Sizes of water-soluble luminescent quantum dots measured by fluorescence correlation spectroscopy
International Nuclear Information System (INIS)
Zhang Pudun; Li Liang; Dong Chaoqing; Qian Huifeng; Ren Jicun
2005-01-01
In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the size of water-soluble quantum dots (QDs). The measurements were performed on a home-built FCS system based on the Stokes-Einstein equation. The obtained results showed that for bare CdTe QDs the sizes from FCS were larger than the ones from transmission electron microscopy (TEM). The brightness of QDs was also evaluated using FCS technique. It was found that the stability of the surface chemistry of QDs would be significantly improved by capping it with hard-core shell. Our data demonstrated that FCS is a simple, fast, and effective method for characterizing the fluorescent quantum dots, and is especially suitable for determining the fluorescent nanoparticles less than 10 nm in water solution
Energy Technology Data Exchange (ETDEWEB)
Penzkofer, A., E-mail: alfons.penzkofer@physik.uni-regensburg.de [Fakultät für Physik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg (Germany)
2013-03-29
Highlights: ► Procedure for absolute phosphorescence quantum yield measurement is described. ► Experimental setup for absolute luminescence quantum yield standard calibration. ► Tb(acac){sub 3} proposed as phosphorescence quantum yield reference standard. ► Luminescence quantum yield of Tb(acac){sub 3} in cyclohexane measured. ► Luminescence lifetime of Tb(acac){sub 3} in cyclohexane measured. - Abstract: Phosphorescence quantum yield measurements of fluorescent and phosphorescent samples require the use of time-gated fluorimeters in order to discriminate against the fluorescence contribution. As reference standard a non-fluorescent luminescent compound is needed for absolute phosphorescence quantum yield determination. For this purpose the luminescence behavior of the rare earth chelate terbium(III)-acetylacetonate (Tb(acac){sub 3}) was studied (determination of luminescence quantum yield and luminescence lifetime). The luminescence quantum yield of Tb(acac){sub 3} was determined by using an external light source and operating the fluorimeter in chemo/bioluminescence mode with a fluorescent dye (rhodamine 6G in methanol) as reference standard. A procedure is developed for absolute luminescence (phosphorescence) quantum yield determination of samples under investigation with a time-gated fluorimeter using a non-fluorescent luminescent compound of known luminescence quantum yield and luminescence lifetime.
Reflection measurements for luminescent powders
Kroon, R. E.
2018-04-01
Luminescent materials are useful in applications varying from lighting and display technologies to document security features and medical research, amongst many others. Measurement of the excitation range is an important consideration, and absorption bands are often determined from a decrease in the measured diffuse reflectance of the material using a ultraviolet-visible (UV-vis) spectrophotometer with an integrating sphere. Such a system may provide questionable results when used to measure the reflectance of a luminescence material, which is demonstrated for a Tb doped silica phosphor, because the system cannot differentiate between the reflected light and luminescence. It is shown that more reliable results are achieved for this phosphor by measuring the reflectance using a synchronous zero-offset scan in a fluorescence spectrometer equipped with an integrating sphere. This method is therefore recommended instead of traditional reflectance measurements using a UV-vis spectrophotometer for luminescent powders.
Anti-Stokes Luminescence in High Quality Quantum Wells
Vinattieri, A.; Bogani, F.; Miotto, A.; Ceccherini, S.
1997-11-01
We present a detailed investigation of the anti-Stokes (AS) luminescence which originates from exciton recombination when below gap excitation is used, in a set of high quality quantum well structures. We observe strong excitonic resonances in the AS signal as measured from photoluminescence and photoluminescence excitation spectra. We demonstrate that neither the electromagnetic coupling between the wells nor the morphological disorder can explain this up-conversion effect. Time-resolved luminescence data after ps excitation and fs correlation spectroscopy results provide clear evidence of the occurrence of a two-step absorption which is assisted by the exciton population resonantly excited by the first photon.
Freestanding silicon quantum dots: origin of red and blue luminescence.
Gupta, Anoop; Wiggers, Hartmut
2011-02-04
In this paper, we studied the behavior of silicon quantum dots (Si-QDs) after etching and surface oxidation by means of photoluminescence (PL) measurements, Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance spectroscopy (EPR). We observed that etching of red luminescing Si-QDs with HF acid drastically reduces the concentration of defects and significantly enhances their PL intensity together with a small shift in the emission spectrum. Additionally, we observed the emergence of blue luminescence from Si-QDs during the re-oxidation of freshly etched particles. Our results indicate that the red emission is related to the quantum confinement effect, while the blue emission from Si-QDs is related to defect states at the newly formed silicon oxide surface.
Busch, Paul; Pellonpää, Juha-Pekka; Ylinen, Kari
2016-01-01
This is a book about the Hilbert space formulation of quantum mechanics and its measurement theory. It contains a synopsis of what became of the Mathematical Foundations of Quantum Mechanics since von Neumann’s classic treatise with this title. Fundamental non-classical features of quantum mechanics—indeterminacy and incompatibility of observables, unavoidable measurement disturbance, entanglement, nonlocality—are explicated and analysed using the tools of operational quantum theory. The book is divided into four parts: 1. Mathematics provides a systematic exposition of the Hilbert space and operator theoretic tools and relevant measure and integration theory leading to the Naimark and Stinespring dilation theorems; 2. Elements develops the basic concepts of quantum mechanics and measurement theory with a focus on the notion of approximate joint measurability; 3. Realisations offers in-depth studies of the fundamental observables of quantum mechanics and some of their measurement implementations; and 4....
Near-Infrared Quantum Cutting Long Persistent Luminescence
Zou, Zehua; Feng, Lin; Cao, Cheng; Zhang, Jiachi; Wang, Yuhua
2016-01-01
By combining the unique features of the quantum cutting luminescence and long persistent luminescence, we design a new concept called ?near-infrared quantum cutting long persistent luminescence (NQPL)?, which makes it possible for us to obtain highly efficient (>100%) near-infrared long persistent luminescence in theory. Guided by the NQPL concept, we fabricate the first NQPL phosphor Ca2Ga2GeO7:Pr3+,Yb3+. It reveals that both the two-step energy transfer of model (I) and the one-step energy ...
Influence of excitonic effects on luminescence quantum yield in silicon
Energy Technology Data Exchange (ETDEWEB)
Sachenko, A.V.; Kostylyov, V.P.; Vlasiuk, V.M. [V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41 prospect Nauky, 03028 Kyiv (Ukraine); Sokolovskyi, I.O., E-mail: isokolovskyi@mun.ca [V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41 prospect Nauky, 03028 Kyiv (Ukraine); Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John' s, NL, A1B 3X7 Canada (Canada); Evstigneev, M. [Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John' s, NL, A1B 3X7 Canada (Canada)
2017-03-15
Nonradiative exciton lifetime in silicon is determined by comparison of the experimental and theoretical curves of bulk minority charge carriers lifetime on doping and excitation levels. This value is used to analyze the influence of excitonic effects on internal luminescence quantum yield at room temperature, taking into account both nonradiative and radiative exciton lifetimes. A range of Shockley-Hall-Reed lifetimes is found, where excitonic effects lead to an increase of internal luminescence quantum yield.
Excitonic effects in the luminescence of quantum wells
International Nuclear Information System (INIS)
Deveaud, B.; Kappei, L.; Berney, J.; Morier-Genoud, F.; Portella-Oberli, M.T.; Szczytko, J.; Piermarocchi, C.
2005-01-01
We report on the origin of the excitonic luminescence in quantum wells. This study is carried out by time-resolved photoluminescence experiments performed on a very high-quality InGaAs quantum well sample in which the photoluminescence contributions at the energy of the exciton and at the band edge can be clearly separated and traced over a broad range of times and densities. This allows us to compare the two conflicting theoretical approaches to the question of the origin of the excitonic luminescence in quantum wells: the model of the exciton population and the model of the Coulomb correlated plasma. We measure the exciton formation time and we show the fast exciton formation and its dependence with carrier density. We are also able to give the boundaries of the Mott transition in our system, and to show the absence of observable renormalization of the gap below the onset of this transition. We detail the characteristics of the trion formation and evidence the possible formation of both positive and negative trions in the absence of any resident free carrier populations
Energy Technology Data Exchange (ETDEWEB)
Prakash, John; Mishra, Ashok Kumar [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India)
2016-01-15
It is possible to measure luminescence quantum yield in a facile way, by designing an optical spectrometer capable of obtaining electronic absorption as well as luminescence spectra, with a setup that uses the same light source and detector for both the spectral measurements. Employment of a single light source and single detector enables use of the same correction factor profile for spectral corrections. A suitable instrumental scaling factor is used for adjusting spectral losses.
Yuan, Jipei; Guo, Weiwei; Yang, Xiurong; Wang, Erkang
2009-01-01
A sensing system based on the photoinduced electron transfer of quantum dots (QDs) was designed to measure the interaction of anticancer drug and DNA, taking mitoxantrone (MTX) as a model drug. MTX adsorbed on the surface of QDs can quench the photoluminescence (PL) of QDs through the photoinduced electron-transfer process; and then the addition of DNA will bring the restoration of QDs PL intensity, as DNA can bind with MTX and remove it from QDs. Sensitive detection of MTX with the detection limit of 10 nmol L(-1) and a linear detection range from 10 nmol L(-1) to 4.5 micromol L(-1) was achieved. The dependence of PL intensity on DNA amount was successfully utilized to investigate the interactions between MTX and DNA. Both the binding constants and the sizes of binding site of MTX-DNA interactions were calculated based on the equations deduced for the PL recovery process. The binding constant obtained in our experiment was generally consistent with previous reports. The sensitive and speedy detection of MTX as well as the avoidance of modification or immobilization process made this system suitable and promising in the drug-DNA interaction studies.
International Nuclear Information System (INIS)
Magaryan, K.A.; Mikhailov, M.A.; Karimullin, K.R.; Knyazev, M.V.; Eremchev, I.Y.; Naumov, A.V.; Vasilieva, I.A.; Klimusheva, G.V.
2016-01-01
The paper is devoted to investigation of luminescence properties of new quantum dot (QD)-doped materials. We studied CdSe QDs (1.8 nm and 2.3 nm) grown inside of a liquid crystalline cadmium alcanoate matrix. Temperature dependence of parameters of fluorescence spectra obtained in a wide temperature range using epi-luminescence microscopy technique was analyzed. Spatially-resolved luminescence images were measured for the areas of the samples of 150×150 µm 2 . Strong correlation between fluorescence spectra and sample structure was observed. - Highlights: • Glassy matrix with CdSe quantum dots inside fabricated in liquid crystalline mesophase. • Study of luminescence properties in a wide range of low temperatures. • Strong dependence of the luminescence spectra on spatial inhomogeneities. • Spatially-resolved luminescence imaging of quantum dots in liquid crystalline matrix.
Energy Technology Data Exchange (ETDEWEB)
Magaryan, K.A., E-mail: xmagaros@gmail.com [Moscow State Pedagogical University, 29 Malaya Pirogovskaya Str., Moscow 119992 (Russian Federation); Mikhailov, M.A. [Moscow State Pedagogical University, 29 Malaya Pirogovskaya Str., Moscow 119992 (Russian Federation); Karimullin, K.R. [Moscow State Pedagogical University, 29 Malaya Pirogovskaya Str., Moscow 119992 (Russian Federation); Institute for Spectroscopy of RAS, 5 Fizicheskaya Str., Troitsk, Moscow 142190 (Russian Federation); E.K. Zavoyski Kazan Physical-Technical Institute of RAS, 10/7 Sibirski trakt Str., Kazan 420029 (Russian Federation); Knyazev, M.V.; Eremchev, I.Y. [Institute for Spectroscopy of RAS, 5 Fizicheskaya Str., Troitsk, Moscow 142190 (Russian Federation); Naumov, A.V. [Moscow State Pedagogical University, 29 Malaya Pirogovskaya Str., Moscow 119992 (Russian Federation); Institute for Spectroscopy of RAS, 5 Fizicheskaya Str., Troitsk, Moscow 142190 (Russian Federation); Vasilieva, I.A. [Moscow State Pedagogical University, 29 Malaya Pirogovskaya Str., Moscow 119992 (Russian Federation); Klimusheva, G.V. [Institute of Physics, NAS of Ukraine, 46 Prospect Nauki, Kiev 03028 (Ukraine)
2016-01-15
The paper is devoted to investigation of luminescence properties of new quantum dot (QD)-doped materials. We studied CdSe QDs (1.8 nm and 2.3 nm) grown inside of a liquid crystalline cadmium alcanoate matrix. Temperature dependence of parameters of fluorescence spectra obtained in a wide temperature range using epi-luminescence microscopy technique was analyzed. Spatially-resolved luminescence images were measured for the areas of the samples of 150×150 µm{sup 2}. Strong correlation between fluorescence spectra and sample structure was observed. - Highlights: • Glassy matrix with CdSe quantum dots inside fabricated in liquid crystalline mesophase. • Study of luminescence properties in a wide range of low temperatures. • Strong dependence of the luminescence spectra on spatial inhomogeneities. • Spatially-resolved luminescence imaging of quantum dots in liquid crystalline matrix.
Time-resolved measurements of luminescence
Energy Technology Data Exchange (ETDEWEB)
Collier, Bradley B. [Department of Biomedical Engineering, 408 Mechanical Engineering Office Building, Spence Street, Texas A and M University, College Station, TX 77843 (United States); McShane, Michael J., E-mail: mcshane@tamu.edu [Department of Biomedical Engineering, 408 Mechanical Engineering Office Building, Spence Street, Texas A and M University, College Station, TX 77843 (United States); Materials Science and Engineering Program, 408 Mechanical Engineering Office Building, Spence Street, Texas A and M University, College Station, TX 77843 (United States)
2013-12-15
Luminescence sensing and imaging has become more widespread in recent years in a variety of industries including the biomedical and environmental fields. Measurements of luminescence lifetime hold inherent advantages over intensity-based response measurements, and advances in both technology and methods have enabled their use in a broader spectrum of applications including real-time medical diagnostics. This review will focus on recent advances in analytical methods, particularly calculation techniques, including time- and frequency-domain lifetime approaches as well as other time-resolved measurements of luminescence. -- Highlights: • Developments in technology have led to widespread use of luminescence lifetime. • Growing interest for sensing and imaging applications. • Recent advances in approaches to lifetime calculations are reviewed. • Advantages and disadvantages of various methods are weighed. • Other methods for measurement of luminescence lifetime also described.
Time-resolved measurements of luminescence
International Nuclear Information System (INIS)
Collier, Bradley B.; McShane, Michael J.
2013-01-01
Luminescence sensing and imaging has become more widespread in recent years in a variety of industries including the biomedical and environmental fields. Measurements of luminescence lifetime hold inherent advantages over intensity-based response measurements, and advances in both technology and methods have enabled their use in a broader spectrum of applications including real-time medical diagnostics. This review will focus on recent advances in analytical methods, particularly calculation techniques, including time- and frequency-domain lifetime approaches as well as other time-resolved measurements of luminescence. -- Highlights: • Developments in technology have led to widespread use of luminescence lifetime. • Growing interest for sensing and imaging applications. • Recent advances in approaches to lifetime calculations are reviewed. • Advantages and disadvantages of various methods are weighed. • Other methods for measurement of luminescence lifetime also described
Application of Quantum Dot nanocrystal in Luminescent solar concentrators
Bakhoda, Shokoufeh; Khalaji Assadi, Morteza; Ahmadi Kandjani, Sohrab; Kayiem, Hussain H. Al; Hussain Bhat, Aamir
2018-03-01
The basic design of luminescent solar concentrator is a transparent plate doped with an appropriate luminescent material (organic dyes, quantum dots), which is able to absorb sunlight (direct and diffuse), and then guides photons produced by photoluminescence to its narrow edges where they are converted by photovoltaic cells. Unfortunately, LSCs have suffered from numerous efficiency losses. Therefore, new luminescent species and novel approaches are needed for its practical application. This paper deals with investigation of nonhazardous, environmental friendly luminescent species include CuInS2/ZnS core/shell QDs. The CuInS2/ZnS QDs possess advantages of Stocks shift as large as more than 130 nm and high photoluminescence quantum yield of 80%. The paper presents the effect of large stock shift CuInS2/ZnS QDs on reducing the reabsorption losses in LSC by using experimental investigation. The LSC sheets were fabricated by dispersing CuInS2/ZnS QDs particles in a polymethylmethacrylate waveguide. A series of LSCs (dimension 4.0 cm × 3.0 cm × 0.3cm) with different CuInS2/ZnS QDs particles concentration (0.015 and 0.03 wt.%) were fabricated and their optical properties (absorptions/emissions) were characterized. The results show that the CuInS2/ZnS QDs-LSC provides a promising way for the reduction of reabsorption losses in LSCs.
DEFF Research Database (Denmark)
Zhang, Aihua; Peng, Mingzeng; Willatzen, Morten
2017-01-01
The mechanism of strain-dependent luminescence is important for the rational design of pressure-sensing devices. The interband momentum-matrix element is the key quantity for understanding luminescent phenomena. We analytically solved an infinite quantum well (IQW) model with strain, in the frame......The mechanism of strain-dependent luminescence is important for the rational design of pressure-sensing devices. The interband momentum-matrix element is the key quantity for understanding luminescent phenomena. We analytically solved an infinite quantum well (IQW) model with strain......, in the framework of the 6 × 6 k·p Hamiltonian for the valence states, to directly assess the interplay between the spin-orbit coupling and the strain-induced deformation potential for the interband momentum-matrix element. We numerically addressed problems of both the infinite and IQWs with piezoelectric fields...... to elucidate the effects of the piezoelectric potential and the deformation potential on the strain-dependent luminescence. The experimentally measured photoluminescence variatio½n as a function of pressure can be qualitatively explained by the theoretical results....
What quantum measurements measure
Griffiths, Robert B.
2017-09-01
A solution to the second measurement problem, determining what prior microscopic properties can be inferred from measurement outcomes ("pointer positions"), is worked out for projective and generalized (POVM) measurements, using consistent histories. The result supports the idea that equipment properly designed and calibrated reveals the properties it was designed to measure. Applications include Einstein's hemisphere and Wheeler's delayed choice paradoxes, and a method for analyzing weak measurements without recourse to weak values. Quantum measurements are noncontextual in the original sense employed by Bell and Mermin: if [A ,B ]=[A ,C ]=0 ,[B ,C ]≠0 , the outcome of an A measurement does not depend on whether it is measured with B or with C . An application to Bohm's model of the Einstein-Podolsky-Rosen situation suggests that a faulty understanding of quantum measurements is at the root of this paradox.
Ligand-assisted fabrication, structure, and luminescence properties of Fe:ZnSe quantum dots
International Nuclear Information System (INIS)
Xie, Ruishi; Zhang, Xingquan; Liu, Haifeng
2014-01-01
Highlights: • A green route is developed for synthesis of water-soluble and fluorescent Fe:ZnSe quantum dots. • Tunable luminescence intensity can be realized with different ligand-to-Zn molar ratios. • The obtained quantum dots are in the so-called “quantum confinement regime”. -- Abstract: Here, we report a synthetic route for highly emissive Fe:ZnSe quantum dots in aqueous media using the mercaptoacetic acid ligand as stabilizing agent. The structural, morphological, componential, and optical properties of the resulting quantum dots were explored by the X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, photoluminescence and UV–visible absorption spectroscopies. The average crystallite size was calculated to be about ca., 4.0 nm using the Scherrer equation, which correlates well with the value obtained from the transmission electron microscopy analysis. The obtained water-soluble Fe:ZnSe quantum dots in the so-called “quantum confinement regime” are spherical shaped, possess the cubic sphalerite crystal structure, and exhibit tunable luminescence properties. The presence of mercaptoacetic acid on the surface of Fe:ZnSe quantum dots was confirmed by the Fourier transform infrared spectroscopy measurements. As the ligand/Zn molar ratio increases from 1.3 to 2.8, there is little shift in the absorption peak of the Fe:ZnSe sample, indicating that the particle size of the obtained quantum dots is not changed during the synthetic process. The photoluminescence quantum yield of the as-prepared water-soluble Fe:ZnSe quantum dots can be up to 39%. The molar ratio of ligand-to-Zn plays a crucial role in determining the final luminescence properties of the resulting quantum dots, and the maximum PL intensity appears as the ligand-to-Zn molar ratio is 2.2. In addition, the underlying mechanism for
Ligand-assisted fabrication, structure, and luminescence properties of Fe:ZnSe quantum dots
Energy Technology Data Exchange (ETDEWEB)
Xie, Ruishi, E-mail: rxie@foxmail.com; Zhang, Xingquan; Liu, Haifeng
2014-03-15
Highlights: • A green route is developed for synthesis of water-soluble and fluorescent Fe:ZnSe quantum dots. • Tunable luminescence intensity can be realized with different ligand-to-Zn molar ratios. • The obtained quantum dots are in the so-called “quantum confinement regime”. -- Abstract: Here, we report a synthetic route for highly emissive Fe:ZnSe quantum dots in aqueous media using the mercaptoacetic acid ligand as stabilizing agent. The structural, morphological, componential, and optical properties of the resulting quantum dots were explored by the X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, photoluminescence and UV–visible absorption spectroscopies. The average crystallite size was calculated to be about ca., 4.0 nm using the Scherrer equation, which correlates well with the value obtained from the transmission electron microscopy analysis. The obtained water-soluble Fe:ZnSe quantum dots in the so-called “quantum confinement regime” are spherical shaped, possess the cubic sphalerite crystal structure, and exhibit tunable luminescence properties. The presence of mercaptoacetic acid on the surface of Fe:ZnSe quantum dots was confirmed by the Fourier transform infrared spectroscopy measurements. As the ligand/Zn molar ratio increases from 1.3 to 2.8, there is little shift in the absorption peak of the Fe:ZnSe sample, indicating that the particle size of the obtained quantum dots is not changed during the synthetic process. The photoluminescence quantum yield of the as-prepared water-soluble Fe:ZnSe quantum dots can be up to 39%. The molar ratio of ligand-to-Zn plays a crucial role in determining the final luminescence properties of the resulting quantum dots, and the maximum PL intensity appears as the ligand-to-Zn molar ratio is 2.2. In addition, the underlying mechanism for
Efficient Luminescence from Perovskite Quantum Dot Solids
Kim, Younghoon; Yassitepe, Emre; Voznyy, Oleksandr; Comin, Riccardo; Walters, Grant; Gong, Xiwen; Kanjanaboos, Pongsakorn; Nogueira, Ana F.; Sargent, Edward H.
2015-01-01
© 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.
Efficient Luminescence from Perovskite Quantum Dot Solids
Kim, Younghoon
2015-11-18
© 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.
Quantum measurement in quantum optics
International Nuclear Information System (INIS)
Kimble, H.J.
1993-01-01
Recent progress in the generation and application of manifestly quantum or nonclassical states of the electromagnetic field is reviewed with emphasis on the research of the Quantum Optics Group at Caltech. In particular, the possibilities for spectroscopy with non-classical light are discussed both in terms of improved quantitative measurement capabilities and for the fundamental alteration of atomic radiative processes. Quantum correlations for spatially extended systems are investigated in a variety of experiments which utilize nondegenerate parametric down conversion. Finally, the prospects for measurement of the position of a free mass with precision beyond the standard quantum limit are briefly considered. (author). 38 refs., 1 fig
Luminescence and ultrafast phenomena in InGaN multiple quantum wells
International Nuclear Information System (INIS)
Viswanath, Annamraju Kasi; Lee, J.I.; Kim, S.T.; Yang, G.M.; Lee, H.J.; Kim, Dongho
2007-01-01
High quality In 0.13 Ga 0.87 N/GaN multiple quantum wells (MQWs) on (0001) sapphire substrate were fabricated by MOCVD method. The quantum well thickness is as thin as 10 A, and the barrier thickness is 50 A. We have investigated these ultrathin MQWs by continuous wave (cw) and time-resolved spectroscopy in the picosecond time scales in a wide temperature range from 10 to 290 K. In the luminescence spectrum at 10 K, we observed a broad peak at 3.134 eV which was attributed to the quantum wells emission of InGaN. The full width at half maximum of this peak was 129 meV at 10 K and the broadening at low temperatures which was mostly inhomogeneous was thought to be due to compositional fluctuations and interfacial disorder in the alloy. We also observed an intense and narrow peak at 3.471 eV due to the GaN barrier. The temperature dependence of the luminescence was studied and the peak positions and the intensities of the different peaks were obtained. The activation energy of the InGaN quantum well emission peak was estimated as 69 meV. From the measurements of luminescence intensities and lifetimes at various temperatures, radiative and non-radiative recombination lifetimes were deduced. The results were explained by considering only the localization of the excitons due to potential fluctuations
New luminescence measurement facilities in retrospective dosimetry
DEFF Research Database (Denmark)
Lapp, Torben; Jain, Mayank; Thomsen, Kristina Jørkov
2012-01-01
), this facility has been used to measure natural doses in feldspar using the decaying NIR RL signal.Secondly, we present a method for mapping radiation field of the built-in 90Sr/90Y β-source and estimating grain-location specific dose-rates. This is important for the accuracy of single grain results, when......This paper gives a review of recent developments in luminescence measurement facilities on the Risø TL/OSL reader including radio-luminescence (RL), exo-electron and violet stimulation attachments, and a method for characterising and if necessary correcting for beta irradiation source non...... radiation field is spatially non-uniform across the sample area. We document the effect of this correction method and further investigate on the effect of lifting the source to achieve a better dose-rate uniformity.Finally we summarise two recently-developed novel facilities to help investigate (i) the time...
Biosynthesis of luminescent quantum dots in an earthworm
Stürzenbaum, S. R.; Höckner, M.; Panneerselvam, A.; Levitt, J.; Bouillard, J.-S.; Taniguchi, S.; Dailey, L.-A.; Khanbeigi, R. Ahmad; Rosca, E. V.; Thanou, M.; Suhling, K.; Zayats, A. V.; Green, M.
2013-01-01
The synthesis of designer solid-state materials by living organisms is an emerging field in bio-nanotechnology. Key examples include the use of engineered viruses as templates for cobalt oxide (Co3O4) particles, superparamagnetic cobalt-platinum alloy nanowires and gold-cobalt oxide nanowires for photovoltaic and battery-related applications. Here, we show that the earthworm's metal detoxification pathway can be exploited to produce luminescent, water-soluble semiconductor cadmium telluride (CdTe) quantum dots that emit in the green region of the visible spectrum when excited in the ultraviolet region. Standard wild-type Lumbricus rubellus earthworms were exposed to soil spiked with CdCl2 and Na2TeO3 salts for 11 days. Luminescent quantum dots were isolated from chloragogenous tissues surrounding the gut of the worm, and were successfully used in live-cell imaging. The addition of polyethylene glycol on the surface of the quantum dots allowed for non-targeted, fluid-phase uptake by macrophage cells.
Doping the dots: doped quantum dots for luminescent solar concentrators
Eilers, J.J.
2015-01-01
In this thesis, synthesis methods for luminescent organically capped colloidal ZnSe QDs of different sizes, ranging from 4.0 to 7.5 nm are reported. These QDs are analyzed using TEM, absorption spectroscopy, photoluminescence measurements and temperature dependent photoluminescence decay
Luminescence model with quantum impact parameter for low energies
International Nuclear Information System (INIS)
Cruz G, H.S.; Michaelian, K.; Galindo U, S.; Martinez D, A.; Belmont M, E.
2000-01-01
The analytical model of induced light production in scintillator materials by energetic ions proposed by Michaelian and Menchaca (M-M) adjusts very well the luminescence substance data in a wide energy interval of the incident ions (10-100 MeV). However at low energies, that is, under to 10 MeV, the experimental deviations of the predictions of M-M model, show that the causes may be certain physical effects, all they important at low energies, which were not considered. We have modified lightly the M-M model using the basic fact that the Quantum mechanics gives to a different limit for the quantum impact parameter instead of the classic approximation. (Author)
Kohl, M.; Heitmann, D.; Grambow, P.; Ploog, K.
1988-06-01
Periodic multiple-quantum-well wires have been prepared by etching five-layer quantum-well structures through a holographically prepared mask. The periodicity was 380 nm, the lateral confinement 180 nm, and the quantum-well width 13, nm. The luminescence from these microstructured systems in the frequency regime of the one-electron-one-heavy-hole transition was strongly polarized with the electric field perpendicular to the periodic structure. This effect was caused by the resonantly enhanced emission of quantum-well-exciton (QWE) polaritons. Excitation of QWE polaritons was also observed in reflection measurements on the microstructured samples.
Energy Technology Data Exchange (ETDEWEB)
Zharkova, Irina S.; Markina, Natalia E. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Markin, Alexey V., E-mail: av_markin@mail.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Drozd, Daniil D.; Speranskaya, Elena S. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Goryacheva, Irina Yu. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Saint-Petersburg State University, Universitetskii pr. 26, 198504 Petrodvorets, Saint-Petersburg (Russian Federation)
2016-08-15
The application of external electric field for verification of quantum dots (QDs) stability in aqueous medium was proposed. Hydrophilic CdSe core-shell nanocrystals were synthesized and used with three polymer-based organic stabilizers, two of which contain PEG chains. An increasing of the stability under applied electric field (EF) was shown for stabilizer containing higher amount of PEG chains and terminal amino-groups: introduction of additional PEG chains allowed reducing degradation of luminescence intensity for about 60%. The changes of QDs solutions after EF treatment were examined by dynamic light scattering measurements, luminescence and absorbance spectroscopy, and conductivity measurements and explained by decreasing of quantum yield of the samples due to degradation of stabilizer coating. - Highlights: • Hydrophilic QDs with three types of stabilizer coatings were prepared and treated by electric field in water environment. • Permanent QDs luminescence quenching in aqueous medium under low electric field strength was observed. • Luminescence stability to EF treatment increases by stabilizer with higher PEG content. • Redox mechanism of luminescence quenching was proved via conductivity, DLS, and UV-visible absorbance measurements.
Measurement in quantum physics
International Nuclear Information System (INIS)
Danos, M.; Kieu, T.D.; Columbia Univ., New York, NY
1997-01-01
The conceptual problems in quantum mechanics - including the collapse of the wave functions, the particle-wave duality, the meaning of measurement-arise from the need to ascribe particle character to the wave function, which describes only the wave aspects. It is demonstrated that all these problems can be resolved when working instead with quantum fields, which have both wave and particle character. The predictions of quantum physics, including Bell's inequalities, remain unchanged from the standard treatments of quantum mechanics. 16 refs
Preparation of carbon quantum dots based high photostability luminescent membranes.
Zhao, Jinxing; Liu, Cui; Li, Yunchuan; Liang, Jiyuan; Liu, Jiyan; Qian, Tonghui; Ding, Jianjun; Cao, Yuan-Cheng
2017-06-01
Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -C = C-vibration at 1101 cm -1 disappeared but there was strong vibration at1687cm -1 which was contributed from the-C = O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications. Copyright © 2016 John Wiley & Sons, Ltd.
Luminescence of CdSe/ZnS quantum dots infiltrated into an opal matrix
International Nuclear Information System (INIS)
Gruzintsev, A. N.; Emelchenko, G. A.; Masalov, V. M.; Yakimov, E. E.; Barthou, C.; Maitre, A.
2009-01-01
The effect of the photonic band gap in the photonic crystal, the synthesized SiO 2 opal with embedded CdSe/ZnS quantum dots, on its luminescence in the visible spectral region is studied. It is shown that the position of the photonic band gap in the luminescence and reflectance spectra for the infiltrated opal depends on the diameter of the constituent nanospheres and on the angle of recording the signal. The optimal conditions for embedding the CdSe/ZnS quantum dots from the solution into the opal matrix are determined. It is found that, for the opal-CdSe/ZnS nanocomposites, the emission intensity decreases and the luminescence decay time increases in the spatial directions, in which the spectral positions of the photonic band gap and the luminescence peak of the quantum dots coincide.
Design of Biotin-Functionalized Luminescent Quantum Dots
Directory of Open Access Journals (Sweden)
Kimihiro Susumu
2007-01-01
Full Text Available We report the design and synthesis of a tetraethylene glycol- (TEG- based bidentate ligand functionalized with dihydrolipoic acid (DHLA and biotin (DHLA—TEG—biotin to promote biocompatibility of luminescent quantum dots (QD's. This new ligand readily binds to CdSe—ZnS core-shell QDs via surface ligand exchange. QDs capped with a mixture of DHLA and DHLA—TEG—biotin or polyethylene glycol- (PEG- (molecular weight average ∼600 modified DHLA (DHLA—PEG600 and DHLA—TEG—biotin are easily dispersed in aqueous buffer solutions. In particular, homogeneous buffer solutions of QDs capped with a mixture of DHLA—PEG600 and DHLA—TEG—biotin that are stable over broad pH range have been prepared. QDs coated with mixtures of DHLA/DHLA—TEG—biotin and with DHLA—PEG600/DHLA—TEG—biotin were tested in surface binding assays and the results indicate that biotin groups on the QD surface interact specifically with NeutrAvidin-functionalized microtiter well plates.
Decoherence and quantum measurements
Namiki, Mikio; Pascazio, Saverio
1997-01-01
The quantum measurement problem is one of the most fascinating and challenging topics in physics both theoretically and experimentally. It involves deep questions and the use of very sophisticated and elegant techniques. After analyzing the fundamental principles of quantum mechanics and of the Copenhagen interpretation, this book reviews the most important approaches to the measurement problem and rigorously reformulates the "collapse of the wave function" by measurement, as a dephasing process quantitatively characterized by an order parameter (called the decoherence parameter), according to
Lin, Liangxu; Zhang, Shaowei
2012-10-21
We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.
Weak Measurement and Quantum Correlation
Indian Academy of Sciences (India)
Arun Kumar Pati
Entanglement: Two quantum systems can be in a strongly correlated state even if .... These are resources which can be used to design quantum computer, quantum ...... Weak measurements have found numerous applications starting from the ...
Direct determination of graphene quantum dots based on terbium-sensitized luminescence
Llorent-Martínez, Eulogio J.; Molina-García, Lucía; Durán, Gema M.; Ruiz-Medina, Antonio; Ríos, Ángel
2018-06-01
Graphene quantum dots (GQD) were determined in water samples using terbium-sensitized luminescence (TSL). Terbium ions complex with GQD due to the carboxylic groups that are usually present in these nanomaterials, increasing the luminescence signal of terbium. In Tb(III)-GQD complexes, GQD absorb energy at their characteristic excitation wavelength and transfer it to terbium ion, which emits at its particular emission wavelength. The analytical signal, measured at λexc = 257 nm and λem = 545 nm, increases proportionally to GQD concentration between 50 and 500 μg L-1. Under optimum conditions, the proposed method presents a detection limit of 15 μg L-1 and is selective to GQD in the presence of other nanomaterials of similar size. As GQD are highly water-soluble, they are potential contaminants in environmental or drinking waters water samples, and hence the method was applied to the analysis of different drinking waters which were the target samples for the application of the developed method.
Quantum learning algorithms for quantum measurements
Energy Technology Data Exchange (ETDEWEB)
Bisio, Alessandro, E-mail: alessandro.bisio@unipv.it [QUIT Group, Dipartimento di Fisica ' A. Volta' and INFN, via Bassi 6, 27100 Pavia (Italy); D' Ariano, Giacomo Mauro, E-mail: dariano@unipv.it [QUIT Group, Dipartimento di Fisica ' A. Volta' and INFN, via Bassi 6, 27100 Pavia (Italy); Perinotti, Paolo, E-mail: paolo.perinotti@unipv.it [QUIT Group, Dipartimento di Fisica ' A. Volta' and INFN, via Bassi 6, 27100 Pavia (Italy); Sedlak, Michal, E-mail: michal.sedlak@unipv.it [QUIT Group, Dipartimento di Fisica ' A. Volta' and INFN, via Bassi 6, 27100 Pavia (Italy); Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia)
2011-09-12
We study quantum learning algorithms for quantum measurements. The optimal learning algorithm is derived for arbitrary von Neumann measurements in the case of training with one or two examples. The analysis of the case of three examples reveals that, differently from the learning of unitary gates, the optimal algorithm for learning of quantum measurements cannot be parallelized, and requires quantum memories for the storage of information. -- Highlights: → Optimal learning algorithm for von Neumann measurements. → From 2 copies to 1 copy: the optimal strategy is parallel. → From 3 copies to 1 copy: the optimal strategy must be non-parallel.
Quantum learning algorithms for quantum measurements
International Nuclear Information System (INIS)
Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo; Sedlak, Michal
2011-01-01
We study quantum learning algorithms for quantum measurements. The optimal learning algorithm is derived for arbitrary von Neumann measurements in the case of training with one or two examples. The analysis of the case of three examples reveals that, differently from the learning of unitary gates, the optimal algorithm for learning of quantum measurements cannot be parallelized, and requires quantum memories for the storage of information. -- Highlights: → Optimal learning algorithm for von Neumann measurements. → From 2 copies to 1 copy: the optimal strategy is parallel. → From 3 copies to 1 copy: the optimal strategy must be non-parallel.
Quantum discord with weak measurements
International Nuclear Information System (INIS)
Singh, Uttam; Pati, Arun Kumar
2014-01-01
Weak measurements cause small change to quantum states, thereby opening up the possibility of new ways of manipulating and controlling quantum systems. We ask, can weak measurements reveal more quantum correlation in a composite quantum state? We prove that the weak measurement induced quantum discord, called as the “super quantum discord”, is always larger than the quantum discord captured by the strong measurement. Moreover, we prove the monotonicity of the super quantum discord as a function of the measurement strength and in the limit of strong projective measurement the super quantum discord becomes the normal quantum discord. We find that unlike the normal discord, for pure entangled states, the super quantum discord can exceed the quantum entanglement. Our results provide new insights on the nature of quantum correlation and suggest that the notion of quantum correlation is not only observer dependent but also depends on how weakly one perturbs the composite system. We illustrate the key results for pure as well as mixed entangled states. -- Highlights: •Introduced the role of weak measurements in quantifying quantum correlation. •We have introduced the notion of the super quantum discord (SQD). •For pure entangled state, we show that the SQD exceeds the entanglement entropy. •This shows that quantum correlation depends not only on observer but also on measurement strength
Quantum measure and integration theory
International Nuclear Information System (INIS)
Gudder, Stan
2009-01-01
This article begins with a review of quantum measure spaces. Quantum forms and indefinite inner-product spaces are then discussed. The main part of the paper introduces a quantum integral and derives some of its properties. The quantum integral's form for simple functions is characterized and it is shown that the quantum integral generalizes the Lebesgue integral. A bounded, monotone convergence theorem for quantum integrals is obtained and it is shown that a Radon-Nikodym-type theorem does not hold for quantum measures. As an example, a quantum-Lebesgue integral on the real line is considered.
Quantum gravity and quantum nondemolition measurements
International Nuclear Information System (INIS)
Borzeszkowski, H.H. von; Treder, H.J.
1984-01-01
It is shown that in Quantum Gravity, and more general: in Grand Unified Theory incorporating General Relativity on a basic level, there arise necessarily absolute limitations on measurement which one cannot evade by any 'quantum nondemolition measurements'. This fact is demonstrated not to oppose the existence of certain approximations to the full theory where these limitations do not arise. (author)
The quantum measurement problem.
Leggett, A J
2005-02-11
Despite the spectacular success of quantum mechanics (QM) over the last 80 years in explaining phenomena observed at the atomic and subatomic level, the conceptual status of the theory is still a topic of lively controversy. Most of the discussion centers around two famous paradoxes (or, as some would have it, pseudoparadoxes) associated, respectively, with the names of Einstein, Podolsky, and Rosen (EPR) and with Schrodinger's cat. In this Viewpoint, I will concentrate on the paradox of Schrodinger's cat or, as it is often known (to my mind somewhat misleadingly), the quantum measurement paradox.
Blue and green luminescence of reduced graphene oxide quantum dots
Czech Academy of Sciences Publication Activity Database
Štengl, Václav; Bakardjieva, Snejana; Henych, Jiří; Lang, Kamil; Kormunda, M.
2013-01-01
Roč. 63, november (2013), s. 537-546 ISSN 0008-6223 Institutional support: RVO:61388980 Keywords : different solvents * graphene oxides * green luminescence * intensive cavitations * N-methyl-2-pyrrolidone Subject RIV: CA - Inorganic Chemistry Impact factor: 6.160, year: 2013
International Nuclear Information System (INIS)
Romero, M.J.; van de Lagemaat, J.
2009-01-01
The electronic coupling between quantum dots (QDs) and surface plasmons (SPs) is investigated by a luminescence spectroscopy based on scanning tunneling microscopy (STM). We show that tunneling luminescence from the dot is excited by coupling with the nonradiative plasmon mode oscillating at the metallic tunneling gap formed during the STM operation. This approach to the SP excitation reveals aspects of the SP-QD coupling not accessible to the more conventional optical excitation of SPs. In the STM, luminescence from the dot is observed when and only when the SP is in resonance with the fundamental transition of the dot. The tunneling luminescence spectrum also suggests that excited SP-QD hybrid states can participate in the excitation of QD luminescence. Not only the SP excitation regulates the QD luminescence but the presence of the dot at the tunneling gap imposes restrictions to the SP that can be excited in the STM, in which the SP cannot exceed the energy of the fundamental transition of the dot. The superior SP-QD coupling observed in the STM is due to the tunneling gap acting as a tunable plasmonic resonator in which the dot is fully immersed.
Pukaki 1-01 : initial luminescence dating and radiometric measurements
International Nuclear Information System (INIS)
Rieser, U.
2001-01-01
Core from Pukaki 1-01 was sampled for luminescence dating and radiometric measurements on 14 March 2001 in the dark room laboratory at Victoria University. Seven samples were taken to get an overview of the crater history, and laboratory work was completed in August 2001. (author). 2 figs., 3 tabs
Quantum ergodicity and a quantum measure algebra
International Nuclear Information System (INIS)
Stechel, E.B.
1985-01-01
A quantum ergodic theory for finite systems (such as isolated molecules) is developed by introducing the concept of a quantum measure algebra. The basic concept in classical ergodic theory is that of a measure space. A measure space is a set M, together with a specified sigma algebra of subsets in M and a measure defined on that algebra. A sigma algebra is closed under the formation of intersections and symmetric differences. A measure is a nonnegative and countably additive set function. For this to be further classified as a dynamical system, a measurable transformation is introduced. A measurable transformation is a mapping from a measure space into a measure space, such that the inverse image of every measurable set is measurable. In conservative dynamical systems, a measurable transformation is measure preserving, which is to say that the inverse image of every measurable set has the same measure as the original set. Once the measure space and the measurable transformation are defined, ergodic theory can be investigated on three levels: describable as analytic, geometric and algebraic. The analytic level studies linear operators induced by a transformation. The geometric level is concerned directly with transformations on a measure space and the algebraic treatments substitute a measure algebra for the measure space and basically equate sets that differ only by sets of measure zero. It is this latter approach that is most directly paralleled here. A measure algebra for a quantum dynamical system is defined within which stochastic concepts in quantum mechanics can be investigated. The quantum measure algebra differs from a normal measure algebra only in that multiplication is noncommutative and addition is nonassociative. Nonetheless, the quantum measure algebra preserves the essence of a normal measure algebra
Suriyaprakash, Jagadeesh; Qiao, Ting Ting
2018-02-01
One can design a robust optical device by engineering the optical band gap of the quantum dots (QDs) owing to their size-tunable quantum confinement effect. To do this, understanding the optical effects of QDs and composite materials is crucial. In this context, various sizes (2.8-4.2 nm) of CdSe QDs-PMMA nanocomposite are fabricated in a two-step process and their absorbance, luminescence and optical constants studied systematically. The ellipsometry spectroscopic analysis exhibits the heterogeneous medium feature of Ψ value and also the measured refractive index (1.51-1.59) values are increased with decreased band gap (2.24-2.10 eV). The observed red shift in the UV-Vis and photoluminescence spectra is indicative of early stage CdSe QD followed by a nucleation process of bigger size QD. In addition, the growth kinetics of the reaction and the band gap of the QDs are evaluated with respect to the time to testify the colloidal QDs formation. The thickness and QD composition of the nanocomposite thin films calculated by effective medium approximation are 100 nm and 8-12%, respectively. Morphology and structural feature transmission electron microscopy study of the fabricated nanocomposite demonstrated that spherical CdSe QDs are well dispersed in PMMA.
Quantum dot-polymer conjugates for stable luminescent displays.
Ghimire, Sushant; Sivadas, Anjaly; Yuyama, Ken-Ichi; Takano, Yuta; Francis, Raju; Biju, Vasudevanpillai
2018-05-23
The broad absorption of light in the UV-Vis-NIR region and the size-based tunable photoluminescence color of semiconductor quantum dots make these tiny crystals one of the most attractive antennae in solar cells and phosphors in electrooptical devices. One of the primary requirements for such real-world applications of quantum dots is their stable and uniform distribution in optically transparent matrices. In this work, we prepare transparent thin films of polymer-quantum dot conjugates, where CdSe/ZnS quantum dots are uniformly distributed at high densities in a chitosan-polystyrene copolymer (CS-g-PS) matrix. Here, quantum dots in an aqueous solution are conjugated to the copolymer by a phase transfer reaction. With the stable conjugation of quantum dots to the copolymer, we prevent undesired phase separation between the two and aggregation of quantum dots. Furthermore, the conjugate allows us to prepare transparent thin films in which quantum dots are uniformly distributed at high densities. The CS-g-PS copolymer helps us in not only preserving the photoluminescence properties of quantum dots in the film but also rendering excellent photostability to quantum dots at the ensemble and single particle levels, making the conjugate a promising material for photoluminescence-based devices.
Enhanced UV luminescence from InAlN quantum well structures using two temperature growth
International Nuclear Information System (INIS)
Zubialevich, Vitaly Z.; Sadler, Thomas C.; Dinh, Duc V.; Alam, Shahab N.; Li, Haoning; Pampili, Pietro; Parbrook, Peter J.
2014-01-01
InAlN/AlGaN multiple quantum wells (MQWs) emitting between 300 and 350 nm have been prepared by metalorganic chemical vapor deposition on planar AlN templates. To obtain strong room temperature luminescence from InAlN QWs a two temperature approach was required. The intensity decayed weakly as the temperature was increased to 300 K, with ratios I PL (300 K)/I PL (T) max up to 70%. This high apparent internal quantum efficiency is attributed to the exceptionally strong carrier localization in this material, which is also manifested by a high Stokes shift (0.52 eV) of the luminescence. Based on these results InAlN is proposed as a robust alternative to AlGaN for ultraviolet emitting devices. - Highlights: • InAlN quantum wells with AlGaN barriers emitting in near UV successfully grown using quasi-2T approach. • 1 nm AlGaN capping of InAlN quantum wells used to avoid In desorption during temperature ramp to barrier growth conditions. • Strong, thermally resilient luminescence obtained as a result of growth optimization. • Promise of InAlN as an alternative active region for UV emitters demonstrated
Cherenkov luminescence measurements with digital silicon photomultipliers: a feasibility study
Energy Technology Data Exchange (ETDEWEB)
Ciarrocchi, Esther; Belcari, Nicola; Guerra, Alberto Del [Department of Physics, University of Pisa, Pisa (Italy); INFN, section of Pisa, Pisa (Italy); Cherry, Simon R. [Department of Biomedical Engineering, University of California, Davis, CA (United States); Lehnert, Adrienne; Hunter, William C. J.; McDougald, Wendy; Miyaoka, Robert S.; Kinahan, Paul E. [Department of Radiology, University of Washington, Seattle, WA (United States)
2015-11-16
A feasibility study was done to assess the capability of digital silicon photomultipliers to measure the Cherenkov luminescence emitted by a β source. Cherenkov luminescence imaging (CLI) is possible with a charge coupled device (CCD) based technology, but a stand-alone technique for quantitative activity measurements based on Cherenkov luminescence has not yet been developed. Silicon photomultipliers (SiPMs) are photon counting devices with a fast impulse response and can potentially be used to quantify β-emitting radiotracer distributions by CLI. In this study, a Philips digital photon counting (PDPC) silicon photomultiplier detector was evaluated for measuring Cherenkov luminescence. The PDPC detector is a matrix of avalanche photodiodes, which were read one at a time in a dark count map (DCM) measurement mode (much like a CCD). This reduces the device active area but allows the information from a single avalanche photodiode to be preserved, which is not possible with analog SiPMs. An algorithm to reject the noisiest photodiodes and to correct the measured count rate for the dark current was developed. The results show that, in DCM mode and at (10–13) °C, the PDPC has a dynamic response to different levels of Cherenkov luminescence emitted by a β source and transmitted through an opaque medium. This suggests the potential for this approach to provide quantitative activity measurements. Interestingly, the potential use of the PDPC in DCM mode for direct imaging of Cherenkov luminescence, as a opposed to a scalar measurement device, was also apparent. We showed that a PDPC tile in DCM mode is able to detect and image a β source through its Cherenkov radiation emission. The detector’s dynamic response to different levels of radiation suggests its potential quantitative capabilities, and the DCM mode allows imaging with a better spatial resolution than the conventional event-triggered mode. Finally, the same acquisition procedure and data processing could
Cherenkov luminescence measurements with digital silicon photomultipliers: a feasibility study
International Nuclear Information System (INIS)
Ciarrocchi, Esther; Belcari, Nicola; Guerra, Alberto Del; Cherry, Simon R.; Lehnert, Adrienne; Hunter, William C. J.; McDougald, Wendy; Miyaoka, Robert S.; Kinahan, Paul E.
2015-01-01
A feasibility study was done to assess the capability of digital silicon photomultipliers to measure the Cherenkov luminescence emitted by a β source. Cherenkov luminescence imaging (CLI) is possible with a charge coupled device (CCD) based technology, but a stand-alone technique for quantitative activity measurements based on Cherenkov luminescence has not yet been developed. Silicon photomultipliers (SiPMs) are photon counting devices with a fast impulse response and can potentially be used to quantify β-emitting radiotracer distributions by CLI. In this study, a Philips digital photon counting (PDPC) silicon photomultiplier detector was evaluated for measuring Cherenkov luminescence. The PDPC detector is a matrix of avalanche photodiodes, which were read one at a time in a dark count map (DCM) measurement mode (much like a CCD). This reduces the device active area but allows the information from a single avalanche photodiode to be preserved, which is not possible with analog SiPMs. An algorithm to reject the noisiest photodiodes and to correct the measured count rate for the dark current was developed. The results show that, in DCM mode and at (10–13) °C, the PDPC has a dynamic response to different levels of Cherenkov luminescence emitted by a β source and transmitted through an opaque medium. This suggests the potential for this approach to provide quantitative activity measurements. Interestingly, the potential use of the PDPC in DCM mode for direct imaging of Cherenkov luminescence, as a opposed to a scalar measurement device, was also apparent. We showed that a PDPC tile in DCM mode is able to detect and image a β source through its Cherenkov radiation emission. The detector’s dynamic response to different levels of radiation suggests its potential quantitative capabilities, and the DCM mode allows imaging with a better spatial resolution than the conventional event-triggered mode. Finally, the same acquisition procedure and data processing could
Luminescence properties of In(Zn)P alloy core/ZnS shell quantum dots
Thuy, Ung Thi Dieu; Reiss, Peter; Liem, Nguyen Quang
2010-11-01
Chemically synthesized InP/ZnS core/shell quantum dots (QDs) are studied using time-resolved photoluminescence spectroscopy and x-ray diffraction. Zinc stearate, which is added during the synthesis of the InP core, significantly improves the optical characteristics of the QDs. The luminescence quantum yield (QY) reaches 60%-70% and the emission is tunable from 485 to 586 nm by varying the Zn2+:In3+ molar ratio and growth temperature. The observed increased Stokes shift, luminescence decay time, and QY in the presence of Zn are rationalized by the formation of an In(Zn)P alloy structure that causes band-edge fluctuation to enhance the confinement of the excited carriers.
Zhuang, Si-Hui; Guo, Xin-Xin; Wu, Ying-Song; Chen, Zhen-Hua; Chen, Yao; Ren, Zhi-Qi; Liu, Tian-Cai
2016-01-01
The unique photoproperties of quantum dots are promising for potential application in bioassays. In the present study, quantum dots were applied to a luminescent oxygen channeling assay. The reaction system developed in this study was based on interaction of biotin with streptavidin. Carboxyl-modified polystyrene microspheres doped with quantum dots were biotinylated and used as acceptors. Photosensitizer-doped carboxyl-modified polystyrene microspheres were conjugated with streptavidin and used as donors. The results indicated that the singlet oxygen that was released from the donor beads diffused into the acceptor beads. The acceptor beads were then exited via thioxene, and were subsequently fluoresced. To avoid generating false positives, a high concentration (0.01 mg/mL) of quantum dots is required for application in homogeneous immunoassays. Compared to a conventional luminescent oxygen channeling assay, this quantum dots-based technique requires less time, and would be easier to automate and miniaturize because it requires no washing to remove excess labels.
Quantum measurement and algebraic quantum field theories
International Nuclear Information System (INIS)
DeFacio, B.
1976-01-01
It is shown that the physics and semantics of quantum measurement provide a natural interpretation of the weak neighborhoods of the states on observable algebras without invoking any ideas of ''a reading error'' or ''a measured range.'' Then the state preparation process in quantum measurement theory is shown to give the normal (or locally normal) states on the observable algebra. Some remarks are made concerning the physical implications of normal state for systems with an infinite number of degrees of freedom, including questions on open and closed algebraic theories
Spatially-resolved measurement of optically stimulated luminescence and time-resolved luminescence
International Nuclear Information System (INIS)
Bailiff, I.K.; Mikhailik, V.B.
2003-01-01
Spatially-resolved measurements of optically stimulated luminescence (OSL) were performed using a two-dimensional scanning system designed for use with planar samples. The scanning system employs a focused laser beam to stimulate a selected area of the sample, which is moved under the beam by a motorised stage. Exposure of the sample is controlled by an electronic shutter. Mapping of the distribution of OSL using a continuous wave laser source was obtained with sub-millimeter resolution for samples of sliced brick, synthetic single crystal quartz, concrete and dental ceramic. These revealed sporadic emission in the case of brick or concrete and significant spatial variation of emission for quartz and dental ceramic slices. Determinations of absorbed dose were performed for quartz grains within a slice of modern brick. Reconfiguration of the scanner with a pulsed laser source enabled quartz and feldspathic minerals within a ceramic sample to be thinner region. about 6 nm from the extrapolation of themeasuring the time-resolved luminescence spectrum
Quantum behaviour of measuring apparatus
International Nuclear Information System (INIS)
Amri, T.
2011-05-01
This thesis explores the quantum behavior of measurement apparatus with illustrations in quantum optics. This is the first study of quantum properties of measurements performed by any kind of devices. We show that the quantum properties of a measurement, such as its projective or non-classical character, are revealed only by the quantum states of an unusual approach of quantum physics: the retrodictive approach. This approach involves retro-predictions about state preparations leading to a given measurement result, contrary to the predictive approach with which we usually make predictions about the results of an experiment. By clarifying the mathematical foundations of the retrodictive approach, we propose a general procedure for reconstructing the quantum states of this approach: the retrodicted states. We have realized these reconstructions for single-photon detectors, widely used in quantum cryptography for instance. This is the first tomography of quantum states totally based on the retrodictive approach and preparation choices, contrary to usual reconstructions based on measurement results. These tomographies enabled us to study experimentally the noise influence on the quantum properties of measurements performed by these detectors, in particular their transition from a strongly quantum behavior into a more classical behavior. Finally, we propose a detector of Schroedinger's Cat states of light, which are superpositions of incompatible quasi-classical states of light. In a modern version of a thought experiment proposed by Eugene Wigner in 1961, such a device could allow the Wigner's Friend to detect a Schroedinger's Cat, contrary to human eyes for which we specify some quantum properties. We generalize the use of such a non-classical detector to an estimation protocol, totally based on the retrodictive approach and preparation choices. Such a procedure could enable optimal estimations, by reaching the quantum Cramer-Rao bound, which is a very topical issue
Low-cost photovoltaics: Luminescent solar concentrators and colloidal quantum dot solar cells
Leow, Shin Woei
Solar energy has long been lauded as an inexhaustible fuel source with more energy reaching the earth's surface in one hour than the global consumption for a year. Although capable of satisfying the world's energy requirements, solar energy remains an expensive technology that has yet to attain grid parity. Another drawback is that existing solar farms require large quantities of land in order to generate power at useful rates. In this work, we look to luminescent solar concentrator systems and quantum dot technology as viable solutions to lowering the cost of solar electricity production with the flexibility to integrate such technologies into buildings to achieve dual land use. Luminescent solar concentrator (LSC) windows with front-facing photovoltaic (PV) cells were built and their gain and power efficiency were investigated. Conventional LSCs employ a photovoltaic (PV) cell that is placed on the edge of the LSC, facing inward. This work describes a new design with the PV cells on the front-face allowing them to receive both direct solar irradiation and wave-guided photons emitted from a dye embedded in an acrylic sheet, which is optically coupled to the PV cells. Parameters investigated include the thickness of the waveguide, edge treatment of the window, cell width, and cell placement. The data allowed us to make projections that aided in designing windows for maximized overall efficiency. A gain in power of 2.2x over the PV cells alone was obtained with PV cell coverage of 5%, and a power conversion efficiency as high as 6.8% was obtained with a PV cell coverage of 31%. Balancing the trade-offs between gain and efficiency, the design with the lowest cost per watt attained a power efficiency of 3.8% and a gain of 1.6x. With the viability of the LSC demonstrated, a weighted Monte-Carlo Ray Tracing program was developed to study the transport of photons and loss mechanisms in the LSC to aid in design optimization. The program imports measured absorption
Energy Technology Data Exchange (ETDEWEB)
Ali, Junaid; Siddiqui, Ghayas Uddin [Department of Mechatronics Engineering, Jeju National University, Jeju (Korea, Republic of); Choi, Kyung Hyun, E-mail: amm@jejunu.ac.kr [Department of Mechatronics Engineering, Jeju National University, Jeju (Korea, Republic of); Jang, Yunseok [Department of Printed Electronics, Korea Institute of Machinery & Materials, Daejeon, Republic of Korea (Korea, Republic of); Lee, Kangtaek [Department of Chemical and Biomolecular Engineering, Yonsei University (Korea, Republic of)
2016-01-15
Molybdenum disulfide (MoS{sub 2}) belongs to transition-metal dichalcogenides (TMDs) family and has vital position among 2D materials. Here, an efficient strategy for the synthesis of zero-dimensional MoS{sub 2} quantum dots (QDs) has been represented. This strategy consists of wet grinding of pristine MoS{sub 2} in N-methyl-2-pyrrolidone (NMP) followed by sonication in NMP and 1,2-dichlorobenzene (o-DCB). The efficacy of this approach to synthesize MoS{sub 2} QDs has been reported by analyzing the as synthesized MoS{sub 2} QDs by different characterization techniques such as high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and UV–vis spectroscopy. The concentration (yield) of as synthesized MoS{sub 2} QDs was found to be 7 mg mL{sup −1}. Most of the MoS{sub 2} QDs were measured around 2–5 nm in size. The as synthesized MoS{sub 2} QDs showed distinct blue luminescence upon UV excitation. - Highlights: • Synthesis of MoS{sub 2} quantum dots. • Wet grinding of MoS{sub 2} flakes for 6 h in NMP. • Ultrasonication of MoS{sub 2} in NMP and DCB. • Particle size 2–5 nm and concentration 7 mg/ml. • MoS{sub 2} QDs showed blue luminescence.
Luminescence quantum efficiency determination in LiYF4:Nd3+ using photoacoustic spectroscopy
International Nuclear Information System (INIS)
Franca, E.J.
1989-01-01
Optical properties of LiYF 4 :Nd 3+ were studied using absorption, emission, excitation and photo acoustic spectroscopies. The Nd 3+ transitions were identified and the Stark sublevels were determined for the 4 I 9/2 , 4 I 11/2 and 4 F 3/2 levels. It is also presented and analysed three methods for the luminescence quantum efficiency determination, based on parameters from the spectra mentioned above. These methods were applied to four groups centered on 517, 577, 743 and 792nm. The first method provided values too high due to its assumption that the material has only one luminescent channel. The values obtained from the second one are still somewhat high but closer to the expected ones. The superestimation can be atributed to the imprecision in the existing branching ratios values, needed in this method. The third one, developed from the other two, provided values closer to the expected ones, but also affected by experimental conditions limitations, mainly related to the spectral resolution of the photoacustic spectra. The obtained results show that this method, once improved and associated to better experimental conditions, will lead to more accurate luminescence quantum efficiency values. (author) [pt
Erbium-implanted silica colloids with 80% luminescence quantum efficiency
Slooff, L. H.; de Dood, M. J. A.; van Blaaderen, A.; Polman, A.
2000-06-01
Silica colloids with a diameter of 240-360 nm, grown by wet chemical synthesis using ethanol, ammonia, water, and tetraethoxysilane, were implanted with 350 keV Er ions, to peak concentrations of 0.2-1.1 at. % and put onto a silicon or glass substrate. After annealing at 700-900 °C the colloids show clear room-temperature photoluminescence at 1.53 μm, with lifetimes as high as 17 ms. By comparing data of different Er concentrations, the purely radiative lifetime is estimated to be 20-22 ms, indicating a high quantum efficiency of about 80%. This high quantum efficiency indicates that, after annealing, the silica colloids are almost free of OH impurities. Spinning a layer of polymethylmethacrylate over the silica spheres results in an optically transparent nanocomposite layer, that can be used as a planar optical waveguide amplifier at 1.5 μm that is fully compatible with polymer technology.
InP/ZnSe/ZnS core-multishell quantum dots for improved luminescence efficiency
Greco, Tonino; Ippen, Christian; Wedel, Armin
2012-04-01
Semiconductor quantum dots (QDs) exhibit unique optical properties like size-tunable emission color, narrow emission peak, and high luminescence efficiency. QDs are therefore investigated towards their application in light-emitting devices (QLEDs), solar cells, and for bio-imaging purposes. In most cases QDs made from cadmium compounds like CdS, CdSe or CdTe are studied because of their facile and reliable synthesis. However, due to the toxicity of Cd compounds and the corresponding regulation (e.g. RoHS directive in Europe) these materials are not feasible for customer applications. Indium phosphide is considered to be the most promising alternative because of the similar band gap (InP 1.35 eV, CdSe 1.73 eV). InP QDs do not yet reach the quality of CdSe QDs, especially in terms of photoluminescence quantum yield and peak width. Typically, QDs are coated with another semiconductor material of wider band gap, often ZnS, to passivate surface defects and thus improve luminescence efficiency. Concerning CdSe QDs, multishell coatings like CdSe/CdS/ZnS or CdSe/ZnSe/ZnS have been shown to be advantageous due to the improved compatibility of lattice constants. Here we present a method to improve the luminescence efficiency of InP QDs by coating a ZnSe/ZnS multishell instead of a ZnS single shell. ZnSe exhibits an intermediate lattice constant of 5.67 Å between those of InP (5.87 Å) and ZnS (5.41 Å) and thus acts as a wetting layer. As a result, InP/ZnSe/ZnS is introduced as a new core-shell quantum dot material which shows improved photoluminescence quantum yield (up to 75 %) compared to the conventional InP/ZnS system.
Quantum nondemolition measurements for quantum information
International Nuclear Information System (INIS)
Ralph, T. C.; O'Brien, J. L.; Bartlett, S. D.; Pryde, G. J.; Wiseman, H. M.
2006-01-01
We discuss the characterization and properties of quantum nondemolition (QND) measurements on qubit systems. We introduce figures of merit which can be applied to systems of any Hilbert space dimension, thus providing universal criteria for characterizing QND measurements. The controlled-NOT gate and an optical implementation are examined as examples of QND devices for qubits. We also consider the QND measurement of weak values
Energy Technology Data Exchange (ETDEWEB)
López, Israel; Gómez, Idalia, E-mail: maria.gomezd@uanl.edu.mx
2014-11-15
Here the improvement of the luminescent properties of CdS quantum dots by a post-synthesis modification with aqueous solutions of NaOH at different concentrations is presented. The CdS quantum dots were synthesized by a microwave-assisted method using citrate ions as stabilizer. The addition of the hydroxide ions increased the intensity of the orange-red emission by about 80%. Besides, a violet-blue emission was achieved by means of this post-synthesis modification. The hydroxide ions control the precipitation equilibria of the CdS and Cd(OH){sub 2}, dissolving and precipitating the surface of the quantum dots. The NaOH treatment increases the number of traps, which produces less band-edge and more deep-trap emission, which explains the decrease and increase in the intensity of the violet-blue and orange-red emissions, respectively.
International Nuclear Information System (INIS)
López, Israel; Gómez, Idalia
2014-01-01
Here the improvement of the luminescent properties of CdS quantum dots by a post-synthesis modification with aqueous solutions of NaOH at different concentrations is presented. The CdS quantum dots were synthesized by a microwave-assisted method using citrate ions as stabilizer. The addition of the hydroxide ions increased the intensity of the orange-red emission by about 80%. Besides, a violet-blue emission was achieved by means of this post-synthesis modification. The hydroxide ions control the precipitation equilibria of the CdS and Cd(OH) 2 , dissolving and precipitating the surface of the quantum dots. The NaOH treatment increases the number of traps, which produces less band-edge and more deep-trap emission, which explains the decrease and increase in the intensity of the violet-blue and orange-red emissions, respectively
Effect of ion-implantation enhanced intermixing on luminescence of InAs/InP quantum dots
Energy Technology Data Exchange (ETDEWEB)
Li, Q; Barik, S; Tan, H H; Jagadish, C [Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra 0200 (Australia)
2008-10-21
Temperature dependent photoluminescence spectra of ion implanted InAs/InP quantum dots (QDs) followed by rapid thermal annealing were studied. By employing a recently developed luminescence model for localized states ensemble, the broadening of the distribution of the localized QD states was determined from the fitting to the luminescence peak energy positions. The broadening of the distribution of the localized QD states reduces due to ion-implantation enhanced intermixing. The contribution of carrier distribution within the localized QD states to the luminescence linewidth decreases after ion-implantation enhanced intermixing. The effect of doses and types of ions used for implantation were also investigated.
The quantum theory of measurement
Busch, Paul; Mittelstaedt, Peter
1996-01-01
The amazing accuracy in verifying quantum effects experimentally has recently renewed interest in quantum mechanical measurement theory. In this book the authors give within the Hilbert space formulation of quantum mechanics a systematic exposition of the quantum theory of measurement. Their approach includes the concepts of unsharp objectification and of nonunitary transformations needed for a unifying description of various detailed investigations. The book addresses advanced students and researchers in physics and philosophy of science. In this second edition Chaps. II-IV have been substantially rewritten. In particular, an insolubility theorem for the objectification problem has been formulated in full generality, which includes unsharp object observables and unsharp pointers.
Energy Technology Data Exchange (ETDEWEB)
Bodunov, Evgeny N. [Department of Physics, Petersburg State Transport University, St. Petersburg (Russian Federation); Danilov, Vladimir V. [Department of Physics, Petersburg State Transport University, St. Petersburg (Russian Federation); Vavilov State Optical Institute, St. Petersburg (Russian Federation); Panfutova, Anastasia S. [Vavilov State Optical Institute, St. Petersburg (Russian Federation); Simoes Gamboa, A.L. [Center of Information Optical Technologies, ITMO University, St. Petersburg (Russian Federation)
2016-04-15
While time-resolved luminescence spectroscopy is commonly used as a quantitative tool for the analysis of the dynamics of photoexcitation in colloidal semiconductor quantum dots, the interpretation of the virtually ubiquitous nonexponential decay profiles is frequently ambiguous, because the assumption of multiple discrete exponential components with distinct lifetimes for resolving the decays is often arbitrary. Here, an interpretation of the room-temperature luminescence decay of CdSe/ZnS semiconductor quantum dots in colloidal solutions is presented based on the Kohlrausch relaxation function. It is proposed that the decay can be understood by using the concept of Foerster resonance energy transfer (FRET) assuming that the role of acceptors of photoexcitation energy is played by high-frequency anharmonic molecular vibrations in the environment of the quantum dots. The term EVFRET (Electronic - Vibrational Foerster Resonance Energy Transfer) is introduced in order to unequivocally refer to this energy transfer process. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Luminescence model with quantum impact parameter for low energy ions
Cruz-Galindo, H S; Martínez-Davalos, A; Belmont-Moreno, E; Galindo, S
2002-01-01
We have modified an analytical model of induced light production by energetic ions interacting in scintillating materials. The original model is based on the distribution of energy deposited by secondary electrons produced along the ion's track. The range of scattered electrons, and thus the energy distribution, depends on a classical impact parameter between the electron and the ion's track. The only adjustable parameter of the model is the quenching density rho sub q. The modification here presented, consists in proposing a quantum impact parameter that leads to a better fit of the model to the experimental data at low incident ion energies. The light output response of CsI(Tl) detectors to low energy ions (<3 MeV/A) is fitted with the modified model and comparison is made to the original model.
Directory of Open Access Journals (Sweden)
Eremchev M. Yu.
2015-01-01
Full Text Available In this research a relation between the accuracy of restoration of the single quantum dots (QD CdSe/CdS/ZnS cross-cut coordinates and luminescence intensity was investigated. It was shown that the limit of the accuracy of determining the coordinates of a single QD for a considerable total amount of registered photons approaches its limiting value that is comparable to the size of the QD. It also means that the installation used in the research is mechanically stable enough to reach the limiting values of determination accuracy of point emitters coordinates.
Quantum mechanical irreversibility and measurement
Grigolini, P
1993-01-01
This book is intended as a tutorial approach to some of the techniques used to deal with quantum dissipation and irreversibility, with special focus on their applications to the theory of measurements. The main purpose is to provide readers without a deep expertise in quantum statistical mechanics with the basic tools to develop a critical judgement on whether the major achievements in this field have to be considered a satisfactory solution of quantum paradox, or rather this ambitious achievement has to be postponed to when a new physics, more general than quantum and classical physics, will
Quantum mechanics and precision measurements
International Nuclear Information System (INIS)
Ramsey, N.F.
1995-01-01
The accuracies of measurements of almost all fundamental physical constants have increased by factors of about 10000 during the past 60 years. Although some of the improvements are due to greater care, most are due to new techniques based on quantum mechanics. Although the Heisenberg Uncertainty Principle often limits measurement accuracies, in many cases the validity of quantum mechanics makes possible the vastly improved measurement accuracies. Seven quantum features that have a profound influence on the science of measurements are: 1) Existence of discrete quantum states of energy. 2) Energy conservation in transitions between two states. 3) Electromagnetic radiation of frequency v is quantized with energy hv per quantum. 4) The identity principle. 5) The Heisenberg Uncertainty Principle. 6) Addition of probability amplitudes (not probabilities). 7) Wave and coherent phase phenomena. Of these seven quantum features, only the Heisenberg Uncertainty Principle limits the accuracy of measurements, and its effect is often negligibly small. The other six features make possible much more accurate measurements of quantum systems than with almost all classical systems. These effects are discussed and illustrated
Quantum measurement and dynamical maps
International Nuclear Information System (INIS)
Sudarshan, E.C.G.
1985-01-01
The problem of measurement in a quantum system involves the interaction of a classical system with only a small number of degrees of freedom ('measuring apparatus') coupled to the quantum system which is being subjected to measurement. It has been the practice to think of the measuring apparatus as a quantum system with a very large number of degrees of freedom treated in the classical limit. It is, however, possible to formulate the problem in such a manner that the measuring apparatus is a classical system with a finite number of degrees of freedom; this involves the perception of the classical system as the projection of a quantum system. The use of dynamical maps, which are discussed in this paper, is shown to be of benefit in tackling this problem. (UK)
Photostable epoxy polymerized carbon quantum dots luminescent thin films and the performance study
Directory of Open Access Journals (Sweden)
Chang Zhang
Full Text Available High photostable epoxy polymerized carbon quantum dots (C-dots luminescent thin films were prepared and their performances were compared with the CdTe quantum dots (QDs. First, water soluble C-dots (λem = 543.60 nm were synthesized. Poly (ethylene glycol diglycidyl ether (PEG and diaminooctane were used as the polymer matrix to make the epoxy resin films. FT-IR spectra showed that there were vibration at 3448 cm−1 and 1644 cm−1 which contributed to -OH and -NH respectively. SEM observations showed that the polymerizations of the films were uniform and there were no structure defects. Mechanical tests showed the tensile modulus of C-dots composite films were 4.6, 4.9, 6.4 and 7.8 MPa respectively with corresponding 0%, 1%, 2% and 5% mass fraction of C-dots, while the tensile modulus of CdTe QDs films were 4.6 MPa under the same mass fraction of CdTe QDs. Compared with semiconductor QDs, the decay of quantum yield were 5% and 10% for the C-dots and CdTe QDs, respectively. The pictures in the continuous irradiation of 48 h showed that the C-dots film was more photostable. This study provides much helpful and profound towards the fluorescent enhancement films in the field of flexible displays. Keywords: Carbon-dots, Waterborne epoxy resin, Luminescent materials, Quantum dots displays
Cloning of a quantum measurement
International Nuclear Information System (INIS)
Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo; Sedlak, Michal
2011-01-01
We analyze quantum algorithms for cloning of a quantum measurement. Our aim is to mimic two uses of a device performing an unknown von Neumann measurement with a single use of the device. When the unknown device has to be used before the bipartite state to be measured is available we talk about 1→2 learning of the measurement, otherwise the task is called 1→2 cloning of a measurement. We perform the optimization for both learning and cloning for arbitrary dimension d of the Hilbert space. For 1→2 cloning we also propose a simple quantum network that achieves the optimal fidelity. The optimal fidelity for 1→2 learning just slightly outperforms the estimate and prepare strategy in which one first estimates the unknown measurement and depending on the result suitably prepares the duplicate.
Cloning of a quantum measurement
Energy Technology Data Exchange (ETDEWEB)
Bisio, Alessandro; D' Ariano, Giacomo Mauro; Perinotti, Paolo; Sedlak, Michal [QUIT Group, Dipartimento di Fisica ' ' A. Volta' ' and INFN, via Bassi 6, I-27100 Pavia (Italy); QUIT Group, Dipartimento di Fisica ' ' A. Volta' ' via Bassi 6, I-27100 Pavia (Italy) and Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-845 11 Bratislava (Slovakia)
2011-10-15
We analyze quantum algorithms for cloning of a quantum measurement. Our aim is to mimic two uses of a device performing an unknown von Neumann measurement with a single use of the device. When the unknown device has to be used before the bipartite state to be measured is available we talk about 1{yields}2 learning of the measurement, otherwise the task is called 1{yields}2 cloning of a measurement. We perform the optimization for both learning and cloning for arbitrary dimension d of the Hilbert space. For 1{yields}2 cloning we also propose a simple quantum network that achieves the optimal fidelity. The optimal fidelity for 1{yields}2 learning just slightly outperforms the estimate and prepare strategy in which one first estimates the unknown measurement and depending on the result suitably prepares the duplicate.
International Nuclear Information System (INIS)
Shamsipur, Mojtaba; Rajabi, Hamid Reza
2014-01-01
A rapid and simple fluorescence method is presented for selective and sensitive determination of hazardous cyanide ion in aqueous solution based on functionalized zinc sulfide (ZnS) quantum dot (QD) as luminescent prob. The ultra-small ZnS QDs were synthesized using a chemical co-precipitation method in the presence of 2-mercaptoethanol (ME) as an efficient capping agent. The prepared pure ZnS QDs was applied as an optical sensor for determination of cyanide ions in aqueous solutions. ZnS nanoparticles have exhibited a strong fluorescent emission at about 424 nm. The fluorescence intensity of QDs is linearly proportional to the cyanide ion concentration in the range 2.44 × 10 −6 to 2.59 × 10 −5 M with a detection limit of 1.70 × 10 −7 M at pH 11. The designed fluorescent sensor possesses remarkable selectivity for cyanide ion over other anions such as Cl − , Br − , F − , I − , IO 3 − , ClO 4 − , BrO 3 − , CO 3 2− , NO 2 − , NO 3 − , SO 4 2− , S 2 O 4 2− , C 2 O 4 2− , SCN − , N 3 − , citrate and tartarate with negligible influences on the cyanide detection by fluorescence spectroscopy. - Highlights: • Preparation of functionalized ZnS quantum dots in aqueous media • Highly selective quantum dot based luminescent probe for determination of cyanide • Fast and sensitive determination of hazardous CN − by fluorescence quenching
Energy Technology Data Exchange (ETDEWEB)
Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.com [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Rajabi, Hamid Reza, E-mail: h.rajabi@mail.yu.ac.ir [Chemistry Department, Yasouj University, Yasouj 75918-74831 (Iran, Islamic Republic of)
2014-03-01
A rapid and simple fluorescence method is presented for selective and sensitive determination of hazardous cyanide ion in aqueous solution based on functionalized zinc sulfide (ZnS) quantum dot (QD) as luminescent prob. The ultra-small ZnS QDs were synthesized using a chemical co-precipitation method in the presence of 2-mercaptoethanol (ME) as an efficient capping agent. The prepared pure ZnS QDs was applied as an optical sensor for determination of cyanide ions in aqueous solutions. ZnS nanoparticles have exhibited a strong fluorescent emission at about 424 nm. The fluorescence intensity of QDs is linearly proportional to the cyanide ion concentration in the range 2.44 × 10{sup −6} to 2.59 × 10{sup −5} M with a detection limit of 1.70 × 10{sup −7} M at pH 11. The designed fluorescent sensor possesses remarkable selectivity for cyanide ion over other anions such as Cl{sup −}, Br{sup −}, F{sup −}, I{sup −}, IO{sub 3}{sup −}, ClO{sub 4}{sup −}, BrO{sub 3}{sup −}, CO{sub 3}{sup 2−}, NO{sub 2}{sup −}, NO{sub 3}{sup −}, SO{sub 4}{sup 2−}, S{sub 2}O{sub 4}{sup 2−}, C{sub 2}O{sub 4}{sup 2−}, SCN{sup −}, N{sub 3}{sup −}, citrate and tartarate with negligible influences on the cyanide detection by fluorescence spectroscopy. - Highlights: • Preparation of functionalized ZnS quantum dots in aqueous media • Highly selective quantum dot based luminescent probe for determination of cyanide • Fast and sensitive determination of hazardous CN{sup −} by fluorescence quenching.
Quantum Inequalities and Sequential Measurements
International Nuclear Information System (INIS)
Candelpergher, B.; Grandouz, T.; Rubinx, J.L.
2011-01-01
In this article, the peculiar context of sequential measurements is chosen in order to analyze the quantum specificity in the two most famous examples of Heisenberg and Bell inequalities: Results are found at some interesting variance with customary textbook materials, where the context of initial state re-initialization is described. A key-point of the analysis is the possibility of defining Joint Probability Distributions for sequential random variables associated to quantum operators. Within the sequential context, it is shown that Joint Probability Distributions can be defined in situations where not all of the quantum operators (corresponding to random variables) do commute two by two. (authors)
Liu, Feng; Zhang, Yaohong; Ding, Chao; Kobayashi, Syuusuke; Izuishi, Takuya; Nakazawa, Naoki; Toyoda, Taro; Ohta, Tsuyoshi; Hayase, Shuzi; Minemoto, Takashi; Yoshino, Kenji; Dai, Songyuan; Shen, Qing
2017-10-24
Perovskite quantum dots (QDs) as a new type of colloidal nanocrystals have gained significant attention for both fundamental research and commercial applications owing to their appealing optoelectronic properties and excellent chemical processability. For their wide range of potential applications, synthesizing colloidal QDs with high crystal quality is of crucial importance. However, like most common QD systems such as CdSe and PbS, those reported perovskite QDs still suffer from a certain density of trapping defects, giving rise to detrimental nonradiative recombination centers and thus quenching luminescence. In this paper, we show that a high room-temperature photoluminescence quantum yield of up to 100% can be obtained in CsPbI 3 perovskite QDs, signifying the achievement of almost complete elimination of the trapping defects. This is realized with our improved synthetic protocol that involves introducing organolead compound trioctylphosphine-PbI 2 (TOP-PbI 2 ) as the reactive precursor, which also leads to a significantly improved stability for the resulting CsPbI 3 QD solutions. Ultrafast kinetic analysis with time-resolved transient absorption spectroscopy evidence the negligible electron or hole-trapping pathways in our QDs, which explains such a high quantum efficiency. We expect the successful synthesis of the "ideal" perovskite QDs will exert profound influence on their applications to both QD-based light-harvesting and -emitting devices.
Measurement theory in quantum mechanics
International Nuclear Information System (INIS)
Klein, G.
1980-01-01
It is assumed that consciousness, memory and liberty (within the limits of the quantum mechanics indeterminism) are fundamental properties of elementary particles. Then, using this assumption it is shown how measurements and observers may be introduced in a natural way in the quantum mechanics theory. There are no longer fundamental differences between macroscopic and microscopic objects, between classical and quantum objects, between observer and object. Thus, discrepancies and paradoxes have disappeared from the conventional quantum mechanics theory. One consequence of the cumulative memory of the particles is that the sum of negentropy plus information is a constant. Using this theory it is also possible to explain the 'paranormal' phenomena and what is their difference from the 'normal' ones [fr
Mikhailov, I. I.; Tarasov, S. A.; Lamkin, I. A.; Tadtaev, P. O.; Kozlovich, L. I.; Solomonov, A. V.; Stepanov, E. M.
2016-08-01
The luminescent organic ITO/TPD/Alq3/Al structures and CdSe/ZnS quantum dots (QD) arrays were created. Electrical and optical properties of the samples were examined. The luminescence of the layers and QD arrays was shown in the range of wavelengths from 400 to 680 nm. Luminescent structures with phosphors corresponding to the emission standards with CRI>98 and with color temperature of 5500 K and 6504 K were created.
Montalti, M; Cantelli, A; Battistelli, G
2015-07-21
Fluorescence bioimaging is a powerful, versatile, method for investigating, both in vivo and in vitro, the complex structures and functions of living organisms in real time and space, also using super-resolution techniques. Being poorly invasive, fluorescence bioimaging is suitable for long-term observation of biological processes. Long-term detection is partially prevented by photobleaching of organic fluorescent probes. Semiconductor quantum dots, in contrast, are ultrastable, fluorescent contrast agents detectable even at the single nanoparticle level. Emission color of quantum dots is size dependent and nanoprobes emitting in the near infrared (NIR) region are ideal for low back-ground in vivo imaging. Biocompatibility of nanoparticles, containing toxic elements, is debated. Recent safety concerns enforced the search for alternative ultrastable luminescent nanoprobes. Most recent results demonstrated that optimized silicon quantum dots (Si QDs) and fluorescent nanodiamonds (FNDs) show almost no photobleaching in a physiological environment. Moreover in vitro and in vivo toxicity studies demonstrated their unique biocompatibility. Si QDs and FNDs are hence ideal diagnostic tools and promising non-toxic vectors for the delivery of therapeutic cargos. Most relevant examples of applications of Si QDs and FNDs to long-term bioimaging are discussed in this review comparing the toxicity and the stability of different nanoprobes.
Meinardi, Francesco; Ehrenberg, Samantha; Dhamo, Lorena; Carulli, Francesco; Mauri, Michele; Bruni, Francesco; Simonutti, Roberto; Kortshagen, Uwe; Brovelli, Sergio
2017-02-01
Building-integrated photovoltaics is gaining consensus as a renewable energy technology for producing electricity at the point of use. Luminescent solar concentrators (LSCs) could extend architectural integration to the urban environment by realizing electrode-less photovoltaic windows. Crucial for large-area LSCs is the suppression of reabsorption losses, which requires emitters with negligible overlap between their absorption and emission spectra. Here, we demonstrate the use of indirect-bandgap semiconductor nanostructures such as highly emissive silicon quantum dots. Silicon is non-toxic, low-cost and ultra-earth-abundant, which avoids the limitations to the industrial scaling of quantum dots composed of low-abundance elements. Suppressed reabsorption and scattering losses lead to nearly ideal LSCs with an optical efficiency of η = 2.85%, matching state-of-the-art semi-transparent LSCs. Monte Carlo simulations indicate that optimized silicon quantum dot LSCs have a clear path to η > 5% for 1 m2 devices. We are finally able to realize flexible LSCs with performances comparable to those of flat concentrators, which opens the way to a new design freedom for building-integrated photovoltaics elements.
Magnetic enhancement of photoluminescence from blue-luminescent graphene quantum dots
Chen, Qi; Shi, Chentian; Zhang, Chunfeng; Pu, Songyang; Wang, Rui; Wu, Xuewei; Wang, Xiaoyong; Xue, Fei; Pan, Dengyu; Xiao, Min
2016-02-01
Graphene quantum-dots (GQDs) have been predicted and demonstrated with fascinating optical and magnetic properties. However, the magnetic effect on the optical properties remains experimentally unexplored. Here, we conduct a magneto-photoluminescence study on the blue-luminescence GQDs at cryogenic temperatures with magnetic field up to 10 T. When the magnetic field is applied, a remarkable enhancement of photoluminescence emission has been observed together with an insignificant change in circular polarization. The results have been well explained by the scenario of magnetic-field-controlled singlet-triplet mixing in GQDs owing to the Zeeman splitting of triplet states, which is further verified by temperature-dependent experiments. This work uncovers the pivotal role of intersystem crossing in GQDs, which is instrumental for their potential applications such as light-emitting diodes, photodynamic therapy, and spintronic devices.
Luminescent, water-soluble silicon quantum dots via micro-plasma surface treatment
International Nuclear Information System (INIS)
Wu, Jeslin J; Siva Santosh Kumar Kondeti, Vighneswara; Bruggeman, Peter J; Kortshagen, Uwe R
2016-01-01
Silicon quantum dots (SiQDs), with their broad absorption, narrow and size-tunable emission, and potential biocompatibility are highly attractive materials in biological imaging applications. The inherent hydrophobicity and instability of hydrogen-terminated SiQDs are obstacles to their widespread implementation. In this work, we successfully produced highly luminescent, hydrophilic SiQDs with long-term stability in water using non-thermal plasma techniques. Hydrogen-terminated SiQDs were produced in a low-pressure plasma and subsequently treated in water using an atmospheric-pressure plasma jet for surface modification. Preliminary assessments of the chemical mechanism(s) involved in the creation of water-soluble SiQDs were performed using Fenton’s reaction and various plasma chemistries, suggesting both OH and O species play a key role in the oxidation of the SiQDs. (letter)
Gui, Rijun; Jin, Hui; Liu, Xifeng; Wang, Zonghua; Zhang, Feifei; Xia, Jianfei; Yang, Min; Bi, Sai
2014-12-07
Under the two-photon excitation, upconversion luminescent "INHIBIT" and "OR" logic gates of water-dispersed CdTe quantum dots (QDs) were constituted by conjugating the QDs with dopamine. This facilitated the development of a novel QDs-based upconversion luminescent probe for efficient turn-on sensing of glutathione.
Quantum market games: implementing tactics via measurements
International Nuclear Information System (INIS)
Pakula, I; Piotrowski, E W; Sladkowski, J
2006-01-01
A major development in applying quantum mechanical formalism to various fields has been made during the last few years. Quantum counterparts of Game Theory, Economy, as well as diverse approaches to Quantum Information Theory have been found and currently are being explored. Using connections between Quantum Game Theory and Quantum Computations, an application of the universality of a measurement based computation in Quantum Market Theory is presented
International Nuclear Information System (INIS)
Gruzintsev, A.N.; Volkov, V.T.; Emelchenko, G.A.; Karpov, I.A.; Maslov, W.M.; Michailov, G.M.; Yakimov, E.E.
2004-01-01
The luminescence properties of ZnO films of different thickness obtained on a synthetic opal were investigated. Several narrow peaks in the exciton emission region related to the size quantum effect of the electron wave functions were detected. Two-dimensional ordered array of ZnO quantum dots formed inside the opal pores on the second sphere layer were found by the atomic force microscopy (AFM) and angle dependence of the luminescence spectra
Effect of antimony incorporation on the density, shape, and luminescence of InAs quantum dots
Chen, J. F.; Chiang, C. H.; Wu, Y. H.; Chang, L.; Chi, J. Y.
2008-07-01
This work investigates the surfactant effect on exposed and buried InAs quantum dots (QDs) by incorporating Sb into the QD layers with various Sb beam equivalent pressures (BEPs). Secondary ion mass spectroscopy shows the presence of Sb in the exposed and buried QD layers with the Sb intensity in the exposed layer substantially exceeding that in the buried layer. Incorporating Sb can reduce the density of the exposed QDs by more than two orders of magnitude. However, a high Sb BEP yields a surface morphology with a regular periodic structure of ellipsoid terraces. A good room-temperature photoluminescence (PL) at ˜1600 nm from the exposed QDs is observed, suggesting that the Sb incorporation probably improves the emission efficiency by reducing the surface recombination velocity at the surface of the exposed QDs. Increasing Sb BEP causes a blueshift of the emission from the exposed QDs due to a reduction in the dot height as suggested by atomic force microscopy. Increasing Sb BEP can also blueshift the ˜1300 nm emission from the buried QDs by decreasing the dot height. However, a high Sb BEP yields a quantum well-like PL feature formed by the clustering of the buried QDs into an undulated planar layer. These results indicate a marked Sb surfactant effect that can be used to control the density, shape, and luminescence of the exposed and buried QDs.
International Nuclear Information System (INIS)
Zhu, Xiaohua; Zuo, Xiaoxi; Hu, Ruiping; Xiao, Xin; Liang, Yong; Nan, Junmin
2014-01-01
A simple and effective chemical synthesis of the photoluminescent nitrogen-doped graphene quantum dots (N-GQDs) biomaterial is reported. Using the hydrothermal treatment of graphene oxide (GO) in the presence of hydrogen peroxide (H 2 O 2 ) and ammonia, the N-GQDs are synthesized through H 2 O 2 exfoliating the GO into nanocrystals with lateral dimensions and ammonia passivating the generated active surface. Then, after a dialytic separation, two water-soluble N-GQDs with average size of about 2.1 nm/6.2 nm, which emit green/khaki luminescence and exhibit excitation dependent/independent photoluminescence (PL) behaviors, are obtained. In addition, it is also demonstrated that these two N-GQDs are stable over a broad pH range and have the upconversion PL property, showing this approach provides a simple and effective method to synthesize the functional N-GQDs. - Highlights: • Nitrogen-doped graphene quantum dots (N-GQDs) are prepared by hydrothermal routine. • Two N-GQDs with different size distribution emit green/khaki photoluminescence. • Two N-GQDs exhibit excitation-dependent/independent photoluminescence behaviors
Quantum ergodicity in a quantum measure algebra
International Nuclear Information System (INIS)
Stechel, E.B.
1986-01-01
This paper is divided into two parts. Part I assembles three pieces of background necessary to develop the logic behind this result. Section IA is devoted to classical algebraic ergodic theory (AET). Section IB briefly discusses random matrix theory (RMT) which should require very little development since a large fraction of this volume is devoted to this subject. Section IC reviews the concepts in quantum ''phase'' space flow (P(a,b)'s and p/sub n//sup a/'s). Part II develops what the authors will call quantum AET (the quantum analog of classical AET). Section IIA presents the formal development with the new definitions. Section IIB discusses intensity fluctuations in quantum ergodic (QE) spectra, leading to the somewhat surprising result that in a QE system a pure, real, smooth state samples only about 1/3 of its available space
Quantum learning by measurement and feedback
DEFF Research Database (Denmark)
Gammelmark, Søren; Mølmer, Klaus
2009-01-01
We investigate an approach to quantum computing in which quantum gate strengths are parametrized by quantum degrees of freedom. The capability of the quantum computer to perform desired tasks is monitored by measurements of the output and gradually improved by successive feedback modifications...
Quantum Learning by Measurement and Feedback
DEFF Research Database (Denmark)
Gammelmark, Søren
We investigate an approach to quantum computing in which quantum gate strengths are parametrized by quantum degrees of freedom. The capability of the quantum computer to perform desired tasks is monitored by measurements of the output and gradually improved by successive feedback modifications...
Optimal control of quantum measurement
Energy Technology Data Exchange (ETDEWEB)
Egger, Daniel; Wilhelm, Frank [Theoretical Physics, Saarland University, 66123 Saarbruecken (Germany)
2015-07-01
Pulses to steer the time evolution of quantum systems can be designed with optimal control theory. In most cases it is the coherent processes that can be controlled and one optimizes the time evolution towards a target unitary process, sometimes also in the presence of non-controllable incoherent processes. Here we show how to extend the GRAPE algorithm in the case where the incoherent processes are controllable and the target time evolution is a non-unitary quantum channel. We perform a gradient search on a fidelity measure based on Choi matrices. We illustrate our algorithm by optimizing a measurement pulse for superconducting phase qubits. We show how this technique can lead to large measurement contrast close to 99%. We also show, within the validity of our model, that this algorithm can produce short 1.4 ns pulses with 98.2% contrast.
Geometric measure of quantum discord and total quantum correlations in an N-partite quantum state
International Nuclear Information System (INIS)
Hassan, Ali Saif M; Joag, Pramod S
2012-01-01
Quantum discord, as introduced by Ollivier and Zurek (2001 Phys. Rev. Lett. 88 017901), is a measure of the discrepancy between quantum versions of two classically equivalent expressions for mutual information and is found to be useful in quantification and application of quantum correlations in mixed states. It is viewed as a key resource present in certain quantum communication tasks and quantum computational models without containing much entanglement. An early step toward the quantification of quantum discord in a quantum state was by Dakic et al (2010 Phys. Rev. Lett. 105 190502) who introduced a geometric measure of quantum discord and derived an explicit formula for any two-qubit state. Recently, Luo and Fu (2010 Phys. Rev. A 82 034302) introduced a generic form of the geometric measure of quantum discord for a bipartite quantum state. We extend these results and find generic forms of the geometric measure of quantum discord and total quantum correlations in a general N-partite quantum state. Further, we obtain computable exact formulas for the geometric measure of quantum discord and total quantum correlations in an N-qubit quantum state. The exact formulas for the N-qubit quantum state can be used to get experimental estimates of the quantum discord and the total quantum correlation. (paper)
Directory of Open Access Journals (Sweden)
Hyeoung Woo Park
2012-01-01
Full Text Available We have investigated the effect of water (H2O cooling and heat treatment on the luminescence efficiency of core CdSe quantum dots (QDs. The photoluminescence (PL quantum yield of the CdSe QDs was enhanced up to ~85%, and some periodic bright points were observed in wide color ranges during the heat treatment of QDs mixed with H2O. The PL enhancement of QDs could be attributed to the recovery of QDs surface traps by unreacted ligands confined within the hydrophilic H2O molecule containers.
Function Package for Computing Quantum Resource Measures
Huang, Zhiming
2018-05-01
In this paper, we present a function package for to calculate quantum resource measures and dynamics of open systems. Our package includes common operators and operator lists, frequently-used functions for computing quantum entanglement, quantum correlation, quantum coherence, quantum Fisher information and dynamics in noisy environments. We briefly explain the functions of the package and illustrate how to use the package with several typical examples. We expect that this package is a useful tool for future research and education.
Energy Technology Data Exchange (ETDEWEB)
Borissevitch, I.E., E-mail: iourib@ffclrp.usp.br [Departamento de Fisica, Faculdade de Filosofia Ciencia e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes 3900, Ribeirao Preto, SP (Brazil); Parra, G.G. [Departamento de Fisica, Faculdade de Filosofia Ciencia e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes 3900, Ribeirao Preto, SP (Brazil); Zagidullin, V.E.; Lukashev, E.P.; Knox, P.P.; Paschenko, V.Z.; Rubin, A.B. [Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Vorobyovy Gory, 119991 Moscow (Russian Federation)
2013-02-15
In this work we report on the study of the interaction of CdSe/ZnS-PEGOH 570 Quantum Dot (QD) with negatively charged meso-tetrakis(p-sulfonato-phenyl)porphyrin (TPPS{sub 4}) using optical absorption and fluorescence spectroscopies accompanied with time resolved 'single photon counting' and dynamic and resonance light scattering techniques. In the steady-state experiments the QD luminescence quenching by TPPS{sub 4} was well approximated by a square law. In the time-resolved experiments we observed a typical multi-exponential luminescence decay curve, successfully fitted by a bi-exponential approximation. At QD interaction with porphyrin the time quenching of both components was described by a linear Stern-Volmer dependence. The discrepancy between Stern-Volmer dependences in the steady-state and time resolved experiments may be due to formation of mixed m(TPPS{sub 4})+n(QD) complexes, in which one TPPS{sub 4} molecule can quench several excited QDs. This idea is in accordance with the dynamic and resonance light scattering data, which demonstrate an increase of the scattering particle size at the TPPS{sub 4} addition to QD solutions. - Highlights: Black-Right-Pointing-Pointer Quantum Dot luminescence quenching by TPPS porphyrin was studied in water solutions. Black-Right-Pointing-Pointer The size of particles in QD solutions possessed increase at the TPPS4 addition. Black-Right-Pointing-Pointer Quenching of the QD luminescence by TPPS4 is realized in contact QD-porphyrin complexes. Black-Right-Pointing-Pointer The formation of mixed quantum dot-porphyrin aggregates takes place.
International Nuclear Information System (INIS)
Borissevitch, I.E.; Parra, G.G.; Zagidullin, V.E.; Lukashev, E.P.; Knox, P.P.; Paschenko, V.Z.; Rubin, A.B.
2013-01-01
In this work we report on the study of the interaction of CdSe/ZnS-PEGOH 570 Quantum Dot (QD) with negatively charged meso-tetrakis(p-sulfonato-phenyl)porphyrin (TPPS 4 ) using optical absorption and fluorescence spectroscopies accompanied with time resolved “single photon counting” and dynamic and resonance light scattering techniques. In the steady-state experiments the QD luminescence quenching by TPPS 4 was well approximated by a square law. In the time-resolved experiments we observed a typical multi-exponential luminescence decay curve, successfully fitted by a bi-exponential approximation. At QD interaction with porphyrin the time quenching of both components was described by a linear Stern–Volmer dependence. The discrepancy between Stern–Volmer dependences in the steady-state and time resolved experiments may be due to formation of mixed m(TPPS 4 )+n(QD) complexes, in which one TPPS 4 molecule can quench several excited QDs. This idea is in accordance with the dynamic and resonance light scattering data, which demonstrate an increase of the scattering particle size at the TPPS 4 addition to QD solutions. - Highlights: ► Quantum Dot luminescence quenching by TPPS porphyrin was studied in water solutions. ► The size of particles in QD solutions possessed increase at the TPPS4 addition. ► Quenching of the QD luminescence by TPPS4 is realized in contact QD–porphyrin complexes. ► The formation of mixed quantum dot–porphyrin aggregates takes place.
Quantum theory of measurements as quantum decision theory
International Nuclear Information System (INIS)
Yukalov, V I; Sornette, D
2015-01-01
Theory of quantum measurements is often classified as decision theory. An event in decision theory corresponds to the measurement of an observable. This analogy looks clear for operationally testable simple events. However, the situation is essentially more complicated in the case of composite events. The most difficult point is the relation between decisions under uncertainty and measurements under uncertainty. We suggest a unified language for describing the processes of quantum decision making and quantum measurements. The notion of quantum measurements under uncertainty is introduced. We show that the correct mathematical foundation for the theory of measurements under uncertainty, as well as for quantum decision theory dealing with uncertain events, requires the use of positive operator-valued measure that is a generalization of projection-valued measure. The latter is appropriate for operationally testable events, while the former is necessary for characterizing operationally uncertain events. In both decision making and quantum measurements, one has to distinguish composite nonentangled events from composite entangled events. Quantum probability can be essentially different from classical probability only for entangled events. The necessary condition for the appearance of an interference term in the quantum probability is the occurrence of entangled prospects and the existence of an entangled strategic state of a decision maker or of an entangled statistical state of a measuring device
How much a quantum measurement is informative?
Energy Technology Data Exchange (ETDEWEB)
Dall' Arno, Michele [Graduate School of Information Science, Nagoya University, Nagoya, 464-8601 (Japan); ICFO-Institut de Ciencies Fotoniques, E-08860 Castelldefels, Barcelona (Spain); Quit Group, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia (Italy); D' Ariano, Giacomo Mauro [Quit Group, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia, Italy and Istituto Nazionale di Fisica Nucleare, Gruppo IV, via Bassi 6, I-27100 Pavia (Italy); Sacchi, Massimiliano F. [Quit Group, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia, Italy and Istituto di Fotonica e Nanotecnologie (INF-CNR), P.zza L. da Vinci 32, I-20133, Milano (Italy)
2014-12-04
The informational power of a quantum measurement is the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We discuss its main properties. Informational power is an additive quantity, being equivalent to the classical capacity of a quantum-classical channel. The informational power of a quantum measurement is the maximum of the accessible information of a quantum ensemble that depends on the measurement. We present some examples where the symmetry of the measurement allows to analytically derive its informational power.
Classical randomness in quantum measurements
International Nuclear Information System (INIS)
D'Ariano, Giacomo Mauro; Presti, Paoloplacido Lo; Perinotti, Paolo
2005-01-01
Similarly to quantum states, also quantum measurements can be 'mixed', corresponding to a random choice within an ensemble of measuring apparatuses. Such mixing is equivalent to a sort of hidden variable, which produces a noise of purely classical nature. It is then natural to ask which apparatuses are indecomposable, i.e. do not correspond to any random choice of apparatuses. This problem is interesting not only for foundations, but also for applications, since most optimization strategies give optimal apparatuses that are indecomposable. Mathematically the problem is posed describing each measuring apparatus by a positive operator-valued measure (POVM), which gives the statistics of the outcomes for any input state. The POVMs form a convex set, and in this language the indecomposable apparatuses are represented by extremal points-the analogous of 'pure states' in the convex set of states. Differently from the case of states, however, indecomposable POVMs are not necessarily rank-one, e.g. von Neumann measurements. In this paper we give a complete classification of indecomposable apparatuses (for discrete spectrum), by providing different necessary and sufficient conditions for extremality of POVMs, along with a simple general algorithm for the decomposition of a POVM into extremals. As an interesting application, 'informationally complete' measurements are analysed in this respect. The convex set of POVMs is fully characterized by determining its border in terms of simple algebraic properties of the corresponding POVMs
Luminescent ZnO quantum dots as an efficient sensor for free chlorine detection in water.
Singh, Kulvinder; Mehta, S K
2016-04-21
Highly luminescent ZnO quantum dots (QDs) synthesized via a simple and facile route are used for the preparation of an optical sensor for the detection of free chlorine. The concentration of free chlorine greatly affects the PL emission of the ZnO QDs at 525 nm. Since hypochlorite gains electrons with high efficiency, it takes electrons from the oxygen vacancies of ZnO QDs, which gives rise to defect emission in ZnO QDs. UV-vis data analysis shows that free chlorine does not affect the optical absorption spectra of ZnO QDs. The optical sensing of free chlorine using ZnO QDs has several advantages, like quick response time, good selectivity and of course high sensitivity. The pH has very little effect on the PL emission of ZnO QDs. It does not interfere in the sensing mechanism for free chlorine. After 60 s, the response of the ZnO QDs remains stable. The present sensor shows high selectivity with respect to various common cations, as well as anions.
Improving Students' Understanding of Quantum Measurement
International Nuclear Information System (INIS)
Zhu Guangtian; Singh, Chandralekha
2010-01-01
We describe the difficulties advanced undergraduate and graduate students have with quantum measurement. To reduce these difficulties, we have developed research-based learning tools such as the Quantum Interactive Learning Tutorial (QuILT) and peer instruction tools. A preliminary evaluation shows that these learning tools are effective in improving students' understanding of concepts related to quantum measurement.
Study of carrier concentration in single InP nanowires by luminescence and Hall measurements
International Nuclear Information System (INIS)
Lindgren, David; Hultin, Olof; Heurlin, Magnus; Storm, Kristian; Borgström, Magnus T; Samuelson, Lars; Gustafsson, Anders
2015-01-01
The free electron carrier concentrations in single InP core–shell nanowires are determined by micro-photoluminescence, cathodoluminescence (CL) and Hall effect measurements. The results from luminescence measurements were obtained by solving the Fermi–Dirac integral, as well as by analyzing the peak full width at half maximum (FWHM). Furthermore, the platform used for Hall effect measurements, combined with spot mode CL spectroscopy, is used to determine the carrier concentrations at specific positions along single nanowires. The results obtained via luminescence measurements provide an accurate and rapid feedback technique for the epitaxial development of doping incorporation in nanowires. The technique has been employed on several series of samples in which growth parameters, such as V/III-ratio, temperature and dopant flows, were investigated in an optimization procedure. The correlation between the Hall effect and luminescence measurements for extracting the carrier concentration of different samples were in excellent agreement. (paper)
Energy Technology Data Exchange (ETDEWEB)
Mirnajafizadeh, Fatemeh; Ramsey, Deborah; McAlpine, Shelli [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Wang, Fan; Reece, Peter [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Stride, John Arron, E-mail: j.stride@unsw.edu.au [School of Chemistry, University of New South Wales, Sydney, NSW 2052 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234 (Australia)
2016-07-01
Highly luminescent quantum dots (QDs) that emit in the visible spectrum are of interest to a number of imaging technologies, not least that of biological samples. One issue that hinders the application of luminescent markers in biology is the potential toxicity of the fluorophore. Here we show that hydrothermally synthesized ZnSe(S) QDs have low cytotoxicity to both human colorectal carcinoma cells (HCT-116) and human skin fibroblast cells (WS1). The QDs exhibited a high degree of crystallinity, with a strong blue photoluminescence at up to 29% quantum yield relative to 4′,6-diamidino-2-phenylindole (DAPI) without post-synthetic UV-irradiation. Confocal microscopy images obtained of HCT-116 cells after incubation with the QDs highlighted the stability of the particles in cell media. Cytotoxicity studies showed that both HCT-116 and WS1 cells retain 100% viability after treatment with the QDs at concentrations up to 0.5 g/L, which makes them of potential use in biological imaging applications. - Highlights: • Highly luminescent ZnSe(S) QDs were synthesized using a simple, one-step hydrothermal method. • The as-synthesized QDs were found to be nontoxic in the presence of biological cells. • The QDs were stable in biological media with identical emission profile to that in water.
Jun, Shinae; Lee, Junho; Jang, Eunjoo
2013-02-26
A highly luminescent and photostable quantum dot-silica monolith (QD-SM) substance was prepared by preliminary surface exchange of the QDs and base-catalyzed sol-gel condensation of silica. The SM was heavily doped with 6-mercaptohexanol exchanged QDs up to 12 vol % (26 wt %) without particle aggregation. Propylamine catalyst was important in maintaining the original luminescence of the QDs in the SM during sol-gel condensation. The silica layer was a good barrier against oxygen and moisture, so that the QD-SM maintained its initial luminescence after high-power UV radiation (∼1 W) for 200 h and through the 150 °C LED encapsulant curing process. Green and red light-emitting QD-SMs were applied as color-converting layers on blue LEDs, and the external quantum efficiency reached up to 89% for the green QD-SM and 63% for the red one. A white LED made with a mixture of green and red QDs in the SM, in which the color coordinate was adjusted at (0.23, 0.21) in CIE1931 color space for a backlight application, showed an efficacy of 47 lm/W, the highest value yet reported.
Xifang, Chen; Wenxia, Zhang; Qianjin, Wang; Jiyang, Fan
Carbon quantum dots (CQDs) have attracted great attention in the past few years due to their low cytotoxicity, exploited various synthesis methods, unexampled abundance of raw materials on earth, and robust near-infrared to near-UV luminescence. Carbon nanoparticles have applications in biological labeling, delivery of drugs and biological molecules into cells, and light emitting diodes and lasing. CQDs generally exist as nanodiamonds or graphite quantum dots according to previous research reports. In this study, we report the first synthesis of the third-allotrope CQDs through carbonization of sucrose and study their luminescence properties. These CQDs have a body-centered cubic structure and each lattice point is composed of eight atoms which form a sub-cube (so called C8 crystal structure). High-resolution transmission electron microscopy and X-ray diffraction confirm the C8 structure of the synthesized carbon nanocrystallites with an average size of 2 nm. The C8 CQDs exhibit double-band luminescence with two peaks centered at around 432 and 520 nm. The study based on the photoluminescence, UV-Vis absorption, Fourier-transform infrared, and X-ray photoelectron spectroscopies reveals that the green emission originates from the C=O related surface defect.
Silica coating of luminescent quantum dots prepared in aqueous media for cellular labeling
Energy Technology Data Exchange (ETDEWEB)
Ma, Yunfei; Li, Yan, E-mail: yli@ecust.edu.cn; Zhong, Xinhua, E-mail: zhongxh@ecust.edu.cn
2014-12-15
Graphical abstract: A facile route based on modified Stöber method was used for the synthesis of silica coated QDs (QD@SiO{sub 2}) starting from aqueously prepared CdTe/CdS QDs. The resultant QD@SiO{sub 2} exhibited a significant increase in emission efficiency compared with that of the initial QDs, along with a small size (∼5 nm in diameter), great stability and low cytotoxicity, which makes it a good candidate as robust biomarker. - Highlights: • We present a facile modified Stöber method to prepare highly luminescent QD@SiO{sub 2}. • The PL efficiency of QDs increases significantly after silica coating. • QD@SiO{sub 2} exhibits small size (∼5 nm) and great dispersibility in aqueous solution. • QD@SiO{sub 2} presents extraordinary photo and colloidal stability. • The silica shell eliminates QD cytotoxicity, providing the access of bioconjugation. - Abstract: Silica coating is an effective approach for rendering luminescent quantum dots (QDs) with water dispersibility and biocompatibility. However, it is still challenging to prepare silica-coated QDs (QD@SiO{sub 2}) with high emission efficiency, small size and great stability in favor for bioapplication. Herein, we reported a modified Stöber method for silica coating of aqueously-prepared CdTe/CdS QDs. With the coexistence of Cd{sup 2+} and thioglycolic acid (TGA), a thin silica shell was formed around QDs by the hydrolysis of tetraethyl orthosilicate (TEOS). The resultant QD@SiO{sub 2} with a small size (∼5 nm in diameter) exhibits significantly higher emission efficiencies than that of the initial QDs. Also, QD@SiO{sub 2} has extraordinary photo and colloidal stability (pH range of 5–13, 4.0 M NaCl solution). Protected by the silica shell, the cytotoxicity of QDs could be reduced. Moreover, the QD@SiO{sub 2} conjugated with folic acid (FA) presents high specific binding toward receptor-positive HeLa cells over receptor-negative A549 cells.
Studies on highly luminescent AgInS{sub 2} and Ag–Zn–In–S quantum dots
Energy Technology Data Exchange (ETDEWEB)
Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Xie, Cuiping; Wang, Jing; Zhong, Jiasong; Liang, Xiaojuan; Yang, Hailong; Luo, Le [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Chen, Zhaoping [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China)
2014-03-05
Highlights: • The quantum yield of the obtained ternary AgInS{sub 2} QDs was up to 62% with the emission peak of 642 nm under the excitation of 460 nm. • Colorful luminescent Ag–Zn–In–S QDs were obtained by adding Zn salts directly as well as Ag and In precursors. • The obtained highly luminescent quantum dots showed promising applications in the white light emitting diodes (W-LED). • The electroluminescence (EL) of AgInS{sub 2} QDs was observed in QD-LED device. -- Abstract: Silver indium sulfide (AIS) quantum dots (QDs) with different Ag/In molar ratios were synthesized via a hot-injection method. Intense photoluminescence (PL) originating from the donor–acceptor pair recombination were observed for all the samples and the emission peak blue-shifted from 739 to 632 nm, being similar to the behavior of the absorption onset as the Ag/In ratios decreased. The highest PL quantum yield (QY) of the obtained ternary AIS QDs was ca. 62% with an optimum ratio of Ag/In = 1/4. Compared with AIS QDs, when Zn ions were introduced, the absorption spectra of the obtained quaternary Ag–Zn–In–S QDs were blue-shifted, and their emission peaks moved to higher energies accordingly, showing a tunable emission from red to green by altering the band gap energy. In order to further study the electroluminescence (EL) as well as looking forward to the applications in the optoelectronic devices of the obtained highly luminescent nanoparticles, the colloidal AIS QDs were deposited as thin films to the sandwich-like structured QD-LED. The experimental results showed that the obtained EL device exhibited EL emission originated from QDs thin films by adjusting the turn on voltage, which is for the first time to realize EL of AIS QDs in such QD-LED.
Quantum noise, quantum measurement, and squeezing
International Nuclear Information System (INIS)
Haus, Herman A
2004-01-01
This is the edited text of the Keynote Speech that Professor Haus had been invited to give at the Conference on Fluctuations and Noise in Photonics and Quantum Optics, held at Santa Fe, NM, on 1-4 June 2003. He introduces it as partly an overview, partly a retrospective, finishing with some remarks about the future, addressing the topics as he knew them best, from his own perspective. Sadly, Professor Haus died shortly before he was due to present this speech to conference delegates. (keynote speech)
Fabrication of highly luminescent InP/Cd and InP/CdS quantum dots
International Nuclear Information System (INIS)
Park, Jaehyun; Kim, Sunghoon; Kim, Sungwoo; Yu, Seung Tack; Lee, Bunyeoul; Kim, Sang-Wook
2010-01-01
Highly luminescent InP/Cd and InP/CdS core-shell QDs were fabricated by sequential addition of cadmium acetylacetonate and dodecanethiol to InP core solutions, which showed a red-shift in absorption and emission. ICP measurement revealed the existence of cadmium and TEM images showed the increased size of InP/CdS QDs. PXRD data identified zinc blend structures of InP and InP/CdS QDs, which indexed to the (1 1 1), (2 2 0) and (3 1 1) planes. The slight shift of peaks between InP and InP/CdS QDs can demonstrate the existence of CdS shell structures.
Quantum probability measures and tomographic probability densities
Amosov, GG; Man'ko, [No Value
2004-01-01
Using a simple relation of the Dirac delta-function to generalized the theta-function, the relationship between the tomographic probability approach and the quantum probability measure approach with the description of quantum states is discussed. The quantum state tomogram expressed in terms of the
Fast and Straightforward Synthesis of Luminescent Titanium(IV Dioxide Quantum Dots
Directory of Open Access Journals (Sweden)
Václav Štengl
2017-01-01
Full Text Available The nucleus of titania was prepared by reaction of solution titanium oxosulphate with hydrazine hydrate. These titania nuclei were used for titania quantum dots synthesis by a simple and fast method. The prepared titanium(IV dioxide quantum dots were characterized by measurement of X-ray powder diffraction (XRD, X-ray photoelectron spectroscopy (XPS, atomic force microscopy (AFM, high-resolution electron microscopy (HRTEM, and selected area electron diffraction (SAED. The optical properties were determined by photoluminescence (PL spectra. The prepared titanium(IV dioxide quantum dots have the narrow range of UV excitation (365–400 nm and also a close range of emission maxima (450–500 nm.
Measurement analysis and quantum gravity
International Nuclear Information System (INIS)
Albers, Mark; Kiefer, Claus; Reginatto, Marcel
2008-01-01
We consider the question of whether consistency arguments based on measurement theory show that the gravitational field must be quantized. Motivated by the argument of Eppley and Hannah, we apply a DeWitt-type measurement analysis to a coupled system that consists of a gravitational wave interacting with a mass cube. We also review the arguments of Eppley and Hannah and of DeWitt, and investigate a second model in which a gravitational wave interacts with a quantized scalar field. We argue that one cannot conclude from the existing gedanken experiments that gravity has to be quantized. Despite the many physical arguments which speak in favor of a quantum theory of gravity, it appears that the justification for such a theory must be based on empirical tests and does not follow from logical arguments alone.
Quantum evolution by discrete measurements
International Nuclear Information System (INIS)
Roa, L; Guevara, M L Ladron de; Delgado, A; Olivares-RenterIa, G; Klimov, A B
2007-01-01
In this article we review two ways of driving a quantum system to a known pure state via a sequence discrete of von Neumann measurements. The first of them assumes that the initial state of the system is unknown, and the evolution is attained only with the help of two non-commuting observables. For this method, the overall success probability is maximized when the eigentstates of the involved observables constitute mutually unbiased bases. The second method assumes the initial state is known and it uses N observables which are consecutively measured to make the state of the system approach the target state. The probability of success of this procedure converges to 1 as the number of observables increases
Quantum evolution by discrete measurements
Energy Technology Data Exchange (ETDEWEB)
Roa, L [Center for Quantum Optics and Quantum Information, Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Guevara, M L Ladron de [Departamento de Fisica, Universidad Catolica del Norte, Casilla 1280, Antofagasta (Chile); Delgado, A [Center for Quantum Optics and Quantum Information, Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Olivares-RenterIa, G [Center for Quantum Optics and Quantum Information, Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Klimov, A B [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44420 Guadalajara, Jalisco (Mexico)
2007-10-15
In this article we review two ways of driving a quantum system to a known pure state via a sequence discrete of von Neumann measurements. The first of them assumes that the initial state of the system is unknown, and the evolution is attained only with the help of two non-commuting observables. For this method, the overall success probability is maximized when the eigentstates of the involved observables constitute mutually unbiased bases. The second method assumes the initial state is known and it uses N observables which are consecutively measured to make the state of the system approach the target state. The probability of success of this procedure converges to 1 as the number of observables increases.
High luminescent L-cysteine capped CdTe quantum dots prepared at different reaction times
Kiprotich, Sharon; Onani, Martin O.; Dejene, Francis B.
2018-04-01
This paper reports a facile synthesis route of high luminescent L-cysteine capped CdTe quantum dots (QDs). The effect of reaction time on the growth mechanism, optical and physical properties of the CdTe QDs was investigated in order to find the suitability of them towards optical and medical applications. The representative high-resolution transmission microscopy (HRTEM) analysis showed that the as-obtained CdTe QDs appeared as spherical particles with excellent monodispersity. The images exhibited clear lattice fringes which are indicative of good crystallinity. The X-ray diffraction (XRD) pattern displayed polycrystalline nature of the QDs which correspond well to zinc blende phase of bulk CdTe. The crystallite sizes calculated from the Scherrer equation were less than 10 nm for different reaction times which were in close agreement with the values estimated from HRTEM. An increase in reaction time improved crystallinity of the sample as explained by highest peak intensity of the XRD supported by the photoluminescence emission spectra which showed high intensity at a longer growth time. It was observed that for prolonged growth time the emission bands were red shifted from about 517-557 nm for 5-180 min of reaction time due to increase in particle sizes. Ultraviolet and visible analysis displayed well-resolved absorption bands which were red shifted upon an increase in reaction time. There was an inverse relation between the band gap and reaction time. Optical band gap decreases from 3.98 to 2.59 eV with the increase in reaction time from 15 to 180 min.
Measures and applications of quantum correlations
International Nuclear Information System (INIS)
Adesso, Gerardo; Bromley, Thomas R; Cianciaruso, Marco
2016-01-01
Quantum information theory is built upon the realisation that quantum resources like coherence and entanglement can be exploited for novel or enhanced ways of transmitting and manipulating information, such as quantum cryptography, teleportation, and quantum computing. We now know that there is potentially much more than entanglement behind the power of quantum information processing. There exist more general forms of non-classical correlations, stemming from fundamental principles such as the necessary disturbance induced by a local measurement, or the persistence of quantum coherence in all possible local bases. These signatures can be identified and are resilient in almost all quantum states, and have been linked to the enhanced performance of certain quantum protocols over classical ones in noisy conditions. Their presence represents, among other things, one of the most essential manifestations of quantumness in cooperative systems, from the subatomic to the macroscopic domain. In this work we give an overview of the current quest for a proper understanding and characterisation of the frontier between classical and quantum correlations (QCs) in composite states. We focus on various approaches to define and quantify general QCs, based on different yet interlinked physical perspectives, and comment on the operational significance of the ensuing measures for quantum technology tasks such as information encoding, distribution, discrimination and metrology. We then provide a broader outlook of a few applications in which quantumness beyond entanglement looks fit to play a key role. (topical review)
Increase of (CdSe/ZnS)Cys quantum dot luminescence intensity in the presence of TPPS4 porphyrin
International Nuclear Information System (INIS)
Parra, Gustavo G.; Borissevitch, Iouri E.; Oleinikov, Vladimir A.
2012-01-01
Full text: Nanocrystal semiconductor particles or Quantum Dots (QD) possess extraordinary photophysical characteristics, such as extreme high fluorescence quantum yield and optical absorption and very narrow fluorescence band, which can be easily shifted by changing of QD particle size. Due to these characteristics, QD is promising for fluorescence cancer diagnostics and photodynamic treatment. The efficiency of these processes can be in- creased by energy transfer between QD and classic fluorescence probes and photosensitizers (PS). In this work we present on the study of the increase of (CdSe/ZnS)Cys quantum dot luminescence intensity, stimulated by interaction with TPPS 4 porphyrin. The optical absorption and steady-state and time-resolved fluorescence techniques were employed. Water soluble QD (CdSe/ZnS) with emission at 580 nm, functionalized with cysteine (Cys), were studied. TPPS 4 porphyrin was used as a stimulator of QD luminescence. All experiments were realized in PBS buffer (pH 7.3; 7.5 mM) in Milli-Q quality water. The TPPS 4 adding into the QD solutions until the 5μM concentration produced an increase in QD luminescence intensity and lifetime, while for TPPS 4 concentrations higher than 20μM the reduction of the fluorescence intensity was observed, the emission spectra and fluorescence decays profile being unchanged. This effect can not be due to the electrostatic interaction between (CdSe/ZnS)Cys and TPPS 4 because both, (CdSe/ZnS)Cys and TPPS 4 , are negatively charged. We suppose that TPPS 4 porphyrin interacts directly with QD (ZnS) shell, reducing the dangling bound number. This reduction decreases, in turn, the probability of nonradiative ways of the excitation energy dissipation. When the majority of dangling bound is occupied by the TPPS 4 molecules, the effect of QD luminescence reduction (quenching) by porphyrin predominates, probably, via the energy transfer from QD to TPPS 4 . However, because of complexity in the systems involving
Thermodynamics of Weakly Measured Quantum Systems.
Alonso, Jose Joaquin; Lutz, Eric; Romito, Alessandro
2016-02-26
We consider continuously monitored quantum systems and introduce definitions of work and heat along individual quantum trajectories that are valid for coherent superposition of energy eigenstates. We use these quantities to extend the first and second laws of stochastic thermodynamics to the quantum domain. We illustrate our results with the case of a weakly measured driven two-level system and show how to distinguish between quantum work and heat contributions. We finally employ quantum feedback control to suppress detector backaction and determine the work statistics.
Fiber optical dose rate measurement based on the luminescence of beryllium oxide
Directory of Open Access Journals (Sweden)
Teichmann Tobias
2018-01-01
Full Text Available This work presents a fiber optical dose rate measurement system based on the radioluminescence and optically stimulated luminescence of beryllium oxide. The system consists of a small, radiation sensitive probe which is coupled to a light detection unit with a long and flexible light guide. Exposing the beryllium oxide probe to ionizing radiation results in the emission of light with an intensity which is proportional to the dose rate. Additionally, optically stimulated luminescence can be used to obtain dose and dose rate information during irradiation or retrospectively. The system is capable of real time dose rate measurements in fields of high dose rates and dose rate gradients and in complex, narrow geometries. This enables the application for radiation protection measurements as well as for quality control in radiotherapy. One inherent drawback of fiber optical dosimetry systems is the generation of Cherenkov radiation and luminescence in the light guide itself when it is exposed to ionizing radiation. This so called “stem” effect leads to an additional signal which introduces a deviation in the dose rate measurement and reduces the spatial resolution of the system, hence it has to be removed. The current system uses temporal discrimination of the effect for radioluminescence measurements in pulsed radiation fields and modulated optically stimulated luminescence for continuous irradiation conditions. This work gives an overview of the major results and discusses new-found obstacles of the applied methods of stem discrimination.
Invariant measures on multimode quantum Gaussian states
Lupo, C.; Mancini, S.; De Pasquale, A.; Facchi, P.; Florio, G.; Pascazio, S.
2012-12-01
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Invariant measures on multimode quantum Gaussian states
International Nuclear Information System (INIS)
Lupo, C.; Mancini, S.; De Pasquale, A.; Facchi, P.; Florio, G.; Pascazio, S.
2012-01-01
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Invariant measures on multimode quantum Gaussian states
Energy Technology Data Exchange (ETDEWEB)
Lupo, C. [School of Science and Technology, Universita di Camerino, I-62032 Camerino (Italy); Mancini, S. [School of Science and Technology, Universita di Camerino, I-62032 Camerino (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); De Pasquale, A. [NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, I-56126 Pisa (Italy); Facchi, P. [Dipartimento di Matematica and MECENAS, Universita di Bari, I-70125 Bari (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Florio, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 1, I-00184 Roma (Italy); Dipartimento di Fisica and MECENAS, Universita di Bari, I-70126 Bari (Italy); Pascazio, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Fisica and MECENAS, Universita di Bari, I-70126 Bari (Italy)
2012-12-15
We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom-the symplectic eigenvalues-which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Maxwell's demon, Szilard's engine and quantum measurements
International Nuclear Information System (INIS)
Zorek, W.H.
1986-01-01
The author proposes and analyzes a quantum version of Szilard's one-molecule engine. In particular, the author recovers, in the quantum context, Szilard's conclusion concerning the free energy ''cost'' of measurements (delta /sub F/ is greater than or equal to k/sub b/T1n2) per bit of information. A cycle of Szilard's engine is illustrated for both the original and quantum versions. The measurement of the location of the molecule is essential in the process of extracting work in both classical and quantum design. Measurements are made by the classical Maxwell's demon
From quantum measurement to biology via retrocausality.
Matsuno, Koichiro
2017-12-01
A reaction cycle in general or a metabolic cycle in particular owes its evolutionary emergence to the covering reaction environment acting as a measurement apparatus of a natural origin. The quantum measurement of the environmental origin underlying the molecular processes observed in the biological realm is operative cohesively between the measuring and the measured. The measuring part comes to pull in a quantum as an indivisible lump available from an arbitrary material body to be measured. The inevitable difference between the impinging quantum upon the receiving end on the part of the environment and the actual quantum pulled into the receiving end comes to effectively be nullified through the retrocausative propagation of the corresponding wave function proceeding backwards in time. The retrocausal regulation applied to the interface between the measuring and the measured is to function as the organizational agency supporting biology, and is sought in the act for the present in the immediate future within the realm of quantum phenomena. Molecular dynamics in biology owes both the evolutionary buildup and maintenance of its organization to the retrocausal operation of the unitary transformation applied to quantum phenomena proceeding backwards in time. Quantum measurement provides the cohesive agency that is pivotal for implementing the retrocausal regulation. In particular, the physical origin of Darwinian natural selection can be seen in the retrocausal regulation applied to the unitary transformation of a quantum origin. Copyright © 2017 Elsevier Ltd. All rights reserved.
The entropic cost of quantum generalized measurements
Mancino, Luca; Sbroscia, Marco; Roccia, Emanuele; Gianani, Ilaria; Somma, Fabrizia; Mataloni, Paolo; Paternostro, Mauro; Barbieri, Marco
2018-03-01
Landauer's principle introduces a symmetry between computational and physical processes: erasure of information, a logically irreversible operation, must be underlain by an irreversible transformation dissipating energy. Monitoring micro- and nano-systems needs to enter into the energetic balance of their control; hence, finding the ultimate limits is instrumental to the development of future thermal machines operating at the quantum level. We report on the experimental investigation of a lower bound to the irreversible entropy associated to generalized quantum measurements on a quantum bit. We adopted a quantum photonics gate to implement a device interpolating from the weakly disturbing to the fully invasive and maximally informative regime. Our experiment prompted us to introduce a bound taking into account both the classical result of the measurement and the outcoming quantum state; unlike previous investigation, our entropic bound is based uniquely on measurable quantities. Our results highlight what insights the information-theoretic approach provides on building blocks of quantum information processors.
Energy Technology Data Exchange (ETDEWEB)
Cruz G, H.S.; Michaelian, K.; Galindo U, S.; Martinez D, A.; Belmont M, E. [Instituto Nacional de Investigaciones Nucleares, Carretera Mexico- Toluca Km. 36.5, A.P. 18-1027, 11801 Mexico D.F. (Mexico)
2000-07-01
The analytical model of induced light production in scintillator materials by energetic ions proposed by Michaelian and Menchaca (M-M) adjusts very well the luminescence substance data in a wide energy interval of the incident ions (10-100 MeV). However at low energies, that is, under to 10 MeV, the experimental deviations of the predictions of M-M model, show that the causes may be certain physical effects, all they important at low energies, which were not considered. We have modified lightly the M-M model using the basic fact that the Quantum mechanics gives to a different limit for the quantum impact parameter instead of the classic approximation. (Author)
Quantum qubit measurement by a quantum point contact with a quantum Langevin equation approach
International Nuclear Information System (INIS)
Dong, Bing; Lei, X.L.; Horing, N.J.M.; Cui, H.L.
2007-01-01
We employ a microscopic quantum Heisenberg-Langevin equation approach to establish a set of quantum Bloch equations for a two-level system (coupled quantum dots) capacitively coupled to a quantum point contact (QPC). The resulting Bloch equations facilitate our analysis of qubit relaxation and decoherence in coupled quantum dots induced by measurement processes at arbitrary bias-voltage and temperature. We also examine the noise spectrum of the meter output current for a symmetric qubit. These results help resolve a recent debate about a quantum oscillation peak in the noise spectrum. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
The role of measurement in quantum games
International Nuclear Information System (INIS)
Nawaz, Ahmad; Toor, A H
2006-01-01
The game of prisoner dilemma is analysed to study the role of measurement basis in quantum games. Four different types of payoffs for quantum games are identified on the basis of different combinations of initial state and measurement basis. A relation among these different payoffs is established
'quantumness' measures in the decohering harmonic oscillator
Indian Academy of Sciences (India)
We studied the behaviour under decoherence of four different measures of the distance between quantum states and classical states for the harmonic oscillator coupled to a linear Markovian bath. Three of these are relative measures, using different definitions of the distance between the given quantum states and the set of ...
Aqueous synthesis of highly luminescent glutathione-capped Mn{sup 2+}-doped ZnS quantum dots
Energy Technology Data Exchange (ETDEWEB)
Kolmykov, Oleksii [Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, CNRS, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France); Coulon, Joël [Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l' Environnement (LCPME), UMR 7564, CNRS, Faculté de Pharmacie, 5 rue Albert Lebrun, 54000 Nancy (France); Lalevée, Jacques [Institut de Science des Matériaux de Mulhouse (IS2M), UMR 7361, CNRS, 15 rue Jean Starcky, 68093 Mulhouse (France); Alem, Halima; Medjahdi, Ghouti [Université de Lorraine, Institut Jean Lamour (IJL), UMR 7198, CNRS, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Schneider, Raphaël, E-mail: raphael.schneider@univ-lorraine.fr [Université de Lorraine, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, CNRS, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)
2014-11-01
In this paper, an aqueous-based route has been developed to prepare highly luminescent glutathione (GSH)-capped Mn-doped ZnS quantum dots (QDs). The dots obtained have an average diameter of 4.3 nm and exhibit the Mn{sup 2+}-related orange luminescence with very low surface defect density. The highest photoluminescence was observed for a Mn{sup 2+} to Zn{sup 2+} molar ratio of 3%. Consecutive overcoating of the Mn:ZnS@GSH QDs by a ZnS shell was done, and the core/shell structured QDs exhibit a PL quantum yield of 23%. Transmission electron microscopy, X-ray powder diffraction, electron spin resonance, X-ray photoelectron spectroscopy, UV–visible spectroscopy and spectrofluorometry have been used to characterize the crystal structure, the doping status, and the optical properties of the doped-QDs. Our systematic investigation shows that Mn:ZnS/ZnS@GSH QDs are highly promising fluorescent labels in biological applications.
Investigation of cross talk in single grain luminescence measurements using an EMCCD camera
International Nuclear Information System (INIS)
Gribenski, Natacha; Preusser, Frank; Greilich, Steffen; Huot, Sebastien; Mittelstraß, Dirk
2015-01-01
Highly sensitive electron multiplying charges coupled devices (EMCCD) enable the spatial detection of luminescence emissions from samples and have a high potential in single grain luminescence dating. However, the main challenge of this approach is the potential effect of cross talk, i.e. the influence of signal emitted by neighbouring grains, which will bias the information recorded from individual grains. Here, we present the first investigations into this phenomenon when performing single grain luminescence measurements of quartz grains spread over the flat surface of a sample carrier. Dose recovery tests using mixed populations show an important effect of cross talk, even when some distance is kept between grains. This issue is further investigated by focusing just on two grains and complemented by simulated experiments. Creation of an additional rejection criteria based on the brightness properties of the grains is inefficient in selecting grains unaffected by their surroundings. Therefore, the use of physical approaches or image processing algorithms to directly counteract cross talk is essential to allow routine single grain luminescence dating using EMCCD cameras. - Highlights: • We have performed single grain OSL measurements using an EMCCD detector. • Individual equivalent dose cannot be accurately recovered from a mixed dose population. • Grains are influenced by signal emitted by their neighbours during the measurements. • Simulated data confirm the strong effect of this phenomenon. • Increasing the distance between grains or applying brightness criteria are inefficient.
Laser-Excited Luminescent Tracers for Planar Concentration Measurements in Gaseous Jets
Lozano, Antonio
Tracers currently used in planar laser-induced fluorescence concentration measurements are not ideal for some experimental conditions, e.g., non-reacting turbulent gaseous flows at standard temperature and pressure. In this work, a number of chemicals have been evaluated, through consideration of their physical and photophysical properties, for use as luminescent concentration markers in turbulent gaseous flows. Two selected substances, biacetyl and acetone, have been studied in more detail. Acetone PLIF concentration images have been acquired in a non-reacting air jet, and the results have been compared to similar images obtained seeding with biacetyl. Acetone has proven to be a superior tracer when imaging fluorescence emission. Acetone has also been used as a fuel marker in hydrogen and methane diffusion flames. This single -laser technique enables simultaneous recording of the acetone and OH fluorescence emissions, as well as Mie scattering from ambient air dust particles. Acetone-sensitized, collisionally-induced biacetyl phosphorescence has been used to visualize molecular mixing in gaseous flows. Initial attempts to produce quantitative results with this method through simultaneous imaging of acetone fluorescence and collisionally-induced biacetyl emission, are described. Using laser-induced biacetyl phosphorescence imaging, a data set of cross-cut concentration images has been acquired in a nitrogen coflowing jet (Re = 5,000). The images have been statistically analyzed. Very simple models of the instantaneous concentration profile have been compared to the experimental data. Of all the tested models, a paraboloid has resulted to be the best approximation to the instantaneous 2-D profile. Finally, an experiment to study jet mixing in crossflow using acetone PLIF imaging has been designed. The flow facility has been constructed, and preliminary images obtained with a high quantum efficiency, thinned CCD detector have revealed the presence of jet structures
Parra, Gustavo G.; Ferreira, Lucimara P.; Gonçalves, Pablo J.; Sizova, Svetlana V.; Oleinikov, Vladimir A.; Morozov, Vladimir N.; Kuzmin, Vladimir A.; Borissevitch, Iouri E.
2018-02-01
Interaction between porphyrins and quantum dots (QD) via energy and/or charge transfer is usually accompanied by reduction of the QD luminescence intensity and lifetime. However, for CdSe/ZnS-Cys QD water solutions, kept at 276 K during 3 months (aged QD), the significant increase in the luminescence intensity at the addition of meso-tetrakis (p-sulfonato-phenyl) porphyrin (TPPS4) has been observed in this study. Aggregation of QD during the storage provokes reduction in the quantum yield and lifetime of their luminescence. Using steady-state and time-resolved fluorescence techniques, we demonstrated that TPPS4 stimulated disaggregation of aged CdSe/ZnS-Cys QD in aqueous solutions, increasing the quantum yield of their luminescence, which finally reached that of the fresh-prepared QD. Disaggregation takes place due to increase in electrostatic repulsion between QD at their binding with negatively charged porphyrin molecules. Binding of just four porphyrin molecules per single QD was sufficient for total QD disaggregation. The analysis of QD luminescence decay curves demonstrated that disaggregation stronger affected the luminescence related with the electron-hole annihilation in the QD shell. The obtained results demonstrate the way to repair aged QD by adding of some molecules or ions to the solutions, stimulating QD disaggregation and restoring their luminescence characteristics, which could be important for QD biomedical applications, such as bioimaging and fluorescence diagnostics. On the other hand, the disaggregation is important for QD applications in biology and medicine since it reduces the size of the particles facilitating their internalization into living cells across the cell membrane.
Continuous quantum measurement and the quantum to classical transition
International Nuclear Information System (INIS)
Bhattacharya, Tanmoy; Habib, Salman; Jacobs, Kurt
2003-01-01
While ultimately they are described by quantum mechanics, macroscopic mechanical systems are nevertheless observed to follow the trajectories predicted by classical mechanics. Hence, in the regime defining macroscopic physics, the trajectories of the correct classical motion must emerge from quantum mechanics, a process referred to as the quantum to classical transition. Extending previous work [Bhattacharya, Habib, and Jacobs, Phys. Rev. Lett. 85, 4852 (2000)], here we elucidate this transition in some detail, showing that once the measurement processes that affect all macroscopic systems are taken into account, quantum mechanics indeed predicts the emergence of classical motion. We derive inequalities that describe the parameter regime in which classical motion is obtained, and provide numerical examples. We also demonstrate two further important properties of the classical limit: first, that multiple observers all agree on the motion of an object, and second, that classical statistical inference may be used to correctly track the classical motion
Approach to measurement to quantum mechanics
International Nuclear Information System (INIS)
Sudarshan, E.C.G.; Sherry, T.N.; Gautam, S.R.
1977-10-01
An unconventional approach to the measurement problem in quantum mechanics is considered, the apparatus is treated as a classical system, belonging to the macro-world. In order to have a measurement the apparatus must interact with the quantum system. As a first step, the classical apparatus is embedded into a larger quantum mechanical structure, making use of superselection rules. Projection back to the classical system is possible. The apparatus and system are now coupled such that the apparatus remains classical (principle of integrity), and unambiguous information of the values of a quantum observable are transferred to the variables of the apparatus. Finally, projection back to the classical formulation is accomplished. Further measurement of the classical apparatus can be done, causing no problems of principle. Thus interactions causing pointers to move (which are not treat) can be added. The restrictions placed by the principle of integrity on the form of the interaction between classical and quantum systems are examined
Maxwell's Demon, Szilard's Engine and Quantum Measurements
Zurek, Wojciech Hubert
2003-01-01
We propose and analyze a quantum version of Szilard's ``one-molecule engine.'' In particular, we recover, in the quantum context, Szilard's conclusion concerning the free energy ``cost'' of measurements: $\\Delta F \\geq k_B T\\ln2$ per bit of information.
Quantum measurements of atoms using cavity QED
International Nuclear Information System (INIS)
Dada, Adetunmise C.; Andersson, Erika; Jones, Martin L.; Kendon, Vivien M.; Everitt, Mark S.
2011-01-01
Generalized quantum measurements are an important extension of projective or von Neumann measurements in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two nonstandard quantum measurements using cavity QED. The first measurement optimally and unambiguously distinguishes between two nonorthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionization detection of atoms and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurements have been realized only on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.
Dutt, Ateet; Matsumoto, Yasuhiro; Santana-Rodríguez, G; Ramos, Estrella; Monroy, B Marel; Santoyo Salazar, J
2017-01-04
The impact of the surface reconstruction of the density distribution and photoluminescence of silicon quantum dots (QDs) embedded in a silicon oxide matrix (SiO x ) has been studied. Annealing treatments carried out on the as-deposited samples provoked the effusion of hydrogen species. Moreover, depending on the surrounding density and coalescence of QDs, they resulted in a change in the average size of the particles depending on the initial local environment. The shift in the luminescence spectra all over the visible region (blue, green and red) shows a strong dependence on the resultant change in the size and/or the passivation environment of QDs. Density functional theoretical (DFT) calculations support this fact and explain the possible electronic transitions (HOMO-LUMO gap) involved. Passivation in the presence of oxygen species lowers the band gap of Si 29 and Si 35 nanoclusters up to 1.7 eV, whereas, surface passivation in the environment of hydrogen species increases the band gap up to 4.4 eV. These results show a good agreement with the quantum confinement model described in this work and explain the shift in the luminescence all over the visible region. The results reported here offer vital insight into the mechanism of emission from silicon quantum dots which has been one of the most debated topics in the last two decades. QDs with multiple size distribution in different local environments (band gap) observed in this work could be used for the fabrication of light emission diodes (LEDs) or shift-conversion thin films in third generation efficient tandem solar cells for the maximum absorption of the solar spectrum in different wavelength regions.
DEFF Research Database (Denmark)
Duller, G.A.T.; Bøtter-Jensen, L.; Kohsiek, P.
1999-01-01
An instrument has been designed for the routine analysis of the optically stimulated luminescence signal from single grains of sand. The system is capable of analysing over 3000 individual grains in a single measurement sequence, and the OSL signal from each grain can be read in less than 3 s....... The design principles are described, along with preliminary measurements that illustrate the operation of the system and its capabilities....
Inconclusive quantum measurements and decisions under uncertainty
Yukalov, Vyacheslav; Sornette, Didier
2016-04-01
We give a mathematical definition for the notion of inconclusive quantum measurements. In physics, such measurements occur at intermediate stages of a complex measurement procedure, with the final measurement result being operationally testable. Since the mathematical structure of Quantum Decision Theory has been developed in analogy with the theory of quantum measurements, the inconclusive quantum measurements correspond, in Quantum Decision Theory, to intermediate stages of decision making in the process of taking decisions under uncertainty. The general form of the quantum probability for a composite event is the sum of a utility factor, describing a rational evaluation of the considered prospect, and of an attraction factor, characterizing irrational, subconscious attitudes of the decision maker. Despite the involved irrationality, the probability of prospects can be evaluated. This is equivalent to the possibility of calculating quantum probabilities without specifying hidden variables. We formulate a general way of evaluation, based on the use of non-informative priors. As an example, we suggest the explanation of the decoy effect. Our quantitative predictions are in very good agreement with experimental data.
Inconclusive quantum measurements and decisions under uncertainty
Directory of Open Access Journals (Sweden)
Vyacheslav I. Yukalov
2016-04-01
Full Text Available We give a mathematical definition for the notion of inconclusive quantum measurements.In physics, such measurements occur at intermediate stages of a complex measurement procedure, with the final measurement result being operationally testable. Since the mathematical structure of Quantum Decision Theory has been developed in analogy withthe theory of quantum measurements, the inconclusive quantum measurements correspond,in Quantum Decision Theory, to intermediate stages of decision making in the process of taking decisions under uncertainty. The general form of the quantum probability for a composite event is the sum of a utility factor, describing a rational evaluationof the considered prospect, and of an attraction factor, characterizing irrational,subconscious attitudes of the decision maker. Despite the involved irrationality, the probability of prospects can be evaluated. This is equivalent to the possibility of calculating quantum probabilities without specifying hidden variables. We formulate a general way of evaluation, based on the use of non-informative priors. As an example,we suggest the explanation of the decoy effect. Our quantitative predictions are in very good agreement with experimental data.
Quantum system lifetimes and measurement perturbations
International Nuclear Information System (INIS)
Najakov, E.
1977-05-01
The recently proposed description of quantum system decay in terms of repeated measurement perturbations is modified. The possibility of retarded reductions to a unique quantum state, due to ineffective localization of the decay products at initial time measurements, is simply taken into account. The exponential decay law is verified again. A modified equation giving the observed lifetime in terms of unperturbed quantum decay law, measurement frequency and reduction law is derived. It predicts deviations of the observed lifetime from the umperturbed one, together with a dependence on experimental procedures. The influence of different model unperturbed decay laws and reduction laws on this effect is studied
A quantum measure of the multiverse
International Nuclear Information System (INIS)
Vilenkin, Alexander
2014-01-01
It has been recently suggested that probabilities of different events in the multiverse are given by the frequencies at which these events are encountered along the worldline of a geodesic observer (the ''watcher''). Here I discuss an extension of this probability measure to quantum theory. The proposed extension is gauge-invariant, as is the classical version of this measure. Observations of the watcher are described by a reduced density matrix, and the frequencies of events can be found using the decoherent histories formalism of Quantum Mechanics (adapted to open systems). The quantum watcher measure makes predictions in agreement with the standard Born rule of QM
A quantum measure of the multiverse
Energy Technology Data Exchange (ETDEWEB)
Vilenkin, Alexander, E-mail: vilenkin@cosmos.phy.tufts.edu [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
2014-05-01
It has been recently suggested that probabilities of different events in the multiverse are given by the frequencies at which these events are encountered along the worldline of a geodesic observer (the ''watcher''). Here I discuss an extension of this probability measure to quantum theory. The proposed extension is gauge-invariant, as is the classical version of this measure. Observations of the watcher are described by a reduced density matrix, and the frequencies of events can be found using the decoherent histories formalism of Quantum Mechanics (adapted to open systems). The quantum watcher measure makes predictions in agreement with the standard Born rule of QM.
Leon, R.; Swift, G. M.; Magness, B.; Taylor, W. A.; Tang, Y. S.; Wang, K. L.; Dowd, P.; Zhang, Y. H.
2000-01-01
The photoluminescence emission from InGaAs/GaAs quantum-well and quantum-dot (QD) structures are compared after controlled irradiation with 1.5 MeV proton fluxes. Results presented here show a significant enhancement in radiation tolerance with three-dimensional quantum confinement.
Simple and rapid measurement of α-rays on smear samples using air luminescence
International Nuclear Information System (INIS)
Takiue, M.
1980-01-01
The α-activity collected on smear samples has been measured indirectly using an air luminescence counting method and a liquid scintillation spectrometer. In this method, air luminescence, attributed to the fluorescence emitted by nitrogen molecules excited by α-rays in air, serves to detect α-rays. Thus, sample preparation and α-ray measurement are simple and rapid, and moreover, no radioactive waste solution is produced. Taking into account a low background and a counting efficiency between 10 and 20%, it is estimated that the detectable limit for α-ray measurement is about 1 x 10 -7 μCi/cm 2 for loose contamination. This method is convenient to use in the routine analysis of α-ray-emitting nuclides on smear paper. (author)
Quantum Nanomechanics: State Engineering and Measurement
International Nuclear Information System (INIS)
Woolley, M. J.; Milburn, G. J.; Doherty, A. C.
2011-01-01
There has recently been a surge of interest in the study of mechanical systems near the quantum limit. Such experiments are motivated by both fundamental interest in studying quantum mechanics with macroscopic engineered systems and potential applications as ultra-sensitive transducers, or even in quantum information processing. A particularly promising system is a microwave cavity optomechanical system, in which a nanomechanical resonator is embedded within (and capacitively coupled to) a superconducting microwave cavity. Here we discuss two schemes for the generation and measurement of quantum states of the nanomechanical resonator. A quantum squeezed state may be generated via mechanical parametric amplification, while a number state may be conditionally generated via continuous measurement and feedback control mediated by a superconducting qubit.
Quantum mechanics and the science of measurements
International Nuclear Information System (INIS)
Ramsey, N.F.
1992-01-01
The accuracies of measurements of almost all fundamental physical constants have increased by factors of about 10,000 during the past 60 years. Although some of the improvements are due to greater care, most are due to new techniques based on quantum mechanics. In popular accounts of quantum mechanics, such great emphases is placed on the Heisenberg Uncertainty Principle that it often appears that the primary effect of quantum mechanics should be to diminish measurement accuracy whereas in most cases it is the validity of quantum mechanics that makes possible the vastly improved measurement accuracies. Seven quantum features that have a profound influence on the science of measurements are: (1) Existence of discrete quantum states of energy W i . (2) Energy conservation in transitions between two states. (3) Electromagnetic radiation of frequency ν is quantized with energy hν per quantum. (4) The identity principle. (5) The Heisenberg Uncertainty Principle. (6) Addition of probability amplitudes (not probabilities) so P=vertical strokeψ 1 +ψ 2 vertical stroke 2 ≠vertical strokeψ 1 vertical stroke 2 +vertical strokeψ 2 vertical stroke 2 . (7) Wave and coherent phase phenomena. Of these seven quantum features, only the Heisenberg Uncertainty Principle limits the accuracy of measurements, and its affect is often negligibly small. The other six features make possible much more accurate measurements of quantum systems than with almost all classical systems and the identity principle provides meaning and significance to highly precise measurements with quantized systems. These effects are discussed and illustrated. (orig.)
International Nuclear Information System (INIS)
Massing, J; Kähler, C J; Cierpka, C; Kaden, D
2016-01-01
The simultaneous and non-intrusive measurement of temperature and velocity fields in flows is of great scientific and technological interest. To sample the velocity and temperature, tracer particle based approaches have been developed, where the velocity is measured using PIV or PTV and the temperature is obtained from the intensity (LIF, thermographic phosphors) or frequency (TLC) of the light emitted or reflected by the tracer particles. In this article, a measurement technique is introduced, that relates the luminescent intensity ratio of individual dual-color luminescent tracer particles to temperature. Different processing algorithms are tested on synthetic particle images and compared with respect to their accuracy in estimating the intensity ratio. Furthermore, polymer particles which are doped with the temperature sensitive dye europium (III) thenoyltrifluoroacetonate (EuTTA) and the nearly temperature insensitive reference dye perylene are characterized as valid tracers. The results show a reduction of the temperature measurement uncertainty of almost 40% (95% confidence interval) compared to previously reported luminescent particle based measurement techniques for microfluidics. (paper)
Quantum decision theory as quantum theory of measurement
International Nuclear Information System (INIS)
Yukalov, V.I.; Sornette, D.
2008-01-01
We present a general theory of quantum information processing devices, that can be applied to human decision makers, to atomic multimode registers, or to molecular high-spin registers. Our quantum decision theory is a generalization of the quantum theory of measurement, endowed with an action ring, a prospect lattice and a probability operator measure. The algebra of probability operators plays the role of the algebra of local observables. Because of the composite nature of prospects and of the entangling properties of the probability operators, quantum interference terms appear, which make actions noncommutative and the prospect probabilities nonadditive. The theory provides the basis for explaining a variety of paradoxes typical of the application of classical utility theory to real human decision making. The principal advantage of our approach is that it is formulated as a self-consistent mathematical theory, which allows us to explain not just one effect but actually all known paradoxes in human decision making. Being general, the approach can serve as a tool for characterizing quantum information processing by means of atomic, molecular, and condensed-matter systems
Colloidal CsPbBr3 Perovskite Nanocrystals: Luminescence beyond Traditional Quantum Dots.
Swarnkar, Abhishek; Chulliyil, Ramya; Ravi, Vikash Kumar; Irfanullah, Mir; Chowdhury, Arindam; Nag, Angshuman
2015-12-14
Traditional CdSe-based colloidal quantum dots (cQDs) have interesting photoluminescence (PL) properties. Herein we highlight the advantages in both ensemble and single-nanocrystal PL of colloidal CsPbBr3 nanocrystals (NCs) over the traditional cQDs. An ensemble of colloidal CsPbBr3 NCs (11 nm) exhibits ca. 90 % PL quantum yield with narrow (FWHM=86 meV) spectral width. Interestingly, the spectral width of a single-NC and an ensemble are almost identical, ruling out the problem of size-distribution in PL broadening. Eliminating this problem leads to a negligible influence of self-absorption and Förster resonance energy transfer, along with batch-to-batch reproducibility of NCs exhibiting PL peaks within ±1 nm. Also, PL peak positions do not alter with measurement temperature in the range of 25 to 100 °C. Importantly, CsPbBr3 NCs exhibit suppressed PL blinking with ca. 90 % of the individual NCs remain mostly emissive (on-time >85 %), without much influence of excitation power. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Tuning quantum measurements to control chaos.
Eastman, Jessica K; Hope, Joseph J; Carvalho, André R R
2017-03-20
Environment-induced decoherence has long been recognised as being of crucial importance in the study of chaos in quantum systems. In particular, the exact form and strength of the system-environment interaction play a major role in the quantum-to-classical transition of chaotic systems. In this work we focus on the effect of varying monitoring strategies, i.e. for a given decoherence model and a fixed environmental coupling, there is still freedom on how to monitor a quantum system. We show here that there is a region between the deep quantum regime and the classical limit where the choice of the monitoring parameter allows one to control the complex behaviour of the system, leading to either the emergence or suppression of chaos. Our work shows that this is a result from the interplay between quantum interference effects induced by the nonlinear dynamics and the effectiveness of the decoherence for different measurement schemes.
International Nuclear Information System (INIS)
Nose, Katsuhiro; Fujita, Hiroshi; Omata, Takahisa; Otsuka-Yao-Matsuo, Shinya; Nakamura, Hiroyuki; Maeda, Hideaki
2007-01-01
The role of organic amines in the colloidal synthesis of CdSe quantum dots (QDs) has been studied. CdSe QDs were synthesized from the source solutions containing 5 vol% of amines having various alkyl chain lengths, stereochemical sizes and electron donation abilities. The role of the additional amines was evaluated on the basis of the photoluminescence (PL) properties such as PL wavelength and intensity of the obtained CdSe QDs. The observed PL spectra were explained by the fact that the amines behaved as capping ligands on the surface of the QDs in the product colloidal solution and complex ligands for cadmium in the source solutions. It was shown that the particle size was controlled by the diffusion process depending on the mass and stereochemical shape of the amines, and the luminescence intensity increased with the increasing electron donation ability and capping density of the amines
Emerging interpretations of quantum mechanics and recent progress in quantum measurement
International Nuclear Information System (INIS)
Clarke, M L
2014-01-01
The focus of this paper is to provide a brief discussion on the quantum measurement process, by reviewing select examples highlighting recent progress towards its understanding. The areas explored include an outline of the measurement problem, the standard interpretation of quantum mechanics, quantum to classical transition, types of measurement (including weak and projective measurements) and newly emerging interpretations of quantum mechanics (decoherence theory, objective reality, quantum Darwinism and quantum Bayesianism). (paper)
Quantum measurement of coherent tunneling between quantum dots
International Nuclear Information System (INIS)
Wiseman, H. M.; Utami, Dian Wahyu; Sun, He Bi; Milburn, G. J.; Kane, B. E.; Dzurak, A.; Clark, R. G.
2001-01-01
We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number by coupling it to a third readout dot via the Coulomb interaction. The readout dot is coupled to source and drain leads under weak bias, and a tunnel current flows through a single bound state when energetically allowed. The occupation of the quantum dot near the readout dot shifts the bound state of the readout dot from a low conducting state to a high conducting state. The measurement is made by continuously monitoring the tunnel current through the readout dot. We show that there is a difference between the time scale for the measurement-induced decoherence between the localized states of the dots, and the time scale on which the system becomes localized due to the measurement
Influence of ionizing radiation on biogel bone implants observed by luminescence measurements
International Nuclear Information System (INIS)
Szarska, St.; Jungner, H.; Borsowska, A.
2004-01-01
The preparation of sol-gel-derived bioactive glass thin films coated on glass is described. Biogel is one of the important modern materials, which are applied in medicine to reduce disability and thus to improve the level of human life. A patient with implanted biogel (i.e. bone, tooth) may be subjected to ionizing radiation during X-ray examination or treatment of cancer. Such an irradiation can generate electron and hole traps in the insulator surface layer. Changes in the microstructure of the biogel surface resulting from irradiation were observed using luminescence methods. Results from luminescence measurements after irradiation of a set of biogel samples are discussed in terms of point defects in the glass structure
Classical field approach to quantum weak measurements.
Dressel, Justin; Bliokh, Konstantin Y; Nori, Franco
2014-03-21
By generalizing the quantum weak measurement protocol to the case of quantum fields, we show that weak measurements probe an effective classical background field that describes the average field configuration in the spacetime region between pre- and postselection boundary conditions. The classical field is itself a weak value of the corresponding quantum field operator and satisfies equations of motion that extremize an effective action. Weak measurements perturb this effective action, producing measurable changes to the classical field dynamics. As such, weakly measured effects always correspond to an effective classical field. This general result explains why these effects appear to be robust for pre- and postselected ensembles, and why they can also be measured using classical field techniques that are not weak for individual excitations of the field.
The macroscopic harmonic oscillator and quantum measurements
International Nuclear Information System (INIS)
Hayward, R.W.
1982-01-01
A quantum mechanical description of a one-dimensional macroscopic harmonic oscillator interacting with its environment is given. Quasi-coherent states are introduced to serve as convenient basis states for application of a density matrix formalism to characterize the system. Attention is given to the pertinent quantum limits to the precision of measurement of physical observables that may provide some information on the nature of a weak classical force interacting with the oscillator. A number of ''quantum nondemolition'' schemes proposed by various authors are discussed. (Auth.)
Universality of measurements on quantum markets
Pakuła, Ireneusz; Piotrowski, Edward W.; Sładkowski, Jan
2007-11-01
Two of the authors have recently discussed financial markets operated by quantum computers-quantum market games. These “new markets” cannot by themselves create opportunity of making extraordinary profits or multiplying goods, but they may cause the dynamism of transaction which would result in more effective markets and capital flow into hands of the most efficient traders. Here we focus upon the problem of universality of measurement in quantum market games offering a possible method of implementation if the necessary technologies would be available. It can be also used to analyse material commitments that elude description in orthodox game-theoretic terms.
Measurements and mathematical formalism of quantum mechanics
Slavnov, D. A.
2007-03-01
A scheme for constructing quantum mechanics is given that does not have Hilbert space and linear operators as its basic elements. Instead, a version of algebraic approach is considered. Elements of a noncommutative algebra (observables) and functionals on this algebra (elementary states) associated with results of single measurements are used as primary components of the scheme. On the one hand, it is possible to use within the scheme the formalism of the standard (Kolmogorov) probability theory, and, on the other hand, it is possible to reproduce the mathematical formalism of standard quantum mechanics, and to study the limits of its applicability. A short outline is given of the necessary material from the theory of algebras and probability theory. It is described how the mathematical scheme of the paper agrees with the theory of quantum measurements, and avoids quantum paradoxes.
International Nuclear Information System (INIS)
Boden, G.
1982-08-01
Silica glasses melted from crystalline SiO 2 were exposed to ionizing radiation. At room temperature the spatial intensity distribution of the emitted luminescent radiation has been recorded by means of photographic or autoradiographic materials. Thereby schlieren and inhomogeneities are made visible and information is obtained on the melting process of the crystalline SiO 2 . Synthetic fused silica made from SiCl 4 shows no luminescent radiation. Depending on the penetration depth of the ionizing radiation the bulk or the surface of the sample can be studied. The decay curves of the integral luminescence intensity yield data on inhomogeneities in the silica glass leading to conclusions on order state and structure. The luminescence intensity and its half-life are a measure for the inhomogeneity of the silica glass and the existence of so-called 'preordered states'. This connection between luminescence intensity and the order state is found also with other X-amorphous SiO 2 modifications: silica gel, precipitated silicic acids, porous SiO 2 glasses, aerosil, thin SiO 2 layers, mechanically activated quartz: whereas no luminescence phenomena occur in disordered nearly ideally amorphous SiO 2 species, the luminescence increases with increasing order degree of the SiO 2 network and attains a high intensity in the case of the crystalline SiO 2 modifications quartz and cristobalite
Identification of irradiated spices with luminescence measurements: a European intercomparison
Energy Technology Data Exchange (ETDEWEB)
Heide, L; Guggenberger, R; Boegl, K W [Federal Health Office, Neuherberg/Muenchen (Germany, F.R.). Inst. for Radiation Hygiene
1989-01-01
Blind tests were performed measuring the thermoluminescence intensity on samples from 10 different spices that were either irradiated or unirradiated. The chemiluminescence was measured on 10 additional spice samples. Twelve institutions participated in this collaborative study. Thresholds were defined which, when exceeded, declare samples as irradiated. The recovering rate was nearly 100% for samples investigated by thermoluminescence. Only one out of 495 irradiated samples was not identified. By using chemiluminescence, the participants succeeded in identifying 99% of unirradiated samples and 75% of irradiated samples from a total of 490 samples. (author).
Quantum theory of successive projective measurements
International Nuclear Information System (INIS)
Johansen, Lars M.
2007-01-01
We show that a quantum state may be represented as the sum of a joint probability and a complex quantum modification term. The joint probability and the modification term can both be observed in successive projective measurements. The complex modification term is a measure of measurement disturbance. A selective phase rotation is needed to obtain the imaginary part. This leads to a complex quasiprobability: The Kirkwood distribution. We show that the Kirkwood distribution contains full information about the state if the two observables are maximal and complementary. The Kirkwood distribution gives another picture of state reduction. In a nonselective measurement, the modification term vanishes. A selective measurement leads to a quantum state as a non-negative conditional probability. We demonstrate the special significance of the Schwinger basis
Measurement device-independent quantum dialogue
Maitra, Arpita
2017-12-01
Very recently, the experimental demonstration of quantum secure direct communication (QSDC) with state-of-the-art atomic quantum memory has been reported (Zhang et al. in Phys Rev Lett 118:220501, 2017). Quantum dialogue (QD) falls under QSDC where the secrete messages are communicated simultaneously between two legitimate parties. The successful experimental demonstration of QSDC opens up the possibilities for practical implementation of QD protocols. Thus, it is necessary to analyze the practical security issues of QD protocols for future implementation. Since the very first proposal for QD by Nguyen (Phys Lett A 328:6-10, 2004), a large number of variants and extensions have been presented till date. However, all of those leak half of the secret bits to the adversary through classical communications of the measurement results. In this direction, motivated by the idea of Lo et al. (Phys Rev Lett 108:130503, 2012), we propose a measurement device-independent quantum dialogue scheme which is resistant to such information leakage as well as side-channel attacks. In the proposed protocol, Alice and Bob, two legitimate parties, are allowed to prepare the states only. The states are measured by an untrusted third party who may himself behave as an adversary. We show that our protocol is secure under this adversarial model. The current protocol does not require any quantum memory, and thus, it is inherently robust against memory attacks. Such robustness might not be guaranteed in the QSDC protocol with quantum memory (Zhang et al. 2017).
Luminescence in medical image science
Energy Technology Data Exchange (ETDEWEB)
Kandarakis, I.S., E-mail: kandarakis@teiath.gr
2016-01-15
Radiation detection in Medical Imaging is mostly based on the use of luminescent materials (scintillators and phosphors) coupled to optical sensors. Materials are employed in the form of granular screens, structured (needle-like) crystals and single crystal transparent blocks. Storage phosphors are also incorporated in some x-ray imaging plates. Description of detector performance is currently based on quality metrics, such as the Luminescence efficiency, the Modulation Transfer Function (MTF), the Noise Power Spectrum (NPS) and the Detective Quantum Efficiency (DQE) can be defined and evaluated. The aforementioned metrics are experimental evaluated for various materials in the form of screens. A software was designed (MINORE v1) to present image quality measurements in a graphical user interface (GUI) environment. Luminescence efficiency, signal and noise analysis are valuable tools for the evaluation of luminescent materials as candidates for medical imaging detectors. - Highlights: • Luminescence based medical imaging detectors. • Image science: MTF, NPS, DQE. • Phosphors screens light emission efficiency experimental evaluation. • Theoretical models for estimation of phosphor screen properties. • Software for medical image quality metrics.
Measuring thermo-luminescence efficiency of TLD-2000 detectors to different energy photons
Energy Technology Data Exchange (ETDEWEB)
Xie, Wei Min; Chen, Bao Wei; Han, Yi; Yang, Zhong Jian [China Institute for Radiation Protection, Taiyuan (China)
2016-06-15
As an important detecting device, TLD is a widely used in the radiation monitoring. It is essential for us to study the property of detecting element. The aim of this study is to calculate the thermo-luminescence efficiency of TL elements. A batch of thermo-luminescence elements were irradiated by the filtered X-ray beams of average energies in the range 40-200 kVp, 662 keV {sup 137}Cs gamma rays and then the amounts of lights were measured by the TL reader. The deposition energies in elements were calculated by theory formula and Monte Carlo simulation. The unit absorbed dose in elements by photons with different energies corresponding to the amounts of lights was calculated, which is called the thermo luminescent efficiency (η(E)). Because of the amounts of lights can be calculated by the absorbed dose in elements multiply η(E), the η(E) can be calculated by the experimental data (the amounts of lights) divided by absorbed dose. The deviation of simulation results compared with theoretical calculation results were less than 5%, so the absorbed dose in elements was calculated by simulation results in here. The change range of η(E) value, relative to 662 keV {sup 137}Cs gamma rays, is about 30% in the energy range of 33 keV to 662 keV, is in accordance by the comparison with relevant foreign literatures. The η(E) values can be used for updating the amounts of lights that are got by the direct ratio assumed relations with deposition energy in TL elements, which can largely reduce the error of calculation results of the amounts of lights. These data can be used for the design of individual dosimeter which used TLD-2000 thermo-luminescence elements, also have a certain reference value for manufacturer to improve the energy-response performance of TL elements by formulation adjustment.
Macroscopic realism and quantum measurement: measurers as a natural kind
International Nuclear Information System (INIS)
Jaeger, Gregg
2014-01-01
The notion of macroscopic realism has been used in attempts to achieve consistency between physics and everyday experience and to locate some boundary between the realms of classical mechanics and quantum meachanics. Its ostensibly underlying conceptual components, realism and macroscopicity, have most often appeared in the foundations of physics in relation to quantum measurement: reality became a prominent topic of discussion in quantum physics after the notion of element of reality was defined and used by Einstein, Podolsky and Rosen in that context, and macroscopicity is often explicitly assumed to be an essential property of any measuring apparatus. However, macroscopicity turns out to be a rather vaguer and less consistently understood notion than typically assumed by physicists who have not explicitly explored the notion themselves. For this reason, it behooves those investigating the foundations of quantum mechanics from a realist perspective to look for alternative notions for grounding quantum measurement. Here, the merits of treating the measuring instrument as a ‘natural kind’ as a means of avoiding anthropocentrism in the foundations of quantum measurement are pointed out as a means of advancing quantum measurement theory. (paper)
Parametric description of the quantum measurement process
Liuzzo-Scorpo, P.; Cuccoli, A.; Verrucchi, P.
2015-08-01
We present a description of the measurement process based on the parametric representation with environmental coherent states. This representation is specifically tailored for studying quantum systems whose environment needs being considered through the quantum-to-classical crossover. Focusing upon projective measures, and exploiting the connection between large-N quantum theories and the classical limit of related ones, we manage to push our description beyond the pre-measurement step. This allows us to show that the outcome production follows from a global-symmetry breaking, entailing the observed system's state reduction, and that the statistical nature of the process is brought about, together with the Born's rule, by the macroscopic character of the measuring apparatus.
Efficient quantum computing with weak measurements
International Nuclear Information System (INIS)
Lund, A P
2011-01-01
Projective measurements with high quantum efficiency are often assumed to be required for efficient circuit-based quantum computing. We argue that this is not the case and show that the fact that they are not required was actually known previously but was not deeply explored. We examine this issue by giving an example of how to perform the quantum-ordering-finding algorithm efficiently using non-local weak measurements considering that the measurements used are of bounded weakness and some fixed but arbitrary probability of success less than unity is required. We also show that it is possible to perform the same computation with only local weak measurements, but this must necessarily introduce an exponential overhead.
Optical pumping and negative luminescence polarization in charged GaAs quantum dots
Shabaev, Andrew; Stinaff, Eric A.; Bracker, Allan S.; Gammon, Daniel; Efros, Alexander L.; Korenev, Vladimir L.; Merkulov, Igor
2009-01-01
Optical pumping of electron spins and negative photoluminescence polarization are observed when interface quantum dots in a GaAs quantum well are excited nonresonantly by circularly polarized light. Both observations can be explained by the formation of long-lived dark excitons through hole spin relaxation in the GaAs quantum well prior to exciton capture. In this model, optical pumping of resident electron spins is caused by capture of dark excitons and recombination in charged quantum dots. Negative polarization results from accumulation of dark excitons in the quantum well and is enhanced by optical pumping. The dark exciton model describes the experimental results very well, including intensity and bias dependence of the photoluminescence polarization and the Hanle effect.
Byun, Ho-June; Lee, Ju Chul; Yang, Heesun
2011-03-01
InP quantum dots (QDs) were solvothermally synthesized by using a greener phosphorus source of P(N(CH(3))(2))(3) instead of highly toxic P(TMS)(3) widely used, and subsequently subjected to a size-sorting processing. While as-grown QDs showed an undetectably low emission intensity, post-synthetic treatments such as photo-etching, photo-radiation, and photo-assisted ZnS shell coating gave rise to a substantial increase in emission efficiency due to the effective removal and passivation of surface states. The emission efficiency of the photo-etched QDs was further enhanced by a consecutive UV photo-radiation, attributable to the photo-oxidation at QD surface. Furthermore, a relatively thick ZnS shell on the surface of InP QDs that were surface-modified with hydrophilic ligands beforehand was photochemically generated in an aqueous solution at room temperature. The resulting InP/ZnS core/shell QDs, emitting from blue to red wavelengths, were more efficient than the above photo-treated InP QDs, and their luminescent properties (emission bandwidth and quantum yield) were comparable to those of InP QDs synthesized with P(TMS)(3). Structural, size, and compositional analyses on InP/ZnS QDs were also conducted to elucidate their core/shell structure. Copyright © 2010 Elsevier Inc. All rights reserved.
High-Performance CuInS _{2} Quantum Dot Laminated Glass Luminescent Solar Concentrators for Windows
Energy Technology Data Exchange (ETDEWEB)
Bergren, Matthew R. [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Makarov, Nikolay S. [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Ramasamy, Karthik [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Jackson, Aaron [UbiQD, Inc., Los Alamos, New Mexico 87544, United States; Guglielmetti, Rob [National Renewable Energy Laboratory, Golden, Colorado 80401, United States; McDaniel, Hunter [UbiQD, Inc., Los Alamos, New Mexico 87544, United States
2018-01-30
Building-integrated sunlight harvesting utilizing laminated glass luminescent solar concentrators (LSCs) is proposed. By incorporating high quantum yield (>90%), NIR-emitting CuInS2/ZnS quantum dots into the polymer interlayer between two sheets of low-iron float glass, a record optical efficiency of 8.1% is demonstrated for a 10 cm x 10 cm device that transmits ~44% visible light. After completing prototypes by attaching silicon solar cells along the perimeter of the device, the electrical power conversion efficiency was certified at 2.2% with a black background and at 2.9% using a reflective substrate. This 'drop-in' LSC solution is particularly attractive because it fits within the existing glazing industry value chain with only modest changes to typical glazing products. Performance modeling predicts >1 GWh annual electricity production for a typical urban skyscraper in most major U.S. cities, enabling significant energy cost savings and potentially 'net-zero' buildings.
Volkova, Elena K.; Yanina, Irina Yu; Genina, Elina A.; Bashkatov, Alexey N.; Konyukhova, Julia G.; Popov, Alexey P.; Speranskaya, Elena S.; Bucharskaya, Alla B.; Navolokin, Nikita A.; Goryacheva, Irina Yu.; Kochubey, Vyacheslav I.; Sukhorukov, Gleb B.; Meglinski, Igor V.; Tuchin, Valery V.
2018-02-01
Delivery and spatial localization of upconversion luminescent microparticles [Y2O3:Yb, Er] (mean size ˜1.6 μm) and quantum dots (QDs) (CuInS2/ZnS nanoparticles coated with polyethylene glycol-based amphiphilic polymer, mean size ˜20 nm) inside rat skin was studied in vivo using a multimodal optical imaging approach. The particles were embedded into the skin dermis to the depth from 300 to 500 μm through microchannels performed by fractional laser microablation. Low-frequency ultrasound was applied to enhance penetration of the particles into the skin. Visualization of the particles was revealed using a combination of luminescent spectroscopy, optical coherence tomography, confocal microscopy, and histochemical analysis. Optical clearing was used to enhance the image contrast of the luminescent signal from the particles. It was demonstrated that the penetration depth of particles depends on their size, resulting in a different detection time interval (days) of the luminescent signal from microparticles and QDs inside the rat skin in vivo. We show that luminescent signal from the upconversion microparticles and QDs was detected after the particle delivery into the rat skin in vivo during eighth and fourth days, respectively. We hypothesize that the upconversion microparticles have created a long-time depot localized in the laser-created channels, as the QDs spread over the surrounding tissues.
Liu, Fei; Jang, Min-Ho; Ha, Hyun Dong; Kim, Je-Hyung; Cho, Yong-Hoon; Seo, Tae Seok
2013-07-19
Pristine graphene quantum dots and graphene oxide quantum dots are synthesized by chemical exfoliation from the graphite nanoparticles with high uniformity in terms of shape (circle), size (less than 4 nm), and thickness (monolayer). The origin of the blue and green photoluminescence of GQDs and GOQDs is attributed to intrinsic and extrinsic energy states, respectively. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Luminescent nanocomposites of conducting polymers and in-situ grown CdS quantum dots
International Nuclear Information System (INIS)
Borriello, C.; Masala, S.; Nenna, G.; Minarini, C.; Di Luccio, T.; Bizzarro, V.; Re, M.; Pesce, E.
2010-01-01
Luminescent PVK:CdS and P3HT:CdS nanocomposites with enhanced electrooptical properties have been synthesized. The nucleation and growth of CdS nanoparticles have been obtained by the thermolysis of a single Cd and S precursor dispersed in the polymers. The size distribution and morphology of the nanoparticles have been studied by TEM analyses. Monodispersive and very small nanoparticles of diameter below 3 nm in PVK and 2 nm in P3HT, have been obtained. The application of such nanocomposites as emitting layers in OLED devices is discussed.
Parameters affecting the luminescence of nanodiamond particles:Quantum chemical calculations
Czech Academy of Sciences Publication Activity Database
Kovalenko, Alexander; Petráková, Vladimíra; Ashcheulov, Petr; Záliš, Stanislav; Nesladek, M.; Kraus, I.; Kratochvílová, Irena
2012-01-01
Roč. 209, č. 9 (2012), s. 1769-1773 ISSN 1862-6300 R&D Projects: GA TA ČR TA01011165; GA ČR(CZ) GAP304/10/1951 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40400503 Keywords : defects * luminescence * nanodiamonds * surface termination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.469, year: 2012 http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1862-6319/earlyview
Contiguity and quantum theory of measurement
Energy Technology Data Exchange (ETDEWEB)
Green, H.S. [Adelaide Univ., SA (Australia). Dept. of Mathematical Physics]|[Adelaide Univ., SA (Australia). Dept. of Physics
1995-12-31
This paper presents a comprehensive treatment of the problem of measurement in microscopic physics, consistent with the indeterministic Copenhagen interpretation of quantum mechanics and information theory. It is pointed out that there are serious difficulties in reconciling the deterministic interpretations of quantum mechanics, based on the concepts of a universal wave function or hidden variables, with the principle of contiguity. Quantum mechanics is reformulated entirely in terms of observables, represented by matrices, including the statistical matrix, and the utility of information theory is illustrated by a discussion of the EPR paradox. The principle of contiguity is satisfied by all conserved quantities. A theory of the operation of macroscopic measuring devices is given in the interaction representation, and the attenuation of the indeterminacy of a microscopic observable in the process of measurement is related to observable changes of entropy. 28 refs.
Contiguity and quantum theory of measurement
International Nuclear Information System (INIS)
Green, H.S.; Adelaide Univ., SA
1995-01-01
This paper presents a comprehensive treatment of the problem of measurement in microscopic physics, consistent with the indeterministic Copenhagen interpretation of quantum mechanics and information theory. It is pointed out that there are serious difficulties in reconciling the deterministic interpretations of quantum mechanics, based on the concepts of a universal wave function or hidden variables, with the principle of contiguity. Quantum mechanics is reformulated entirely in terms of observables, represented by matrices, including the statistical matrix, and the utility of information theory is illustrated by a discussion of the EPR paradox. The principle of contiguity is satisfied by all conserved quantities. A theory of the operation of macroscopic measuring devices is given in the interaction representation, and the attenuation of the indeterminacy of a microscopic observable in the process of measurement is related to observable changes of entropy. 28 refs
Energy Technology Data Exchange (ETDEWEB)
Qiao, Wen [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Yan, Shiming [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); College of Science, Henan University of Technology, Zhengzhou 450001 (China); Song, Xueyin; Zhang, Xing; He, Xueming [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Zhong, Wei, E-mail: wzhong@nju.edu.cn [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Du, Youwei [Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China)
2015-12-30
Graphical abstract: - Highlights: • A new preparation, multi-exfoliation method based on lithium (Li) intercalation, has been demonstrated for preparing monolayer molybdenum disulfide (MoS{sub 2}) quantum dots (QDs). • The advantage of this approach is that it is capable of producing monolayer MoS{sub 2} QDs in a large number, regardless of whether the raw material is bulk or nanoparticles. • The PL intensity excited at 300 nm can be enhanced by five times after ultrasonicated heating treatment. - Abstract: An effective multi-exfoliation method based on lithium (Li) intercalation has been demonstrated for preparing monolayer molybdenum disulfide (MoS{sub 2}) quantum dots (QDs). The cutting mechanism of MoS{sub 2} QDs may involve the complete breakup around the defects and edges during the reaction of Li{sub x}MoS{sub 2} with water and its following ultrasonication process. The multiply exfoliation make the MoS{sub 2} fragile and easier to break up. After the third exfoliation, a large number of monolayer MoS{sub 2} QDs is formed. The as-prepared MoS{sub 2} QDs show photoluminescence (PL) inactive due to the existence of 1T phase. After heating treatment, the PL intensity excited at 300 nm is enhanced by five times. The MoS{sub 2} QDs solution has an excitation-dependent luminescence emission which shifts to longer wavelengths when the excitation wavelength changes from 280 nm to 370 nm. The optical properties are explored based on the quantum confinement and edge effect.
Luminescent behavior of cadmium sulfide quantum dots for gallic acid estimation
Singh, Suman; Garg, Sourav; Chahal, Jitender; Raheja, Khushboo; Singh, Deepak; Singla, M. L.
2013-03-01
Thioglycolic acid capped cadmium sulfide (CdS/T) quantum dots have been synthesized using wet chemistry and their optical behavior has been investigated using UV-visible absorption and fluorescence spectroscopy. The role of the capping agent, sulfide source concentration, pH and temperature has been studied and discussed. Studies showed that alkaline pH leads to a decrease in the size of quantum dots and reflux temperature above 70 °C resulted in red-shift of emission spectra which is due to narrowing of the bandgap. Further, to reduce the toxicity and photochemical instability of quantum dots, the quantum dots have been functionalized with polyethylene glycol (PEG), which resulted in a 20% enhancement of the fluorescence intensity. The application potential of CdS/T-PEG quantum dots was further studied using gallic acid as a model compound. The sensing is based on fluorescence quenching of quantum dots in the presence of gallic acid, and this study showed linearity in the range from 1.3 × 10-8 to 46.5 × 10-8 mM, with a detection limit of 3.6 × 10-8 mM.
Luminescent behavior of cadmium sulfide quantum dots for gallic acid estimation
International Nuclear Information System (INIS)
Singh, Suman; Garg, Sourav; Chahal, Jitender; Raheja, Khushboo; Singla, M L; Singh, Deepak
2013-01-01
Thioglycolic acid capped cadmium sulfide (CdS/T) quantum dots have been synthesized using wet chemistry and their optical behavior has been investigated using UV–visible absorption and fluorescence spectroscopy. The role of the capping agent, sulfide source concentration, pH and temperature has been studied and discussed. Studies showed that alkaline pH leads to a decrease in the size of quantum dots and reflux temperature above 70 °C resulted in red-shift of emission spectra which is due to narrowing of the bandgap. Further, to reduce the toxicity and photochemical instability of quantum dots, the quantum dots have been functionalized with polyethylene glycol (PEG), which resulted in a 20% enhancement of the fluorescence intensity. The application potential of CdS/T-PEG quantum dots was further studied using gallic acid as a model compound. The sensing is based on fluorescence quenching of quantum dots in the presence of gallic acid, and this study showed linearity in the range from 1.3 × 10 −8 to 46.5 × 10 −8 mM, with a detection limit of 3.6 × 10 −8 mM. (paper)
Luminescence of highly excited nonpolar a-plane GaN and AlGaN/GaN multiple quantum wells
International Nuclear Information System (INIS)
Jursenas, S.; Kuokstis, E.; Miasojedovas, S.; Kurilcik, G.; Zukauskas, A.; Chen, C.Q.; Yang, J.W.; Adivarahan, V.; Asif Khan, M.
2004-01-01
Carrier recombination dynamics in polar and nonpolar GaN epilayers and GaN/AlGaN multiple quantum wells grown over sapphire substrates with a various crystallographic orientation were studied under high photoexcitation by 20 ps laser pulses. The transient luminescence featured a significant enhancement on nonradiative recombination of free carriers for nonpolar a-plane GaN epilayers compared to conventional c-plane samples. The epitaxial layer overgrowth technique was demonstrated to significantly improve the quality of nonpolar a-plane films. This was proved by more than 40-fold increase in luminescence decay time (430 ps compared to ≤ 10 ps in the ordinary a-plane epilayer). Under high-excitation regime, a complete screening of built-in electric field by free carriers in multiple quantum wells grown on c-plane and r-plane sapphire substrates was achieved. Under such high excitation, luminescence efficiency and carrier lifetime of multiple quantum wells were shown to be determined by the substrate quality. (author)
Woda, Clemens; Jacob, P; Ulanovsky, A; Fiedler, I; Mokrov, Y; Rovny, S
2009-11-01
Recently discovered historical documents indicate that large releases of noble gases (mainly (41)Ar and radioactive isotopes of Kr and Xe) from the Mayak Production Association (MPA) over the period from 1948 to 1956 may have caused considerable external exposures of both, inhabitants of Ozyorsk and former inhabitants of villages at the upper Techa River. To quantify this exposure, seven brick samples from three buildings in Ozyorsk, located 8-10 km north-northwest from the radioactive gas release points, were taken. The absorbed dose in brick was measured in a depth interval of 3-13 mm below the exposed surface of the bricks by means of the thermoluminescence (TL) and the optically stimulated luminescence (OSL) method. Generally, luminescence properties using TL were more favorable for precise dose determination than using OSL, but within their uncertainties the results from both methods agree well with each other. The absorbed dose due to natural radiation was assessed and subtracted under the assumption of the bricks to be completely dry. The weighted average of the anthropogenic dose for all samples measured by TL and OSL is 10 +/- 9 and 1 +/- 9 mGy, respectively. An upper limit for a possible anthropogenic dose in brick that would not be detected due to the measurement uncertainties is estimated at 24 mGy. This corresponds to an effective dose of about 21 mSv. A similar range of values is obtained in recently published dispersion calculations that were based on reconstructed MPA releases. It is concluded that the release of radioactive noble gases from the radiochemical and reactor plants at Mayak PA did not lead to a significant external exposure of the population of Ozyorsk. In addition, the study demonstrates the detection limit for anthropogenic doses in ca. 60-year-old bricks to be about 24 mGy, if luminescence methods are used.
Interpreting quantum coherence through a quantum measurement process
Yao, Yao; Dong, G. H.; Xiao, Xing; Li, Mo; Sun, C. P.
2017-11-01
Recently, there has been a renewed interest in the quantification of coherence or other coherencelike concepts within the framework of quantum resource theory. However, rigorously defined or not, the notion of coherence or decoherence has already been used by the community for decades since the advent of quantum theory. Intuitively, the definitions of coherence and decoherence should be two sides of the same coin. Therefore, a natural question is raised: How can the conventional decoherence processes, such as the von Neumann-Lüders (projective) measurement postulation or partially dephasing channels, fit into the bigger picture of the recently established theoretical framework? Here we show that the state collapse rules of the von Neumann or Lüders-type measurements, as special cases of genuinely incoherent operations (GIOs), are consistent with the resource theories of quantum coherence. New hierarchical measures of coherence are proposed for the Lüders-type measurement and their relationship with measurement-dependent discord is addressed. Moreover, utilizing the fixed-point theory for C* algebra, we prove that GIOs indeed represent a particular type of partially dephasing (phase-damping) channels which have a matrix representation based on the Schur product. By virtue of the Stinespring dilation theorem, the physical realizations of incoherent operations are investigated in detail and we find that GIOs in fact constitute the core of strictly incoherent operations and generally incoherent operations and the unspeakable notion of coherence induced by GIOs can be transferred to the theories of speakable coherence by the corresponding permutation or relabeling operators.
Measurement-device-independent quantum digital signatures
Puthoor, Ittoop Vergheese; Amiri, Ryan; Wallden, Petros; Curty, Marcos; Andersson, Erika
2016-08-01
Digital signatures play an important role in software distribution, modern communication, and financial transactions, where it is important to detect forgery and tampering. Signatures are a cryptographic technique for validating the authenticity and integrity of messages, software, or digital documents. The security of currently used classical schemes relies on computational assumptions. Quantum digital signatures (QDS), on the other hand, provide information-theoretic security based on the laws of quantum physics. Recent work on QDS Amiri et al., Phys. Rev. A 93, 032325 (2016);, 10.1103/PhysRevA.93.032325 Yin, Fu, and Zeng-Bing, Phys. Rev. A 93, 032316 (2016), 10.1103/PhysRevA.93.032316 shows that such schemes do not require trusted quantum channels and are unconditionally secure against general coherent attacks. However, in practical QDS, just as in quantum key distribution (QKD), the detectors can be subjected to side-channel attacks, which can make the actual implementations insecure. Motivated by the idea of measurement-device-independent quantum key distribution (MDI-QKD), we present a measurement-device-independent QDS (MDI-QDS) scheme, which is secure against all detector side-channel attacks. Based on the rapid development of practical MDI-QKD, our MDI-QDS protocol could also be experimentally implemented, since it requires a similar experimental setup.
Quantum measure of nonclassical light
International Nuclear Information System (INIS)
Kim, Ki Sik
2003-01-01
The nonclassical light and its properties are reviewed in the phase space representation. The quantitative measure of nonclassicality for a single-mode case is introduced and its physical significance is discussed in terms of the environmental effects on nonclassicality. The quantitative measure of nonclassical property is defined and used to classify the different nonclassical properties. The nonclassical measure is also extended to the multi-mode case. One of the distinctive features of multi-mode nonclassical light is entanglement, which is not possessed by a single-mode light, and the multi-mode nonclassical measure may reflect the contents of entanglement. The multi-mode nonclassical measure is calculated for the superposition through a beam spitter and compared with the single-mode nonclassical measure.
International Nuclear Information System (INIS)
Hardzei, Maryia; Artemyev, Mikhail
2012-01-01
Water-soluble ZnSe/ZnS core–shell quantum dots with ZnSe core doped by manganese ions show different luminescence response to pH changes in aqueous solutions depending on the type of solubilizing agents (thioglycolic acid, mercaptoundecanoic acid, sodium mercaptopropylsulfonate). In the case of long-chain mercaptoundecanoic acid only excitonic emission is affected by pH changes. Short-chain thioglycolic acid brings about equal excitonic/Mn emission variations with pH, while mercaptopropylsulfonate-stabilized quantum dots are insensitive to pH. The mechanism discussed here is based on the competition between different relaxation channels for excited excitons in ZnSe: excitonic radiative recombination, energy transfer to Mn ion and the photogenerated electron trapping due to the presence of protonated carboxyl group. ZnSe:Mn/ZnS quantum dots stabilized with long-chain mercaptoacids may be used as a new type of fluorescence ratiometric pH-sensor or indicator. - Highlights: ► Prepared ZnSe:Mn/ZnS quantum dots capped with different mercaptoacids in water. ► Photoluminescence intensity of ZnSe:Mn/ZnS quantum dots varied with pH. ► Character of luminescence variations depends on the sort of mercaptoacid capping. ► Competition between different excitonic relaxation channels for different caps.
Quantum measurement and entanglement of spin quantum bits in diamond
Pfaff, W.
2013-01-01
This thesis presents a set of experiments that explore the possible realisation of a macroscopic quantum network based on solid-state quantum bits. Such a quantum network would allow for studying quantum mechanics on large scales (meters, or even kilometers), and can open new possibilities for
Squeezing more from a quantum nondemolition measurement
DEFF Research Database (Denmark)
Buchler, B.C.; Lam, P.K.; Bachor, H.A.
2002-01-01
We use a stable, 5 dB, amplitude squeezed source for a quantum nondomolition (QND) experiment. The performance of our QND system is enhanced by an electro-optic feedforward loop which improve,, the signal transfer efficiency. At best, we measure a total signal transfer of 1.81 and conditional var...
Conjugation of biotin-coated luminescent quantum dots with single domain antibody-rhizavidin fusions
Directory of Open Access Journals (Sweden)
Jinny L. Liu
2016-06-01
Full Text Available Straightforward and effective methods are required for the bioconjugation of proteins to surfaces and particles. Previously we demonstrated that the fusion of a single domain antibody with the biotin binding molecule rhizavidin provided a facile method to coat biotin-modified surfaces with a highly active and oriented antibody. Here, we constructed similar single domain antibody—rhizavidin fusions as well as unfused rhizavidin with a His-tag. The unfused rhizavidin produced efficiently and its utility for assay development was demonstrated in surface plasmon resonance experiments. The single domain antibody-rhizavidin fusions were utilized to coat quantum dots that had been prepared with surface biotins. Preparation of antibody coated quantum dots by this means was found to be both easy and effective. The prepared single domain antibody-quantum dot reagent was characterized by surface plasmon resonance and applied to toxin detection in a fluoroimmunoassay sensing format.
Enhancing robustness of multiparty quantum correlations using weak measurement
International Nuclear Information System (INIS)
Singh, Uttam; Mishra, Utkarsh; Dhar, Himadri Shekhar
2014-01-01
Multipartite quantum correlations are important resources for the development of quantum information and computation protocols. However, the resourcefulness of multipartite quantum correlations in practical settings is limited by its fragility under decoherence due to environmental interactions. Though there exist protocols to protect bipartite entanglement under decoherence, the implementation of such protocols for multipartite quantum correlations has not been sufficiently explored. Here, we study the effect of local amplitude damping channel on the generalized Greenberger–Horne–Zeilinger state, and use a protocol of optimal reversal quantum weak measurement to protect the multipartite quantum correlations. We observe that the weak measurement reversal protocol enhances the robustness of multipartite quantum correlations. Further it increases the critical damping value that corresponds to entanglement sudden death. To emphasize the efficacy of the technique in protection of multipartite quantum correlation, we investigate two proximately related quantum communication tasks, namely, quantum teleportation in a one sender, many receivers setting and multiparty quantum information splitting, through a local amplitude damping channel. We observe an increase in the average fidelity of both the quantum communication tasks under the weak measurement reversal protocol. The method may prove beneficial, for combating external interactions, in other quantum information tasks using multipartite resources. - Highlights: • Extension of weak measurement reversal scheme to protect multiparty quantum correlations. • Protection of multiparty quantum correlation under local amplitude damping noise. • Enhanced fidelity of quantum teleportation in one sender and many receivers setting. • Enhanced fidelity of quantum information splitting protocol
Enhancing robustness of multiparty quantum correlations using weak measurement
Energy Technology Data Exchange (ETDEWEB)
Singh, Uttam, E-mail: uttamsingh@hri.res.in [Quantum Information and Computation Group, Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India); Mishra, Utkarsh, E-mail: utkarsh@hri.res.in [Quantum Information and Computation Group, Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India); Dhar, Himadri Shekhar, E-mail: dhar.himadri@gmail.com [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)
2014-11-15
Multipartite quantum correlations are important resources for the development of quantum information and computation protocols. However, the resourcefulness of multipartite quantum correlations in practical settings is limited by its fragility under decoherence due to environmental interactions. Though there exist protocols to protect bipartite entanglement under decoherence, the implementation of such protocols for multipartite quantum correlations has not been sufficiently explored. Here, we study the effect of local amplitude damping channel on the generalized Greenberger–Horne–Zeilinger state, and use a protocol of optimal reversal quantum weak measurement to protect the multipartite quantum correlations. We observe that the weak measurement reversal protocol enhances the robustness of multipartite quantum correlations. Further it increases the critical damping value that corresponds to entanglement sudden death. To emphasize the efficacy of the technique in protection of multipartite quantum correlation, we investigate two proximately related quantum communication tasks, namely, quantum teleportation in a one sender, many receivers setting and multiparty quantum information splitting, through a local amplitude damping channel. We observe an increase in the average fidelity of both the quantum communication tasks under the weak measurement reversal protocol. The method may prove beneficial, for combating external interactions, in other quantum information tasks using multipartite resources. - Highlights: • Extension of weak measurement reversal scheme to protect multiparty quantum correlations. • Protection of multiparty quantum correlation under local amplitude damping noise. • Enhanced fidelity of quantum teleportation in one sender and many receivers setting. • Enhanced fidelity of quantum information splitting protocol.
International Nuclear Information System (INIS)
Yoshio Takahashi; Takaumi Kimura; Yoshiharu Kato; Yoshitaka Minai
2001-01-01
Luminescence from lanthanide or actinide ion is influenced by hydration structure of the ion in aqueous solution system. In particular lifetime of the luminescence has been regarded as a measure of hydration number of the lanthanide or the actinide ion based on the studies on lifetime measurement of the ion in solid and solution system. Compared with other technique like NMR to determine the hydration number, laser induced lifetime measurement is advantageous in sensitivity and selectivity. This allows us to apply this method to determining the hydration number of lanthanide or actinide ion even at low concentration. (authors)
Work required for selective quantum measurement
Konishi, Eiji
2018-06-01
In quantum mechanics, we define the measuring system M in a selective measurement by two conditions. Firstly, when we define the measured system S as the system in which the non-selective measurement part acts, M is independent from the measured system S as a quantum system in the sense that any time-dependent process in the total system S + M is divisible into parts for S and M. Secondly, when we can separate S and M from each other without changing the unitary equivalence class of the state of S from that obtained by the partial trace of M, the eigenstate selection in the selective measurement cannot be realized. In order for such a system M to exist, we show that in one selective measurement of an observable of a quantum system S 0 of particles in S, there exists a negative entropy transfer from M to S that can be directly transformed into an amount of Helmholtz free energy of where T is the thermodynamic temperature of the system S. Equivalently, an extra amount of work, , is required to be done by the system M.
Quantum metrology foundation of units and measurements
Goebel, Ernst O
2015-01-01
The International System of Units (SI) is the world's most widely used system of measurement, used every day in commerce and science, and is the modern form of the metric system. It currently comprises the meter (m), the kilogram (kg), the second (s), the ampere (A), the kelvin (K), the candela (cd) and the mole (mol)). The system is changing though, units and unit definitions are modified through international agreements as the technology of measurement progresses, and as the precision of measurements improves. The SI is now being redefined based on constants of nature and their realization by quantum standards. Therefore, the underlying physics and technologies will receive increasing interest, and not only in the metrology community but in all fields of science. This book introduces and explains the applications of modern physics concepts to metrology, the science and the applications of measurements. A special focus is made on the use of quantum standards for the realization of the forthcoming new SI (the...
Luminescent manganese-doped CsPbCl3 perovskite quantum dots
Lin, Chun Che; Xu, Kun Yuan; Wang, Da; Meijerink, A|info:eu-repo/dai/nl/075044986
2017-01-01
Nanocrystalline cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I) form an exciting new class of semiconductor materials showing quantum confinement. The emission color can be tuned over the full visible spectral region making them promising for light‒emitting applications. Further control
Fabrication of CdSe quantum dots/permutite luminescent materials
Indian Academy of Sciences (India)
Administrator
tosuccinic acid-capped CdSe quantum dots (QDs) were prepared in aqueous solution by using SeO2 as selenium source and NaBH4 as reductant. Secondly, the commercial permutite was treated with acetic acid to induce a partial dealumnization, which can introduce a large number of intracrystal mesopores, and the.
Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping
2015-04-28
Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.
Volkova, Elena K.; Yanina, Irina Yu.; Sagaydachnaya, Elena; Konyukhova, Julia G.; Kochubey, Vyacheslav I.; Tuchin, Valery V.
2018-02-01
The spectra of luminescence of ZnCdS nanoparticles (ZnCdS NPs) were measured and analyzed in a wide temperature range: from room to human body and further to a hyperthermic temperature resulting in tissue morphology change. The results show that the signal of luminescence of ZnCdS NPs placed within the tissue is reasonably good sensitive to temperature change and accompanied by phase transitions of lipid structures of adipose tissue. It is shown that the presence of a phase transition in adipose tissue upon its heating (polymorphic transformations of lipids) leads to a nonmonotonic temperature dependence of the intensity of luminescence for the nanoparticles introduced into adipose tissue. This is due to a change in the light scattering by the tissue. The light scattering of adipose tissue greatly distorts the results of temperature measurements. The application of these nanoparticles is possible for temperature measurements in very thin or weakly scattering samples.
Cavity QED experiments, entanglement and quantum measurement
International Nuclear Information System (INIS)
Brune, M.
2001-01-01
This course is devoted to the physics of entanglement in microwave CQED (cavity quantum electrodynamics) experiments. The heart of this system is a microwave photon trap, made of superconducting mirrors, which stores a few-photon field in a small volume of space for times as long as milliseconds. This field interacts with circular Rydberg atoms injected one by one into the cavity. Section 2 is devoted to the description of the strong coupling regime in Rydberg atom CQED. The tools of the experiment are briefly presented at the beginning of this section as well as the main characteristics of the strong coupling regime. We then show in section 3 how to use the strong interaction with a single photon to perform a non-destructive detection of a single photon with a single atom as a meter. In section 4, we show that the achieved QND (quantum non-demolition) measurement process corresponds to the operation of a quantum phase gate. It allows, in principle, to prepare arbitrary atom + field entangled states. Various methods will be presented for preparing entangled states such as a two atom EPR (Einstein Podolsky Rosen) pair as well as a GHZ triplet. Entanglement involving more and more complex systems will then be investigated in section 5 where the preparation of a ''Schroedinger cat state'' of the cavity field is presented. We especially address in this last section the problem of entanglement between the system and the meter which occurs during any quantum measurement process
International Nuclear Information System (INIS)
Jarm, T.; Miklavcic, D.; Lesnicar, H.; Sersa, G.
2001-01-01
Background. The purpose of this preliminary study was to evaluate a novel luminescence-based fiber-optic sensor (OxyLite system) for the measurement of partial pressure of oxygen (pO 2 ) in tumors and for the detection of changes in pO 2 as a function of time. The new method was used simultaneously with the laser Doppler flowmetry method for the measurement of relative tissue perfusion. Materials and methods. Blood perfusion and pO 2 were measured continuously via fiber-optic sensors inserted into SA-1 tumors in anesthetized A/J mice. The changes in blood flow and oxygenation of tumors were induced by transient changes of the parameters of anesthesia and by injection of a vasoactive drug hydralazine. Results. Both optical methods used in the study successfully detected the induced changes in blood flow and pO 2 . The measurements of pO 2 were well correlated with measurements of microcirculatory blood perfusion. In the majority of pO 2 measurements, we observed an unexpected behavior of the signal during the stabilization process immediately after the insertion of the probe into tumor. This behaviour of the pO 2 signal was most probably caused by local tissue damage induced by the insertion of the probe. Conclusion. The novel luminescence-based optical oximetry can reliably detect local pO 2 changes in tumors as a function of time but some aspects of prolonged pO 2 measurement by this method require further investigation. (author)
Relativistic quantum metrology: exploiting relativity to improve quantum measurement technologies.
Ahmadi, Mehdi; Bruschi, David Edward; Sabín, Carlos; Adesso, Gerardo; Fuentes, Ivette
2014-05-22
We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects.
Quantum disentanglement and phase measurements
International Nuclear Information System (INIS)
Buzek, V.; Hillery, M.
1995-01-01
A 50:50 beam splitter disentangles a two-mode squeezed vacuum state into two single-mode squeezed vacuum states. With the proper choice of parameters these two single-mode states will be identical. If one is passed through a device which shifts its phase, then the phases of the shifted and reference (unshifted) modes can be determined by the Vogel-Schleich technique. In this way the phase difference, i.e. the phase shift, can be measured to an accuracy of 1/N, where N is the total number of photons coming into the beam splitter. An improved scheme is also proposed involving the disentanglement of a shifted two-mode squeezed vacuum state. This leads to two shifted squeezed vacuum states at the output of the beam splitter. If one of these is passed through the phase shifter, then by performing homodyne measurements on the shifted and unshifted modes the phase shift can again be determined to an accuracy of 1/N. (author) 4 figs., 14 refs
International Nuclear Information System (INIS)
Liu Yanping; Du Yanzhao; Chen Zhaoyang; Ba Weizhen; Fan Yanwei; Pan Shilie; Guo Qi
2008-01-01
The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy. The equipment is relatively simple and small in size, and has low power consumption. This device is suitable for measuring the space radiation dose and also can be used in high radiation dose condition and other dangerous radiation occasions. (authors)
Chèze, C.; Feix, F.; Lähnemann, J.; Flissikowski, T.; Kryśko, M.; Wolny, P.; Turski, H.; Skierbiszewski, C.; Brandt, O.
2018-01-01
Previously, we found that N-polar (In,Ga)N/GaN quantum wells prepared on freestanding GaN substrates by plasma-assisted molecular beam epitaxy at conventional growth temperatures of about 650 °C do not exhibit any detectable luminescence even at 10 K. In the present work, we investigate (In,Ga)N/GaN quantum wells grown on Ga- and N-polar GaN substrates at a constant temperature of 730 °C . This exceptionally high temperature results in a vanishing In incorporation for the Ga-polar sample. In contrast, quantum wells with an In content of 20% and abrupt interfaces are formed on N-polar GaN. Moreover, these quantum wells exhibit a spatially uniform green luminescence band up to room temperature, but the intensity of this band is observed to strongly quench with temperature. Temperature-dependent photoluminescence transients show that this thermal quenching is related to a high density of nonradiative Shockley-Read-Hall centers with large capture coefficients for electrons and holes.
Multiplexed measurements by time resolved spectroscopy using colloidal CdSe/ZnS quantum dots
Energy Technology Data Exchange (ETDEWEB)
Kaiser, U.; Jimenez de Aberasturi, D.; Malinowski, R.; Amin, F.; Parak, W. J.; Heimbrodt, W., E-mail: Wolfram.Heimbrodt@physik.uni-marburg.de [Department of Physics and Materials Sciences Center, Philipps-University of Marburg, Renthof 5, D-35032 Marburg (Germany)
2014-01-27
Multiplexed measurements of analytes in parallel is a topical demand in bioanalysis and bioimaging. An interesting alternative to commonly performed spectral multiplexing is lifetime multiplexing. In this Letter, we present a proof of principle of single-color lifetime multiplexing by coupling the same fluorophore to different nanoparticles. The effective lifetime of the fluorophores can be tuned by more than one order of magnitude due to resonance energy transfer from donor states. Measurements have been done on a model systems consisting of ATTO-590 dye molecules linked to either gold particles or to CdSe/ZnS core shell quantum dots. Both systems show the same luminescence spectrum of ATTO-590 dye emission in continuous wave excitation, but can be distinguished by means of time resolved measurements. The dye molecules bound to gold particles exhibit a mono-exponential decay with a lifetime of 4.5 ns, whereas the dye molecules bound to CdSe/ZnS dots show a nonexponential decay with a slow component of about 135 ns due to the energy transfer from the quantum dots. We demonstrate the fundamental possibility to determine the mixing ratio for dyes with equal luminescence spectra but very different transients. This opens up a pathway independent of the standard optical multiplexing with many different fluorophores emitting from the near ultraviolet to the near infrared spectral region.
Quantum key distribution without alternative measurements
Cabello, A
2000-01-01
Entanglement swapping between Einstein-Podolsky-Rosen (EPR) pairs can be used to generate the same sequence of random bits in two remote places. A quantum key distribution protocol based on this idea is described. The scheme exhibits the following features. (a) It does not require that Alice and Bob choose between alternative measurements, therefore improving the rate of generated bits by transmitted qubit. (b) It allows Alice and Bob to generate a key of arbitrary length using a single quantum system (three EPR pairs), instead of a long sequence of them. (c) Detecting Eve requires the comparison of fewer bits. (d) Entanglement is an essential ingredient. The scheme assumes reliable measurements of the Bell operator. (20 refs).
Boolean Approach to Dichotomic Quantum Measurement Theories
Energy Technology Data Exchange (ETDEWEB)
Nagata, K. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Nakamura, T. [Keio University, Yokohama (Japan); Batle, J. [Universitat de les Illes Balears, Balearic Islands (Spain); Abdalla, S. [King Abdulaziz University Jeddah, Jeddah (Saudi Arabia); Farouk, A. [Al-Zahra College for Women, Muscat (Egypt)
2017-02-15
Recently, a new measurement theory based on truth values was proposed by Nagata and Nakamura [Int. J. Theor. Phys. 55, 3616 (2016)], that is, a theory where the results of measurements are either 0 or 1. The standard measurement theory accepts a hidden variable model for a single Pauli observable. Hence, we can introduce a classical probability space for the measurement theory in this particular case. Additionally, we discuss in the present contribution the fact that projective measurement theories (the results of which are either +1 or −1) imply the Bell, Kochen, and Specker (BKS) paradox for a single Pauli observable. To justify our assertion, we present the BKS theorem in almost all the two-dimensional states by using a projective measurement theory. As an example, we present the BKS theorem in two-dimensions with white noise. Our discussion provides new insight into the quantum measurement problem by using this measurement theory based on the truth values.
Channel capacities versus entanglement measures in multiparty quantum states
International Nuclear Information System (INIS)
Sen, Aditi; Sen, Ujjwal
2010-01-01
For quantum states of two subsystems, highly entangled states have a higher capacity of transmitting classical as well as quantum information, and vice versa. We show that this is no more the case in general: Quantum capacities of multiaccess channels, motivated by communication in quantum networks, do not have any relation with genuine multiparty entanglement measures. Importantly, the statement is demonstrated for arbitrary multipartite entanglement measures. Along with revealing the structural richness of multiaccess channels, this gives us a tool to classify multiparty quantum states from the perspective of its usefulness in quantum networks, which cannot be visualized by any genuine multiparty entanglement measure.
A relativistic theory for continuous measurement of quantum fields
International Nuclear Information System (INIS)
Diosi, L.
1990-04-01
A formal theory for the continuous measurement of relativistic quantum fields is proposed. The corresponding scattering equations were derived. The proposed formalism reduces to known equations in the Markovian case. Two recent models for spontaneous quantum state reduction have been recovered in the framework of this theory. A possible example of the relativistic continuous measurement has been outlined in standard Quantum Electrodynamics. The continuous measurement theory possesses an alternative formulation in terms of interacting quantum and stochastic fields. (author) 23 refs
Inside Perovskites: Quantum Luminescence from Bulk Cs4PbBr6 Single Crystals
de Bastiani, Michele
2017-08-01
Zero-dimensional perovskite-related structures (0D-PRS) are a new frontier of perovskite-based materials. 0D-PRS, commonly synthesized in powder form, manifest distinctive optical properties such as strong photoluminescence (PL), narrow emission linewidth, and high exciton binding energy. These properties make 0D-PRS compelling for several types of optoelectronic applications, including phosphor screens and electroluminescent devices. However, it would not be possible to rationally design the chemistry and structure of these materials, without revealing the origins of their optical behaviour, which is contradictory to the well-studied APbX3 perovskites. In this work, we synthesize single crystals of Cs4PbBr6 0D-PRS, and investigated the origins of their unique optical and electronic properties. The crystals exhibit a PL quantum yield higher than 40%, the highest reported for perovskite-based single crystals. Time-resolved and temperature dependent PL studies, supported by DFT calculations, and structural analysis, elucidate an emissive behaviour reminiscent of a quantum confined structure rather than a typical bulk perovskite material.
A stochastic model for quantum measurement
International Nuclear Information System (INIS)
Budiyono, Agung
2013-01-01
We develop a statistical model of microscopic stochastic deviation from classical mechanics based on a stochastic process with a transition probability that is assumed to be given by an exponential distribution of infinitesimal stationary action. We apply the statistical model to stochastically modify a classical mechanical model for the measurement of physical quantities reproducing the prediction of quantum mechanics. The system+apparatus always has a definite configuration at all times, as in classical mechanics, fluctuating randomly following a continuous trajectory. On the other hand, the wavefunction and quantum mechanical Hermitian operator corresponding to the physical quantity arise formally as artificial mathematical constructs. During a single measurement, the wavefunction of the whole system+apparatus evolves according to a Schrödinger equation and the configuration of the apparatus acts as the pointer of the measurement so that there is no wavefunction collapse. We will also show that while the outcome of each single measurement event does not reveal the actual value of the physical quantity prior to measurement, its average in an ensemble of identical measurements is equal to the average of the actual value of the physical quantity prior to measurement over the distribution of the configuration of the system. (paper)
Quantum fluctuation theorems and power measurements
International Nuclear Information System (INIS)
Prasanna Venkatesh, B; Watanabe, Gentaro; Talkner, Peter
2015-01-01
Work in the paradigm of the quantum fluctuation theorems of Crooks and Jarzynski is determined by projective measurements of energy at the beginning and end of the force protocol. In analogy to classical systems, we consider an alternative definition of work given by the integral of the supplied power determined by integrating up the results of repeated measurements of the instantaneous power during the force protocol. We observe that such a definition of work, in spite of taking account of the process dependence, has different possible values and statistics from the work determined by the conventional two energy measurement approach (TEMA). In the limit of many projective measurements of power, the system’s dynamics is frozen in the power measurement basis due to the quantum Zeno effect leading to statistics only trivially dependent on the force protocol. In general the Jarzynski relation is not satisfied except for the case when the instantaneous power operator commutes with the total Hamiltonian at all times. We also consider properties of the joint statistics of power-based definition of work and TEMA work in protocols where both values are determined. This allows us to quantify their correlations. Relaxing the projective measurement condition, weak continuous measurements of power are considered within the stochastic master equation formalism. Even in this scenario the power-based work statistics is in general not able to reproduce qualitative features of the TEMA work statistics. (paper)
International Nuclear Information System (INIS)
Takeoka, Masahiro; Fujiwara, Mikio; Mizuno, Jun; Sasaki, Masahide
2004-01-01
Quantum-information theory predicts that when the transmission resource is doubled in quantum channels, the amount of information transmitted can be increased more than twice by quantum-channel coding technique, whereas the increase is at most twice in classical information theory. This remarkable feature, the superadditive quantum-coding gain, can be implemented by appropriate choices of code words and corresponding quantum decoding which requires a collective quantum measurement. Recently, an experimental demonstration was reported [M. Fujiwara et al., Phys. Rev. Lett. 90, 167906 (2003)]. The purpose of this paper is to describe our experiment in detail. Particularly, a design strategy of quantum-collective decoding in physical quantum circuits is emphasized. We also address the practical implication of the gain on communication performance by introducing the quantum-classical hybrid coding scheme. We show how the superadditive quantum-coding gain, even in a small code length, can boost the communication performance of conventional coding techniques
Quantum measurement with a positive operator-valued measure
International Nuclear Information System (INIS)
Brandt, Howard E
2003-01-01
In the quantum theory of measurement, the positive operator-valued measure (POVM) is an important concept, and its implementation can be useful. A POVM consists of a set of non-negative quantum-mechanical Hermitian operators that add up to the identity. The probability that a quantum system is in a particular state is given by the expectation value of the POVM operator corresponding to that state. Following a brief review of the mathematics and mention of the history of POVMs in quantum theory, a particular implementation of a POVM for use in the measurement of nonorthogonal photon polarization states is reviewed. The implementation consists simply of a Wollaston prism, a mirror, two beam splitters, a polarization rotator and three phototubes arranged in an interferometric configuration, and it is shown analytically that the device faithfully represents the POVM. Based on Neumark's extension theorem, the two-dimensional Hilbert space of the POVM implementation can be embedded in the three-dimensional Hilbert space of an ordinary projective-valued measure. Also, analytical expressions are given for the maximum Renyi information loss from the device to a disturbing probe, and for the error and inconclusive rates induced by the probe. Various aspects of the problem of probe optimization are elaborated
Energy Technology Data Exchange (ETDEWEB)
Rao, Yeluri Narayana; Datta, Aparna [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India); Das, Satyendra K. [Radiochemistry Division, Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700 064 (India); Saha, Abhijit, E-mail: abhijit@alpha.iuc.res.in [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India)
2016-08-15
Highlights: • Radiation chemical technique can provide a useful route for synthesis of ZnSe QDs. • Chelating nature of ethylene diamine is exploited for capping nanoparticles. • ZnSe QDs can be a suitable sensitive alternative to toxic cadmium-based system. • Cu(II) ion is probed by QDs in the presence of other physiologically relevant ions. - Abstract: Size-controlled synthesis of stable ZnSe QDs with narrow distribution in aqueous environment through conventional soft chemical method still poses a challenge. The proposed radiation assisted strategy demonstrates aqueous synthesis of stable, monodisperse and luminescent ZnSe QDs capped with chelating ethylene diamine under ambient conditions and at room temperature. Radiation chemical method facilitates in slow and in-situ release of selenium ion from sodium selenosulfate. The concentrations of precursors, such as zinc salt, selenium source, ethylene diamine and absorbed radiation (7–90 kGy) dose were optimized for obtaining good quality particles. Selective quenching of luminescence of as-synthesized quantum dots (QDs) by Cu{sup 2+} ions vis-à-vis other physiologically important cations provide evidence for use of ZnSe quantum dots as alternative to toxic Cd-based quantum dots to probe Cu{sup 2+} ions. The linear relation of ratio of loss in emission intensity as a function of concentration of Cu(II) indicates detection limit in nano-molar range.
Energy Technology Data Exchange (ETDEWEB)
Xiong, Sicheng; Zhou, Yaofeng; Huang, Xiaolin [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047 (China); Yu, Ruijin [College of Science, Northwest A& F University, Yangling, Shaanxi 712100 (China); Lai, Weihua [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047 (China); Xiong, Yonghua, E-mail: yhxiongchen@163.com [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047 (China)
2017-06-15
Herein, for the first time we report a novel direct competitive fluorescence-linked immunosorbent assay (dcFLISA) for the ultrasensitive detection of ochratoxin A (OTA) by introducing a large size polymer beads loaded with quantum dots (QBs) as carrier of competing antigen for decreasing binding affinity to antibody and enhancing the fluorescent signal intensity. When using 255 nm QBs as carrier of competing antigen, the equilibrium dissociation constant of QB based competing antigen to antibodies can be tuned to 100 times higher than that of the horseradish peroxidase (HRP) based competing antigen by controlling labeled amounts of antigen on the surface of QBs. Various parameters that influenced the sensitivity of dcFLISA were investigated and optimized. Under optimum detection parameters, the dynamic linear range of developed dcFLISA for detecting OTA was established at 0.05 pg/mL to 1.56 pg/mL with a half maximal inhibitory concentration at 0.14 ± 0.04 pg/mL (n = 5), which is three orders of magnitude lower than that of conventional HRP-based dcELISA (0.24 ng/mL). The developed FLISA is also highly accurate, reliable, and shows no cross reaction to other mycotoxins. In summary, the proposed method offers a straightforward approach to improve the sensitivity of direct competitive immunoassay for trace small chemical molecule detection in food quality control, environmental monitoring, and clinical diagnosis. - Highlights: • Highly luminescent QBs were used as a carrier of competing antigen for ultrasensitive detection of OTA. • It is the first time to use a large size QBs as a carrier for tuning affinity of competing antigen to antibodies. • IC{sub 50} value of QB-based dcFLISA is three orders of magnitude lower than that of HRP-based dcELISA.
International Nuclear Information System (INIS)
Xiong, Sicheng; Zhou, Yaofeng; Huang, Xiaolin; Yu, Ruijin; Lai, Weihua; Xiong, Yonghua
2017-01-01
Herein, for the first time we report a novel direct competitive fluorescence-linked immunosorbent assay (dcFLISA) for the ultrasensitive detection of ochratoxin A (OTA) by introducing a large size polymer beads loaded with quantum dots (QBs) as carrier of competing antigen for decreasing binding affinity to antibody and enhancing the fluorescent signal intensity. When using 255 nm QBs as carrier of competing antigen, the equilibrium dissociation constant of QB based competing antigen to antibodies can be tuned to 100 times higher than that of the horseradish peroxidase (HRP) based competing antigen by controlling labeled amounts of antigen on the surface of QBs. Various parameters that influenced the sensitivity of dcFLISA were investigated and optimized. Under optimum detection parameters, the dynamic linear range of developed dcFLISA for detecting OTA was established at 0.05 pg/mL to 1.56 pg/mL with a half maximal inhibitory concentration at 0.14 ± 0.04 pg/mL (n = 5), which is three orders of magnitude lower than that of conventional HRP-based dcELISA (0.24 ng/mL). The developed FLISA is also highly accurate, reliable, and shows no cross reaction to other mycotoxins. In summary, the proposed method offers a straightforward approach to improve the sensitivity of direct competitive immunoassay for trace small chemical molecule detection in food quality control, environmental monitoring, and clinical diagnosis. - Highlights: • Highly luminescent QBs were used as a carrier of competing antigen for ultrasensitive detection of OTA. • It is the first time to use a large size QBs as a carrier for tuning affinity of competing antigen to antibodies. • IC_5_0 value of QB-based dcFLISA is three orders of magnitude lower than that of HRP-based dcELISA.
Mermut, O.; Bouchard, J.-P.; Cormier, J.-F.; Desroches, P.; Diamond, K. R.; Fortin, M.; Gallant, P.; Leclair, S.; Marois, J.-S.; Noiseux, I.; Morin, J.-F.; Patterson, M. S.; Vernon, M.
2008-02-01
The development of multimodal molecular probes and photosensitizing agents for use in photodynamic therapy (PDT) is vital for optimizing and monitoring cytotoxic responses. We propose a combinatorial approach utilizing photosensitizing molecules that are both paramagnetic and luminescent with multimodal functionality to perturb, control, and monitor molecular-scale reaction pathways in PDT. To this end, a time-domain single photon counting lifetime apparatus with a 400 nm excitation source has been developed and integrated with a variable low field magnet (0- 350mT). The luminescence lifetime decay function was measured in the presence of a sweeping magnetic field for a custom designed photosensitizing molecule in which photoinduced electron transfer was studied The photosensitizer studied was a donor-acceptor complex synthesized using a porphyrin linked to a fullerene molecule. The magneto-optic properties were investigated for the free-base photosensitizer complex as well as those containing either diamagnetic (paired electron) or paramagnetic (unpaired electron) metal centers, Zn(II) and Cu(II). The magnetic field was employed to affect and modify the spin states of radical pairs of the photosensitizing agents via magnetically induced hyperfine and Zeeman effects. Since the Type 1 reaction pathway of an excited triplet state photosensitizer involves the production of radical species, lifetime measurements were conducted at low dissolved oxygen concentration (0.01ppm) to elucidate the dependence of the magnetic perturbation on the photosensitization mechanistic pathway. To optimize the magnetic response, a solvent study was performed examining the dependence of the emission properties on the magnetic field in solutions of varying dielectric constants. Lastly, the cytotoxicity in murine tumor cell suspensions was investigated for the novel porphyrin-fullerene complex by inducing photodynamic treatments and determining the associated cell survival.
Physical approaches to tuning the luminescence color patterns of colloidal quantum dots
International Nuclear Information System (INIS)
Hu Lian; Wu Huizhen; Wan Zhengfen; Cai Chunfeng; Xu Tianning; Lou Tenggang; Zhang Bingpo
2012-01-01
Localized surface plasmon resonance (LSPR) and photoactivation (PA) effects are combined for the tuning of fluorescent colors of colloidal CdSe quantum dots (QDs). It is found that LSPR with QD emitters intensely enhances surface state emission, accompanied by a remarkable red-shift of fluorescent colors, while PA treatment with colloidal QDs leads to a distinct enhancement of band-edge emission, accompanied by a peak blue-shift. Furthermore, the LSPR effect on QD emitters can be continuously tuned by the PA process. The combination of the post-synthetic approaches allows feasible realization of multi-color patterns from one batch of QDs and the approaches can also be compatible with other micro-fabrication technologies of QD embossed fluorescent patterns, which undoubtedly provides a way of precisely tuning the colors of light-emitting materials and devices that use colloidal QDs. (paper)
Gold Doping of Silver Nanoclusters: A 26-Fold Enhancement in the Luminescence Quantum Yield
Soldan, Giada
2016-04-10
A high quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for a wide range of applications. Unfortunately, the weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility. Herein, we accomplished a ≥26-fold PL QY enhancement of the Ag29(BDT)12(TPP)4 cluster (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) by doping with a discrete number of Au atoms, producing Ag29-xAux(BDT)12(TPP)4, x=1-5. The Au-doped clusters exhibit an enhanced stability and an intense red emission around 660nm. Single-crystal XRD, mass spectrometry, optical, and NMR spectroscopy shed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.
Luminescence spectra of CdSe/ZnSe double layers of quantum dots
Energy Technology Data Exchange (ETDEWEB)
Reznitsky, Alexander; Permogorov, Sergei; Korenev, Vladimir V.; Sedova, Irina; Sorokin, Sergey; Sitnikova, Alla; Ivanov, Sergei [A.F. Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Klochikhin, Albert [B.P. Konstantinov Nuclear Physics Institute, St. Petersburg (Russian Federation)
2009-12-15
We have studied the emission spectra and structural properties of double CdSe/ZnSe quantum dot (QD) sheet structures grown by molecular beam epitaxy in order to elucidate the mechanisms of the electronic and strain field interaction between the QD planes. The thickness of the ZnSe barrier separating the CdSe sheets was in the range of 10-60 monolayers (ML) in the set of samples studied. We have found that coupling between dots in adjacent layers becomes relatively strong in CdSe/ZnSe double layers structures with 25-27 ML barrier, while it is rather weak when the barrier thickness exceeds 30 ML. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Energy Technology Data Exchange (ETDEWEB)
Zhang, Lei, E-mail: mejswu@ust.hk; Chen, Haibin, E-mail: mejswu@ust.hk, E-mail: mejswu@ust.hk; Wu, Jingshen, E-mail: mejswu@ust.hk, E-mail: mejswu@ust.hk [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong and Fok Ying Tung Graduate School, The Hong Kong University of Science and Technology (Hong Kong); Bi, Xianghong, E-mail: takubatch@gmail.com [Fok Ying Tung Graduate School, The Hong Kong University of Science and Technology (Hong Kong)
2014-05-15
Without precursor preparation, inert gas protection and enormous amount of additives and reductants, CdTe quantum dots (QDs) can be rapidly synthesized with high quality. A 600 nm photoluminescence peak wavelength could be obtained within 1 hour's refluxing through minimal addition of 1,2-diaminoethane (DAE). The theoretical design for the experiments are illustrated and further proved by the characterization results with different concentrations and reagents. On the other hand, generation of CdTe QDs was found even under room temperature by applying droplet quantity of DAE. This indicates that QDs can be synthesized with simply a bottle and no enormous additives required. The QDs were mixed into the epoxy matrix through solution casting method with cetyltrimethylammonium (CTA) capping for phase transfer. The acquired epoxy based nanocomposite exhibits good transparency, compatibility and fluorescence.
Process tomography via sequential measurements on a single quantum system
CSIR Research Space (South Africa)
Bassa, H
2015-09-01
Full Text Available The authors utilize a discrete (sequential) measurement protocol to investigate quantum process tomography of a single two-level quantum system, with an unknown initial state, undergoing Rabi oscillations. The ignorance of the dynamical parameters...
Energy Technology Data Exchange (ETDEWEB)
Parra, Gustavo G.; Borissevitch, Iouri E. [Universidade de Sao Paulo (FFCLRP/USP), Ribeirao Preto, SP (Brazil). Fac. de Filosofia, Ciencias e Letras de Ribeirao Preto. Dept. de Fisica; Kuzmin, Vladimir A. [Emanuel Institute of Biophysical Chemistry, RAS-RU, Moscow (Russian Federation); Oleinikov, Vladimir A. [Shemyakin and Ovchinnikov Institute of Biooganic Cemistry, RAS-RU, Moscow (Russian Federation)
2012-07-01
Full text: Nanocrystal semiconductor particles or Quantum Dots (QD) possess extraordinary photophysical characteristics, such as extreme high fluorescence quantum yield and optical absorption and very narrow fluorescence band, which can be easily shifted by changing of QD particle size. Due to these characteristics, QD is promising for fluorescence cancer diagnostics and photodynamic treatment. The efficiency of these processes can be in- creased by energy transfer between QD and classic fluorescence probes and photosensitizers (PS). In this work we present on the study of the increase of (CdSe/ZnS)Cys quantum dot luminescence intensity, stimulated by interaction with TPPS{sub 4} porphyrin. The optical absorption and steady-state and time-resolved fluorescence techniques were employed. Water soluble QD (CdSe/ZnS) with emission at 580 nm, functionalized with cysteine (Cys), were studied. TPPS{sub 4} porphyrin was used as a stimulator of QD luminescence. All experiments were realized in PBS buffer (pH 7.3; 7.5 mM) in Milli-Q quality water. The TPPS{sub 4} adding into the QD solutions until the 5{mu}M concentration produced an increase in QD luminescence intensity and lifetime, while for TPPS{sub 4} concentrations higher than 20{mu}M the reduction of the fluorescence intensity was observed, the emission spectra and fluorescence decays profile being unchanged. This effect can not be due to the electrostatic interaction between (CdSe/ZnS)Cys and TPPS{sub 4} because both, (CdSe/ZnS)Cys and TPPS{sub 4}, are negatively charged. We suppose that TPPS{sub 4} porphyrin interacts directly with QD (ZnS) shell, reducing the dangling bound number. This reduction decreases, in turn, the probability of nonradiative ways of the excitation energy dissipation. When the majority of dangling bound is occupied by the TPPS{sub 4} molecules, the effect of QD luminescence reduction (quenching) by porphyrin predominates, probably, via the energy transfer from QD to TPPS{sub 4}. However
Quantum Backaction Evading Measurement of Collective Mechanical Modes.
Ockeloen-Korppi, C F; Damskägg, E; Pirkkalainen, J-M; Clerk, A A; Woolley, M J; Sillanpää, M A
2016-09-30
The standard quantum limit constrains the precision of an oscillator position measurement. It arises from a balance between the imprecision and the quantum backaction of the measurement. However, a measurement of only a single quadrature of the oscillator can evade the backaction and be made with arbitrary precision. Here we demonstrate quantum backaction evading measurements of a collective quadrature of two mechanical oscillators, both coupled to a common microwave cavity. The work allows for quantum state tomography of two mechanical oscillators, and provides a foundation for macroscopic mechanical entanglement and force sensing beyond conventional quantum limits.
Cui, Ping
The thesis comprises two major themes of quantum statistical dynamics. One is the development of quantum dissipation theory (QDT). It covers the establishment of some basic relations of quantum statistical dynamics, the construction of several nonequivalent complete second-order formulations, and the development of exact QDT. Another is related to the applications of quantum statistical dynamics to a variety of research fields. In particular, unconventional but novel theories of the electron transfer in Debye solvents, quantum transport, and quantum measurement are developed on the basis of QDT formulations. The thesis is organized as follows. In Chapter 1, we present some background knowledge in relation to the aforementioned two themes of this thesis. The key quantity in QDT is the reduced density operator rho(t) ≡ trBrho T(t); i.e., the partial trace of the total system and bath composite rhoT(t) over the bath degrees of freedom. QDT governs the evolution of reduced density operator, where the effects of bath are treated in a quantum statistical manner. In principle, the reduced density operator contains all dynamics information of interest. However, the conventional quantum transport theory is formulated in terms of nonequilibrium Green's function. The newly emerging field of quantum measurement in relation to quantum information and quantum computing does exploit a sort of QDT formalism. Besides the background of the relevant theoretical development, some representative experiments on molecular nanojunctions are also briefly discussed. In chapter 2, we outline some basic (including new) relations that highlight several important issues on QDT. The content includes the background of nonequilibrium quantum statistical mechanics, the general description of the total composite Hamiltonian with stochastic system-bath interaction, a novel parameterization scheme for bath correlation functions, a newly developed exact theory of driven Brownian oscillator (DBO
Huang, Xin; Jiang, Chunyan; Du, Chunhua; Jing, Liang; Liu, Mengmeng; Hu, Weiguo; Wang, Zhong Lin
2016-12-27
With a promising prospect of light-emitting diodes as an attractive alternative to conventional light sources, remaining challenges still cannot be addressed owing to their limited efficiency. Among the continued scientific efforts, significant improvement on the emission efficiency has been achieved via either piezo-phototronic effect-based strain modulation or resonant excitation of plasmons in metallic nanostructures. Here, we present the investigation on the coupling process between piezo-phototronic effect and localized surface plasmonic resonance for enhancing the photoluminescence of InGaN/GaN quantum wells coated with Ag nanoparticles. The underlying physical mechanism of experimental results originates from tuning plasmonic resonance controlled by the shift of emission wavelength via piezo-phototronic effect, and it is further confirmed with the support of theoretical calculations. As a result, our research provides an approach to the integration of plasmonics with piezo-phototronic effect and brings widespread applications to high-efficiency artificial lighting, on-chip integrated plasmonic circuits, subwavelength optical communication, and micro-optoelectronic mechanical systems.
Classical and nonclassical randomness in quantum measurements
International Nuclear Information System (INIS)
Farenick, Douglas; Plosker, Sarah; Smith, Jerrod
2011-01-01
The space POVM H (X) of positive operator-valued probability measures on the Borel sets of a compact (or even locally compact) Hausdorff space X with values in B(H), the algebra of linear operators acting on a d-dimensional Hilbert space H, is studied from the perspectives of classical and nonclassical convexity through a transform Γ that associates any positive operator-valued measure ν with a certain completely positive linear map Γ(ν) of the homogeneous C*-algebra C(X) x B(H) into B(H). This association is achieved by using an operator-valued integral in which nonclassical random variables (that is, operator-valued functions) are integrated with respect to positive operator-valued measures and which has the feature that the integral of a random quantum effect is itself a quantum effect. A left inverse Ω for Γ yields an integral representation, along the lines of the classical Riesz representation theorem for linear functionals on C(X), of certain (but not all) unital completely positive linear maps φ:C(X) x B(H)→B(H). The extremal and C*-extremal points of POVM H (X) are determined.
Measurement-only topological quantum computation via anyonic interferometry
International Nuclear Information System (INIS)
Bonderson, Parsa; Freedman, Michael; Nayak, Chetan
2009-01-01
We describe measurement-only topological quantum computation using both projective and interferometrical measurement of topological charge. We demonstrate how anyonic teleportation can be achieved using 'forced measurement' protocols for both types of measurement. Using this, it is shown how topological charge measurements can be used to generate the braiding transformations used in topological quantum computation, and hence that the physical transportation of computational anyons is unnecessary. We give a detailed discussion of the anyonics for implementation of topological quantum computation (particularly, using the measurement-only approach) in fractional quantum Hall systems
Abraham, Sara A; Kearfott, Kimberlee J; Jawad, Ali H; Boria, Andrew J; Buth, Tobias J; Dawson, Alexander S; Eng, Sheldon C; Frank, Samuel J; Green, Crystal A; Jacobs, Mitchell L; Liu, Kevin; Miklos, Joseph A; Nguyen, Hien; Rafique, Muhammad; Rucinski, Blake D; Smith, Travis; Tan, Yanliang
2017-03-01
Optically-stimulated luminescent dosimeters are capable of being interrogated multiple times post-irradiation. Each interrogation removes a fraction of the signal stored within the optically-stimulated luminescent dosimeter. This signal loss must be corrected to avoid systematic errors in estimating the average signal of a series of optically-stimulated luminescent dosimeter interrogations and requires a minimum number of consecutive readings to determine an average signal that is within a desired accuracy of the true signal with a desired statistical confidence. This paper establishes a technical basis for determining the required number of readings for a particular application of these dosimeters when using certain OSL dosimetry systems.
Mordvinova, Natalia; Vinokurov, Alexander; Kuznetsova, Tatiana; Lebedev, Oleg I; Dorofeev, Sergey
2017-01-24
Here we report a simple method for the creation of highly luminescent core-shell InP/ZnX (X = S, Se) quantum dots (QDs) on the basis of a phosphine synthetic route. In this method a Zn precursor was added to the reaction mixture at the beginning of the synthesis to form an In(Zn)P alloy structure, which promoted the formation of a ZnX shell. Core-shell InP/ZnX QDs exhibit highly intensive emission with a quantum yield over 50%. The proposed method is primarily important for practical applications. Advantages of this method compared to the widely used SILAR technique are discussed. We further demonstrate that the SILAR approach consisting of consequent addition of Zn and chalcogen precursors to pre-prepared non-doped InP colloidal nanoparticles is not quite suitable for shell growth without the addition of special activator agents or the use of very reactive precursors.
Optically stimulated luminescence from quartz measured using the linear modulation technique
DEFF Research Database (Denmark)
Bulur, E.; Bøtter-Jensen, L.; Murray, A.S.
2000-01-01
The optically stimulated luminescence (OSL) from heated natural quartz has been investigated using the linear modulation technique (LMT), in which the excitation light intensity is increased linearly during stimulation. In contrast to conventional stimulation, which usually produces a monotonical...
A conceptual analysis of quantum zeno; paradox, measurement, and experiment
International Nuclear Information System (INIS)
Home, D.; Whitaker, M.A.
1997-01-01
Arguments on controversial points concerning quantum measurement theory and the quantum Zeno effect are presented. In particular it is argued that (1) the quantum Zeno effect is a genuine result of quantum theory and current quantum measurement theory, independent of the projection postulate; (2) the effect is of very general nature and rests on analogous arguments to those involved in Bell close-quote s theories; (3) the term open-quotes quantum Zeno effectclose quotes may usefully be restricted to experiments where a measuring device exerts a nonlocal negative-result effect on a microscopic system, mere inhibition of a transition by a directly interacting device not qualifying; (4) since no decay is truly exponential, theoretically all decay phenomena should exhibit the quantum Zeno effect under observation, continuous or discrete. A detailed study is made of the experiments claiming to demonstrate the effect; it is found that they do not meet our criterion above. copyright 1997 Academic Press, Inc
The issue of phases in quantum measurement theory
International Nuclear Information System (INIS)
Pati, Arun Kumar
1999-01-01
The issue of phases is always very subtle in quantum world and many of the curious phenomena are due to the existence of the phase of the quantum mechanical wave function. We investigate the issue of phases in quantum measurement theory and predict a new effect of fundamental importance. We call a quantum system under goes a quantum Zeno dynamics when the unitary evolution of a quantum system is interrupted by a sequence of measurements. In particular, we investigate the effect of repeated measurements on the geometric phase and show that the quantum Zeno dynamics can inhibit its development under a large number of measurement pulses. It is interesting to see that neither the total phase nor the dynamical phase goes to zero under large number of measurements. This new effect we call as the 'quantum Zeno Phase effect' in analogous to the quantum Zeno effect where the repeated measurements inhibit the transition probability. This 'quantum Zeno Phase effect' can be proved within von Neumann's collapse mechanism as well as using a continuous measurement model. So the effect is really independent of any particular measurement model considered. Since the geometric phase attributes a memory to a quantum system our results also proves that the path dependent memory of a system can be erased by a sequence of measurements. The quantum Zeno Phase effect provides a way to control and manipulate the phase of a wave function in an interference set up. Finally, we stress that the quantum Zeno Phase effect can be tested using neutron, photon and atom interference experiments with the presently available technology. (Author)
CMOS direct time interval measurement of long-lived luminescence lifetimes.
Yao, Lei; Yung, Ka Yi; Cheung, Maurice C; Chodavarapu, Vamsy P; Bright, Frank V
2011-01-01
We describe a Complementary Metal-Oxide Semiconductor (CMOS) Direct Time Interval Measurement (DTIM) Integrated Circuit (IC) to detect the decay (fall) time of the luminescence emission when analyte-sensitive luminophores are excited with an optical pulse. The CMOS DTIM IC includes 14 × 14 phototransistor array, transimpedance amplifier, regulated gain amplifier, fall time detector, and time-to-digital convertor. We examined the DTIM system to measure the emission lifetime of oxygen-sensitive luminophores tris(4,7-diphenyl-1, 10-phenanthroline) ruthenium(II) ([Ru(dpp)(3)](2+)) encapsulated in sol-gel derived xerogel thin-films. The DTIM system fabricated using TSMC 0.35 μm process functions to detect lifetimes from 4 μs to 14.4 μs but can be tuned to detect longer lifetimes. The system provides 8-bit digital output proportional to lifetimes and consumes 4.5 mW of power with 3.3 V DC supply. The CMOS system provides a useful platform for the development of reliable, robust, and miniaturized optical chemical sensors.
Effective Fault-Tolerant Quantum Computation with Slow Measurements
International Nuclear Information System (INIS)
DiVincenzo, David P.; Aliferis, Panos
2007-01-01
How important is fast measurement for fault-tolerant quantum computation? Using a combination of existing and new ideas, we argue that measurement times as long as even 1000 gate times or more have a very minimal effect on the quantum accuracy threshold. This shows that slow measurement, which appears to be unavoidable in many implementations of quantum computing, poses no essential obstacle to scalability
Measurement of quantum noise in a single-electron transistor near the quantum limit
Xue, W. W.; Ji, Z.; Pan, Feng; Stettenheim, Joel; Blencowe, M. P.; Rimberg, A. J.
2009-09-01
Quantum measurement has challenged physicists for almost a century. Classically, there is no lower bound on the noise a measurement may add. Quantum mechanically, however, measuring a system necessarily perturbs it. When applied to electrical amplifiers, this means that improved sensitivity requires increased backaction that itself contributes noise. The result is a strict quantum limit on added amplifier noise. To approach this limit, a quantum-limited amplifier must possess an ideal balance between sensitivity and backaction; furthermore, its noise must dominate that of subsequent classical amplifiers. Here, we report the first complete and quantitative measurement of the quantum noise of a superconducting single-electron transistor (S-SET) near a double Cooper-pair resonance predicted to have the right combination of sensitivity and backaction. A simultaneous measurement of our S-SET's charge sensitivity indicates that it operates within a factor of 3.6 of the quantum limit, a fourfold improvement over the nearest comparable results.
Dynamics of quantum measurements employing two Curie-Weiss apparatuses
Perarnau-Llobet, Martí; Nieuwenhuizen, Theodorus Maria
2017-10-01
Two types of quantum measurements, measuring the spins of an entangled pair and attempting to measure a spin at either of two positions, are analysed dynamically by apparatuses of the Curie-Weiss type. The outcomes comply with the standard postulates. This article is part of the themed issue `Second quantum revolution: foundational questions'.
Konstantinova, E.; Zyubin, A.; Moiseeva, E.; Matveeva, K.; Slezhkin, V.; Samusev, I.; Bryukhanov, V.
2017-12-01
The study of the luminescence of CdZnSeS / ZnS quantum dots (QDs) absorbed on the rough surface of a silver film, including the energy transfer between human serum albumin molecules, isolated from the blood plasma of healthy and infected with sepsis patients, was performed by spectral-kinetic methods.
Luminescent Measurement Systems for the Investigation of a Scramjet Inlet-Isolator
Directory of Open Access Journals (Sweden)
Azam Che Idris
2014-04-01
Full Text Available Scramjets have become a main focus of study for many researchers, due to their application as propulsive devices in hypersonic flight. This entails a detailed understanding of the fluid mechanics involved to be able to design and operate these engines with maximum efficiency even at their off-design conditions. It is the objective of the present cold-flow investigation to study and analyse experimentally the mechanics of the fluid structures encountered within a generic scramjet inlet at M = 5. Traditionally, researchers have to rely on stream-thrust analysis, which requires the complex setup of a mass flow meter, a force balance and a heat transducer in order to measure inlet-isolator performance. Alternatively, the pitot rake could be positioned at inlet-isolator exit plane, but this method is intrusive to the flow, and the number of pitot tubes is limited by the model size constraint. Thus, this urgent need for a better flow diagnostics method is addressed in this paper. Pressure-sensitive paint (PSP has been applied to investigate the flow characteristics on the compression ramp, isolator surface and isolator sidewall. Numerous shock-shock interactions, corner and shoulder separation regions, as well as shock trains were captured by the luminescent system. The performance of the scramjet inlet-isolator has been shown to improve when operated in a modest angle of attack.
Blind topological measurement-based quantum computation.
Morimae, Tomoyuki; Fujii, Keisuke
2012-01-01
Blind quantum computation is a novel secure quantum-computing protocol that enables Alice, who does not have sufficient quantum technology at her disposal, to delegate her quantum computation to Bob, who has a fully fledged quantum computer, in such a way that Bob cannot learn anything about Alice's input, output and algorithm. A recent proof-of-principle experiment demonstrating blind quantum computation in an optical system has raised new challenges regarding the scalability of blind quantum computation in realistic noisy conditions. Here we show that fault-tolerant blind quantum computation is possible in a topologically protected manner using the Raussendorf-Harrington-Goyal scheme. The error threshold of our scheme is 4.3 × 10(-3), which is comparable to that (7.5 × 10(-3)) of non-blind topological quantum computation. As the error per gate of the order 10(-3) was already achieved in some experimental systems, our result implies that secure cloud quantum computation is within reach.
Coherence and measurement in quantum thermodynamics.
Kammerlander, P; Anders, J
2016-02-26
Thermodynamics is a highly successful macroscopic theory widely used across the natural sciences and for the construction of everyday devices, from car engines to solar cells. With thermodynamics predating quantum theory, research now aims to uncover the thermodynamic laws that govern finite size systems which may in addition host quantum effects. Recent theoretical breakthroughs include the characterisation of the efficiency of quantum thermal engines, the extension of classical non-equilibrium fluctuation theorems to the quantum regime and a new thermodynamic resource theory has led to the discovery of a set of second laws for finite size systems. These results have substantially advanced our understanding of nanoscale thermodynamics, however putting a finger on what is genuinely quantum in quantum thermodynamics has remained a challenge. Here we identify information processing tasks, the so-called projections, that can only be formulated within the framework of quantum mechanics. We show that the physical realisation of such projections can come with a non-trivial thermodynamic work only for quantum states with coherences. This contrasts with information erasure, first investigated by Landauer, for which a thermodynamic work cost applies for classical and quantum erasure alike. Repercussions on quantum work fluctuation relations and thermodynamic single-shot approaches are also discussed.
Measurement Uncertainty for Finite Quantum Observables
Directory of Open Access Journals (Sweden)
René Schwonnek
2016-06-01
Full Text Available Measurement uncertainty relations are lower bounds on the errors of any approximate joint measurement of two or more quantum observables. The aim of this paper is to provide methods to compute optimal bounds of this type. The basic method is semidefinite programming, which we apply to arbitrary finite collections of projective observables on a finite dimensional Hilbert space. The quantification of errors is based on an arbitrary cost function, which assigns a penalty to getting result x rather than y, for any pair ( x , y . This induces a notion of optimal transport cost for a pair of probability distributions, and we include an Appendix with a short summary of optimal transport theory as needed in our context. There are then different ways to form an overall figure of merit from the comparison of distributions. We consider three, which are related to different physical testing scenarios. The most thorough test compares the transport distances between the marginals of a joint measurement and the reference observables for every input state. Less demanding is a test just on the states for which a “true value” is known in the sense that the reference observable yields a definite outcome. Finally, we can measure a deviation as a single expectation value by comparing the two observables on the two parts of a maximally-entangled state. All three error quantities have the property that they vanish if and only if the tested observable is equal to the reference. The theory is illustrated with some characteristic examples.
Measures of Quantum Synchronization in Continuous Variable Systems
Mari, A.; Farace, A.; Didier, N.; Giovannetti, V.; Fazio, R.
2013-09-01
We introduce and characterize two different measures which quantify the level of synchronization of coupled continuous variable quantum systems. The two measures allow us to extend to the quantum domain the notions of complete and phase synchronization. The Heisenberg principle sets a universal bound to complete synchronization. The measure of phase synchronization is, in principle, unbounded; however, in the absence of quantum resources (e.g., squeezing) the synchronization level is bounded below a certain threshold. We elucidate some interesting connections between entanglement and synchronization and, finally, discuss an application based on quantum optomechanical systems.
Projective measurements in quantum and classical optical systems
CSIR Research Space (South Africa)
Roux, FS
2014-09-01
Full Text Available equally well to both classical and quantum optical systems. A projective measurement, in the context of quantum mechanics, is understood to be the process where a projection operator operates on some input state. Often this projection operator is composed...) Projective measurements in quantum and classical optical systems Filippus S. Roux* and Yingwen Zhang CSIR National Laser Centre, P.O. Box 395, Pretoria 0001, South Africa (Received 3 July 2014; published 22 September 2014) Experimental setups for the optical...
International Nuclear Information System (INIS)
Lin, Huiyun; Chen, Defu; Wang, Min; Lin, Juqiang; Li, Buhong; Xie, Shusen
2011-01-01
Direct measurement of near-infrared (NIR) luminescence around 1270 nm is the golden standard of singlet oxygen ( 1 O 2 ) identification. In this study, the influence of pulse-height discrimination threshold on measurement accuracy of the 1 O 2 luminescence that is generated from the photoirradiation of meso-tetra (N-methyl-4-pyridyl) morphine tetra-tosylate (TMPyP) in aqueous solution was investigated by using our custom-developed detection system. Our results indicate that the discrimination threshold has a significant influence on the absolute 1 O 2 luminescence counts, and the optimal threshold for our detection system is found to be about − 41.2 mV for signal discrimination. After optimization, the derived triplet-state and 1 O 2 lifetimes of TMPyP in aqueous solution are found to be 1.73 ± 0.03 and 3.70 ± 0.04 µs, respectively, and the accuracy of measurement was further independently demonstrated using the laser flash photolysis technique
Chen, Yameng; Zhou, Yang; Zhao, Qing; Zhang, Junying; Ma, Ju-Ping; Xuan, Tong-Tong; Guo, Shao-Qiang; Yong, Zi-Jun; Wang, Jing; Kuroiwa, Yoshihiro; Moriyoshi, Chikako; Sun, Hong-Tao
2018-04-18
All-inorganic perovskites have emerged as a new class of phosphor materials owing to their outstanding optical properties. Zero-dimensional inorganic perovskites, in particular the Cs4PbBr6-related systems, are inspiring intensive research owing to the high photoluminescence quantum yield (PLQY) and good stability. However, synthesizing such perovskites with high PLQYs through an enviromentally friendly, cost-effective, scalable, and high-yield approach remains challenging, and their luminescence mechanisms has been elusive. Here, we report a simple, scalable, room-temperature self-assembly strategy for the synthesis of Cs4PbBr6/CsPbBr3 perovskite composites with near-unity PLQY (95%), high product yield (71%) and good stability, using low-cost, low-toxicity chemicals as precursors. A broad range of experimental and theoretical characterizations suggest that the high-efficiency PL originates from CsPbBr3 nanocrystals well passivated by the zero-dimensional Cs4PbBr6 matrix that forms based on a dissolution-crystallization process. These findings underscore the importance in accurately identifying the phase purity of zero-dimensional perovskites by synchrotron X-ray technique to gain deep insights into the structure-property relationship. Additionally, we demonstrate that green-emitting Cs4PbBr6/CsPbBr3, combined with red-emitting K2SiF6:Mn4+, can be used for the construction of WLEDs. Our work may pave the way for the use of such composite perovskites as highly luminescent emitters in various applications such as lighting, displays, and other optoelectronic and photonic devices.
Quantum measurements without Schroedinger cat states
International Nuclear Information System (INIS)
Spehner, D; Haake, F
2007-01-01
We report and give an alternative derivation of some results on a model for a quantum measurement studied in [1]. The measured microscopic system is coupled to the position of a macroscopic pointer, which itself interacts with its environment via its momentum. The entanglement between the system and the pointer produced by their mutual interaction is simultaneous with the decoherence of distinct pointer readings resulting from leakage of information to the environment. After a discussion on the various time scales in the model we calculate the matrix elements of the system-pointer density operator between eigenstates of the measured observable with distinct eigenvalues. In general, the decay with time of these coherences is neither exponential nor gaussian. We determine the decoherence (decay) time in terms of the strength of the system-pointer and pointer-environment couplings. This decoherence time does not depend upon the details of the pointer-bath coupling as soon as it is smaller than the bath correlation time (non-Markov regime). In contrast, in the Markov regime it depends strongly on whether this coupling is Ohmic or super-Ohmic
Quantum measurements without Schroedinger cat states
Energy Technology Data Exchange (ETDEWEB)
Spehner, D [Institut Fourier, 100 rue des Maths, 38402 Saint-Martin d' Heres (France); Haake, F [Fachbereich Physik, Universitaet Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg (Germany)
2007-10-15
We report and give an alternative derivation of some results on a model for a quantum measurement studied in [1]. The measured microscopic system is coupled to the position of a macroscopic pointer, which itself interacts with its environment via its momentum. The entanglement between the system and the pointer produced by their mutual interaction is simultaneous with the decoherence of distinct pointer readings resulting from leakage of information to the environment. After a discussion on the various time scales in the model we calculate the matrix elements of the system-pointer density operator between eigenstates of the measured observable with distinct eigenvalues. In general, the decay with time of these coherences is neither exponential nor gaussian. We determine the decoherence (decay) time in terms of the strength of the system-pointer and pointer-environment couplings. This decoherence time does not depend upon the details of the pointer-bath coupling as soon as it is smaller than the bath correlation time (non-Markov regime). In contrast, in the Markov regime it depends strongly on whether this coupling is Ohmic or super-Ohmic.
Quantum probabilities of composite events in quantum measurements with multimode states
International Nuclear Information System (INIS)
Yukalov, V I; Sornette, D
2013-01-01
The problem of defining quantum probabilities of composite events is considered. This problem is of great importance for the theory of quantum measurements and for quantum decision theory, which is a part of measurement theory. We show that the Lüders probability of consecutive measurements is a transition probability between two quantum states and that this probability cannot be treated as a quantum extension of the classical conditional probability. The Wigner distribution is shown to be a weighted transition probability that cannot be accepted as a quantum extension of the classical joint probability. We suggest the definition of quantum joint probabilities by introducing composite events in multichannel measurements. The notion of measurements under uncertainty is defined. We demonstrate that the necessary condition for mode interference is the entanglement of the composite prospect together with the entanglement of the composite statistical state. As an illustration, we consider an example of a quantum game. Special attention is paid to the application of the approach to systems with multimode states, such as atoms, molecules, quantum dots, or trapped Bose-condensed atoms with several coherent modes. (paper)
A symmetric geometric measure and the dynamics of quantum discord
International Nuclear Information System (INIS)
Jiang Feng-Jian; Shi Ming-Jun; Lü Hai-Jiang; Yan Xin-Hu
2013-01-01
A symmetric measure of quantum correlation based on the Hilbert—Schmidt distance is presented in this paper. For two-qubit states, we considerably simplify the optimization procedure so that numerical evaluation can be performed efficiently. Analytical expressions for the quantum correlation are attained for some special states. We further investigate the dynamics of quantum correlation of the system qubits in the presence of independent dissipative environments. Several nontrivial aspects are demonstrated. We find that the quantum correlation can increase even if the system state is suffering from dissipative noise. Sudden changes occur, even twice, in the time evolution of quantum correlation. There exists a certain correspondence between the evolution of quantum correlation in the systems and that in the environments, and the quantum correlation in the systems will be transferred into the environments completely and asymptotically. (general)
Quantum reversibility is relative, or does a quantum measurement reset initial conditions?
Zurek, Wojciech H
2018-07-13
I compare the role of the information in classical and quantum dynamics by examining the relation between information flows in measurements and the ability of observers to reverse evolutions. I show that in the Newtonian dynamics reversibility is unaffected by the observer's retention of the information about the measurement outcome. By contrast-even though quantum dynamics is unitary, hence, reversible-reversing quantum evolution that led to a measurement becomes, in principle, impossible for an observer who keeps the record of its outcome. Thus, quantum irreversibility can result from the information gain rather than just its loss-rather than just an increase of the (von Neumann) entropy. Recording of the outcome of the measurement resets, in effect, initial conditions within the observer's (branch of) the Universe. Nevertheless, I also show that the observer's friend-an agent who knows what measurement was successfully carried out and can confirm that the observer knows the outcome but resists his curiosity and does not find out the result-can, in principle, undo the measurement. This relativity of quantum reversibility sheds new light on the origin of the arrow of time and elucidates the role of information in classical and quantum physics. Quantum discord appears as a natural measure of the extent to which dissemination of information about the outcome affects the ability to reverse the measurement.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'. © 2018 The Author(s).
Kemerink, M.; Gerritsen, J.W.; Koenraad, P.M.; Kempen, van H.; Wolter, J.H.
1999-01-01
Spectrally resolved scanning tunneling microscope-induced luminescence has been obtained under ambient conditions, i.e., at room temperature, in air, by passivating the sample surface with sulfur. This passivation turned out to be essential to suppress the local anodic oxidation induced by the
Theory of “Weak Value" and Quantum Mechanical Measurements
Shikano, Yutaka
2012-01-01
Comment: to be published from "Measurements in Quantum Mechanics", edited by M. R. Pahlavani (InTech, 2012) Chapter 4 page 75. Yutaka Shikano (2012). ISBN: 978-953-51-0058-4 Available from: http://www.intechopen.com/articles/show/title/theory-of-weak-value-and-quantum-mechanical-measurement
Toward quantum-limited position measurements using optically levitated microspheres
International Nuclear Information System (INIS)
Libbrecht, Kenneth G.; Black, Eric D.
2004-01-01
We propose the use of optically levitated microspheres as test masses in experiments aimed at reaching and potentially exceeding the standard quantum limit for position measurements. Optically levitated microspheres have low mass and are essentially free of suspension thermal noise, making them well suited for experimentally testing our understanding of quantum-limited measurements
Toward quantum-limited position measurements using optically levitated microspheres
Energy Technology Data Exchange (ETDEWEB)
Libbrecht, Kenneth G.; Black, Eric D
2004-01-26
We propose the use of optically levitated microspheres as test masses in experiments aimed at reaching and potentially exceeding the standard quantum limit for position measurements. Optically levitated microspheres have low mass and are essentially free of suspension thermal noise, making them well suited for experimentally testing our understanding of quantum-limited measurements.
Increasing lanthanide luminescence by use of the RETEL effect.
Leif, Robert C; Vallarino, Lidia M; Becker, Margie C; Yang, Sean
2006-08-01
Luminescent lanthanide complexes produce emissions with the narrowest-known width at half maximum; however, their significant use in cytometry required an increase in luminescence intensity. The companion review, Leif et al., Cytometry 2006;69A:767-778, described a new technique for the enhancement of lanthanide luminescence, the Resonance Energy Transfer Enhanced Luminescence (RETEL) effect, which increases luminescence and is compatible with standard slide microscopy. The luminescence of the europium ion macrocyclic complex, EuMac, was increased by employing the RETEL effect. After adding the nonluminescent gadolinium ion complex of the thenoyltrifluoroacetonate (TTFA) ligand or the sodium salt of TTFA in ethanol solution, the EuMac-labeled sample was allowed to dry. Both a conventional arc lamp and a time-gated UV LED served as light sources for microscopic imaging. The emission intensity was measured with a CCD camera. Multiple time-gated images were summed with special software to permit analysis and effective presentation of the final image. With the RETEL effect, the luminescence of the EuMac-streptavidin conjugate increased at least six-fold upon drying. Nuclei of apoptotic cells were stained with DAPI and tailed with 5BrdUrd to which a EuMac-anti-5BrdU conjugate was subsequently attached. Time-gated images showed the long-lived EuMac luminescence but did not show the short-lived DAPI fluorescence. Imaging of DNA-synthesizing cells with an arc lamp showed that both S phase and apoptotic cells were labeled, and that their labeling patterns were different. The images of the luminescent EuMac and fluorescent DAPI were combined to produce a color image on a white background. This combination of simple chemistry, instrumentation, and presentation should make possible the inexpensive use of the lanthanide macrocycles, Quantum Dyes, as molecular diagnostics for cytological and histopathological microscopic imaging. (c) 2006 International Society for Analytical
Demonstration of measurement-only blind quantum computing
International Nuclear Information System (INIS)
Greganti, Chiara; Roehsner, Marie-Christine; Barz, Stefanie; Walther, Philip; Morimae, Tomoyuki
2016-01-01
Blind quantum computing allows for secure cloud networks of quasi-classical clients and a fully fledged quantum server. Recently, a new protocol has been proposed, which requires a client to perform only measurements. We demonstrate a proof-of-principle implementation of this measurement-only blind quantum computing, exploiting a photonic setup to generate four-qubit cluster states for computation and verification. Feasible technological requirements for the client and the device-independent blindness make this scheme very applicable for future secure quantum networks. (paper)
Demonstration of measurement-only blind quantum computing
Greganti, Chiara; Roehsner, Marie-Christine; Barz, Stefanie; Morimae, Tomoyuki; Walther, Philip
2016-01-01
Blind quantum computing allows for secure cloud networks of quasi-classical clients and a fully fledged quantum server. Recently, a new protocol has been proposed, which requires a client to perform only measurements. We demonstrate a proof-of-principle implementation of this measurement-only blind quantum computing, exploiting a photonic setup to generate four-qubit cluster states for computation and verification. Feasible technological requirements for the client and the device-independent blindness make this scheme very applicable for future secure quantum networks.
Laser-induced incandescence of suspended particles as a source of excitation of dye luminescence
Zelensky, S
2003-01-01
The interaction of pulsed YAG-Nd sup 3 sup + laser radiation with submicron light-absorbing particles suspended in an aqueous solution of Rhodamine 6G is investigated experimentally. The experiments demonstrate that the laser-induced incandescence of suspended particles excites the luminescence of the dissolved dye molecules. The mechanism of the luminescence excitation consists in the reabsorption of the thermal radiation within the volume of the sample cell. On the ground of this mechanism of excitation, a method of measurement of the luminescence quantum yield is proposed and realized. The method requires the knowledge of the geometrical parameters of the cell and does not require the use of reference samples.
Bohmian mechanics, open quantum systems and continuous measurements
Nassar, Antonio B
2017-01-01
This book shows how Bohmian mechanics overcomes the need for a measurement postulate involving wave function collapse. The measuring process plays a very important role in quantum mechanics. It has been widely analyzed within the Copenhagen approach through the Born and von Neumann postulates, with later extension due to Lüders. In contrast, much less effort has been invested in the measurement theory within the Bohmian mechanics framework. The continuous measurement (sharp and fuzzy, or strong and weak) problem is considered here in this framework. The authors begin by generalizing the so-called Mensky approach, which is based on restricted path integral through quantum corridors. The measuring system is then considered to be an open quantum system following a stochastic Schrödinger equation. Quantum stochastic trajectories (in the Bohmian sense) and their role in basic quantum processes are discussed in detail. The decoherence process is thereby described in terms of classical trajectories issuing from th...
Measurement-only topological quantum computation without forced measurements
International Nuclear Information System (INIS)
Zheng, Huaixiu; Dua, Arpit; Jiang, Liang
2016-01-01
We investigate the measurement-only topological quantum computation (MOTQC) approach proposed by Bonderson et al (2008 Phys. Rev. Lett. 101 010501) where the braiding operation is shown to be equivalent to a series of topological charge ‘forced measurements’ of anyons. In a forced measurement, the charge measurement is forced to yield the desired outcome (e.g. charge 0) via repeatedly measuring charges in different bases. This is a probabilistic process with a certain success probability for each trial. In practice, the number of measurements needed will vary from run to run. We show that such an uncertainty associated with forced measurements can be removed by simulating the braiding operation using a fixed number of three measurements supplemented by a correction operator. Furthermore, we demonstrate that in practice we can avoid applying the correction operator in hardware by implementing it in software. Our findings greatly simplify the MOTQC proposal and only require the capability of performing charge measurements to implement topologically protected transformations generated by braiding exchanges without physically moving anyons. (paper)
International Nuclear Information System (INIS)
Bishnoi, Swati; Gupta, Vinay; Sharma, Gauri D.; Chand, Suresh; Sharma, Chhavi; Kumar, Mahesh; Haranath, D.; Naqvi, Sheerin
2016-01-01
In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO_4:Sm"3"+) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO_4:Sm"3"+ QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO_4:Sm"3"+ to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO_4:Sm"3"+ QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO_4:Sm"3"+:PC_7_1BM ([6,6]-phenyl-C_7_1-butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO_4:Sm"3"+:PC_7_1BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC_7_1BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.
Tran, Phan T.; Goldman, Ellen R.; Mattoussi, Hedi M.; Anderson, George P.; Mauro, J. Matthew
2001-06-01
Colloidal semiconductor quantum dots (QDs) seem suitable for labeling certain biomolecules for use in fluorescent tagging applications, such as fluoro-immunoassays. Compared to organic dye labels, Qds are resistant to photo-degradation, and these luminescent nanoparticles have size-dependent emission spectra spanning a wide range of wavelengths in the visible and near IR. We previously described an electrostatic self-assembly approach for conjugating highly luminescent colloidal CdSe-ZnS core-shell Qds with engineered two-domain recombinant proteins. Here we describe the application of this approach to prepare QD conjugates with the (Beta) 2 immunoglobin G (IgG) binding domain of streptococcal protein G (PG) appended with a basic lucine zipper attachment domain (PG-zb). We also demonstrate that the QD/PG conjugates retain their ability to bind IgG antibodies, and that a specific antibody coupled to QD via the PG functional domain efficiently binds its antigen. These preliminary results indicate that electrostatically self-assembled QD/PG-zb/IgG bioconjugates can be used in fluoro-immunoassays.
Weak Measurement and Quantum Smoothing of a Superconducting Qubit
Tan, Dian
In quantum mechanics, the measurement outcome of an observable in a quantum system is intrinsically random, yielding a probability distribution. The state of the quantum system can be described by a density matrix rho(t), which depends on the information accumulated until time t, and represents our knowledge about the system. The density matrix rho(t) gives probabilities for the outcomes of measurements at time t. Further probing of the quantum system allows us to refine our prediction in hindsight. In this thesis, we experimentally examine a quantum smoothing theory in a superconducting qubit by introducing an auxiliary matrix E(t) which is conditioned on information obtained from time t to a final time T. With the complete information before and after time t, the pair of matrices [rho(t), E(t)] can be used to make smoothed predictions for the measurement outcome at time t. We apply the quantum smoothing theory in the case of continuous weak measurement unveiling the retrodicted quantum trajectories and weak values. In the case of strong projective measurement, while the density matrix rho(t) with only diagonal elements in a given basis |n〉 may be treated as a classical mixture, we demonstrate a failure of this classical mixture description in determining the smoothed probabilities for the measurement outcome at time t with both diagonal rho(t) and diagonal E(t). We study the correlations between quantum states and weak measurement signals and examine aspects of the time symmetry of continuous quantum measurement. We also extend our study of quantum smoothing theory to the case of resonance fluorescence of a superconducting qubit with homodyne measurement and observe some interesting effects such as the modification of the excited state probabilities, weak values, and evolution of the predicted and retrodicted trajectories.
Towards minimal resources of measurement-based quantum computation
International Nuclear Information System (INIS)
Perdrix, Simon
2007-01-01
We improve the upper bound on the minimal resources required for measurement-only quantum computation (M A Nielsen 2003 Phys. Rev. A 308 96-100; D W Leung 2004 Int. J. Quantum Inform. 2 33; S Perdrix 2005 Int. J. Quantum Inform. 3 219-23). Minimizing the resources required for this model is a key issue for experimental realization of a quantum computer based on projective measurements. This new upper bound also allows one to reply in the negative to the open question presented by Perdrix (2004 Proc. Quantum Communication Measurement and Computing) about the existence of a trade-off between observable and ancillary qubits in measurement-only QC
Einstein-Podolsky-Rosen paradox and measurement of quantum system
Kladko, Konstantin
1999-01-01
Einstein-Podolsky-Rosen (EPR) paradox is considered in a relation to a measurement of an arbitrary quantum system . It is shown that the EPR paradox always appears in a gedanken experiment with two successively joined measuring devices.
Effect of measurement on the quantum kicked reactor
Energy Technology Data Exchange (ETDEWEB)
Sarkar, S; Satchell, J S
1987-07-15
The detailed time-dependent behaviour of the kinetic energy of the quantum kicked rotator is found for both destructive and nondestructive measurement models. This represents a full measurement analysis of a nonlinear dynamical system which shows chaos classically.
Measured efficiency of a luminescent solar concentrator PV module called Leaf Roof
Reinders, Angèle H.M.E; Debije, Michael G.; Rosemann, Alexander
2017-01-01
A functional prototype of a luminescent solar concentrator photovoltaic (LSC PV) module, called Leaf Roof, aims at demonstrating the design features of LSC PV technologies such as coloring, transparency, and flexibility in physical shape. In this paper, the prototype is presented and the first
DEFF Research Database (Denmark)
Madsen, Anni T.; Murray, Andrew S.; Jain, Mayank
2011-01-01
The rates of post-depositional mixing by bioturbation have been investigated using Optically Stimulated Luminescence (OSL) dating in two sediment cores (BAL2 and BAL5), retrieved from a sandy tidal flat in the Danish part of the Wadden Sea. A high-resolution chronology, consisting of thirty-six OSL...
Measurement of Solid-State Optical Refrigeration by Two-Band Differential Luminescence Thermometry
2010-03-01
high speed transimpedance amplifier that generates an output voltage proportional to the difference in the optical power in bands A and D, i.e., IA...bands in the luminescence spectrum by inter- ference filters, in combination with large core optical fi- bers and highly amplified balanced
Ten Kate, O.M.; De Jong, M.; Hintzen, H.T.; Van der Kolk, E.
2013-01-01
Solar cells of which the efficiency is not limited by the Shockley-Queisser limit can be obtained by integrating a luminescent spectral conversion layer into the cell structure. We have calculated the maximum efficiency of state-of-the-art c-Si, pc-Si, a-Si, CdTe, GaAs, CIS, CIGS, CGS, GaSb, and Ge
Measurement-Device-Independent Quantum Cryptography
Tang, Zhiyuan
Quantum key distribution (QKD) enables two legitimate parties to share a secret key even in the presence of an eavesdropper. The unconditional security of QKD is based on the fundamental laws of quantum physics. Original security proofs of QKD are based on a few assumptions, e.g., perfect single photon sources and perfect single-photon detectors. However, practical implementations of QKD systems do not fully comply with such assumptions due to technical limitations. The gap between theory and implementations leads to security loopholes in most QKD systems, and several attacks have been launched on sophisticated QKD systems. Particularly, the detectors have been found to be the most vulnerable part of QKD. Much effort has been put to build side-channel-free QKD systems. Solutions such as security patches and device-independent QKD have been proposed. However, the former are normally ad-hoc, and cannot close unidentified loopholes. The latter, while having the advantages of removing all assumptions on devices, is impractical to implement today. Measurement-device-independent QKD (MDI-QKD) turns out to be a promising solution to the security problem of QKD. In MDI-QKD, all security loopholes, including those yet-to-be discovered, have been removed from the detectors, the most critical part in QKD. In this thesis, we investigate issues related to the practical implementation and security of MDI-QKD. We first present a demonstration of polarization-encoding MDI-QKD. Taking finite key effect into account, we achieve a secret key rate of 0.005 bit per second (bps) over 10 km spooled telecom fiber, and a 1600-bit key is distributed. This work, together with other demonstrations, shows the practicality of MDI-QKD. Next we investigate a critical assumption of MDI-QKD: perfect state preparation. We apply the loss-tolerant QKD protocol and adapt it to MDI-QKD to quantify information leakage due to imperfect state preparation. We then present an experimental demonstration of
Jaque, Daniel; Vetrone, Fiorenzo
2012-07-01
The current status of luminescence nanothermometry is reviewed in detail. Based on the main parameters of luminescence including intensity, bandwidth, bandshape, polarization, spectral shift and lifetime, we initially describe and compare the different classes of luminescence nanothermometry. Subsequently, the various luminescent materials used in each case are discussed and the mechanisms at the root of the luminescence thermal sensitivity are described. The most important results obtained in each case are summarized and the advantages and disadvantages of these approaches are discussed.The current status of luminescence nanothermometry is reviewed in detail. Based on the main parameters of luminescence including intensity, bandwidth, bandshape, polarization, spectral shift and lifetime, we initially describe and compare the different classes of luminescence nanothermometry. Subsequently, the various luminescent materials used in each case are discussed and the mechanisms at the root of the luminescence thermal sensitivity are described. The most important results obtained in each case are summarized and the advantages and disadvantages of these approaches are discussed. This work was supported by the Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid (Project S2009/MAT-1756), by the Spanish Ministerio de Educacion y Ciencia (MAT2010-16161) and by Caja Madrid Foundation.
Quantum nondemolition measurement saturates fidelity trade-off
International Nuclear Information System (INIS)
Mista, L.; Filip, R.
2005-01-01
Full text: A general quantum measurement on an unknown quantum state enables us to estimate what the state originally was. Simultaneously, the measurement has a destructive effect on a measured quantum state which is reflected by the decrease of the output fidelity. We show for any d-level system that quantum non-demolition measurement controlled by a suitably prepared ancilla is a measurement in which the decrease of the output fidelity is minimal. The ratio between the estimation fidelity and the output fidelity can be continuously controlled by the preparation of the ancilla. Different measurement strategies on the ancilla to gain maximum estimation fidelity are analyzed. A feasible scheme of such a measurement for atomic and optical 2-level systems based on basic controlled-NOT gate is discussed. (author)
Fidelity induced distance measures for quantum states
International Nuclear Information System (INIS)
Ma Zhihao; Zhang Fulin; Chen Jingling
2009-01-01
Fidelity plays an important role in quantum information theory. In this Letter, we introduce new metric of quantum states induced by fidelity, and connect it with the well-known trace metric, Sine metric and Bures metric for the qubit case. The metric character is also presented for the qudit (i.e., d-dimensional system) case. The CPT contractive property and joint convex property of the metric are also studied.
DEFF Research Database (Denmark)
Duller, G.A.T.; Bøtter-Jensen, L.; Murray, A.S.
2003-01-01
A system designed for measurement of the optically stimulated luminescence (OSL) from individual sand-sized mineral grains has been constructed. Previously, this system was equipped only with a green laser emitting at 532 run, but now an infrared (IR) laser at 830 run has been added. It is now...... possible to interchangeably use the two laser sources for optical stimulation. This is especially valuable for the measurement of feldspars. The power density using the IR laser at the grain is similar to500 W cm(-2), and stimulation for 1 s reduces the OSL signal to near background level. Initial results...
Optimal Measurements for Simultaneous Quantum Estimation of Multiple Phases.
Pezzè, Luca; Ciampini, Mario A; Spagnolo, Nicolò; Humphreys, Peter C; Datta, Animesh; Walmsley, Ian A; Barbieri, Marco; Sciarrino, Fabio; Smerzi, Augusto
2017-09-29
A quantum theory of multiphase estimation is crucial for quantum-enhanced sensing and imaging and may link quantum metrology to more complex quantum computation and communication protocols. In this Letter, we tackle one of the key difficulties of multiphase estimation: obtaining a measurement which saturates the fundamental sensitivity bounds. We derive necessary and sufficient conditions for projective measurements acting on pure states to saturate the ultimate theoretical bound on precision given by the quantum Fisher information matrix. We apply our theory to the specific example of interferometric phase estimation using photon number measurements, a convenient choice in the laboratory. Our results thus introduce concepts and methods relevant to the future theoretical and experimental development of multiparameter estimation.
Optimal Measurements for Simultaneous Quantum Estimation of Multiple Phases
Pezzè, Luca; Ciampini, Mario A.; Spagnolo, Nicolò; Humphreys, Peter C.; Datta, Animesh; Walmsley, Ian A.; Barbieri, Marco; Sciarrino, Fabio; Smerzi, Augusto
2017-09-01
A quantum theory of multiphase estimation is crucial for quantum-enhanced sensing and imaging and may link quantum metrology to more complex quantum computation and communication protocols. In this Letter, we tackle one of the key difficulties of multiphase estimation: obtaining a measurement which saturates the fundamental sensitivity bounds. We derive necessary and sufficient conditions for projective measurements acting on pure states to saturate the ultimate theoretical bound on precision given by the quantum Fisher information matrix. We apply our theory to the specific example of interferometric phase estimation using photon number measurements, a convenient choice in the laboratory. Our results thus introduce concepts and methods relevant to the future theoretical and experimental development of multiparameter estimation.
Measurement-based local quantum filters and their ability to ...
Indian Academy of Sciences (India)
Debmalya Das
2017-05-30
May 30, 2017 ... Entanglement; local filters; quantum measurement. PACS No. 03.65 ... ties [4,5], it also plays a key role in quantum computing where it is ... Furthermore, we pro- vide an ..... Corresponding to each of these vectors, we can con-.
Muon 2 measurements and non-commutative geometry of quantum ...
Indian Academy of Sciences (India)
Abstract. We discuss a completely quantum mechanical treatment of the measurement of the anomalous magnetic moment of the muon. A beam of muons move in a strong uniform magnetic field and a weak focusing electrostatic field. Errors in the classical beam analysis are exposed. In the Dirac quantum beam analysis, ...
International Nuclear Information System (INIS)
Yu Watanabe; Masahito Ueda
2012-01-01
Full text: When we try to obtain information about a quantum system, we need to perform measurement on the system. The measurement process causes unavoidable state change. Heisenberg discussed a thought experiment of the position measurement of a particle by using a gamma-ray microscope, and found a trade-off relation between the error of the measured position and the disturbance in the momentum caused by the measurement process. The trade-off relation epitomizes the complementarity in quantum measurements: we cannot perform a measurement of an observable without causing disturbance in its canonically conjugate observable. However, at the time Heisenberg found the complementarity, quantum measurement theory was not established yet, and Kennard and Robertson's inequality erroneously interpreted as a mathematical formulation of the complementarity. Kennard and Robertson's inequality actually implies the indeterminacy of the quantum state: non-commuting observables cannot have definite values simultaneously. However, Kennard and Robertson's inequality reflects the inherent nature of a quantum state alone, and does not concern any trade-off relation between the error and disturbance in the measurement process. In this talk, we report a resolution to the complementarity in quantum measurements. First, we find that it is necessary to involve the estimation process from the outcome of the measurement for quantifying the error and disturbance in the quantum measurement. We clarify the implicitly involved estimation process in Heisenberg's gamma-ray microscope and other measurement schemes, and formulate the error and disturbance for an arbitrary quantum measurement by using quantum estimation theory. The error and disturbance are defined in terms of the Fisher information, which gives the upper bound of the accuracy of the estimation. Second, we obtain uncertainty relations between the measurement errors of two observables [1], and between the error and disturbance in the
Holographic patterning of luminescent photopolymer nanocomposites
International Nuclear Information System (INIS)
Sakhno, Oksana V.; Smirnova, Tatiana N.; Goldenberg, Leonid M.; Stumpe, Joachim
2008-01-01
Volume phase gratings in the photopolymerisable composites, containing luminescent nanoparticles have been fabricated for the first time. Nanoparticles of LaPO 4 , doped by Ce 3+ and Tb 3+ ions (the trade name is REN-X-green) with high luminescence quantum yield were used as a luminescent inorganic additive. The holographic gratings in such materials are formed as a result of the diffusion distribution of the nanoparticles during exposure of photopolymerisable composites to interference pattern. The influence of the pre-polymer formulation and the holographic patterning parameters on the grating formation is comprehensively investigated. The use of the optimised pre-polymer syrup containing two monomers with sufficiently different polymerisation rates allows fabrication of gratings with diffraction efficiency up to 80% at low optical losses (< 5%) (20 μm film thickness). To obtain maximum diffraction efficiency the intensity and the period of the interference pattern were optimised for each formulation. In addition maximum diffraction efficiency was achieved with the nanocomposites containing 30-32 wt.% of nanoparticles. On the other hand the highest possible modulation of the nanoparticles' concentration was obtained for the concentration of about 20 wt.%. In this case maximum ordering of the nanoparticles in the polymer matrix is achieved. The photoluminescence of the nanoparticles within the homogeneous polymer film and within the grating has been measured. The example application of the photopolymerisable composite containing luminescence inorganic nanoparticles in holographic security technology has been demonstrated
Quantum trajectories and measurements in continuous time. The diffusive case
International Nuclear Information System (INIS)
Barchielli, Alberto; Gregoratti, Matteo
2009-01-01
This course-based monograph introduces the reader to the theory of continuous measurements in quantum mechanics and provides some benchmark applications. The approach chosen, quantum trajectory theory, is based on the stochastic Schroedinger and master equations, which determine the evolution of the a-posteriori state of a continuously observed quantum system and give the distribution of the measurement output. The present introduction is restricted to finite-dimensional quantum systems and diffusive outputs. Two appendices introduce the tools of probability theory and quantum measurement theory which are needed for the theoretical developments in the first part of the book. First, the basic equations of quantum trajectory theory are introduced, with all their mathematical properties, starting from the existence and uniqueness of their solutions. This makes the text also suitable for other applications of the same stochastic differential equations in different fields such as simulations of master equations or dynamical reduction theories. In the next step the equivalence between the stochastic approach and the theory of continuous measurements is demonstrated. To conclude the theoretical exposition, the properties of the output of the continuous measurement are analyzed in detail. This is a stochastic process with its own distribution, and the reader will learn how to compute physical quantities such as its moments and its spectrum. In particular this last concept is introduced with clear and explicit reference to the measurement process. The two-level atom is used as the basic prototype to illustrate the theory in a concrete application. Quantum phenomena appearing in the spectrum of the fluorescence light, such as Mollow's triplet structure, squeezing of the fluorescence light, and the linewidth narrowing, are presented. Last but not least, the theory of quantum continuous measurements is the natural starting point to develop a feedback control theory in
Lepper, K.; Kuhns, C. K.; McKeever, S. W. S.; Sears, D. W. G.
2000-08-01
Martian polar deposits have the potential to reveal a wealth of information about the evolution of Mars' climate and surface environment. However, as pointed out by Clifford et al. in the summary of the First International Conference on Mars Polar Science and Exploration, 'The single greatest obstacle to unlocking and interpreting the geologic and climatic record preserved at the [martian] poles is the need for absolute dating.' At that same conference Lepper and McKeever proposed development of luminescence dating as a remote in-situ technique for absolute dating of silicate mineral grains incorporated in polar deposits. Clifford et al. have also acknowledged that luminescence dating is more practical from cost, engineering, and logistical perspectives than other isotope-based methods proposed for in-situ dating on Mars. We report here the results of ongoing experiments with terrestrial analogs of martian surface materials to establish a broad fundamental knowledge base from which robust dating procedures for robotic missions may be developed. This broad knowledge base will also be critical in determining the engineering requirements of remote in-situ luminescence dating equipment intended for use on Mars. Additional information can be found in the original extended abstract.
Blind quantum computation protocol in which Alice only makes measurements
Morimae, Tomoyuki; Fujii, Keisuke
2013-05-01
Blind quantum computation is a new secure quantum computing protocol which enables Alice (who does not have sufficient quantum technology) to delegate her quantum computation to Bob (who has a full-fledged quantum computer) in such a way that Bob cannot learn anything about Alice's input, output, and algorithm. In previous protocols, Alice needs to have a device which generates quantum states, such as single-photon states. Here we propose another type of blind computing protocol where Alice does only measurements, such as the polarization measurements with a threshold detector. In several experimental setups, such as optical systems, the measurement of a state is much easier than the generation of a single-qubit state. Therefore our protocols ease Alice's burden. Furthermore, the security of our protocol is based on the no-signaling principle, which is more fundamental than quantum physics. Finally, our protocols are device independent in the sense that Alice does not need to trust her measurement device in order to guarantee the security.
Stability of continuous-time quantum filters with measurement imperfections
Amini, H.; Pellegrini, C.; Rouchon, P.
2014-07-01
The fidelity between the state of a continuously observed quantum system and the state of its associated quantum filter, is shown to be always a submartingale. The observed system is assumed to be governed by a continuous-time Stochastic Master Equation (SME), driven simultaneously by Wiener and Poisson processes and that takes into account incompleteness and errors in measurements. This stability result is the continuous-time counterpart of a similar stability result already established for discrete-time quantum systems and where the measurement imperfections are modelled by a left stochastic matrix.
Al-Khalili, Jim
2003-01-01
In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.
Exceptional points and quantum correlations in precise measurements
International Nuclear Information System (INIS)
Thilagam, A
2012-01-01
We examine the physical manifestations of exceptional points and passage times in a two-level system which is subjected to quantum measurements and which admits a non-Hermitian description. Using an effective Hamiltonian acting in the two-dimensional space spanned by the evolving initial and final states, the effects of highly precise quantum measurements in which the monitoring device interferes significantly with the evolution dynamics of the monitored two-level system is analyzed. The dynamics of a multipartite system consisting of the two-level system, a source of external potential and the measurement device is examined using correlation measures such as entanglement and non-classical quantum correlations. Results show that the quantum correlations between the monitored (monitoring) systems is considerably decreased (increased) as the measurement precision nears the exceptional point, at which the passage time is half of the measurement duration. The results indicate that the underlying mechanism by which the non-classical correlations of quantum systems are transferred from one subsystem to another may be better revealed via use of geometric approaches. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’. (paper)
Quantum Measurement Theory in Gravitational-Wave Detectors
Directory of Open Access Journals (Sweden)
Stefan L. Danilishin
2012-04-01
Full Text Available The fast progress in improving the sensitivity of the gravitational-wave detectors, we all have witnessed in the recent years, has propelled the scientific community to the point at which quantum behavior of such immense measurement devices as kilometer-long interferometers starts to matter. The time when their sensitivity will be mainly limited by the quantum noise of light is around the corner, and finding ways to reduce it will become a necessity. Therefore, the primary goal we pursued in this review was to familiarize a broad spectrum of readers with the theory of quantum measurements in the very form it finds application in the area of gravitational-wave detection. We focus on how quantum noise arises in gravitational-wave interferometers and what limitations it imposes on the achievable sensitivity. We start from the very basic concepts and gradually advance to the general linear quantum measurement theory and its application to the calculation of quantum noise in the contemporary and planned interferometric detectors of gravitational radiation of the first and second generation. Special attention is paid to the concept of the Standard Quantum Limit and the methods of its surmounting.
Quantum Measurement Theory in Gravitational-Wave Detectors.
Danilishin, Stefan L; Khalili, Farid Ya
2012-01-01
The fast progress in improving the sensitivity of the gravitational-wave detectors, we all have witnessed in the recent years, has propelled the scientific community to the point at which quantum behavior of such immense measurement devices as kilometer-long interferometers starts to matter. The time when their sensitivity will be mainly limited by the quantum noise of light is around the corner, and finding ways to reduce it will become a necessity. Therefore, the primary goal we pursued in this review was to familiarize a broad spectrum of readers with the theory of quantum measurements in the very form it finds application in the area of gravitational-wave detection. We focus on how quantum noise arises in gravitational-wave interferometers and what limitations it imposes on the achievable sensitivity. We start from the very basic concepts and gradually advance to the general linear quantum measurement theory and its application to the calculation of quantum noise in the contemporary and planned interferometric detectors of gravitational radiation of the first and second generation. Special attention is paid to the concept of the Standard Quantum Limit and the methods of its surmounting.
International Nuclear Information System (INIS)
Rieser, U.
2009-01-01
The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materals in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs.
International Nuclear Information System (INIS)
Rieser, U.
2008-01-01
The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materals in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs
International Nuclear Information System (INIS)
Rieser, U.
2012-01-01
The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materials in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs.
International Nuclear Information System (INIS)
Rieser, U.
2009-01-01
The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materals in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs
International Nuclear Information System (INIS)
Rieser, U.
2013-01-01
The luminescence techniques have evolved over the last 40 years to a powerful dating instrument in archaeology and geoscience. Depending on how the luminescence is stimulated, one distinguishes the phenomena of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Each of these phenomena has its specific potential for dating various archaeological materials in the time range from medieval back to palaeolithic periods, or, speaking in geological terms, for dating of Holocene and late Pleistocene objects. The OSL and IRSL techniques are sometimes treated together as 'optical dating'. The luminescence techniques differ from other major dating techniques, such as 14 C, essentially by their applicability to inorganic materials, their wide age-range from about 100 years to more than 100,000 years and the kind of datable events which are the last exposure to heat or to light. (author). 10 refs., 3 figs.
Energy Technology Data Exchange (ETDEWEB)
Wu, Zhengyuan; Shen, Xiyang; Xiong, Huan; Li, Qingfei; Kang, Junyong; Fang, Zhilai [Xiamen University, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen (China); Lin, Feng; Yang, Bilan; Lin, Shilin [San' an Optoelectronics Co., Ltd, Xiamen (China); Shen, Wenzhong [Shanghai Jiao Tong University, Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics, Shanghai (China); Zhang, Tong-Yi [Shanghai University, Shanghai University Materials Genome Institute and Shanghai Materials Genome Institute, Shanghai (China)
2016-02-15
Interface modification of high indium content InGaN/GaN quantum wells was carried out by Mg pretreatment of the GaN barrier surface. The indium in the Mg-pretreated InGaN layer was homogeneously distributed, making the interfaces abrupt. The improved interface quality greatly enhanced light emission capacity. The cathodoluminescence intensity of the Mg-pretreated InGaN/GaN quantum wells was correspondingly much stronger than those of the InGaN/GaN quantum wells without Mg pretreatment. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Sarma, Runjun; Deka, Geetamoni; Mohanta, Dambarudhar, E-mail: best@tezu.ernet.in
2015-02-15
Highlights: • Thio-glycolic acid (TGA) coated Cd{sub 1−x}Mn{sub x}Se quantum dots have been prepared with varying x • Formation of QD heterostructure can be expected at a nonzero, but higher value of x. • The deep defect related emission can be attributed to V{sub Cd}–V{sub Se} di-vacancies, which is dominant for smaller values of x. • An appreciable charge transfer between Mn{sup 2+} ions and capping agent TGA is anticipated. - Abstract: We report on stoichiometry dependent manifested physical properties of thioglycolic acid (TGA) coated Cd{sub 1− x}Mn{sub x}Se QDs. While possessing a wurtzite phase, with increasing x, the QDs exhibited a notable blue-shifting of the onset of absorption. Attributed to V{sub Cd}–V{sub Se} di-vacancies, the QDs describe an intense deep-defect related emission response at smaller values of x (=0 to 0.3). Due to the facilitation of magnetic Mn{sup 2+} ion migration from the core to the QD surfaces, {sup 4}T{sub 1}–{sup 6}A{sub 1} transition based Mn{sup 2+} orange emission get suppressed at a higher x (=0.6 to 1). While the FT-IR spectra of the alloyed QDs display characteristic Mn–OH stretching mode at ∼644 cm{sup −1}, the peak located at ∼703 cm{sup −1} is assigned to Cd-Se bending. Furthermore, the QDs with a low x (=0.3), exhibit paramagnetic characteristics owing to the presence of uncorrelated, isolated Mn{sup 2+} spins. The collective luminescence and magnetic features would find immense scope in bio-labeling and imaging applications, apart from solid state luminescent components.
Self-guaranteed measurement-based quantum computation
Hayashi, Masahito; Hajdušek, Michal
2018-05-01
In order to guarantee the output of a quantum computation, we usually assume that the component devices are trusted. However, when the total computation process is large, it is not easy to guarantee the whole system when we have scaling effects, unexpected noise, or unaccounted for correlations between several subsystems. If we do not trust the measurement basis or the prepared entangled state, we do need to be worried about such uncertainties. To this end, we propose a self-guaranteed protocol for verification of quantum computation under the scheme of measurement-based quantum computation where no prior-trusted devices (measurement basis or entangled state) are needed. The approach we present enables the implementation of verifiable quantum computation using the measurement-based model in the context of a particular instance of delegated quantum computation where the server prepares the initial computational resource and sends it to the client, who drives the computation by single-qubit measurements. Applying self-testing procedures, we are able to verify the initial resource as well as the operation of the quantum devices and hence the computation itself. The overhead of our protocol scales with the size of the initial resource state to the power of 4 times the natural logarithm of the initial state's size.
Measuring the effective phonon density of states of a quantum dot in cavity quantum electrodynamics
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Nielsen, Per Kær; Kreiner-Møller, Asger
2013-01-01
We employ detuning-dependent decay-rate measurements of a quantum dot in a photonic-crystal cavity to study the influence of phonon dephasing in a solid-state quantum-electrodynamics experiment. The experimental data agree with a microscopic non-Markovian model accounting for dephasing from...... longitudinal acoustic phonons, and the analysis explains the difference between nonresonant cavity feeding in different nanocavities. From the comparison between experiment and theory we extract the effective phonon density of states experienced by the quantum dot in the nanocavity. This quantity determines...
A new flexible system for measuring thermally and optically stimulated luminescence
DEFF Research Database (Denmark)
Markey, B.G.; Bøtter-Jensen, L.; Duller, G.A.T.
1997-01-01
. New hardware features include a two-speed sample turntable, a new detachable beta irradiator with a Be window vacuum interface and the incorporation of an on-board minicomputer.,A completely new software concept was developed that allows the user unlimited control of the reader and has, at the same......The automated Riso TL/OSL reader system is used worldwide for luminescence dating, retrospective dosimetry environmental dosimetry and material characterization. In response to requests from many users we have re-designed the reader by incorporating a variety of new hardware and software features...
Measuring modulated luminescence using non-modulated stimulation: Ramping the sample period
DEFF Research Database (Denmark)
Poolton, N.R.J.; Bøtter-Jensen, L.; Andersen, C.E.
2003-01-01
. Directly analogous results to LM-OSL can, however, be achieved with non-modulated excitation sources, by ramping the sample period (RSP) of luminescence detection. RSP-OSL has the distinct advantage over LM-OSL in that, since the excitation remains at full power, data accumulation times (that can...... be considerable) can be reduced by typically 50%. RSP methods are universally applicable and can be employed, for example, where the excitation source is constant heat, rather than light: here, iso-thermal decay of phosphorescence becomes recorded as a sequence of peaks, corresponding to de-trapping of charge...
Quantum coherence in the time-resolved Auger measurement
Energy Technology Data Exchange (ETDEWEB)
Smirnova, Olga; Yakovlev, Vladislav S; Scrinzi, Armin
2003-12-19
We present a quantum mechanical model of the attosecond-XUV (extreme ultraviolet) pump and laser probe measurement of an Auger decay [Drescher et al., Nature (London) 419, 803 (2002)10.1038/nature01143] and investigate effects of quantum coherence. The time-dependent Schroedinger equation is solved by numerical integration and in analytic form. We explain the transition from a quasiclassical energy shift of the spectrum to the formation of sidebands and the enhancement of high- and low-energy tails of the Auger spectrum due to quantum coherence between photoionization and Auger decay.
Partial Measurements and the Realization of Quantum-Mechanical Counterfactuals
Paraoanu, G. S.
2011-07-01
We propose partial measurements as a conceptual tool to understand how to operate with counterfactual claims in quantum physics. Indeed, unlike standard von Neumann measurements, partial measurements can be reversed probabilistically. We first analyze the consequences of this rather unusual feature for the principle of superposition, for the complementarity principle, and for the issue of hidden variables. Then we move on to exploring non-local contexts, by reformulating the EPR paradox, the quantum teleportation experiment, and the entanglement-swapping protocol for the situation in which one uses partial measurements followed by their stochastic reversal. This leads to a number of counter-intuitive results, which are shown to be resolved if we give up the idea of attributing reality to the wavefunction of a single quantum system.
Weak measurements and quantum weak values for NOON states
Rosales-Zárate, L.; Opanchuk, B.; Reid, M. D.
2018-03-01
Quantum weak values arise when the mean outcome of a weak measurement made on certain preselected and postselected quantum systems goes beyond the eigenvalue range for a quantum observable. Here, we propose how to determine quantum weak values for superpositions of states with a macroscopically or mesoscopically distinct mode number, that might be realized as two-mode Bose-Einstein condensate or photonic NOON states. Specifically, we give a model for a weak measurement of the Schwinger spin of a two-mode NOON state, for arbitrary N . The weak measurement arises from a nondestructive measurement of the two-mode occupation number difference, which for atomic NOON states might be realized via phase contrast imaging and the ac Stark effect using an optical meter prepared in a coherent state. The meter-system coupling results in an entangled cat-state. By subsequently evolving the system under the action of a nonlinear Josephson Hamiltonian, we show how postselection leads to quantum weak values, for arbitrary N . Since the weak measurement can be shown to be minimally invasive, the weak values provide a useful strategy for a Leggett-Garg test of N -scopic realism.
Coherent versus Measurement Feedback: Linear Systems Theory for Quantum Information
Directory of Open Access Journals (Sweden)
Naoki Yamamoto
2014-11-01
Full Text Available To control a quantum system via feedback, we generally have two options in choosing a control scheme. One is the coherent feedback, which feeds the output field of the system, through a fully quantum device, back to manipulate the system without involving any measurement process. The other one is measurement-based feedback, which measures the output field and performs a real-time manipulation on the system based on the measurement results. Both schemes have advantages and disadvantages, depending on the system and the control goal; hence, their comparison in several situations is important. This paper considers a general open linear quantum system with the following specific control goals: backaction evasion, generation of a quantum nondemolished variable, and generation of a decoherence-free subsystem, all of which have important roles in quantum information science. Some no-go theorems are proven, clarifying that those goals cannot be achieved by any measurement-based feedback control. On the other hand, it is shown that, for each control goal there exists a coherent feedback controller accomplishing the task. The key idea to obtain all the results is system theoretic characterizations of the above three notions in terms of controllability and observability properties or transfer functions of linear systems, which are consistent with their standard definitions.
Measurement and the mathematical apparatus of quantum physics
International Nuclear Information System (INIS)
Slavnov, D.A.
2007-01-01
A scheme for constructing quantum mechanics in which the Hilbert space and linear operators are not primary elements on the theory is described. Some variant of the algebraic approach is instead considered. The elements of a noncommutative algebra (observables) and functionals in this algebra serve as the primary components of the theory. Such a scheme allows one to use the formalism of the classical (Kolmogorovian) theory of probability, and to reproduce the mathematical formalism of standard quantum mechanics and to specify borders of its applicability. A brief review of necessary data from the theory of algebras and probability theory is given. The manner is described in which the considered mathematical scheme agrees with the theory of quantum measurements and allows one to avoid quantum paradoxes [ru
Direct measurement of nonlinear properties of bipartite quantum states.
Bovino, Fabio Antonio; Castagnoli, Giuseppe; Ekert, Artur; Horodecki, Paweł; Alves, Carolina Moura; Sergienko, Alexander Vladimir
2005-12-09
Nonlinear properties of quantum states, such as entropy or entanglement, quantify important physical resources and are frequently used in quantum-information science. They are usually calculated from a full description of a quantum state, even though they depend only on a small number of parameters that specify the state. Here we extract a nonlocal and a nonlinear quantity, namely, the Renyi entropy, from local measurements on two pairs of polarization-entangled photons. We also introduce a "phase marking" technique which allows the selection of uncorrupted outcomes even with nondeterministic sources of entangled photons. We use our experimental data to demonstrate the violation of entropic inequalities. They are examples of nonlinear entanglement witnesses and their power exceeds all linear tests for quantum entanglement based on all possible Bell-Clauser-Horne-Shimony-Holt inequalities.
Measurement of gravity and gauge fields using quantum mechanical probes
International Nuclear Information System (INIS)
Anandan, J.
1986-01-01
The author considers the question of which quantities are observed when the gravitational and gauge fields are measured by a quantum mechanical probe. The motion of a quantum mechanical particle can be constructed, via Huyghens' principle, by the interference of secondary wavelets. Three types of interference phenomena are considered: interference of two coherent beams separated in space-time during part of their motion; interference of two coherent beams which are in the same region in spacetime but differ in energy or mass; and the Josphson effect and its generalization. The author shows how to determine the gravitational field by means of quantum interference. The corresponding problem for gauge fields is treated and a simple proof of the previously proved theorem for the reconstruction of the connection from the holonomy transformations is presented. A heuristic principle for the gravitational interaction of two quantum mechanical particles is formulated which implies the equivalence of inertial and active gravitational masses
Quantum continual measurements and a posteriori collapse on CCR
International Nuclear Information System (INIS)
Belavkin, V.P.
1992-01-01
A quantum stochastic model for the Markovian dynamics of an open system under the nondemolition unsharp observation which is continuous in time, is given. A stochastic equation for the posterior evolution of a quantum continuously observed system is derived and the spontaneous collapse (stochastically continuous reduction of the wave packet) is described. The quantum Langevin evolution equation is solved for the case of a quasi-free Hamiltonian in the initial CCR algebra with a linear output channel, and the posterior dynamics corresponding to an initial Gaussian state is found. It is shown for an example of the posterior dynamics of a quantum oscillator that any mixed state under a complete nondemolition measurement collapses exponentially to a pure Gaussian one. (orig.)
Measurement-device-independent quantum communication with an untrusted source
Xu, Feihu
2015-07-01
Measurement-device-independent quantum key distribution (MDI-QKD) can provide enhanced security compared to traditional QKD, and it constitutes an important framework for a quantum network with an untrusted network server. Still, a key assumption in MDI-QKD is that the sources are trusted. We propose here a MDI quantum network with a single untrusted source. We have derived a complete proof of the unconditional security of MDI-QKD with an untrusted source. Using simulations, we have considered various real-life imperfections in its implementation, and the simulation results show that MDI-QKD with an untrusted source provides a key generation rate that is close to the rate of initial MDI-QKD in the asymptotic setting. Our work proves the feasibility of the realization of a quantum network. The network users need only low-cost modulation devices, and they can share both an expensive detector and a complicated laser provided by an untrusted network server.
Memory-assisted measurement-device-independent quantum key distribution
Panayi, Christiana; Razavi, Mohsen; Ma, Xiongfeng; Lütkenhaus, Norbert
2014-04-01
A protocol with the potential of beating the existing distance records for conventional quantum key distribution (QKD) systems is proposed. It borrows ideas from quantum repeaters by using memories in the middle of the link, and that of measurement-device-independent QKD, which only requires optical source equipment at the user's end. For certain memories with short access times, our scheme allows a higher repetition rate than that of quantum repeaters with single-mode memories, thereby requiring lower coherence times. By accounting for various sources of nonideality, such as memory decoherence, dark counts, misalignment errors, and background noise, as well as timing issues with memories, we develop a mathematical framework within which we can compare QKD systems with and without memories. In particular, we show that with the state-of-the-art technology for quantum memories, it is potentially possible to devise memory-assisted QKD systems that, at certain distances of practical interest, outperform current QKD implementations.
Maire, E; Lelièvre, E; Brau, D; Lyons, A; Woodward, M; Fafeur, V; Vandenbunder, B
2000-04-10
We have developed an approach to study in single living epithelial cells both cell migration and transcriptional activation, which was evidenced by the detection of luminescence emission from cells transfected with luciferase reporter vectors. The image acquisition chain consists of an epifluorescence inverted microscope, connected to an ultralow-light-level photon-counting camera and an image-acquisition card associated to specialized image analysis software running on a PC computer. Using a simple method based on a thin calibrated light source, the image acquisition chain has been optimized following comparisons of the performance of microscopy objectives and photon-counting cameras designed to observe luminescence. This setup allows us to measure by image analysis the luminescent light emitted by individual cells stably expressing a luciferase reporter vector. The sensitivity of the camera was adjusted to a high value, which required the use of a segmentation algorithm to eliminate the background noise. Following mathematical morphology treatments, kinetic changes of luminescent sources were analyzed and then correlated with the distance and speed of migration. Our results highlight the usefulness of our image acquisition chain and mathematical morphology software to quantify the kinetics of luminescence changes in migrating cells.
Quantum measurement and real-time feedback with a spin-register in diamond
Blok, M.S.
2015-01-01
Gaining precise control over quantum systems is crucial for applications in quantum information processing and quantum sensing and to perform experimental tests of quantum mechanics. The experiments presented in this thesis implement quantum measurements and real-time feedback protocols that can
Quantum limits to center-of-mass measurements
International Nuclear Information System (INIS)
Vaughan, Timothy; Drummond, Peter; Leuchs, Gerd
2007-01-01
We discuss the issue of measuring the mean position (center of mass) of a group of bosonic or fermionic quantum particles, including particle number fluctuations. We introduce a standard quantum limit for these measurements at ultralow temperatures, and discuss this limit in the context of both photons and ultracold atoms. In the case of non-interacting harmonically trapped fermions, we present evidence that the Pauli exclusion principle has a strongly beneficial effect, giving rise to a 1/N scaling in the position standard deviation--as opposed to a 1/√(N) scaling for bosons. The difference between the actual mean-position fluctuation and this limit is evidence for quantum wave-packet spreading in the center of mass. This macroscopic quantum effect cannot be readily observed for noninteracting particles, due to classical pulse broadening. For this reason, we also study the evolution of photonic and matter-wave solitons, where classical dispersion is suppressed. In the photonic case, we show that the intrinsic quantum diffusion of the mean position can contribute significantly to uncertainties in soliton pulse arrival times. We also discuss ways in which the relatively long lifetimes of attractive bosons in matter-wave solitons may be used to demonstrate quantum interference between massive objects composed of thousands of particles
Dohnalova, K.; Fucikova, A.; Umesh, C.P.; Humpolickova, J.; Paulusse, Jos Marie Johannes; Valenta, J.; Zuilhof, H.
2012-01-01
The microscopic origin of the bright nanosecond blue-green photoluminescence (PL), frequently reported for synthesized organically terminated Si quantum dots (Si-QDs), has not been fully resolved, hampering potential applications of this interesting material. Here a comprehensive study of the PL
Dohnalová, K.; Gregorkiewicz, T.; Fucíková, A.; Valenta, J.; Umesh, C.; Paulusse, J.M.J.; Zuilhof, H.; Humpolícková, J.; Hof, van M.
2012-01-01
The microscopic origin of the bright nanosecond blue-green photoluminescence (PL), frequently reported for synthesized organically terminated Si quantum dots (Si-QDs), has not been fully resolved, hampering potential applications of this interesting material. Here a comprehensive study of the PL
Highly luminescent CdSe/ZnSe core-shell quantum dots of one-pot preparation in octadecene
Zeng, Q.; Kong, X.; Zhang, Y.; Zhang, H.
2008-01-01
CdSe/ZnSe core-shell quantum dots were synthesized using a new one-pot procedure where the core was prepared in octadecene. A ZnSe shell around a CdSe nanoparticle was formed by the reaction of selenium-richness on the surfaces of CdSe nanoparticles with Zn2+ from the injected zinc stearate
Surface plasmon inhibited photo-luminescence activation in CdSe/ZnS core-shell quantum dots
Czech Academy of Sciences Publication Activity Database
Chen, J.; Žídek, Karel; Abdellah, M.; Al-Marri, M.J.; Zheng, K.; Pullerits, T.
2016-01-01
Roč. 28, č. 25 (2016), č. článku 254001. ISSN 0953-8984 Institutional support: RVO:61389021 Keywords : surface plasmon * gold nanorods * quantum dots * energy transfer * photoactivation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.649, year: 2016 http://dx.doi.org/10.1088/0953-8984/28/25/254001
Foda, Mohamed F; Huang, Liang; Shao, Feng; Han, He-You
2014-02-12
Bright and stable CuInS2/ZnS@SiO2 nanoparticles with near-infrared (NIR) emission were competently prepared by incorporating the as-prepared hydrophobic CuInS2/ZnS quantum dots (QDs) directly into lipophilic silane micelles and subsequently an exterior silica shell was formed. The obtained CuInS2/ZnS@SiO2 nanoparticles homogeneously comprised both single-core and multicore remarkable CuInS2/ZnS QDs, while the silica shell thickness could be controlled to within 5-10 nm and their overall size was 17-25 nm. Also, the functionalized CuInS2/ZnS QDs encapsulated in the silica spheres, expedited their bioconjugation with holo-Transferrin (Tf) for further cancer cell imaging. The CuInS2/ZnS@SiO2 nanoparticles not only showed a dominant NIR band-edge luminescence at 650-720 nm with a quantum yield (QY) between 30 and 50%, without a recognized photoluminescence (PL) red shift, but also exhibited excellent PL and colloidal stability in aqueous media. Impressively, the cytotoxicity studies revealed minor suppression on cell viability under both CuInS2/ZnS@SiO2 and CuInS2/ZnS@SiO2@Tf concentrations up to 1 mg/mL. The application in live-cell imaging revealed that the potential of CuInS2/ZnS QDs as biocompatible, robust, cadmium-free, and brilliant NIR emitters is considered promising for fluorescent labels.
Zero-reabsorption doped-nanocrystal luminescent solar concentrators.
Erickson, Christian S; Bradshaw, Liam R; McDowall, Stephen; Gilbertson, John D; Gamelin, Daniel R; Patrick, David L
2014-04-22
Optical concentration can lower the cost of solar energy conversion by reducing photovoltaic cell area and increasing photovoltaic efficiency. Luminescent solar concentrators offer an attractive approach to combined spectral and spatial concentration of both specular and diffuse light without tracking, but they have been plagued by luminophore self-absorption losses when employed on practical size scales. Here, we introduce doped semiconductor nanocrystals as a new class of phosphors for use in luminescent solar concentrators. In proof-of-concept experiments, visibly transparent, ultraviolet-selective luminescent solar concentrators have been prepared using colloidal Mn(2+)-doped ZnSe nanocrystals that show no luminescence reabsorption. Optical quantum efficiencies of 37% are measured, yielding a maximum projected energy concentration of ∼6× and flux gain for a-Si photovoltaics of 15.6 in the large-area limit, for the first time bounded not by luminophore self-absorption but by the transparency of the waveguide itself. Future directions in the use of colloidal doped nanocrystals as robust, processable spectrum-shifting phosphors for luminescent solar concentration on the large scales required for practical application of this technology are discussed.
Optimal and secure measurement protocols for quantum sensor networks
Eldredge, Zachary; Foss-Feig, Michael; Gross, Jonathan A.; Rolston, S. L.; Gorshkov, Alexey V.
2018-04-01
Studies of quantum metrology have shown that the use of many-body entangled states can lead to an enhancement in sensitivity when compared with unentangled states. In this paper, we quantify the metrological advantage of entanglement in a setting where the measured quantity is a linear function of parameters individually coupled to each qubit. We first generalize the Heisenberg limit to the measurement of nonlocal observables in a quantum network, deriving a bound based on the multiparameter quantum Fisher information. We then propose measurement protocols that can make use of Greenberger-Horne-Zeilinger (GHZ) states or spin-squeezed states and show that in the case of GHZ states the protocol is optimal, i.e., it saturates our bound. We also identify nanoscale magnetic resonance imaging as a promising setting for this technology.
Quantum measurement and quantum gravity: many-worlds or collapse of the wavefunction?
International Nuclear Information System (INIS)
Singh, T P
2009-01-01
At present, there are two possible, and equally plausible, explanations for the physics of quantum measurement. The first explanation, known as the many-worlds interpretation, does not require any modification of quantum mechanics, and asserts that at the time of measurement the Universe splits into many branches, one branch for every possible alternative. The various branches do not interfere with each other because of decoherence, thus providing a picture broadly consistent with the observed Universe. The second explanation, which requires quantum mechanics to be modified from its presently known form, is that at the time of measurement the wavefunction collapses into one of the possible alternatives. The two explanations are mutually exclusive, and up until now, no theoretical reasoning has been put forward to choose one explanation over the other. In this article, we provide an argument which implies that the collapse interpretation is favored over the many-worlds interpretation. Our starting point is the assertion (which we justify) that there ought to exist a reformulation of quantum mechanics which does not refer to a classical spacetime manifold. The need for such a reformulation implies that quantum theory becomes nonlinear on the Planck mass/energy scale. Standard linear quantum mechanics is an approximation to this nonlinear theory, valid at energy scales much smaller than the Planck scale. Using ideas based on noncommutative differential geometry, we develop such a reformulation and derive a nonlinear Schroedinger equation, which can explain collapse of the wavefunction. We also obtain an expression for the lifetime of a quantum superposition. We suggest ideas for an experimental test of this model.
High-Efficiency Quantum Interrogation Measurements via the Quantum Zeno Effect
International Nuclear Information System (INIS)
Kwiat, P. G.; White, A. G.; Mitchell, J. R.; Nairz, O.; Weihs, G.; Weinfurter, H.; Zeilinger, A.
1999-01-01
The phenomenon of quantum interrogation allows one to optically detect the presence of an absorbing object, without the measuring light interacting with it. In an application of the quantum Zeno effect, the object inhibits the otherwise coherent evolution of the light, such that the probability that an interrogating photon is absorbed can in principle be arbitrarily small. We have implemented this technique, achieving efficiencies of up to 73% , and consequently exceeding the 50% theoretical maximum of the original ''interaction-free'' measurement proposal. We have also predicted and experimentally verified a previously unsuspected dependence on loss. (c) 1999 The American Physical Society
Probing 2D black phosphorus by quantum capacitance measurements
International Nuclear Information System (INIS)
Kuiri, Manabendra; Kumar, Chandan; Chakraborty, Biswanath; Gupta, Satyendra N; Naik, Mit H; Jain, Manish; Sood, A K; Das, Anindya
2015-01-01
Two-dimensional materials and their heterostructures have emerged as a new class of materials, not only for fundamental physics but also for electronic and optoelectronic applications. Black phosphorus (BP) is a relatively new addition to this class of materials. Its strong in-plane anisotropy makes BP a unique material for making conceptually new types of electronic devices. However, the global density of states (DOS) of BP in device geometry has not been measured experimentally. Here, we report the quantum capacitance measurements together with the conductance measurements on an hBN-protected few-layer BP (∼six layers) in a dual-gated field effect transistor (FET) geometry. The measured DOS from our quantum capacitance is compared with density functional theory (DFT). Our results reveal that the transport gap for quantum capacitance is smaller than that in conductance measurements due to the presence of localized states near the band edge. The presence of localized states is confirmed by the variable range hopping seen in our temperature dependence conductivity. A large asymmetry is observed between the electron and hole side. This asymmetric nature is attributed to the anisotropic band dispersion of BP. Our measurements establish the uniqueness of quantum capacitance in probing the localized states near the band edge, hitherto not seen in conductance measurements. (paper)
Luminescence and luminescence quenching of Eu{sub 2}Mo{sub 4}O{sub 15}
Energy Technology Data Exchange (ETDEWEB)
Janulevicius, Matas; Grigorjevaite, Julija; Merkininkaite, Greta [Department of Analytical and Environmental Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania); Sakirzanovas, Simas [Department of Applied Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania); Katelnikovas, Arturas, E-mail: arturas.katelnikovas@chf.vu.lt [Department of Analytical and Environmental Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania)
2016-11-15
A polycrystalline Eu{sub 2}Mo{sub 4}O{sub 15} phosphor sample was prepared by high temperature solid state reaction. Phase purity and morphological features of the phosphor were investigated by X-ray diffraction and scanning electron microscopy, respectively. Reflectance spectra showed that the optical band gap of Eu{sub 2}Mo{sub 4}O{sub 15} is 2.95 eV. Phosphor emits intensive red light when excited with 394 and 465 nm radiation. Temperature dependent emission and luminescence lifetime measurements revealed that external and internal quantum yields decrease at the same rate and that luminescence quenches due to photoionization. The calculated external quantum yields for 394 and 465 nm excitation were 7.8% and 53.5%, respectively.
Husen, Nicholas; Roozeboom, Nettie; Liu, Tianshu; Sullivan, John P.
2015-01-01
A quantitative global skin-friction measurement technique is proposed. An oil-film is doped with a luminescent molecule and thereby made to fluoresce in order to resolve oil-film thickness, and Particle Image Surface Flow Visualization is used to resolve the velocity field of the surface of the oil-film. Skin-friction is then calculated at location x as (x )xh, where x is the displacement of the surface of the oil-film and is the dynamic viscosity of the oil. The data collection procedure and data analysis procedures are explained, and preliminary experimental skin-friction results for flow over the wing of the CRM are presented.
Estimation of atomic interaction parameters by quantum measurements
DEFF Research Database (Denmark)
Kiilerich, Alexander Holm; Mølmer, Klaus
Quantum systems, ranging from atomic systems to field modes and mechanical devices are useful precision probes for a variety of physical properties and phenomena. Measurements by which we extract information about the evolution of single quantum systems yield random results and cause a back actio...... strategies, we address the Fisher information and the Cramér-Rao sensitivity bound. We investigate monitoring by photon counting, homodyne detection and frequent projective measurements respectively, and exemplify by Rabi frequency estimation in a driven two-level system....
Exciton luminescence in In0.3Ga0.7As/GaAs quantum well heterostructures
International Nuclear Information System (INIS)
Kapon, Eli; Mereuta, Alexandru; Dorogan, Andrei; Dragutan, Nicolae; Vieru, Tatiana; Syrbu, Nicolae
2011-01-01
Radiation maxima were observed in photoluminescence spectra of GaAs/ In 0.3 Ga 0.7 As/ GaAs in case of 632.8 nm and 532 nm He-Ne laser excitation conditioned by the recombination from ground (e1-hh1, e1-lh1) and excited (e2-hh2, e2-lh2) states of polarionic excitons in quantum wells. The doublet character of e1-hh1, e1-lh1 transitions can be explained by the interaction of excitons in quantum wells. Radiation maxima are revealed in the region of 1.5eV energy conditioned by recombination transitions E b -hh1, E b -lh1of the GaAs buffer layer.
Foundations and measures of quantum non-Markovianity
International Nuclear Information System (INIS)
Breuer, Heinz-Peter
2012-01-01
The basic features of the dynamics of open quantum systems, such as the dissipation of energy, the decay of coherences, the relaxation to an equilibrium or non-equilibrium stationary state, and the transport of excitations in complex structures are of central importance in many applications of quantum mechanics. The theoretical description, analysis and control of non-Markovian quantum processes play an important role in this context. While in a Markovian process an open system irretrievably loses information to its surroundings, non-Markovian processes feature a flow of information from the environment back to the open system, which implies the presence of memory effects and represents the key property of non-Markovian quantum behaviour. Here, we review recent ideas developing a general mathematical definition for non-Markovianity in the quantum regime and a measure for the degree of memory effects in the dynamics of open systems, which are based on the exchange of information between system and environment. We further study the dynamical effects induced by the presence of system–environment correlations in the total initial state and design suitable methods to detect such correlations through local measurements on the open system. (topical review)
Role of measurement in feedback-controlled quantum engines
Yi, Juyeon; Kim, Yong Woon
2018-01-01
In feedback controls, measurement is an essential step in designing protocols according to outcomes. For quantum mechanical systems, measurement has another effect; to supply energy to the measured system. We verify that in feedback-controlled quantum engines, measurement plays a dual role; not only as an auxiliary to perform feedback control but also as an energy supply to drive the engines. We consider a specific engine cycle exploiting feedback control followed by projective measurement and show that the maximum bound of the extractable work is set by both the efficacy of the feedback control and the energy change caused by projective measurement. We take a concrete example of an engine using an immobile spin-1/2 particle as a working substance and suggest two possible scenarios for work extraction.
On the problem of measurement in quantum mechanics
International Nuclear Information System (INIS)
He Zuoxiu
1993-01-01
Some new developments in the theory of measurement in quantum mechanics are presented. The theory of measurement given by Von Neumann is shown to be incorrect, since the process of measurement is one of increasing entropy and cannot be derived within the scope of Schroedinger's equation. The new theory developed by Daneri, Loinger and Prosperi can avoid the difficulties previously encountered and, furthermore, can explain the EPR paradox
Quantum mechanics with spontaneous localization and the quantum theory of measurement
International Nuclear Information System (INIS)
Benatti, F.; Ghirardi, G.C.; Rimini, A.; Weber, T.
1986-10-01
Recently a modification of quantum dynamics allowing a unified description of microscopic and macroscopic systems has been introduced. We investigate here the consequences of this approach for the measurement problem. We show that in this way one gets a consistent and objective solution of the problem of the wave packet reduction. (author)
Optically stimulated luminescence from quartz measured using the linear modulation technique
International Nuclear Information System (INIS)
Bulur, E.; Boetter-Jensen, L.; Murray, A.S.
2000-01-01
The optically stimulated luminescence (OSL) from heated natural quartz has been investigated using the linear modulation technique (LMT), in which the excitation light intensity is increased linearly during stimulation. In contrast to conventional stimulation, which usually produces a monotonically decreasing signal, linearly increasing the stimulation power gives peaks in the signal as a function of time. In cases where the OSL signal contains more than one component, the linear increase in power of the stimulation light may result in a curve containing overlapping peaks, where the most easily stimulated component occurs at a shorter time. This allows the separation of the overlapping OSL components, which are assumed to originate from different traps. The LM-OSL curve from quartz shows an initial peak followed by a broad one. Deconvolution using curve fitting has shown that the composite OSL curve from quartz can be approximated well by using a linear combination of first-order peaks. In addition to the three known components, i.e. fast, medium and slow components from continuous-wave-OSL studies, an additional slow component is also identified for the first time. The dose responses and thermal stabilities of the various components are also studied
A cost-effective measurement-device-independent quantum key distribution system for quantum networks
Valivarthi, Raju; Zhou, Qiang; John, Caleb; Marsili, Francesco; Verma, Varun B.; Shaw, Matthew D.; Nam, Sae Woo; Oblak, Daniel; Tittel, Wolfgang
2017-12-01
We experimentally realize a measurement-device-independent quantum key distribution (MDI-QKD) system. It is based on cost-effective and commercially available hardware such as distributed feedback lasers and field-programmable gate arrays that enable time-bin qubit preparation and time-tagging, and active feedback systems that allow for compensation of time-varying properties of photons after transmission through deployed fiber. We examine the performance of our system, and conclude that its design does not compromise performance. Our demonstration paves the way for MDI-QKD-based quantum networks in star-type topology that extend over more than 100 km distance.
Measurement and quasi-states in quantum mechanics
International Nuclear Information System (INIS)
Harper, C.D.
1987-01-01
Part of the task of quantum logic is to account for the collapse of the state vector during measurement. A difficulty in this is that it is not obvious how to describe measurement quantum mechanically as the interaction of two or more systems; interacting quantum-mechanical systems do not possess states, so their states cannot collapse. This dissertation shows that component systems of a composite system possess families of state-like vectors. These are the quasi-projections of the state vector of the composite system, each associated with a family of commutable observables. Often these quasi-projections cluster so closely around a quasi-state that they are practically indistinguishable from it. A description of measurement based on quasi-projections reveals the apparent collapse of the state vector during measurement to be illusory. The continuous evolution of the state of the composite system give rise to abrupt changes in the quasi-projections which make it appear that the state has changed. The quasi-projections cease to cluster near one quasi-state, are momentarily scattered, and then cluster again near another quasi-state. The concept of quasi-projection is also used to generalize the quantum logic of Birkhoff and von Neumann in such a fashion that a proposition can always be assigned a truth value
Quantum optical measurements with undetected photons through vacuum field indistinguishability.
Lee, Sun Kyung; Yoon, Tai Hyun; Cho, Minhaeng
2017-07-26
Quantum spectroscopy and imaging with undetected idler photons have been demonstrated by measuring one-photon interference between the corresponding entangled signal fields from two spontaneous parametric down conversion (SPDC) crystals. In this Report, we present a new quantum optical measurement scheme utilizing three SPDC crystals in a cascading arrangement; here, neither the detection of the idler photons which interact with materials of interest nor their conjugate signal photons which do not interact with the sample is required. The coherence of signal beams in a single photon W-type path-entangled state is induced and modulated by indistinguishabilities of the idler beams and crucially the quantum vacuum fields. As a result, the optical properties of materials or objects interacting with the idler beam from the first SPDC crystal can be measured by detecting second-order interference between the signal beams generated by the other two SPDC crystals further down the set-up. This gedankenexperiment illustrates the fundamental importance of vacuum fields in generating an optical tripartite entangled state and thus its crucial role in quantum optical measurements.
On the Interpretation of Measurement Within the Quantum Theory
Cooper, Leon N.; Van Vechten, Deborah
1969-01-01
In interpretation of the process of measurement is proposed which can be placed wholly within the quantum theory. The entire system including the apparatus and even the mind of the observer can be considered to develop according to the Schrodinger equation. (RR)
Dynamics of 'quantumness' measures in the decohering harmonic ...
Indian Academy of Sciences (India)
2016-07-26
Jul 26, 2016 ... are relative measures, using different definitions of the distance between the given quantum states and the set ..... the correspondence principle on the face of it, as they ..... validity of using the negativity – ηW – as an absolute.
Directly Measuring the Degree of Quantum Coherence using Interference Fringes
Wang, Yi-Tao; Tang, Jian-Shun; Wei, Zhi-Yuan; Yu, Shang; Ke, Zhi-Jin; Xu, Xiao-Ye; Li, Chuan-Feng; Guo, Guang-Can
2017-01-01
Quantum coherence is the most distinguished feature of quantum mechanics. It lies at the heart of the quantum-information technologies as the fundamental resource and is also related to other quantum resources, including entanglement. It plays a critical role in various fields, even in biology. Nevertheless, the rigorous and systematic resource-theoretic framework of coherence has just been developed recently, and several coherence measures are proposed. Experimentally, the usual method to measure coherence is to perform state tomography and use mathematical expressions. Here, we alternatively develop a method to measure coherence directly using its most essential behavior—the interference fringes. The ancilla states are mixed into the target state with various ratios, and the minimal ratio that makes the interference fringes of the "mixed state" vanish is taken as the quantity of coherence. We also use the witness observable to witness coherence, and the optimal witness constitutes another direct method to measure coherence. For comparison, we perform tomography and calculate l1 norm of coherence, which coincides with the results of the other two methods in our situation. Our methods are explicit and robust, providing a nice alternative to the tomographic technique.
Uncertainty relation and simultaneous measurements in quantum theory
International Nuclear Information System (INIS)
Busch, P.
1982-01-01
In this thesis the question for the interpretation of the uncertainty relation is picked up, and a program for the justification of its individualistic interpretation is formulated. By means of quantum mechanical models for the position and momentum measurement a justification of the interpretaton has been tried by reconstruction of the origin of the uncertainties from the conditions of the measuring devices and the determination of the relation of the measured results to the object. By means of a model of the common measurement it could be shown how the uncertainty relation results from the not eliminable mutual disturbance of the devices and the uncertainty relation for the measuring system. So finally the commutation relation is conclusive. For the illustration the split experiment is discussed, first according to Heisenberg with fixed split, then for the quantum mechanical, movable split (Bohr-Einstein). (orig./HSI) [de
International Nuclear Information System (INIS)
Kovacs, A.; Baranyai, M.; Wojnarovits, L.; Slezsak, I.; McLaughlin, W.L.; Miller, S.D.; Miller, A.; Fuochi, P.G.; Lavalle, M.
1999-01-01
A new potential dosimetry system 'Sunna' containing a microcrystalline dispersion of an optically-stimulated fluor in a plastic matrix has been recently developed to measure and image high doses. Our previous investigations have revealed that the new dosimeter system is capable of measuring absorbed doses in the dose range of 1-100 kGy. The optically-stimulated luminescence (OSL) analysis is based on the blue light stimulation of the colour center states produced upon irradiation, and the intensity of the resulting red-light emission is used to measure absorbed dose. This analysis is carried out with a simple table-top fluorimeter developed for this purpose having also the ability to calculate the mathematical formula of the calibration function. The Sunna dosimeter was recently investigated for potential use in lower dose range below 1 kGy. These investigations have shown that the film is suitable for measuring doses in the range of 1-1000 Gy for both electron and gamma radiation. To test the applicability of the film, its reproducibility, stability, sensitivity to ambient and UV light and irradiation temperature were measured. The stability of the dosimeter was investigated by monitoring the change of the OSL signal with storage time after irradiation. Further experiments proved the homogeneity of the film with respect to thickness variation, and limited differences in its response were found between batches. (author)
Quantum Measurement Backaction and Upconverting Microwave Signals with Mechanical Resonators
Peterson, R. W.
The limits of optical measurement and control of mechanical motion are set by the quantum nature of light. The familiar shot noise limit can be avoided by increasing the optical power, but at high enough powers, the backaction of the randomly-arriving photons' radiation pressure can grow to become the dominant force on the system. This thesis will describe an experiment showing how backaction limits the laser cooling of macroscopic drumhead membranes, as well as work on how these membranes can be used to upconvert microwave signals to optical frequencies, potentially preserving the fragile quantum state of the upconverted signal.
Information-disturbance tradeoff in quantum measurements
International Nuclear Information System (INIS)
Maccone, Lorenzo
2006-01-01
We present a simple information-disturbance tradeoff relation valid for any general measurement apparatus: The disturbance between input and output states is lower bounded by the information the apparatus provides in distinguishing these two states
International Nuclear Information System (INIS)
Fujioka, Kouki; Manabe, Noriyoshi; Hanada, Sanshiro; Hoshino, Akiyoshi; Yamamoto, Kenji; Hiruoka, Masaki; Sato, Keisuke; Hirakuri, Kenji; Miyasaka, Ryosuke; Tilley, Richard D; Manome, Yoshinobu
2008-01-01
Semiconductor quantum dots (QDs) hold some advantages over conventional organic fluorescent dyes. Due to these advantages, they are becoming increasingly popular in the field of bioimaging. However, recent work suggests that cadmium based QDs affect cellular activity. As a substitute for cadmium based QDs, we have developed photoluminescent stable silicon quantum dots (Si-QDs) with a passive-oxidation technique. Si-QDs (size: 6.5 ± 1.5 nm) emit green light, and they have been used as biological labels for living cell imaging. In order to determine the minimum concentration for cytotoxicity, we investigated the response of HeLa cells. We have shown that the toxicity of Si-QDs was not observed at 112 μg ml -1 and that Si-QDs were less toxic than CdSe-QDs at high concentration in mitochondrial assays and with lactate dehydrogenase (LDH) assays. Especially under UV exposure, Si-QDs were more than ten times safer than CdSe-QDs. We suggest that one mechanism for the cytotoxicity is that Si-QDs can generate oxygen radicals and these radicals are associated with membrane damages. This work has demonstrated the suitability of Si-QDs for bioimaging in lower concentration, and their cytotoxicity and one toxicity mechanism at high concentration
Feng, Qian; Xiao, Wenqing; Zheng, Yongping; Lin, Yuda; Li, Jiaxin; Ye, Qingying; Huang, Zhigao
2018-01-01
A novel approach has been developed to synthesize slightly fluorinated graphene quantum dots (GQDs-F) through thermal cutting of highly fluorinated graphene. The fluorinated graphene with substantial structure defects is fragile and is readily attacked. The direct evaporation of abundant CFn (n = 2, 3) groups near structure defects lead to the loss of adjacent skelton C atoms, and the fluorinated graphene can be thermally cut into GQDs-F with a relatively uniform nanosize in pyrolysis at 810 K. The GQDs-F with a low F/C atomic ratio of ca. 0.03 exhibit excitation wavelength-dependent properties with multicolor photoluminescence (PL) from blue to green. At the same time, F adatoms that are most likely located at the edges of GQDs-F have a high efficiency of introducing paramagnetic centres, and GQDs-F show a strong paramagnetism because of sp3-type defects and magnetic zigzag edges. The graphene quantum dots with such multimodal capabilities should have great applied value in material science. PMID:29316730
Energy Technology Data Exchange (ETDEWEB)
Liang, Qingshuang; Bai, Yijia; Han, Lin; Deng, Xiaolong [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Graduate School, Chinese Academy of Sciences, Beijing 10049 (China); Wu, Xiaojie [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang, Zhongchang [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Liu, Xiaojuan, E-mail: lxjuan@ciac.jl.cn [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Meng, Jian, E-mail: jmeng@ciac.jl.cn [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)
2013-11-15
An one-pot synthesis of aqueous ZnSe:Cu nanocrystals (NCs) is realized in aqueous solution by a facile yet efficient hydrothermal technique. The dopant emission spectrum of the NCs is tunable, spanning a wide range from 438 to 543 nm. Room-temperature quantum yield for the NCs prepared at the optimal conditions reaches as high as 20% without any post-treatment. The ZnSe:Cu NCs prepared in a neutral aqueous solution (pH=8) are remarkably stable and exhibit comparatively high photoluminescent quantum yield (PL QY) as high as 17%. First-principles pseudopotential calculations using plane-wave basis functions have been performed. The formation energies of copper ions occupied in the interstitial octahedron and substitutional tetrahedral Zn{sup 2+} sites have been calculated. The occupation of copper ions in the interstitial octahedral site is found to be more thermodynamics-facilitated by −0.98 eV. The density of state analysis indicates that the Cu-related emission is primary dominated by the substitutional tetrahedral Cu ions, and the large dopant related emission width of ZnSe:Cu NCs originated from the corresponding Cu 3d impurity band. Highlights: • One-pot synthesis of aqueous ZnSe:Cu nanocrystals with tunable emission and high QY%. • ZnSe:Cu NCs exhibit high QY% at neutral pH suitable for biological application. • The microscopic mechanism underlying Cu-related emission has been provided.
Control and Measurement of an Xmon with the Quantum Socket
McConkey, T. G.; Bejanin, J. H.; Earnest, C. T.; McRae, C. R. H.; Rinehart, J. R.; Weides, M.; Mariantoni, M.
The implementation of superconducting quantum processors is rapidly reaching scalability limitations. Extensible electronics and wiring solutions for superconducting quantum bits (qubits) are among the most imminent issues to be tackled. The necessity to substitute planar electrical interconnects (e.g., wire bonds) with three-dimensional wires is emerging as a fundamental pillar towards scalability. In a previous work, we have shown that three-dimensional wires housed in a suitable package, named the quantum socket, can be utilized to measure high-quality superconducting resonators. In this work, we set out to test the quantum socket with actual superconducting qubits to verify its suitability as a wiring solution in the development of an extensible quantum computing architecture. To this end, we have designed and fabricated a series of Xmon qubits. The qubits range in frequency from about 6 to 7 GHz with anharmonicity of 200 MHz and can be tuned by means of Z pulses. Controlling tunable Xmons will allow us to verify whether the three-dimensional wires contact resistance is low enough for qubit operation. Qubit T1 and T2 times and single qubit gate fidelities are compared against current standards in the field.
Measure problem in slow roll inflation and loop quantum cosmology
International Nuclear Information System (INIS)
Corichi, Alejandro; Karami, Asieh
2011-01-01
We consider the measure problem in standard slow-roll inflationary models from the perspective of loop quantum cosmology (LQC). Following recent results by Ashtekar and Sloan, we study the probability of having enough e-foldings and focus on its dependence on the quantum gravity scale, including the transition of the theory to the limit where general relativity (GR) is recovered. Contrary to the standard expectation, the probability of having enough inflation, that is close to 1 in LQC, grows and tends to 1 as one approaches the GR limit. We study the origin of the tension between these results with those by Gibbons and Turok, and offer an explanation that brings these apparent contradictory results into a coherent picture. As we show, the conflicting results stem from different choices of initial conditions for the computation of probability. The singularity-free scenario of loop quantum cosmology offers a natural choice of initial conditions, and suggests that enough inflation is generic.
Relational description of the measurement process in quantum field theory
International Nuclear Information System (INIS)
Gambini, Rodolfo; Porto, Rafael A.
2002-01-01
We have recently introduced a realistic, covariant, interpretation for the reduction process in relativistic quantum mechanics. The basic problem for a covariant description is the dependence of the states on the frame within which collapse takes place. A suitable use of the causal structure of the devices involved in the measurement process allowed us to introduce a covariant notion for the collapse of quantum states. However, a fully consistent description in the relativistic domain requires the extension of the interpretation to quantum fields. The extension is far from straightforward. Besides the obvious difficulty of dealing with the infinite degrees of freedom of the field theory, one has to analyse the restrictions imposed by causality concerning the allowed operations in a measurement process. In this paper we address these issues. We shall show that, in the case of partial causally connected measurements, our description allows us to include a wider class of causal operations than the one resulting from the standard way of computing conditional probabilities. This alternative description could be experimentally tested. A verification of this proposal would give stronger support to the realistic interpretations of the states in quantum mechanics. (author)
Verifiable Measurement-Only Blind Quantum Computing with Stabilizer Testing.
Hayashi, Masahito; Morimae, Tomoyuki
2015-11-27
We introduce a simple protocol for verifiable measurement-only blind quantum computing. Alice, a client, can perform only single-qubit measurements, whereas Bob, a server, can generate and store entangled many-qubit states. Bob generates copies of a graph state, which is a universal resource state for measurement-based quantum computing, and sends Alice each qubit of them one by one. Alice adaptively measures each qubit according to her program. If Bob is honest, he generates the correct graph state, and, therefore, Alice can obtain the correct computation result. Regarding the security, whatever Bob does, Bob cannot get any information about Alice's computation because of the no-signaling principle. Furthermore, malicious Bob does not necessarily send the copies of the correct graph state, but Alice can check the correctness of Bob's state by directly verifying the stabilizers of some copies.
Luminescence properties of the Sm-doped borate glasses
International Nuclear Information System (INIS)
Kindrat, I.I.; Padlyak, B.V.; Drzewiecki, A.
2015-01-01
The optical absorption and photoluminescence (emission and excitation) spectra as well as decay kinetics of a series of the Sm-doped glasses with Li 2 B 4 O 7 , LiKB 4 O 7 , CaB 4 O 7 , and LiCaBO 3 compositions were investigated and analysed. The Li 2 B 4 O 7 :Sm, LiKB 4 O 7 :Sm, CaB 4 O 7 :Sm, and LiCaBO 3 :Sm glasses of high optical quality have been obtained from the corresponding polycrystalline compounds in the air atmosphere, using a standard glass technology. On the basis of electron paramagnetic resonance (EPR) and optical spectra analysis it was shown that the samarium impurity is incorporated into the glass network as Sm 3+ (4f 5 , 6 H 5/2 ) ions, exclusively. All observed 4f – 4f transitions of the Sm 3+ centres in the optical absorption and luminescence spectra of the investigated glasses are identified. Most intense emission band of the Sm 3+ ions peaked about 598 nm ( 4 G 5/2 → 6 H 7/2 transition) is characterised by a single exponential decay with typical lifetime values, which depend on the basic glass composition as well as concentration and local structure of the Sm 3+ luminescence centres. The quantum efficiency has been evaluated for observed transitions of the Sm 3+ centres using obtained experimental lifetimes and radiative lifetimes calculated by Judd–Ofelt theory. The calculated high quantum efficiencies and measured quantum yields of luminescence show that the investigated borate glasses are perspective luminescence materials. Energy transfer from the Ce 3+ non-controlled impurity and intrinsic luminescence centres to the Sm 3+ centres has been observed. Peculiarities of the Sm 3+ local structure in the network of investigated glasses have been discussed based on the obtained spectroscopic results and structural data. - Highlights: • The Sm-doped Li 2 B 4 O 7 , LiKB 4 O 7 , CaB 4 O 7 , and LiCaBO 3 glasses of high quality were obtained. • EPR, optical absorption and luminescence spectra of Sm 3+ ions in obtained glasses were
Nonlinearities in the quantum measurement process of superconducting qubits
International Nuclear Information System (INIS)
Serban, Ioana
2008-05-01
The work described in this thesis focuses on the investigation of decoherence and measurement backaction, on the theoretical description of measurement schemes and their improvement. The study presented here is centered around quantum computing implementations using superconducting devices and most important, the Josephson effect. The measured system is invariantly a qubit, i. e. a two-level system. The objective is to study detectors with increasing nonlinearity, e. g. coupling of the qubit to the frequency a driven oscillator, or to the bifurcation amplifier, to determine the performance and backaction of the detector on the measured system and to investigate the importance of a strong qubit-detector coupling for the achievement of a quantum non-demolition type of detection. The first part gives a very basic introduction to quantum information, briefly reviews some of the most promising physical implementations of a quantum computer before focusing on the superconducting devices. The second part presents a series of studies of different qubit measurements, describing the backaction of the measurement onto the measured system and the internal dynamics of the detector. Methodology adapted from quantum optics and chemical physics (master equations, phase-space analysis etc.) combined with the representation of a complex environment yielded a tool capable of describing a nonlinear, non-Markovian environment, which couples arbitrarily strongly to the measured system. This is described in chapter 3. Chapter 4 focuses on the backaction on the qubit and presents novel insights into the qubit dephasing in the strong coupling regime. Chapter 5 uses basically the same system and technical tools to explore the potential of a fast, strong, indirect measurement, and determine how close such a detection would ideally come to the quantum non-demolition regime. Chapter 6 focuses on the internal dynamics of a strongly driven Josephson junction. The analytical results are based on
Nonlinearities in the quantum measurement process of superconducting qubits
Energy Technology Data Exchange (ETDEWEB)
Serban, Ioana
2008-05-15
The work described in this thesis focuses on the investigation of decoherence and measurement backaction, on the theoretical description of measurement schemes and their improvement. The study presented here is centered around quantum computing implementations using superconducting devices and most important, the Josephson effect. The measured system is invariantly a qubit, i. e. a two-level system. The objective is to study detectors with increasing nonlinearity, e. g. coupling of the qubit to the frequency a driven oscillator, or to the bifurcation amplifier, to determine the performance and backaction of the detector on the measured system and to investigate the importance of a strong qubit-detector coupling for the achievement of a quantum non-demolition type of detection. The first part gives a very basic introduction to quantum information, briefly reviews some of the most promising physical implementations of a quantum computer before focusing on the superconducting devices. The second part presents a series of studies of different qubit measurements, describing the backaction of the measurement onto the measured system and the internal dynamics of the detector. Methodology adapted from quantum optics and chemical physics (master equations, phase-space analysis etc.) combined with the representation of a complex environment yielded a tool capable of describing a nonlinear, non-Markovian environment, which couples arbitrarily strongly to the measured system. This is described in chapter 3. Chapter 4 focuses on the backaction on the qubit and presents novel insights into the qubit dephasing in the strong coupling regime. Chapter 5 uses basically the same system and technical tools to explore the potential of a fast, strong, indirect measurement, and determine how close such a detection would ideally come to the quantum non-demolition regime. Chapter 6 focuses on the internal dynamics of a strongly driven Josephson junction. The analytical results are based on
Quantum Jarzynski equality with multiple measurement and ...
Indian Academy of Sciences (India)
three different cases: (i) the full evolution is unitary with no intermediate measurements, (ii) with ... theorems have important application in nanotechnology and nanophysics. One of the ... Thus the joint probability of state being in |i0〉 and |iτ 〉 is.
Dohnalová, Kateřina; Fučíková, Anna; Umesh, Chinnaswamy P; Humpolíčková, Jana; Paulusse, Jos M J; Valenta, Jan; Zuilhof, Han; Hof, Martin; Gregorkiewicz, Tom
2012-10-22
The microscopic origin of the bright nanosecond blue-green photoluminescence (PL), frequently reported for synthesized organically terminated Si quantum dots (Si-QDs), has not been fully resolved, hampering potential applications of this interesting material. Here a comprehensive study of the PL from alkyl-terminated Si-QDs of 2-3 nm size, prepared by wet chemical synthesis is reported. Results obtained on the ensemble and those from the single nano-object level are compared, and they provide conclusive evidence that efficient and tunable emission arises due to radiative recombination of electron-hole pairs confined in the Si-QDs. This understanding paves the way towards applications of chemical synthesis for the development of Si-QDs with tunable sizes and bandgaps. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Bekin, N.A.; Zhukavin, R.Kh.; Kovalevskij, K.A.; Pavlov, S.G.; Shastin, V.N.; Zvonkov, B.N.; Uskova, E.A.
2005-01-01
Terahertz spontaneous emission (∼ 3-3.5 THz) based on 2D-continuum-shallow donor (Si) states transitions has been investigated from both GaAs/InGaAs:Si and GaAs/InGaAsP:Si selectively doped heterostructures under CO 2 laser excitation at the liquid helium temperature. It is shown that the population inversion and the amplification with the coefficient up to 100-300 cm -1 per active layer can be realized for the planar doping level N D ≅ 10 11 cm -2 in multilayer structures with 50 periods of quantum wells under the pump flux density 10 23 quant/cm 2 s [ru
Algebraic and algorithmic frameworks for optimized quantum measurements
DEFF Research Database (Denmark)
Laghaout, Amine; Andersen, Ulrik Lund
2015-01-01
von Neumann projections are the main operations by which information can be extracted from the quantum to the classical realm. They are, however, static processes that do not adapt to the states they measure. Advances in the field of adaptive measurement have shown that this limitation can...... be overcome by "wrapping" the von Neumann projectors in a higher-dimensional circuit which exploits the interplay between measurement outcomes and measurement settings. Unfortunately, the design of adaptive measurement has often been ad hoc and setup specific. We shall here develop a unified framework...
DEFF Research Database (Denmark)
Shirokov, M. E.; Shulman, Tatiana
2014-01-01
We give a detailed description of a low-dimensional quantum channel (input dimension 4, Choi rank 3) demonstrating the symmetric form of superactivation of one-shot quantum zero-error capacity. This property means appearance of a noiseless (perfectly reversible) subchannel in the tensor square...... of a channel having no noiseless subchannels. Then we describe a quantum channel with an arbitrary given level of symmetric superactivation (including the infinite value). We also show that superactivation of one-shot quantum zero-error capacity of a channel can be reformulated in terms of quantum measurement...
Development of measurement protocols for quantum magnetometry
DEFF Research Database (Denmark)
Stark, Alexander
and protocols to enhance the lifetime and the coherences of the NV center with the overall goal of enhancing the capabilities of this sensor in the field of magnetometry. In order to realize complex protocols, a sophisticated software control of the measurement setup is required. A general software framework......, is serving as rigorous framework to reduce the complexity of the setup configuration by a fundamental separation of tasks. As a consequence, the general idea of this framework is not limited to experiments with color centers in diamond, but can find application in any laboratory environment. The measurement...... of magnetic fields in the high-frequency GHz regimes is challenging. In this thesis, a continuous dynamical decoupling protocol is developed and implemented, which extends the capabilities of the NV sensor to probe GHz signals with a narrow bandwidth. Moreover, the protocol protects the system from noise...
Indian Academy of Sciences (India)
1Faculty of Science and Arts, Department of Chemistry, Bozok University, Yozgat 66900, Turkey. 2Faculty of Science, Department of Chemistry, Erciyes ... synthesized by the conventional solid-state reaction method, their crystal structures and luminescence properties were investigated. X-ray diffraction patterns (XRD) ...
International Nuclear Information System (INIS)
Smith, Leon; Haque, Mamoon; Hill, Robin; Morales, Johnny
2015-01-01
Cone beam computed tomography (CBCT) is now widely used to image radiotherapy patients prior to treatment for the purpose of accurate patient setup. However each CBCT image delivered to a patient increases the total radiation dose that they receive. The measurement of the dose delivered from the CBCT images is not readily performed in the clinic. In this study, we have used commercially available optically stimulated luminescence (OSLD) dosimeters to measure the dose delivered by the Varian OBI on a radiotherapy linear accelerator. Calibration of the OSLDs was achieved by using a therapeutic X-ray unit. The dose delivered by a head CBCT scan was found to be 3.2 ± 0.3 mGy which is similar in magnitude to the dose of a head computed tomography (CT) scan. The results of this study suggest that the radiation hazard associated with CBCT is of a similar nature to that of conventional CT scans. We have also demonstrated that the OSLDs are suitable for these low X-ray dose measurements.
Continuous quantum measurements and the action uncertainty principle
Mensky, Michael B.
1992-09-01
The path-integral approach to quantum theory of continuous measurements has been developed in preceding works of the author. According to this approach the measurement amplitude determining probabilities of different outputs of the measurement can be evaluated in the form of a restricted path integral (a path integral “in finite limits”). With the help of the measurement amplitude, maximum deviation of measurement outputs from the classical one can be easily determined. The aim of the present paper is to express this variance in a simpler and transparent form of a specific uncertainty principle (called the action uncertainty principle, AUP). The most simple (but weak) form of AUP is δ S≳ℏ, where S is the action functional. It can be applied for simple derivation of the Bohr-Rosenfeld inequality for measurability of gravitational field. A stronger (and having wider application) form of AUP (for ideal measurements performed in the quantum regime) is |∫{/' t″ }(δ S[ q]/δ q( t))Δ q( t) dt|≃ℏ, where the paths [ q] and [Δ q] stand correspondingly for the measurement output and for the measurement error. It can also be presented in symbolic form as Δ(Equation) Δ(Path) ≃ ℏ. This means that deviation of the observed (measured) motion from that obeying the classical equation of motion is reciprocally proportional to the uncertainty in a path (the latter uncertainty resulting from the measurement error). The consequence of AUP is that improving the measurement precision beyond the threshold of the quantum regime leads to decreasing information resulting from the measurement.
Measurement of photomultiplier effective quantum efficiency
International Nuclear Information System (INIS)
Arshad, S.; Gowers, C.; Nielsen, P.
1998-07-01
The JET divertor LIDAR system, is being modified to perform measurements of plasma edge electron temperature and density in the new gas-box divertor configuration. The change involves raising the line of sight from the divertor region so that the laser beam passes through the plasma edge reaching a depth of ∼ 5 cm inside the boundary. Changes are also being made to the detection system. This currently employs a grating, spectrometer and a streak camera. The new system will contain a 4-channel filter spectrometer with microchannel plate (MCP) photomuItipliers
New methods for the measurement and alteration of quantum states
International Nuclear Information System (INIS)
Steuernagel, O.
1996-01-01
Themes of this thesis are the mathematical representation, measurement-technical reconstruction, and preparation of quantum states as well as their alteration by measurement. The main topics of the considerations are quantum-mechanical system states, the complet description of which pursues by means of density operators. The first chapter presents a general mathematical scheme for the representaion of density operators by means of projection operators. The second chapter explains a scheme for the syntehsis of Fock states by means of a linear mixer. The third chapter answers the question, whether spontaneous emitted light, which is emitted by an atom with large spatial extension, can show self-interferences and lets conclude on thee coherent structure of the c.m. wave function of the emitting atom. The last chapter reconstructs measurement results on the coherence loss of atoms in an atomic-beam experiment by spontaneous emission in the language of the density-operator formalism
International Nuclear Information System (INIS)
Zhao Meixia; Su Hua; Mao Zongwan; Ji Liangnian
2012-01-01
A series of CdSe and CdSe/CdS quantum dots (QDs) labeled with amino acid-modified β-cyclodextrin (β-CD) was prepared by a simple ultrasonic method. These amino acid-modified β-CD-coated QDs are very soluble and stable in biological buffer. They also have high colloidal stability and strong optical emission properties that are similar to those of untreated tri-n-octylphosphine oxide (TOPO)-coated QDs. The quantum yields (QYs) of these amino acid-modified β-CD-coated CdSe and CdSe/CdS QDs in biological buffer were found to be very high. In particular, the QYs of the positively charged L-His-β-CD-coated CdSe/CdS QDs were as high as 33.5±1.8%. In addition, the fluorescence lifetime of these QDs was also very long in PBS solutions as determined by frequency domain spectroscopy. For example, the lifetime of L-His-β-CD-coated CdSe/CdS QDs was 8.6 ns. The in vitro cytotoxicity of these QDs in ECV-304, SH-SY5Y and HeLa cells was found to be lower. L-His-β-CD-coated CdSe/CdS QDs were the least cytotoxic (IC 50 95.6±3.2 mg mL -1 in ECV-304 cells after 48 h). The flow cytometry results show that the positively charged amino acid led to a considerable increase in biocompatibility of QDs. This may be attributed to the presence of an amino acid-modified β-CD outer layer, which enhanced the biocompatibility. - Highlights: → Amino acid-modified β-CD-coated QDs were prepared by a simple ultrasonic method. → Amino acid-modified β-CD-coated QDs have appropriate size, high colloidal stability and strong optical emission properties. → In vitro cytotoxicity is lower in ECV-304, SH-SY5Y and HeLa cells. → The positive charge of amino acid resulted in a considerable increase in biocompatibility of QDs.
Luminescent lanthanide coordination polymers
Energy Technology Data Exchange (ETDEWEB)
Ma, L.; Evans, O.R.; Foxman, B.M.; Lin, W.
1999-12-13
One-dimensional lanthanide coordination polymers with the formula Ln(isonicotinate){sub 3}(H{sub 2}O){sub 2} (Ln = Ce, Pr, Nd, Sm, Eu, Tb; 1a-f) were synthesized by treating nitrate or perchlorate salts of Ln(III) with 4-pyridinecarboxaldehyde under hydro(solvo)thermal conditions. Single-crystal and powder X-ray diffraction studies indicate that these lanthanide coordination polymers adopt two different structures. While Ce(III), Pr(III), and Nd(III) complexes adopt a chain structure with alternating Ln-(carboxylate){sub 2}-Ln and Ln-(carboxylate){sub 4}-Ln linkages, Sm(III), Eu(III), and Tb(III) complexes have a doubly carboxylate-bridged infinite-chain structure with one chelating carboxylate group on each metal center. In both structures, the lanthanide centers also bind to two water molecules to yield an eight-coordinate, square antiprismatic geometry. The pyridine nitrogen atoms of the isonicotinate groups do not coordinate to the metal centers in these lanthanide(III) complexes; instead, they direct the formation of Ln(III) coordination polymers via hydrogen bonding with coordinated water molecules. Photoluminescence measurements show that Tb(isonicotinate){sub 3}(H{sub 2}O){sub 2} is highly emissive at room temperature with a quantum yield of {approximately}90%. These results indicate that highly luminescent lanthanide coordination polymers can be assembled using a combination of coordination and hydrogen bonds. Crystal data for 1a: monoclinic space group P2{sub 1}/c, a = 9.712(2) {angstrom}, b = 19.833(4) {angstrom}, c = 11.616(2) {angstrom}, {beta} = 111.89(3){degree}, Z = 4. Crystal data for 1f: monoclinic space group C2/c, a = 20.253(4) {angstrom}, b = 11.584(2) {angstrom}, c = 9.839(2) {angstrom}, {beta} = 115.64(3){degree}, Z = 8.
Energy Technology Data Exchange (ETDEWEB)
Li, Zhichun; Kong, Long; Huang, Shouqiang; Li, Liang [School of Environmental Science and Engineering, Shanghai Jiao Tong University (China)
2017-07-03
We successfully prepared QDs incorporated into a silica/alumina monolith (QDs-SAM) by a simple sol-gel reaction of an Al-Si single precursor with CsPbBr{sub 3} QDs blended in toluene solution, without adding water and catalyst. The resultant transparent monolith exhibits high photoluminescence quantum yields (PLQY) up to 90 %, and good photostability under strong illumination of blue light for 300 h. We show that the preliminary ligand exchange of didodecyl dimethyl ammonium bromide (DDAB) was very important to protect CsPbBr{sub 3} QDs from surface damages during the sol-gel reaction, which not only allowed us to maintain the original optical properties of CsPbBr{sub 3} QDs but also prevented the aggregation of QDs and made the monolith transparent. The CsPbBr{sub 3} QDs-SAM in powder form was easily mixed into the resins and applied as color-converting layer with curing on blue light-emitting diodes (LED). The material showed a high luminous efficacy of 80 lm W{sup -1} and a narrow emission with a full width at half maximum (FWHM) of 25 nm. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
Li, Zhichun; Kong, Long; Huang, Shouqiang; Li, Liang
2017-07-03
We successfully prepared QDs incorporated into a silica/alumina monolith (QDs-SAM) by a simple sol-gel reaction of an Al-Si single precursor with CsPbBr 3 QDs blended in toluene solution, without adding water and catalyst. The resultant transparent monolith exhibits high photoluminescence quantum yields (PLQY) up to 90 %, and good photostability under strong illumination of blue light for 300 h. We show that the preliminary ligand exchange of didodecyl dimethyl ammonium bromide (DDAB) was very important to protect CsPbBr 3 QDs from surface damages during the sol-gel reaction, which not only allowed us to maintain the original optical properties of CsPbBr 3 QDs but also prevented the aggregation of QDs and made the monolith transparent. The CsPbBr 3 QDs-SAM in powder form was easily mixed into the resins and applied as color-converting layer with curing on blue light-emitting diodes (LED). The material showed a high luminous efficacy of 80 lm W -1 and a narrow emission with a full width at half maximum (FWHM) of 25 nm. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Energy Technology Data Exchange (ETDEWEB)
Rousset, J.-G., E-mail: j-g.rousset@fuw.edu.pl; Kobak, J.; Janik, E.; Slupinski, T.; Golnik, A.; Kossacki, P.; Nawrocki, M.; Pacuski, W. [Faculty of Physics, Institute of Experimental Physics, University of Warsaw, ul. Pasteura 5, PL-02-093 Warszawa (Poland); Parlinska-Wojtan, M. [Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Krakow (Poland)
2016-05-14
We report on the optical properties of structures containing self assembled CdTe quantum dots (QDs) combined with Te and Se based distributed Bragg reflectors either in a half cavity geometry with a relatively broad cavity mode or in a full cavity geometry where the cavity mode is much narrower. We show that for both structures the extraction coefficient of the light emitted from the QDs ensemble is enhanced by more than one order of magnitude with respect to the QDs grown on a ZnTe buffer. However, a single QD line broadening is observed and attributed to an unintentional incorporation of Se in the vicinity of the CdTe QDs. We show that postponing the QDs growth for 24 h after the distributed Bragg reflector deposition allows recovering sharp emission lines from individual QDs. This two step growth method is proven to be efficient also for the structures with CdTe QDs containing a single Mn{sup 2+} ion.
International Nuclear Information System (INIS)
Boehme, Christian Gerhard Heinrich
2011-01-01
Modern particle accelerators are applied for a long time no more only in the fundamental physical research but in ever larger extent also in the concrete application for instance in the tumor irradiation or the microprocessor fabrication. The precise knowledge of the beam profile is thereby of great importance for the success. But in intermediate-energy hadron accelerators it hitherto not satisfyingly succeeds to measure the beam profiles not disturbingly. These study presents two not beam-disturbing measuring methods, which are based on the ion beam-residual gas interactions of luminescence and ionization. They were developed for different framework conditions at the JESSICA beam place of the COSY accelerator of the Juelich research center, an advance experiment of the planned European Spallation Source (ESS), as well at the proton synchrotron COSY itself, and the iThemba Laboratory for Accelerator Based Science, Somerset West, South Africa. Thereby the studies consider a large range of possible configuration parameters: Particle momenta from 3 MeV/c to 3 GeV/c, pressures from 1 mbar to 10 -11 mbar and time structures from DC beam to beam bunches of 100 ns length. The experimental arrangement, the application ranges, and the advantages and disadvantages of both methods are explained in this book.
A Quantum Non-Demolition Parity measurement in a mixed-species trapped-ion quantum processor
Marinelli, Matteo; Negnevitsky, Vlad; Lo, Hsiang-Yu; Flühmann, Christa; Mehta, Karan; Home, Jonathan
2017-04-01
Quantum non-demolition measurements of multi-qubit systems are an important tool in quantum information processing, in particular for syndrome extraction in quantum error correction. We have recently demonstrated a protocol for quantum non-demolition measurement of the parity of two beryllium ions by detection of a co-trapped calcium ion. The measurement requires a sequence of quantum gates between the three ions, using mixed-species gates between beryllium hyperfine qubits and a calcium optical qubit. Our work takes place in a multi-zone segmented trap setup in which we have demonstrated high fidelity control of both species and multi-well ion shuttling. The advantage of using two species of ion is that we can individually manipulate and read out the state of each ion species without disturbing the internal state of the other. The methods demonstrated here can be used for quantum error correcting codes as well as quantum metrology and are key ingredients for realizing a hybrid universal quantum computer based on trapped ions. Mixed-species control may also enable the investigation of new avenues in quantum simulation and quantum state control. left the group and working in a company now.
Multi-qubit parity measurement in circuit quantum electrodynamics
International Nuclear Information System (INIS)
DiVincenzo, David P; Solgun, Firat
2013-01-01
We present a concept for performing direct parity measurements on three or more qubits in microwave structures with superconducting resonators coupled to Josephson-junction qubits. We write the quantum-eraser conditions that must be fulfilled for the parity measurements as requirements for the scattering phase shift of our microwave structure. We show that these conditions can be fulfilled with present-day devices. We present one particular scheme, implemented with two-dimensional cavity techniques, in which each qubit should be coupled equally to two different microwave cavities. The magnitudes of the couplings that are needed are in the range that has been achieved in current experiments. A quantum calculation indicates that the measurement is optimal if the scattering signal can be measured with near single-photon sensitivity. A comparison with an extension of a related proposal from cavity optics is presented. We present a second scheme, for which a scalable implementation of the four-qubit parities of the surface quantum error correction code can be envisioned. It uses three-dimensional cavity structures, using cavity symmetries to achieve the necessary multiple resonant modes within a single resonant structure. (paper)
International Nuclear Information System (INIS)
Adegoke, Oluwasesan; Hosten, Eric; McCleland, Cedric; Nyokong, Tebello
2012-01-01
Graphical abstract: A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery. Highlights: ► Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. ► Quantum dots fluorescence is quenched by the radical. ► In the presence of bromide ions the fluorescence is restored. ► The sensor is more selective to bromine ions than other common ions. - Abstract: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
Quantum measurement of a rapidly rotating spin qubit in diamond.
Wood, Alexander A; Lilette, Emmanuel; Fein, Yaakov Y; Tomek, Nikolas; McGuinness, Liam P; Hollenberg, Lloyd C L; Scholten, Robert E; Martin, Andy M
2018-05-01
A controlled qubit in a rotating frame opens new opportunities to probe fundamental quantum physics, such as geometric phases in physically rotating frames, and can potentially enhance detection of magnetic fields. Realizing a single qubit that can be measured and controlled during physical rotation is experimentally challenging. We demonstrate quantum control of a single nitrogen-vacancy (NV) center within a diamond rotated at 200,000 rpm, a rotational period comparable to the NV spin coherence time T 2 . We stroboscopically image individual NV centers that execute rapid circular motion in addition to rotation and demonstrate preparation, control, and readout of the qubit quantum state with lasers and microwaves. Using spin-echo interferometry of the rotating qubit, we are able to detect modulation of the NV Zeeman shift arising from the rotating NV axis and an external DC magnetic field. Our work establishes single NV qubits in diamond as quantum sensors in the physically rotating frame and paves the way for the realization of single-qubit diamond-based rotation sensors.
Memory-assisted measurement-device-independent quantum key distribution
International Nuclear Information System (INIS)
Panayi, Christiana; Razavi, Mohsen; Ma, Xiongfeng; Lütkenhaus, Norbert
2014-01-01
A protocol with the potential of beating the existing distance records for conventional quantum key distribution (QKD) systems is proposed. It borrows ideas from quantum repeaters by using memories in the middle of the link, and that of measurement-device-independent QKD, which only requires optical source equipment at the user's end. For certain memories with short access times, our scheme allows a higher repetition rate than that of quantum repeaters with single-mode memories, thereby requiring lower coherence times. By accounting for various sources of nonideality, such as memory decoherence, dark counts, misalignment errors, and background noise, as well as timing issues with memories, we develop a mathematical framework within which we can compare QKD systems with and without memories. In particular, we show that with the state-of-the-art technology for quantum memories, it is potentially possible to devise memory-assisted QKD systems that, at certain distances of practical interest, outperform current QKD implementations. (paper)
Measure theoretical approach to recurrent properties for quantum dynamics
International Nuclear Information System (INIS)
Otobe, Yoshiki; Sasaki, Itaru
2011-01-01
Poincaré's recurrence theorem, which states that every Hamiltonian dynamics enclosed in a finite volume returns to its initial position as close as one wishes, is a mathematical basis of statistical mechanics. It is Liouville's theorem that guarantees that the dynamics preserves the volume on the state space. A quantum version of Poincaré's theorem was obtained in the middle of the 20th century without any volume structures of the state space (Hilbert space). One of our aims in this paper is to establish such properties of quantum dynamics from an analog of Liouville's theorem, namely, we will construct a natural probability measure on the Hilbert space from a Hamiltonian defined on the space. Then we will show that the measure is invariant under the corresponding Schrödinger flow. Moreover, we show that the dynamics naturally causes an infinite-dimensional Weyl transformation. It also enables us to discuss the ergodic properties of such dynamics. (paper)
Applications of quantum measurement in single and many body systems
International Nuclear Information System (INIS)
Steixner, V.
2010-01-01
This thesis contains a study about the influence of the back action of a signal emitted by a trapped ion onto itself. The continuous measurement signal is used to alter the motional state of the ion, corresponding to classical friction, in order to cool the ion. The quantum mechanical evolution of the ion with the help of stochastic Schroedinger- and master equations is explored, as well as experimental results. A second method of feedback to obtain the momentum necessary for cooling by means of electromagnetically induced transparency is discussed next. This method allows for a theoretical cooling down to the motional ground state. In a second part of the thesis, the measurement of particle currents in optical lattices is discussed. The usual method of measuring spatial correlations in a cold gas, the time-of-flight method, disadvantageously destroys the measured sample. Here a measurement scheme for atoms with an internal Lambda level structure, coupled with lasers as a Raman transition, is used instead. The measured photons are transformed with the help of homodyne detection into a continuous photon current proportional to the particle current. This thesis contains numerical and analytical calculations for this measurement process and the back action on the measured system. As an application example, the measurement of superfluid currents in a ring optical lattice is described, as well as the entanglement of two of these macroscopic quantum objects. (author) [de
The measurement problem in quantum mechanics: A phenomenological investigation
Hunter, Joel Brooks
2008-10-01
This dissertation is a phenomenological investigation of the measurement problem in quantum mechanics. The primary subject matter for description and analysis is scientific instruments and their use in experiments which elicit the measurement problem. A methodological critique is mounted against the ontological commitments taken for granted in the canonical interpretations of quantum theory and the scientific activity of measurement as the necessary interface between theoretical interest and perceptual results. I argue that an aesthetic dimension of reality functions as aproto-scientific establishment of sense-making that constantly operates to set integratively all other cognitively neat determinations, including scientifically rendered objects that are intrinsically non-visualizable. The way in which data "key in" to the original and originative register of the sensible in observation is clarified by examining prostheses, measuring apparatuses and instruments that are sense-conveying and -integrative with the human sensorium. Experiments, technology and instrumentation are examined in order to understand how knowing and that which is known is bonded by praxis-aisthesis. Quantum measurement is a praxic-dynamie activity and homologically structured and structur ing functional engagement in terms of instantiation, quantifiability, and spatiotemporal differentiation. The distinctions between a beauty-aesthetic and praxis-aisthesis are delineated. It is argued that a beauty-aesthetic is a construal of the economic dimension of scientific objects and work, and is not the primary manner in which the aesthetic dimension is disclosed. The economic dimension of abstractions reduces to an austere aesthetic of calculative economy. Nature itself, however, is not stingy; it is intrinsically capacious, extravagant, full of surprise, nuance, ambiguity and allusiveness. The capaciousness of Nature and the way in which we are integratively set within Nature in a materiality
Entanglement measure for general pure multipartite quantum states
International Nuclear Information System (INIS)
Heydari, Hoshang; Bjoerk, Gunnar
2004-01-01
We propose an explicit formula for a measure of entanglement of pure multipartite quantum states. We discuss the mathematical structure of the measure and give a brief explanation of its physical motivation. We apply the measure on some pure, tripartite, qubit states and demonstrate that, in general, the entanglement can depend on what actions are performed on the various subsystems, and specifically if the parties in possession of the subsystems cooperate or not. We also give some simple but illustrative examples of the entanglement of four-qubit and m-qubit states
Directory of Open Access Journals (Sweden)
Veeranarayanan S
2012-07-01
Full Text Available Srivani Veeranarayanan, Aby Cheruvathoor Poulose, M Sheikh Mohamed, Yutaka Nagaoka, Seiki Iwai, Yuya Nakagame, Shosaku Kashiwada, Yasuhiko Yoshida, Toru Maekawa, D Sakthi KumarBio Nano Electronics Research Centre, Graduate School of Interdisciplinary New Science, Toyo University, Kawagoe, JapanAbstract: This paper presents the synthesis of aqueous cadmium sulfide (CdS quantum dots (QDs and silica-encapsulated CdS QDs by reverse microemulsion method and utilized as targeted bio-optical probes. We report the role of CdS as an efficient cell tag with fluorescence on par with previously documented cadmium telluride and cadmium selenide QDs, which have been considered to impart high levels of toxicity. In this study, the toxicity of bare QDs was efficiently quenched by encapsulating them in a biocompatible coat of silica. The toxicity profile and uptake of bare CdS QDs and silica-coated QDs, along with the CD31-labeled, silica-coated CdS QDs on human umbilical vein endothelial cells and glioma cells, were investigated. The effect of size, along with the time-dependent cellular uptake of the nanomaterials, has also been emphasized. Enhanced, high-specificity imaging toward endothelial cell lines in comparison with glioma cells was achieved with CD31 antibody-conjugated nanoparticles. The silica-coated nanomaterials exhibited excellent biocompatibility and greater photostability inside live cells, in addition to possessing an extended shelf life. In vivo biocompatibility and localization study of silica-coated CdS QDs in medaka fish embryos, following direct nanoparticle exposure for 24 hours, authenticated the nanomaterials' high potential for in vivo imaging, augmented with superior biocompatibility. As expected, CdS QD-treated embryos showed 100% mortality, whereas the silica-coated QD-treated embryos stayed viable and healthy throughout and after the experiments, devoid of any deformities. We provide highly cogent and convincing evidence for such
Luminescence of water or ice as a new detection method for magnetic monopoles
Directory of Open Access Journals (Sweden)
Pollmann Anna Obertacke
2017-01-01
We present analysis techniques to use luminescence in neutrino telescopes and discuss experimental setups to measure the light yield of luminescence for the particular conditions in neutrino detectors.
Understanding quantum measurement from the solution of dynamical models
Energy Technology Data Exchange (ETDEWEB)
Allahverdyan, Armen E. [Laboratoire de Physique Statistique et Systèmes Complexes, ISMANS, 44 Av. Bartholdi, 72000 Le Mans (France); Balian, Roger [Institut de Physique Théorique, CEA Saclay, 91191 Gif-sur-Yvette cedex (France); Nieuwenhuizen, Theo M., E-mail: T.M.Nieuwenhuizen@uva.nl [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)
2013-04-15
The quantum measurement problem, to wit, understanding why a unique outcome is obtained in each individual experiment, is currently tackled by solving models. After an introduction we review the many dynamical models proposed over the years for elucidating quantum measurements. The approaches range from standard quantum theory, relying for instance on quantum statistical mechanics or on decoherence, to quantum–classical methods, to consistent histories and to modifications of the theory. Next, a flexible and rather realistic quantum model is introduced, describing the measurement of the z-component of a spin through interaction with a magnetic memory simulated by a Curie–Weiss magnet, including N≫1 spins weakly coupled to a phonon bath. Initially prepared in a metastable paramagnetic state, it may transit to its up or down ferromagnetic state, triggered by its coupling with the tested spin, so that its magnetization acts as a pointer. A detailed solution of the dynamical equations is worked out, exhibiting several time scales. Conditions on the parameters of the model are found, which ensure that the process satisfies all the features of ideal measurements. Various imperfections of the measurement are discussed, as well as attempts of incompatible measurements. The first steps consist in the solution of the Hamiltonian dynamics for the spin-apparatus density matrix D{sup -hat} (t). Its off-diagonal blocks in a basis selected by the spin–pointer coupling, rapidly decay owing to the many degrees of freedom of the pointer. Recurrences are ruled out either by some randomness of that coupling, or by the interaction with the bath. On a longer time scale, the trend towards equilibrium of the magnet produces a final state D{sup -hat} (t{sub f}) that involves correlations between the system and the indications of the pointer, thus ensuring registration. Although D{sup -hat} (t{sub f}) has the form expected for ideal measurements, it only describes a large set of
Energy Technology Data Exchange (ETDEWEB)
Rosiles-Perez, C. [Universidad de Guanajuato, Departamento de Quimica, Unidad Pueblito de Rocha, Campus Guanajuato, Cerro de la Venada s/n, Col. Pueblito de Rocha, CP 36040 Guanajuato (Mexico); Lambert, J. [CIATEC, A.C, Omega no. 201 Colonia: Industrial Delta, C.P. 37545 León, Guanajuato (Mexico); Alatorre-Ordaz, A., E-mail: alatorre@ugto.mx [Universidad de Guanajuato, Departamento de Quimica, Unidad Pueblito de Rocha, Campus Guanajuato, Cerro de la Venada s/n, Col. Pueblito de Rocha, CP 36040 Guanajuato (Mexico); Gutierrez, J.A. [Universidad de Guanajuato, Departamento de Quimica, Unidad Pueblito de Rocha, Campus Guanajuato, Cerro de la Venada s/n, Col. Pueblito de Rocha, CP 36040 Guanajuato (Mexico); López-Luke, T. [Centro de Investigaciones en Óptica, A.P. 1-948, León, Gto. 37160 (Mexico); Ramirez-Fuentes, R. [Universidad de Guanajuato, Departamento de Quimica, Unidad Pueblito de Rocha, Campus Guanajuato, Cerro de la Venada s/n, Col. Pueblito de Rocha, CP 36040 Guanajuato (Mexico); Kobayashi, T. [Department of Materials Science and Technology, Nagaoka University of Technology, Kamitomioka, Nagaoka 940-2188 (Japan)
2017-04-15
A series of colloidal quantum dots (QDs) of CdS, ZnS, and the ternary chalcogenide Cd{sub 1−x}Zn{sub x}S were synthesized by a nanoemulsion method, using a sonication probe as shearing power source. Quantum dots with diameters between 4 and 5 nm and cubic crystal structure were obtained and measured by HRTEM and XRD. In all cases, homogeneous solid solutions were obtained, as revealed by Vegard's Law, except with Cd{sub 0.39}Zn{sub 0.61}S. Optical properties of colloidal QDs were measured; the absorption edge is blue shifted, as the content of Zn increases, and showed a quantum confinement. Different emitted colors under UV light was observed, from dark brown with CdS to deep blue with ZnS. QDs of Cd{sub 0.39}Zn{sub 0.61}S show a white photoluminescence. Photoluminescence of the colloidal QDs is due to the combination of the direct band emissions and the trap emissions.
Measuring Charge Carrier Diffusion in Coupled Colloidal Quantum Dot Solids
Zhitomirsky, David
2013-06-25
Colloidal quantum dots (CQDs) are attractive materials for inexpensive, room-temperature-, and solution-processed optoelectronic devices. A high carrier diffusion length is desirable for many CQD device applications. In this work we develop two new experimental methods to investigate charge carrier diffusion in coupled CQD solids under charge-neutral, i.e., undepleted, conditions. The methods take advantage of the quantum-size-effect tunability of our materials, utilizing a smaller-bandgap population of quantum dots as a reporter system. We develop analytical models of diffusion in 1D and 3D structures that allow direct extraction of diffusion length from convenient parametric plots and purely optical measurements. We measure several CQD solids fabricated using a number of distinct methods and having significantly different doping and surface ligand treatments. We find that CQD materials recently reported to achieve a certified power conversion efficiency of 7% with hybrid organic-inorganic passivation have a diffusion length of 80 ± 10 nm. The model further allows us to extract the lifetime, trap density, mobility, and diffusion coefficient independently in each material system. This work will facilitate further progress in extending the diffusion length, ultimately leading to high-quality CQD solid semiconducting materials and improved CQD optoelectronic devices, including CQD solar cells. © 2013 American Chemical Society.
Quantum analysis of the direct measurement of light waves
International Nuclear Information System (INIS)
Saldanha, Pablo L
2014-01-01
In a beautiful experiment performed about a decade ago, Goulielmakis et al (2004 Science 305 1267–69) made a direct measurement of the electric field of light waves. However, they used a laser source to produce the light field, whose quantum state has a null expectation value for the electric field operator, so how was it possible to measure this electric field? Here we present a quantum treatment for the f:2f interferometer used to calibrate the carrier–envelope phase of the light pulses in the experiment. We show how the special nonlinear features of the f:2f interferometer can change the quantum state of the electromagnetic field inside the laser cavity to a state with a definite oscillating electric field, explaining how the ‘classical’ electromagnetic field emerges in the experiment. We discuss that this experiment was, to our knowledge, the first demonstration of an absolute coherent superposition of different photon number states in the optical regime. (paper)
Quantum Jarzynski equality of measurement-based work extraction.
Morikuni, Yohei; Tajima, Hiroyasu; Hatano, Naomichi
2017-03-01
Many studies of quantum-size heat engines assume that the dynamics of an internal system is unitary and that the extracted work is equal to the energy loss of the internal system. Both assumptions, however, should be under scrutiny. In the present paper, we analyze quantum-scale heat engines, employing the measurement-based formulation of the work extraction recently introduced by Hayashi and Tajima [M. Hayashi and H. Tajima, arXiv:1504.06150]. We first demonstrate the inappropriateness of the unitary time evolution of the internal system (namely, the first assumption above) using a simple two-level system; we show that the variance of the energy transferred to an external system diverges when the dynamics of the internal system is approximated to a unitary time evolution. Second, we derive the quantum Jarzynski equality based on the formulation of Hayashi and Tajima as a relation for the work measured by an external macroscopic apparatus. The right-hand side of the equality reduces to unity for "natural" cyclic processes but fluctuates wildly for noncyclic ones, exceeding unity often. This fluctuation should be detectable in experiments and provide evidence for the present formulation.
A measure theoretical approach to quantum stochastic processes
Energy Technology Data Exchange (ETDEWEB)
Waldenfels, Wilhelm von
2014-04-01
Authored by a leading researcher in the field. Self-contained presentation of the subject matter. Examines a number of worked examples in detail. This monograph takes as starting point that abstract quantum stochastic processes can be understood as a quantum field theory in one space and in one time coordinate. As a result it is appropriate to represent operators as power series of creation and annihilation operators in normal-ordered form, which can be achieved using classical measure theory. Considering in detail four basic examples (e.g. a two-level atom coupled to a heat bath of oscillators), in each case the Hamiltonian of the associated one-parameter strongly continuous group is determined and the spectral decomposition is explicitly calculated in the form of generalized eigen-vectors. Advanced topics include the theory of the Hudson-Parthasarathy equation and the amplified oscillator problem. To that end, a chapter on white noise calculus has also been included.
A measure theoretical approach to quantum stochastic processes
Von Waldenfels, Wilhelm
2014-01-01
This monograph takes as starting point that abstract quantum stochastic processes can be understood as a quantum field theory in one space and in one time coordinate. As a result it is appropriate to represent operators as power series of creation and annihilation operators in normal-ordered form, which can be achieved using classical measure theory. Considering in detail four basic examples (e.g. a two-level atom coupled to a heat bath of oscillators), in each case the Hamiltonian of the associated one-parameter strongly continuous group is determined and the spectral decomposition is explicitly calculated in the form of generalized eigen-vectors. Advanced topics include the theory of the Hudson-Parthasarathy equation and the amplified oscillator problem. To that end, a chapter on white noise calculus has also been included.
DEFF Research Database (Denmark)
Ploquin, N.; Kertzscher Schwencke, Gustavo Adolfo Vladimir; Vandervoort, E.
2012-01-01
from 5 to 60 mm. ROFs were also measured using a mobileMOSFET system (Best Medical Canada) and EBT1 and EBT2 GAFCHROMIC® (ISP, Ashland) radiochromic films. For cone sizes 12.5–60 mm all detector results were in agreement within the measurement uncertainty. The microMOSFET/RADPOS measurements (published.......3% and 0.865 ± 0.3% for 5, 7.5 and 10 mm cones. Our study shows that the microMOSFET/RADPOS and optical fiber‐coupled RL dosimetry system are well suited for Cyberknife cone output factors measurements over the entire range of field sizes, provided that appropriate correction factors are applied...
Entanglement measures in embedding quantum simulators with nuclear spins
Xin, Tao; Pedernales, Julen S.; Solano, Enrique; Long, Gui-Lu
2018-02-01
We implement an embedding quantum simulator (EQS) in nuclear spin systems. The experiment consists of a simulator of up to three qubits, plus a single ancillary qubit, where we are able to efficiently measure the concurrence and the three-tangle of two-qubit and three-qubit systems as they undergo entangling dynamics. The EQS framework allows us to drastically reduce the number of measurements needed for this task, which otherwise would require full-state reconstruction of the qubit system. Our simulator is built of the nuclear spins of four 13C atoms in a molecule of trans-crotonic acid manipulated with NMR techniques.
DEFF Research Database (Denmark)
Wu, Shengjun; Poulsen, Uffe Vestergaard; Mølmer, Klaus
2009-01-01
and the classical correlations and we relate our quantitative finding to the so-called classical correlation locked in a quantum state. We derive upper bounds for the sum of classical correlation obtained by measurements in different mutually unbiased bases and we show that the complementarity gap is also present......We consider the classical correlations that two observers can extract by measurements on a bipartite quantum state and we discuss how they are related to the quantum mutual information of the state. We show with several examples how complementarity gives rise to a gap between the quantum...... in the deterministic quantum computation with one quantum bit....
Luminescent properties of fluorophosphate glasses with lead chalcogenides molecular clusters
International Nuclear Information System (INIS)
Kolobkova, E.V.; Kukushkin, D.S.; Nikonorov, N.V.; Shakhverdov, T.A.; Sidorov, A.I.; Vasiliev, V.N.
2015-01-01
Fluorophosphate glasses containing lead, selenium, and sulfur exhibit an intense luminescence in the 400–620 nm spectral region when excited by the 240–420 nm radiation. This luminescence is due to the presence of (PbSe) n and/or (PbS) n molecular clusters in the glasses, which appear in the as-prepared glasses before quantum dots formation. The thermal treatment at temperatures less than the glass transition temperature results in the red-shift of the luminescence bands and in an increase in the luminescence intensity. Heating the thermally treated glass samples leads to the reversible thermal quenching of the luminescence. - Highlights: • Fluorophosphate glasses with Pb, Se, and S ions contain (PbSe) n or (PbS) n molecular clusters. • (PbSe) n and (PbS) n molecular clusters possess luminescence in the visible with UV excitation. • Heating the glass leads to the reversible thermal quenching of the luminescence
Strong Measurements Give a Better Direct Measurement of the Quantum Wave Function.
Vallone, Giuseppe; Dequal, Daniele
2016-01-29
Weak measurements have thus far been considered instrumental in the so-called direct measurement of the quantum wave function [4J. S. Lundeen, Nature (London) 474, 188 (2011).]. Here we show that a direct measurement of the wave function can be obtained by using measurements of arbitrary strength. In particular, in the case of strong measurements, i.e., those in which the coupling between the system and the measuring apparatus is maximum, we compared the precision and the accuracy of the two methods, by showing that strong measurements outperform weak measurements in both for arbitrary quantum states in most cases. We also give the exact expression of the difference between the original and reconstructed wave function obtained by the weak measurement approach; this will allow one to define the range of applicability of such a method.
Indirect and two fold measurements in quantum mechanics
International Nuclear Information System (INIS)
Fer, Francis
1981-01-01
Keeping strictly in the positivist, probabilistic and hilbertian frame of quantum mechanics, the author develops a criticism of the accepted theory of indirect and twofold measurements. He shows that this theory cannot logically derive from the usual axiomatics, namely from the so-called reduction-of-state axiom. He proposes a modified statement (already used sometimes) of this axiom, which leads to a reliable theory of indirect and twofold measurements. The results are particularly: a) that a measurement made on a sub-system does not modify the mathematical representation of the complementary system, nor its prior probability distributions; b) that measurement is nothing else than an information which enables to correct the probabilities of further measurements according to the classical rules of the calculus of probabilities [fr
Reconsideration of the Uncertainty Relations and Quantum Measurements
Directory of Open Access Journals (Sweden)
Dumitru S.
2008-04-01
Full Text Available Discussions on uncertainty relations (UR and quantum measurements (QMS persisted until nowadays in publications about quantum mechanics (QM. They originate mainly from the conventional interpretation of UR (CIUR. In the most of the QM literarure, it is underestimated the fact that, over the years, a lot of deficiencies regarding CIUR were signaled. As a rule the alluded deficiencies were remarked disparately and discussed as punctual and non-essential questions. Here we approach an investigation of the mentioned deficiencies collected in a conclusive ensemble. Subsequently we expose a reconsideration of the major problems referring to UR and QMS. We reveal that all the basic presumption of CIUR are troubled by insurmountable deficiencies which require the indubitable failure of CIUR and its necessary abandonment. Therefore the UR must be deprived of their statute of crucialpieces for physics. So, the aboriginal versions of UR appear as being in postures of either (i thought-experimental fictions or (ii simple QM formulae and, any other versions of them, have no connection with the QMS. Then the QMS must be viewed as an additional subject comparatively with the usual questions of QM. For a theoretical description of QMS we propose an information-transmission model, in which the quantum observables are considered as random variables. Our approach directs to natural solutions and simplifications for many problems regarding UR and QMS.
Two path transport measurements on a triple quantum dot
Energy Technology Data Exchange (ETDEWEB)
Rogge, Maximilian C.; Haug, Rolf J. [Institut fuer Festkoerperphysik, Leibniz Universitaet Hannover, Appelstr. 2, 30167 Hannover (Germany)
2008-07-01
We present a novel triple quantum dot device made with local anodic oxidation on a GaAs/AlGaAs heterostructure. The geometry provides two path transport via a three lead setup with each lead connected to one of the three quantum dots. In addition charge detection is implemented via a quantum point contact. One lead is used as a common source contact, the other two are used as two separate drain contacts with independent current measurement. Thus two paths are formed with two dots in each path. Along both paths serial transport is observed at the triple points of the two corresponding dots. With four side gates a wide tunability is given. Thus the system can be tuned in and out of triple dot resonances. When all three dots come into resonance, quadruple points are formed with simultaneous transport along both paths. The data are analysed in combined two colour plots and compared to the charge detection showing sets of three different lines, one for each dot. This way the two path setup allows to investigate the transition from double dot physics to triple dot physics.
Reconsideration of the Uncertainty Relations and Quantum Measurements
Directory of Open Access Journals (Sweden)
Dumitru S.
2008-04-01
Full Text Available Discussions on uncertainty relations (UR and quantum measurements (QMS persisted until nowadays in publications about quantum mechanics (QM. They originate mainly from the conventional interpretation of UR (CIUR. In the most of the QM literarure, it is underestimated the fact that, over the years, a lot of deficiencies regarding CIUR were signaled. As a rule the alluded deficiencies were remarked disparately and dis- cussed as punctual and non-essential questions. Here we approach an investigation of the mentioned deficiencies collected in a conclusive ensemble. Subsequently we expose a reconsideration of the major problems referring to UR and QMS. We reveal that all the basic presumption of CIUR are troubled by insurmountable deficiencies which require the indubitable failure of CIUR and its necessary abandonment. Therefore the UR must be deprived of their statute of crucial pieces for physics. So, the aboriginal versions of UR appear as being in postures of either (i thought-experimental fictions or (ii sim- ple QM formulae and, any other versions of them, have no connection with the QMS. Then the QMS must be viewed as an additional subject comparatively with the usual questions of QM. For a theoretical description of QMS we propose an information- transmission model, in which the quantum observables are considered as random vari- ables. Our approach directs to natural solutions and simplifications for many problems regarding UR and QMS.
Discuss on luminescence dose data analysis technology
International Nuclear Information System (INIS)
Ma Xinhua; Xiao Wuyun; Ai Xianyun; Shi Zhilan; Liu Ying
2009-01-01
This article describes the development of luminescence dose data measurement and processing technology. General design planning of luminescence dose data measurement and processing technology is put forward with the diverse demands. The emphasis is focused on dose data processing method, luminescence curve analysis method, using of network, mechanics of communication among computers, data base management system of individual dose in this paper. The main methods and skills used in this technology as well as their advantages are also discussed. And it offers general design references for development luminescence dose data processing software. (authors)
Energy Technology Data Exchange (ETDEWEB)
Adegoke, Oluwasesan [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Hosten, Eric; McCleland, Cedric [Department of Chemistry, Nelson Mandela Metropolitan University (South Campus), Port Elizabeth 6031 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)
2012-04-06
Graphical abstract: A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery. Highlights: Black-Right-Pointing-Pointer Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. Black-Right-Pointing-Pointer Quantum dots fluorescence is quenched by the radical. Black-Right-Pointing-Pointer In the presence of bromide ions the fluorescence is restored. Black-Right-Pointing-Pointer The sensor is more selective to bromine ions than other common ions. - Abstract: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 {mu}M. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
Quantum measurement and the mind-brain connection
International Nuclear Information System (INIS)
Stapp, H.P.
1990-01-01
It is argued that quantum measurements do pose a problem, within the context created by the fundamental aim of science, which is identified as the construction of a cohesive, comprehensive, and rationally coherent idea of the nature of the world in which we live. Models of nature are divided into two classes: (1), those in which there is a selection process that, for any possible measurement, would, if that measurement were to be performed, pick out one single outcome, and, (2), all others. It is proved that any model of class that reproduces the predictions of quantum theory must violate the condition that there be no faster-than-light influences of any kind. This result is used to motivate the study of models in which unitary evolution is maintained and there is no selection of unique outcomes. A consideration of ontic probabilities, historical records, and the form of the mind-brain connection leads to an elaboration of the Everett many-worlds interpretation that appears to provide the basis of satisfactory solution of the measurement problem. 18 refs
S.I.A. Bodmer (Sander I. A.); G. Balestra (Gianmarco); F.A. Harms (Floor A.); T. Johannes (Tanja); N.J.H. Raat (Nicolaas); R.J. Stolker (Robert); E.G. Mik (Egbert)
2012-01-01
textabstractMeasurement of tissue oxygenation is a complex task and various techniques have led to a wide range of tissue PO 2 values and contradictory results. Tissue is compartmentalized in microcirculation, interstitium and intracellular space and current techniques are biased towards a certain
A new sensitive system for measurement of thermally and optically stimulated luminescence
DEFF Research Database (Denmark)
Markey, B.G.; Bøtter-Jensen, L.; Poolton, N.R.J.
1996-01-01
optics of the system with a combination of ellipsoidal mirrors and light guides, which also serve to make the system more flexible in choice of excitation source when OSL measurements are required. A variety of new light sources might be employed, adapted to allow the most efficient wavelengths...
Direct quantum process tomography via measuring sequential weak values of incompatible observables.
Kim, Yosep; Kim, Yong-Su; Lee, Sang-Yun; Han, Sang-Wook; Moon, Sung; Kim, Yoon-Ho; Cho, Young-Wook
2018-01-15
The weak value concept has enabled fundamental studies of quantum measurement and, recently, found potential applications in quantum and classical metrology. However, most weak value experiments reported to date do not require quantum mechanical descriptions, as they only exploit the classical wave nature of the physical systems. In this work, we demonstrate measurement of the sequential weak value of two incompatible observables by making use of two-photon quantum interference so that the results can only be explained quantum physically. We then demonstrate that the sequential weak value measurement can be used to perform direct quantum process tomography of a qubit channel. Our work not only demonstrates the quantum nature of weak values but also presents potential new applications of weak values in analyzing quantum channels and operations.
International Nuclear Information System (INIS)
Lu, C.-I.
1982-01-01
Luminescent screens which are useful for such purposes as intensifying screens for radiographs are comprised of a support bearing a layer of finely divided particles of a phosphor dispersed in a cross-linked polymeric matrix formed by heat-curing of a coating composition comprising an unsaturated cross-linkable polymer, a polymerizable acrylic monomer, a thermoplastic polyurethane elastomer, and a heat-activatable polymerization initiator. The phosphor layer includes voids formed by evaporation of an evaporable component which is present in the coating composition from which such layer is formed. (author)
Measuring the scale parameter of quantum chromodynamics at CHEER
International Nuclear Information System (INIS)
Krauss, L.M.
1981-01-01
The possibility of measuring the scale parameter of quantum chromodynamics, Λsub(s), at CHEER is discussed. Rationale for the measurement of this quantity are given, along with a discussion of the theoretical difficulties involved. The meaurement of the Q 2 dependence of structure functions and their moments, and methods of measuring αsub(s) and its Q 2 evolution, are discussed, and arguments are given for the advantages and disadvantages of going to high Q 2 values at CHEER. It is concluded that while sensitivity to Λ is lowered at high Q 2 , CHEER will, in principle, be able to provide the first clean measurements of Λ, free from almost all the theoretical confusion involved in interpretations of present data
Radiation doses measured by TLD (thermo luminescent dosimeter) in x-ray examination
International Nuclear Information System (INIS)
Yamamoto, Seiichi; Hiraki, Motoji; Murakami, Shozo; Nishikawa, Naozo; Yagi, Takayuki
1977-01-01
By means of TLD, we measured the radiation doses to the skin in the central area of the field of radiation and doses scattered outside of the radiation field, utilizing a phantom to define a suitable radiation field. Clinically, when radiography of the gall bladder and the chest was done, we measured both the radiation doses of the central skin area where radiation was done and the skin above the area of the female gonads. In radiography of the chest, the radiation doses to the skin area above the female gonads situate was under 0.1 mR. When female gonads are less than 15 cm from the margin of the radiation field of the radiation dose can be decreased by 30% if gum sheets containing lead are used to cover the skin area outside the radiation field. (auth.)
Luminescence properties of some food dye-stuffs
International Nuclear Information System (INIS)
Astanov, S.Kh.; Muminova, Z.A.; Urunov, R.G.
2004-01-01
The luminescence properties of the natural food dye-stuffs and vitamins in temperature range of 300-5.2 K are studied. On the basis of experimental data on quantum yields of the fluorescence, trans-cis-isomerization and luminescence of the molecular oxygen the main ways of the inactivation of electronic excitations in researching compounds have been defined. (author)
Upper bounds on quantum uncertainty products and complexity measures
Energy Technology Data Exchange (ETDEWEB)
Guerrero, Angel; Sanchez-Moreno, Pablo; Dehesa, Jesus S. [Department of Atomic, Molecular and Nuclear Physics, University of Granada, Granada (Spain); Department of Applied Mathematics, University of Granada, Granada (Spain) and Institute Carlos I for Computational and Theoretical Physics, University of Granada, Granada (Spain); Department of Atomic, Molecular and Nuclear Physics, University of Granada, Granada (Spain); Institute Carlos I for Computational and Theoretical Physics, University of Granada, Granada (Spain)
2011-10-15
The position-momentum Shannon and Renyi uncertainty products of general quantum systems are shown to be bounded not only from below (through the known uncertainty relations), but also from above in terms of the Heisenberg-Kennard product . Moreover, the Cramer-Rao, Fisher-Shannon, and Lopez-Ruiz, Mancini, and Calbet shape measures of complexity (whose lower bounds have been recently found) are also bounded from above. The improvement of these bounds for systems subject to spherically symmetric potentials is also explicitly given. Finally, applications to hydrogenic and oscillator-like systems are done.
Decoherence assisting a measurement-driven quantum evolution process
International Nuclear Information System (INIS)
Roa, Luis; Olivares-Renteria, G. A.
2006-01-01
We study the problem of driving an unknown initial mixed quantum state onto a known pure state without using unitary transformations. This can be achieved, in an efficient manner, with the help of sequential measurements on at least two unbiased bases. However here we found that, when the system is affected by a decoherence mechanism, only one observable is required in order to achieve the same goal. In this way the decoherence can assist the process. We show that, depending on the sort of decoherence, the process can converge faster or slower than the method implemented by means of two complementary observables
Measurement and Quantum State Transfer in Superconducting Qubits
Mlinar, Eric
The potential of superconducting qubits as the medium for a scalable quantum computer has motivated the pursuit of improved interactions within this system. Two challenges for the field of superconducting qubits are measurement fidelity, to accurately determine the state of the qubit, and the efficient transfer of quantum states. In measurement, the current state-of-the-art method employs dispersive readout, by coupling the qubit to a cavity and reading the resulting shift in cavity frequency to infer the qubit's state; however, this is vulnerable to Purcell relaxation, as well as being modeled off a simplified two-level abstraction of the qubit. In state transfer, the existing proposal for moving quantum states is mostly untested against non-idealities that will likely be present in an experiment. In this dissertation, we examine three problems within these two areas. We first describe a new scheme for fast and high-fidelity dispersive measurement specifically designed to circumvent the Purcell Effect. To do this, the qubit-resonator interaction is turned on only when the resonator is decoupled from the environment; then, after the resonator state has shifted enough to infer the qubit state, the qubit-resonator interaction is turned off before the resonator and environment are recoupled. We also show that the effectiveness of this "Catch-Disperse-Release'' procedure partly originates from quadrature squeezing of the resonator state induced by the Jaynes-Cummings nonlinearity. The Catch-Disperse-Release measurement scheme treats the qubit as a two-level system, which is a common simplification used in theoretical works. However, the most promising physical candidate for a superconducting qubit, the transmon, is a multi-level system. In the second work, we examine the effects of including the higher energy levels of the transmon. Specifically, we expand the eigenstate picture developed in the first work to encompass multiple qubit levels, and examine the resulting
International Nuclear Information System (INIS)
Daoud, M.; Ahl Laamara, R.
2012-01-01
We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl–Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger–Horne–Zeilinger states. -- Highlights: ► Pairwise quantum correlations multipartite coherent states. ► Explicit expression of geometric quantum discord. ► Entanglement sudden death and quantum discord robustness. ► Generalized coherent states interpolating between Werner and Greenberger–Horne–Zeilinger states
Energy Technology Data Exchange (ETDEWEB)
Daoud, M., E-mail: m_daoud@hotmail.com [Department of Physics, Faculty of Sciences, University Ibnou Zohr, Agadir (Morocco); Ahl Laamara, R., E-mail: ahllaamara@gmail.com [LPHE-Modeling and Simulation, Faculty of Sciences, University Mohammed V, Rabat (Morocco); Centre of Physics and Mathematics, CPM, CNESTEN, Rabat (Morocco)
2012-07-16
We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl–Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger–Horne–Zeilinger states. -- Highlights: ► Pairwise quantum correlations multipartite coherent states. ► Explicit expression of geometric quantum discord. ► Entanglement sudden death and quantum discord robustness. ► Generalized coherent states interpolating between Werner and Greenberger–Horne–Zeilinger states.
Noninvasive Quantum Measurement of Arbitrary Operator Order by Engineered Non-Markovian Detectors
Bülte, Johannes; Bednorz, Adam; Bruder, Christoph; Belzig, Wolfgang
2018-04-01
The development of solid-state quantum technologies requires the understanding of quantum measurements in interacting, nonisolated quantum systems. In general, a permanent coupling of detectors to a quantum system leads to memory effects that have to be taken into account in interpreting the measurement results. We analyze a generic setup of two detectors coupled to a quantum system and derive a compact formula in the weak-measurement limit that interpolates between an instantaneous (text-book type) and almost continuous—detector dynamics-dependent—measurement. A quantum memory effect that we term "system-mediated detector-detector interaction" is crucial to observe noncommuting observables simultaneously. Finally, we propose a mesoscopic double-dot detector setup in which the memory effect is tunable and that can be used to explore the transition to non-Markovian quantum measurements experimentally.
Quantitative luminescence imaging system
Erwin, David N.; Kiel, Johnathan L.; Batishko, Charles R.; Stahl, Kurt A.
1990-01-01
The QLIS images and quantifies low-level chemiluminescent reactions in an electromagnetic field. It is capable of real time nonperturbing measurement and simultaneous recording of many biochemical and chemical reactions such as luminescent immunoassays or enzyme assays. The system comprises image transfer optics, a low-light level digitizing camera with image intensifying microchannel plates, an image process or, and a control computer. The image transfer optics may be a fiber image guide with a bend, or a microscope, to take the light outside of the RF field. Output of the camera is transformed into a localized rate of cumulative digitalized data or enhanced video display or hard-copy images. The system may be used as a luminescent microdosimetry device for radiofrequency or microwave radiation, as a thermal dosimeter, or in the dosimetry of ultra-sound (sonoluminescence) or ionizing radiation. It provides a near-real-time system capable of measuring the extremely low light levels from luminescent reactions in electromagnetic fields in the areas of chemiluminescence assays and thermal microdosimetry, and is capable of near-real-time imaging of the sample to allow spatial distribution analysis of the reaction. It can be used to instrument three distinctly different irradiation configurations, comprising (1) RF waveguide irradiation of a small Petri-dish-shaped sample cell, (2) RF irradiation of samples in a microscope for the microscopie imaging and measurement, and (3) RF irradiation of small to human body-sized samples in an anechoic chamber.
Baianu, IC
2004-01-01
Two important concepts for nanoscience and nanotechnology-- the quantum automaton and quantum computation--were introduced in the context of quantum genetics and complex genetic networks with nonlinear dynamics. In previous publications (Baianu,1971a, b) the formal definition of quantum automaton was initially presented in the Schrodinger representation of quantum mechanics, and several possible implications for genetic processes and metabolic activities in living cells and organisms were considered. This was followed by reports on quantum, as well as symbolic, abstract computations based on the theory of categories, functors and natural transformations (Baianu,1971b; 1977; 1987; 2004; Baianu et al, 2004). The notions of quantum topological semigroup, quantum automaton, and/or quantum computer, were then suggested with a view to their potential applications to the analogous simulation of biological systems, and especially genetic activities and nonlinear dynamics in genetic networks. A representation of inter...
DEFF Research Database (Denmark)
Jain, M.; Murray, A.S.; Bøtter-Jensen, L.
2003-01-01
-aliquot dose-evaluation protocols seem to be relatively free of complications when applied to quartz dominated by the fast OSL component coming from 325degreesC TL region, but this may not be true for quartz in which other components are more significant. An adequate understanding of how different OSL...... results from measurement of (a) sensitisation, (b) thermal stability, (c) recuperation, and (d) infrared response as a function of stimulation temperature from 3 different samples of sedimentary quartz selected on the basis of relative OSL contribution from different blue light stimulated linearly...
Adaptive phase measurements in linear optical quantum computation
International Nuclear Information System (INIS)
Ralph, T C; Lund, A P; Wiseman, H M
2005-01-01
Photon counting induces an effective non-linear optical phase shift in certain states derived by linear optics from single photons. Although this non-linearity is non-deterministic, it is sufficient in principle to allow scalable linear optics quantum computation (LOQC). The most obvious way to encode a qubit optically is as a superposition of the vacuum and a single photon in one mode-so-called 'single-rail' logic. Until now this approach was thought to be prohibitively expensive (in resources) compared to 'dual-rail' logic where a qubit is stored by a photon across two modes. Here we attack this problem with real-time feedback control, which can realize a quantum-limited phase measurement on a single mode, as has been recently demonstrated experimentally. We show that with this added measurement resource, the resource requirements for single-rail LOQC are not substantially different from those of dual-rail LOQC. In particular, with adaptive phase measurements an arbitrary qubit state α vertical bar 0>+β vertical bar 1> can be prepared deterministically
Luo, Shiming; Xing, Da; Zhou, Jing; Qin, Yanfang; Chen, Qun
2005-04-01
Photodynamic therapy (PDT) is a cancer therapy that utilizes optical energy to activate a photosensitizer drug in a target tissue. Reactive oxygen species (ROS), such as 1O2 and superoxide, are believed to be the major cytotoxic agents involved in PDT. Although current PDT dosimetry mostly involves measurements of light and photosensitizer doses delivered to a patient, the quantification of ROS production during a treatment would be the ultimate dosimetry of PDT. Technically, it is very difficult and expensive to directly measure the fluorescence from 1O2, due to its extreme short lifetime and weak signal strength. In this paper, Photofrin(R) and 635nm laser were used to generate 1O2 and superoxide in a PDT in solution. Compound 3,7- dihydro-6-{4-[2-(N"-(5-fluoresceinyl) thioureido) ethoxy] phenyl}-2- methylimidazo{1,2-a} pyrazin-3-one sodium salt,an Cyp- ridina luciferin analog commonly referred as FCLA, was used as a chemical reporter of ROS. The 532nm chemiluminescence (CL) from the reaction of the FCLA and ROS was detected with a photon multiplier tube (PMT) system operating at single photon counting mode. With the setup, we have made detections of ROS generated by PDT in real time. By varying the amount of conventional PDT dosage (photosensitizer concentration, light irradiation fluence and its delivery rate) and the amount of FCLA, the intensity of CL and its consumption rate were investigated. The results show that the intensity and temporal profile of CL are highly related to the PDT treatment parameters. This suggests that FCLA CL may provide a highly potential alternative for ROS detection during PDT.
Using measurement-induced disturbance to characterize correlations as classical or quantum
International Nuclear Information System (INIS)
Luo Shunlong
2008-01-01
In contrast to the seminal entanglement-separability paradigm widely used in quantum information theory, we introduce a quantum-classical dichotomy in order to classify and quantify statistical correlations in bipartite states. This is based on the idea that while in the classical description of nature measurements can be carried out without disturbance, in the quantum description, generic measurements often disturb the system and the disturbance can be exploited to quantify the quantumness of correlations therein. It turns out that certain separable states still possess correlations of a quantum nature and indicates that quantum correlations are more general than entanglement. The results are illustrated in the Werner states and the isotropic states, and are applied to quantify the quantum advantage of the model of quantum computation proposed by Knill and Laflamme [Phys. Rev. Lett. 81, 5672 (1998)
Quantum Entanglement: Separability, Measure, Fidelity of Teleportation, and Distillation
Directory of Open Access Journals (Sweden)
Ming Li
2010-01-01
Full Text Available Quantum entanglement plays crucial roles in quantum information processing. Quantum entangled states have become the key ingredient in the rapidly expanding field of quantum information science. Although the nonclassical nature of entanglement has been recognized for many years, considerable efforts have been taken to understand and characterize its properties recently. In this review, we introduce some recent results in the theory of quantum entanglement. In particular separability criteria based on the Bloch representation, covariance matrix, normal form and entanglement witness, lower bounds, subadditivity property of concurrence and tangle, fully entangled fraction related to the optimal fidelity of quantum teleportation, and entanglement distillation will be discussed in detail.
International Nuclear Information System (INIS)
Endo, T.; Murayama, Y.; Sakamoto, Y.; Sakuraba, T.; Shiota, F.
1989-01-01
A series of systems composed of cryogenic devices such as a Josephson potentiometer and a cryogenic current comparator has been proposed and developed to precisely measure a current with any value up to 1 A. These systems will be used to measure the injected electrical energy with an uncertainty of the order of 0.01 ppm or less in the absolute measurement of the magnetic flux quantum by superconducting magnetic levitation. Some preliminary experiments are described
Generalized flow and determinism in measurement-based quantum computation
Energy Technology Data Exchange (ETDEWEB)
Browne, Daniel E [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Kashefi, Elham [Computing Laboratory and Christ Church College, University of Oxford, Parks Road, Oxford OX1 3QD (United Kingdom); Mhalla, Mehdi [Laboratoire d' Informatique de Grenoble, CNRS - Centre national de la recherche scientifique, Universite de Grenoble (France); Perdrix, Simon [Preuves, Programmes et Systemes (PPS), Universite Paris Diderot, Paris (France)
2007-08-15
We extend the notion of quantum information flow defined by Danos and Kashefi (2006 Phys. Rev. A 74 052310) for the one-way model (Raussendorf and Briegel 2001 Phys. Rev. Lett. 86 910) and present a necessary and sufficient condition for the stepwise uniformly deterministic computation in this model. The generalized flow also applied in the extended model with measurements in the (X, Y), (X, Z) and (Y, Z) planes. We apply both measurement calculus and the stabiliser formalism to derive our main theorem which for the first time gives a full characterization of the stepwise uniformly deterministic computation in the one-way model. We present several examples to show how our result improves over the traditional notion of flow, such as geometries (entanglement graph with input and output) with no flow but having generalized flow and we discuss how they lead to an optimal implementation of the unitaries. More importantly one can also obtain a better quantum computation depth with the generalized flow rather than with flow. We believe our characterization result is particularly valuable for the study of the algorithms and complexity in the one-way model.
Measure theoretical approach to recurrent properties for quantum dynamics
Energy Technology Data Exchange (ETDEWEB)
Otobe, Yoshiki [Department of Mathematical Sciences, Shinshu University, Asahi 3-1-1, Matsumoto 390-8621 (Japan); Sasaki, Itaru, E-mail: otobe@math.shinshu-u.ac.jp, E-mail: isasaki@shinshu-u.ac.jp [Fiber-Nanotech Young Researcher Empowerment Center, Shinshu University, Asahi 3-1-1, Matsumoto 390-8621 (Japan)
2011-11-18
Poincare's recurrence theorem, which states that every Hamiltonian dynamics enclosed in a finite volume returns to its initial position as close as one wishes, is a mathematical basis of statistical mechanics. It is Liouville's theorem that guarantees that the dynamics preserves the volume on the state space. A quantum version of Poincare's theorem was obtained in the middle of the 20th century without any volume structures of the state space (Hilbert space). One of our aims in this paper is to establish such properties of quantum dynamics from an analog of Liouville's theorem, namely, we will construct a natural probability measure on the Hilbert space from a Hamiltonian defined on the space. Then we will show that the measure is invariant under the corresponding Schroedinger flow. Moreover, we show that the dynamics naturally causes an infinite-dimensional Weyl transformation. It also enables us to discuss the ergodic properties of such dynamics. (paper)
Model for calorimetric measurements in an open quantum system
Donvil, Brecht; Muratore-Ginanneschi, Paolo; Pekola, Jukka P.; Schwieger, Kay
2018-05-01
We investigate the experimental setup proposed in New J. Phys. 15, 115006 (2013), 10.1088/1367-2630/15/11/115006 for calorimetric measurements of thermodynamic indicators in an open quantum system. As a theoretical model we consider a periodically driven qubit coupled with a large yet finite electron reservoir, the calorimeter. The calorimeter is initially at equilibrium with an infinite phonon bath. As time elapses, the temperature of the calorimeter varies in consequence of energy exchanges with the qubit and the phonon bath. We show how under weak-coupling assumptions, the evolution of the qubit-calorimeter system can be described by a generalized quantum jump process including as dynamical variable the temperature of the calorimeter. We study the jump process by numeric and analytic methods. Asymptotically with the duration of the drive, the qubit-calorimeter attains a steady state. In this same limit, we use multiscale perturbation theory to derive a Fokker-Planck equation governing the calorimeter temperature distribution. We inquire the properties of the temperature probability distribution close and at the steady state. In particular, we predict the behavior of measurable statistical indicators versus the qubit-calorimeter coupling constant.
Generalized flow and determinism in measurement-based quantum computation
International Nuclear Information System (INIS)
Browne, Daniel E; Kashefi, Elham; Mhalla, Mehdi; Perdrix, Simon
2007-01-01
We extend the notion of quantum information flow defined by Danos and Kashefi (2006 Phys. Rev. A 74 052310) for the one-way model (Raussendorf and Briegel 2001 Phys. Rev. Lett. 86 910) and present a necessary and sufficient condition for the stepwise uniformly deterministic computation in this model. The generalized flow also applied in the extended model with measurements in the (X, Y), (X, Z) and (Y, Z) planes. We apply both measurement calculus and the stabiliser formalism to derive our main theorem which for the first time gives a full characterization of the stepwise uniformly deterministic computation in the one-way model. We present several examples to show how our result improves over the traditional notion of flow, such as geometries (entanglement graph with input and output) with no flow but having generalized flow and we discuss how they lead to an optimal implementation of the unitaries. More importantly one can also obtain a better quantum computation depth with the generalized flow rather than with flow. We believe our characterization result is particularly valuable for the study of the algorithms and complexity in the one-way model
Entanglement entropy after selective measurements in quantum chains
Energy Technology Data Exchange (ETDEWEB)
Najafi, Khadijeh [Department of Physics, Georgetown University,37th and O Sts. NW, Washington, DC 20057 (United States); Rajabpour, M.A. [Instituto de Física, Universidade Federal Fluminense,Av. Gal. Milton Tavares de Souza s/n, Gragoatá, 24210-346, Niterói, RJ (Brazil)
2016-12-22
We study bipartite post measurement entanglement entropy after selective measurements in quantum chains. We first study the quantity for the critical systems that can be described by conformal field theories. We find a connection between post measurement entanglement entropy and the Casimir energy of floating objects. Then we provide formulas for the post measurement entanglement entropy for open and finite temperature systems. We also comment on the Affleck-Ludwig boundary entropy in the context of the post measurement entanglement entropy. Finally, we also provide some formulas regarding modular hamiltonians and entanglement spectrum in the after measurement systems. After through discussion regarding CFT systems we also provide some predictions regarding massive field theories. We then discuss a generic method to calculate the post measurement entanglement entropy in the free fermion systems. Using the method we study the post measurement entanglement entropy in the XY spin chain. We check numerically the CFT and the massive field theory results in the transverse field Ising chain and the XX model. In particular, we study the post meaurement entanglement entropy in the infinite, periodic and open critical transverse field Ising chain and the critical XX model. The effect of the temperature and the gap is also discussed in these models.
Entanglement entropy after selective measurements in quantum chains
International Nuclear Information System (INIS)
Najafi, Khadijeh; Rajabpour, M.A.
2016-01-01
We study bipartite post measurement entanglement entropy after selective measurements in quantum chains. We first study the quantity for the critical systems that can be described by conformal field theories. We find a connection between post measurement entanglement entropy and the Casimir energy of floating objects. Then we provide formulas for the post measurement entanglement entropy for open and finite temperature systems. We also comment on the Affleck-Ludwig boundary entropy in the context of the post measurement entanglement entropy. Finally, we also provide some formulas regarding modular hamiltonians and entanglement spectrum in the after measurement systems. After through discussion regarding CFT systems we also provide some predictions regarding massive field theories. We then discuss a generic method to calculate the post measurement entanglement entropy in the free fermion systems. Using the method we study the post measurement entanglement entropy in the XY spin chain. We check numerically the CFT and the massive field theory results in the transverse field Ising chain and the XX model. In particular, we study the post meaurement entanglement entropy in the infinite, periodic and open critical transverse field Ising chain and the critical XX model. The effect of the temperature and the gap is also discussed in these models.
Scintillation properties of quantum-dot doped styrene based plastic scintillators
International Nuclear Information System (INIS)
Park, J.M.; Kim, H.J.; Hwang, Y.S.; Kim, D.H.; Park, H.W.
2014-01-01
We fabricated quantum-dot doped plastic scintillators in order to control the emission wavelength. We studied the characterization of the quantum-dots (CdSe/ZnS) and PPO (2, 5-diphenyloxazole) doped styrene based plastic scintillators. PPO is usually used as a dopant to enhance the scintillation properties of organic scintillators with a maximum emission wavelength of 380 nm. In order to study the scintillation properties of the quantum-dots doped plastic scintillators, the samples were irradiated with X-ray, photon, and 45 MeV proton beams. We observed that only PPO doped plastic scintillators shows a luminescence peak around 380 nm. However, both the quantum-dots and PPO doped plastic scintillators shows luminescence peaks around 380 nm and 520 nm. Addition of quantum-dots had shifted the luminescence spectrum from 380 nm (PPO) toward the region of 520 nm (Quantum-dots). Emissions with wavelength controllable plastic scintillators can be matched to various kinds of photosensors such as photomultiplier tubes, photo-diodes, avalanche photo-diodes, and CCDs, etc. Also quantum-dots doped plastic scintillator, which is irradiated 45 MeV proton beams, shows that the light yield of quantum-dots doped plastic scintillator is increases as quantum-dots doping concentration increases at 520 nm. And also the plastic scintillators were irradiated with Cs-137 γ-ray for measuring fluorescence decay time. -- Highlights: • Quantum-dot doped plastic scintillator is grown by the thermal polymerization method. • Quantum-dot doped plastic scintillators can control the emission wavelength to match with photo-sensor. • Quantum-dots and PPO doped plastic scintillators emitted luminescence peaks around 380 nm and 520 nm. • We observed the energy transfer from PPO to quantum-dot in the quantum-dot doped plastic scintillator
Scintillation properties of quantum-dot doped styrene based plastic scintillators
Energy Technology Data Exchange (ETDEWEB)
Park, J.M.; Kim, H.J., E-mail: hongjooknu@gmail.com; Hwang, Y.S.; Kim, D.H.; Park, H.W.
2014-02-15
We fabricated quantum-dot doped plastic scintillators in order to control the emission wavelength. We studied the characterization of the quantum-dots (CdSe/ZnS) and PPO (2, 5-diphenyloxazole) doped styrene based plastic scintillators. PPO is usually used as a dopant to enhance the scintillation properties of organic scintillators with a maximum emission wavelength of 380 nm. In order to study the scintillation properties of the quantum-dots doped plastic scintillators, the samples were irradiated with X-ray, photon, and 45 MeV proton beams. We observed that only PPO doped plastic scintillators shows a luminescence peak around 380 nm. However, both the quantum-dots and PPO doped plastic scintillators shows luminescence peaks around 380 nm and 520 nm. Addition of quantum-dots had shifted the luminescence spectrum from 380 nm (PPO) toward the region of 520 nm (Quantum-dots). Emissions with wavelength controllable plastic scintillators can be matched to various kinds of photosensors such as photomultiplier tubes, photo-diodes, avalanche photo-diodes, and CCDs, etc. Also quantum-dots doped plastic scintillator, which is irradiated 45 MeV proton beams, shows that the light yield of quantum-dots doped plastic scintillator is increases as quantum-dots doping concentration increases at 520 nm. And also the plastic scintillators were irradiated with Cs-137 γ-ray for measuring fluorescence decay time. -- Highlights: • Quantum-dot doped plastic scintillator is grown by the thermal polymerization method. • Quantum-dot doped plastic scintillators can control the emission wavelength to match with photo-sensor. • Quantum-dots and PPO doped plastic scintillators emitted luminescence peaks around 380 nm and 520 nm. • We observed the energy transfer from PPO to quantum-dot in the quantum-dot doped plastic scintillator.
Recent developments in luminescent solar concentrators
van Sark, W. G. J. H. M.
2014-10-01
High efficiency photovoltaic devices combine full solar spectrum absorption and effective generation and collection of charge carriers, while commercial success depends on cost effectiveness in manufacturing. Spectrum modification using down shifting has been demonstrated in luminescent solar concentrators (LSCs) since the 1970s, as a cheap alternative for standard c-Si technology. LSCs consist of a highly transparent plastic plate, in which luminescent species are dispersed, which absorb incident light and emit light at a red-shifted wavelength, with high quantum efficiency. Material issues have hampered efficiency improvements, in particular re-absorption of light emitted by luminescent species and stability of these species. In this contribution, approaches are reviewed on minimizing re-absorption, which should allow surpassing the 10% luminescent solar concentrator efficiency barrier.
Understanding quantum mechanics by measuring the properties of mesoscopic devices
International Nuclear Information System (INIS)
Webb, R.
1993-01-01
Measurements of the electrical transport and magnetic properties of micron-size scale insulators, metals, semi-metals, and semiconductors at low temperatures have uncovered a wealth of unexpected phenomena. The only way to understand these new properties is by invoking many of the postulates of quantum mechanics. The author has confirmed that the electron acts as a long-range phase-coherent wave and conventional classical forces are not as important as scalar and vector potentials in determining the response of the electron as it moves through its environment. This talk will focus on the measurement of the Aharonov-Bohm self-interference effects, nonlocal transport phenomena, and persistent currents in normal metal ring structures that have been observed in these nanostructures
Reality, measurement and locality in Quantum Field Theory
International Nuclear Information System (INIS)
Tommasini, Daniele
2002-01-01
It is currently believed that the local causality of Quantum Field Theory (QFT) is destroyed by the measurement process. This belief is also based on the Einstein-Podolsky-Rosen (EPR) paradox and on the so-called Bell's theorem, that are thought to prove the existence of a mysterious, instantaneous action between distant measurements. However, I have shown recently that the EPR argument is removed, in an interpretation-independent way, by taking into account the fact that the Standard Model of Particle Physics prevents the production of entangled states with a definite number of particles. This result is used here to argue in favor of a statistical interpretation of QFT and to show that it allows for a full reconciliation with locality and causality. Within such an interpretation, as Ballentine and Jarret pointed out long ago, Bell's theorem does not demonstrate any nonlocality. (author)
Admittance measurements in the quantum Hall effect regime
Energy Technology Data Exchange (ETDEWEB)
Hernández, C., E-mail: carlos.hernandezr@unimilitar.edu.co [Departamento de Física, Universidad Militar Nueva Granada, Carrera 11 # 101-80, Bogotá D.C. (Colombia); Laboratorio de Magnetismo, Departamento de Física, Universidad de los Andes, A.A. 4976, Bogotá D.C. (Colombia); Consejo, C.; Chaubet, C. [Laboratoire Charles Coulomb L2C, Université Montpellier II, Pl. E. Bataillon, 34095 Montpellier Cedex 5 (France)
2014-11-15
In this work we present an admittance study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. We have studied several Hall bars in different contacts configurations in the frequency range 100 Hz–1 MHz. Our interpretation is based on the Landauer–Büttiker theory and takes into account both the capacitance and the topology of the coaxial cables which are connected to the sample holder. We show that we always observe losses through the capacitive impedance of the coaxial cables, except in the two contacts configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the 2DEG and show its dependence with the filling factor ν.
Decoherence bypass of macroscopic superpositions in quantum measurement
International Nuclear Information System (INIS)
Spehner, Dominique; Haake, Fritz
2008-01-01
We study a class of quantum measurement models. A microscopic object is entangled with a macroscopic pointer such that a distinct pointer position is tied to each eigenvalue of the measured object observable. Those different pointer positions mutually decohere under the influence of an environment. Overcoming limitations of previous approaches we (i) cope with initial correlations between pointer and environment by considering them initially in a metastable local thermal equilibrium, (ii) allow for object-pointer entanglement and environment-induced decoherence of distinct pointer readouts to proceed simultaneously, such that mixtures of macroscopically distinct object-pointer product states arise without intervening macroscopic superpositions, and (iii) go beyond the Markovian treatment of decoherence. (fast track communication)
Quantum Measurements: From Bayes Rule to Neural Networks
DEFF Research Database (Denmark)
Greplova, Eliska
2017-01-01
Quantum technologies are becoming more and more introduced into the devices that we use in the daily life, such as quantum dot based television screens or quantum cryptographic channels for encoding financial transactions. Given the limits of the silicon computer chips, it will in the near future...... learning techniques such as artificial neural networks....
High-rate measurement-device-independent quantum cryptography
DEFF Research Database (Denmark)
Pirandola, Stefano; Ottaviani, Carlo; Spedalieri, Gaetana
2015-01-01
Quantum cryptography achieves a formidable task - the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction...
Energy Technology Data Exchange (ETDEWEB)
Bishnoi, Swati [CSIR-Network of Institutes for Solar Energy, New Delhi 110001 (India); Luminescent Materials and Devices Group, CSIR-National Physical Laboratory, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Gupta, Vinay, E-mail: drvinaygupta@netscape.net; Sharma, Gauri D.; Chand, Suresh [CSIR-Network of Institutes for Solar Energy, New Delhi 110001 (India); Organic and Hybrid Solar Cells Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, New Delhi 110012 (India); Sharma, Chhavi; Kumar, Mahesh [Ultrafast Optoelectronics and Terahertz Photonics Lab, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, New Delhi 110012 (India); Haranath, D. [CSIR-Network of Institutes for Solar Energy, New Delhi 110001 (India); Luminescent Materials and Devices Group, CSIR-National Physical Laboratory, New Delhi 110012 (India); Naqvi, Sheerin [Luminescent Materials and Devices Group, CSIR-National Physical Laboratory, New Delhi 110012 (India)
2016-07-11
In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO{sub 4}:Sm{sup 3+}) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO{sub 4}:Sm{sup 3+} QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO{sub 4}:Sm{sup 3+} to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO{sub 4}:Sm{sup 3+} QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO{sub 4}:Sm{sup 3+}:PC{sub 71}BM ([6,6]-phenyl-C{sub 71}-butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO{sub 4}:Sm{sup 3+}:PC{sub 71}BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC{sub 71}BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.
Control-free control: Manipulating a quantum system using only a limited set of measurements
International Nuclear Information System (INIS)
Ashhab, S.; Nori, Franco
2010-01-01
We present and discuss different protocols for preparing an arbitrary quantum state of a qubit using only a restricted set of measurements, with no unitary operations at all. We show that an arbitrary state can indeed be prepared, provided that the available measurements satisfy certain requirements. Our results shed light on the role that measurement-induced back-action plays in quantum feedback control and the extent to which this back-action can be exploited in quantum-control protocols.
Convergence of repeated quantum nondemolition measurements and wave-function collapse
International Nuclear Information System (INIS)
Bauer, Michel; Bernard, Denis
2011-01-01
Motivated by recent experiments on quantum trapped fields, we give a rigorous proof that repeated indirect quantum nondemolition (QND) measurements converge to the collapse of the wave function as predicted by the postulates of quantum mechanics for direct measurements. We also relate the rate of convergence toward the collapsed wave function to the relative entropy of each indirect measurement, a result which makes contact with information theory.
Distribution of Bell-inequality violation versus multiparty-quantum-correlation measures
Sharma, Kunal; Das, Tamoghna; Sen (de), Aditi; Sen, Ujjwal
Violation of a Bell inequality guarantees the existence of quantum correlations in a shared quantum state. A pure bipartite quantum state, having nonvanishing quantum correlation, always violates a Bell inequality. Such correspondence is absent for multipartite pure quantum states in the case of multipartite correlation function Bell inequalities with two settings at each site. We establish a connection between the monogamy of Bell-inequality violation and multiparty quantum correlations for shared multisite quantum states. We believe that the relation is generic, as it is true for a number of different multisite measures that are defined from radically different perspectives. Precisely, we quantify the multisite-quantum-correlation content in the states by generalized geometric measure, a genuine multisite entanglement measure, as well as three monogamybased multiparty-quantum-correlation measures, viz., 3-tangle, quantum-discord score, and quantum-work-deficit score. We find that generalized Greenberger-Horne-Zeilinger states and another single-parameter family of states, which we refer to as the special Greenberger-Horne-Zeilinger states, have the status of extremal states in such relations.
Energy Technology Data Exchange (ETDEWEB)
Park, Y; Oguma, H; Ueda, H; Iida, N [Keio University, Tokyo (Japan)
1997-10-01
In order to make clear of the combustion mechanism and the frame structure in two stake, so called, active thermo-atmosphere combustion (ATAC) engine fueled by gasoline and methanol, we measured the 2-demensional images of OH, CH and C2 radical band spectra in both ATAC and SI combustion mode. From the results of pressure data in the cylinder, the heat release rate was calculated. We evaluated the correlation of radical luminescence intensity and the rate of heat release. 3 refs., 4 figs., 2 tabs.
Towards the Fundamental Quantum Limit of Linear Measurements of Classical Signals.
Miao, Haixing; Adhikari, Rana X; Ma, Yiqiu; Pang, Belinda; Chen, Yanbei
2017-08-04
The quantum Cramér-Rao bound (QCRB) sets a fundamental limit for the measurement of classical signals with detectors operating in the quantum regime. Using linear-response theory and the Heisenberg uncertainty relation, we derive a general condition for achieving such a fundamental limit. When applied to classical displacement measurements with a test mass, this condition leads to an explicit connection between the QCRB and the standard quantum limit that arises from a tradeoff between the measurement imprecision and quantum backaction; the QCRB can be viewed as an outcome of a quantum nondemolition measurement with the backaction evaded. Additionally, we show that the test mass is more a resource for improving measurement sensitivity than a victim of the quantum backaction, which suggests a new approach to enhancing the sensitivity of a broad class of sensors. We illustrate these points with laser interferometric gravitational-wave detectors.
Application of luminescence techniques in retrospective dosimetry
DEFF Research Database (Denmark)
Bøtter-Jensen, L.; Jungner, H.
1999-01-01
Luminescence signals measured from minerals within bricks or ceramic samples can provide information about the absorbed radiation dose. This feature has for several years been used in dating archaeological and geological samples and recently luminescence techniques have been intensively used far ...
Study of the liquid water luminescence induced by charged particles
International Nuclear Information System (INIS)
Rusu, Mircea; Stere, Oana; Haiduc, Maria; Caramete, Laurentiu
2004-01-01
Many observations suggested that liquid water (with impurities) could give a luminescence output when irradiated with charged particles. We investigate theoretical and practical possibility of detecting such luminescence. Preliminary results on this possibility are presented, and a layout of the device proposed for measuring luminescence is given. (authors)
Oxide/polymer nanocomposites as new luminescent materials
Vollath, D.; Szabó, D. V.; Schlabach, S.
2004-06-01
It is demonstrated that nanocomposites, consisting of an electrically insulating oxide core and PMMA coating exhibit strong luminescence. This luminescence is connected to the interface, where PMMA is bond via a carboxylate bonding to the surface. In this case, luminescence is originated at the carbonyl group of the coating polymer. With decreasing particle size, this emission shows a blue shift, following a law inversely the ones found for quantum confinement systems. For semi-conducting oxides, such as ZnO, this interface related emission is found additionally to quantum confinement phenomena.
Collapsing a perfect superposition to a chosen quantum state without measurement.
Directory of Open Access Journals (Sweden)
Ahmed Younes
Full Text Available Given a perfect superposition of [Formula: see text] states on a quantum system of [Formula: see text] qubits. We propose a fast quantum algorithm for collapsing the perfect superposition to a chosen quantum state [Formula: see text] without applying any measurements. The basic idea is to use a phase destruction mechanism. Two operators are used, the first operator applies a phase shift and a temporary entanglement to mark [Formula: see text] in the superposition, and the second operator applies selective phase shifts on the states in the superposition according to their Hamming distance with [Formula: see text]. The generated state can be used as an excellent input state for testing quantum memories and linear optics quantum computers. We make no assumptions about the used operators and applied quantum gates, but our result implies that for this purpose the number of qubits in the quantum register offers no advantage, in principle, over the obvious measurement-based feedback protocol.
Implementation of generalized measurements with minimal disturbance on a quantum computer
International Nuclear Information System (INIS)
Decker, T.; Grassl, M.
2006-01-01
We consider the problem of efficiently implementing a generalized measurement on a quantum computer. Using methods from representation theory, we exploit symmetries of the states we want to identify respectively symmetries of the measurement operators. In order to allow the information to be extracted sequentially, the disturbance of the quantum state due to the measurement should be minimal. (Abstract Copyright [2006], Wiley Periodicals, Inc.)
Pedagogical Review of Quantum Measurement Theory with an Emphasis on Weak Measurements
Directory of Open Access Journals (Sweden)
Bengt E. Y. Svensson
2013-05-01
Full Text Available The quantum theory of measurement has been with us since quantum mechanics was invented. It has recently been invigorated, partly due to the increasing interest in quantum information science. In this partly pedagogical review I attempt to give a self-contained overview of non-relativistic quantum theory of measurement expressed in density matrix formalism. I will not dwell on the applications in quantum information theory; it is well covered by several books in that field. The focus is instead on applications to the theory of weak measurement, as developed by Aharonov and collaborators. Their development of weak measurement combined with what they call post-selection - judiciously choosing not only the initial state of a system (pre-selection but also its final state - has received much attention recently. Not the least has it opened up new, fruitful experimental vistas, like novel approaches to amplification. But the approach has also attached to it some air of mystery. I will attempt to demystify it by showing that (almost all results can be derived in a straight-forward way from conventional quantum mechanics. Among other things, I develop the formalism not only to first order but also to second order in the weak interaction responsible for the measurement. I apply it to the so called Leggett-Garg inequalities, also known as Bell inequalities in time. I also give an outline, even if rough, of some of the ingenious experiments that the work by Aharonov and collaborators has inspired. As an application of weak measurement, not related to the approach by Aharonov and collaborators, the formalism also allows me to derive the master equation for the density matrix of an open system in interaction with an environment. An issue that remains in the weak measurement plus post-selection approach is the interpretation of the so called weak value of an observable. Is it a bona fide property of the system considered? I have no definite answer to this
Luminescent amine sensor based on europium(III) chelate.
Petrochenkova, Nataliya V; Mirochnik, Anatolii G; Emelina, Tatyana B; Sergeev, Alexander A; Leonov, Andrei A; Voznesenskii, Sergey S
2018-07-05
The effect of methylamine vapor on luminescence of Eu(III) tris-benzoylacetonate (I) immobilized in thin-layer chromatography plates has been investigated. It has been revealed that interaction of I with analyte vapor results in increase of the intensity of Eu(III) luminescence. The mechanism of the effect of methylamine vapors on intensification of the Eu(III) luminescence has been suggested using the data of IR spectroscopy and quantum chemistry calculations. The mechanism of luminescence sensitization consists in bonding of an analyte molecule with a water molecule into the coordination sphere of Eu(III). As a result, the bond of a water molecule with the luminescence centre weakens, rigid structural fragment including europium ion, water and methylamine molecules forms. The presence of such fragment must naturally promote decrease of influence of OH-vibrations on luminescence of the complex I. Copyright © 2018 Elsevier B.V. All rights reserved.
Novel Schemes for Measurement-Based Quantum Computation
International Nuclear Information System (INIS)
Gross, D.; Eisert, J.
2007-01-01
We establish a framework which allows one to construct novel schemes for measurement-based quantum computation. The technique develops tools from many-body physics--based on finitely correlated or projected entangled pair states--to go beyond the cluster-state based one-way computer. We identify resource states radically different from the cluster state, in that they exhibit nonvanishing correlations, can be prepared using nonmaximally entangling gates, or have very different local entanglement properties. In the computational models, randomness is compensated in a different manner. It is shown that there exist resource states which are locally arbitrarily close to a pure state. We comment on the possibility of tailoring computational models to specific physical systems
Novel schemes for measurement-based quantum computation.
Gross, D; Eisert, J
2007-06-01
We establish a framework which allows one to construct novel schemes for measurement-based quantum computation. The technique develops tools from many-body physics-based on finitely correlated or projected entangled pair states-to go beyond the cluster-state based one-way computer. We identify resource states radically different from the cluster state, in that they exhibit nonvanishing correlations, can be prepared using nonmaximally entangling gates, or have very different local entanglement properties. In the computational models, randomness is compensated in a different manner. It is shown that there exist resource states which are locally arbitrarily close to a pure state. We comment on the possibility of tailoring computational models to specific physical systems.
One-sided measurement-device-independent quantum key distribution
Cao, Wen-Fei; Zhen, Yi-Zheng; Zheng, Yu-Lin; Li, Li; Chen, Zeng-Bing; Liu, Nai-Le; Chen, Kai
2018-01-01
Measurement-device-independent quantum key distribution (MDI-QKD) protocol was proposed to remove all the detector side channel attacks, while its security relies on the trusted encoding systems. Here we propose a one-sided MDI-QKD (1SMDI-QKD) protocol, which enjoys detection loophole-free advantage, and at the same time weakens the state preparation assumption in MDI-QKD. The 1SMDI-QKD can be regarded as a modified MDI-QKD, in which Bob's encoding system is trusted, while Alice's is uncharacterized. For the practical implementation, we also provide a scheme by utilizing coherent light source with an analytical two decoy state estimation method. Simulation with realistic experimental parameters shows that the protocol has a promising performance, and thus can be applied to practical QKD applications.
Advances in luminescence instrument systems
DEFF Research Database (Denmark)
Bøtter-Jensen, L.; Bulur, E.; Duller, G.A.T.
2000-01-01
We report on recent advances in the development of luminescence measurement systems and techniques at Riso. These include: (1) optical stimulation units based on new-generation powerful blue light (470 nm) emitting diodes providing up to 28 mW/cm(2) for OSL measurements; (2) an infrared (830 nm...
Transitions in the computational power of thermal states for measurement-based quantum computation
International Nuclear Information System (INIS)
Barrett, Sean D.; Bartlett, Stephen D.; Jennings, David; Doherty, Andrew C.; Rudolph, Terry
2009-01-01
We show that the usefulness of the thermal state of a specific spin-lattice model for measurement-based quantum computing exhibits a transition between two distinct 'phases' - one in which every state is a universal resource for quantum computation, and another in which any local measurement sequence can be simulated efficiently on a classical computer. Remarkably, this transition in computational power does not coincide with any phase transition, classical, or quantum in the underlying spin-lattice model.
Quantum optical arbitrary waveform manipulation and measurement in real time.
Kowligy, Abijith S; Manurkar, Paritosh; Corzo, Neil V; Velev, Vesselin G; Silver, Michael; Scott, Ryan P; Yoo, S J B; Kumar, Prem; Kanter, Gregory S; Huang, Yu-Ping
2014-11-17
We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting. We also report on experimental progress to distinguish two overlapping, orthogonal temporal modes, demonstrating over 8 dB extinction between picosecond-scale time-frequency modes, which agrees well with our theory. Our theoretical and experimental progress, as a whole, points to an enabling optical technique for various applications such as ultradense quantum coding, unity-efficiency cavity-atom quantum memories, and high-speed quantum computing.
National Research Council Canada - National Science Library
Cahay, Marc
1999-01-01
The symposium addresses recent developments in the area of nanoscale semiconductors, metallic, and organic structures, porous silicon quantum dot structures self-ordered nanostructures and clusters...
Feldspar, Infrared Stimulated Luminescence
DEFF Research Database (Denmark)
Jain, Mayank
2014-01-01
This entry primarily concerns the characteristics and the origins of infrared-stimulated luminescence in feldspars.......This entry primarily concerns the characteristics and the origins of infrared-stimulated luminescence in feldspars....
Luminescence sensitivity changes in quartz
Wintle, A G
1999-01-01
In the luminescence dating of sedimentary or heated quartz, some heat treatment is usually applied to the sample immediately prior to the measurement of the optically stimulated luminescence. In this paper we report experiments on a 30,000-year-old sedimentary quartz, in which we use the luminescence response to a test dose to monitor the changes in sensitivity that are caused by holding the quartz at temperatures from 160 to 280 deg. C for times from 10 s to 22 h. For an optically bleached sample, the monitoring is by both optically stimulated luminescence and the 110 deg. C TL peak; both luminescence signals are shown to have the same sensitisation (i.e. activation energy) characteristics. For natural or laboratory irradiated samples only the 110 deg. C TL peak can be used; sensitivity increases of up to a factor of 1.3 and 3 are observed for the natural and laboratory irradiated aliquots, respectively. Up to four exponential components are used to deconvolve the sensitivity change data; the dominant compon...
Visible luminescence in polyaniline/(gold nanoparticle) composites
Energy Technology Data Exchange (ETDEWEB)
Santos, Renata F. S. [Universidade Federal de Pernambuco, Pos-Graduacao em Ciencia de Materiais (Brazil); Andrade, Cesar A. S. [Universidade Federal de Pernambuco, Departamento de Bioquimica (Brazil); Santos, Clecio G. dos [Instituto de Educacao, Ciencia e Tecnologia de Pernambuco (Brazil); Melo, Celso P. de, E-mail: celso@df.ufpe.br [Universidade Federal de Pernambuco, Pos-Graduacao em Ciencia de Materiais (Brazil)
2013-01-15
We describe the use of solution chemistry methods to prepare polyaniline/(gold nanoparticles)-PANI/AuNPs-composites as colloidal particles that exhibit an intense green fluorescence after excitation in the ultraviolet region. Measurements of the relative fluorescence quantum yield indicate that the intensity of the observed luminescence of these nanocomposites is a few orders of magnitude higher than the corresponding fluorescence of either the isolated polymer or the pure AuNPs. Hence, cooperative effects between the conducting polymer chains and the metallic particles must dominate the emission behavior of these materials. Transmission electron microscopy reveals the existence of metal nanoparticle aggregates with sizes in the 2-3 nm range dispersed in the polymer matrix. By implementing an experimental planning, we have been able to change the preparation parameters so as to vary in a controlled manner the intensity and the profile of the luminescence spectrum as well as the size and aggregation characteristics of the colloidal particles. We also show that when the pH of the medium is varied, the dielectric properties (such as the degree of conductivity) of the PANI/AuNPs colloidal solutions and the intensity of their luminescence change in a consistent manner. Due to the polycation nature of the doped PANI chains, we suggest that these composites may find interesting applications as fluorescent markers of biologic molecules.
International Nuclear Information System (INIS)
Greig, Natalie E.; Einkauf, Jeffrey D.; Clark, Jessica M.; Corcoran, Eric J.; Karram, Joseph P.; Kent, Charles A.; Eugene, Vadine E.; Chan, Benny C.; Lill, Daniel T. de
2015-01-01
Dimethyl-3,4-furandicarboxylate undergoes hydrolysis under hydrothermal conditions with lanthanide (Ln) ions to form two-dimensional coordination polymers, [Ln(C 6 H 2 O 5 )(C 6 H 3 O 5 )(H 2 O)] n (Ln=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). The resulting materials exhibit luminescent properties with quantum yields and lifetimes for the Eu(III) and Tb(III) compounds of 1.1±0.3% and 0.387±0.0001 ms, and 3.3±0.8% and 0.769±0.006 ms, respectively. Energy values for the singlet and triplet states were determined for dimethyl-3,4-furandicarboxylate and 3,4-furandicarboxylic acid. Excited state dynamics and structural features are examined to explicate the reported quantum yields. A series of other FDC structures is briefly presented. - Graphical abstract: A new two-dimensional coordination polymer derived from the in-situ hydrolysis of a furan dimethyl ester with lanthanide(III) ions was obtained in order to study its photophysical behavior when constructed from trivalent Eu and Tb. Quantum yields, lifetime measurements, and singlet/triplet state energies values were obtained. The nature of the material's excited state dynamics is examined and correlated to its structure in order to explain the overall luminescent efficiency of the system. - Highlights: • A new lanthanide–furandicarboxylate coordination polymer is presented. • Eu and Tb compounds display luminescent properties, albeit with low quantum yields. • Photophysical behavior explained through the compound's triplet state and structure. • Nonradiative deactivation of luminescence through high-energy oscillators was noted. • Molecular modeling of the organic moiety was conducted
Energy Technology Data Exchange (ETDEWEB)
Greig, Natalie E.; Einkauf, Jeffrey D.; Clark, Jessica M.; Corcoran, Eric J.; Karram, Joseph P.; Kent, Charles A.; Eugene, Vadine E. [Department of Chemistry & Biochemistry, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431 (United States); Chan, Benny C. [Department of Chemistry, The College of New Jersey, 2000 Pennington Road, Ewing, NJ 08628 (United States); Lill, Daniel T. de, E-mail: ddelill@fau.edu [Department of Chemistry & Biochemistry, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431 (United States)
2015-05-15
Dimethyl-3,4-furandicarboxylate undergoes hydrolysis under hydrothermal conditions with lanthanide (Ln) ions to form two-dimensional coordination polymers, [Ln(C{sub 6}H{sub 2}O{sub 5})(C{sub 6}H{sub 3}O{sub 5})(H{sub 2}O)]{sub n} (Ln=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). The resulting materials exhibit luminescent properties with quantum yields and lifetimes for the Eu(III) and Tb(III) compounds of 1.1±0.3% and 0.387±0.0001 ms, and 3.3±0.8% and 0.769±0.006 ms, respectively. Energy values for the singlet and triplet states were determined for dimethyl-3,4-furandicarboxylate and 3,4-furandicarboxylic acid. Excited state dynamics and structural features are examined to explicate the reported quantum yields. A series of other FDC structures is briefly presented. - Graphical abstract: A new two-dimensional coordination polymer derived from the in-situ hydrolysis of a furan dimethyl ester with lanthanide(III) ions was obtained in order to study its photophysical behavior when constructed from trivalent Eu and Tb. Quantum yields, lifetime measurements, and singlet/triplet state energies values were obtained. The nature of the material's excited state dynamics is examined and correlated to its structure in order to explain the overall luminescent efficiency of the system. - Highlights: • A new lanthanide–furandicarboxylate coordination polymer is presented. • Eu and Tb compounds display luminescent properties, albeit with low quantum yields. • Photophysical behavior explained through the compound's triplet state and structure. • Nonradiative deactivation of luminescence through high-energy oscillators was noted. • Molecular modeling of the organic moiety was conducted.
A critical analysis of the quantum theory of measurement
International Nuclear Information System (INIS)
Fer, F.
1984-01-01
Keeping strictly in the positivist and probabilistic, hence hilbertian frame of Quantum Mechanics, the author tries to ascertain whether or not Quantum Mechanics, starting from its axioms, reaches the aim of any physical theory, that is, comparison with experiment. The answer is: no, as long as it keeps close to the existing axiomatics, and also to accurate mathematics. (Auth.)
Mean values and measures in quantum mechanics and classical mechanics
International Nuclear Information System (INIS)
Bass, J.
1980-01-01
In quantum mechanics, for a system at a fixed time, the theory of operators associates to every physical quantity X a probability law. But it is not possible to associate a probability law to a pair (X, Y) of operators, when they do not commute. Therefore it is not possible to represent the physical quantities by the usual methods of probability theory. The aim of this paper is to show that, if X, Y are represented by non random functions which are oscillating in such a way that they generate temporal averages their exist pairs of functions X, Y which have properties similar to pairs of operators. To X and to Y it is possible to associate two measures analogous to probability measures, but that is not possible for the pair (X, Y). The functions satisfying to such conditions are the pseudo-random function, a class of stationary functions which is complementary of the class of almost-periodic functions. The construction of these functions makes use of uniformly distributed sequences of real numbers, which constitute a simulation of random variables uniformly distributed over [0, 1]. Their properties are consequences of the ergodic theorems of H. Weyl (1916) and are related to the properties of irrational numbers [fr
Fast automotive diesel exhaust measurement using quantum cascade lasers
Herbst, J.; Brunner, R.; Lambrecht, A.
2013-12-01
Step by step, US and European legislations enforce the further reduction of atmospheric pollution caused by automotive exhaust emissions. This is pushing automotive development worldwide. Fuel efficient diesel engines with SCRtechnology can impede NO2-emission by reduction with NH3 down to the ppm range. To meet the very low emission limits of the Euro6 resp. US NLEV (National Low Emission Vehicle) regulations, automotive manufacturers have to optimize continuously all phases of engine operation and corresponding catalytic converters. Especially nonstationary operation holds a high potential for optimizing gasoline consumption and further reducing of pollutant emissions. Test equipment has to cope with demanding sensitivity and speed requirements. In the past Fraunhofer IPM has developed a fast emission analyzer called DEGAS (Dynamic Exhaust Gas Analyzer System), based on cryogenically cooled lead salt lasers. These systems have been used at Volkswagen AG`s test benches for a decade. Recently, IPM has developed DEGAS-Next which is based on cw quantum cascade lasers and thermoelectrically cooled detectors. The system is capable to measure three gas components (i.e. NO, NO2, NH3) in two channels with a time resolution of 20 ms and 1 ppm detection limits. We shall present test data and a comparison with fast FTIR measurements.
International Nuclear Information System (INIS)
Eriksson, Karl-Erik
2009-01-01
The measurement process of quantum mechanics is analysed in the scattering theory of quantum field theory. A matrix of bilinear forms of the scattering amplitudes (the R-matrix) is used as the basic descriptive tool. The measurement process is viewed as a final-state interaction described through a series of linear stochastic mappings of the R-matrix, not changing the observable to be measured. The unknown details of the measurement apparatus enter through the stochasticity of the mappings. Although linear in terms of the R-matrix, the mappings are nonlinear in the density matrix, which is obtainable from the R-matrix through normalization. The eigenstates of the observable are the attractors of the mapping process. This result, known from previous generalizations of quantum mechanics, is obtained here within linear quantum mechanics. The conclusion is that the measurement process can be understood within relativistic quantum field theory itself without any generalization or metatheory.
On luminescence lifetimes in quartz
International Nuclear Information System (INIS)
Chithambo, M.L.; Galloway, R.B.
2000-01-01
In this paper we present results of investigations concerning the time dependence of luminescence emission relative to the time of stimulation in quartz. Measurements of time-resolved spectra were performed on a new versatile pulsed light emitting diode system using 525 nm stimulation, an 11 μs duration pulse, a repetition rate of 11 kHz and a 64 μs dynamic range. Effects on luminescence lifetime resulting from sample treatments such as optical stimulation, irradiation, and preheating, are reported
Metal plasmon enhanced europium complex luminescence
International Nuclear Information System (INIS)
Liu Feng; Aldea, Gabriela; Nunzi, Jean-Michel
2010-01-01
The plasmon enhanced luminescence of a rare-earth complex Tris(6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium (Eu(fod) 3 ) was investigated. A polyvinyl alcohol (PVA) thin film was successfully adopted as a spacer to separate the Eu complex from the silver island film (SIF), and five-fold enhancement of the radiative decay rate of the Eu complex on SIF was demonstrated based on the luminescence intensity and lifetime measurement. Investigation of the distance dependent luminescence indicates that 7 nm is an optimal distance for SIF enhanced Eu luminescence. Plasmon enhanced rare-earth luminescence based on an organic film spacer would find potential applications in plasmon enhanced organic light emitting diode (OLED) devices.
International Nuclear Information System (INIS)
Tomes, John J; Finlayson, Chris E
2016-01-01
We report upon the exploitation of the latest 3D printing technologies to provide low-cost instrumentation solutions, for use in an undergraduate level final-year project. The project addresses prescient research issues in optoelectronics, which would otherwise be inaccessible to such undergraduate student projects. The experimental use of an integrating sphere in conjunction with a desktop spectrometer presents opportunities to use easily handled, low cost materials as a means to illustrate many areas of physics such as spectroscopy, lasers, optics, simple circuits, black body radiation and data gathering. Presented here is a 3rd year undergraduate physics project which developed a low cost (£25) method to manufacture an experimentally accurate integrating sphere by 3D printing. Details are given of both a homemade internal reflectance coating formulated from readily available materials, and a robust instrument calibration method using a tungsten bulb. The instrument is demonstrated to give accurate and reproducible experimental measurements of luminescence quantum yield of various semiconducting fluorophores, in excellent agreement with literature values. (paper)
Tomes, John J.; Finlayson, Chris E.
2016-09-01
We report upon the exploitation of the latest 3D printing technologies to provide low-cost instrumentation solutions, for use in an undergraduate level final-year project. The project addresses prescient research issues in optoelectronics, which would otherwise be inaccessible to such undergraduate student projects. The experimental use of an integrating sphere in conjunction with a desktop spectrometer presents opportunities to use easily handled, low cost materials as a means to illustrate many areas of physics such as spectroscopy, lasers, optics, simple circuits, black body radiation and data gathering. Presented here is a 3rd year undergraduate physics project which developed a low cost (£25) method to manufacture an experimentally accurate integrating sphere by 3D printing. Details are given of both a homemade internal reflectance coating formulated from readily available materials, and a robust instrument calibration method using a tungsten bulb. The instrument is demonstrated to give accurate and reproducible experimental measurements of luminescence quantum yield of various semiconducting fluorophores, in excellent agreement with literature values.
International Nuclear Information System (INIS)
Usera, J.I.
1996-01-01
An approach based on bits and pieces of standard wisdom plus and operational quantum mechanical identity deduced by the author is presented here in order to convey arguments concerning the quantum theory of measurement and which betray a flavor against completive claims for quantum mechanics. Special emphasis is put on the phenomenon of decoherence. This phenomenon (which is experimentally verifiable) finds natural room within the formalism while the wave function collapse (which is not) is precluded. (Author)
Measurement-Device Independency Analysis of Continuous-Variable Quantum Digital Signature
Directory of Open Access Journals (Sweden)
Tao Shang
2018-04-01
Full Text Available With the practical implementation of continuous-variable quantum cryptographic protocols, security problems resulting from measurement-device loopholes are being given increasing attention. At present, research on measurement-device independency analysis is limited in quantum key distribution protocols, while there exist different security problems for different protocols. Considering the importance of quantum digital signature in quantum cryptography, in this paper, we attempt to analyze the measurement-device independency of continuous-variable quantum digital signature, especially continuous-variable quantum homomorphic signature. Firstly, we calculate the upper bound of the error rate of a protocol. If it is negligible on condition that all measurement devices are untrusted, the protocol is deemed to be measurement-device-independent. Then, we simplify the calculation by using the characteristics of continuous variables and prove the measurement-device independency of the protocol according to the calculation result. In addition, the proposed analysis method can be extended to other quantum cryptographic protocols besides continuous-variable quantum homomorphic signature.
Zhou, Hua; Su, Yang; Wang, Rong; Zhu, Yong; Shen, Huiping; Pu, Tao; Wu, Chuanxin; Zhao, Jiyong; Zhang, Baofu; Xu, Zhiyong
2017-10-01
Online reconstruction of a time-variant quantum state from the encoding/decoding results of quantum communication is addressed by developing a method of evolution reconstruction from a single measurement record with random time intervals. A time-variant two-dimensional state is reconstructed on the basis of recovering its expectation value functions of three nonorthogonal projectors from a random single measurement record, which is composed from the discarded qubits of the six-state protocol. The simulated results prove that our method is robust to typical metro quantum channels. Our work extends the Fourier-based method of evolution reconstruction from the version for a regular single measurement record with equal time intervals to a unified one, which can be applied to arbitrary single measurement records. The proposed protocol of evolution reconstruction runs concurrently with the one of quantum communication, which can facilitate the online quantum tomography.
International Nuclear Information System (INIS)
Xiang Guo-Yong; Guo Guang-Can
2013-01-01
The statistical error is ineluctable in any measurement. Quantum techniques, especially with the development of quantum information, can help us squeeze the statistical error and enhance the precision of measurement. In a quantum system, there are some quantum parameters, such as the quantum state, quantum operator, and quantum dimension, which have no classical counterparts. So quantum metrology deals with not only the traditional parameters, but also the quantum parameters. Quantum metrology includes two important parts: measuring the physical parameters with a precision beating the classical physics limit and measuring the quantum parameters precisely. In this review, we will introduce how quantum characters (e.g., squeezed state and quantum entanglement) yield a higher precision, what the research areas are scientists most interesting in, and what the development status of quantum metrology and its perspectives are. (topical review - quantum information)
Zhang, Zhen-Yu; Wang, Hai-Yu; Zhang, Yan-Xia; Hao, Ya-Wei; Sun, Chun; Zhang, Yu; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo
2016-06-01
Hybrid metal halide perovskites have been paid enormous attentions in photophysics research, whose excellent performances were attributed to their intriguing charge carriers proprieties. However, it still remains far from satisfaction in the comprehensive understanding of perovskite charge-transport properities, especially about trap-assisted recombination process. In this Letter, through time-resolved transient absorption (TA) and photoluminescence (PL) measurements, we provided a relative comprehensive investigation on the charge carriers recombination dynamics of CH3NH3PbBr3 (MAPbBr3) perovskite films and quantum dots (QDs), especially about trap-assisted recombination. It was found that the integral recombination mode of MAPbBr3 films was highly sensitive to the density distribution of generated charge carriers and trap states. Additional, Trap effects would be gradually weakened with elevated carrier densities. Furthermore, the trap-assisted recombination can be removed from MAPbBr3 QDs through its own surface passivation mechanism and this specialty may render the QDs as a new material in illuminating research. This work provides deeper physical insights into the dynamics processes of MAPbBr3 materials and paves a way toward more light-harvesting applications in future.
An integrity measure to benchmark quantum error correcting memories
Xu, Xiaosi; de Beaudrap, Niel; O'Gorman, Joe; Benjamin, Simon C.
2018-02-01
Rapidly developing experiments across multiple platforms now aim to realise small quantum codes, and so demonstrate a memory within which a logical qubit can be protected from noise. There is a need to benchmark the achievements in these diverse systems, and to compare the inherent power of the codes they rely upon. We describe a recently introduced performance measure called integrity, which relates to the probability that an ideal agent will successfully ‘guess’ the state of a logical qubit after a period of storage in the memory. Integrity is straightforward to evaluate experimentally without state tomography and it can be related to various established metrics such as the logical fidelity and the pseudo-threshold. We offer a set of experimental milestones that are steps towards demonstrating unconditionally superior encoded memories. Using intensive numerical simulations we compare memories based on the five-qubit code, the seven-qubit Steane code, and a nine-qubit code which is the smallest instance of a surface code; we assess both the simple and fault-tolerant implementations of each. While the ‘best’ code upon which to base a memory does vary according to the nature and severity of the noise, nevertheless certain trends emerge.
Electromagnetic and quantum measurements a bitemporal neoclassical theory
Wessel-Berg, Tore
2001-01-01
It is a pleasure to write a foreword for Professor Tore Wessel-Berg's book, "Electromagnetic and Quantum Measurements: A Bitemporal Neoclassical Theory." This book appeals to me for several reasons. The most important is that, in this book, Wessel-Berg breaks from the pack. The distinguished astrophysicist Thomas Gold has written about the pressures on scientists to move in tight formation, to avoid having their legs nipped by the sheepdogs of science. This book demonstrates that Wessel-Berg is willing to take that risk. I confess that I do not sufficiently understand this book to be able to either agree or disagree with its thesis. Nevertheless, Wessel-Berg makes very cogent arguments for setting out on his journey. The basic equations of physics are indeed time-reversible. Our experience, that leads us to the concept of an "arrow of time," is derived from macro scopic phenomena, not from fundamental microscopic phenomena. For this reason, it makes very good sense to explore the consequences of treating mi...
Immonen, Nina; Karp, Matti
2006-02-01
Nisin is a lantibiotic, an antibacterial peptide produced by certain Lactococcus lactis strains that kills or inhibits the growth of other bacteria. Nisin is widely used as a food preservative, and its long-time use suggests that it can be generally regarded as safe. We have developed a method for determining the amount of nisin in food samples that is based on luminescent biosensor bacteria. Bacterial luciferase operon luxABCDE was inserted into plasmid pNZ8048, and the construct was transformed by electroporation into Lc. lactis strain NZ9800, whose ability to produce nisin has been erased by deletion of the gene nisA. The operon luxABCDE has been modified to be functional in gram-positive bacteria to confer a bioluminescent phenotype without the requirement of adding an exogenous substrate. In the plasmid pNZ8048, the operon was placed under control of the nisin-inducible nisA promoter. The chromosomal nisRK genes of Lc. lactis NZ9800 allow it to sense nisin in the environment and relay this signal via signal transduction proteins NisK and NisR to initiate transcription from nisA promoter. In the case of our sensor bacteria, this leads to production of luciferase and, thus, luminescence that can be directly measured from living bacteria. Luminescence can be detected as early as within minutes of induction. The nisin assay described here provides a detection limit in the sub-picogram level per ml, and a linear area between 1 - 1000 pg/ml. The sensitivity of this assay exceeds the performance of all previously published methods.
Inhibited quantum processes through repeated measurements: An approach to quantum zero effect?
International Nuclear Information System (INIS)
Crespo, G.; Proto, A.N.; Cerdeira, H.A.
1992-04-01
The dynamics of a finite set of relevant observables, associated to a Hamiltonian of a three level system is analyzed in connection with the quantum Zeno effect. Since we use the Hamiltonian that completely describes the physical situation related to the experiment under study (W.M. Itano et al, Phys. Rev. A41, 2295 (1990)), no reduction or collapse of the wave function is required to describe the quantum Zeno effect. (author). 18 refs, 18 figs
Polarization memory of white luminescence of Ag nanoclusters dispersed in glass host.
Kuznetsov, A S; Tikhomirov, V K; Moshchalkov, V V
2012-09-10
A mechanism for white luminescence of Ag nanoclusters dispersed in oxyfluoride glass host has been revealed by studying a temperature dependence of its polarization memory. The spectral dependence of the polarization memory indicates the presence of a variety of Ag nanoclusters, particularly emitting in the blue, green and red. Temperature activated intercluster energy transfer has been found responsible for white luminescence. The means for increasing luminescence quantum yield have been suggested. This efficient white luminescence may be used in highly demanded devices, such as luminescent lamps, displays, color phosphors for LEDs, photovoltaic devices based on down shifting of solar spectrum.
Akselrod, Gleb M.; Bawendi, Moungi G.; Bulovic, Vladimir; Tischler, Jonathan R.; Tisdale, William A.; Walker, Brian J.
2017-12-12
Disclosed are a device and a method for the design and fabrication of the device for enhancing the brightness of luminescent molecules, nanostructures, and thin films. The device includes a mirror, a dielectric medium or spacer, an absorptive layer, and a luminescent layer. The absorptive layer is a continuous thin film of a strongly absorbing organic or inorganic material. The luminescent layer may be a continuous luminescent thin film or an arrangement of isolated luminescent species, e.g., organic or metal-organic dye molecules, semiconductor quantum dots, or other semiconductor nanostructures, supported on top of the absorptive layer.
Influence of sample oxidation on the nature of optical luminescence from porous silicon
International Nuclear Information System (INIS)
Coulthard, I.; Antel, W. J. Jr.; Freeland, J. W.; Sham, T. K.; Naftel, S. J.; Zhang, P.
2000-01-01
Site-selective luminescence experiments were performed upon porous-silicon samples exposed to varying degrees of oxidation. The source of different luminescence bands was determined to be due to either quantum confinement in nanocrystalline silicon or defective silicon oxide. Of particular interest is the defective silicon-oxide luminescence band found at 2.1 eV, which was found to frequently overlap with a luminescence band from nanocrystalline silicon. Some of the historical confusion and debate with regards to the source of luminescence from porous silicon can be attributed to this overlap. (c) 2000 American Institute of Physics
Quantum to Classical Transitions via Weak Measurements and Post-Selection
Cohen, Eliahu; Aharonov, Yakir
Alongside its immense empirical success, the quantum mechanical account of physical systems imposes a myriad of divergences from our thoroughly ingrained classical ways of thinking. These divergences, while striking, would have been acceptable if only a continuous transition to the classical domain was at hand. Strangely, this is not quite the case. The difficulties involved in reconciling the quantum with the classical have given rise to different interpretations, each with its own shortcomings. Traditionally, the two domains are sewed together by invoking an ad hoc theory of measurement, which has been incorporated in the axiomatic foundations of quantum theory. This work will incorporate a few related tools for addressing the above conceptual difficulties: deterministic operators, weak measurements, and post-selection. Weak Measurement, based on a very weak von Neumann coupling, is a unique kind of quantum measurement with numerous theoretical and practical applications. In contrast to other measurement techniques, it allows to gather a small amount of information regarding the quantum system, with only a negligible probability of collapsing it onto an eigenstate of the measured observable. A single weak measurement yieldsan almost random outcome, but when performed repeatedly over a large ensemble, the averaged outcome becomes increasingly robust and accurate. Importantly, a long sequence of weak measurements can be thought of as a single projective measurement. We claim in this work that classical variables appearing in the o-world, such as center of mass, moment of inertia, pressure, and average forces, result from a multitude of quantum weak measurements performed in the micro-world. Here again, the quantum outcomes are highly uncertain, but the law of large numbers obliges their convergence to the definite quantities we know from our everyday lives. By augmenting this description with a final boundary condition and employing the notion of "classical
International Nuclear Information System (INIS)
Carbo, R.; Calabuig, B.
1988-01-01
Molecular similarity measures within the quantum concept of density functions are described and analyzed. It is intended to show how artificial intelligence techniques can be used within the framework of quantum theory, in order to study and classify the molecular structures and their properties. (A.C.A.S) [pt
Calibration beads containing luminescent lanthanide ion complexes
The reliability of lanthanide luminescence measurements, by both flow cytometry and digital microscopy, will be enhanced by the availability of narrow-band emitting lanthanide calibration beads. These beads can also be used to characterize spectrographic instruments, including mi...
Luminescence properties of the Sm-doped borate glasses
Energy Technology Data Exchange (ETDEWEB)
Kindrat, I.I. [University of Zielona Góra, Institute of Physics, Division of Spectroscopy of Functional Materials, 4a Szafrana Street, 65-516 Zielona Góra (Poland); Padlyak, B.V., E-mail: B.Padlyak@if.uz.zgora.pl [University of Zielona Góra, Institute of Physics, Division of Spectroscopy of Functional Materials, 4a Szafrana Street, 65-516 Zielona Góra (Poland); Vlokh Institute of Physical Optics, 23 Dragomanov Street, 79-005 Lviv (Ukraine); Drzewiecki, A. [University of Zielona Góra, Institute of Physics, Division of Spectroscopy of Functional Materials, 4a Szafrana Street, 65-516 Zielona Góra (Poland)
2015-10-15
The optical absorption and photoluminescence (emission and excitation) spectra as well as decay kinetics of a series of the Sm-doped glasses with Li{sub 2}B{sub 4}O{sub 7}, LiKB{sub 4}O{sub 7}, CaB{sub 4}O{sub 7}, and LiCaBO{sub 3} compositions were investigated and analysed. The Li{sub 2}B{sub 4}O{sub 7}:Sm, LiKB{sub 4}O{sub 7}:Sm, CaB{sub 4}O{sub 7}:Sm, and LiCaBO{sub 3}:Sm glasses of high optical quality have been obtained from the corresponding polycrystalline compounds in the air atmosphere, using a standard glass technology. On the basis of electron paramagnetic resonance (EPR) and optical spectra analysis it was shown that the samarium impurity is incorporated into the glass network as Sm{sup 3+} (4f{sup 5}, {sup 6}H{sub 5/2}) ions, exclusively. All observed 4f – 4f transitions of the Sm{sup 3+} centres in the optical absorption and luminescence spectra of the investigated glasses are identified. Most intense emission band of the Sm{sup 3+} ions peaked about 598 nm ({sup 4}G{sub 5/2} → {sup 6}H{sub 7/2} transition) is characterised by a single exponential decay with typical lifetime values, which depend on the basic glass composition as well as concentration and local structure of the Sm{sup 3+} luminescence centres. The quantum efficiency has been evaluated for observed transitions of the Sm{sup 3+} centres using obtained experimental lifetimes and radiative lifetimes calculated by Judd–Ofelt theory. The calculated high quantum efficiencies and measured quantum yields of luminescence show that the investigated borate glasses are perspective luminescence materials. Energy transfer from the Ce{sup 3+} non-controlled impurity and intrinsic luminescence centres to the Sm{sup 3+} centres has been observed. Peculiarities of the Sm{sup 3+} local structure in the network of investigated glasses have been discussed based on the obtained spectroscopic results and structural data. - Highlights: • The Sm-doped Li{sub 2}B{sub 4}O{sub 7}, LiKB{sub 4}O{sub 7}, Ca
Luminescence and energy transfer
Energy Technology Data Exchange (ETDEWEB)
Blasse, G; Bleijenberg, K C; Powell, R C
1980-01-01
This paper deals with the luminescence of uranate centres in solids. The luminescence properties are influenced by the coordination number of the hexavalent uranium ion and by the crystallographic surroundings of the uranate centre. Transitions playing a role in the luminescence processes within the octahedral UO/sub 6//sup 6 -/ group are discussed using the results from both theoretical and experimental studies on another octahedral uranium complex: UF/sub 6/. The luminescence of the octahedral uranate group in oxidic compounds is discussed. Attention is paid to the vibrational structure, which is observed in the luminescence spectra at low temperatures and to the temperature quenching of the luminescence. The temperature quenching of the uranate luminescence in uranium-doped tungstates with ordered perovskite structure can be described in terms of a three state single configurational coordinate diagram. The complicated luminescence spectra of uranium-activated sodium fluoride (NaF-U) crystals have been unraveled using chemical variation of the crystal compositions and using site selective laser excitation techniques. Four different luminescent uranate centres have been observed in NaF-U. A model for the configurations of the luminescent centres has been deduced using the results from ionic conductivity experiments.
Puri, Shruti; McMahon, Peter; Yamamoto, Yoshihisa
2014-03-01
The quantum non-demolition (QND) measurement of a single electron spin is of great importance in measurement-based quantum computing schemes. The current single-shot readout demonstrations exhibit substantial spin-flip backaction. We propose a QND readout scheme for quantum dot (QD) electron spins in Faraday geometry, which differs from previous proposals and implementations in that it relies on a novel physical mechanism: the spin-dependent Coulomb exchange interaction between a QD spin and optically-excited quantum well (QW) microcavity exciton-polaritons. The Coulomb exchange interaction causes a spin-dependent shift in the resonance energy of the polarized polaritons, thus causing the phase and intensity response of left circularly polarized light to be different to that of the right circularly polarized light. As a result the QD electron's spin can be inferred from the response to a linearly polarized probe. We show that by a careful design of the system, any spin-flip backaction can be eliminated and a QND measurement of the QD electron spin can be performed within a few 10's of nanoseconds with fidelity 99:95%. This improves upon current optical QD spin readout techniques across multiple metrics, including fidelity, speed and scalability. National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan.
A scheme of quantum state discrimination over specified states via weak-value measurement
Chen, Xi; Dai, Hong-Yi; Liu, Bo-Yang; Zhang, Ming
2018-04-01
The commonly adopted projective measurements are invalid in the specified task of quantum state discrimination when the discriminated states are superposition of planar-position basis states whose complex-number probability amplitudes have the same magnitude but different phases. Therefore we propose a corresponding scheme via weak-value measurement and examine the feasibility of this scheme. Furthermore, the role of the weak-value measurement in quantum state discrimination is analyzed and compared with one in quantum state tomography in this Letter.
The role of scalar product and Wigner distribution in optical and quantum mechanical measurements
International Nuclear Information System (INIS)
Wodkiewicz, K.
1984-01-01
In this paper we present a unified approach to the phase-space description of optical and quantum measurements. We find that from the operational point of view the notion of a time dependent spectrum of light and a joint measurement of position and momentum in quantum mechanics can be formulated in one common approach in which the scalar product, the Wigner function and the phase-space proximity are closely related to a realistic measuring process
Luminescence spectroscopy with synchrotron radiation: History, highlights, future
International Nuclear Information System (INIS)
Zimmerer, Georg
2006-01-01
Luminescence spectroscopy and the investigation of dynamical processes with synchrotron radiation (SR) started about 35 years ago in nearly all SR laboratories existing at that time. In the present paper, the pioneering experiments are particularly emphasized. The exciting development is illustrated presenting highlights for the whole period from the beginning to the present day. The highlights are taken from fields like exciton self-trapping, inelastic electron-electron scattering, optically stimulated desorption, cross luminescence, or probing of cluster properties with luminescence spectroscopic methods. More technological aspects play a role in present day's experiments, like quantum cutting in rare-earth-doped insulators. Promising two-photon excitation and light amplification experiments with SR will be included, as well as the first results obtained in a luminescence experiment with selective Vaccum ultraviolet-free electron laser excitation. Finally, a few ideas concerning the future development of luminescence spectroscopy with SR will be sketched
Europium enabled luminescent nanoparticles for biomedical applications
Energy Technology Data Exchange (ETDEWEB)
Syamchand, S.S., E-mail: syamchand.ss@gmail.com; Sony, G., E-mail: emailtosony@gmail.com
2015-09-15
Lanthanide based nanoparticles are receiving great attention ought to their excellent luminescent and magnetic properties and find challenging biomedical applications. Among the luminescent lanthanide NPs, europium based NPs (Eu-NPs) are better candidates for immunoassay and imaging applications. The Eu-NPs have an edge over quantum dots (QDs) by means of their stable luminescence, long fluorescence lifetime, sharp emission peaks with narrow band width, lack of blinking and biocompatibility. This review surveys the synthesis and properties of a variety of Eu-NPs consolidated from different research articles, for their applications in medicine and biology. The exquisite luminescent properties of Eu-NPs are explored for developing biomedical applications such as immunoassay and bioimaging including multimodal imaging. The biomedical applications of Eu-NPs are mostly diagnostic in nature and mainly focus on various key analytes present in biological systems. The luminescent properties of europium enabled NPs are influenced by a number of factors such as the site symmetry, the metal nanoparticles, metal ions, quantum dots, surfactants, morphology of Eu-NPs, crystal defect, phenomena like antenna effect and physical parameters like temperature. Through this review we explore and assimilate all the factors which affect the luminescence in Eu-NPs and coil a new thread of parameters that control the luminescence in Eu-NPs, which would provide further insight in developing Eu-based nanoprobes for future biomedical prospects. - Highlights: • The review describes 14 major factors that influence the luminescence properties of europium enabled luminescent nanoparticles (Eu-NPs). • Surveys different types of europium containing nanoparticles that have been reported for their biomedical applications. • Eu-NPs are conveniently divided into four different categories, based on the type of the substrates involved. The four categories are (1) virgin Eu-substrate based NPs; (2
Europium enabled luminescent nanoparticles for biomedical applications
International Nuclear Information System (INIS)
Syamchand, S.S.; Sony, G.
2015-01-01
Lanthanide based nanoparticles are receiving great attention ought to their excellent luminescent and magnetic properties and find challenging biomedical applications. Among the luminescent lanthanide NPs, europium based NPs (Eu-NPs) are better candidates for immunoassay and imaging applications. The Eu-NPs have an edge over quantum dots (QDs) by means of their stable luminescence, long fluorescence lifetime, sharp emission peaks with narrow band width, lack of blinking and biocompatibility. This review surveys the synthesis and properties of a variety of Eu-NPs consolidated from different research articles, for their applications in medicine and biology. The exquisite luminescent properties of Eu-NPs are explored for developing biomedical applications such as immunoassay and bioimaging including multimodal imaging. The biomedical applications of Eu-NPs are mostly diagnostic in nature and mainly focus on various key analytes present in biological systems. The luminescent properties of europium enabled NPs are influenced by a number of factors such as the site symmetry, the metal nanoparticles, metal ions, quantum dots, surfactants, morphology of Eu-NPs, crystal defect, phenomena like antenna effect and physical parameters like temperature. Through this review we explore and assimilate all the factors which affect the luminescence in Eu-NPs and coil a new thread of parameters that control the luminescence in Eu-NPs, which would provide further insight in developing Eu-based nanoprobes for future biomedical prospects. - Highlights: • The review describes 14 major factors that influence the luminescence properties of europium enabled luminescent nanoparticles (Eu-NPs). • Surveys different types of europium containing nanoparticles that have been reported for their biomedical applications. • Eu-NPs are conveniently divided into four different categories, based on the type of the substrates involved. The four categories are (1) virgin Eu-substrate based NPs; (2
Squeezing of a nanomechanical resonator by quantum nondemolition measurement and feedback
Ruskov, Rusko; Schwab, Keith; Korotkov, Alexander N.
2005-06-01
We analyze squeezing of the nanoresonator state produced by periodic measurement of position by a quantum point contact or a single-electron transistor. The mechanism of squeezing is the stroboscopic quantum nondemolition measurement generalized to the case of continuous measurement by a weakly coupled detector. The magnitude of squeezing is calculated for the harmonic and stroboscopic modulations of measurement, taking into account detector efficiency and nanoresonator quality factor. We also analyze the operation of the quantum feedback, which prevents fluctuations of the wave packet center due to measurement back-action. Verification of the squeezed state can be performed in almost the same way as its preparation; a similar procedure can also be used for the force detection with sensitivity beyond the standard quantum limit.