WorldWideScience

Sample records for quantum pulse position

  1. Coherent pulse position modulation quantum cipher

    Energy Technology Data Exchange (ETDEWEB)

    Sohma, Masaki; Hirota, Osamu [Quantum ICT Research Institute, Tamagawa University, 6-1-1 Tamagawa-gakuen, Machida, Tokyo 194-8610 (Japan)

    2014-12-04

    On the basis of fundamental idea of Yuen, we present a new type of quantum random cipher, where pulse position modulated signals are encrypted in the picture of quantum Gaussian wave form. We discuss the security of our proposed system with a phase mask encryption.

  2. Passive measurement-device-independent quantum key distribution with orbital angular momentum and pulse position modulation

    Science.gov (United States)

    Wang, Lian; Zhou, Yuan-yuan; Zhou, Xue-jun; Chen, Xiao

    2018-03-01

    Based on the orbital angular momentum and pulse position modulation, we present a novel passive measurement-device-independent quantum key distribution (MDI-QKD) scheme with the two-mode source. Combining with the tight bounds of the yield and error rate of single-photon pairs given in our paper, we conduct performance analysis on the scheme with heralded single-photon source. The numerical simulations show that the performance of our scheme is significantly superior to the traditional MDI-QKD in the error rate, key generation rate and secure transmission distance, since the application of orbital angular momentum and pulse position modulation can exclude the basis-dependent flaw and increase the information content for each single photon. Moreover, the performance is improved with the rise of the frame length. Therefore, our scheme, without intensity modulation, avoids the source side channels and enhances the key generation rate. It has greatly utility value in the MDI-QKD setups.

  3. Quantum Computation with Ultrafast Laser Pulse Shaping

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 6. Quantum Computation with Ultrafast Laser Pulse Shaping. Debabrata Goswami. General Article Volume 10 Issue 6 June 2005 pp 8-14. Fulltext. Click here to view fulltext PDF. Permanent link:

  4. Blind quantum computing with weak coherent pulses.

    Science.gov (United States)

    Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

    2012-05-18

    The universal blind quantum computation (UBQC) protocol [A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual IEEE Symposiumon Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, USA, 2009), pp. 517-526.] allows a client to perform quantum computation on a remote server. In an ideal setting, perfect privacy is guaranteed if the client is capable of producing specific, randomly chosen single qubit states. While from a theoretical point of view, this may constitute the lowest possible quantum requirement, from a pragmatic point of view, generation of such states to be sent along long distances can never be achieved perfectly. We introduce the concept of ϵ blindness for UBQC, in analogy to the concept of ϵ security developed for other cryptographic protocols, allowing us to characterize the robustness and security properties of the protocol under possible imperfections. We also present a remote blind single qubit preparation protocol with weak coherent pulses for the client to prepare, in a delegated fashion, quantum states arbitrarily close to perfect random single qubit states. This allows us to efficiently achieve ϵ-blind UBQC for any ϵ>0, even if the channel between the client and the server is arbitrarily lossy.

  5. Blind Quantum Computing with Weak Coherent Pulses

    Science.gov (United States)

    Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

    2012-05-01

    The universal blind quantum computation (UBQC) protocol [A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual IEEE Symposiumon Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, USA, 2009), pp. 517-526.] allows a client to perform quantum computation on a remote server. In an ideal setting, perfect privacy is guaranteed if the client is capable of producing specific, randomly chosen single qubit states. While from a theoretical point of view, this may constitute the lowest possible quantum requirement, from a pragmatic point of view, generation of such states to be sent along long distances can never be achieved perfectly. We introduce the concept of ɛ blindness for UBQC, in analogy to the concept of ɛ security developed for other cryptographic protocols, allowing us to characterize the robustness and security properties of the protocol under possible imperfections. We also present a remote blind single qubit preparation protocol with weak coherent pulses for the client to prepare, in a delegated fashion, quantum states arbitrarily close to perfect random single qubit states. This allows us to efficiently achieve ɛ-blind UBQC for any ɛ>0, even if the channel between the client and the server is arbitrarily lossy.

  6. Electromagnetic pulse compression and energy localization in quantum plasmas

    International Nuclear Information System (INIS)

    Hefferon, Gareth; Sharma, Ashutosh; Kourakis, Ioannis

    2010-01-01

    The evolution of the intensity of a relativistic laser beam propagating through a dense quantum plasma is investigated, by considering different plasma regimes. A cold quantum fluid plasma and then a thermal quantum description(s) is (are) adopted, in comparison with the classical case of reference. Considering a Gaussian beam cross-section, we investigate both the longitudinal compression and lateral/longitudinal localization of the intensity of a finite-radius electromagnetic pulse. By employing a quantum plasma fluid model in combination with Maxwell's equations, we rely on earlier results on the quantum dielectric response, to model beam-plasma interaction. We present an extensive parametric investigation of the dependence of the longitudinal pulse compression mechanism on the electron density in cold quantum plasmas, and also study the role of the Fermi temperature in thermal quantum plasmas. Our numerical results show pulse localization through a series of successive compression cycles, as the pulse propagates through the plasma. A pulse of 100 fs propagating through cold quantum plasma is compressed to a temporal size of ∼1.35 attosecond and a spatial size of ∼1.08.10 -3 cm. Incorporating Fermi pressure via a thermal quantum plasma model is shown to enhance localization effects. A 100 fs pulse propagating through quantum plasma with a Fermi temperature of 350 K is compressed to a temporal size of ∼0.6 attosecond and a spatial size of ∼2.4.10 -3 cm.

  7. Pulsed homodyne Gaussian quantum tomography with low detection efficiency

    Science.gov (United States)

    Esposito, M.; Benatti, F.; Floreanini, R.; Olivares, S.; Randi, F.; Titimbo, K.; Pividori, M.; Novelli, F.; Cilento, F.; Parmigiani, F.; Fausti, D.

    2014-04-01

    Pulsed homodyne quantum tomography usually requires a high detection efficiency, limiting its applicability in quantum optics. Here, it is shown that the presence of low detection efficiency (<50%) does not prevent the tomographic reconstruction of quantum states of light, specifically, of Gaussian states. This result is obtained by applying the so-called ‘minimax’ adaptive reconstruction of the Wigner function to pulsed homodyne detection. In particular, we prove, by both numerical and real experiments, that an effective discrimination of different Gaussian quantum states can be achieved. Our finding paves the way to a more extensive use of quantum tomographic methods, even in physical situations in which high detection efficiency is unattainable.

  8. Pulsed homodyne Gaussian quantum tomography with low detection efficiency

    International Nuclear Information System (INIS)

    Esposito, M; Benatti, F; Randi, F; Titimbo, K; Pividori, M; Parmigiani, F; Fausti, D; Floreanini, R; Olivares, S; Novelli, F; Cilento, F

    2014-01-01

    Pulsed homodyne quantum tomography usually requires a high detection efficiency, limiting its applicability in quantum optics. Here, it is shown that the presence of low detection efficiency (<50) does not prevent the tomographic reconstruction of quantum states of light, specifically, of Gaussian states. This result is obtained by applying the so-called ‘minimax’ adaptive reconstruction of the Wigner function to pulsed homodyne detection. In particular, we prove, by both numerical and real experiments, that an effective discrimination of different Gaussian quantum states can be achieved. Our finding paves the way to a more extensive use of quantum tomographic methods, even in physical situations in which high detection efficiency is unattainable

  9. Pulsed positive corona streamer propagation and branching

    International Nuclear Information System (INIS)

    Veldhuizen, E.M. van; Rutgers, W.R.

    2002-01-01

    The propagation and branching of pulsed positive corona streamers in a short gap is observed with high resolution in space and time. The appearance of the pre-breakdown phenomena can be controlled by the electrode configuration, the gas composition and the impedance of the pulsed power circuit. In a point-wire gap the positive corona shows much more branching than in the parallel plane gap with a protrusion. In air, the branching is more pronounced than in argon. The pulsed power circuit appears to operate in two modes, either as an inductive circuit creating a lower number of thick streamers or as a resistive circuit giving a higher number of thin streamers. A possible cause for branching is electrostatic repulsion of two parts of the streamer head. The electric field at the streamer head is limited, the maximum values found are ∼170 kV cm -1 in air and ∼100 kV cm -1 in argon. At these maximum field strengths, the electrons have 5-10 eV energy, so the ionization is dominated by two-step processes. Differences between argon and ambient air in the field strength at which streamers propagate are ascribed to the difference in de-excitation processes in noble and molecular gases. The fact that the pulsed power circuit can control the streamer structure is important for applications, but this effect must also be taken into account in fundamental studies of streamer propagation and branching. (author)

  10. Pulsed positive corona streamer propagation and branching

    Energy Technology Data Exchange (ETDEWEB)

    Veldhuizen, E.M. van [Department of Physics, Technische Universiteit Eindhoven, Eindhoven (Netherlands)]. E-mail: e.m.v.veldhuizen@tue.nl; Rutgers, W.R. [Department of Physics, Technische Universiteit Eindhoven, Eindhoven (Netherlands)

    2002-09-07

    The propagation and branching of pulsed positive corona streamers in a short gap is observed with high resolution in space and time. The appearance of the pre-breakdown phenomena can be controlled by the electrode configuration, the gas composition and the impedance of the pulsed power circuit. In a point-wire gap the positive corona shows much more branching than in the parallel plane gap with a protrusion. In air, the branching is more pronounced than in argon. The pulsed power circuit appears to operate in two modes, either as an inductive circuit creating a lower number of thick streamers or as a resistive circuit giving a higher number of thin streamers. A possible cause for branching is electrostatic repulsion of two parts of the streamer head. The electric field at the streamer head is limited, the maximum values found are {approx}170 kV cm{sup -1} in air and {approx}100 kV cm{sup -1} in argon. At these maximum field strengths, the electrons have 5-10 eV energy, so the ionization is dominated by two-step processes. Differences between argon and ambient air in the field strength at which streamers propagate are ascribed to the difference in de-excitation processes in noble and molecular gases. The fact that the pulsed power circuit can control the streamer structure is important for applications, but this effect must also be taken into account in fundamental studies of streamer propagation and branching. (author)

  11. Self triggered single pulse beam position monitor

    International Nuclear Information System (INIS)

    Rothman, J.L.; Blum, E.B.

    1993-01-01

    A self triggered beam position monitor (BPM) has been developed for the NSLS injection system to provide single pulse orbit measurements in the booster synchrotron, linac, and transport lines. The BPM integrates the negative going portion of 3 nS wide bipolar pickup electrode signals. The gated, self triggering feature confines critical timing components to the front end, relaxing external timing specifications. The system features a low noise high speed FET sampler, a fiber optic gate for bunch and turn selection, and an inexpensive interface to a standard PC data acquisition system

  12. Control of trapped-ion quantum states with optical pulses

    International Nuclear Information System (INIS)

    Rangan, C.; Monroe, C.; Bucksbaum, P.H.; Bloch, A.M.

    2004-01-01

    We present new results on the quantum control of systems with infinitely large Hilbert spaces. A control-theoretic analysis of the control of trapped-ion quantum states via optical pulses is performed. We demonstrate how resonant bichromatic fields can be applied in two contrasting ways--one that makes the system completely uncontrollable and the other that makes the system controllable. In some interesting cases, the Hilbert space of the qubit-harmonic oscillator can be made finite, and the Schroedinger equation controllable via bichromatic resonant pulses. Extending this analysis to the quantum states of two ions, a new scheme for producing entangled qubits is discovered

  13. Dynamics of a pulsed continuous-variable quantum memory

    DEFF Research Database (Denmark)

    Dantan, Aurelien Romain; Cviklinski, Jean; Pinard, Michel

    2006-01-01

    We study the transfer dynamics of nonclassical fluctuations of light to the ground-state collective spin components of an atomic ensemble during a pulsed quantum memory sequence, and evaluate the relevant physical quantities to be measured in order to characterize such a quantum memory. We show...... in particular that the fluctuations stored into the atoms are emitted in temporal modes which are always different from those of the readout pulse, but which can nevertheless be retrieved efficiently using a suitable temporal mode-matching technique. We give a simple toy model—a cavity with variable...... transmission—that accounts for the behavior of the atomic quantum memory....

  14. Quantum theory of NMR adiabatic pulses and their applications

    International Nuclear Information System (INIS)

    Ke, Y.

    1993-01-01

    Recently explosive developments of in vivo NMR spectroscopy (NMRS) and imaging (NMRI) in biological and medical sciences have resulted in the establishment of NMR as one of the most advanced major technique in life sciences. These developments have created huge demands for a variety of NMR adiabatic pulses with play a very important role in NMR experiments in vivo. In order to develop new NMR adiabatic pulses, a rigorous systematical quantum theory for this kind of pulses is greatly needed. Providing such a theory is one of the important goals of this dissertation. Quantum density matrix theory and product operator method have been used throughout this dissertation. Another goal, which is the major goal of this thesis research, is to use the quantum theory as a guide to develop new NMR adiabatic pulses and their applications. To fill this goal, a technique to construct a new type of adiabatic pulses, narrow band selective adiabatic pulses, has been invented, which is described through the example of constructing an adiabatic DANTE inversion pulse. This new adiabatic pulse is the first narrow band selective adiabatic pulses: Adiabatic homonuclear and heteronuclear spectral editing sequences. Unique to the first pulse sequence is a B 1 -field filter which is built by using two non-refocusing adiabatic full passage pulses to refocus the wanted signal and dephase unwanted signals. This extra filter greatly enhance the editing efficiency. Unlike commonly used heteronuclear spectral editing sequences which depend on the polarization transfer or spectral subtraction by phase cycling techniques, the second pulse sequences accomplishes the editing of heteronuclear J-coupled signals based on the fact that this sequence is transparent to the uncoupled spins and is equivalent a 90 degrees excitation pulse to the heteronuclear J-coupled spins. Experimental results have confirmed the ability of spectral editing with these two new sequences

  15. Experimental quantum fingerprinting with weak coherent pulses

    Science.gov (United States)

    Xu, Feihu; Arrazola, Juan Miguel; Wei, Kejin; Wang, Wenyuan; Palacios-Avila, Pablo; Feng, Chen; Sajeed, Shihan; Lütkenhaus, Norbert; Lo, Hoi-Kwong

    2015-10-01

    Quantum communication holds the promise of creating disruptive technologies that will play an essential role in future communication networks. For example, the study of quantum communication complexity has shown that quantum communication allows exponential reductions in the information that must be transmitted to solve distributed computational tasks. Recently, protocols that realize this advantage using optical implementations have been proposed. Here we report a proof-of-concept experimental demonstration of a quantum fingerprinting system that is capable of transmitting less information than the best-known classical protocol. Our implementation is based on a modified version of a commercial quantum key distribution system using off-the-shelf optical components over telecom wavelengths, and is practical for messages as large as 100 Mbits, even in the presence of experimental imperfections. Our results provide a first step in the development of experimental quantum communication complexity.

  16. Experimental quantum fingerprinting with weak coherent pulses

    Science.gov (United States)

    Xu, Feihu; Arrazola, Juan Miguel; Wei, Kejin; Wang, Wenyuan; Palacios-Avila, Pablo; Feng, Chen; Sajeed, Shihan; Lütkenhaus, Norbert; Lo, Hoi-Kwong

    2015-01-01

    Quantum communication holds the promise of creating disruptive technologies that will play an essential role in future communication networks. For example, the study of quantum communication complexity has shown that quantum communication allows exponential reductions in the information that must be transmitted to solve distributed computational tasks. Recently, protocols that realize this advantage using optical implementations have been proposed. Here we report a proof-of-concept experimental demonstration of a quantum fingerprinting system that is capable of transmitting less information than the best-known classical protocol. Our implementation is based on a modified version of a commercial quantum key distribution system using off-the-shelf optical components over telecom wavelengths, and is practical for messages as large as 100 Mbits, even in the presence of experimental imperfections. Our results provide a first step in the development of experimental quantum communication complexity. PMID:26515586

  17. Quantum coherence in photo-ionisation with tailored XUV pulses

    Science.gov (United States)

    Carlström, Stefanos; Mauritsson, Johan; Schafer, Kenneth J.; L'Huillier, Anne; Gisselbrecht, Mathieu

    2018-01-01

    Ionisation with ultrashort pulses in the extreme ultraviolet (XUV) regime can be used to prepare an ion in a superposition of spin-orbit substates. In this work, we study the coherence properties of such a superposition, created by ionising xenon atoms using two phase-locked XUV pulses at different frequencies. In general, if the duration of the driving pulse exceeds the quantum beat period, dephasing will occur. If however, the frequency difference of the two pulses matches the spin-orbit splitting, the coherence can be efficiently increased and dephasing does not occur.

  18. Quantum Heterogeneous Computing for Satellite Positioning Optimization

    Science.gov (United States)

    Bass, G.; Kumar, V.; Dulny, J., III

    2016-12-01

    Hard optimization problems occur in many fields of academic study and practical situations. We present results in which quantum heterogeneous computing is used to solve a real-world optimization problem: satellite positioning. Optimization problems like this can scale very rapidly with problem size, and become unsolvable with traditional brute-force methods. Typically, such problems have been approximately solved with heuristic approaches; however, these methods can take a long time to calculate and are not guaranteed to find optimal solutions. Quantum computing offers the possibility of producing significant speed-up and improved solution quality. There are now commercially available quantum annealing (QA) devices that are designed to solve difficult optimization problems. These devices have 1000+ quantum bits, but they have significant hardware size and connectivity limitations. We present a novel heterogeneous computing stack that combines QA and classical machine learning and allows the use of QA on problems larger than the quantum hardware could solve in isolation. We begin by analyzing the satellite positioning problem with a heuristic solver, the genetic algorithm. The classical computer's comparatively large available memory can explore the full problem space and converge to a solution relatively close to the true optimum. The QA device can then evolve directly to the optimal solution within this more limited space. Preliminary experiments, using the Quantum Monte Carlo (QMC) algorithm to simulate QA hardware, have produced promising results. Working with problem instances with known global minima, we find a solution within 8% in a matter of seconds, and within 5% in a few minutes. Future studies include replacing QMC with commercially available quantum hardware and exploring more problem sets and model parameters. Our results have important implications for how heterogeneous quantum computing can be used to solve difficult optimization problems in any

  19. Quantum Computation with Ultrafast Laser Pulse Shaping

    Indian Academy of Sciences (India)

    level quantum systems or 'qubits' that follow the laws of quantum ... physics. Feynman was among the first to attempt to provide an answer to this question by producing an abstract model in 1982 that ... Law was reformulated to mean that rate.

  20. Position-dependent friction in quantum mechanics

    International Nuclear Information System (INIS)

    Srokowski, T.

    1985-01-01

    The quantum description of motion of a particle subjected to position-dependent frictional forces is presented. The two cases are taken into account: a motion without external forces and in the harmonic oscillator field. As an example, a frictional barrier penetration is considered. 16 refs. (author)

  1. Practical system for the generation of pulsed quantum frequency combs.

    Science.gov (United States)

    Roztocki, Piotr; Kues, Michael; Reimer, Christian; Wetzel, Benjamin; Sciara, Stefania; Zhang, Yanbing; Cino, Alfonso; Little, Brent E; Chu, Sai T; Moss, David J; Morandotti, Roberto

    2017-08-07

    The on-chip generation of large and complex optical quantum states will enable low-cost and accessible advances for quantum technologies, such as secure communications and quantum computation. Integrated frequency combs are on-chip light sources with a broad spectrum of evenly-spaced frequency modes, commonly generated by four-wave mixing in optically-excited nonlinear micro-cavities, whose recent use for quantum state generation has provided a solution for scalable and multi-mode quantum light sources. Pulsed quantum frequency combs are of particular interest, since they allow the generation of single-frequency-mode photons, required for scaling state complexity towards, e.g., multi-photon states, and for quantum information applications. However, generation schemes for such pulsed combs have, to date, relied on micro-cavity excitation via lasers external to the sources, being neither versatile nor power-efficient, and impractical for scalable realizations of quantum technologies. Here, we introduce an actively-modulated, nested-cavity configuration that exploits the resonance pass-band characteristic of the micro-cavity to enable a mode-locked and energy-efficient excitation. We demonstrate that the scheme allows the generation of high-purity photons at large coincidence-to-accidental ratios (CAR). Furthermore, by increasing the repetition rate of the excitation field via harmonic mode-locking (i.e. driving the cavity modulation at harmonics of the fundamental repetition rate), we managed to increase the pair production rates (i.e. source efficiency), while maintaining a high CAR and photon purity. Our approach represents a significant step towards the realization of fully on-chip, stable, and versatile sources of pulsed quantum frequency combs, crucial for the development of accessible quantum technologies.

  2. Optimal control of quantum rings by terahertz laser pulses.

    Science.gov (United States)

    Räsänen, E; Castro, A; Werschnik, J; Rubio, A; Gross, E K U

    2007-04-13

    Complete control of single-electron states in a two-dimensional semiconductor quantum-ring model is established, opening a path into coherent laser-driven single-gate qubits. The control scheme is developed in the framework of optimal-control theory for laser pulses of two-component polarization. In terms of pulse lengths and target-state occupations, the scheme is shown to be superior to conventional control methods that exploit Rabi oscillations generated by uniform circularly polarized pulses. Current-carrying states in a quantum ring can be used to manipulate a two-level subsystem at the ring center. Combining our results, we propose a realistic approach to construct a laser-driven single-gate qubit that has switching times in the terahertz regime.

  3. Pulse interactions in a quantum dot waveguide in the regime of electromagnetically Induced transparency

    DEFF Research Database (Denmark)

    Nielsen, Per; Nielsen, Henri; Mørk, Jesper

    2006-01-01

    The interaction of optical pulses in a quantum dot waveguide in the slow-light regime is investigated. Dipole oscillations lead to strong interactions between the two pulses, implying a minimum pulse separation for optical buffer applications.......The interaction of optical pulses in a quantum dot waveguide in the slow-light regime is investigated. Dipole oscillations lead to strong interactions between the two pulses, implying a minimum pulse separation for optical buffer applications....

  4. Positive Cosmological Constant and Quantum Theory

    Directory of Open Access Journals (Sweden)

    Felix M. Lev

    2010-11-01

    Full Text Available We argue that quantum theory should proceed not from a spacetime background but from a Lie algebra, which is treated as a symmetry algebra. Then the fact that the cosmological constant is positive means not that the spacetime background is curved but that the de Sitter (dS algebra as the symmetry algebra is more relevant than the Poincare or anti de Sitter ones. The physical interpretation of irreducible representations (IRs of the dS algebra is considerably different from that for the other two algebras. One IR of the dS algebra splits into independent IRs for a particle and its antiparticle only when Poincare approximation works with a high accuracy. Only in this case additive quantum numbers such as electric, baryon and lepton charges are conserved, while at early stages of the Universe they could not be conserved. Another property of IRs of the dS algebra is that only fermions can be elementary and there can be no neutral elementary particles. The cosmological repulsion is a simple kinematical consequence of dS symmetry on quantum level when quasiclassical approximation is valid. Therefore the cosmological constant problem does not exist and there is no need to involve dark energy or other fields for explaining this phenomenon (in agreement with a similar conclusion by Bianchi and Rovelli.

  5. Robust quantum gates between trapped ions using shaped pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Ping, E-mail: zouping@m.scnu.edu.cn; Zhang, Zhi-Ming, E-mail: zmzhang@scnu.edu.cn

    2015-12-18

    We improve two existing entangling gate schemes between trapped ion qubits immersed in a large linear crystal. Based on the existing two-qubit gate schemes by applying segmented forces on the individually addressed qubits, we present a systematic method to optimize the shapes of the forces to suppress the dominant source of infidelity. The spin-dependent forces in the scheme can be from periodic photon kicks or from continuous optical pulses. The entangling gates are fast, robust, and have high fidelity. They can be used to implement scalable quantum computation and quantum simulation. - Highlights: • We present a systematic method to optimize the shape of the pulses to decouple qubits from intermediary motional modes. • Our optimized scheme can be applied to both the ultrafast gate and fast gate. • Our optimized scheme can suppress the dominant source of infidelity to arbitrary order. • When the number of trapped ions increase, the number of needed segments increases slowly.

  6. Excess quantum noise in optical parametric chirped-pulse amplification

    OpenAIRE

    Manzoni, C.; Moses, J.; Kärtner, F. X.; Cerullo, G.

    2011-01-01

    Noise evolution in an optical parametric chirped-pulse amplifier (OPCPA) differs essentially from that of an optical parametric or a conventional laser amplifier, in that an incoherent pedestal is produced by superfluorescence that can overwhelm the signal under strong saturation. Using a model for the nonlinear dynamics consistent with quantum mechanics, we numerically study the evolution of excess noise in an OPCPA. The observed dynamics explain the macroscopic characteristics seen previous...

  7. On observation of position in quantum theory

    Science.gov (United States)

    Kryukov, A.

    2018-05-01

    Newtonian and Schrödinger dynamics can be formulated in a physically meaningful way within the same Hilbert space framework. This fact was recently used to discover an unexpected relation between classical and quantum motions that goes beyond the results provided by the Ehrenfest theorem. A formula relating the normal probability distribution and the Born rule was also found. Here the dynamical mechanism responsible for the latter formula is proposed and applied to measurements of macroscopic and microscopic systems. A relationship between the classical Brownian motion and the diffusion of state on the space of states is discovered. The role of measuring devices in quantum theory is investigated in the new framework. It is shown that the so-called collapse of the wave function is not measurement specific and does not require a "concentration" near the eigenstates of the measured observable. Instead, it is explained by the common diffusion of a state over the space of states under interaction with the apparatus and the environment. This in turn provides us with a basic reason for the definite position of macroscopic bodies in space.

  8. Position-based quantum cryptography and catalytic computation

    NARCIS (Netherlands)

    Speelman, F.

    2016-01-01

    In this thesis, we present several results along two different lines of research. The first part concerns the study of position-based quantum cryptography, a topic in quantum cryptography. By combining quantum mechanics with special relativity theory, new cryptographic tasks can be developed that

  9. Quantum Logic with Composite Pulse Sequences on Sr^+

    Science.gov (United States)

    Shewmon, Ruth; Labaziewicz, Jaroslaw; Ge, Yufei; Wang, Shannon; Chuang, Isaac L.

    2008-03-01

    The optical 5S1/2->4D1/2 transition in Sr^+ is an attractive qubit because it can be addressed by diode lasers, which are relatively inexpensive and easy to operate. We characterize single-qubit rotations as well as a CNOT gate on a Sr^+ ion in a surface electrode Paul trap. To improve these operations, the frequency of the clock laser is stabilized to a high-finesse optical cavity. The resulting linewidth of the laser is approximately 300Hz. Composite pulse sequences, a technique adapted from NMR, have been shown to reduce the effects of systematic errors in a variety of quantum systems. We demonstrate several composite sequences that improve the fidelity of quantum logic operations on Sr^+.

  10. Nonresonant interaction of ultrashort electromagnetic pulses with multilevel quantum systems

    Science.gov (United States)

    Belenov, E.; Isakov, V.; Nazarkin, A.

    1994-01-01

    Some features of the excitation of multilevel quantum systems under the action of electromagnetic pulses which are shorter than the inverse frequency of interlevel transitions are considered. It is shown that the interaction is characterized by a specific type of selectivity which is not connected with the resonant absorption of radiation. The simplest three-level model displays the inverse population of upper levels. The effect of an ultrashort laser pulse on a multilevel molecule was regarded as an instant reception of the oscillation velocity by the oscillator and this approach showed an effective excitation and dissociation of the molecule. The estimations testify to the fact that these effects can be observed using modern femtosecond lasers.

  11. High current precision long pulse electron beam position monitor

    CERN Document Server

    Nelson, S D; Fessenden, T J; Holmes, C

    2000-01-01

    Precision high current long pulse electron beam position monitoring has typically experienced problems with high Q sensors, sensors damped to the point of lack of precision, or sensors that interact substantially with any beam halo thus obscuring the desired signal. As part of the effort to develop a multi-axis electron beam transport system using transverse electromagnetic stripline kicker technology, it is necessary to precisely determine the position and extent of long high energy beams for accurate beam position control (6 - 40 MeV, 1 - 4 kA, 2 μs beam pulse, sub millimeter beam position accuracy.) The kicker positioning system utilizes shot-to-shot adjustments for reduction of relatively slow (< 20 MHz) motion of the beam centroid. The electron beams passing through the diagnostic systems have the potential for large halo effects that tend to corrupt position measurements.

  12. Fast gas spectroscopy using pulsed quantum cascade lasers

    Science.gov (United States)

    Beyer, T.; Braun, M.; Lambrecht, A.

    2003-03-01

    Laser spectroscopy has found many industrial applications, e.g., control of automotive exhaust and process monitoring. The midinfrared region is of special interest because it has stronger absorption lines compared to the near infrared (NIR). However, in the NIR high quality reliable laser sources, detectors, and passive optical components are available. A quantum cascade laser could change this situation if fundamental advantages can be exploited with compact and reliable systems. It will be shown that, using pulsed lasers and available fast detectors, lower residual sensitivity levels than in corresponding NIR systems can be achieved. The stability is sufficient for industrial applications.

  13. Quantum Noise Reduction with Pulsed Light in Optical Fibers.

    Science.gov (United States)

    Bergman, Keren

    Optical fibers offer considerable advantages over bulk nonlinear media for the generation of squeezed states. This thesis reports on experimental investigations of reducing quantum noise by means of squeezing in nonlinear fiber optic interferometers. Fibers have low insertion loss which allows for long interaction lengths. High field intensities are easily achieved in the small cores of single mode fibers. Additionally, the nonlinear process employed is self phase modulation or the Kerr effect, whose broad band nature requires no phase matching and can be exploited with ultra-short pulses of high peak intensity. All these advantageous features of fibers result in easily obtained large nonlinear phase shifts and subsequently large squeezing parameters. By the self phase modulation process a correlation is produced between the phase and amplitude fluctuations of the optical field. The attenuated or squeezed quadrature has a lower noise level than the initial level associated with the coherent state field before propagation. The resulting reduced quantum noise quadrature can be utilized to improve the sensitivity of a phase measuring instrument such as an interferometer. Because the Kerr nonlinearity is a degenerate self pumping process, the squeezed noise is at the same frequency as the pump field. Classical pump noise can therefore interfere with the desired measurement of the quantum noise reduction. The most severe noise process is the phase noise caused by thermally induced index modulation of the fiber. This noise termed Guided Acoustic Wave Brillouin Scattering, or GAWBS, by previous researchers is studied and analyzed. Experiments performed to overcome GAWBS successfully with several schemes are described. An experimental demonstration of an interferometric measurement with better sensitivity than the standard quantum limit is described. The results lead to new understandings into the limitations of quantum noise reduction that can be achieved in the

  14. Theoretical investigations of quantum correlations in NMR multiple-pulse spin-locking experiments

    Science.gov (United States)

    Gerasev, S. A.; Fedorova, A. V.; Fel'dman, E. B.; Kuznetsova, E. I.

    2018-04-01

    Quantum correlations are investigated theoretically in a two-spin system with the dipole-dipole interactions in the NMR multiple-pulse spin-locking experiments. We consider two schemes of the multiple-pulse spin-locking. The first scheme consists of π /2-pulses only and the delays between the pulses can differ. The second scheme contains φ-pulses (0Quantum discord is obtained for the first scheme of the multiple-pulse spin-locking experiment at different temperatures.

  15. Implementing quantum logic gates with gradient ascent pulse engineering: principles and practicalities.

    Science.gov (United States)

    Rowland, Benjamin; Jones, Jonathan A

    2012-10-13

    We briefly describe the use of gradient ascent pulse engineering (GRAPE) pulses to implement quantum logic gates in nuclear magnetic resonance quantum computers, and discuss a range of simple extensions to the core technique. We then consider a range of difficulties that can arise in practical implementations of GRAPE sequences, reflecting non-idealities in the experimental systems used.

  16. Simulating the inception of pulsed discharges near positive electrodes

    Science.gov (United States)

    Teunissen, Jannis; Ebert, Ute

    2013-09-01

    With 3D particle simulations we study the inception of pulsed discharges near positive electrodes. In different geometries, we first determine the breakdown voltage. Then we study the probability of inception for a fast voltage pulse. This probability mostly depends on the availability of seed electrons to generate the initial electron avalanches. These results are compared with experimental observations. Then we investigate how the shape of a starting discharge affects its further development. In particular, we discuss the formation of so-called ``inception clouds.'' JT was supported by STW-project 10755.

  17. Design of Optical Pulse Position Modulation (PPM) Translating Receiver

    Energy Technology Data Exchange (ETDEWEB)

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V

    2009-06-19

    M-ary pulse position modulation (M-ary PPM) signaling is a means of transmitting multiple bits per symbol in an intensity modulated/direct detection (IM/DD) system. PPM is used in applications with average power limitations. In optical communication systems, PPM becomes challenging to implement at gigabit rates and/or large M, since pulsed signaling requires higher electronic processing bandwidths than the fundamental transmission rate. they have thus been exploring techniques for PPM communications using optical processing. Previous work described a transmitter algorithm that directly translates a bit sequence of N digital bits to the optical pulse position m for any M = 2{sup N}. It has been considerably more difficult to define a similar receiver algorithm that translates the received optical pulse position directly back to a bit sequence with minimal electronic processing. Designs for specific Ms (e.g., 4-ary) have been shown and implemented, but are difficult to scale to larger M. In this work, they present for the first time a generalized PPM translating receiver that is applicable to all M and data rates.

  18. Periodic dark pulse emission induced by delayed feedback in a quantum well semiconductor laser

    Directory of Open Access Journals (Sweden)

    L. Li

    2012-12-01

    Full Text Available We report the experimental observation of periodic dark pulse emission in a quantum-well semiconductor laser with delayed optical feedback. We found that under appropriate operation conditions the laser can also emit a stable train of dark pulses. The repetition frequency of the dark pulse is determined by the external cavity length. Splitting of the dark pulse was also observed. We speculate that the observed dark pulse is a kind of temporal cavity soliton formed in the laser.

  19. Band-selective shaped pulse for high fidelity quantum control in diamond

    International Nuclear Information System (INIS)

    Chang, Yan-Chun; Xing, Jian; Liu, Gang-Qin; Jiang, Qian-Qing; Li, Wu-Xia; Zhang, Fei-Hao; Gu, Chang-Zhi; Pan, Xin-Yu; Long, Gui-Lu

    2014-01-01

    High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host 14 N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevels (e.g., of a nearby 13 C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.

  20. Band-selective shaped pulse for high fidelity quantum control in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yan-Chun; Xing, Jian; Liu, Gang-Qin; Jiang, Qian-Qing; Li, Wu-Xia [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Fei-Hao [Tsinghua National Laboratory for Information Science and Technology, Beijing 100084 (China); State Key Laboratory of Low-Dimensional Physics and Department of Physics, Tsinghua University, Beijing 100084 (China); Gu, Chang-Zhi; Pan, Xin-Yu, E-mail: xypan@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China); Long, Gui-Lu [Tsinghua National Laboratory for Information Science and Technology, Beijing 100084 (China); State Key Laboratory of Low-Dimensional Physics and Department of Physics, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2014-06-30

    High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host {sup 14}N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevels (e.g., of a nearby {sup 13}C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.

  1. Self-slowdown and -advancement of fs pulses in a quantum-dot semiconductor optical amplifier

    DEFF Research Database (Denmark)

    Poel, Mike van der; Mørk, Jesper; Hvam, Jørn Märcher

    2005-01-01

    We demonstrate changes in the propagation time of 180 femtosecond pulses in a quantum-dot semiconductor optical amplifier as function of pulse input power and bias current. The results interpreted as a result of pulse reshaping by gain saturation but are also analogous to coherent population osci...

  2. Controllable delay of ultrashort pulses in a quantum dot optical amplifier

    DEFF Research Database (Denmark)

    Poel, Mike van der; Mørk, Jesper; Hvam, Jørn Märcher

    2005-01-01

    Optical and electrical tuning of the propagation time of 170 fs pulses in a quantum dot semiconductor amplifier at room temperature is demonstrated. Both pulse slowdown and advancement is possible and we achieve fractional delays (delay divided with pulse duration) of up to 40%. The results...

  3. Research for robust femtosecond chirped-pulse amplification laser with an identical positive dispersive media as pulse stretcher and compressor

    International Nuclear Information System (INIS)

    Akahane, Yutaka; Ogawa, Kanade; Tsuji, Koichi; Aoyama, Makoto; Yamakawa, Koichi

    2011-01-01

    We have proposed and demonstrated a simple and robust femtosecond optical-parametric chirped-pulse amplification scheme in which an even order dispersion of an idler pulse is compensated by passing through an identical positive dispersive material used for temporal stretching a signal pulse. By compressing the idler pulses having a negatively chirp in this manner, high power sub-100 fs pulses were successfully obtained with only a transparent glass block used for the stretcher and compressor. (author)

  4. 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

  5. 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.

  6. Classical and quantum position-dependent mass harmonic oscillators

    International Nuclear Information System (INIS)

    Cruz y Cruz, S.; Negro, J.; Nieto, L.M.

    2007-01-01

    The position-dependent mass oscillator is studied from both, classical and quantum mechanical points of view, in order to discuss the ambiguity on the operator ordering of the kinetic term in the quantum framework. The results are illustrated by some examples of specific mass functions

  7. Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

    Science.gov (United States)

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-02-01

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a ``super pressing'' state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.

  8. Some quantum Lie algebras of type Dn positive

    International Nuclear Information System (INIS)

    Bautista, Cesar; Juarez-Ramirez, Maria Araceli

    2003-01-01

    A quantum Lie algebra is constructed within the positive part of the Drinfeld-Jimbo quantum group of type D n . Our quantum Lie algebra structure includes a generalized antisymmetry property and a generalized Jacobi identity closely related to the braid equation. A generalized universal enveloping algebra of our quantum Lie algebra of type D n positive is proved to be the Drinfeld-Jimbo quantum group of the same type. The existence of such a generalized Lie algebra is reduced to an integer programming problem. Moreover, when the integer programming problem is feasible we show, by means of the generalized Jacobi identity, that the Poincare-Birkhoff-Witt theorem (basis) is still true

  9. Population Transfer between Two Quantum States by Piecewise Chirping of Femtosecond Pulses: Theory and Experiment

    International Nuclear Information System (INIS)

    Zhdanovich, S.; Shapiro, E. A.; Shapiro, M.; Hepburn, J. W.; Milner, V.

    2008-01-01

    We propose and experimentally demonstrate the method of population transfer by piecewise adiabatic passage between two quantum states. Coherent excitation of a two-level system with a train of ultrashort laser pulses is shown to reproduce the effect of an adiabatic passage, conventionally achieved with a single frequency-chirped pulse. By properly adjusting the amplitudes and phases of the pulses in the excitation pulse train, we achieve complete and robust population transfer to the target state. The piecewise nature of the process suggests a possibility for the selective population transfer in complex quantum systems

  10. Laboratory transferability of optimally shaped laser pulses for quantum control

    International Nuclear Information System (INIS)

    Moore Tibbetts, Katharine; Xing, Xi; Rabitz, Herschel

    2014-01-01

    Optimal control experiments can readily identify effective shaped laser pulses, or “photonic reagents,” that achieve a wide variety of objectives. An important additional practical desire is for photonic reagent prescriptions to produce good, if not optimal, objective yields when transferred to a different system or laboratory. Building on general experience in chemistry, the hope is that transferred photonic reagent prescriptions may remain functional even though all features of a shaped pulse profile at the sample typically cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments. First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found to still produce near optimal yields on the second laser system. Third, transferring a collection of photonic reagents optimized on the first laser system to the second laser system reproduced systematic trends in photoproduct yields upon interaction with the homologous chemical family. These three transfers of photonic reagents are demonstrated to be successful upon paying reasonable attention to overall laser system characteristics. The ability to transfer photonic reagents from one laser system to another is analogous to well-established utilitarian operating procedures with traditional chemical reagents. The practical implications of the present results for experimental quantum control are discussed

  11. Quantum wave packet revival in two-dimensional circular quantum wells with position-dependent mass

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Alexandre G.M. [Departamento de Ciencias Exatas, Polo Universitario de Volta Redonda-Universidade Federal Fluminense, Av. dos Trabalhadores 420, Volta Redonda RJ, CEP 27255-125 (Brazil)], E-mail: agmschmidt@gmail.com; Azeredo, Abel D. [Departamento de Fisica-Universidade Federal de Roraima, Av. Cap. Ene Garcez 2413, Boa Vista RR, CEP 69304-000 (Brazil)], E-mail: aazeredo@gmail.com; Gusso, A. [Departamento de Ciencias Exatas e Tecnologicas-Universidade Estadual de Santa Cruz, km 16 Rodovia Ilheus-Itabuna, Ilheus BA, CEP 45662-000 (Brazil)], E-mail: agusso@uesc.br

    2008-04-14

    We study quantum wave packet revivals on two-dimensional infinite circular quantum wells (CQWs) and circular quantum dots with position-dependent mass (PDM) envisaging a possible experimental realization. We consider CQWs with radially varying mass, addressing particularly the cases where M(r){proportional_to}r{sup w} with w=1,2, or -2. The two PDM Hamiltonians currently allowed by theory were analyzed and we were able to construct a strong theoretical argument favoring one of them.

  12. Quantum wave packet revival in two-dimensional circular quantum wells with position-dependent mass

    International Nuclear Information System (INIS)

    Schmidt, Alexandre G.M.; Azeredo, Abel D.; Gusso, A.

    2008-01-01

    We study quantum wave packet revivals on two-dimensional infinite circular quantum wells (CQWs) and circular quantum dots with position-dependent mass (PDM) envisaging a possible experimental realization. We consider CQWs with radially varying mass, addressing particularly the cases where M(r)∝r w with w=1,2, or -2. The two PDM Hamiltonians currently allowed by theory were analyzed and we were able to construct a strong theoretical argument favoring one of them

  13. Dual-Pulse Pulse Position Modulation (DPPM) for Deep-Space Optical Communications: Performance and Practicality Analysis

    Science.gov (United States)

    Li, Jing; Hylton, Alan; Budinger, James; Nappier, Jennifer; Downey, Joseph; Raible, Daniel

    2012-01-01

    Due to its simplicity and robustness against wavefront distortion, pulse position modulation (PPM) with photon counting detector has been seriously considered for long-haul optical wireless systems. This paper evaluates the dual-pulse case and compares it with the conventional single-pulse case. Analytical expressions for symbol error rate and bit error rate are first derived and numerically evaluated, for the strong, negative-exponential turbulent atmosphere; and bandwidth efficiency and throughput are subsequently assessed. It is shown that, under a set of practical constraints including pulse width and pulse repetition frequency (PRF), dual-pulse PPM enables a better channel utilization and hence a higher throughput than it single-pulse counterpart. This result is new and different from the previous idealistic studies that showed multi-pulse PPM provided no essential information-theoretic gains than single-pulse PPM.

  14. Modelling and characterization of colliding-pulse mode-locked (CPM) quantum well lasers. [MPS1

    DEFF Research Database (Denmark)

    Bischoff, Svend; Brorson, S.D.; Franck, T.

    1996-01-01

    A theoretical and experimental study of passive colliding pulse mode-locked quantum well lasers is presented. The theoretical model for the gain dynamics is based on semi-classical density matrixequations. The gain dynamics are characterized exp...

  15. Free space relativistic quantum cryptography with faint laser pulses

    International Nuclear Information System (INIS)

    Molotkov, S N; Potapova, T A

    2013-01-01

    A new protocol for quantum key distribution through empty space is proposed. Apart from the quantum mechanical restrictions on distinguishability of non-orthogonal states, the protocol employs additional restrictions imposed by special relativity. The protocol ensures generation of a secure key even for the source generating non-strictly single-photon quantum states and for arbitrary losses in quantum communication channel. (letter)

  16. Antibacterial Activity of Silver-Graphene Quantum Dots Nanocomposites Against Gram-Positive and Gram-Negative Bacteria

    Science.gov (United States)

    Habiba, Khaled (Inventor); Makarov, Vladimir (Inventor); Weiner, Brad R (Inventor); Morell, Gerardo (Inventor)

    2018-01-01

    The invention provides a composite of silver nanoparticles decorated with graphene quantum dots (Ag-GQDs) using pulsed laser synthesis. The nanocomposites were functionalized with polyethylene glycol (PEG). A concentration of 150 .mu.g/mL of Ag-GQDs, a non-toxic level for human cells, exhibits strong antibacterial activity against both Gram-Positive and Gram-Negative Bacteria.

  17. Quantum ring states in magnetic field and delayed half-cycle pulses

    Indian Academy of Sciences (India)

    2016-07-19

    Jul 19, 2016 ... A very important aspect of the present work is the persistent current generation in a quantum ring in the presence ... quantum effects and their energy spectra are discrete. They are in many .... small with respect to its rotational time period, hence .... of delayed half-cycle pulse pair of the electric field. E0 = 1.0 ...

  18. Positive Wigner functions render classical simulation of quantum computation efficient.

    Science.gov (United States)

    Mari, A; Eisert, J

    2012-12-07

    We show that quantum circuits where the initial state and all the following quantum operations can be represented by positive Wigner functions can be classically efficiently simulated. This is true both for continuous-variable as well as discrete variable systems in odd prime dimensions, two cases which will be treated on entirely the same footing. Noting the fact that Clifford and Gaussian operations preserve the positivity of the Wigner function, our result generalizes the Gottesman-Knill theorem. Our algorithm provides a way of sampling from the output distribution of a computation or a simulation, including the efficient sampling from an approximate output distribution in the case of sampling imperfections for initial states, gates, or measurements. In this sense, this work highlights the role of the positive Wigner function as separating classically efficiently simulable systems from those that are potentially universal for quantum computing and simulation, and it emphasizes the role of negativity of the Wigner function as a computational resource.

  19. Relativistic quantum similarities in atoms in position and momentum spaces

    International Nuclear Information System (INIS)

    Maldonado, P.; Sarsa, A.; Buendia, E.; Galvez, F.J.

    2011-01-01

    A study of different quantum similarity measures and their corresponding quantum similarity indices is carried out for the atoms from H to Lr (Z=1-103). Relativistic effects in both position and momentum spaces have been studied by comparing the relativistic values to the non-relativistic ones. We have used the atomic electron density in both position and momentum spaces obtained within relativistic and non-relativistic numerical-parameterized optimized effective potential approximations. -- Highlights: → Quantum similarity measures and indices in electronic structure of atoms. → Position and momentum electronic densities. → Similarity of relativistic and non-relativistic densities. → Similarity of core and valence regions of different atoms. → Dependence with Z along the Periodic Table.

  20. Inception behaviour of pulsed positive corona in several gases

    International Nuclear Information System (INIS)

    Veldhuizen, E M van; Rutgers, W R

    2003-01-01

    The inception probability and the streamer length of pulsed positive corona discharges is determined in argon, nitrogen, oxygen and air. This study is performed in a 25 mm point-plane gap at a pressure of 1 bar. The lowest voltage at which a discharge in argon starts is 3 kV but only with an inception probability of 1%. At 5 kV the corona discharge in argon transforms into a spark with a probability close to 100%. The inception probability of corona discharges in all molecular gases used here as a function of the voltage is identical, starting with 1% at 4 kV and going up to 100% at 9 kV. The streamer lengths are quite different for these gases, nitrogen requiring the lowest voltage for streamers to cross the gap and oxygen the highest. This is probably due to electron attachment in oxygen. A remarkable result is that in air streamers bridge the gap at 8 kV, but spark breakdown occurs only above 26 kV. This property makes it relatively easy to obtain powerful pulsed corona discharges in air

  1. Inception behaviour of pulsed positive corona in several gases

    Energy Technology Data Exchange (ETDEWEB)

    Veldhuizen, E M van; Rutgers, W R [Technische Universiteit Eindhoven, PO Box 513, 5600 MB Eindhoven (Netherlands)

    2003-11-07

    The inception probability and the streamer length of pulsed positive corona discharges is determined in argon, nitrogen, oxygen and air. This study is performed in a 25 mm point-plane gap at a pressure of 1 bar. The lowest voltage at which a discharge in argon starts is 3 kV but only with an inception probability of 1%. At 5 kV the corona discharge in argon transforms into a spark with a probability close to 100%. The inception probability of corona discharges in all molecular gases used here as a function of the voltage is identical, starting with 1% at 4 kV and going up to 100% at 9 kV. The streamer lengths are quite different for these gases, nitrogen requiring the lowest voltage for streamers to cross the gap and oxygen the highest. This is probably due to electron attachment in oxygen. A remarkable result is that in air streamers bridge the gap at 8 kV, but spark breakdown occurs only above 26 kV. This property makes it relatively easy to obtain powerful pulsed corona discharges in air.

  2. Effect of laser pulse shaping parameters on the fidelity of quantum logic gates.

    Science.gov (United States)

    Zaari, Ryan R; Brown, Alex

    2012-09-14

    The effect of varying parameters specific to laser pulse shaping instruments on resulting fidelities for the ACNOT(1), NOT(2), and Hadamard(2) quantum logic gates are studied for the diatomic molecule (12)C(16)O. These parameters include varying the frequency resolution, adjusting the number of frequency components and also varying the amplitude and phase at each frequency component. A time domain analytic form of the original discretized frequency domain laser pulse function is derived, providing a useful means to infer the resulting pulse shape through variations to the aforementioned parameters. We show that amplitude variation at each frequency component is a crucial requirement for optimal laser pulse shaping, whereas phase variation provides minimal contribution. We also show that high fidelity laser pulses are dependent upon the frequency resolution and increasing the number of frequency components provides only a small incremental improvement to quantum gate fidelity. Analysis through use of the pulse area theorem confirms the resulting population dynamics for one or two frequency high fidelity laser pulses and implies similar dynamics for more complex laser pulse shapes. The ability to produce high fidelity laser pulses that provide both population control and global phase alignment is attributed greatly to the natural evolution phase alignment of the qubits involved within the quantum logic gate operation.

  3. Ozone production process in pulsed positive dielectric barrier discharge

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Ryo [High Temperature Plasma Center, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 227-8568 (Japan); Oda, Tetsuji [Department of Electrical Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 (Japan)

    2007-01-07

    The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O{sub 2} + M {yields} O{sub 3} + M, is estimated to be 2.5 x 10{sup -34} cm{sup 6} s{sup -1}.

  4. Ozone production process in pulsed positive dielectric barrier discharge

    Science.gov (United States)

    Ono, Ryo; Oda, Tetsuji

    2007-01-01

    The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O2 + M → O3 + M, is estimated to be 2.5 × 10-34 cm6 s-1.

  5. Ozone production process in pulsed positive dielectric barrier discharge

    International Nuclear Information System (INIS)

    Ono, Ryo; Oda, Tetsuji

    2007-01-01

    The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O 2 + M → O 3 + M, is estimated to be 2.5 x 10 -34 cm 6 s -1

  6. Quantum phase amplification for temporal pulse shaping and super-resolution in remote sensing

    Science.gov (United States)

    Yin, Yanchun

    The use of nonlinear optical interactions to perform nonclassical transformations of electromagnetic field is an area of considerable interest. Quantum phase amplification (QPA) has been previously proposed as a method to perform nonclassical manipulation of coherent light, which can be experimentally realized by use of nonlinear optical mixing processes, of which phase-sensitive three-wave mixing (PSTWM) is one convenient choice. QPA occurs when PSTWM is operated in the photon number deamplification mode, i.e., when the energy is coherently transferred among the low-frequency signal and idler waves and the high-frequency pump wave. The final state is nonclassical, with the field amplitude squeezed and the phase anti-squeezed. In the temporal domain, the use of QPA has been studied to facilitate nonlinear pulse shaping. This novel method directly shapes the temporal electric field amplitude and phase using the PSTWM in a degenerate and collinear configuration, which has been analyzed using a numerical model. Several representative pulse shaping capabilities of this technique have been identified, which can augment the performance of common passive pulse shaping methods operating in the Fourier domain. The analysis indicates that a simple quadratic variation of temporal phase facilitates pulse compression and self-steepening, with features significantly shorter than the original transform-limited pulse. Thus, PSTWM can act as a direct pulse compressor based on the combined effects of phase amplification and group velocity mismatch, even without the subsequent linear phase compensation. Furthermore, it is shown numerically that pulse doublets and pulse trains can be produced at the pump frequency by utilizing the residual linear phase of the signal. Such pulse shaping capabilities are found to be within reach of this technique in common nonlinear optical crystals pumped by pulses available from compact femtosecond chirped-pulse amplification laser systems. The use of

  7. Quantum interference of position and momentum: A particle propagation paradox

    Science.gov (United States)

    Hofmann, Holger F.

    2017-08-01

    Optimal simultaneous control of position and momentum can be achieved by maximizing the probabilities of finding their experimentally observed values within two well-defined intervals. The assumption that particles move along straight lines in free space can then be tested by deriving a lower limit for the probability of finding the particle in a corresponding spatial interval at any intermediate time t . Here, it is shown that this lower limit can be violated by quantum superpositions of states confined within the respective position and momentum intervals. These violations of the particle propagation inequality show that quantum mechanics changes the laws of motion at a fundamental level, providing a different perspective on causality relations and time evolution in quantum mechanics.

  8. Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory

    Science.gov (United States)

    Tang, Jian-Shun; Zhou, Zong-Quan; Wang, Yi-Tao; Li, Yu-Long; Liu, Xiao; Hua, Yi-Lin; Zou, Yang; Wang, Shuang; He, De-Yong; Chen, Geng; Sun, Yong-Nan; Yu, Ying; Li, Mi-Feng; Zha, Guo-Wei; Ni, Hai-Qiao; Niu, Zhi-Chuan; Li, Chuan-Feng; Guo, Guang-Can

    2015-01-01

    Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by the Duan–Lukin–Cirac–Zoller protocol, many improved quantum repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multiple photons (or multiple photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Here, we demonstrate the storage of deterministic single photons emitted from a quantum dot in a polarization-maintaining solid-state quantum memory; in addition, multi-temporal-mode memory with 1, 20 and 100 narrow single-photon pulses is also demonstrated. Multi-photons are eliminated, and only one photon at most is contained in each pulse. Moreover, the solid-state properties of both sub-systems make this configuration more stable and easier to be scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devices. PMID:26468996

  9. Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode.

    Science.gov (United States)

    Abellán, C; Amaya, W; Jofre, M; Curty, M; Acín, A; Capmany, J; Pruneri, V; Mitchell, M W

    2014-01-27

    We demonstrate a high bit-rate quantum random number generator by interferometric detection of phase diffusion in a gain-switched DFB laser diode. Gain switching at few-GHz frequencies produces a train of bright pulses with nearly equal amplitudes and random phases. An unbalanced Mach-Zehnder interferometer is used to interfere subsequent pulses and thereby generate strong random-amplitude pulses, which are detected and digitized to produce a high-rate random bit string. Using established models of semiconductor laser field dynamics, we predict a regime of high visibility interference and nearly complete vacuum-fluctuation-induced phase diffusion between pulses. These are confirmed by measurement of pulse power statistics at the output of the interferometer. Using a 5.825 GHz excitation rate and 14-bit digitization, we observe 43 Gbps quantum randomness generation.

  10. Peak Source Power Associated with Positive Narrow Bipolar Lightning Pulses

    Science.gov (United States)

    Bandara, S. A.; Marshall, T. C.; Karunarathne, S.; Karunarathne, N. D.; Siedlecki, R. D., II; Stolzenburg, M.

    2017-12-01

    During the summer of 2016, we deployed a lightning sensor array in and around Oxford Mississippi, USA. The array system comprised seven lightning sensing stations in a network approximately covering an area of 30 km × 30 km. Each station is equipped with four sensors: Fast antenna (10 ms decay time), Slow antenna (1.0 s decay time)), field derivative sensor (dE/dt) and Log-RF antenna (bandwidth 187-192 MHz). We have observed 319 Positive NBPs and herein we report on comparisons of the NBP properties measured from the Fast antenna data with the Log-RF antenna data. These properties include 10-90% rise time, full width at half maximum, zero cross time, and range-normalized amplitude at 100 km. NBPs were categorized according to the fine structure of the electric field wave shapes into Types A-D, as in Karunarathne et al. [2015]. The source powers of NBPs in each category were determined using single station Log-RF data. Furthermore, we also categorized the NBPs in three other groups: initial event of an IC flash, isolated, and not-isolated (according to their spatiotemporal relationship with other lightning activity). We compared the source powers within each category. Karunarathne, S., T. C. Marshall, M. Stolzenburg, and N. Karunarathna (2015), Observations of positive narrow bipolar pulses, J. Geophys. Res. Atmos., 120, doi:10.1002/2015JD023150.

  11. Position-based quantum cryptography over untrusted networks

    International Nuclear Information System (INIS)

    Nadeem, Muhammad

    2014-01-01

    In this article, we propose quantum position verification (QPV) schemes where all the channels are untrusted except the position of the prover and distant reference stations of verifiers. We review and analyze the existing QPV schemes containing some pre-shared data between the prover and verifiers. Most of these schemes are based on non-cryptographic assumptions, i.e. quantum/classical channels between the verifiers are secure. It seems impractical in an environment fully controlled by adversaries and would lead to security compromise in practical implementations. However, our proposed formula for QPV is more robust, secure and according to the standard assumptions of cryptography. Furthermore, once the position of the prover is verified, our schemes establish secret keys in parallel and can be used for authentication and secret communication between the prover and verifiers. (paper)

  12. Unconditionally secure commitment in position-based quantum cryptography.

    Science.gov (United States)

    Nadeem, Muhammad

    2014-10-27

    A new commitment scheme based on position-verification and non-local quantum correlations is presented here for the first time in literature. The only credential for unconditional security is the position of committer and non-local correlations generated; neither receiver has any pre-shared data with the committer nor does receiver require trusted and authenticated quantum/classical channels between him and the committer. In the proposed scheme, receiver trusts the commitment only if the scheme itself verifies position of the committer and validates her commitment through non-local quantum correlations in a single round. The position-based commitment scheme bounds committer to reveal valid commitment within allocated time and guarantees that the receiver will not be able to get information about commitment unless committer reveals. The scheme works for the commitment of both bits and qubits and is equally secure against committer/receiver as well as against any third party who may have interests in destroying the commitment. Our proposed scheme is unconditionally secure in general and evades Mayers and Lo-Chau attacks in particular.

  13. Quantum computer based on activated dielectric nanoparticles selectively interacting with short optical pulses

    International Nuclear Information System (INIS)

    Gadomskii, Oleg N; Kharitonov, Yu Ya

    2004-01-01

    The operation principle of a quantum computer is proposed based on a system of dielectric nanoparticles activated with two-level atoms - cubits, in which electric dipole transitions are excited by short intense optical pulses. It is proved that the logical operation (logical operator) CNOT (controlled NOT) is performed by means of time-dependent transfer of quantum information over 'long' (of the order of 10 4 nm) distances between spherical nanoparticles owing to the delayed interaction between them in the optical radiation field. It is shown that one-cubit and two-cubit logical operators required for quantum calculations can be realised by selectively exciting dielectric particles with short optical pulses. (quantum calculations)

  14. Coherent dynamics and terahertz emission in an asymmetric quantum well coupled to broadband infrared pulses

    International Nuclear Information System (INIS)

    Wu, B H; Cao, J C

    2004-01-01

    A selected intersubband transition in the asymmetric quantum well is theoretically proposed by using the superposition of two identical time delayed and phase shifted broadband pulses. Three conduction subbands in the semiconductor quantum well structure are optically coupled with the ultrafast infrared pulses. By adjusting the delay between these two pulses, the carriers at ground level can be selectively pumped to one of the upper levels, while the other upper level remains unoccupied. Thus selective transitions in the three level model can be manipulated by optical interference. At the same time, terahertz radiation will be emitted by coherent controlled charge oscillations. The phase and amplitude of THz radiation is found to be sensitive to the optical interference of the coupling pulses

  15. Influence of the nuclear Zeeman effect on mode locking in pulsed semiconductor quantum dots

    Science.gov (United States)

    Beugeling, Wouter; Uhrig, Götz S.; Anders, Frithjof B.

    2017-09-01

    The coherence of the electron spin in a semiconductor quantum dot is strongly enhanced by mode locking through nuclear focusing, where the synchronization of the electron spin to periodic pulsing is slowly transferred to the nuclear spins of the semiconductor material, mediated by the hyperfine interaction between these. The external magnetic field that drives the Larmor oscillations of the electron spin also subjects the nuclear spins to a Zeeman-like coupling, albeit a much weaker one. For typical magnetic fields used in experiments, the energy scale of the nuclear Zeeman effect is comparable to that of the hyperfine interaction, so that it is not negligible. In this work, we analyze the influence of the nuclear Zeeman effect on mode locking quantitatively. Within a perturbative framework, we calculate the Overhauser-field distribution after a prolonged period of pulsing. We find that the nuclear Zeeman effect can exchange resonant and nonresonant frequencies. We distinguish between models with a single type and with multiple types of nuclei. For the latter case, the positions of the resonances depend on the individual g factors, rather than on the average value.

  16. Increasing the bit rate in OCDMA systems using pulse position modulation techniques.

    Science.gov (United States)

    Arbab, Vahid R; Saghari, Poorya; Haghi, Mahta; Ebrahimi, Paniz; Willner, Alan E

    2007-09-17

    We have experimentally demonstrated two novel pulse position modulation techniques, namely Double Pulse Position Modulation (2-PPM) and Differential Pulse Position Modulation (DPPM) in Time-Wavelength OCDMA systems that will operate at a higher bit rate compared to traditional OOK-OCDMA systems with the same bandwidth. With 2-PPM technique, the number of active users will be more than DPPM while their bit rate is almost the same. Both techniques provide variable quality of service in OCDMA networks.

  17. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

    Science.gov (United States)

    Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

    2007-07-27

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

  18. Quantum state population transfer of lithium atoms induced by frequency-chirped laser pulses

    International Nuclear Information System (INIS)

    Ma Huanqiang; Zhang Xianzhou; Jia Guangrui; Zhang Yonghui; Jiang Lijuan

    2011-01-01

    Using the time-dependent multilevel approach (TDMA) and B-splines function, we have calculated the five quantum state population transfer of rydberg lithium atoms. We also analyse the influence of the four major parameters of the frequency-chirped laser pulses field on transition. The result shows that the population can be completely transferred to the target state by changing the parameters of the laser pulse and achieve manual controls to a certain degree. (authors)

  19. 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

  20. Optical pulse dynamics for quantum-dot logic operations in a photonic-crystal waveguide

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xun; John, Sajeev [Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 Canada (Canada)

    2011-11-15

    We numerically demonstrate all-optical logic operations with quantum dots (QDs) embedded in a bimodal photonic-crystal waveguide using Maxwell-Bloch equations in a slowly varying envelope approximation (SVEA). The two-level QD excitation level is controlled by one or more femtojoule optical driving pulses passing through the waveguide. Specific logic operations depend on the relative pulse strengths and their detunings from an inhomogeneouslly broadened (about 1% for QD transitions centered at 1.5 {mu}m) QD transition. This excitation controlled two-level medium then determines passage of subsequent probe optical pulses. Envelope equations for electromagnetic waves in the linear dispersion and cutoff waveguide modes are derived to simplify solution of the coupled Maxwell-Bloch equations in the waveguide. These determine the quantum mechanical evolution of the QD excitation and its polarization, driven by classical electromagnetic (EM) pulses near a sharp discontinuity in the EM density of states of the bimodal waveguide. Different configurations of the driving pulses lead to distinctive relations between driving pulse strength and probe pulse passage, representing all-optical logic and, or, and not operations. Simulation results demonstrate that such operations can be done on picosecond time scales and within a waveguide length of about 10 {mu}m in a photonic-band-gap (PBG) optical microchip.

  1. Quantum interference metrology at deep-UV wavelengths using phase-controlled ultrashort laser pulses

    NARCIS (Netherlands)

    Zinkstok, R. Th; Witte, S.; Ubachs, W.; Hogervorst, W.; Eikema, K. S E

    2005-01-01

    High-resolution metrology at wavelengths shorter than ultraviolet is in general hampered by a limited availability of appropriate laser sources. It is demonstrated that this limitation can be overcome by quantum-interference metrology with frequency up-converted ultrafast laser pulses. The required

  2. The effect of positive end-expiratory pressure on pulse pressure ...

    African Journals Online (AJOL)

    The effect of positive end-expiratory pressure on pulse pressure variation. FJ Smith, M Geyser, I Schreuder, PJ Becker. Abstract. Objectives: To determine the effect of different levels of positive end-expiratory pressure (PEEP) on pulse pressure variation (PPV). Design: An observational study. Setting: Operating theatres of a ...

  3. Quantum energy duplication using super high output pulse laser

    International Nuclear Information System (INIS)

    Sugisaki, Kiwamu; Koyama, Kazuyoshi; Tanimoto, Mitsumori; Saito, Naoaki

    2000-01-01

    This study aims at elucidation on phenomena induced by strong electric field of super high output ultra short laser pulse to carry out development of basic technology required for promotion of a study on generation of high energy particle and photon using them, in order to contribute to application of super high output ultra short laser pulse and high energy plasma formed by it. In 1998 fiscal year of the last fiscal year in this study, by intending to increase the output by narrowing pulse width of the super high output laser, some basic experiments such as verification due to experiment on relativity theoretical self-convergence, generation of high energy particles, and so forth were carried out to establish a forecasting on future application. And, by conducting plasma generation experiment, self-guide and high energy particle formation experiment in plasma of super high intensity laser pulse important for its applications, and so forth, various technologies constituting foundation of future developments were developed, and more results could be obtained than those at proposal of this study. (G.K.)

  4. Optimal control of quantum systems by chirped pulses

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Doll, J. D.; Sauerbrey, R. A.

    1993-01-01

    treated are pulsed population inversion between electronic levels, and optimization of vibronic excitation in the presence of another electronic level. In the problem of population inversion effective potentials of displaced harmonic oscillators are used. For optimizing vibronic excitation the CsI model...

  5. Electromagnetic pulse-driven spin-dependent currents in semiconductor quantum rings.

    Science.gov (United States)

    Zhu, Zhen-Gang; Berakdar, Jamal

    2009-04-08

    We investigate the non-equilibrium charge and spin-dependent currents in a quantum ring with a Rashba spin-orbit interaction (SOI) driven by two asymmetric picosecond electromagnetic pulses. The equilibrium persistent charge and persistent spin-dependent currents are investigated as well. It is shown that the dynamical charge and the dynamical spin-dependent currents vary smoothly with a static external magnetic flux and the SOI provides a SU(2) effective flux that changes the phases of the dynamic charge and the dynamic spin-dependent currents. The period of the oscillation of the total charge current with the delay time between the pulses is larger in a quantum ring with a larger radius. The parameters of the pulse fields control to a certain extent the total charge and the total spin-dependent currents. The calculations are applicable to nanometre rings fabricated in heterojunctions of III-V and II-VI semiconductors containing several hundreds of electrons.

  6. Theory of Pulse Train Amplification Without Patterning Effects in Quantum Dot Semiconductor Optical Amplifiers

    DEFF Research Database (Denmark)

    Uskov, Alexander V.; Berg, Tommy Winther; Mørk, Jesper

    2004-01-01

    A theory for pulse amplification and saturation in quantum dot (QD) semiconductor optical amplifiers (SOAs) is developed. In particular, the maximum bit rate at which a data stream of pulses can be amplified without significant patterning effects is investigated. Simple expressions are derived th...... energies of 0.2–0.4 pJ. The superiority of QD SOAs is based on: 1) the faster achievement of the regime of maximum gain in QD SOAs compared to QW and bulk SOAs and 2) the lower effective cross section of photon-carrier interaction in QDs....... that clearly show the dependence of the maximum bit rate on material and device parameters. A comparative analysis of QD, quantum well (QW), and bulk SOAs shows that QD SOAs may have superior properties; calculations predict patterning-free amplification up to bit rates of 150–200 Gb/s with pulse output...

  7. Positive staining for cellulose in oral pulse granuloma

    DEFF Research Database (Denmark)

    Virkkunen, Sirke; Wolff, Henrik; Haglund, Caj

    2017-01-01

    Objective: Oral pulse granuloma (OPG) is an oral inflammatory lesion characterized by the presence of hyaline rings with numerous multinucleated giant cells. The etiopathogenesis of this lesion is thus far unclear, as is the composition of the hyaline rings. Our aim was to investigate whether...

  8. First results from Position-Sensitive quantum calorimeters using Mo/Au Transition-Edge Sensors

    International Nuclear Information System (INIS)

    Figueroa-Feliciano, Enectali; Chervenak, Jay; Finkbeiner, Fred M.; Li, Mary; Lindeman, Mark A.; Stahle, Caroline K.; Stahle, Carl M.

    2002-01-01

    We report the first results from a high-energy-resolution imaging spectrometer called a Position-Sensitive Transition-Edge Sensor (PoST). A PoST is a quantum calorimeter consisting of two Transition Edge Sensors (TESs) on the ends of a long absorber to do one dimensional imaging spectroscopy. Comparing rise time and energy information, the position of the event in the PoST is determined. Energy is inferred from the sum of the two pulses. We have fabricated 7- and 15-pixel PoSTs using Mo-Au TESs and Au absorbers. We have achieved 32 eV FWHM energy resolution at 1.5 keV with a 7-pixel PoST calorimeter

  9. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    Science.gov (United States)

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-07

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging".

  10. Quantum entanglement and teleportation in pulsed cavity optomechanics

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, Sebastian G. [Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Institute for Theoretical Physics, Institute for Gravitational Physics, Leibniz University Hannover, Callinstrasse 38, 30167 Hannover (Germany); Wieczorek, Witlef; Aspelmeyer, Markus [Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Hammerer, Klemens [Institute for Theoretical Physics, Institute for Gravitational Physics, Leibniz University Hannover, Callinstrasse 38, 30167 Hannover (Germany)

    2011-11-15

    Entangling a mechanical oscillator with an optical mode is an enticing and yet a very challenging goal in cavity optomechanics. Here we consider a pulsed scheme to create Einstein-Podolsky-Rosen-type entanglement between a traveling-wave light pulse and a mechanical oscillator. The entanglement can be verified unambiguously by a pump-probe sequence of pulses. In contrast to schemes that work in a steady-state regime under a continuous-wave drive, this protocol is not subject to stability requirements that normally limit the strength of achievable entanglement. We investigate the protocol's performance under realistic conditions, including mechanical decoherence, in full detail. We discuss the relevance of a high mechanical Qf product for entanglement creation and provide a quantitative statement on which magnitude of the Qf product is necessary for a successful realization of the scheme. We determine the optimal parameter regime for its operation and show it to work in current state-of-the-art systems.

  11. Sensitive detection of acrolein and acrylonitrile with a pulsed quantum-cascade laser

    Science.gov (United States)

    Manne, J.; Lim, A.; Tulip, J.; Jäger, W.

    2012-05-01

    We report on spectroscopic measurements of acrolein and acrylonitrile at atmospheric pressure using a pulsed distributed feedback quantum-cascade laser in combination with intra- and inter-pulse techniques and compare the results. The measurements were done in the frequency region around 957 cm-1. In the inter-pulse technique, the laser is excited with short current pulses (5-10 ns), and the pulse amplitude is modulated with an external current ramp resulting in a ˜2.3 cm-1 frequency scan. In the intra-pulse technique, a linear frequency down-chirp during the pulse is used for sweeping across the absorption line. Long current pulses up to 500 ns were used for these measurements which resulted in a spectral window of ˜2.2 cm-1 during the down-chirp. These comparatively wide spectral windows facilitated the measurements of the relatively broad absorption lines (˜1 cm-1) of acrolein and acrylonitrile. The use of a room-temperature mercury-cadmium-telluride detector resulted in a completely cryogen-free spectrometer. We demonstrate ppb level detection limits within a data acquisition time of ˜10 s with these methodologies.

  12. Manifestations of classical physics in the quantum evolution of correlated spin states in pulsed NMR experiments.

    Science.gov (United States)

    Ligare, Martin

    2016-05-01

    Multiple-pulse NMR experiments are a powerful tool for the investigation of molecules with coupled nuclear spins. The product operator formalism provides a way to understand the quantum evolution of an ensemble of weakly coupled spins in such experiments using some of the more intuitive concepts of classical physics and semi-classical vector representations. In this paper I present a new way in which to interpret the quantum evolution of an ensemble of spins. I recast the quantum problem in terms of mixtures of pure states of two spins whose expectation values evolve identically to those of classical moments. Pictorial representations of these classically evolving states provide a way to calculate the time evolution of ensembles of weakly coupled spins without the full machinery of quantum mechanics, offering insight to anyone who understands precession of magnetic moments in magnetic fields.

  13. Detection of acrolein and acrylonitrile with a pulsed room temperature quantum cascade laser

    Science.gov (United States)

    Manne, J.; Jäger, W.; Tulip, J.

    2010-06-01

    We investigated the use of a pulsed, distributed feedback quantum cascade laser centered at 957 cm-1 in combination with an astigmatic Herriot cell with 250 m path length for the detection of acrolein and acrylonitrile. These molecules have been identified as hazardous air-pollutants because of their adverse health effects. The spectrometer utilizes the intra-pulse method, where a linear frequency down-chirp, that is induced when a top-hat current pulse is applied to the laser, is used for sweeping across the absorption line. Up to 450 ns long pulses were used for these measurements which resulted in a spectral window of ~2.2 cm-1. A room temperature mercury-cadmium-telluride detector was used, resulting in a completely cryogen free spectrometer. We demonstrated detection limits of ~3 ppb for acrylonitrile and ~6 ppb for acrolein with ~10 s averaging time. Laser characterization and optimization of the operational parameters for sensitivity improvement are discussed.

  14. SFOL Pulse: A High Accuracy DME Pulse for Alternative Aircraft Position and Navigation

    Directory of Open Access Journals (Sweden)

    Euiho Kim

    2017-09-01

    Full Text Available In the Federal Aviation Administration’s (FAA performance based navigation strategy announced in 2016, the FAA stated that it would retain and expand the Distance Measuring Equipment (DME infrastructure to ensure resilient aircraft navigation capability during the event of a Global Navigation Satellite System (GNSS outage. However, the main drawback of the DME as a GNSS back up system is that it requires a significant expansion of the current DME ground infrastructure due to its poor distance measuring accuracy over 100 m. The paper introduces a method to improve DME distance measuring accuracy by using a new DME pulse shape. The proposed pulse shape was developed by using Genetic Algorithms and is less susceptible to multipath effects so that the ranging error reduces by 36.0–77.3% when compared to the Gaussian and Smoothed Concave Polygon DME pulses, depending on noise environment.

  15. Positive Nonlinear Dynamical Group Uniting Quantum Mechanics and Thermodynamics

    OpenAIRE

    Beretta, Gian Paolo

    2006-01-01

    We discuss and motivate the form of the generator of a nonlinear quantum dynamical group 'designed' so as to accomplish a unification of quantum mechanics (QM) and thermodynamics. We call this nonrelativistic theory Quantum Thermodynamics (QT). Its conceptual foundations differ from those of (von Neumann) quantum statistical mechanics (QSM) and (Jaynes) quantum information theory (QIT), but for thermodynamic equilibrium (TE) states it reduces to the same mathematics, and for zero entropy stat...

  16. Temporal evolution of atmosphere pressure plasma jets driven by microsecond pulses with positive and negative polarities

    Science.gov (United States)

    Shao, Tao; Yang, Wenjin; Zhang, Cheng; Fang, Zhi; Zhou, Yixiao; Schamiloglu, Edl

    2014-09-01

    Current-voltage characteristics, discharge images, and optical spectra of atmospheric pressure plasma jets (APPJs) are studied using a microsecond pulse length generator producing repetitive output pulses with different polarities. The experimental results show that the APPJs excited by the pulses with positive polarity have longer plume, faster propagation speed, higher power, and more excited species, such as \\text{N}2 , O, He, \\text{N}2+ , than that with the negatively excited APPJs. The images taken using an intensified charge-coupled device show that the APPJs excited by pulses with positive polarity are characterized by a bullet-like structure, while the APPJs excited by pulses with negative polarity are continuous. The propagation speed of the APPJs driven by a microsecond pulse length generator is about tens of km/s, which is similar to the APPJs driven by a kHz frequency sinusoidal voltage source. The analysis shows that the space charge accumulation effect plays an important role during the discharge. The transient enhanced electric field induced by the accumulated ions between the needle-like electrode and the nozzle in the APPJs excited by pulses with negative polarity enhances electron field emission from the cathode, which is illustrated by the bright line on the time-integrated images. This makes the shape of the APPJ excited using pulses with negative polarity different from the bullet-like shape of the APPJs excited by pulses with positive polarity.

  17. Simulating quantum search algorithm using vibronic states of I2 manipulated by optimally designed gate pulses

    International Nuclear Information System (INIS)

    Ohtsuki, Yukiyoshi

    2010-01-01

    In this paper, molecular quantum computation is numerically studied with the quantum search algorithm (Grover's algorithm) by means of optimal control simulation. Qubits are implemented in the vibronic states of I 2 , while gate operations are realized by optimally designed laser pulses. The methodological aspects of the simulation are discussed in detail. We show that the algorithm for solving a gate pulse-design problem has the same mathematical form as a state-to-state control problem in the density matrix formalism, which provides monotonically convergent algorithms as an alternative to the Krotov method. The sequential irradiation of separately designed gate pulses leads to the population distribution predicted by Grover's algorithm. The computational accuracy is reduced by the imperfect quality of the pulse design and by the electronic decoherence processes that are modeled by the non-Markovian master equation. However, as long as we focus on the population distribution of the vibronic qubits, we can search a target state with high probability without introducing error-correction processes during the computation. A generalized gate pulse-design scheme to explicitly include decoherence effects is outlined, in which we propose a new objective functional together with its solution algorithm that guarantees monotonic convergence.

  18. The pure phases, the irreducible quantum fields, and dynamical symmetry breaking in Symanzik--Nelson positive quantum field theories

    International Nuclear Information System (INIS)

    Frohlich, J.

    1976-01-01

    We prove that a Symanzik--Nelson positive quantum field theory, i.e., a quantum field theory derived from a Euclidean field theory, has a unique decomposition into pure phases which preserves Symanzik--Nelson positivity and Poincare covariance. We derive useful sufficient conditions for the breakdown of an internal symmetry of such a theory in its pure phases, for the self-adjointness and nontrivially (in the sense of Borchers classes) of its quantum fields, and the existence of time-ordered and retarded products. All these general results are then applied to the P (phi) 2 and the phi 3 4 quantum field models

  19. Pulsed neural networks consisting of single-flux-quantum spiking neurons

    International Nuclear Information System (INIS)

    Hirose, T.; Asai, T.; Amemiya, Y.

    2007-01-01

    An inhibitory pulsed neural network was developed for brain-like information processing, by using single-flux-quantum (SFQ) circuits. It consists of spiking neuron devices that are coupled to each other through all-to-all inhibitory connections. The network selects neural activity. The operation of the neural network was confirmed by computer simulation. SFQ neuron devices can imitate the operation of the inhibition phenomenon of neural networks

  20. Controlled release of stored pulses in a double-quantum-well structure

    International Nuclear Information System (INIS)

    Carreno, F; Anton, M A

    2009-01-01

    We show that an asymmetric double-quantum-well structure can operate as an optical memory. The double quantum wells are modelled like an atomic ensemble of four-level atoms in the Λ-V-type configuration with vacuum-induced coherence arising from resonant tunnelling through the ultra-thin potential energy barrier between the wells. A weak quantum field connects the ground level with the two upper levels and an auxiliary classical control field connects the intermediate level with the upper levels. The quantum field can be mapped into two channels. One channel results from the adiabatic change of the control field which maps the incoming quantum field into the coherence of the two lower levels like in a Λ-type atomic ensemble. The other channel results from the mapping of the quantum field into a combination of coherences between the two upper levels and the ground level, and it is allowed by the adiabatic change of the upper level splitting via an external voltage. The possibility of releasing multiple pulses from the medium resulting from the existence of a non-evolving component of the two-channel memory is shown. A physical picture has been developed providing an explanation of the performance of the device.

  1. Fold maps and positive topological quantum field theories

    Energy Technology Data Exchange (ETDEWEB)

    Wrazidlo, Dominik Johannes

    2017-04-12

    The notion of positive TFT as coined by Banagl is specified by an axiomatic system based on Atiyah's original axioms for TFTs. By virtue of a general framework that is based on the concept of Eilenberg completeness of semirings from computer science, a positive TFT can be produced rigorously via quantization of systems of fields and action functionals - a process inspired by Feynman's path integral from classical quantum field theory. The purpose of the present dissertation thesis is to investigate a new differential topological invariant for smooth manifolds that arises as the state sum of the fold map TFT, which has been constructed by Banagl as a example of a positive TFT. By eliminating an internal technical assumption on the fields of the fold map TFT, we are able to express the informational content of the state sum in terms of an extension problem for fold maps from cobordisms into the plane. Next, we use the general theory of generic smooth maps into the plane to improve known results about the structure of the state sum in arbitrary dimensions, and to determine it completely in dimension two. The aggregate invariant of a homotopy sphere, which is derived from the state sum, naturally leads us to define a filtration of the group of homotopy spheres in order to understand the role of indefinite fold lines beyond a theorem of Saeki. As an application, we show how Kervaire spheres can be characterized by indefinite fold lines in certain dimensions.

  2. Femtosecond pulsed laser ablation in microfluidics for synthesis of photoluminescent ZnSe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chao, E-mail: chaoyangscu@gmail.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Feng, Guoying, E-mail: guoing_feng@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Dai, Shenyu, E-mail: 232127079@qq.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Wang, Shutong, E-mail: wangshutong.scu@gmail.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Li, Guang, E-mail: 632524844@qq.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Zhang, Hua [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Zhou, Shouhuan, E-mail: zhoush@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); North China Research Institute of Electro-Optics, 4 Jiuxianqiao Street, Chaoyang District, Beijing 100015 (China)

    2017-08-31

    Highlights: • A novel method for synthesis and coating of quantum dots by ultrafast laser pulses. • Mild and “green” synthesis method without toxic chemicals. • Enhanced bright green light emission without doped transition metal ions. • Ultrafast laser and coating layer enhanced the emission originated from defects. - Abstract: A simple but new toxic chemical free method, Femtosecond Laser Ablation in Microfluidics (FLAM) was proposed for the first time. ZnSe quantum dots of 4–6 nm were synthesized and with the use of hyperbranched Polyethyleneimine (PEI) as both structural and functional coated layer. These aqueous nanosized micelles consisting of quantum dots exhibit deep defect states emission of bright green light centered at 500 nm. A possible mechanism for the enhanced board band emission was discussed. The properties of toxic matters free and enhanced photoluminescence without doped transition metal ions demonstrate an application potential for biomedical imaging.

  3. Femtosecond pulsed laser ablation in microfluidics for synthesis of photoluminescent ZnSe quantum dots

    International Nuclear Information System (INIS)

    Yang, Chao; Feng, Guoying; Dai, Shenyu; Wang, Shutong; Li, Guang; Zhang, Hua; Zhou, Shouhuan

    2017-01-01

    Highlights: • A novel method for synthesis and coating of quantum dots by ultrafast laser pulses. • Mild and “green” synthesis method without toxic chemicals. • Enhanced bright green light emission without doped transition metal ions. • Ultrafast laser and coating layer enhanced the emission originated from defects. - Abstract: A simple but new toxic chemical free method, Femtosecond Laser Ablation in Microfluidics (FLAM) was proposed for the first time. ZnSe quantum dots of 4–6 nm were synthesized and with the use of hyperbranched Polyethyleneimine (PEI) as both structural and functional coated layer. These aqueous nanosized micelles consisting of quantum dots exhibit deep defect states emission of bright green light centered at 500 nm. A possible mechanism for the enhanced board band emission was discussed. The properties of toxic matters free and enhanced photoluminescence without doped transition metal ions demonstrate an application potential for biomedical imaging.

  4. Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

    Science.gov (United States)

    Priebe, Katharina E.; Rathje, Christopher; Yalunin, Sergey V.; Hohage, Thorsten; Feist, Armin; Schäfer, Sascha; Ropers, Claus

    2017-12-01

    Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—`SQUIRRELS'—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime.

  5. Plasmon-enhanced terahertz emission in self-assembled quantum dots by femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Carreño, F., E-mail: ferpo@fis.ucm.es; Antón, M. A., E-mail: antonm@fis.ucm.es; Melle, Sonia, E-mail: smelle@fis.ucm.es; Calderón, Oscar G., E-mail: oscargc@fis.ucm.es; Cabrera-Granado, E., E-mail: ecabrera@fis.ucm.es [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, C/ Arcos de Jalón 118, 28037 Madrid (Spain); Cox, Joel, E-mail: jcox27@uwo.ca; Singh, Mahi R., E-mail: msingh@uwo.ca [Department of Physics and Astronomy, The University of Western Ontario, London N6A 3K7 (Canada); Egatz-Gómez, A., E-mail: Ana.Egatz-Gomez.1@nd.edu [Department of Chemical and Biomolecular Engineering, University of Notre Dame, South Bend, Indiana 46556 (United States)

    2014-02-14

    A scheme for terahertz (THz) generation from intraband transition in a self-assembled quantum dot (QD) molecule coupled to a metallic nanoparticle (MNP) is analyzed. The QD structure is described as a three-level atom-like system using the density matrix formalism. The MNP with spherical geometry is considered in the quasistatic approximation. A femtosecond laser pulse creates a coherent superposition of two subbands in the quantum dots and produces localized surface plasmons in the nanoparticle which act back upon the QD molecule via dipole-dipole interaction. As a result, coherent THz radiation with a frequency corresponding to the interlevel spacing can be obtained, which is strongly modified by the presence of the MNP. The peak value of the terahertz signal is analyzed as a function of nanoparticle's size, the MNP to QD distance, and the area of the applied laser field. In addition, we theoretically demonstrate that the terahertz pulse generation can be effectively controlled by making use of a train of femtosecond laser pulses. We show that by a proper choice of the parameters characterizing the pulse train a huge enhancement of the terahertz signal is obtained.

  6. Einstein-Podolsky-Rosen paradox and quantum steering in pulsed optomechanics

    Science.gov (United States)

    He, Q. Y.; Reid, M. D.

    2013-11-01

    We describe how to generate an Einstein-Podolsky-Rosen (EPR) paradox between a mesoscopic mechanical oscillator and an optical pulse. We find two types of paradox, defined by whether it is the oscillator or the pulse that shows the effect Schrödinger called “steering”. Only the oscillator paradox addresses the question of mesoscopic local reality for a massive system. In that case, EPR's “elements of reality” are defined for the oscillator, and it is these elements of reality that are falsified (if quantum mechanics is complete). For this sort of paradox, we show that a thermal barrier exists, meaning that a threshold level of pulse-oscillator interaction is required for a given thermal occupation n0 of the oscillator. We find there is no equivalent thermal barrier for the entanglement of the pulse with the oscillator or for the EPR paradox that addresses the local reality of the optical system. Finally, we examine the possibility of an EPR paradox between two entangled oscillators. Our work highlights the asymmetrical effect of thermal noise on quantum nonlocality.

  7. Dropout dynamics in pulsed quantum dot lasers due to mode jumping

    Energy Technology Data Exchange (ETDEWEB)

    Sokolovskii, G. S.; Dudelev, V. V.; Deryagin, A. G.; Novikov, I. I.; Maximov, M. V.; Ustinov, V. M.; Kuchinskii, V. I. [Ioffe Physical-Technical Institute, St. Petersburg (Russian Federation); Viktorov, E. A. [National Research University of Information Technologies, Mechanics and Optics, Saint Petersburg (Russian Federation); Optique Nonlinéaire Théorique, Campus Plaine CP 231, 1050 Bruxelles (Belgium); Applied Physics Research Group (APHY), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels (Belgium); Abusaa, M. [Applied Physics Research Group (APHY), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels (Belgium); Arab American University, Jenin, Palestine (Country Unknown); Danckaert, J. [Applied Physics Research Group (APHY), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels (Belgium); Kolykhalova, E. D. [St. Petersburg State Electrotechnical University “LETI,” St. Petersburg (Russian Federation); Soboleva, K. K. [St. Petersburg State Polytechnical University, St. Petersburg (Russian Federation); Zhukov, A. E. [Academic University, St. Petersburg (Russian Federation); Sibbett, W. [University of St. Andrews, St. Andrews (United Kingdom); Rafailov, E. U. [Aston Institute of Photonic Technologies, Aston University, Birmingham (United Kingdom); Erneux, T. [Optique Nonlinéaire Théorique, Campus Plaine CP 231, 1050 Bruxelles (Belgium)

    2015-06-29

    We examine the response of a pulse pumped quantum dot laser both experimentally and numerically. As the maximum of the pump pulse comes closer to the excited-state threshold, the output pulse shape becomes unstable and leads to dropouts. We conjecture that these instabilities result from an increase of the linewidth enhancement factor α as the pump parameter comes close to the excitated state threshold. In order to analyze the dynamical mechanism of the dropout, we consider two cases for which the laser exhibits either a jump to a different single mode or a jump to fast intensity oscillations. The origin of these two instabilities is clarified by a combined analytical and numerical bifurcation diagram of the steady state intensity modes.

  8. Dropout dynamics in pulsed quantum dot lasers due to mode jumping

    International Nuclear Information System (INIS)

    Sokolovskii, G. S.; Dudelev, V. V.; Deryagin, A. G.; Novikov, I. I.; Maximov, M. V.; Ustinov, V. M.; Kuchinskii, V. I.; Viktorov, E. A.; Abusaa, M.; Danckaert, J.; Kolykhalova, E. D.; Soboleva, K. K.; Zhukov, A. E.; Sibbett, W.; Rafailov, E. U.; Erneux, T.

    2015-01-01

    We examine the response of a pulse pumped quantum dot laser both experimentally and numerically. As the maximum of the pump pulse comes closer to the excited-state threshold, the output pulse shape becomes unstable and leads to dropouts. We conjecture that these instabilities result from an increase of the linewidth enhancement factor α as the pump parameter comes close to the excitated state threshold. In order to analyze the dynamical mechanism of the dropout, we consider two cases for which the laser exhibits either a jump to a different single mode or a jump to fast intensity oscillations. The origin of these two instabilities is clarified by a combined analytical and numerical bifurcation diagram of the steady state intensity modes

  9. Optimal and robust control of quantum state transfer by shaping the spectral phase of ultrafast laser pulses.

    Science.gov (United States)

    Guo, Yu; Dong, Daoyi; Shu, Chuan-Cun

    2018-04-04

    Achieving fast and efficient quantum state transfer is a fundamental task in physics, chemistry and quantum information science. However, the successful implementation of the perfect quantum state transfer also requires robustness under practically inevitable perturbative defects. Here, we demonstrate how an optimal and robust quantum state transfer can be achieved by shaping the spectral phase of an ultrafast laser pulse in the framework of frequency domain quantum optimal control theory. Our numerical simulations of the single dibenzoterrylene molecule as well as in atomic rubidium show that optimal and robust quantum state transfer via spectral phase modulated laser pulses can be achieved by incorporating a filtering function of the frequency into the optimization algorithm, which in turn has potential applications for ultrafast robust control of photochemical reactions.

  10. Theory and Development of Position-Sensitive Quantum Calorimeters. Degree awarded by Stanford Univ.

    Science.gov (United States)

    Figueroa-Feliciano, Enectali; White, Nicholas E. (Technical Monitor)

    2001-01-01

    Quantum calorimeters are being developed as imaging spectrometers for future X-ray astrophysics observatories. Much of the science to be done by these instruments could benefit greatly from larger focal-plane coverage of the detector (without increasing pixel size). An order of magnitude more area will greatly increase the science throughput of these future instruments. One of the main deterrents to achieving this goal is the complexity of the readout schemes involved. We have devised a way to increase the number of pixels from the current baseline designs by an order of magnitude without increasing the number of channels required for readout. The instrument is a high energy resolution, distributed-readout imaging spectrometer called a Position-Sensitive Transition-Edge Sensor (POST). A POST is a quantum calorimeter consisting of two Transition-Edge Sensors (TESS) on the ends of a long absorber capable of one-dimensional imaging spectroscopy. Comparing rise time and energy information from the two TESS, the position of the event in the POST is determined. The energy of the event is inferred from the sum of the two pulses. We have developed a generalized theoretical formalism for distributed-readout calorimeters and apply it to our devices. We derive the noise theory and calculate the theoretical energy resolution of a POST. Our calculations show that a 7-pixel POST with 6 keV saturation energy can achieve 2.3 eV resolution, making this a competitive design for future quantum calorimeter instruments. For this thesis we fabricated 7- and 15-pixel POSTS using Mo/Au TESs and gold absorbers, and moved from concept drawings on scraps of napkins to a 32 eV energy resolution at 1.5 keV, 7-pixel POST calorimeter.

  11. Comparison of WDM/Pulse-Position-Modulation (WDM/PPM) with Code/Pulse-Position-Swapping (C/PPS) Based on Wavelength/Time Codes

    Energy Technology Data Exchange (ETDEWEB)

    Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V

    2009-06-19

    Pulse position modulation (PPM) signaling is favored in intensity modulated/direct detection (IM/DD) systems that have average power limitations. Combining PPM with WDM over a fiber link (WDM/PPM) enables multiple accessing and increases the link's throughput. Electronic bandwidth and synchronization advantages are further gained by mapping the time slots of PPM onto a code space, or code/pulse-position-swapping (C/PPS). The property of multiple bits per symbol typical of PPM can be combined with multiple accessing by using wavelength/time [W/T] codes in C/PPS. This paper compares the performance of WDM/PPM and C/PPS for equal wavelengths and bandwidth.

  12. Initial position estimation method for permanent magnet synchronous motor based on improved pulse voltage injection

    DEFF Research Database (Denmark)

    Wang, Z.; Lu, K.; Ye, Y.

    2011-01-01

    According to saliency of permanent magnet synchronous motor (PMSM), the information of rotor position is implied in performance of stator inductances due to the magnetic saturation effect. Researches focused on the initial rotor position estimation of PMSM by injecting modulated pulse voltage...... vectors. The relationship between the inductance variations and voltage vector positions was studied. The inductance variation effect on estimation accuracy was studied as well. An improved five-pulses injection method was proposed, to improve the estimation accuracy by choosing optimaized voltage vectors...

  13. A pulse stacking method of particle counting applied to position sensitive detection

    International Nuclear Information System (INIS)

    Basilier, E.

    1976-03-01

    A position sensitive particle counting system is described. A cyclic readout imaging device serves as an intermediate information buffer. Pulses are allowed to stack in the imager at very high counting rates. Imager noise is completely discriminated to provide very wide dynamic range. The system has been applied to a detector using cascaded microchannel plates. Pulse height spread produced by the plates causes some loss of information. The loss is comparable to the input loss of the plates. The improvement in maximum counting rate is several hundred times over previous systems that do not permit pulse stacking. (Auth.)

  14. Output pulse-shapes of position-sensitive proportional counters using high resistance single wire

    International Nuclear Information System (INIS)

    Iwatani, Kazuo; Nishiyama, Fumitaka; Hasai, Hiromi

    1980-01-01

    The measurements and model analysis of the output pulse-shapes from a single wire proportional counter (SWPC) which has a high resistance anode are described. The characteristics of the observed pulse-shapes are determined by only one parameter which is a function of anode resistance and load resistance and they are reproduced by a simple model. Using this model, the methods for position read-out are discussed in a systematical way. (author)

  15. Efficient optical trapping of CdTe quantum dots by femtosecond laser pulses

    KAUST Repository

    Chiang, Weiyi

    2014-12-11

    The development in optical trapping and manipulation has been showing rapid progress, most of it is in the small particle sizes in nanometer scales, substituting the conventional continuous-wave lasers with high-repetition-rate ultrashort laser pulse train and nonlinear optical effects. Here, we evaluate two-photon absorption in optical trapping of 2.7 nm-sized CdTe quantum dots (QDs) with high-repetition-rate femtosecond pulse train by probing laser intensity dependence of both Rayleigh scattering image and the two-photon-induced luminescence spectrum of the optically trapped QDs. The Rayleigh scattering imaging indicates that the two-photon absorption (TPA) process enhances trapping ability of the QDs. Similarly, a nonlinear increase of the two-photon-induced luminescence with the incident laser intensity fairly indicates the existence of the TPA process.

  16. Pulse-amplitude modulation of optical injection-locked quantum-dot lasers

    Science.gov (United States)

    Zhou, Yue-Guang; Wang, Cheng

    2018-02-01

    This work theoretically investigates the four-level pulse-amplitude modulation characteristics of quantum dot lasers subject to optical injection. The rate equation model takes into account carrier dynamics in the carrier reservoir, in the excited state, and in the ground state, as well as photon dynamics and phase dynamics of the electric field. It is found that the optical injection significantly improves the eye diagram quality through suppressing the relaxation oscillation, while the extinction ratio is reduced as well. In addition, both the adiabatic chirp and the transient chirp of the signal are substantially suppressed.

  17. The detailed characteristics of positive corona current pulses in the line-to-plane electrodes

    Science.gov (United States)

    Xuebao, LI; Dayong, LI; Qian, ZHANG; Yinfei, LI; Xiang, CUI; Tiebing, LU

    2018-05-01

    The corona current pulses generated by corona discharge are the sources of the radio interference from transmission lines and the detailed characteristics of the corona current pulses from conductor should be investigated in order to reveal their generation mechanism. In this paper, the line-to-plane electrodes are designed to measure and analyze the characteristics of corona current pulses from positive corona discharges. The influences of inter-electrode gap and line diameters on the detail characteristics of corona current pulses, such as pulse amplitude, rise time, duration time and repetition frequency, are carefully analyzed. The obtained results show that the pulse amplitude and the repetition frequency increase with the diameter of line electrode when the electric fields on the surface of line electrodes are same. With the increase of inter-electrode gap, the pulse amplitude and the repetition frequency first decrease and then turn to be stable, while the rise time first increases and finally turns to be stable. The distributions of electric field and space charges under the line electrodes are calculated, and the influences of inter-electrode gap and line electrode diameter on the experimental results are qualitatively explained.

  18. Control quantum evolution speed of a single dephasing qubit for arbitrary initial states via periodic dynamical decoupling pulses.

    Science.gov (United States)

    Song, Ya-Ju; Tan, Qing-Shou; Kuang, Le-Man

    2017-03-08

    We investigate the possibility to control quantum evolution speed of a single dephasing qubit for arbitrary initial states by the use of periodic dynamical decoupling (PDD) pulses. It is indicated that the quantum speed limit time (QSLT) is determined by initial and final quantum coherence of the qubit, as well as the non-Markovianity of the system under consideration during the evolution when the qubit is subjected to a zero-temperature Ohmic-like dephasing reservoir. It is shown that final quantum coherence of the qubit and the non-Markovianity of the system can be modulated by PDD pulses. Our results show that for arbitrary initial states of the dephasing qubit with non-vanishing quantum coherence, PDD pulses can be used to induce potential acceleration of the quantum evolution in the short-time regime, while PDD pulses can lead to potential speedup and slow down in the long-time regime. We demonstrate that the effect of PDD on the QSLT for the Ohmic or sub-Ohmic spectrum (Markovian reservoir) is much different from that for the super-Ohmic spectrum (non-Markovian reservoir).

  19. Mode-Selective Photon Counting Via Quantum Frequency Conversion Using Spectrally-Engineered Pump Pulses

    Science.gov (United States)

    Manurkar, Paritosh

    Most of the existing protocols for quantum communication operate in a two-dimensional Hilbert space where their manipulation and measurement have been routinely investigated. Moving to higher-dimensional Hilbert spaces is desirable because of advantages in terms of longer distance communication capabilities, higher channel capacity and better information security. We can exploit the spatio-temporal degrees of freedom for the quantum optical signals to provide the higher-dimensional signals. But this necessitates the need for measurement and manipulation of multidimensional quantum states. To that end, there have been significant theoretical studies based on quantum frequency conversion (QFC) in recent years even though the experimental progress has been limited. QFC is a process that allows preservation of the quantum information while changing the frequency of the input quantum state. It has deservedly garnered a lot of attention because it serves as the connecting bridge between the communications band (C-band near 1550 nm) where the fiber-optic infrastructure is already established and the visible spectrum where high efficiency single-photon detectors and optical memories have been demonstrated. In this experimental work, we demonstrate mode-selective frequency conversion as a means to measure and manipulate photonic signals occupying d -dimensional Hilbert spaces where d=2 and 4. In the d=2 case, we demonstrate mode contrast between two temporal modes (TMs) which serves as the proof-of-concept demonstration. In the d=4 version, we employ six different TMs for our detailed experimental study. These TMs also include superposition modes which are a crucial component in many quantum key distribution protocols. Our method is based on producing pump pulses which allow us to upconvert the TM of interest while ideally preserving the other modes. We use MATLAB simulations to determine the pump pulse shapes which are subsequently produced by controlling the amplitude and

  20. A0535+26: Refined position measurement and new pulse period data

    International Nuclear Information System (INIS)

    Li, F.; Rappaport, S.; Clark, G.W.; Jernigan, J.G.

    1979-01-01

    The hard, pulsing, transient X-ray source A0535+26 has been observed with SAS 3 on three occasions during 1977--1978. These observations have yielded a precise position measurement (20'' error radius) which renders the identification of A0535+26 with the Be star HDE 245770 virtually certain. The pulse phase was tracked for approx.9 days in 1978 April and clearly showed both first and second derivatives in the pulse period. An analysis of these new timing data, combined with data from previous observations, leads to the following conclusions: (1) a significant fraction of the observed changes in pulse period is probably intrinsic to the compact X-ray stae (e.g., accretion torques on a neutron star), and (2) conservative limits on binary orbital parameters tend to further confirm a long orbital period

  1. Two-photon interference of weak coherent laser pulses recalled from separate solid-state quantum memories

    Science.gov (United States)

    Jin, Jeongwan; Slater, Joshua A.; Saglamyurek, Erhan; Sinclair, Neil; George, Mathew; Ricken, Raimund; Oblak, Daniel; Sohler, Wolfgang; Tittel, Wolfgang

    2013-08-01

    Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.

  2. Two-photon interference of weak coherent laser pulses recalled from separate solid-state quantum memories.

    Science.gov (United States)

    Jin, Jeongwan; Slater, Joshua A; Saglamyurek, Erhan; Sinclair, Neil; George, Mathew; Ricken, Raimund; Oblak, Daniel; Sohler, Wolfgang; Tittel, Wolfgang

    2013-01-01

    Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.

  3. Research on channel characteristics of differential multi pulse position modulation without background noise

    Science.gov (United States)

    Gao, Zhuo; Zhan, Weida; Sun, Quan; Hao, Ziqiang

    2018-04-01

    Differential multi-pulse position modulation (DMPPM) is a new type of modulation technology. There is a fast transmission rate, high bandwidth utilization, high modulation rate characteristics. The study of DMPPM modulation has important scientific value and practical significance. Channel capacity is one of the important indexes to measure the communication capability of communication system, and studying the channel capacity of DMPPM without background noise is the key to analyze the characteristics of DMPPM. The DMPPM theoretical model is established. The symbol structure of DMPPM with guard time slot is analyzed, and the channel capacity expression of DMPPM is deduced. Simulation analysis by MATLAB. The curves of unit channel capacity and capacity efficiency at different pulse and photon counting rates are analyzed. The results show that DMPPM is more advantageous than multi-pulse position modulation (MPPM), and is more suitable for future wireless optical communication system.

  4. A quantum dynamics study of the benzopyran ring opening guided by laser pulses

    Science.gov (United States)

    Saab, Mohamad; Doriol, Loïc Joubert; Lasorne, Benjamin; Guérin, Stéphane; Gatti, Fabien

    2014-10-01

    The ring-opening photoisomerization of benzopyran, which occurs via a photochemical route involving a conical intersection, has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method (MCTDH). We introduce a mechanistic strategy to control the conversion of benzopyran to merocyanine with laser pulses. We use a six-dimensional model developed in a previous work for the potential energy surfaces (PES) based on an extension of the vibronic-coupling Hamiltonian model (diabatization method by ansatz), which depends on the most active degrees of freedom. The main objective of these quantum dynamics simulations is to provide a set of strategies that could help experimentalists to control the photoreactivity vs. photostability ratio (selectivity). In this work we present: (i) a pump-dump technique used to control the photostability, (ii) a two-step strategy to enhance the reactivity of the system: first, a pure vibrational excitation in the electronic ground state that prepares the system and, second, an ultraviolet excitation that brings the system to the first adiabatic electronic state; (iii) finally the effect of a non-resonant pulse (Stark effect) on the dynamics.

  5. Dynamical model of coherent circularly polarized optical pulse interactions with two-level quantum systems

    International Nuclear Information System (INIS)

    Slavcheva, G.; Hess, O.

    2005-01-01

    We propose and develop a method for theoretical description of circularly (elliptically) polarized optical pulse resonant coherent interactions with two-level atoms. The method is based on the time-evolution equations of a two-level quantum system in the presence of a time-dependent dipole perturbation for electric dipole transitions between states with total angular-momentum projection difference (ΔJ z =±1) excited by a circularly polarized electromagnetic field [Feynman et al., J. Appl. Phys. 28, 49 (1957)]. The adopted real-vector representation approach allows for coupling with the vectorial Maxwell's equations for the optical wave propagation and thus the resulting Maxwell pseudospin equations can be numerically solved in the time domain without any approximations. The model permits a more exact study of the ultrafast coherent pulse propagation effects taking into account the vector nature of the electromagnetic field and hence the polarization state of the optical excitation. We demonstrate self-induced transparency effects and formation of polarized solitons. The model represents a qualitative extension of the well-known optical Maxwell-Bloch equations valid for linearly polarized light and a tool for studying coherent quantum control mechanisms

  6. Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers

    International Nuclear Information System (INIS)

    Wójcik, Aleksander K.; Belyanin, Alexey; Malara, Pietro; Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico

    2013-01-01

    We propose a robust and reliable method of active mode locking of mid-infrared quantum cascade lasers and develop its theoretical description. Its key element is the use of an external ring cavity, which circumvents fundamental issues undermining the stability of mode locking in quantum cascade lasers. We show that active mode locking can give rise to the generation of picosecond pulses and phase-locked frequency combs containing thousands of the ring cavity modes

  7. Interband optical pulse injection locking of quantum dot mode-locked semiconductor laser.

    Science.gov (United States)

    Kim, Jimyung; Delfyett, Peter J

    2008-07-21

    We experimentally demonstrate optical clock recovery from quantum dot mode-locked semiconductor lasers by interband optical pulse injection locking. The passively mode-locked slave laser oscillating on the ground state or the first excited state transition is locked through the injection of optical pulses generated via the opposite transition bands, i.e. the first excited state or the ground state transition from the hybridly mode-locked master laser, respectively. When an optical pulse train generated via the first excited state from the master laser is injected to the slave laser oscillating via ground state, the slave laser shows an asymmetric locking bandwidth around the nominal repetition rate of the slave laser. In the reverse injection case of, i.e. the ground state (master laser) to the first excited state (slave laser), the slave laser does not lock even though both lasers oscillate at the same cavity frequency. In this case, the slave laser only locks to higher injection rates as compared to its own nominal repetition rate, and also shows a large locking bandwidth of 6.7 MHz.

  8. Homogeneous spectral broadening of pulsed terahertz quantum cascade lasers by radio frequency modulation.

    Science.gov (United States)

    Wan, W J; Li, H; Cao, J C

    2018-01-22

    The authors present an experimental investigation of radio frequency modulation on pulsed terahertz quantum cascade lasers (QCLs) emitting around 4.3 THz. The QCL chip used in this work is based on a resonant phonon design which is able to generate a 1.2 W peak power at 10 K from a 400-µm-wide and 4-mm-long laser with a single plasmon waveguide. To enhance the radio frequency modulation efficiency and significantly broaden the terahertz spectra, the QCLs are also processed into a double-metal waveguide geometry with a Silicon lens out-coupler to improve the far-field beam quality. The measured beam patterns of the double-metal QCL show a record low divergence of 2.6° in vertical direction and 2.4° in horizontal direction. Finally we perform the inter-mode beat note and terahertz spectra measurements for both single plasmon and double-metal QCLs working in pulsed mode. Since the double-metal waveguide is more suitable for microwave signal transmission, the radio frequency modulation shows stronger effects on the spectral broadening for the double-metal QCL. Although we are not able to achieve comb operation in this work for the pulsed lasers due to the large phase noise, the homogeneous spectral broadening resulted from the radio frequency modulation can be potentially used for spectroscopic applications.

  9. High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

    International Nuclear Information System (INIS)

    Duun, Sune; Haahr, Rasmus G; Hansen, Ole; Birkelund, Karen; Thomsen, Erik V

    2010-01-01

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized for minimizing the optical power needed in reflectance pulse oximetry. To simplify packaging, backside photodiodes are made which are compatible with assembly using surface mounting technology without pre-packaging. Quantum efficiencies up to 95% and area-specific noise equivalent powers down to 30 fW Hz -1/2 cm -1 are achieved. The photodiodes are incorporated into a wireless pulse oximetry sensor system embedded in an adhesive patch presented elsewhere as 'The Electronic Patch'. The annular photodiodes are fabricated using two masked diffusions of first boron and subsequently phosphor. The surface is passivated with a layer of silicon nitride also serving as an optical filter. As the final process, after metallization, a hole in the center of the photodiode is etched using deep reactive ion etch.

  10. Quantum dots for future nanophotonic devices : lateral ordering, position, and number control

    NARCIS (Netherlands)

    Nötzel, R.

    2010-01-01

    After the general aspects of InAs/InP (100) quantum dots (QDs) regarding the formation of QDs versus quantum dashes, wavelength tuning from telecom to mid-infrared region, and device applications, we discuss our recent progress on the lateral ordering, position, and number control of QDs.

  11. Pulse shape analysis and position determination in segmented HPGe detectors: The AGATA detector library

    Energy Technology Data Exchange (ETDEWEB)

    Bruyneel, B. [Universitaet zu Koeln, Institut fuer Kernphysik, Koeln (Germany); Service de Physique Nucleaire, CEA Saclay, Gif-sur-Yvette (France); Birkenbach, B.; Reiter, P. [Universitaet zu Koeln, Institut fuer Kernphysik, Koeln (Germany)

    2016-03-15

    The AGATA Detector Library (ADL) was developed for the calculation of signals from highly segmented large volume high-purity germanium (HPGe) detectors. ADL basis sets comprise a huge amount of calculated position-dependent detector pulse shapes. A basis set is needed for Pulse Shape Analysis (PSA). By means of PSA the interaction position of a γ -ray inside the active detector volume is determined. Theoretical concepts of the calculations are introduced and cover the relevant aspects of signal formation in HPGe. The approximations and the realization of the computer code with its input parameters are explained in detail. ADL is a versatile and modular computer code; new detectors can be implemented in this library. Measured position resolutions of the AGATA detectors based on ADL are discussed. (orig.)

  12. Effect of quantum well position on the distortion characteristics of transistor laser

    Science.gov (United States)

    Piramasubramanian, S.; Ganesh Madhan, M.; Radha, V.; Shajithaparveen, S. M. S.; Nivetha, G.

    2018-05-01

    The effect of quantum well position on the modulation and distortion characteristics of a 1300 nm transistor laser is analyzed in this paper. Standard three level rate equations are numerically solved to study this characteristics. Modulation depth, second order harmonic and third order intermodulation distortion of the transistor laser are evaluated for different quantum well positions for a 900 MHz RF signal modulation. From the DC analysis, it is observed that optical power is maximum, when the quantum well is positioned near base-emitter interface. The threshold current of the device is found to increase with increasing the distance between the quantum well and the base-emitter junction. A maximum modulation depth of 0.81 is predicted, when the quantum well is placed at 10 nm from the base-emitter junction, under RF modulation. The magnitude of harmonic and intermodulation distortion are found to decrease with increasing current and with an increase in quantum well distance from the emitter base junction. A minimum second harmonic distortion magnitude of -25.96 dBc is predicted for quantum well position (230 nm) near to the base-collector interface for 900 MHz modulation frequency at a bias current of 20 Ibth. Similarly, a minimum third order intermodulation distortion of -38.2 dBc is obtained for the same position and similar biasing conditions.

  13. Lead-position dependent regular oscillations and random fluctuations of conductance in graphene quantum dots

    International Nuclear Information System (INIS)

    Huang Liang; Yang Rui; Lai Yingcheng; Ferry, David K

    2013-01-01

    Quantum interference causes a wavefunction to have sensitive spatial dependence, and this has a significant effect on quantum transport. For example, in a quantum-dot system, the conductance can depend on the lead positions. We investigate, for graphene quantum dots, the conductance variations with the lead positions. Since for graphene the types of boundaries, e.g., zigzag and armchair, can fundamentally affect the quantum transport characteristics, we focus on rectangular graphene quantum dots, for which the effects of boundaries can be systematically studied. For both zigzag and armchair horizontal boundaries, we find that changing the positions of the leads can induce significant conductance variations. Depending on the Fermi energy, the variations can be either regular oscillations or random conductance fluctuations. We develop a physical theory to elucidate the origin of the conductance oscillation/fluctuation patterns. In particular, quantum interference leads to standing-wave-like-patterns in the quantum dot which, in the absence of leads, are regulated by the energy-band structure of the corresponding vertical graphene ribbon. The observed ‘coexistence’ of regular oscillations and random fluctuations in the conductance can be exploited for the development of graphene-based nanodevices. (paper)

  14. Quantum dots for future nanophotonic devices : lateral ordering, position, and number control

    NARCIS (Netherlands)

    Nötzel, R.; Sritirawisarn, N.; Selçuk, E.; Wang, H.; Yuan, J.

    2009-01-01

    We review our recent advances in the lateral ordering, position, and number control of self-organized epitaxial semiconductor quantum dots based on self-organized anisotropic strain engineering, growth on patterned substrates, and selective area growth.

  15. Insecurity of position-based quantum-cryptography protocols against entanglement attacks

    International Nuclear Information System (INIS)

    Lau, Hoi-Kwan; Lo, Hoi-Kwong

    2011-01-01

    Recently, position-based quantum cryptography has been claimed to be unconditionally secure. On the contrary, here we show that the existing proposals for position-based quantum cryptography are, in fact, insecure if entanglement is shared among two adversaries. Specifically, we demonstrate how the adversaries can incorporate ideas of quantum teleportation and quantum secret sharing to compromise the security with certainty. The common flaw to all current protocols is that the Pauli operators always map a codeword to a codeword (up to an irrelevant overall phase). We propose a modified scheme lacking this property in which the same cheating strategy used to undermine the previous protocols can succeed with a rate of at most 85%. We prove the modified protocol is secure when the shared quantum resource between the adversaries is a two- or three-level system.

  16. Some quantum Lie algebras of type D{sub n} positive

    Energy Technology Data Exchange (ETDEWEB)

    Bautista, Cesar [Facultad de Ciencias de la Computacion, Benemerita Universidad Autonoma de Puebla, Edif 135, 14 sur y Av San Claudio, Ciudad Universitaria, Puebla Pue. CP 72570 (Mexico); Juarez-Ramirez, Maria Araceli [Facultad de Ciencias Fisico-Matematicas, Benemerita Universidad Autonoma de Puebla, Edif 158 Av San Claudio y Rio Verde sn Ciudad Universitaria, Puebla Pue. CP 72570 (Mexico)

    2003-03-07

    A quantum Lie algebra is constructed within the positive part of the Drinfeld-Jimbo quantum group of type D{sub n}. Our quantum Lie algebra structure includes a generalized antisymmetry property and a generalized Jacobi identity closely related to the braid equation. A generalized universal enveloping algebra of our quantum Lie algebra of type D{sub n} positive is proved to be the Drinfeld-Jimbo quantum group of the same type. The existence of such a generalized Lie algebra is reduced to an integer programming problem. Moreover, when the integer programming problem is feasible we show, by means of the generalized Jacobi identity, that the Poincare-Birkhoff-Witt theorem (basis) is still true.

  17. Smeared quantum lattices exhibiting PT -symmetry with positive P

    Czech Academy of Sciences Publication Activity Database

    Znojil, Miloslav; Geyer, H.B.

    2013-01-01

    Roč. 61, 2-3 (2013), s. 111-123 ISSN 0015-8208 R&D Projects: GA ČR GAP203/11/1433 Institutional support: RVO:61389005 Keywords : cryptohermiticity * quantum lattices * unphysical and physical inner products Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 1.233, year: 2013

  18. Position-momentum uncertainty relations in the presence of quantum memory

    DEFF Research Database (Denmark)

    Furrer, Fabian; Berta, Mario; Tomamichel, Marco

    2014-01-01

    A prominent formulation of the uncertainty principle identifies the fundamental quantum feature that no particle may be prepared with certain outcomes for both position and momentum measurements. Often the statistical uncertainties are thereby measured in terms of entropies providing a clear oper....... As an illustration, we evaluate the uncertainty relations for position and momentum measurements, which is operationally significant in that it implies security of a quantum key distribution scheme based on homodyne detection of squeezed Gaussian states....

  19. Time-resolved study of a pulsed dc discharge using quantum cascade laser absorption spectroscopy : NO and gas temperature kinetics

    NARCIS (Netherlands)

    Welzel, S.; Gatilova, L.; Röpcke, J.; Rousseau, A.

    2007-01-01

    In a pulsed dc discharge of an Ar–N2 mixture containing 0.91% of NO the kinetics of the destruction of NO has been studied under static and flowing conditions, i.e. in a closed and open discharge tube (p = 266 Pa). For this purpose quantum cascade laser absorption spectroscopy (QCLAS) in the

  20. NO kinetics in pulsed low-pressure nitrogen plasmas studied by time resolved quantum cascade laser absorption spectroscopy

    NARCIS (Netherlands)

    Welzel, S.; Guaitella, O.; Lazzaroni, C.; Pintassilgo, C.; Rousseau, A.; Röpcke, J.

    2011-01-01

    Time-resolved quantum cascade laser absorption spectroscopy at 1897 cm-1 (5.27 µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the

  1. Gradient ascent pulse engineering approach to CNOT gates in donor electron spin quantum computing

    International Nuclear Information System (INIS)

    Tsai, D.-B.; Goan, H.-S.

    2008-01-01

    In this paper, we demonstrate how gradient ascent pulse engineering (GRAPE) optimal control methods can be implemented on donor electron spin qubits in semiconductors with an architecture complementary to the original Kane's proposal. We focus on the high fidelity controlled-NOT (CNOT) gate and we explicitly find the digitized control sequences for a controlled-NOT gate by optimizing its fidelity using the effective, reduced donor electron spin Hamiltonian with external controls over the hyperfine A and exchange J interactions. We then simulate the CNOT-gate sequence with the full spin Hamiltonian and find that it has an error of 10 -6 that is below the error threshold of 10 -4 required for fault-tolerant quantum computation. Also the CNOT gate operation time of 100 ns is 3 times faster than 297 ns of the proposed global control scheme.

  2. Investigation of the pulse shape analysis for the position sensitive γ-ray spectrometer AGATA

    Energy Technology Data Exchange (ETDEWEB)

    Lewandowski, Lars; Birkenbach, Benedikt; Reiter, Peter [Institut fuer Kernphysik Koeln (Germany); Collaboration: AGATA-Collaboration

    2015-07-01

    The next generation of γ-ray spectrometers like AGATA will provide high quality γ-ray spectra by the new Gamma-Ray Tracking technique (GRT). Position sensitive HPGe detectors will allow for precise Doppler correction and small broadening of lines for spectroscopy at relativistic energies. GRT is based on the interaction position of the γ-rays within the volume of the highly segmented germanium detectors provided by Pulse Shape Analysis (PSA) methods. The proof of principle of GRT was already demonstrated with great success however systematic deviations from expected results occur. The parameterization of the following detector properties and their impact on PSA were thoroughly investigated and optimized: electron and hole mobility, crystal axis orientation, space charge distributions, crystal impurities, response functions of preamplifiers and digitizers, linear and differential crosstalk, time alignment of pulses and the distance metric. Results of an improved PSA performance are presented.

  3. Analysis of the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery☆

    Science.gov (United States)

    Arba-Mosquera, Samuel; Aslanides, Ioannis M.

    2012-01-01

    Purpose To analyze the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery. Methods A comprehensive model, which directly considers eye movements, including saccades, vestibular, optokinetic, vergence, and miniature, as well as, eye-tracker acquisition rate, eye-tracker latency time, scanner positioning time, laser firing rate, and laser trigger delay have been developed. Results Eye-tracker acquisition rates below 100 Hz correspond to pulse positioning errors above 1.5 mm. Eye-tracker latency times to about 15 ms correspond to pulse positioning errors of up to 3.5 mm. Scanner positioning times to about 9 ms correspond to pulse positioning errors of up to 2 mm. Laser firing rates faster than eye-tracker acquisition rates basically duplicate pulse-positioning errors. Laser trigger delays to about 300 μs have minor to no impact on pulse-positioning errors. Conclusions The proposed model can be used for comparison of laser systems used for ablation processes. Due to the pseudo-random nature of eye movements, positioning errors of single pulses are much larger than observed decentrations in the clinical settings. There is no single parameter that ‘alone’ minimizes the positioning error. It is the optimal combination of the several parameters that minimizes the error. The results of this analysis are important to understand the limitations of correcting very irregular ablation patterns.

  4. Graphene quantum dot synthesis using nanosecond laser pulses and its comparison to Methylene Blue

    Science.gov (United States)

    Kholikov, Khomidkhodza; Thomas, Zachary; Seyitliyev, Dovletgeldi; Smith, Skylar

    A biocompatible photodynamic therapy agent that generates a high amount of singlet oxygen with high water dispersibility and excellent photostability is desirable. In this work, a graphene based biomaterial which is a promising alternative to a standard photosensitizers was produced. Methylene blue was used as a reference photosensitizer. Bacteria deactivation by methylene blue was shown to be inhibited inside human blood due to protein binding. Graphene quantum dots (GQD) were synthesized by irradiating benzene and nickel oxide mixture using nanosecond laser pulses. High resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) were used for characterization of GQDs. Initial results show graphene quantum dots whose size less than 5 nm were successfully obtained. UV-VIS spectra shows absorption peak around 310 nm. The results of these studies can potentially be used to develop therapies for the eradication of pathogens in open wounds, burns, or skin cancers. New therapies for these conditions are particularly needed when antibiotic-resistant infections are present. NIH KBRIN.

  5. Magnetosphere and ionosphere response to a positive-negative pulse pair of solar wind dynamic pressure

    Science.gov (United States)

    Tian, A.; Degeling, A. W.

    2017-12-01

    Simulations and observations had shown that single positive/negative solar wind dynamic pressure pulse would excite geomagnetic impulsive events along with ionosphere and/or magnetosphere vortices which are connected by field aligned currents(FACs). In this work, a large scale ( 9min) magnetic hole event in solar wind provided us with the opportunity to study the effects of positive-negative pulse pair (△p/p 1) on the magnetosphere and ionosphere. During the magnetic hole event, two traveling convection vortices (TCVs, anti-sunward) first in anticlockwise then in clockwise rotation were detected by geomagnetic stations located along the 10:30MLT meridian. At the same time, another pair of ionospheric vortices azimuthally seen up to 3 MLT first in clockwise then in counter-clockwise rotation were also appeared in the afternoon sector( 14MLT) and centered at 75 MLAT without obvious tailward propagation feature. The duskside vortices were also confirmed in SuperDARN radar data. We simulated the process of magnetosphere struck by a positive-negative pulse pair and it shows that a pair of reversed flow vortices in the magnetosphere equatorial plane appeared which may provide FACs for the vortices observed in ionosphere. Dawn dusk asymmetry of the vortices as well as the global geomagnetism perturbation characteristics were also discussed.

  6. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Yung Szen, E-mail: yungszen@utm.my [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka-shi, Osaka 560-8531 (Japan); Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Tabuchi, Yutaka [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku, Tokyo 153-8904 (Japan); Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro, E-mail: kitagawa@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka-shi, Osaka 560-8531 (Japan)

    2015-06-15

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.

  7. New hybrid reverse differential pulse position width modulation scheme for wireless optical communication

    Science.gov (United States)

    Liao, Renbo; Liu, Hongzhan; Qiao, Yaojun

    2014-05-01

    In order to improve the power efficiency and reduce the packet error rate of reverse differential pulse position modulation (RDPPM) for wireless optical communication (WOC), a hybrid reverse differential pulse position width modulation (RDPPWM) scheme is proposed, based on RDPPM and reverse pulse width modulation. Subsequently, the symbol structure of RDPPWM is briefly analyzed, and its performance is compared with that of other modulation schemes in terms of average transmitted power, bandwidth requirement, and packet error rate over ideal additive white Gaussian noise (AWGN) channels. Based on the given model, the simulation results show that the proposed modulation scheme has the advantages of improving the power efficiency and reducing the bandwidth requirement. Moreover, in terms of error probability performance, RDPPWM can achieve a much lower packet error rate than that of RDPPM. For example, at the same received signal power of -28 dBm, the packet error rate of RDPPWM can decrease to 2.6×10-12, while that of RDPPM is 2.2×10. Furthermore, RDPPWM does not need symbol synchronization at the receiving end. These considerations make RDPPWM a favorable candidate to select as the modulation scheme in the WOC systems.

  8. Status and trends of short pulse generation using mode-locked lasers based on advanced quantum-dot active media

    International Nuclear Information System (INIS)

    Shi, L W; Chen, Y H; Xu, B; Wang, Z C; Jiao, Y H; Wang, Z G

    2007-01-01

    In this review, the potential of mode-locked lasers based on advanced quantum-dot (QD) active media to generate short optical pulses is analysed. A comprehensive review of experimental and theoretical work on related aspects is provided, including monolithic-cavity mode-locked QD lasers and external-cavity mode-locked QD lasers, as well as mode-locked solid-state and fibre lasers based on QD semiconductor saturable absorber mirrors. Performance comparisons are made for state-of-the-art experiments. Various methods for improving important characteristics of mode-locked pulses such as pulse duration, repetition rate, pulse power, and timing jitter through optimization of device design parameters or mode-locking methods are addressed. In addition, gain switching and self-pulsation of QD lasers are also briefly reviewed, concluding with the summary and prospects. (topical review)

  9. Quantum learning of classical stochastic processes: The completely positive realization problem

    Science.gov (United States)

    Monràs, Alex; Winter, Andreas

    2016-01-01

    Among several tasks in Machine Learning, a specially important one is the problem of inferring the latent variables of a system and their causal relations with the observed behavior. A paradigmatic instance of this is the task of inferring the hidden Markov model underlying a given stochastic process. This is known as the positive realization problem (PRP), [L. Benvenuti and L. Farina, IEEE Trans. Autom. Control 49(5), 651-664 (2004)] and constitutes a central problem in machine learning. The PRP and its solutions have far-reaching consequences in many areas of systems and control theory, and is nowadays an important piece in the broad field of positive systems theory. We consider the scenario where the latent variables are quantum (i.e., quantum states of a finite-dimensional system) and the system dynamics is constrained only by physical transformations on the quantum system. The observable dynamics is then described by a quantum instrument, and the task is to determine which quantum instrument — if any — yields the process at hand by iterative application. We take as a starting point the theory of quasi-realizations, whence a description of the dynamics of the process is given in terms of linear maps on state vectors and probabilities are given by linear functionals on the state vectors. This description, despite its remarkable resemblance with the hidden Markov model, or the iterated quantum instrument, is however devoid of any stochastic or quantum mechanical interpretation, as said maps fail to satisfy any positivity conditions. The completely positive realization problem then consists in determining whether an equivalent quantum mechanical description of the same process exists. We generalize some key results of stochastic realization theory, and show that the problem has deep connections with operator systems theory, giving possible insight to the lifting problem in quotient operator systems. Our results have potential applications in quantum machine

  10. Quantum learning of classical stochastic processes: The completely positive realization problem

    Energy Technology Data Exchange (ETDEWEB)

    Monràs, Alex [Física Teòrica: Informació i Fenòmens Quàntics, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain); Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Winter, Andreas [Física Teòrica: Informació i Fenòmens Quàntics, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain); Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); ICREA—Institució Catalana de Recerca i Estudis Avançats, Pg. Lluis Companys, 23, 08010 Barcelona (Spain)

    2016-01-15

    Among several tasks in Machine Learning, a specially important one is the problem of inferring the latent variables of a system and their causal relations with the observed behavior. A paradigmatic instance of this is the task of inferring the hidden Markov model underlying a given stochastic process. This is known as the positive realization problem (PRP), [L. Benvenuti and L. Farina, IEEE Trans. Autom. Control 49(5), 651–664 (2004)] and constitutes a central problem in machine learning. The PRP and its solutions have far-reaching consequences in many areas of systems and control theory, and is nowadays an important piece in the broad field of positive systems theory. We consider the scenario where the latent variables are quantum (i.e., quantum states of a finite-dimensional system) and the system dynamics is constrained only by physical transformations on the quantum system. The observable dynamics is then described by a quantum instrument, and the task is to determine which quantum instrument — if any — yields the process at hand by iterative application. We take as a starting point the theory of quasi-realizations, whence a description of the dynamics of the process is given in terms of linear maps on state vectors and probabilities are given by linear functionals on the state vectors. This description, despite its remarkable resemblance with the hidden Markov model, or the iterated quantum instrument, is however devoid of any stochastic or quantum mechanical interpretation, as said maps fail to satisfy any positivity conditions. The completely positive realization problem then consists in determining whether an equivalent quantum mechanical description of the same process exists. We generalize some key results of stochastic realization theory, and show that the problem has deep connections with operator systems theory, giving possible insight to the lifting problem in quotient operator systems. Our results have potential applications in quantum machine

  11. Quantum learning of classical stochastic processes: The completely positive realization problem

    International Nuclear Information System (INIS)

    Monràs, Alex; Winter, Andreas

    2016-01-01

    Among several tasks in Machine Learning, a specially important one is the problem of inferring the latent variables of a system and their causal relations with the observed behavior. A paradigmatic instance of this is the task of inferring the hidden Markov model underlying a given stochastic process. This is known as the positive realization problem (PRP), [L. Benvenuti and L. Farina, IEEE Trans. Autom. Control 49(5), 651–664 (2004)] and constitutes a central problem in machine learning. The PRP and its solutions have far-reaching consequences in many areas of systems and control theory, and is nowadays an important piece in the broad field of positive systems theory. We consider the scenario where the latent variables are quantum (i.e., quantum states of a finite-dimensional system) and the system dynamics is constrained only by physical transformations on the quantum system. The observable dynamics is then described by a quantum instrument, and the task is to determine which quantum instrument — if any — yields the process at hand by iterative application. We take as a starting point the theory of quasi-realizations, whence a description of the dynamics of the process is given in terms of linear maps on state vectors and probabilities are given by linear functionals on the state vectors. This description, despite its remarkable resemblance with the hidden Markov model, or the iterated quantum instrument, is however devoid of any stochastic or quantum mechanical interpretation, as said maps fail to satisfy any positivity conditions. The completely positive realization problem then consists in determining whether an equivalent quantum mechanical description of the same process exists. We generalize some key results of stochastic realization theory, and show that the problem has deep connections with operator systems theory, giving possible insight to the lifting problem in quotient operator systems. Our results have potential applications in quantum machine

  12. Pulsed Electrical Spin Injection into InGaAs Quantum Dots: Studies of the Electroluminescence Polarization Dynamics

    International Nuclear Information System (INIS)

    Asshoff, P.; Loeffler, W.; Fluegge, H.; Zimmer, J.; Mueller, J.; Westenfelder, B.; Hu, D. Z.; Schaadt, D. M.; Kalt, H.; Hetterich, M.

    2010-01-01

    We present time-resolved studies of the spin polarization dynamics during and after initialization through pulsed electrical spin injection into InGaAs quantum dots embedded in a p-i-n-type spin-injection light-emitting diode. Experiments are performed with pulse widths in the nanosecond range and a time-resolved single photon counting setup is used to detect the subsequent electroluminescence. We find evidence that the achieved spin polarization shows an unexpected temporal behavior, attributed mainly to many-carrier and non-equilibrium effects in the device.

  13. Formation of plasmon pulses in the cooperative decay of excitons of quantum dots near a metal surface

    Energy Technology Data Exchange (ETDEWEB)

    Shesterikov, A. B.; Gubin, M. Yu. [Vladimir State University (Russian Federation); Gladush, M. G. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation); Prokhorov, A. V., E-mail: avprokhorov33@mail.ru [Vladimir State University (Russian Federation)

    2017-01-15

    The formation of pulses of surface electromagnetic waves at a metal–dielectric boundary is considered in the process of cooperative decay of excitons of quantum dots distributed near a metal surface in a dielectric layer. It is shown that the efficiency of exciton energy transfer to excited plasmons can, in principle, be increased by selecting the dielectric material with specified values of the complex permittivity. It is found that in the mean field approximation, the semiclassical model of formation of plasmon pulses in the system under study is reduced to the pendulum equation with the additional term of nonlinear losses.

  14. The Influences of Quantum Coherence on the Positive Work and the Efficiency of Quantum Heat Engine with Working Substance of Two-Qubit Heisenberg XXX Model

    Science.gov (United States)

    Peng, Hu-Ping; Fang, Mao-Fa; Yu, Min; Zou, Hong-Mei

    2018-03-01

    We study the influences of quantum coherence on the positive work and the efficiency of quantum heat engine (QHE) based on working substance of two-qubit Heisenberg model under a constant external magnetic field. By using analytical and numerical solution, we give the relation expressions for both the positive work and the efficiency with quantum coherence, and in detail discuss the effects of the quantum coherence on the positive work and the efficiency of QHE in the absence or presence of external magnetic field, respectively.

  15. The Influences of Quantum Coherence on the Positive Work and the Efficiency of Quantum Heat Engine with Working Substance of Two-Qubit Heisenberg XXX Model

    Science.gov (United States)

    Peng, Hu-Ping; Fang, Mao-Fa; Yu, Min; Zou, Hong-Mei

    2018-06-01

    We study the influences of quantum coherence on the positive work and the efficiency of quantum heat engine (QHE) based on working substance of two-qubit Heisenberg model under a constant external magnetic field. By using analytical and numerical solution, we give the relation expressions for both the positive work and the efficiency with quantum coherence, and in detail discuss the effects of the quantum coherence on the positive work and the efficiency of QHE in the absence or presence of external magnetic field, respectively.

  16. Intercept-resend attacks in the Bennett-Brassard 1984 quantum-key-distribution protocol with weak coherent pulses

    International Nuclear Information System (INIS)

    Curty, Marcos; Luetkenhaus, Norbert

    2005-01-01

    Unconditional security proofs of the Bennett-Brassard 1984 protocol of quantum key distribution have been obtained recently. These proofs cover also practical implementations that utilize weak coherent pulses in the four signal polarizations. Proven secure rates leave open the possibility that new proofs or new public discussion protocols will obtain larger rates over increased distance. In this paper we investigate limits to the error rate and signal losses that can be tolerated by future protocols and proofs

  17. Finite-key analysis for quantum key distribution with weak coherent pulses based on Bernoulli sampling

    Science.gov (United States)

    Kawakami, Shun; Sasaki, Toshihiko; Koashi, Masato

    2017-07-01

    An essential step in quantum key distribution is the estimation of parameters related to the leaked amount of information, which is usually done by sampling of the communication data. When the data size is finite, the final key rate depends on how the estimation process handles statistical fluctuations. Many of the present security analyses are based on the method with simple random sampling, where hypergeometric distribution or its known bounds are used for the estimation. Here we propose a concise method based on Bernoulli sampling, which is related to binomial distribution. Our method is suitable for the Bennett-Brassard 1984 (BB84) protocol with weak coherent pulses [C. H. Bennett and G. Brassard, Proceedings of the IEEE Conference on Computers, Systems and Signal Processing (IEEE, New York, 1984), Vol. 175], reducing the number of estimated parameters to achieve a higher key generation rate compared to the method with simple random sampling. We also apply the method to prove the security of the differential-quadrature-phase-shift (DQPS) protocol in the finite-key regime. The result indicates that the advantage of the DQPS protocol over the phase-encoding BB84 protocol in terms of the key rate, which was previously confirmed in the asymptotic regime, persists in the finite-key regime.

  18. Quantum key distribution with an efficient countermeasure against correlated intensity fluctuations in optical pulses

    Science.gov (United States)

    Yoshino, Ken-ichiro; Fujiwara, Mikio; Nakata, Kensuke; Sumiya, Tatsuya; Sasaki, Toshihiko; Takeoka, Masahiro; Sasaki, Masahide; Tajima, Akio; Koashi, Masato; Tomita, Akihisa

    2018-03-01

    Quantum key distribution (QKD) allows two distant parties to share secret keys with the proven security even in the presence of an eavesdropper with unbounded computational power. Recently, GHz-clock decoy QKD systems have been realized by employing ultrafast optical communication devices. However, security loopholes of high-speed systems have not been fully explored yet. Here we point out a security loophole at the transmitter of the GHz-clock QKD, which is a common problem in high-speed QKD systems using practical band-width limited devices. We experimentally observe the inter-pulse intensity correlation and modulation pattern-dependent intensity deviation in a practical high-speed QKD system. Such correlation violates the assumption of most security theories. We also provide its countermeasure which does not require significant changes of hardware and can generate keys secure over 100 km fiber transmission. Our countermeasure is simple, effective and applicable to wide range of high-speed QKD systems, and thus paves the way to realize ultrafast and security-certified commercial QKD systems.

  19. Probing background ionization: positive streamers with varying pulse repetition rate and with a radioactive admixture

    International Nuclear Information System (INIS)

    Nijdam, S; Van Veldhuizen, E M; Ebert, U; Wormeester, G

    2011-01-01

    Positive streamers need a source of free electrons ahead of them to propagate. A streamer can supply these electrons by itself through photo-ionization, or the electrons can be present due to external background ionization. Here we investigate the effects of background ionization on streamer propagation and morphology by changing the gas composition and the repetition rate of the voltage pulses, and by adding a small amount of radioactive 85 Kr. We find that the general morphology of a positive streamer discharge in high-purity nitrogen depends on background ionization: at lower background ionization levels the streamers branch more and have a more feather-like appearance. This is observed both when varying the repetition rate and when adding 85 Kr, though side branches are longer with the radioactive admixture. But velocities and minimal diameters of streamers are virtually independent of the background ionization level. In air, the inception cloud breaks up into streamers at a smaller radius when the repetition rate and therefore the background ionization level is higher. When measuring the effects of the pulse repetition rate and of the radioactive admixture on the discharge morphology, we found that our estimates of background ionization levels are consistent with these observations; this gives confidence in the estimates. Streamer channels generally do not follow the paths of previous discharge channels for repetition rates of up to 10 Hz. We estimate the effect of recombination and diffusion of ions and free electrons from the previous discharge and conclude that the old trail has largely disappeared at the moment of the next voltage pulse; therefore the next streamers indeed cannot follow the old trail.

  20. Simulation and measurement of short infrared pulses on silicon position sensitive device

    International Nuclear Information System (INIS)

    Krapohl, D; Esebamen, O X; Nilsson, H E; Thungstroem, G

    2011-01-01

    Lateral position sensitive devices (PSD) are important for triangulation, alignment and surface measurements as well as for angle measurements. Large PSDs show a delay on rising and falling edges when irradiated with near infra-red light. This delay is also dependent on the spot position relative to the electrodes. It is however desirable in most applications to have a fast response. We investigated the responsiveness of a Sitek PSD in a mixed mode simulation of a two dimensional full sized detector. For simulation and measurement purposes focused light pulses with a wavelength of 850 nm, duration of 1μs and spot size of 280μm were used. The cause for the slopes of rise and fall time is due to time constants of the device capacitance as well as the photo-generation mechanism itself. To support the simulated results, we conducted measurements of rise and fall times on a physical device. Additionally, we quantified the homogeneity of the device by repositioning a spot of light from a pulsed ir-laser diode on the surface area.

  1. Dynamic Characteristics of Positive Pulsed Dielectric Barrier Discharge for Ozone Generation in Air

    International Nuclear Information System (INIS)

    Wei Linsheng; Peng Bangfa; Li Ming; Zhang Yafang; Hu Zhaoji

    2016-01-01

    A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge (DBD) using parallel-plate reactor in air. The electron energy conservation equation is coupled to the electron continuity equation, the heavy species continuity equation, and Poisson's equation for a better description. The reliability of the model is experimentally confirmed. The model can be used to predict the temporal and spatial evolution of species, as well as streamer propagation. The simulation results show that electron density increases nearly exponentially in the direction to the anode at the electron avalanche. Streamer propagation velocity is about 5.26 × 10 4 m/s from anode to cathode in the simulated condition. The primary positive ion, negative ion, and excited species are O 2 + , O 3 − and O 2 ( 1 Δg) in pulsed DBD in air, respectively. N 2 O has the largest density among nitrogen oxides. e and N 2 + densities in the streamer head increase gradually to maximum values with the development of the streamer. Meanwhile, the O 2 + , O, O 3 , N 2 (A 3 Σ) and N 2 O densities reach maximum values in the vicinity of the anode. (paper)

  2. Ultra-short pulse, ultra-high intensity laser improvement techniques for laser-driven quantum beam science

    International Nuclear Information System (INIS)

    Kiriyama, Hiromitsu; Kando, Masaki

    2014-01-01

    Recent development activities of the Quantum Beam Research Team in JAEA are reported. The downsized, petawatt and femtosecond pulse laser is described at first. The process of the system development and utilization effort of so-called J-KAREN is explained with its time and space control system. For high contrast, OPCPA (Optical Parametric Chirped Pulse Amplification) preamplifier is adopted by using the titanium-sapphire laser system in which only the seed light pulses can be amplified. In addition, high contrast is obtained by adopting the high energy seed light to the amplifier. The system configuration of J-KAREN laser is illustrated. Typical spectra with and without OPCPA, as well as the spectra with OPCPA adjustment and without one are shown. The result of the recompressed pulses is shown in which the pulse width of 29.5 femtoseconds is close to the theoretical limit. Considering the throughput of the pulse compressor is 64 percent it is possible to generate high power laser beam of about 600 terawatts. In the supplementary budget of 2012, it has been approved to cope with the aging or obsoleteness of the system and at the same time to further sophisticate the laser using system. The upgraded laser system is named as J-KAREN-P in which the repetition rate is improved and another booster amplifier is added to increase the power. The system configuration of J-KAREN-P after the upgrading is illustrated. (S. Funahashi)

  3. Mechanical strain can switch the sign of quantum capacitance from positive to negative.

    Science.gov (United States)

    Hanlumyuang, Yuranan; Li, Xiaobao; Sharma, Pradeep

    2014-11-14

    Quantum capacitance is a fundamental quantity that can directly reveal many-body interactions among electrons and is expected to play a critical role in nanoelectronics. One of the many tantalizing recent physical revelations about quantum capacitance is that it can possess a negative value, hence allowing for the possibility of enhancing the overall capacitance in some particular material systems beyond the scaling predicted by classical electrostatics. Using detailed quantum mechanical simulations, we found an intriguing result that mechanical strains can tune both signs and values of quantum capacitance. We used a small coaxially gated carbon nanotube as a paradigmatical capacitor system and showed that, for the range of mechanical strain considered, quantum capacitance can be adjusted from very large positive to very large negative values (in the order of plus/minus hundreds of attofarads), compared to the corresponding classical geometric value (0.31035 aF). This finding opens novel avenues in designing quantum capacitance for applications in nanosensors, energy storage, and nanoelectronics.

  4. Efficiency of ozone production by pulsed positive corona discharge in synthetic air

    Energy Technology Data Exchange (ETDEWEB)

    Simek, Milan [Institute of Plasma Physics, Department of Pulsed Plasma Systems, Academy of Sciences of the Czech Republic, Prague (Czech Republic)]. E-mail: simek@ipp.cas.cz; Clupek, Martin [Institute of Plasma Physics, Department of Pulsed Plasma Systems, Academy of Sciences of the Czech Republic, Prague (Czech Republic)

    2002-06-07

    We have studied the efficiency of ozone production by pulsed positive corona discharge in coaxial wire-cylinder geometry at atmospheric pressure. A corona discharge was generated by short ({approx}150 ns) high voltage pulses applied between a silver coated copper wire anode and stainless steel cylinder cathode in synthetic air. A pyrex probe and Teflon tube was used for collecting discharge products and an ozone concentration was monitored outside of the discharge chamber by a non-dispersive UV absorption technique. The production of ozone was investigated as a function of energy density (10{sup -4}-3x10{sup -1} Wh l{sup -1}) delivered to the discharge volume by combining the discharge frequency (0.1-10 Hz) and airflow rate (1-32 l min{sup -1}). From ozone concentration measurements we have evaluated the ozone production, yield and production energy cost. The ozone production yield and cost vary in the range of 15-55 g kWh{sup -1} and 35-110 eV/molecule. (author)

  5. Circuit dependence of the diameter of pulsed positive streamers in air

    Energy Technology Data Exchange (ETDEWEB)

    Briels, T M P [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands); Kos, J [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands); Veldhuizen, E M van [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands); Ebert, U [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands)

    2006-12-21

    The diameter and branching structure of positive streamers in ambient air are investigated with a fast iCCD camera. We use different pulsed power circuits and find that they generate different spatial streamer structures. The electrodes have a point-plane geometry and a distance of 40 or 80 mm, and the peak voltages over the discharge gap are up to 60 kV. Depending on circuit and peak voltage, we observe streamers with diameters varying gradually between 0.2 and 2.5 mm. The streamer velocity increases with the diameter, ranging from 0.07 to 1.5 mm ns{sup -1}, while the current density within the streamers stays almost constant. The thicker streamers extend much further before they branch than the thinner ones. The pulsed power supplies are a switched capacitor supply with an internal resistance of 1 k{omega} and a transmission line transformer supply with an impedance of 200 {omega}; additional resistors change the impedance as well as the voltage rise time in the case of the capacitor supply. We observe that short rise times and low impedance create thick streamers close to the pointed electrode, while a longer rise time as well as a higher impedance create thinner streamers at the same peak voltage over the discharge.

  6. Circuit dependence of the diameter of pulsed positive streamers in air

    International Nuclear Information System (INIS)

    Briels, T M P; Kos, J; Veldhuizen, E M van; Ebert, U

    2006-01-01

    The diameter and branching structure of positive streamers in ambient air are investigated with a fast iCCD camera. We use different pulsed power circuits and find that they generate different spatial streamer structures. The electrodes have a point-plane geometry and a distance of 40 or 80 mm, and the peak voltages over the discharge gap are up to 60 kV. Depending on circuit and peak voltage, we observe streamers with diameters varying gradually between 0.2 and 2.5 mm. The streamer velocity increases with the diameter, ranging from 0.07 to 1.5 mm ns -1 , while the current density within the streamers stays almost constant. The thicker streamers extend much further before they branch than the thinner ones. The pulsed power supplies are a switched capacitor supply with an internal resistance of 1 kΩ and a transmission line transformer supply with an impedance of 200 Ω; additional resistors change the impedance as well as the voltage rise time in the case of the capacitor supply. We observe that short rise times and low impedance create thick streamers close to the pointed electrode, while a longer rise time as well as a higher impedance create thinner streamers at the same peak voltage over the discharge

  7. Quantum control of a chiral molecular motor driven by femtosecond laser pulses: Mechanisms of regular and reverse rotations

    International Nuclear Information System (INIS)

    Yamaki, M.; Hoki, K.; Kono, H.; Fujimura, Y.

    2008-01-01

    Rotational mechanisms of a chiral molecular motor driven by femtosecond laser pulses were investigated on the basis of results of a quantum control simulation. A chiral molecule, (R)-2-methyl-cyclopenta-2,4-dienecarboaldehyde, was treated as a molecular motor within a one-dimensional model. It was assumed that the motor is fixed on a surface and driven in the low temperature limit. Electric fields of femtosecond laser pulses driving both regular rotation of the molecular motor with a plus angular momentum and reverse rotation with a minus one were designed by using a global control method. The mechanism of the regular rotation is similar to that obtained by a conventional pump-dump pulse method: the direction of rotation is the same as that of the initial wave packet propagation on the potential surface of the first singlet (nπ*) excited state S 1 . A new control mechanism has been proposed for the reverse rotation that cannot be driven by a simple pump-dump pulse method. In this mechanism, a coherent Stokes pulse creates a wave packet localized on the ground state potential surface in the right hand side. The wave packet has a negative angular momentum to drive reverse rotation at an early time

  8. Femtosecond pulse with THz repetition frequency based on the coupling between quantum emitters and a plasmonic resonator

    Science.gov (United States)

    Li, Shilei; Ding, Yinxing; Jiao, Rongzhen; Duan, Gaoyan; Yu, Li

    2018-03-01

    Nanoscale pulsed light is highly desirable in nano-integrated optics. In this paper, we obtained femtosecond pulses with THz repetition frequency via the coupling between quantum emitters (QEs) and plasmonic resonators. Our structure consists of a V -groove (VG) plasmonic resonator and a nanowire embedded with two-level QEs. The influences of the incident light intensity and QE number density on the transmission response for this hybrid system are investigated through semiclassical theory and simulation. The results show that the transmission response can be modulated to the pulse form. And the repetition frequency and extinction ratio of the pulses can be controlled by the incident light intensity and QE number density. The reason is that the coupling causes the output power of nanowire to behave as an oscillating form, the oscillating output power in turn causes the field amplitude in the resonator to oscillate over time. A feedback system is formed between the plasmonic resonator and the QEs in the nanowire. This provides a method for generating narrow pulsed lasers with ultrahigh repetition frequencies in plasmonic systems using a continuous wave input, which has potential applications in generating optical clock signals at the nanoscale.

  9. Treatment of Dyeing Wastewater by Using Positive Pulsed Corona Discharge to Water Surface

    Science.gov (United States)

    Young, Sun Mok; Hyun, Tae Ahn; Joeng, Tai Kim

    2007-02-01

    This study investigated the treatment of textile-dyeing wastewater by using an electrical discharge technique (positive pulsed corona discharge). The high-voltage electrode was placed above the surface of the wastewater while the ground electrode was submerged in the wastewater. The electrical discharge starting at the tip of the high voltage electrode propagated toward the surface of the wastewater, producing various oxidative radicals and ozone. Oxygen was used as the working gas instead of air to prevent nitrogen oxides from forming. The simulated wastewater was made up with amaranth, which is a kind of azo dye. The results obtained showed that the chromaticity of the wastewater was almost completely removed within an hour. The ultraviolet/visible spectra of the wastewater treated by the electrical discharge revealed that the total hydrocarbon level also decreased significantly.

  10. Treatment of Dyeing Wastewater by Using Positive Pulsed Corona Discharge to Water Surface

    International Nuclear Information System (INIS)

    Mok, Young Sun; Ahn, Hyun Tae; Kim, Joeng Tai

    2007-01-01

    This study investigated the treatment of textile-dyeing wastewater by using an electrical discharge technique (positive pulsed corona discharge). The high-voltage electrode was placed above the surface of the wastewater while the ground electrode was submerged in the wastewater. The electrical discharge starting at the tip of the high voltage electrode propagated toward the surface of the wastewater, producing various oxidative radicals and ozone. Oxygen was used as the working gas instead of air to prevent nitrogen oxides from forming. The simulated wastewater was made up with amaranth, which is a kind of azo dye. The results obtained showed that the chromaticity of the wastewater was almost completely removed within an hour. The ultraviolet/visible spectra of the wastewater treated by the electrical discharge revealed that the total hydrocarbon level also decreased significantly

  11. Dynamic Characteristics of Positive Pulsed Dielectric Barrier Discharge for Ozone Generation in Air

    Science.gov (United States)

    Wei, Linsheng; Peng, Bangfa; Li, Ming; Zhang, Yafang; Hu, Zhaoji

    2016-02-01

    A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge (DBD) using parallel-plate reactor in air. The electron energy conservation equation is coupled to the electron continuity equation, the heavy species continuity equation, and Poisson's equation for a better description. The reliability of the model is experimentally confirmed. The model can be used to predict the temporal and spatial evolution of species, as well as streamer propagation. The simulation results show that electron density increases nearly exponentially in the direction to the anode at the electron avalanche. Streamer propagation velocity is about 5.26 × 104 m/s from anode to cathode in the simulated condition. The primary positive ion, negative ion, and excited species are O2+, O3- and O2(1Δg) in pulsed DBD in air, respectively. N2O has the largest density among nitrogen oxides. e and N2+ densities in the streamer head increase gradually to maximum values with the development of the streamer. Meanwhile, the O2+, O, O3, N2(A3Σ) and N2O densities reach maximum values in the vicinity of the anode. supported by National Natural Science Foundation of China (Nos. 51366012 and 11105067), Jiangxi Province Young Scientists (Jinggang Star) Cultivation Plan of China (No. 20133BCB23008), Natural Science Foundation of Jiangxi, China (No. 20151BAB206047) and Jiangxi Province Higher School Science and Technology Landing Plan of China (No. KJLD-14015)

  12. Positive and negative gain exceeding unity magnitude in silicon quantum well metal-oxide-semiconductor transistors

    Science.gov (United States)

    Hu, Gangyi; Wijesinghe, Udumbara; Naquin, Clint; Maggio, Ken; Edwards, H. L.; Lee, Mark

    2017-10-01

    Intrinsic gain (AV) measurements on Si quantum well (QW) n-channel metal-oxide-semiconductor (NMOS) transistors show that these devices can have |AV| > 1 in quantum transport negative transconductance (NTC) operation at room temperature. QW NMOS devices were fabricated using an industrial 45 nm technology node process incorporating ion implanted potential barriers to define a lateral QW in the conduction channel under the gate. While NTC at room temperature arising from transport through gate-controlled QW bound states has been previously established, it was unknown whether the quantum NTC mechanism could support gain magnitude exceeding unity. Bias conditions were found giving both positive and negative AV with |AV| > 1 at room temperature. This result means that QW NMOS devices could be useful in amplifier and oscillator applications.

  13. Quantum tunneling recombination in a system of randomly distributed trapped electrons and positive ions.

    Science.gov (United States)

    Pagonis, Vasilis; Kulp, Christopher; Chaney, Charity-Grace; Tachiya, M

    2017-09-13

    During the past 10 years, quantum tunneling has been established as one of the dominant mechanisms for recombination in random distributions of electrons and positive ions, and in many dosimetric materials. Specifically quantum tunneling has been shown to be closely associated with two important effects in luminescence materials, namely long term afterglow luminescence and anomalous fading. Two of the common assumptions of quantum tunneling models based on random distributions of electrons and positive ions are: (a) An electron tunnels from a donor to the nearest acceptor, and (b) the concentration of electrons is much lower than that of positive ions at all times during the tunneling process. This paper presents theoretical studies for arbitrary relative concentrations of electrons and positive ions in the solid. Two new differential equations are derived which describe the loss of charge in the solid by tunneling, and they are solved analytically. The analytical solution compares well with the results of Monte Carlo simulations carried out in a random distribution of electrons and positive ions. Possible experimental implications of the model are discussed for tunneling phenomena in long term afterglow signals, and also for anomalous fading studies in feldspars and apatite samples.

  14. Studies of the pulse charge of lead-acid batteries for PV applications. Part I. Factors influencing the mechanism of the pulse charge of the positive plate

    Energy Technology Data Exchange (ETDEWEB)

    Kirchev, A.; Perrin, M.; Lemaire, E.; Karoui, F.; Mattera, F. [Commissariat de l' Energie Atomique, Institut National de l' Energie Solaire, INES-RDI, Parc Technologique de Savoie Technolac, 50 Avenue du Lac Leman, 73377 Le Bourget du Lac Cedex (France)

    2008-02-15

    The mechanism of the positive plate charge in pulse regime was studied in model lead-acid cells with one positive and two negative plates (8 Ah each) and Ag/Ag{sub 2}SO{sub 4} reference electrodes. The results showed that the evolution of the electrode potential is much slower on the positive plate than on the negative plate. Regardless of this fact, the calculated capacitive current of charge and self-discharge of the electrochemical double layer (EDL) during the 'ON' and 'OFF' half-periods of the pulse current square waves is comparable with the charge current amplitude. The result is due to the high values of the EDL on the surface of the lead dioxide active material. The influence of different factors like state of charge, state of health, pulse frequency, current amplitude and open circuit stay before the polarization was discussed. The previously determined optimal frequency of 1 Hz was associated with a maximum in the average double layer current on frequency dependence. The average double layer current is also maximal at SOC between 75 and 100%. The exchange of the constant current polarization with pulse polarization does not change substantially the mechanism and the overvoltage of the oxygen evolution reaction on the positive plate. The mechanism of the self-discharge of the EDL was also estimated analyzing long-time PPP transients (up to 2 h). It was found that when the PPP is lower than 1.2 V the preferred mechanism of EDL self-discharge is by coupling with the lead sulphate oxidation reaction. At higher values of PPP the EDL self-discharge happens via oxygen evolution. The high faradic efficiency of the pulse charge is due to the chemical oxidation of the Pb(II) ions by the O atoms and OH radicals formed at the oxygen evolution both during the 'ON' and 'OFF' periods. (author)

  15. "Shut up and calculate": the available discursive positions in quantum physics courses

    Science.gov (United States)

    Johansson, Anders; Andersson, Staffan; Salminen-Karlsson, Minna; Elmgren, Maja

    2018-03-01

    Educating new generations of physicists is often seen as a matter of attracting good students, teaching them physics and making sure that they stay at the university. Sometimes, questions are also raised about what could be done to increase diversity in recruitment. Using a discursive perspective, in this study of three introductory quantum physics courses at two Swedish universities, we instead ask what it means to become a physicist, and whether certain ways of becoming a physicist and doing physics is privileged in this process. Asking the question of what discursive positions are made accessible to students, we use observations of lectures and problem solving sessions together with interviews with students to characterize the discourse in the courses. Many students seem to have high expectations for the quantum physics course and generally express that they appreciate the course more than other courses. Nevertheless, our analysis shows that the ways of being a "good quantum physics student" are limited by the dominating focus on calculating quantum physics in the courses. We argue that this could have negative consequences both for the education of future physicists and the discipline of physics itself, in that it may reproduce an instrumental "shut up and calculate"-culture of physics, as well as an elitist physics education. Additionally, many students who take the courses are not future physicists, and the limitation of discursive positions may also affect these students significantly.

  16. False positive rate of carbon monoxide saturation by pulse oximetry of emergency department patients.

    Science.gov (United States)

    Weaver, Lindell K; Churchill, Susan K; Deru, Kayla; Cooney, Darryl

    2013-02-01

    Symptoms of carbon monoxide (CO) poisoning are non-specific. Diagnosis requires suspicion of exposure, confirmed by measuring ambient CO levels or carboxyhemoglobin (COHb). An FDA-approved pulse oximeter (Rad-57) can measure CO saturation (S(pCO)). The device accuracy has implications for clinical decision-making. From April 1 to August 15, 2008, study personnel measured S(pCO) and documented demographic factors at time of clinical blood draw, in a convenience sample of 1,363 subjects presenting to the emergency department at Intermountain Medical Center, Murray, Utah. The technician then assayed COHb. COHb and S(pCO) values were compared by subject; false positive or negative values were defined as S(pCO) at least 3 percentage points greater or less than COHb level, reported by the manufacturer to be ± 1 SD in performance. In 1,363 subjects, 613 (45%) were male, 1,141 (84%) were light-skinned, 14 in shock, 4 with CO poisoning, and 122 (9%) met the criteria for a false positive value (range 3-19 percentage points), while 247 (18%) met the criteria for a false negative value (-13 to -3 percentage points). Risks for a false positive S(pCO) reading included being female and having a lower perfusion index. Methemoglobin, body temperature, and blood pressure also appear to influence the S(pCO) accuracy. There was variability among monitors, possibly related to technician technique, as rotation of monitors among technicians was not enforced. While the Rad-57 pulse oximeter functioned within the manufacturer's specifications, clinicians using the Rad-57 should expect some S(pCO) readings to be significantly higher or lower than COHb measurements, and should not use S(pCO) to direct triage or patient management. An elevated S(pCO) could broaden the diagnosis of CO poisoning in patients with non-specific symptoms. However, a negative S(pCO) level in patients suspected of having CO poisoning should never rule out CO poisoning, and should always be confirmed by COHb. © 2013

  17. Quantum transition probabilities during a perturbing pulse: Differences between the nonadiabatic results and Fermi's golden rule forms

    Science.gov (United States)

    Mandal, Anirban; Hunt, Katharine L. C.

    2018-05-01

    For a perturbed quantum system initially in the ground state, the coefficient ck(t) of excited state k in the time-dependent wave function separates into adiabatic and nonadiabatic terms. The adiabatic term ak(t) accounts for the adjustment of the original ground state to form the new ground state of the instantaneous Hamiltonian H(t), by incorporating excited states of the unperturbed Hamiltonian H0 without transitions; ak(t) follows the adiabatic theorem of Born and Fock. The nonadiabatic term bk(t) describes excitation into another quantum state k; bk(t) is obtained as an integral containing the time derivative of the perturbation. The true transition probability is given by |bk(t)|2, as first stated by Landau and Lifshitz. In this work, we contrast |bk(t)|2 and |ck(t)|2. The latter is the norm-square of the entire excited-state coefficient which is used for the transition probability within Fermi's golden rule. Calculations are performed for a perturbing pulse consisting of a cosine or sine wave in a Gaussian envelope. When the transition frequency ωk0 is on resonance with the frequency ω of the cosine wave, |bk(t)|2 and |ck(t)|2 rise almost monotonically to the same final value; the two are intertwined, but they are out of phase with each other. Off resonance (when ωk0 ≠ ω), |bk(t)|2 and |ck(t)|2 differ significantly during the pulse. They oscillate out of phase and reach different maxima but then fall off to equal final values after the pulse has ended, when ak(t) ≡ 0. If ωk0 ω. While the transition probability is rising, the midpoints between successive maxima and minima fit Gaussian functions of the form a exp[-b(t - d)2]. To our knowledge, this is the first analysis of nonadiabatic transition probabilities during a perturbing pulse.

  18. Entanglement and the process of measuring the position of a quantum particle

    International Nuclear Information System (INIS)

    Apel, V.M.; Curilef, S.; Plastino, A.R.

    2015-01-01

    We explore the entanglement-related features exhibited by the dynamics of a composite quantum system consisting of a particle and an apparatus (here referred to as the “pointer”) that measures the position of the particle. We consider measurements of finite duration, and also the limit case of instantaneous measurements. We investigate the time evolution of the quantum entanglement between the particle and the pointer, with special emphasis on the final entanglement associated with the limit case of an impulsive interaction. We consider entanglement indicators based on the expectation values of an appropriate family of observables, and also an entanglement measure computed on particular exact analytical solutions of the particle–pointer Schrödinger equation. The general behavior exhibited by the entanglement indicators is consistent with that shown by the entanglement measure evaluated on particular analytical solutions of the Schrödinger equation. In the limit of instantaneous measurements the system’s entanglement dynamics corresponds to that of an ideal quantum measurement process. On the contrary, we show that the entanglement evolution corresponding to measurements of finite duration departs in important ways from the behavior associated with ideal measurements. In particular, highly localized initial states of the particle lead to highly entangled final states of the particle–pointer system. This indicates that the above mentioned initial states, in spite of having an arbitrarily small position uncertainty, are not left unchanged by a finite-duration position measurement process. - Highlights: • We explore entanglement features of a quantum position measurement. • We consider instantaneous and finite-duration measurements. • We evaluate the entanglement of exact time-dependent particle–pointer states

  19. Experimental investigation of quantum key distribution with position and momentum of photon pairs

    International Nuclear Information System (INIS)

    Almeida, M.P.; Walborn, S.P.; Souto Ribeiro, P.H.

    2005-01-01

    We investigate the utility of Einstein-Podolsky-Rosen correlations of the position and momentum of photon pairs from parametric down-conversion in the implementation of a secure quantum key distribution protocol. We show that security is guaranteed by the entanglement between down-converted pairs, and can be checked by either direct comparison of Alice and Bob's measurement results or evaluation of an inequality of the sort proposed by Mancini et al. [Phys. Rev. Lett. 88, 120401 (2002)

  20. Development of a positive column pulsed capillary discharge source for use with high resolution Fourier transform spectrometer

    International Nuclear Information System (INIS)

    Syed, W A A

    2002-01-01

    We report the designing and application of a positive column pulsed capillary discharge with the Fourier transform spectrometer (FTS). The pulsed light source has been used for the first time with the ultraviolet FTS. The experiment has been carried out with the high energy pulsed discharge with energy of 2-3 J lasting about 300 ns. A system has been developed to trigger the discharge at about 600 Hz with the pulses directly taken from the FTS sampling system. The spectrum of Ar III has been recorded in the 19 000-50 000 cm -1 region with good signal to noise ratio. The results have opened a wide range of applications in spectroscopy of multiply ionized species

  1. Ultra-low power anti-crosstalk collision avoidance light detection and ranging using chaotic pulse position modulation approach

    International Nuclear Information System (INIS)

    Hao Jie; Gong Ma-li; Du Peng-fei; Lu Bao-jie; Zhang Fan; Zhang Hai-tao; Fu Xing

    2016-01-01

    A novel concept of collision avoidance single-photon light detection and ranging (LIDAR) for vehicles has been demonstrated, in which chaotic pulse position modulation is applied on the transmitted laser pulses for robust anti-crosstalk purposes. Besides, single-photon detectors (SPD) and time correlated single photon counting techniques are adapted, to sense the ultra-low power used for the consideration of compact structure and eye safety. Parameters including pulse rate, discrimination threshold, and number of accumulated pulses have been thoroughly analyzed based on the detection requirements, resulting in specified receiver operating characteristics curves. Both simulation and indoor experiments were performed to verify the excellent anti-crosstalk capability of the presented collision avoidance LIDAR despite ultra-low transmitting power. (paper)

  2. Amplifiable DNA from Gram-negative and Gram-positive bacteria by a low strength pulsed electric field method

    Science.gov (United States)

    Vitzthum, Frank; Geiger, Georg; Bisswanger, Hans; Elkine, Bentsian; Brunner, Herwig; Bernhagen, Jürgen

    2000-01-01

    An efficient electric field-based procedure for cell disruption and DNA isolation is described. Isoosmotic suspensions of Gram-negative and Gram-positive bacteria were treated with pulsed electric fields of Pulses had an exponential decay waveform with a time constant of 3.4 µs. DNA yield was linearly dependent on time or pulse number, with several thousand pulses needed. Electrochemical side-effects and electrophoresis were minimal. The lysates contained non-fragmented DNA which was readily amplifiable by PCR. As the method was not limited to samples of high specific resistance, it should be applicable to physiological fluids and be useful for genomic and DNA diagnostic applications. PMID:10734214

  3. Position-momentum uncertainty relations in the presence of quantum memory

    Energy Technology Data Exchange (ETDEWEB)

    Furrer, Fabian, E-mail: furrer@eve.phys.s.u-tokyo.ac.jp [Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Berta, Mario [Institute for Quantum Information and Matter, Caltech, Pasadena, California 91125 (United States); Institute for Theoretical Physics, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zürich (Switzerland); Tomamichel, Marco [School of Physics, The University of Sydney, Sydney 2006 (Australia); Centre for Quantum Technologies, National University of Singapore, Singapore 117543 (Singapore); Scholz, Volkher B. [Institute for Theoretical Physics, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zürich (Switzerland); Christandl, Matthias [Institute for Theoretical Physics, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zürich (Switzerland); Department of Mathematical Sciences, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen (Denmark)

    2014-12-15

    A prominent formulation of the uncertainty principle identifies the fundamental quantum feature that no particle may be prepared with certain outcomes for both position and momentum measurements. Often the statistical uncertainties are thereby measured in terms of entropies providing a clear operational interpretation in information theory and cryptography. Recently, entropic uncertainty relations have been used to show that the uncertainty can be reduced in the presence of entanglement and to prove security of quantum cryptographic tasks. However, much of this recent progress has been focused on observables with only a finite number of outcomes not including Heisenberg’s original setting of position and momentum observables. Here, we show entropic uncertainty relations for general observables with discrete but infinite or continuous spectrum that take into account the power of an entangled observer. As an illustration, we evaluate the uncertainty relations for position and momentum measurements, which is operationally significant in that it implies security of a quantum key distribution scheme based on homodyne detection of squeezed Gaussian states.

  4. An efficient fluorescent single-particle position tracking system for long-term pulsed measurements of nitrogen-vacancy centers in diamond

    Science.gov (United States)

    Kim, Kiho; Yun, Jiwon; Lee, Donghyuck; Kim, Dohun

    2018-02-01

    A simple and convenient design enables real-time three-dimensional position tracking of nitrogen-vacancy (NV) centers in diamond. The system consists entirely of commercially available components (a single-photon counter, a high-speed digital-to-analog converter, a phase-sensitive detector-based feedback device, and a piezo stage), eliminating the need for custom programming or rigorous optimization processes. With a large input range of counters and trackers combined with high sensitivity of single-photon counting, high-speed position tracking (upper bound recovery time of 0.9 s upon 250 nm of step-like positional shift) not only of bright ensembles, but also of low-photon-collection-efficiency single to few NV centers (down to 103 s-1) is possible. The tracking requires position modulation of only 10 nm, which allows simultaneous position tracking and pulsed measurements in the long term. Therefore, this tracking system enables measuring a single-spin magnetic resonance and Rabi oscillations at a very high resolution even without photon collection optimization. The system is widely applicable to various fields related to NV center quantum manipulation research such as NV optical trapping, NV tracking in fluid dynamics, and biological sensing using NV centers inside a biological cell.

  5. A characterization of positive linear maps and criteria of entanglement for quantum states

    International Nuclear Information System (INIS)

    Hou Jinchuan

    2010-01-01

    Let H and K be (finite- or infinite-dimensional) complex Hilbert spaces. A characterization of positive completely bounded normal linear maps from B(H) into B(K) is given, which particularly gives a characterization of positive elementary operators including all positive linear maps between matrix algebras. This characterization is then applied to give a representation of quantum channels (operations) between infinite-dimensional systems. A necessary and sufficient criterion of separability is given which shows that a state ρ on HxK is separable if and only if (ΦxI)ρ ≥ 0 for all positive finite-rank elementary operators Φ. Examples of NCP and indecomposable positive linear maps are given and are used to recognize some entangled states that cannot be recognized by the PPT criterion and the realignment criterion.

  6. A characterization of positive linear maps and criteria of entanglement for quantum states

    Science.gov (United States)

    Hou, Jinchuan

    2010-09-01

    Let H and K be (finite- or infinite-dimensional) complex Hilbert spaces. A characterization of positive completely bounded normal linear maps from {\\mathcal B}(H) into {\\mathcal B}(K) is given, which particularly gives a characterization of positive elementary operators including all positive linear maps between matrix algebras. This characterization is then applied to give a representation of quantum channels (operations) between infinite-dimensional systems. A necessary and sufficient criterion of separability is given which shows that a state ρ on HotimesK is separable if and only if (ΦotimesI)ρ >= 0 for all positive finite-rank elementary operators Φ. Examples of NCP and indecomposable positive linear maps are given and are used to recognize some entangled states that cannot be recognized by the PPT criterion and the realignment criterion.

  7. Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications

    Directory of Open Access Journals (Sweden)

    Sethakaset Ubolthip

    2005-01-01

    Full Text Available We propose a novel differential amplitude pulse-position modulation (DAPPM for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR. The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM depending on the number of amplitude levels and the maximum length of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about and more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM . When the number of bits per symbol is the same, PAM requires more power, and DH-PIM less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.

  8. Measurement of gas temperature and OH density in the afterglow of pulsed positive corona discharge

    International Nuclear Information System (INIS)

    Ono, Ryo; Oda, Tetsuji

    2008-01-01

    The gas temperature and OH density in the afterglow of pulsed positive corona discharge are measured using the laser-induced predissociation fluorescence (LIPF) of OH radicals. Discharge occurs in a 13 mm point-to-plane gap in an atmospheric-pressure H 2 O(2.8%)/O 2 (2.0%)/N 2 mixture. The temperature measurement shows that (i) the temperature increases after discharge and (ii) the temperature near the anode tip (within 1 mm from the anode tip) is much higher than that of the rest of the discharge volume. Near the anode tip, the temperature increases from 500 K (t = 0 μs) to 1100 K (t = 20 μs), where t is the postdischarge time, while it increases from 400 K (t = 0 μs) to 700 K (t = 100 μs) in the rest of the discharge volume away from the anode tip. This temperature difference between the two volumes (near and far from the anode tip) causes a difference in the decay rate of OH density: OH density near the anode tip decays approximately 10 times slower than that far from the tip. The spatial distribution of OH density shows good agreement with that of the secondary streamer luminous intensity. This shows that OH radicals are mainly produced in the secondary streamer, not in the primary one

  9. Efficient ion heating of tokamak plasma by application of positive and negative current pulse in TRIAM-1

    International Nuclear Information System (INIS)

    Toi, Kazuo; Hiraki, Naoji; Nakamura, Kazuo; Mitarai, Osamu; Kawai, Yoshinobu

    1980-01-01

    The efficient heating of bulk ions of tokamak plasma is observed by application of the pulsed toroidal electric field much higher than the Dreicer field with the positive and negative polarities for the ohmic heating field. No deleterious effect on the confinement properties of tokamak plasma appears by the heating. The decay time of ion temperature raised by the heating pulse agrees well with the prediction by the neoclassical transport theory. The magnitude of the current induced by the pulsed electric field with the positive polarity is limited by the violent current disruption. In the case of the negative polarity, this is limited by lack of the MHD equilibrium due to vanishing the total plasma current. The ratio of drift velocity to electron thermal one / attains around 0.5, which suggests that the efficient ion heating may be due to the current-driven turbulence. (author)

  10. Efficient ion heating of tokamak plasma by application of positive and negative current pulse in TRIAM-1

    Energy Technology Data Exchange (ETDEWEB)

    Toi, K; Hiraki, N; Nakamura, K; Mitarai, O; Kawai, Y [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1980-02-01

    The efficient heating of bulk ions of tokamak plasma is observed by application of the pulsed toroidal electric field much higher than the Dreicer field with the positive and negative polarities for the ohmic heating field. No deleterious effect on the confinement properties of tokamak plasma appears by the heating. The decay time of ion temperature raised by the heating pulse agrees well with the prediction by the neoclassical transport theory. The magnitude of the current induced by the pulsed electric field with the positive polarity is limited by the violent current disruption. In the case of the negative polarity, this is limited by lack of the MHD equilibrium due to vanishing the total plasma current. The ratio of drift velocity to electron thermal one / attains around 0.5, which suggests that the efficient ion heating may be due to the current-driven turbulence.

  11. Pulsed voltage deposited lead selenide thin film as efficient counter electrode for quantum-dot-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Bin Bin [Key Laboratory of Macromolecular Science of Shaanxi Province & School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Department of Chemical Engineering, Institute of Chemical Industry, Shaanxi Institute of Technology, Xi’an 710300 (China); Wang, Ye Feng [Key Laboratory of Macromolecular Science of Shaanxi Province & School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Wang, Xue Qing [Faculty of Chemical, Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024 (China); Zeng, Jing Hui, E-mail: jhzeng@ustc.edu [Key Laboratory of Macromolecular Science of Shaanxi Province & School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China)

    2016-04-30

    Highlights: • PbSe thin film is deposited on FTO glass by a pulse voltage electrodeposition method. • The thin film is used as counter electrode (CE) in quantum dot-sensitized solar cell. • Superior electrocatalytic activity and stability in the polysulfide electrolyte is received. • The narrow band gap characteristics and p-type conductivity enhances the cell efficiency. • An efficiency of 4.67% is received for the CdS/CdSe co-sensitized solar cells. - Abstract: Lead selenide (PbSe) thin films were deposited on fluorine doped tin oxide (FTO) glass by a facile one-step pulse voltage electrodeposition method, and used as counter electrode (CE) in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). A power conversion efficiency of 4.67% is received for the CdS/CdSe co-sensitized solar cells, which is much better than that of 2.39% received using Pt CEs. The enhanced performance is attributed to the extended absorption in the near infrared region, superior electrocatalytic activity and p-type conductivity with a reflection of the incident light at the back electrode in addition. The physical and chemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), reflectance spectra, electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The present work provides a facile pathway to an efficient CE in the QDSSCs.

  12. Crossover from negative to positive magnetoresistance in the double quantum well system with different starting disorder

    International Nuclear Information System (INIS)

    Kannan, E S; Karamad, M; Kim, Gil-Ho; Farrer, I; Ritchie, D A

    2010-01-01

    Magnetotransport measurements were performed in two widely separated double quantum well systems with different starting disorders. In the weak magnetic field regime, a crossover from negative to positive magnetoresistance in the longitudinal resistivity was observed in the system with weak disorder when the electron densities in the neighboring wells were significantly unbalanced. The crossover was found to be the result of the exchange-energy-assisted interactions between the electrons occupying the lowest subbands in the neighboring wells. In the case of the system with strong disorder short range scattering dominated the scattering process and no such transition in longitudinal resistivity in the low magnetic field regime was observed. However, at high magnetic fields, sharp peaks were observed in the Hall resistance due to the interaction between the edge states in the quantum Hall regime.

  13. Electroluminescence property improvement by adjusting quantum wells’ position relative to p-doped region in InGaN/GaN multiple-quantum-well light emitting diodes

    Directory of Open Access Journals (Sweden)

    P. Chen

    2017-03-01

    Full Text Available The hole distribution and electroluminescence property improvement by adjusting the relative position between quantum wells and p-doped region in InGaN/GaN multiple-quantum-well structures are experimentally and theoretically investigated. Five designed samples with different barrier layer parameters of multiple-quantum-well structure are grown by MOCVD and then fabricated into devices. The electroluminescence properties of these samples are measured and compared. It is found that the output electroluminescence intensity of samples is enhanced if the position of quantum wells shifts towards p-side, while the output power is reduced if their position is shifted towards the n-side. The theoretical calculation of characteristics of these devices using the simulation program APSYS agrees well with the experimental data, illustrating that the effect of relative position between p-doped region and quantum wells on the improvement of hole distribution and electroluminescence performance is significant, especially for InGaN/GaN multiple-quantum-well devices operated under high injection condition.

  14. 35 GHz passive mode-locking of InGaAs/GaAs quantum dot lasers at 1.3 μm with Fourier-limited pulses

    DEFF Research Database (Denmark)

    Kuntz, M.; Fiol, G.; Laemmlin, M.

    2004-01-01

    We report 35 GHz passive mode-locking and 20 GHz hybrid mode-locking of quantum dot (QD) lasers at 1.3 ìm. Our investigations show ultrafast absorber recovery times and for the first time transform-limited mode-locked pulses.......We report 35 GHz passive mode-locking and 20 GHz hybrid mode-locking of quantum dot (QD) lasers at 1.3 ìm. Our investigations show ultrafast absorber recovery times and for the first time transform-limited mode-locked pulses....

  15. Study on quantum beam science by using ultra short electron pulse, FEL, and slow positron beam at ISIR (Institute of Science and Industrial Research), Osaka University

    International Nuclear Information System (INIS)

    Yoshida, Y.; Tagawa, S.; Okuda, S.; Honda, Y.; Kimura, N.; Yamamoto, T.; Isoyama, G.

    1995-01-01

    Three projects for quantum beam science, an ultra fast electron pulse, a free electron laser, and a slow positron beam, has been started by using 38 MeV L-band and 150 MeV S-band linacs at ISIR in Osaka University. Both study on the production of three beams and study on quantum material science by using three beams will play an important role in the beam science. (author)

  16. Patterning effects in quantum dot amplifiers characterized through pump probe spectroscopy using two pump pulses

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Poel, Mike van der; Laemmlin, M.

    2004-01-01

    Patterning effects at ultrahigh bitrates in quantum dot amplifiers are investigated by a novel experimental technique. Slow carrier dynamics in the excited states and wetting layer are found to limit the potential for ultrahigh-speed signal processing....

  17. Time-resolved measurement of the quantum states of photons using two-photon interference with short-time reference pulses

    International Nuclear Information System (INIS)

    Ren Changliang; Hofmann, Holger F.

    2011-01-01

    To fully utilize the energy-time degree of freedom of photons for optical quantum-information processes, it is necessary to control and characterize the temporal quantum states of the photons at extremely short time scales. For measurements of the temporal coherence of the quantum states beyond the time resolution of available detectors, two-photon interference with a photon in a short-time reference pulse may be a viable alternative. In this paper, we derive the temporal measurement operators for the bunching statistics of a single-photon input state with a photon from a weak coherent reference pulse. It is shown that the effects of the pulse shape of the reference pulse can be expressed in terms of a spectral filter selecting the bandwidth within which the measurement can be treated as an ideal projection on eigenstates of time. For full quantum tomography, temporal coherence can be determined by using superpositions of reference pulses at two different times. Moreover, energy-time entanglement can be evaluated based on the two-by-two entanglement observed in the coherences between pairs of detection times.

  18. Quantum switching of π-electron rotations in a nonplanar chiral molecule by using linearly polarized UV laser pulses.

    Science.gov (United States)

    Mineo, Hirobumi; Yamaki, Masahiro; Teranishi, Yoshiaki; Hayashi, Michitoshi; Lin, Sheng Hsien; Fujimura, Yuichi

    2012-09-05

    Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.

  19. 4th meeting on advanced pulsed-neutron research on quantum functions in nano-scale materials

    International Nuclear Information System (INIS)

    2006-07-01

    Toward the worldwide realization of high-intensity pulsed neutron source, KEK (High Energy Accelerator Research Organization) proceeds the research by composing 6 research groups as neutron science initiation base to initiate new neutron science. The papers generalizing the researches for 2 years were presented at this meeting. KENS (Neutron Science Laboratory, KEK) shut down on March 22nd in 2006, and KEK will continue the research utilizing the pulsed neutron by using foreign facilities until the completion of J-PARC from now on. At international session in this meeting, the accomplishments and future prospects about the Japan-United Kingdom science and technology collaboration project, and about the research collaboration projects with IPNS (Intense Pulsed Neutron Source, ANL) and LANSCE (Los Alamos Neutron Science Center) were presented. Especially in the latter projects, the first accomplishment was reported under the present agreement. In addition, Meeting on structural study of proteins in aqueous solutions' and 'Meeting on hydrogen quantum atomics study' were held as satellite meetings. (J.P.N)

  20. Pulse position modulation for compact all-fiber vehicle laser rangefinder development

    Science.gov (United States)

    Mao, Xuesong; Cheng, Yongzhi; Xiong, Ying; Inoue, Daisuke; Kagami, Manabu

    2017-10-01

    We propose a method for developing small all-fiber vehicle laser rangefinders that is based on pulse position modulation (PPM) and data integration and present a theoretical study on its performance. Compared with spatial coupling, which is employed by most of the current commercial vehicle laser rangefinders, fiber coupling has the advantage that it can guide laser echoes into the interior of a car, so the electronic components following the photodiode can operate in a moderate-temperature environment. However, optical fibers have numerical apertures (NAs), which means that a laser beam from a receiving lens cannot be coupled into an optical fiber if its incident angle exceeds the critical value. Therefore, the effective size of the receiving lens is typically small since it is limited by its focal length and the NA of the fiber, causing the power of the laser echoes gathered by the receiving lens to be insufficient for performing target identification. Instead of increasing the peak transmitting laser power unrestrictedly, PPM and data integration effectively compensate for the low signal-to-noise ratio that results from the effective receiving lens size reduction. We validated the proposed method by conducting numerical simulations and performance analysis. Finally, we compared the proposed method with pseudorandom noise (PN) code modulation and found that, although the two methods perform equally well in single-target measurement scenarios, PPM is more effective than PN code modulation for multitarget measurement. In addition, PPM enables the transmission of laser beams with higher peak powers and requires less computation than PN code modulation does.

  1. Position sensitive photon detectors using epitaxial InGaAs/InAlAs quantum wells

    International Nuclear Information System (INIS)

    Ganbold, T.; Antonelli, M.; Cautero, G.; Jark, H.; Eichert, D.M.; Cucini, R.; Menk, R.H.; Biasiol, G.

    2014-01-01

    This work deals with the investigation of novel position-sensitive devices based on InGaAs/InAlAs quantum wells, which could be applied to several applications of either synchrotron or conventional light sources. Such devices may be used as fast and efficient detectors due to the direct, low-energy band gap and high electron mobility at room temperature. Metamorphic In 0.75 Ga 0.25 As/In 0.75 Al 0.25 As quantum wells containing a two-dimensional electron gas were grown by molecular beam epitaxy. Two devices with size of 5 × 5 mm 2 were prepared by using optical lithography. In the first, the active layers were segmented into four electrically insulated quadrants. Indium ohmic contacts were realized on the corner of each quadrant (for readout) and on the back surface (for bias). In the second, the quantum well was left unsegmented and covered by 400 nm of Al providing a single bias electrode, while four readout electrodes were fabricated on the back side by depositing and segmenting a Ni/Ge/Au layer. Photo-generated carriers can be collected at the readout electrodes by biasing from either the QW side or the back side of the devices during beam exposure. Individual currents obtained from each electrode allow monitoring of both the position and the intensity of the impinging beam for photon energies ranging from visible to hard X-ray. Such detector prototypes were tested with synchrotron radiation. Moreover, the position of the beam can be estimated with a precision of 800 nm in the segmented QW. A lower precision of 10 μm was recorded in the unsegmented QW due to the charge diffusion through the 500-μm-thick wafer, with however a lower electronic noise due to the better uniformity of the contacts

  2. Position-based coding and convex splitting for private communication over quantum channels

    Science.gov (United States)

    Wilde, Mark M.

    2017-10-01

    The classical-input quantum-output (cq) wiretap channel is a communication model involving a classical sender X, a legitimate quantum receiver B, and a quantum eavesdropper E. The goal of a private communication protocol that uses such a channel is for the sender X to transmit a message in such a way that the legitimate receiver B can decode it reliably, while the eavesdropper E learns essentially nothing about which message was transmitted. The ɛ -one-shot private capacity of a cq wiretap channel is equal to the maximum number of bits that can be transmitted over the channel, such that the privacy error is no larger than ɛ \\in (0,1). The present paper provides a lower bound on the ɛ -one-shot private classical capacity, by exploiting the recently developed techniques of Anshu, Devabathini, Jain, and Warsi, called position-based coding and convex splitting. The lower bound is equal to a difference of the hypothesis testing mutual information between X and B and the "alternate" smooth max-information between X and E. The one-shot lower bound then leads to a non-trivial lower bound on the second-order coding rate for private classical communication over a memoryless cq wiretap channel.

  3. Numerical studies of entangled positive-partial-transpose states in composite quantum systems

    International Nuclear Information System (INIS)

    Leinaas, Jon Magne; Sollid, Per Oyvind; Myrheim, Jan

    2010-01-01

    We report here on the results of numerical searches for PPT states in a series of bipartite quantum systems of low dimensions. PPT states are represented by density matrices that remain positive semidefinite under partial transposition with respect to one of the subsystems, and our searches are for such states with specified ranks for the density matrix and its partial transpose. For a series of different ranks extremal PPT states and nonextremal entangled PPT states have been found. The results are listed in tables and charted in diagrams. Comparison of the results for systems of different dimensions reveals several regularities. We discuss lower and upper bounds on the ranks of extremal PPT states.

  4. Phase transitions and reflection positivity for a class of quantum lattice systems

    International Nuclear Information System (INIS)

    Perez, J.F.; Wreszinski, W.F.

    1980-08-01

    A form reflection positivity in planes containing sites is proved for a class of quantum lattice systems. Two apllications to typical models are given: a proof of phase transition of ferromagnetic type by the method of infrared bounds for hhe Fisher-stabilized Ising antiferromagnet in an external magnetic field with parallel and tranverse components, and a proof of a phase transition of antiferromagnetic type for the same model with no stabilization by a suitable version of the Peierls argument. The spherical model is also discussed in an appendix. (Author) [pt

  5. Deep tissue optical imaging of upconverting nanoparticles enabled by exploiting higher intrinsic quantum yield through use of millisecond single pulse excitation with high peak power

    DEFF Research Database (Denmark)

    Liu, Haichun; Xu, Can T.; Dumlupinar, Gökhan

    2013-01-01

    We have accomplished deep tissue optical imaging of upconverting nanoparticles at 800 nm, using millisecond single pulse excitation with high peak power. This is achieved by carefully choosing the pulse parameters, derived from time-resolved rate-equation analysis, which result in higher intrinsic...... quantum yield that is utilized by upconverting nanoparticles for generating this near infrared upconversion emission. The pulsed excitation approach thus promises previously unreachable imaging depths and shorter data acquisition times compared with continuous wave excitation, while simultaneously keeping...... therapy and remote activation of biomolecules in deep tissues....

  6. Decoy state method for quantum cryptography based on phase coding into faint laser pulses

    Science.gov (United States)

    Kulik, S. P.; Molotkov, S. N.

    2017-12-01

    We discuss the photon number splitting attack (PNS) in systems of quantum cryptography with phase coding. It is shown that this attack, as well as the structural equations for the PNS attack for phase encoding, differs physically from the analogous attack applied to the polarization coding. As far as we know, in practice, in all works to date processing of experimental data has been done for phase coding, but using formulas for polarization coding. This can lead to inadequate results for the length of the secret key. These calculations are important for the correct interpretation of the results, especially if it concerns the criterion of secrecy in quantum cryptography.

  7. Quantum dynamics of an electric charge in an oscillating pulsed magnetic field

    International Nuclear Information System (INIS)

    Oliveira, I.S.; Guimaraes, A.P.; Silva, X.A. da

    1996-11-01

    The motion of a charged particle under the action of a time-dependent oscillating magnetic field has been investigated. For one and two magnetic pulses were obtained analytical expressions for the free current decay and current echo in agreement with a recently proposed classical description of electrical current in fields E and B. When the resonance condition is achieved, the axis of quantization is turned over by 90 degrees. The results suggest a magnetic pulsed resonant method to separate charged particles in a beam. (author). 12 refs

  8. Polarization spectroscopy of positive and negative trions in an InAs quantum dot

    Science.gov (United States)

    Ware, Morgan E.; Bracker, Allan S.; Stinaff, Eric; Gammon, Daniel; Gershoni, David; Korenev, Vladimir L.

    2005-02-01

    Using polarization-sensitive photoluminescence and photoluminescence excitation spectroscopy, we study single InAs/GaAs self-assembled quantum dots. The dots were embedded in an n-type, Schottky diode structure allowing for control of the charge state. We present here the exciton, singly charged exciton (positive and negative trions), and the twice negatively charged exciton. For non-resonant excitation below the wetting layer, we observed a large degree of polarization memory from the radiative recombination of both the positive and negative trions. In excitation spectra, through the p-shell, we have found several sharp resonances in the emission from the s-shell recombination of the dot in all charged states. Some of these excitation resonances exhibit strong coulomb shifts upon addition of charges into the quantum dot. One particular resonance of the negatively charged trion was found to exhibit a fine structure doublet under circular polarization. This observation is explained in terms of resonant absorption into the triplet states of the negative trion.

  9. High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

    DEFF Research Database (Denmark)

    Duun, Sune Bro; Haahr, Rasmus Grønbek; Hansen, Ole

    2010-01-01

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized...

  10. Time-Resolved Quantum Cascade Laser Absorption Spectroscopy of Pulsed Plasma Assisted Chemical Vapor Deposition Processes Containing BCl3

    Science.gov (United States)

    Lang, Norbert; Hempel, Frank; Strämke, Siegfried; Röpcke, Jürgen

    2011-08-01

    In situ measurements are reported giving insight into the plasma chemical conversion of the precursor BCl3 in industrial applications of boriding plasmas. For the online monitoring of its ground state concentration, quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range was applied in a plasma assisted chemical vapor deposition (PACVD) reactor. A compact quantum cascade laser measurement and control system (Q-MACS) was developed to allow a flexible and completely dust-sealed optical coupling to the reactor chamber of an industrial plasma surface modification system. The process under the study was a pulsed DC plasma with periodically injected BCl3 at 200 Pa. A synchronization of the Q-MACS with the process control unit enabled an insight into individual process cycles with a sensitivity of 10-6 cm-1·Hz-1/2. Different fragmentation rates of the precursor were found during an individual process cycle. The detected BCl3 concentrations were in the order of 1014 molecules·cm-3. The reported results of in situ monitoring with QCLAS demonstrate the potential for effective optimization procedures in industrial PACVD processes.

  11. Analysis of the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery

    Directory of Open Access Journals (Sweden)

    Samuel Arba-Mosquera

    2012-01-01

    Conclusions: The proposed model can be used for comparison of laser systems used for ablation processes. Due to the pseudo-random nature of eye movements, positioning errors of single pulses are much larger than observed decentrations in the clinical settings. There is no single parameter that ‘alone’ minimizes the positioning error. It is the optimal combination of the several parameters that minimizes the error. The results of this analysis are important to understand the limitations of correcting very irregular ablation patterns.

  12. Maximally-localized position, Euclidean path-integral, and thermodynamics in GUP quantum mechanics

    Science.gov (United States)

    Bernardo, Reginald Christian S.; Esguerra, Jose Perico H.

    2018-04-01

    In dealing with quantum mechanics at very high energies, it is essential to adapt to a quasiposition representation using the maximally-localized states because of the generalized uncertainty principle. In this paper, we look at maximally-localized states as eigenstates of the operator ξ = X + iβP that we refer to as the maximally-localized position. We calculate the overlap between maximally-localized states and show that the identity operator can be expressed in terms of the maximally-localized states. Furthermore, we show that the maximally-localized position is diagonal in momentum-space and that the maximally-localized position and its adjoint satisfy commutation and anti-commutation relations reminiscent of the harmonic oscillator commutation and anti-commutation relations. As application, we use the maximally-localized position in developing the Euclidean path-integral and introduce the compact form of the propagator for maximal localization. The free particle momentum-space propagator and the propagator for maximal localization are analytically evaluated up to quadratic-order in β. Finally, we obtain a path-integral expression for the partition function of a thermodynamic system using the maximally-localized states. The partition function of a gas of noninteracting particles is evaluated. At temperatures exceeding the Planck energy, we obtain the gas' maximum internal energy N / 2 β and recover the zero heat capacity of an ideal gas.

  13. Pseudo-Hermitian coherent states under the generalized quantum condition with position-dependent mass

    International Nuclear Information System (INIS)

    Yahiaoui, S A; Bentaiba, M

    2012-01-01

    In the context of the factorization method, we investigate the pseudo-Hermitian coherent states and their Hermitian counterpart coherent states under the generalized quantum condition in the framework of a position-dependent mass. By considering a specific modification in the superpotential, suitable annihilation and creation operators are constructed in order to reproduce the Hermitian counterpart Hamiltonian in the factorized form. We show that by means of these ladder operators, we can construct a wide range of exactly solvable potentials as well as their accompanying coherent states. Alternatively, we explore the relationship between the pseudo-Hermitian Hamiltonian and its Hermitian counterparts, obtained from a similarity transformation, to construct the associated pseudo-Hermitian coherent states. These latter preserve the structure of Perelomov’s states and minimize the generalized position–momentum uncertainty principle. 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)

  14. Propagator with positive cosmological constant in the 3D Euclidean quantum gravity toy model

    International Nuclear Information System (INIS)

    Bunting, William E; Rovelli, Carlo

    2014-01-01

    We study the propagator on a single tetrahedron in a three-dimensional toy model of quantum gravity with positive cosmological constant. The cosmological constant is included in the model via q-deformation of the spatial symmetry algebra, that is, we use the Turaev–Viro amplitude. The expected repulsive effect of dark energy is recovered in numerical and analytic calculations of the propagator at large scales comparable to the infrared cutoff. However, due to the simplicity of the model, we do not obtain the exact Newton limit of the propagator. This is a first step toward the similar calculation in the full 3+1 dimensional theory with larger numbers of simplicies. (paper)

  15. Geometrical conditions for completely positive trace-preserving maps and their application to a quantum repeater and a state-dependent quantum cloning machine

    International Nuclear Information System (INIS)

    Carlini, A.; Sasaki, M.

    2003-01-01

    We address the problem of finding optimal CPTP (completely positive trace-preserving) maps between a set of binary pure states and another set of binary generic mixed state in a two-dimensional space. The necessary and sufficient conditions for the existence of such CPTP maps can be discussed within a simple geometrical picture. We exploit this analysis to show the existence of an optimal quantum repeater which is superior to the known repeating strategies for a set of coherent states sent through a lossy quantum channel. We also show that the geometrical formulation of the CPTP mapping conditions can be a simpler method to derive a state-dependent quantum (anti) cloning machine than the study so far based on the explicit solution of several constraints imposed by unitarity in an extended Hilbert space

  16. Receiver Architecture for 12.5 Gb/s 16-ary Pulse Position Modulation (PPM) Signaling

    Energy Technology Data Exchange (ETDEWEB)

    Mendez, A J; Gagliardi, R M; Hernandez, V J; Bennett, C V

    2008-07-11

    PPM is a signaling scheme that enables the transmission of multiple bits per symbol [1]. It has found favor in the regime of free space optical communications ('FSO' or 'Lasercom'); however, PPM has yet to be widely applied to fiber optic-based communications. Its limitation in fiber results from the exceedingly high bandwidth requirements needed to electronically process a directly detected pulse, especially as the symbol rate increases and the pulse width correspondingly decreases. As a solution, we introduced the concept of a virtual quadrant receiver for receiving 1.25 Gb/s 4-ary PPM, where photonic processing reduced the number of required electronic components [2]. In this paper, we extend these photonic process techniques to a 16-ary, 12.5 Gb/s (10 Gb/s plus 8B/10B line coding) PPM communications system for fiber optic avionics, wherein much of the receiver processing is enabled by techniques based on planar lightwave circuits (PLCs). The architecture is applicable to higher input data rates and M-ary PPM. In the following, we present the PPM encoding and decoding architectures and numerically simulated results.

  17. Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    Science.gov (United States)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

  18. 3D positioning scheme exploiting nano-scale IR-UWB orthogonal pulses

    Directory of Open Access Journals (Sweden)

    Kim Nammoon

    2011-01-01

    Full Text Available Abstract In these days, the development of positioning technology for realizing ubiquitous environments has become one of the most important issues. The Global Positioning System (GPS is a well-known positioning scheme, but it is not suitable for positioning in in-door/building environments because it is difficult to maintain line-of-sight condition between satellites and a GPS receiver. To such problem, various positioning methods such as RFID, WLAN, ZigBee, and Bluetooth have been developed for indoor positioning scheme. However, the majority of positioning schemes are focused on the two-dimension positioning even though three-dimension (3D positioning information is more useful especially in indoor applications, such as smart space, U-health service, context aware service, etc. In this paper, a 3D positioning system based on mutually orthogonal nano-scale impulse radio ultra-wideband (IR-UWB signals and cross array antenna is proposed. The proposed scheme uses nano-scale IR-UWB signals providing fine time resolution and high-resolution multiple signal specification algorithm for the time-of-arrival and the angle-of-arrival estimation. The performance is evaluated over various IEEE 802.15.4a channel models, and simulation results show the effectiveness of proposed scheme.

  19. 3D positioning scheme exploiting nano-scale IR-UWB orthogonal pulses.

    Science.gov (United States)

    Kim, Nammoon; Kim, Youngok

    2011-10-04

    In these days, the development of positioning technology for realizing ubiquitous environments has become one of the most important issues. The Global Positioning System (GPS) is a well-known positioning scheme, but it is not suitable for positioning in in-door/building environments because it is difficult to maintain line-of-sight condition between satellites and a GPS receiver. To such problem, various positioning methods such as RFID, WLAN, ZigBee, and Bluetooth have been developed for indoor positioning scheme. However, the majority of positioning schemes are focused on the two-dimension positioning even though three-dimension (3D) positioning information is more useful especially in indoor applications, such as smart space, U-health service, context aware service, etc. In this paper, a 3D positioning system based on mutually orthogonal nano-scale impulse radio ultra-wideband (IR-UWB) signals and cross array antenna is proposed. The proposed scheme uses nano-scale IR-UWB signals providing fine time resolution and high-resolution multiple signal specification algorithm for the time-of-arrival and the angle-of-arrival estimation. The performance is evaluated over various IEEE 802.15.4a channel models, and simulation results show the effectiveness of proposed scheme.

  20. A new design of pulsed laser diode driver system for multistate quantum key distribution

    Science.gov (United States)

    Abdullah, M. S.; Jamaludin, M. Z.; Witjaksono, G.; Mokhtar, M. H. H.

    2011-07-01

    In this paper, we describe a new design of laser diode driver system based on MOSFET current mirror and digital signal controller (DSC). The system is designed to emit stream pairs of photons from three semiconductor laser diodes. The DSC is able to switch between the three laser diodes at constant rate. The duty cycle is maintained at 1% in order to reduce its thermal effect and thus prolong the laser diodes' life cycles. The MOSFET current mirror circuits are capable of delivering constant modulation current with peak current up to 58 mA to each laser diode. This laser driver system will allow the generating biphotons automatically with qubit rate around 8-13% for μ less than or equal to 1, thus making it practical for six-states quantum key distribution implementation.

  1. Experimental observation of pulse delay and speed-up in cascaded quantum well gain and absorber media

    DEFF Research Database (Denmark)

    Hansen, Per Lunnemann; Poel, Mike van der; Yvind, Kresten

    2008-01-01

    Slow-down and speed-up of 180 fs pulses in semiconductor waveguides beyond the existing models is obseved. Cascaded gain and absorbing sections is shown to provide significant temporal pulse shifting at near constant output pulse energy.......Slow-down and speed-up of 180 fs pulses in semiconductor waveguides beyond the existing models is obseved. Cascaded gain and absorbing sections is shown to provide significant temporal pulse shifting at near constant output pulse energy....

  2. The effect of temperature on pulsed positive streamer discharges in air over the range 292 K–1438 K

    Science.gov (United States)

    Ono, Ryo; Ishikawa, Yuta

    2018-05-01

    The effect of temperature on pulsed positive streamer discharges in air is measured by comparing atmospheric-pressure, high-temperature discharges with low-pressure, room-temperature discharges at the same air densities n and discharge voltages. Both discharges have the same reduced electric field E/n, so the differences between the two discharges only depend on the temperature, which is varied from 292 K to 1438 K. Temperature affects the discharge pulse energy most significantly; at 1438 K, the energy of an atmospheric-pressure discharge pulse is approximately 30 times larger than that of the corresponding 20.5 kPa, room-temperature discharge. Temperature also affects the shapes of the streamers when K, but no significant effect is observed for K. There is also no significant temperature effect on the spatially integrated intensity of N2(C–B) emission. However, temperature strongly affects the ratio of the integrated emission intensity to the discharge energy. No effect of the temperature is observed on the propagation velocity of the primary streamer or on the length of the secondary streamer.

  3. Rapid temperature increase near the anode and cathode in the afterglow of a pulsed positive streamer discharge

    Science.gov (United States)

    Ono, Ryo

    2018-06-01

    The spatiotemporal evolution of the temperature in the afterglow of point-to-plane, pulsed positive streamer discharge was measured near the anode tip and cathode surface using laser-induced predissociation fluorescence of OH radicals. The temperature exhibited a rapid increase and displayed a steep spatial gradient after a discharge pulse. The rate of temperature rise reached 84 K μs‑1 at mm, where z represents the distance from the anode tip. The temperature rise was much faster than in the middle of the gap; it was only 2.8 K μs‑1 at mm. The temperature reached 1700 K near the anode tip at s and 1500 K near the cathode surface at s, where t represents the postdischarge time. The spatial gradient reached 1280 K mm‑1 near the anode tip at s. The mechanism responsible for the rapid temperature increase was discussed, including rapid heating of the gas in the early postdischarge phase (s), and vibration-to-translation energy transfer in the later postdischarge phase (s). The high temperatures near the anode tip and cathode surface are particularly important for the ignition of combustible mixtures and for surface treatments, including solid-surface treatments, water treatments, and plasma medicine using pulsed streamer discharges.

  4. The properties of Ge quantum rings deposited by pulsed laser deposition.

    Science.gov (United States)

    Ma, Xiying

    2010-07-01

    SiGe ring-shape nanostructures have attracted much research interest because of the interesting morphology, mechanical, and electromagnetic properties. In this paper, we present the planar Ge nanorings with well-defined sharp edges self-assembled on Si (100) matrix prepared with pulsed laser deposition (PLD) in the present of Ar gas. The transforming mechanism of the droplets is discussed, which a dynamic deformation model has been developed to simulate the self-transforming process of the droplets. The rings were found to be formed in two steps: from droplets to cones and from cones to rings via an elastic self-deforming process, which were likely to be driven by the lateral strain of Ge/Si layers and the surface tension.

  5. Tracing explosive in solvent using quantum cascade laser with pulsed electric discharge system

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seong-Wook; Tian, Chao; Martini, Rainer, E-mail: rmartini@stevens.edu [Department of Physics and Engineering Physics, Stevens Institute of Technology, 1 Castle Point on Hudson, Hoboken, New Jersey 07030 (United States); Chen, Gang [School of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China); Chen, I-chun Anderson [Newport Corporation/Oriel Instruments, 150 Long Beach Boulevard, Stratford, Connecticut 06615 (United States)

    2014-11-03

    We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N{sub 2}O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX.

  6. Tracing explosive in solvent using quantum cascade laser with pulsed electric discharge system

    International Nuclear Information System (INIS)

    Park, Seong-Wook; Tian, Chao; Martini, Rainer; Chen, Gang; Chen, I-chun Anderson

    2014-01-01

    We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N 2 O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX

  7. Extended space expectation values of position related operators for hydrogen-like quantum system evolutions

    International Nuclear Information System (INIS)

    Kalay, Berfin; Demiralp, Metin

    2014-01-01

    The expectation value definitions over an extended space from the considered Hilbert space of the system under consideration is given in another paper of the second author in this symposium. There, in that paper, the conceptuality rather than specification is emphasized on. This work uses that conceptuality to investigate the time evolutions of the position related operators' expectation values not in its standard meaning but rather in a new version of the definition over not the original Hilbert space but in the space obtained by extensions via introducing the images of the given initial wave packet under the positive integer powers of the system Hamiltonian. These images may not be residing in the same space of the initial wave packet when certain singularities appear in the structure of the system Hamiltonian. This may break down the existence of the integrals in the definitions of the expectation values. The cure is the use of basis functions in the abovementioned extended space and the sandwiching of the target operator whose expectation value is under questioning by an appropriately chosen operator guaranteeing the existence of the relevant integrals. Work specifically focuses on the hydrogen-like quantum systems whose Hamiltonians contain a polar singularity at the origin

  8. Positioning of self-assembled InAs quantum dots by focused ion beam implantation

    International Nuclear Information System (INIS)

    Mehta, M.

    2007-01-01

    Self-assembled quantum dots (QDs) are envisioned as building blocks for realization of novel nanoelectronic devices, for which the site-selective growth is highly desirable. This thesis presents a successful route toward selective positioning of self-assembled InAs QDs on patterned GaAs surface by combination of in situ focused ion beam (FIB) implantation and molecular beam epitaxy (MBE) technology. First, a buffer layer of GaAs was grown by MBE before a square array of holes with a pitch of 1-2 μm was fabricated by FIB implantation of Ga and In, ions respectively. Later, an in-situ annealing step followed by InAs deposition was performed. The InAs QDs were preferentially formed in the holes generated by FIB. The influence of ion dose, annealing parameters and InAs amount was investigated in this work. With optimized parameters, more than 50 % single dot occupancy per hole is achieved. Furthermore, the photoluminescence spectra from positioned QDs confirm their good optical quality. (orig.)

  9. Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng; Ikeda, Masao, E-mail: mikeda2013@sinano.ac.cn; Liu, Jianping; Zhang, Shuming [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Zhou, Kun; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Institute of Semiconductors (CAS), Beijing 100083 (China); Liu, Zongshun [Institute of Semiconductors (CAS), Beijing 100083 (China)

    2015-07-21

    Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells.

  10. Quantum

    CERN Document Server

    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.

  11. Instantaneous coherent destruction of tunneling and fast quantum state preparation for strongly pulsed spin qubits in diamond

    DEFF Research Database (Denmark)

    Wubs, Martijn

    2010-01-01

    Qubits driven by resonant strong pulses are studied and a parameter regime is explored in which the dynamics can be solved in closed form. Instantaneous coherent destruction of tunneling can be seen for longer pulses, whereas shorter pulses allow a fast preparation of the qubit state. Results...... are compared with recent experiments of pulsed nitrogen-vacancy center spin qubits in diamond....

  12. Creative scientific research international session of 2nd meeting on advanced pulsed-neutron research on quantum functions in nano-scale materials

    International Nuclear Information System (INIS)

    Itoh, Shinichi

    2005-06-01

    1 MW-class pulsed-neutron sources will be constructed in Japan, United State and United Kingdom in a few years. Now is the time for a challenge to innovate on neutron science and extend new science fields. Toward the new era, we develop new pulsed-neutron technologies as well as new neutron devices under the international collaborations with existing pulsed-neutron facilities, such as the UK-Japan collaboration program on neutron scattering. At the same time, the new era will bring international competitions to neutron researchers. We aim to create new neutron science toward the new pulsed-neutron era by introducing the new technologies developed here. For this purpose, we have started the research project, 'Advanced pulsed-neutron research on quantum functions in nano-scale materials,' in the duration between JFY2004 and JFY2008. The 2nd meeting of this project was held on 22-24 February 2005 to summarize activities in FY2004 and to propose research projects in the coming new fiscal year. In this international session as a part of this meeting, the scientific results and research plans on the UK-Japan collaboration program, the research plans on the collaboration between IPNS (Intense Pulsed Neutron Source, Argonne National Laboratory) and KENS (Neutron Science Laboratory, KEK), also the recent scientific results arisen form this project were presented. (author)

  13. Control of quantum paths of high-order harmonics and attosecond pulse generation in the presence of a static electric field

    International Nuclear Information System (INIS)

    Hong Weiyi; Lu Peixiang; Cao Wei; Lan Pengfei; Wang Xinlin

    2007-01-01

    The time-frequency properties of high-order harmonic generation in the presence of a static electric field are investigated. It is found that the quantum paths contributing to the harmonics can be controlled by adding a static electric field. The highest photon energies of harmonics emitted in the adjacent half-cycles of the laser field are modulated by the static electric field, and then an attosecond pulse train with one burst per optical cycle can be extracted. For the ratio between the laser and the static field of 0.39, the harmonic spectrum is extended to I p + 9.1U p , and the harmonics above I p + 0.7U p are emitted almost in phase. The phase-locked harmonics covered by a broad bandwidth are produced, and then a regular attosecond pulse train with a pulse duration of 80 as is generated

  14. Positivity, discontinuity, finite resources, and nonzero error for arbitrarily varying quantum channels

    International Nuclear Information System (INIS)

    Boche, H.; Nötzel, J.

    2014-01-01

    This work is motivated by a quite general question: Under which circumstances are the capacities of information transmission systems continuous? The research is explicitly carried out on finite arbitrarily varying quantum channels (AVQCs). We give an explicit example that answers the recent question whether the transmission of messages over AVQCs can benefit from assistance by distribution of randomness between the legitimate sender and receiver in the affirmative. The specific class of channels introduced in that example is then extended to show that the unassisted capacity does have discontinuity points, while it is known that the randomness-assisted capacity is always continuous in the channel. We characterize the discontinuity points and prove that the unassisted capacity is always continuous around its positivity points. After having established shared randomness as an important resource, we quantify the interplay between the distribution of finite amounts of randomness between the legitimate sender and receiver, the (nonzero) probability of a decoding error with respect to the average error criterion and the number of messages that can be sent over a finite number of channel uses. We relate our results to the entanglement transmission capacities of finite AVQCs, where the role of shared randomness is not yet well understood, and give a new sufficient criterion for the entanglement transmission capacity with randomness assistance to vanish

  15. Sub-diffraction positioning of a two-photon excited and optically trapped quantum dot

    DEFF Research Database (Denmark)

    Pedersen, Liselotte Jauffred; Kyrsting, Anders Højbo; Christensen, Eva Arnspang

    2014-01-01

    Colloidal quantum dots are luminescent long-lived probes that can be two-photon excited and manipulated by a single laser beam. Therefore, quantum dots can be used for simultaneous single molecule visualization and force manipulation using an infra-red laser. Here, we show that even a single opti...

  16. Two-photon absorption laser-induced fluorescence of atomic oxygen in the afterglow of pulsed positive corona discharge

    Science.gov (United States)

    Ono, Ryo; Takezawa, Kei; Oda, Tetsuji

    2009-08-01

    Atomic oxygen is measured in the afterglow of pulsed positive corona discharge using time-resolved two-photon absorption laser-induced fluorescence. The discharge occurs in a 14 mm point-to-plane gap in dry air. After the discharge pulse, the atomic oxygen density decreases at a rate of 5×104 s-1. Simultaneously, ozone density increases at almost the same rate, where the ozone density is measured using laser absorption method. This agreement between the increasing rate of atomic oxygen and decreasing rate of ozone proves that ozone is mainly produced by the well-known three-body reaction, O+O2+M→O3+M. No other process for ozone production such as O2(v)+O2→O3+O is observed. The spatial distribution of atomic oxygen density is in agreement with that of the secondary streamer luminous intensity. This agreement indicates that atomic oxygen is mainly produced in the secondary streamer channels, not in the primary streamer channels.

  17. Field-free molecular orientation induced by single-cycle THz pulses: the role of resonance and quantum interference

    DEFF Research Database (Denmark)

    Shu, Chuan-Cun; Henriksen, Niels Engholm

    2013-01-01

    distributions of the pulses at the rotational resonance frequencies play an important role. Furthermore, we investigate the interference between multiple rotational excitation pathways following prealignment with a nonresonant 800-nm femtosecond pulse. It is shown that such interference can lead...

  18. LDPC-coded MIMO optical communication over the atmospheric turbulence channel using Q-ary pulse-position modulation.

    Science.gov (United States)

    Djordjevic, Ivan B

    2007-08-06

    We describe a coded power-efficient transmission scheme based on repetition MIMO principle suitable for communication over the atmospheric turbulence channel, and determine its channel capacity. The proposed scheme employs the Q-ary pulse-position modulation. We further study how to approach the channel capacity limits using low-density parity-check (LDPC) codes. Component LDPC codes are designed using the concept of pairwise-balanced designs. Contrary to the several recent publications, bit-error rates and channel capacities are reported assuming non-ideal photodetection. The atmospheric turbulence channel is modeled using the Gamma-Gamma distribution function due to Al-Habash et al. Excellent bit-error rate performance improvement, over uncoded case, is found.

  19. Positive magnetoresistance in ferromagnetic Nd-doped In2O3 thin films grown by pulse laser deposition

    KAUST Repository

    Xing, G. Z.

    2014-05-23

    We report the magnetic and magnetotransport properties of (In 0.985Nd0.015)2O2.89 thin films grown by pulse laser deposition. The clear magnetization hysteresis loops with the complementary magnetic domain structure reveal the intrinsic room temperature ferromagnetism in the as-prepared films. The strong sp-f exchange interaction as a result of the rare earth doping is discussed as the origin of the magnetotransport behaviours. A positive magnetoresistance (∼29.2%) was observed at 5 K and ascribed to the strong ferromagnetic sp-f exchange interaction in (In0.985Nd0.015)2O 2.89 thin films due to a large Zeeman splitting in an external magnetic field of 50 KOe. © 2014 AIP Publishing LLC.

  20. ''Positive'' and ''negative'' electric-pulse-induced reversible resistance switching effect in Pr0.7Ca0.3MnO3 films

    International Nuclear Information System (INIS)

    Wang, Q.; Chen, L.D.; Li, X.M.; Shang, D.S.; Wu, Z.H.

    2007-01-01

    ''Negative'' electric-pulse-induced reversible resistance (EPIR) switching phenomenon was found in In/PCMO/Pt sandwich, in which the high resistance can be written with positive voltage pulses, and the low resistance can be reset using negative voltage pulses (the positive voltage direction is defined as going from the top electrode to the bottom electrode). This is just the opposite from the ''positive'' EPIR effect in Ag/PCMO/Pt sandwich, in which the high resistance can be written only with negative voltage pulses, and the low resistance can be reset using positive voltage pulses. The I-V hysteresis curves of In/PCMO/Pt and Ag/PCMO/Pt sandwiches also show opposite directions, i.e., counterclockwise and clockwise under a negative voltage region for indium and Ag electrode systems, respectively. C-V characteristics show that the barrier does not exist in Ag/PCMO/Pt sandwich, while In/PCMO/Pt sandwich exhibits an obvious Schottky-like barrier. We suggest that in the negative EPIR behavior in In/PCMO/Pt structure, the resistance states are mainly controlled changing the Schottky-like barrier at the interface with the weak effect of carrier trapping process, while the positive EPIR behavior in Ag/PCMO/Pt sandwich mainly depends on the carrier trapping process at the interface. (orig.)

  1. Super-resolution with a positive epsilon multi-quantum-well super-lens

    International Nuclear Information System (INIS)

    Bak, A. O.; Giannini, V.; Maier, S. A.; Phillips, C. C.

    2013-01-01

    We design an anisotropic and dichroic quantum metamaterial that is able to achieve super-resolution without the need for a negative permittivity. When exploring the parameters of the structure, we take into account the limits of semiconductor fabrication technology based on quantum well stacks. By heavily doping the structure with free electrons, we infer an anisotropic effective medium with a prolate ellipsoid dispersion curve which allows for near-diffractionless propagation of light (similar to an epsilon-near-zero hyperbolic lens). This, coupled with low absorption, allows us to resolve images at the sub-wavelength scale at distances 6 times greater than equivalent natural materials

  2. Noise-driven diamagnetic susceptibility of impurity doped quantum dots: Role of anisotropy, position-dependent effective mass and position-dependent dielectric screening function

    International Nuclear Information System (INIS)

    Bera, Aindrila; Saha, Surajit; Ganguly, Jayanta; Ghosh, Manas

    2016-01-01

    Highlights: • Diamagnetic susceptibility (DMS) of doped quantum dot is studied. • The dot is subjected to Gaussian white noise. • Role of anisotropy, PDEM and PDDSF have been analyzed. • Noise amplifies and suppresses DMS depending on particular condition. • Findings bear significant technological importance. - Abstract: We explore Diamagnetic susceptibility (DMS) of impurity doped quantum dot (QD) in presence of Gaussian white noise introduced to the system additively and multiplicatively. In view of this profiles of DMS have been pursued with variations of geometrical anisotropy and dopant location. We have invoked position-dependent effective mass (PDEM) and position-dependent dielectric screening function (PDDSF) of the system. Presence of noise sometimes suppresses and sometimes amplifies DMS from that of noise-free condition and the extent of suppression/amplification depends on mode of application of noise. It is important to mention that the said suppression/amplification exhibits subtle dependence on use of PDEM, PDDSF and geometrical anisotropy. The study reveals that DMS, or more fundamentally, the effective confinement of LDSS, can be tuned by appropriate mingling of geometrical anisotropy/effective mass/dielectric constant of the system with noise and also on the pathway of application of latter.

  3. Silica coating of PbS quantum dots and their position control using a nanohole on Si substrate

    Science.gov (United States)

    Mukai, Kohki; Okumura, Isao; Nishizaki, Yuta; Yamashita, Shuzo; Niwa, Keisuke

    2018-04-01

    We succeeded in controlling the apparent size of a colloidal PbS quantum dot (QD) in the range of 20 to 140 nm by coating with silica and trapping the coated QDs in a nanohole prepared by scanning probe microscope lithography. Photoluminescence intensity was improved by controlling the process of adding the silica source material of tetraethoxysilane for the coating. Nanoholes of different sizes were formed on a single substrate by scanning probe oxidation with the combination of SF6 dry etching and KOH wet etching. QDs having an arbitrary energy structure can be arranged at an arbitrary position on the semiconductor substrate using this technique, which will aid in the fabrication of future nanosize solid devices such as quantum information circuits.

  4. Calculus of the Power Spectral Density of Ultra Wide Band Pulse Position Modulation Signals Coded with Totally Flipped Code

    Directory of Open Access Journals (Sweden)

    DURNEA, T. N.

    2009-02-01

    Full Text Available UWB-PPM systems were noted to have a power spectral density (p.s.d. consisting of a continuous portion and a line spectrum, which is composed of energy components placed at discrete frequencies. These components are the major source of interference to narrowband systems operating in the same frequency interval and deny harmless coexistence of UWB-PPM and narrowband systems. A new code denoted as Totally Flipped Code (TFC is applied to them in order to eliminate these discrete spectral components. The coded signal transports the information inside pulse position and will have the amplitude coded to generate a continuous p.s.d. We have designed the code and calculated the power spectral density of the coded signals. The power spectrum has no discrete components and its envelope is largely flat inside the bandwidth with a maximum at its center and a null at D.C. These characteristics make this code suited for implementation in the UWB systems based on PPM-type modulation as it assures a continuous spectrum and keeps PPM modulation performances.

  5. Observation of bulk-ion heating in a tokamak plasma by application of positive and negative current pulses in TRIAM-1

    Energy Technology Data Exchange (ETDEWEB)

    Toi, K; Hiraki, N; Nakamura, K; Mitarai, O; Kawai, Y; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1980-09-01

    A positive of negative current pulse induced by a pulsed toroidal electric field much higher than the Dreicer field increases the bulk-ion temperature of the plasma centre two to three times, without macroscopic plasma destruction. The decay time of the raised ion temperature agrees well with the prediction from neoclassical transport theory. The magnitude of the positive current pulse is limited by violent current disruption, and that of the negative current by a lack of MHD equilibrium which is due to a marked reduction of the total plasma current. The relevant current-driven instabilities in the turbulent heating of a tokamak plasma, skin heating and inward transfer of the energy deposition in the skin layer are briefly discussed.

  6. Macroscopic quantum systems and gravitational phenomena

    International Nuclear Information System (INIS)

    Pikovski, I.

    2014-01-01

    Low-energy quantum systems are studied theoretically in light of possible experiments to test the interplay between quantum theory and general relativity. The research focus in this thesis is on quantum systems which can be controlled with very high precision and which allow for tests of quantum theory at novel scales in terms of mass and size. The pulsed regime of opto-mechanics is explored and it is shown how short optical pulses can be used to prepare and characterize quantum states of a massive mechanical resonator, and how some phenomenological models of quantum gravity can be probed. In addition, quantum interferometry with photons and matter-waves in the presence of gravitational time dilation is considered. It is shown that time dilation causes entanglement between internal states and the center-of-mass position and that it leads to decoherence of all composite quantum systems. The results of the thesis show that the interplay between quantum theory and general relativity affects even low-energy quantum systems and that it offers novel phenomena which can be probed in experiments. (author) [de

  7. Localization of s-Wave and Quantum Effective Potential of a Quasi-free Particle with Position-Dependent Mass

    International Nuclear Information System (INIS)

    Ju Guoxing; Xiang Yang; Ren Zhongzhou

    2006-01-01

    The properties of the s-wave for a quasi-free particle with position-dependent mass (PDM) have been discussed in details. Differed from the system with constant mass in which the localization of the s-wave for the free quantum particle around the origin only occurs in two dimensions, the quasi-free particle with PDM can experience attractive forces in D dimensions except D = 1 when its mass function satisfies some conditions. The effective mass of a particle varying with its position can induce effective interaction, which may be attractive in some cases. The analytical expressions of the eigenfunctions and the corresponding probability densities for the s-waves of the two- and three-dimensional systems with a special PDM are given, and the existences of localization around the origin for these systems are shown.

  8. A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform

    International Nuclear Information System (INIS)

    Sheu, Yae-lin; Hsu, Liang-Yan; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I

    2014-01-01

    This study introduces a new adaptive time-frequency (TF) analysis technique, the synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an ab initio level, upon which we have demonstrated its versatility as a new viable venue for further exploring quantum dynamics. For a signal composed of oscillatory components which can be characterized by instantaneous frequency, the SST enables rendering the decomposed signal based on the phase information inherited in the linear TF representation with mathematical support. Compared with the classical type of TF methods, the SST clearly depicts several intrinsic quantum dynamical processes such as selection rules, AC Stark effects, and high harmonic generation

  9. Optimal quantum control of Bose-Einstein condensates in magnetic microtraps: Comparison of gradient-ascent-pulse-engineering and Krotov optimization schemes

    Science.gov (United States)

    Jäger, Georg; Reich, Daniel M.; Goerz, Michael H.; Koch, Christiane P.; Hohenester, Ulrich

    2014-09-01

    We study optimal quantum control of the dynamics of trapped Bose-Einstein condensates: The targets are to split a condensate, residing initially in a single well, into a double well, without inducing excitation, and to excite a condensate from the ground state to the first-excited state of a single well. The condensate is described in the mean-field approximation of the Gross-Pitaevskii equation. We compare two optimization approaches in terms of their performance and ease of use; namely, gradient-ascent pulse engineering (GRAPE) and Krotov's method. Both approaches are derived from the variational principle but differ in the way the control is updated, additional costs are accounted for, and second-order-derivative information can be included. We find that GRAPE produces smoother control fields and works in a black-box manner, whereas Krotov with a suitably chosen step-size parameter converges faster but can produce sharp features in the control fields.

  10. Ultrafast dynamics of laser-pulse excited semiconductors: non-Markovian quantum kinetic equations with nonequilibrium correlations

    Directory of Open Access Journals (Sweden)

    V.V.Ignatyuk

    2004-01-01

    Full Text Available Non-Markovian kinetic equations in the second Born approximation are derived for a two-zone semiconductor excited by a short laser pulse. Both collision dynamics and running nonequilibrium correlations are taken into consideration. The energy balance and relaxation of the system to equilibrium are discussed. Results of numerical solution of the kinetic equations for carriers and phonons are presented.

  11. Ergodic channel capacity of spatial correlated multiple-input multiple-output free space optical links using multipulse pulse-position modulation

    Science.gov (United States)

    Wang, Huiqin; Wang, Xue; Cao, Minghua

    2017-02-01

    The spatial correlation extensively exists in the multiple-input multiple-output (MIMO) free space optical (FSO) communication systems due to the channel fading and the antenna space limitation. Wilkinson's method was utilized to investigate the impact of spatial correlation on the MIMO FSO communication system employing multipulse pulse-position modulation. Simulation results show that the existence of spatial correlation reduces the ergodic channel capacity, and the reception diversity is more competent to resist this kind of performance degradation.

  12. Entanglement in SU(2)-invariant quantum systems: The positive partial transpose criterion and others

    International Nuclear Information System (INIS)

    Schliemann, John

    2005-01-01

    We study entanglement in mixed bipartite quantum states which are invariant under simultaneous SU(2) transformations in both subsystems. Previous results on the behavior of such states under partial transposition are substantially extended. The spectrum of the partial transpose of a given SU(2)-invariant density matrix ρ is entirely determined by the diagonal elements of ρ in a basis of tensor-product states of both spins with respect to a common quantization axis. We construct a set of operators which act as entanglement witnesses on SU(2)-invariant states. A sufficient criterion for ρ having a negative partial transpose is derived in terms of a simple spin correlator. The same condition is a necessary criterion for the partial transpose to have the maximum number of negative eigenvalues. Moreover, we derive a series of sum rules which uniquely determine the eigenvalues of the partial transpose in terms of a system of linear equations. Finally we compare our findings with other entanglement criteria including the reduction criterion, the majorization criterion, and the recently proposed local uncertainty relations

  13. Quantum systems with position-dependent mass and spin-orbit interaction via Rashba and Dresselhaus terms

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Alexandre G. M., E-mail: agmschmidt@gmail.com; Portugal, L., E-mail: liciniolportugal@gmail.com; Jesus, Anderson L. de [Departamento de Física do polo universitário de Volta Redonda, Instituto de Ciências Exatas—Universidade Federal Fluminense, R. Des. Ellis Hermydio Figueira, 783, Volta Redonda, RJ CEP 27215-350 (Brazil)

    2015-01-15

    We consider a particle with spin 1/2 with position-dependent mass moving in a plane. Considering separately Rashba and Dresselhaus spin-orbit interactions, we write down the Hamiltonian for this problem and solve it for Dirichlet boundary conditions. Our radial wavefunctions have two contributions: homogeneous ones which are written as Bessel functions of non-integer orders—that depend on angular momentum m—and particular solutions which are obtained after decoupling the non-homogeneous system. In this process, we find non-homogeneous Bessel equation, Laguerre, as well as biconfluent Heun equation. We also present the probability densities for m = 0, 1, 2 in an annular quantum well. Our results indicate that the background as well as the spin-orbit interaction naturally splits the spinor components.

  14. Quantum systems with position-dependent mass and spin-orbit interaction via Rashba and Dresselhaus terms

    International Nuclear Information System (INIS)

    Schmidt, Alexandre G. M.; Portugal, L.; Jesus, Anderson L. de

    2015-01-01

    We consider a particle with spin 1/2 with position-dependent mass moving in a plane. Considering separately Rashba and Dresselhaus spin-orbit interactions, we write down the Hamiltonian for this problem and solve it for Dirichlet boundary conditions. Our radial wavefunctions have two contributions: homogeneous ones which are written as Bessel functions of non-integer orders—that depend on angular momentum m—and particular solutions which are obtained after decoupling the non-homogeneous system. In this process, we find non-homogeneous Bessel equation, Laguerre, as well as biconfluent Heun equation. We also present the probability densities for m = 0, 1, 2 in an annular quantum well. Our results indicate that the background as well as the spin-orbit interaction naturally splits the spinor components

  15. Clinical Benefit of Allogeneic Melanoma Cell Lysate-Pulsed Autologous Dendritic Cell Vaccine in MAGE-Positive Colorectal Cancer Patients

    DEFF Research Database (Denmark)

    Toh, Han Chong; Wang, Who-Whong; Chia, Whay Kuang

    2009-01-01

    PURPOSE: We evaluated the clinical benefit of an allogeneic melanoma cell lysate (MCL)-pulsed autologous dendritic cell (DC) vaccine in advanced colorectal cancer patients expressing at least one of six MAGE-A antigens overexpressed by the cell line source of the lysate. EXPERIMENTAL DESIGN: DCs...... were cultured from peripheral blood mononuclear cells (PBMC), pulsed with the allogeneic MCL, and matured using cytokines that achieved high CD83- and CCR7-expressing DCs. Each patient received up to 10 intradermal vaccinations (3-5 x 10(6) cells per dose) at biweekly intervals. RESULTS: Twenty......-free for >27 and >37 months, respectively. This result is particularly meaningful as all patients had progressive disease before treatment. Overall, DC vaccination was associated with a serial decline in regulatory T cells. Using an antibody array, we characterized plasma protein profiles in responding...

  16. The Use of Ultrashort Picosecond Laser Pulses to Generate Quantum Optical Properties of Single Molecules in Biophysics

    Science.gov (United States)

    Ly, Sonny

    Generation of quantum optical states from ultrashort laser-molecule interactions have led to fascinating discoveries in physics and chemistry. In recent years, these interactions have been extended to probe phenomena in single molecule biophysics. Photons emitted from a single fluorescent molecule contains important properties about how the molecule behave and function in that particular environment. Analysis of the second order coherence function through fluorescence correlation spectroscopy plays a pivotal role in quantum optics. At very short nanosecond timescales, the coherence function predicts photon antibunching, a purely quantum optical phenomena which states that a single molecule can only emit one photon at a time. Photon antibunching is the only direct proof of single molecule emission. From the nanosecond to microsecond timescale, the coherence function gives information about rotational diffusion coefficients, and at longer millisecond timescales, gives information regarding the translational diffusion coefficients. In addition, energy transfer between molecules from dipole-dipole interaction results in FRET, a highly sensitive method to probe conformational dynamics at nanometer distances. Here I apply the quantum optical techniques of photon antibunching, fluorescence correlation spectroscopy and FRET to probe how lipid nanodiscs form and function at the single molecule level. Lipid nanodiscs are particles that contain two apolipoprotein (apo) A-I circumventing a lipid bilayer in a belt conformation. From a technological point of view, nanodiscs mimics a patch of cell membrane that have recently been used to reconstitute a variety of membrane proteins including cytochrome P450 and bacteriorhodopsin. They are also potential drug transport vehicles due to its small and stable 10nm diameter size. Biologically, nanodiscs resemble to high degree, high density lipoproteins (HDL) in our body and provides a model platform to study lipid-protein interactions

  17. The positive action conjecture and asymptotically euclidean metrics in quantum gravity

    International Nuclear Information System (INIS)

    Gibbons, G.W.; Pope, C.N.

    1979-01-01

    The positive action conjecture requires that the action of any asymptotically Euclidean 4-dimensional Riemannian metric be positive, vanishing if and only if the space is flat. Because any Ricci flat, asymptotically Euclidean metric has zero action and is local extremum of the action which is a local minimum at flat space, the conjecture requires that there are no Ricci flat asymptotically Euclidean metrics other than flat space, which would establish that flat space is the only local minimum. We prove this for metrics on R 4 and a large class of more complicated topologies and for self-dual metrics. We show that if Rsupμsubμ >= 0 there are no bound states of the Dirac equation and discuss the relevance to possible baryon non-conserving processes mediated by gravitational instantons. We conclude that these are forbidden in the lowest stationary phase approximation. We give a detailed discussion of instantons invariant under an SU(2) or SO(3) isometry group. We find all regular solutions, none of which is asymptotically Euclidean and all of which possess a further Killing vector. In an appendix we construct an approximate self-dual metric on K3 - the only simply connected compact manifold which admits a self-dual metric. (orig.) [de

  18. Quantum information entropies for position-dependent mass Schrödinger problem

    Energy Technology Data Exchange (ETDEWEB)

    Yañez-Navarro, G. [Departamento de Física, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Edificio 9, UPALM, Mexico D. F. 07738 (Mexico); Sun, Guo-Hua, E-mail: sunghdb@yahoo.com [Centro Universitario Valle de Chalco, Universidad Autónoma del Estado de México, Valle de Chalco Solidaridad, Estado de México, 56615 (Mexico); Dytrych, T., E-mail: tdytrych@gmail.com [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Launey, K.D., E-mail: kristina@baton.phys.lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Dong, Shi-Hai, E-mail: dongsh2@yahoo.com [Departamento de Física, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Edificio 9, UPALM, Mexico D. F. 07738 (Mexico); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Draayer, J.P., E-mail: draayer@sura.org [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)

    2014-09-15

    The Shannon entropy for the position-dependent Schrödinger equation for a particle with a nonuniform solitonic mass density is evaluated in the case of a trivial null potential. The position S{sub x} and momentum S{sub p} information entropies for the three lowest-lying states are calculated. In particular, for these states, we are able to derive analytical solutions for the S{sub x} entropy as well as for the Fourier transformed wave functions, while the S{sub p} quantity is calculated numerically. We notice the behavior of the S{sub x} entropy, namely, it decreases as the mass barrier width narrows and becomes negative beyond a particular width. The negative Shannon entropy exists for the probability densities that are highly localized. The mass barrier determines the stability of the system. The dependence of S{sub p} on the width is contrary to the one for S{sub x}. Some interesting features of the information entropy densities ρ{sub s}(x) and ρ{sub s}(p) are demonstrated. In addition, the Bialynicki-Birula–Mycielski (BBM) inequality is tested for a number of states and found to hold for all the cases.

  19. Quantum information entropies for position-dependent mass Schrödinger problem

    International Nuclear Information System (INIS)

    Yañez-Navarro, G.; Sun, Guo-Hua; Dytrych, T.; Launey, K.D.; Dong, Shi-Hai; Draayer, J.P.

    2014-01-01

    The Shannon entropy for the position-dependent Schrödinger equation for a particle with a nonuniform solitonic mass density is evaluated in the case of a trivial null potential. The position S x and momentum S p information entropies for the three lowest-lying states are calculated. In particular, for these states, we are able to derive analytical solutions for the S x entropy as well as for the Fourier transformed wave functions, while the S p quantity is calculated numerically. We notice the behavior of the S x entropy, namely, it decreases as the mass barrier width narrows and becomes negative beyond a particular width. The negative Shannon entropy exists for the probability densities that are highly localized. The mass barrier determines the stability of the system. The dependence of S p on the width is contrary to the one for S x . Some interesting features of the information entropy densities ρ s (x) and ρ s (p) are demonstrated. In addition, the Bialynicki-Birula–Mycielski (BBM) inequality is tested for a number of states and found to hold for all the cases

  20. Pulsed laser induced optical nonlinearities in undoped, copper doped and chromium doped CdS quantum dots

    Science.gov (United States)

    Sharma, Dimple; Malik, B. P.; Gaur, Arun

    2015-04-01

    Quantum dots (QDs) of CdS, Cu doped and Cr doped CdS were synthesized through chemical co- precipitation method. The synthesized QDs have been characterized by x-ray diffraction, ultraviolet visible absorption spectroscopy. The diameters of QDs were calculated using Debye-Scherrer’s formula and Brus equation. They are found to be in 3.5-3.8 nm range. The nonlinear properties has been studied by the open and closed aperture Z-scan technique using frequency double Nd:YAG laser. The nonlinear refractive index (n2), nonlinear absorption coefficient (β), third order nonlinear susceptibilities (χ3) of QDs has been calculated. It has been found that the values of nonlinear parameters are higher for doped QDs than undoped CdS QDs. Hence they can be regarded as potential material for the development of optoelectronics and photonics devices.

  1. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    Ultrashort Laser Pulse Phenomena, 2e serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond (""faster than electronics"") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic

  2. Fabrication of carbon quantum dots with nano-defined position and pattern in one step via sugar-electron-beam writing.

    Science.gov (United States)

    Weng, Yuyan; Li, Zhiyun; Peng, Lun; Zhang, Weidong; Chen, Gaojian

    2017-12-14

    Quantum dots (QDs) are promising materials in nanophotonics, biological imaging, and even quantum computing. Precise positioning and patterning of QDs is a prerequisite for realizing their actual applications. Contrary to the traditional two discrete steps of fabricating and positioning QDs, herein, a novel sugar-electron-beam writing (SEW) method is reported for producing QDs via electron-beam lithography (EBL) that uses a carefully chosen synthetic resist, poly(2-(methacrylamido)glucopyranose) (PMAG). Carbon QDs (CQDs) could be fabricated in situ through electron beam exposure, and the nanoscale position and luminescence intensity of the produced CQDs could be precisely controlled without the assistance of any other fluorescent matter. We have demonstrated that upon combining an electron beam with a glycopolymer, in situ production of CQDs occurs at the electron beam spot center with nanoscale precision at any place and with any patterns, an advancement that we believe will stimulate innovations in future applications.

  3. Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS).

    Science.gov (United States)

    Hardin, Robert A; Liu, Yun; Long, Cary; Aleksandrov, Alexander; Blokland, Willem

    2011-02-14

    A high peak-power Q-switched laser has been used to monitor the ion beam profiles in the superconducting linac at the Spallation Neutron Source (SNS). The laser beam suffers from position drift due to movement, vibration, or thermal effects on the optical components in the 250-meter long laser beam transport line. We have designed, bench-tested, and implemented a beam position stabilization system by using an Ethernet CMOS camera, computer image processing and analysis, and a piezo-driven mirror platform. The system can respond at frequencies up to 30 Hz with a high position detection accuracy. With the beam stabilization system, we have achieved a laser beam pointing stability within a range of 2 μrad (horizontal) to 4 μrad (vertical), corresponding to beam drifts of only 0.5 mm × 1 mm at the furthest measurement station located 250 meters away from the light source.

  4. A Comparative Study on Pulse Sinusoidal High Frequency Voltage Injection and INFORM Methods for PMSM Position Sensorless Control

    DEFF Research Database (Denmark)

    Ni, Ronggang; Lu, Kaiyuan; Blaabjerg, Frede

    2016-01-01

    and Indirect Flux detection by On-line Reactance Measurement (INFORM) method in the α-β reference frame. Implementation methods are deliberated in detail and the position estimation error caused by magnetic field distorsion is also discussed. Experiments using a commercial PMSM are carried out...

  5. Positive magnetoresistance in ferromagnetic Nd-doped In2O3 thin films grown by pulse laser deposition

    KAUST Repository

    Xing, G. Z.; Yi, J. B.; Yan, F.; Wu, Tao; Li, S.

    2014-01-01

    temperature ferromagnetism in the as-prepared films. The strong sp-f exchange interaction as a result of the rare earth doping is discussed as the origin of the magnetotransport behaviours. A positive magnetoresistance (∼29.2%) was observed at 5 K and ascribed

  6. Usefulness of pulse-wave doppler tissue sampling and dobutamine stress echocardiography for identification of false positive inferior wall defects in SPECT

    International Nuclear Information System (INIS)

    Altinmakas, S.; Dagdeviren, B.; Turkmen, M.; Gursurer, M.; Say, B.; Tezel, T.; Ersek, B.

    2000-01-01

    False positive inferior wall perfusion defects restrict the accuracy of SPECT in diagnosis of coronary artery disease (CAD). Pulse-Wave Tissue Doppler (PWTD) has been recently proposed to assess regional wall motion velocities. The objectives of this study were to evaluate the presence of CAD by using PWTD during dobutamine stress echocardiography (DSE) in patients with an inferior perfusion defect detected by SPECT and compare PWTD parameters of normal cases with patients who had inferior perfusion defect and CAD. Sixty-five patients (mean age 58±8 years, 30 men) with a normal LV systolic function at rest according to echocardiographic evaluation with an inferior ischemia determined by SPECT and a control group (CG) of 34 normal cases (mean age 56±7 years, 16 men) were included in this study. All patients underwent a standard DSE (up to 40 μg/kg/min with additional atropine during sub-maximum heart rate responses). Pulse-wave Doppler tissue sampling of inferior wall was performed in the apical 2-chamber view at rest and stress. The coronary angiography was performed within 24 hours. The results were evaluated for the prediction of significant right coronary artery (RCA) and/or left circumflex coronary artery (CX) with narrowing (≥50% diameter stenosis, assessed by quantitative coronary angiography). It was observed that the peak stress mean E/A ratio was lower in patients with CAD when compared to patients without CAD (0.78±0.2 versus 1.29±0.11 p<0.0001). Also the peak stress E/A ratio of normal cases was significantly higher than patients who had CAD (1.19±0.3 versus 0.78±0.2 p<0.0001). When the cut off point for the E/A ratio was determined as 1, the sensitivity and specificity of dobutamine stress PWTD E/A were 89% and 86%, respectively. The peak stress E/A ratio was higher than 1 in all patients with a false positive perfusion defect. Systolic S velocity increase during DSE was significantly lower in patients with CAD (54%±17 versus 99%±24 p=0

  7. Effect of pulse sequence parameter selection on signal strength in positive-contrast MRI markers for MRI-based prostate postimplant assessment

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Tze Yee [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, Texas 77030 (United States); Kudchadker, Rajat J., E-mail: rkudchad@mdanderson.org; Wang, Jihong; Ibbott, Geoffrey S. [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Stafford, R. Jason [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); MacLellan, Christopher [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, Texas 77030 (United States); Rao, Arvind [Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Frank, Steven J. [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)

    2016-07-15

    Purpose: For postimplant dosimetric assessment, computed tomography (CT) is commonly used to identify prostate brachytherapy seeds, at the expense of accurate anatomical contouring. Magnetic resonance imaging (MRI) is superior to CT for anatomical delineation, but identification of the negative-contrast seeds is challenging. Positive-contrast MRI markers were proposed to replace spacers to assist seed localization on MRI images. Visualization of these markers under varying scan parameters was investigated. Methods: To simulate a clinical scenario, a prostate phantom was implanted with 66 markers and 86 seeds, and imaged on a 3.0T MRI scanner using a 3D fast radiofrequency-spoiled gradient recalled echo acquisition with various combinations of scan parameters. Scan parameters, including flip angle, number of excitations, bandwidth, field-of-view, slice thickness, and encoding steps were systematically varied to study their effects on signal, noise, scan time, image resolution, and artifacts. Results: The effects of pulse sequence parameter selection on the marker signal strength and image noise were characterized. The authors also examined the tradeoff between signal-to-noise ratio, scan time, and image artifacts, such as the wraparound artifact, susceptibility artifact, chemical shift artifact, and partial volume averaging artifact. Given reasonable scan time and managable artifacts, the authors recommended scan parameter combinations that can provide robust visualization of the MRI markers. Conclusions: The recommended MRI pulse sequence protocol allows for consistent visualization of the markers to assist seed localization, potentially enabling MRI-only prostate postimplant dosimetry.

  8. Synchronized Pulsed dc - dc Converter as Maximum Power Position Tracker with Wide Load and Insolation Variation for Stand Alone PV System

    International Nuclear Information System (INIS)

    Hardik, P. Desai; Ranjan Maheshwari

    2011-01-01

    This paper investigates the interest focused on employing parallel connected dc-dc converter with high tracking effectiveness under wide variation in environmental conditions (Insolation) and wide load variation. dc-dc converter is an essential part of the stand alone PV system. Paper also presents an approach on how duty cycle for maximum power position (MPP) is adjusted by taking care of varying load conditions and without iterative steps. Synchronized PWM pulses are employed for the converter. High tracking efficiency is achieved with continuous input and inductor current. In this approach, the converter can he utilized in buck as well in boost mode. The PV system simulation was verified and experimental results were in agreement to the presented scheme. (authors)

  9. The impact of arm position and pulse pressure on the validation of a wrist-cuff blood pressure measurement device in a high risk population

    Directory of Open Access Journals (Sweden)

    Ali Reza Khoshdel

    2010-03-01

    Full Text Available Ali Reza Khoshdel1,2, Shane Carney2, Alastair Gillies21Faculty of Medicine, Aja University of Medical Science, Tehran, Iran; 2John Hunter Hospital, Faculty of Health, The University of Newcastle, Newcastle, NS W, AustraliaAbstract: Despite the increasing popularity of blood pressure (BP wrist monitors for self-BP measurement at home, device validation and the effect of arm position remains an issue. This study focused on the validation of the Omron HEM-609 wrist BP device, including an evaluation of the impact of arm position and pulse pressure on BP measurement validation. Fifty patients at high risk for cardiovascular disease were selected (age 65 ± 10 years. Each patient had two measurements with a mercury sphygmomanometer and three measurements with the wrist BP device (wrist at the heart level while the horizontal arm supported [HORIZONTAL], hand supported on the opposite shoulder [SHOULDER], and elbow placed on a desk [DESK], in random order. The achieved systolic BP (SBP and diastolic BP (DBP wrist-cuff readings were compared to the mercury device and the frequencies of the readings within 5, 10, and 15 mmHg of the gold standard were computed and compared with the British Hypertension Society (BHS and Association for the Advancement of Medical Instrumentation (AAMI protocols. The results showed while SBP readings with HORIZONTAL and SHOULDER positions were significantly different from the mercury device (mean difference = 7.1 and 13.3 mmHg, respectively; P < 0.05, the DESK position created the closest reading to mercury (mean difference = 3.8, P > 0.1. Approximately 71% of SBP readings with the DESK position were within ±10 mmHg, whereas it was 62.5% and 34% for HORIZONTAL and SHOULDER positions, respectively. Wrist DBP attained category D with BHS criteria with all three arm positions. Bland–Altman plots illustrated that the wrist monitor systematically underestimated SBP and DBP values. However a reading adjustment of 5 and 10 mm

  10. 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

  11. Quantum Integers

    International Nuclear Information System (INIS)

    Khrennikov, Andrei; Klein, Moshe; Mor, Tal

    2010-01-01

    In number theory, a partition of a positive integer n is a way of writing n as a sum of positive integers. The number of partitions of n is given by the partition function p(n). Inspired by quantum information processing, we extend the concept of partitions in number theory as follows: for an integer n, we treat each partition as a basis state of a quantum system representing that number n, so that the Hilbert-space that corresponds to that integer n is of dimension p(n); the 'classical integer' n can thus be generalized into a (pure) quantum state ||ψ(n) > which is a superposition of the partitions of n, in the same way that a quantum bit (qubit) is a generalization of a classical bit. More generally, ρ(n) is a density matrix in that same Hilbert-space (a probability distribution over pure states). Inspired by the notion of quantum numbers in quantum theory (such as in Bohr's model of the atom), we then try to go beyond the partitions, by defining (via recursion) the notion of 'sub-partitions' in number theory. Combining the two notions mentioned above, sub-partitions and quantum integers, we finally provide an alternative definition of the quantum integers [the pure-state |ψ'(n)> and the mixed-state ρ'(n),] this time using the sub-partitions as the basis states instead of the partitions, for describing the quantum number that corresponds to the integer n.

  12. Lectures on pulsed NMR

    International Nuclear Information System (INIS)

    Pines, A.

    1988-08-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs

  13. Lectures on pulsed NMR

    International Nuclear Information System (INIS)

    Pines, A.

    1986-09-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs

  14. 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

  15. Scalable optical quantum computer

    Energy Technology Data Exchange (ETDEWEB)

    Manykin, E A; Mel' nichenko, E V [Institute for Superconductivity and Solid-State Physics, Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)

    2014-12-31

    A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr{sup 3+}, regularly located in the lattice of the orthosilicate (Y{sub 2}SiO{sub 5}) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)

  16. Scalable optical quantum computer

    International Nuclear Information System (INIS)

    Manykin, E A; Mel'nichenko, E V

    2014-01-01

    A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr 3+ , regularly located in the lattice of the orthosilicate (Y 2 SiO 5 ) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)

  17. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Pulsed formation and readout of dynamic holograms in a photorefractive GaAs:Cr crystal

    Science.gov (United States)

    Andreeva, N. P.; Barashkov, M. S.; Bel'dyugin, Igor'M.; Kruzhilin, Yu I.; Petnikova, V. M.; Umnov, A. F.; Kharchenko, M. A.; Shuvalov, Vladimir V.

    1989-12-01

    An experimental investigation was made of the energy (diffraction efficiency) and time (formation, storage, readout) parameters of four-wave mixing in GaAs:Cr. An investigation of the dynamics of the leading edge of a nonlinear response pulse could become an effective method for pulsed spectroscopy of photorefractive materials.

  18. Ionization of Rydberg atoms by the kicks of half-cycle pulses

    Indian Academy of Sciences (India)

    Rydberg atom; half-cycle pulses; ionization; quantum mechanical model. ... packet which represents a non-stationary quantum state formed by coherent ...... Wetzels, Impulsive interactions of half cycle pulse radiation with Rydberg atoms, Ph.D.

  19. Quantum communication with photons

    International Nuclear Information System (INIS)

    Tittel, W.

    2005-01-01

    Full text: The discovery that transmission of information encoded into single quantum systems enables new forms of communication let to the emergence of the domain of quantum communication. During the last ten years, various key experiments based on photons as carrier of the quantum information have been realized. Today, quantum cryptography systems based on faint laser pulses can be purchased commercially, bi-partite entanglement has been distributed over long distances and has been used for quantum key distribution, and quantum purification, teleportation and entanglement swapping have been demonstrated. I will give a general introduction into this fascinating field and will review experimental achievements in the domain of quantum communication with discrete two-level quantum systems (qubits) encoded into photons. (author)

  20. p-Adic quantum mechanics

    International Nuclear Information System (INIS)

    Vladimirov, V.S.; Volovich, I.V.

    1988-01-01

    Quantum mechanics above the field of p-adic numbers is constructed. Three formulations of p-adic quantum mechanics are considered: 1) quantum mechanics with complex-valued wave functions and p-adic coordinates and pulses; an approach based on Weyl representation is suggested; 2) the probability (Euclidean) formulation; 3) the secondary quantization representation (Fock representation) with p-adic wave functions

  1. Experiments for possible hydroacoustic discrimination of free-swimming juvenile gadoid fish by analysis of broadband pulse spectra as well as 3D fish position form video images and split beam acoustics

    DEFF Research Database (Denmark)

    Lundgren, Bo; Nielsen, J. Rasmus

    2002-01-01

    , alignment of acoustic and optical-reference frames, and automatic position-fitting of fish models to manually marked fix-points on fish images. The software also performs Fourier spectrum analysis and pulse-shape analysis of broad-bandwidth echoes. Therefore, several measurement series on free...

  2. Quantum Nonlinear Optics

    CERN Document Server

    Hanamura, Eiichi; Yamanaka, Akio

    2007-01-01

    This graduate-level textbook gives an introductory overview of the fundamentals of quantum nonlinear optics. Based on the quantum theory of radiation, Quantum Nonlinear Optics incorporates the exciting developments in novel nonlinear responses of materials (plus laser oscillation and superradiance) developed over the past decade. It deals with the organization of radiation field, interaction between electronic system and radiation field, statistics of light, mutual manipulation of light and matter, laser oscillation, dynamics of light, nonlinear optical response, and nonlinear spectroscopy, as well as ultrashort and ultrastrong laser pulse. Also considered are Q-switching, mode locking and pulse compression. Experimental and theoretical aspects are intertwined throughout.

  3. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Dynamics of splashing of molten metals during irradiation with single CO2 laser pulses

    Science.gov (United States)

    Arutyunyan, R. V.; Baranov, V. Yu; Bol'shov, Leonid A.; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1988-03-01

    An experimental investigation was made of the dynamics of the loss of the melt as a result of interaction with single-mode CO2 laser radiation pulses of 5-35 μs duration. The dynamics of splashing of the melt during irradiation with short pulses characterized by a Gaussian intensity distribution differed from that predicted by models in which the distribution of the vapor pressure was assumed to be radially homogeneous.

  4. Adjacent effect on positive charge transfer from radical cation of n-dodecane to scavenger studied by supbicosecond pulse radiolysis, statistical and Monte Carlo approach

    International Nuclear Information System (INIS)

    Saeki, A.; Tagawa, S.; Kozawa, T.; Yoshida, Y.

    2003-01-01

    Time-dependent behaviors of radical cation in n-dodecane in the presence of high-concentrated cation scavenger triethylamine were measured by subpicosecond pulse radiolysis system. The significant reduction of the initial yield in the optical density was observed. This reduction were not able to be explained by the first order rate constant. Therefore, we assumed that this phenomena occur due to the adjacent effect of the solute molecules. We approached this effect by the statistical model and configurational-bias Monte Carlo method. In both methods, we supposed a condition that the cation site in the radical cation is delocalized and will be scavenged rapidly within the time resolution if the solute molecules is adjacent to any sites of the solvent. In addition to the adjacent effect, the fact that a large part of the solvent molecules is excluded by the solute molecules especially at high concentration was taken into consideration. First, we formulated this effect by a statistical model. In addition to the above assumption, this model is based on the following assumption; the effects of molecule's shape, conformation and interaction among molecules were ignored and the aggregation of the solute molecules were treated randomly. As a result, the formula indicated good agreement with the experimental data. Second, as another approach, we adopted the configurational-bias Monte Carlo simulation to reproduce the liquid system. The OLPS model was used to describe the intermolecular and intramolecular potentials. The adjacent effect estimated by this method corresponded to the experimental data with a threshold of 0.5 nm. This value are close to a typical reaction radius. The average number of adjacent solvent molecules and the distribution of aggregated solute's number were also collected from the position data

  5. Contributions of an adiabatic initial inversion pulse and K-space Re-ordered by inversion-time at each slice position (KRISP) to control of CSF artifacts and visualization of the brain in FLAIR magnetic resonance imaging

    International Nuclear Information System (INIS)

    Curati, Walter L.; Oatridge, Angela; Herlihy, Amy H.; Hajnal, Joseph V.; Puri, Basant K.; Bydder, Graeme M.

    2001-01-01

    AIM: The aim of this study was to compare the performance of three fluid attenuated inversion recovery (FLAIR) pulse sequences for control of cerebrospinal fluid (CSF) and blood flow artifacts in imaging of the brain. The first of these sequences had an initial sinc inversion pulse which was followed by conventional k-space mapping. The second had an initial sinc inversion pulse followed by k-space re-ordered by inversion time at each slice position (KRISP) and the third had an adiabatic initial inversion pulse followed by KRISP. MATERIALS AND METHODS: Ten patients with established disease were studied with all three pulse sequences. Seven were also studied with the adiabatic KRISP sequence after contrast enhancement. Their images were evaluated for patient motion artifact, CSF and blood flow artifact as well as conspicuity of the cortex, meninges, ventricular system, brainstem and cerebellum. The conspicuity of lesions and the degree of enhancement were also evaluated. RESULTS: Both the sinc and adiabatic KRISP FLAIR sequences showed better control of CSF and blood flow artifacts than the conventional FLAIR sequence. In addition the adiabatic KRISP FLAIR sequence showed better control of CSF artifact at the inferior aspect of the posterior fossa. The lesion conspicuity was similar for each of the FLAIR sequences as was the degree of contrast enhancement to that shown with a T 1 weighted spin echo sequence. CONCLUSION: The KRISP FLAIR sequence controls high signal artifacts from CSF flow and blood flow and the adiabatic pulse controls high signal artifacts due to inadequate inversion of the CSF magnetization at the periphery of the head transmitter coil. The KRISP FLAIR sequence also improves cortical and meningeal definition as a result of an edge enhancement effect. The effects are synergistic and can be usefully combined in a single pulse sequence. Curati, W.L. et al. (2001)

  6. Quantum size correction to the work function and the centroid of excess charge in positively ionized simple metal clusters

    Directory of Open Access Journals (Sweden)

    M. Payami

    2003-12-01

    Full Text Available  In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct position of the centroid of excess charge in positively charged simple metal clusters with different values . For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes in the framework of local spin-density approximation and stabilized jellium model (SJM as well as simple jellium model (JM with rigid jellium. Secondly, we have fitted our results to the asymptotic ionization formulas both with and without the size correction to the work function. The results of fittings show that the formula containing the size correction predict a correct position of the centroid inside the jellium while the other predicts a false position, outside the jellium sphere.

  7. Quantum size correction to the work function and centroid of excess charge in positively ionized simple metal clusters

    International Nuclear Information System (INIS)

    Payami, M.

    2004-01-01

    In this work, we have shown the important role of the finite-size correction to the work function in predicting the correct position of the centroid of excess charge in positively charged simple metal clusters with different r s values (2≤ r s ≥ 7). For this purpose, firstly we have calculated the self-consistent Kohn-Sham energies of neutral and singly-ionized clusters with sizes 2≤ N ≥100 in the framework of local spin-density approximation and stabilized jellium model as well as simple jellium model with rigid jellium. Secondly, we have fitted our results to the asymptotic ionization formulas both with and without the size correction to the work function. The results of fittings show that the formula containing the size correction predict a correct position of the centroid inside the jellium while the other predicts a false position, outside the jellium sphere

  8. Pulse Generator

    Science.gov (United States)

    Greer, Lawrence (Inventor)

    2017-01-01

    An apparatus and a computer-implemented method for generating pulses synchronized to a rising edge of a tachometer signal from rotating machinery are disclosed. For example, in one embodiment, a pulse state machine may be configured to generate a plurality of pulses, and a period state machine may be configured to determine a period for each of the plurality of pulses.

  9. Deterministic self-organization: Ordered positioning of InAs quantum dots by self-organized anisotropic strain engineering on patterned GaAs(311)B

    International Nuclear Information System (INIS)

    Selcuk, E.; Hamhuis, G.J.; Noetzel, R.

    2009-01-01

    Laterally ordered InGaAs quantum dot (QD) arrays, InAs QD molecules, and single InAs QDs in a spot-like periodic arrangement are created by self-organized anisotropic strain engineering of InGaAs/GaAs superlattice (SL) templates on planar GaAs (311)B substrates in molecular beam epitaxy. On shallow- and deep-patterned substrates the respectively generated steps and facets guide the self-organization process during SL template formation to create more complex ordering such as periodic stripes, depending on pattern design. Here we demonstrate for patterns such as shallow- and deepetched round holes and deep-etched zigzag mesas that the self-organized periodic arrangement of QD molecules and single QDs is spatially locked to the pattern sidewalls and corners. This extends the concept of guided self-organization to deterministic self-organization. Absolute position control of the QDs is achieved without one-to-one pattern definition. This guarantees the excellent arrangement control of the ordered QD molecules and single QDs with strong photoluminescence emission up to room temperature, which is required for future quantum functional devices. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Femtosecond pulse shaping using the geometric phase.

    Science.gov (United States)

    Gökce, Bilal; Li, Yanming; Escuti, Michael J; Gundogdu, Kenan

    2014-03-15

    We demonstrate a femtosecond pulse shaper that utilizes polarization gratings to manipulate the geometric phase of an optical pulse. This unique approach enables circular polarization-dependent shaping of femtosecond pulses. As a result, it is possible to create coherent pulse pairs with orthogonal polarizations in a 4f pulse shaper setup, something until now that, to our knowledge, was only achieved via much more complex configurations. This approach could be used to greatly simplify and enhance the functionality of multidimensional spectroscopy and coherent control experiments, in which multiple coherent pulses are used to manipulate quantum states in materials of interest.

  11. Broadband Near-Infrared Quantum Cutting in Metal-Ion Codoped Y3Al5O12 Thin Films Grown by Pulsed-Laser Deposition for Solar Cell Application

    Directory of Open Access Journals (Sweden)

    Mei Kwan Lau

    2013-01-01

    Full Text Available We have deposited thin films of yttrium aluminum garnet (YAG doped with Ce3+ and Yb3+ on quartz and silicon substrates by pulsed laser deposition. Near-infrared (NIR quantum cutting which involves the emission of NIR photons through the downconversion from Ce3+ to Yb3+ is realized. Upon the broadband excitation of Ce3+ ions with a visible photon at the peak wavelength of 450 nm, NIR photons are generated by Yb3+ ions, with an emission wavelength centered at 1030 nm. The luminescent decay curves of Ce3+ were recorded as a supporting evidence corresponding to the energy transfer. This work offers a better and more convenient approach compatible with crystalline silicon solar cell compared to conventional bulk phosphors.

  12. Finite and profinite quantum systems

    CERN Document Server

    Vourdas, Apostolos

    2017-01-01

    This monograph provides an introduction to finite quantum systems, a field at the interface between quantum information and number theory, with applications in quantum computation and condensed matter physics. The first major part of this monograph studies the so-called `qubits' and `qudits', systems with periodic finite lattice as position space. It also discusses the so-called mutually unbiased bases, which have applications in quantum information and quantum cryptography. Quantum logic and its applications to quantum gates is also studied. The second part studies finite quantum systems, where the position takes values in a Galois field. This combines quantum mechanics with Galois theory. The third part extends the discussion to quantum systems with variables in profinite groups, considering the limit where the dimension of the system becomes very large. It uses the concepts of inverse and direct limit and studies quantum mechanics on p-adic numbers. Applications of the formalism include quantum optics and ...

  13. Quantum Criticality

    Science.gov (United States)

    Drummond, P. D.; Chaturvedi, S.; Dechoum, K.; Comey, J.

    2001-02-01

    We investigate the theory of quantum fluctuations in non-equilibrium systems having large crit­ical fluctuations. This allows us to treat the limits imposed by nonlinearities to quantum squeezing and noise reduction, and also to envisage future tests of quantum theory in regions of macroscopic quantum fluctuations. A long-term objective of this research is to identify suitable physical sys­tems in which macroscopic 'Schrödinger cat'-like behaviour may be observed. We investigate two systems in particular of much current experimental interest, namely the degenerate parametric oscillator near threshold, and the evaporatively cooled (BEC). We compare the results obtained in the positive-P representation, as a fully quantum mechanical calculation, with the truncated Wigner phase space equation, also known as semi-classical theory. We show when these results agree and differ in calculations taken beyond the linearized approximation. In the region where the largest quantum fluctuations and Schrödinger cat-like behaviour might be expected, we find that the quantum predictions correspond very closely to the semi-classical theory. Nature abhors observing a Schrödinger cat. -Pacs: 03.65.Bz

  14. Dynamic pulse difference circuit

    International Nuclear Information System (INIS)

    Erickson, G.L.

    1978-01-01

    A digital electronic circuit of especial use for subtracting background activity pulses in gamma spectrometry is disclosed which comprises an up-down counter connected to count up with signal-channel pulses and to count down with background-channel pulses. A detector responsive to the count position of the up-down counter provides a signal when the up-down counter has completed one scaling sequence cycle of counts in the up direction. In an alternate embodiment, a detector responsive to the count position of the up-down counter provides a signal upon overflow of the counter

  15. Quantum optics

    National Research Council Canada - National Science Library

    Agarwal, G. S

    2013-01-01

    .... Focusing on applications of quantum optics, the textbook covers recent developments such as engineering of quantum states, quantum optics on a chip, nano-mechanical mirrors, quantum entanglement...

  16. Quantum electrodynamics

    International Nuclear Information System (INIS)

    Akhiezer, A.I.

    1983-01-01

    Basic ideas of quantum electrodynamics history of its origination and its importance are outlined. It is shown low the notion of the field for each kind of particles and the notion of vacuum for such field had originated and been affirmed how a new language of the Feynman diagrams had appeared without which it is quite impossible to described complex processes of particle scattering and mutual transformation. The main problem of the quantum electrodynamics is to find a scattering matrix, which solution comes to the determination of the Green electrodynamic functions. A review is given of papers on clarifying the asymptotic behaviour of the Green electrodynamic functions in the range of high pulses, on studying the Compton effect, bremsstrahlung irradiation Raman light scattering elastic scattering during channeling of charged particles in a crystal

  17. Maximally incompatible quantum observables

    Energy Technology Data Exchange (ETDEWEB)

    Heinosaari, Teiko, E-mail: teiko.heinosaari@utu.fi [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Schultz, Jussi, E-mail: jussi.schultz@gmail.com [Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Toigo, Alessandro, E-mail: alessandro.toigo@polimi.it [Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Via Celoria 16, I-20133 Milano (Italy); Ziman, Mario, E-mail: ziman@savba.sk [RCQI, Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 84511 Bratislava (Slovakia); Faculty of Informatics, Masaryk University, Botanická 68a, 60200 Brno (Czech Republic)

    2014-05-01

    The existence of maximally incompatible quantum observables in the sense of a minimal joint measurability region is investigated. Employing the universal quantum cloning device it is argued that only infinite dimensional quantum systems can accommodate maximal incompatibility. It is then shown that two of the most common pairs of complementary observables (position and momentum; number and phase) are maximally incompatible.

  18. Maximally incompatible quantum observables

    International Nuclear Information System (INIS)

    Heinosaari, Teiko; Schultz, Jussi; Toigo, Alessandro; Ziman, Mario

    2014-01-01

    The existence of maximally incompatible quantum observables in the sense of a minimal joint measurability region is investigated. Employing the universal quantum cloning device it is argued that only infinite dimensional quantum systems can accommodate maximal incompatibility. It is then shown that two of the most common pairs of complementary observables (position and momentum; number and phase) are maximally incompatible.

  19. Quantum minigolf

    Energy Technology Data Exchange (ETDEWEB)

    Reinhard, Friedemann [Universitaet Stuttgart (Germany). 3. Physikalisches Institut

    2010-07-01

    Quantum minigolf is a virtual-reality computer game visualizing quantum mechanics. The rules are the same as for the classical game minigolf, the goal being to kick a ball such that it crosses an obstacle course and runs into a hole. The ball, however, follows the laws of quantum mechanics: It can be at several places at once or tunnel through obstacles. To know whether the ball has reached the goal, the player has to perform a position measurement, which converts the ball into a classical object and fixes its position. But quantum mechanics is indeterministic: There is always a chance to lose, even for Tiger Woods. Technically, the obstacle course and the ball are projected onto the floor by a video projector. The position of the club is tracked by an infrared marker, similar as in Nintendo's Wii console. The whole setup is portable and the software has been published under the GPL license on www.quantum-minigolf.org.

  20. Quantum thermodynamics of general quantum processes.

    Science.gov (United States)

    Binder, Felix; Vinjanampathy, Sai; Modi, Kavan; Goold, John

    2015-03-01

    Accurately describing work extraction from a quantum system is a central objective for the extension of thermodynamics to individual quantum systems. The concepts of work and heat are surprisingly subtle when generalizations are made to arbitrary quantum states. We formulate an operational thermodynamics suitable for application to an open quantum system undergoing quantum evolution under a general quantum process by which we mean a completely positive and trace-preserving map. We derive an operational first law of thermodynamics for such processes and show consistency with the second law. We show that heat, from the first law, is positive when the input state of the map majorizes the output state. Moreover, the change in entropy is also positive for the same majorization condition. This makes a strong connection between the two operational laws of thermodynamics.

  1. Optical properties of Germanium nanoparticles synthesized by pulsed laser ablation in acetone

    Directory of Open Access Journals (Sweden)

    Saikiran eVadavalli

    2014-10-01

    Full Text Available Germanium (Ge nanoparticles (NPs are synthesized by means of pulsed laser ablation of bulk germanium target immersed in acetone with ns laser pulses at different pulse energies. The fabricated NPs are characterized by employing different techniques such as UV-visible absorption spectroscopy, photoluminescence, micro-Raman spectroscopy, transmission electron microscopy (TEM and field emission scanning electron microscopy (FESEM. The mean size of the Ge NPs is found to vary from few nm to 40 nm with the increase in laser pulse energy. Shift in the position of the absorption spectra is observed and also the photoluminescence peak shift is observed due to quantum confinement effects. High resolution TEM combined with micro-Raman spectroscopy confirms the crystalline nature of the generated germanium nanoparticles. The formation of various sizes of germanium NPs at different laser pulse energies is evident from the asymmetry in the Raman spectra and the shift in its peak position towards the lower wavenumber side. The FESEM micrographs confirm the formation of germanium micro/nanostructures at the laser ablated position of the bulk germanium. In particular, the measured NP sizes from the micro-Raman phonon quantum confinement model are found in good agreement with TEM measurements of Ge NPs.

  2. Quantum solitons

    Energy Technology Data Exchange (ETDEWEB)

    Abram, I [Centre National d' Etudes des Telecommunications (CNET), 196 Avenue Henri Ravera, F-92220 Bagneux (France)

    1999-02-01

    Two of the most remarkable properties of light - squeezing and solitons - are being combined in a new generation of experiments that could revolutionize optics and communications. One area of application concerns the transmission and processing of classical (binary) information, in which the presence or absence of a soliton in a time-window corresponds to a ''1'' or ''0'', as in traditional optical-fibre communications. However, since solitons occur at fixed power levels, we do not have the luxury of being able to crank up the input power to improve the signal-to-noise ratio at the receiving end. Nevertheless, the exploitation of quantum effects such as squeezing could help to reduce noise and improve fidelity. In long-distance communications, where the signal is amplified every 50-100 kilometres or so, the soliton pulse is strongest just after the amplifier. Luckily this is where the bulk of the nonlinear interaction needed to maintain the soliton shape occurs. However, the pulse gets weaker as it propagates along the fibre, so the nonlinear interaction also becomes weakerand weaker. This means that dispersive effects become dominant until the next stage of amplification, where the nonlinearity takes over again. One problem is that quantum fluctuations in the amplifiers lead to random jumps in the central wavelength of the individual solitons, and this results in a random variation of the speed of individual solitons in the fibre. Several schemes have been devised to remove this excess noise and bring the train of solitons back to the orderly behaviour characteristic of a stable coherent state (e.g. the solitons could be passed through a spectral filter). Photon-number squeezing could also play a key role in solving this problem. For example, if the solitons are number-squeezed immediately after amplification, there will be a smaller uncertainty in the nonlinearity that keeps the soliton in shape and, therefore, there will also be less noise in the soliton. This

  3. FT-IR measurements of NH3 in the 1.5 μm region: line positions, intensities and their quantum assignments

    Science.gov (United States)

    Sung, K.; Brown, L. R.; Huang, X.; Schwenke, D. W.; Lee, T. J.

    2011-12-01

    As part of an effort to provide a complete set of spectroscopic line parameters of NH3 in the 1.5 μm region, we have analyzed the laboratory spectra recorded at various temperatures (200 - 299 K) with the McMath-Pierce Fourier transform spectrometer (FTS) on Kitt Peak Observatory in Arizona. The integrated sum of observed line strengths is measured to be 4.7×10-19 cm/molecule in the 6300 - 7000 cm-1 region. In this poster, we present line positions and strengths for the lines from four strong bands (2v1, 2v3, v1+v3, v1+2v4 and v3+2v4), which contribute more than 65% of opacity in the region. Lower state energies and quantum assignments determined by constructing combination differences are also presented. A theoretical IR linelist (X. Huang, D. W. Schwenke, and T. J. Lee. J. Chem. Phys., 134, 044320/044321, 2011) built upon the recent HSL-2 potential energy surface (nonadiabatic corrections included) is complementarily used for the quantum assignments. This work will support spectroscopic studies of atmospheres of outer planets, low mass brown dwarfs, and possibly extrasolar planets, in the 1.5 μm region (the H-band), where ammonia is one of significant opacity sources. (Research described in this talk was performed at Jet Propulsion Laboratory, California Institute of Technology, and was supported by the Planetary Atmospheric Research Program under the National Aeronautics and Space Administration. The AMES group acknowledges support from the NASA APRA & Herschel GO Program, and X.H. acknowledges the support by NASA/SETI Institute Co-operative Agreement.)

  4. Autocompensating quantum cryptography

    International Nuclear Information System (INIS)

    Bethune, Donald S.; Risk, William P.

    2002-01-01

    Quantum cryptographic key distribution (QKD) uses extremely faint light pulses to carry quantum information between two parties (Alice and Bob), allowing them to generate a shared, secret cryptographic key. Autocompensating QKD systems automatically and passively compensate for uncontrolled time-dependent variations of the optical fibre properties by coding the information as a differential phase between orthogonally polarized components of a light pulse sent on a round trip through the fibre, reflected at mid-course using a Faraday mirror. We have built a prototype system based on standard telecom technology that achieves a privacy-amplified bit generation rate of ∼1000 bits s -1 over a 10 km optical fibre link. Quantum cryptography is an example of an application that, by using quantum states of individual particles to represent information, accomplishes a practical task that is impossible using classical means. (author)

  5. Quantum quincunx in cavity quantum electrodynamics

    International Nuclear Information System (INIS)

    Sanders, Barry C.; Bartlett, Stephen D.; Tregenna, Ben; Knight, Peter L.

    2003-01-01

    We introduce the quantum quincunx, which physically demonstrates the quantum walk and is analogous to Galton's quincunx for demonstrating the random walk by employing gravity to draw pellets through pegs on a board, thereby yielding a binomial distribution of final peg locations. In contradistinction to the theoretical studies of quantum walks over orthogonal lattice states, we introduce quantum walks over nonorthogonal lattice states (specifically, coherent states on a circle) to demonstrate that the key features of a quantum walk are observable albeit for strict parameter ranges. A quantum quincunx may be realized with current cavity quantum electrodynamics capabilities, and precise control over decoherence in such experiments allows a remarkable decrease in the position noise, or spread, with increasing decoherence

  6. Pulsed atomic soliton laser

    International Nuclear Information System (INIS)

    Carr, L.D.; Brand, J.

    2004-01-01

    It is shown that simultaneously changing the scattering length of an elongated, harmonically trapped Bose-Einstein condensate from positive to negative and inverting the axial portion of the trap, so that it becomes expulsive, results in a train of self-coherent solitonic pulses. Each pulse is itself a nondispersive attractive Bose-Einstein condensate that rapidly self-cools. The axial trap functions as a waveguide. The solitons can be made robustly stable with the right choice of trap geometry, number of atoms, and interaction strength. Theoretical and numerical evidence suggests that such a pulsed atomic soliton laser can be made in present experiments

  7. Development of high resolution Michelson interferometer for stable phase-locked ultrashort pulse pair generation.

    Science.gov (United States)

    Okada, Takumi; Komori, Kazuhiro; Goshima, Keishiro; Yamauchi, Shohgo; Morohashi, Isao; Sugaya, Takeyoshi; Ogura, Mutsuo; Tsurumachi, Noriaki

    2008-10-01

    We developed a high resolution Michelson interferometer with a two-frequency He-Ne laser positioning system in order to stabilize the relative phase of a pulse pair. The control resolution corresponded to a 12 as time resolution or a phase of 1.5 degrees at 900 nm. This high resolution Michelson interferometer can generate a phase-locked pulse pair either with a specific relative phase such as 0 or pi radians or with an arbitrary phase. Coherent control of an InAs self-assembled quantum dot was demonstrated using the high resolution Michelson interferometer with a microspectroscopy system.

  8. Intensity stabilisation of optical pulse sequences for coherent control of laser-driven qubits

    Science.gov (United States)

    Thom, Joseph; Yuen, Ben; Wilpers, Guido; Riis, Erling; Sinclair, Alastair G.

    2018-05-01

    We demonstrate a system for intensity stabilisation of optical pulse sequences used in laser-driven quantum control of trapped ions. Intensity instability is minimised by active stabilisation of the power (over a dynamic range of > 104) and position of the focused beam at the ion. The fractional Allan deviations in power were found to be logic gates to be below 10^{-6} per gate.

  9. Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Bergbauer, W; Strassburg, M; Koelper, Ch; Linder, N [Osram Opto Semiconductors GmbH, Leibnizstrasse 4, D-93055 Regensburg (Germany); Roder, C; Laehnemann, J; Trampert, A [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Fuendling, S; Li, S F; Wehmann, H-H; Waag, A, E-mail: werner.bergbauer@osram-os.com [Institut fuer Halbleitertechnik, TU Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig (Germany)

    2010-07-30

    We demonstrate the fabrication of N-face GaN nanorods by metal organic vapour phase epitaxy (MOVPE), using continuous-flux conditions. This is in contrast to other approaches reported so far, which have been based on growth modes far off the conventional growth regimes. For position control of nanorods an SiO{sub 2} masking layer with a dense hole pattern on a c-plane sapphire substrate was used. Nanorods with InGaN/GaN heterostructures have been grown catalyst-free. High growth rates up to 25 {mu}m h{sup -1} were observed and a well-adjusted carrier gas mixture between hydrogen and nitrogen enabled homogeneous nanorod diameters down to 220 nm with aspect ratios of approximately 8:1. The structural quality and defect progression within nanorods were determined by transmission electron microscopy (TEM). Different emission energies for InGaN quantum wells (QWs) could be assigned to different side facets by room temperature cathodoluminescence (CL) measurements.

  10. Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells

    Science.gov (United States)

    Bergbauer, W.; Strassburg, M.; Kölper, Ch; Linder, N.; Roder, C.; Lähnemann, J.; Trampert, A.; Fündling, S.; Li, S. F.; Wehmann, H.-H.; Waag, A.

    2010-07-01

    We demonstrate the fabrication of N-face GaN nanorods by metal organic vapour phase epitaxy (MOVPE), using continuous-flux conditions. This is in contrast to other approaches reported so far, which have been based on growth modes far off the conventional growth regimes. For position control of nanorods an SiO2 masking layer with a dense hole pattern on a c-plane sapphire substrate was used. Nanorods with InGaN/GaN heterostructures have been grown catalyst-free. High growth rates up to 25 µm h - 1 were observed and a well-adjusted carrier gas mixture between hydrogen and nitrogen enabled homogeneous nanorod diameters down to 220 nm with aspect ratios of approximately 8:1. The structural quality and defect progression within nanorods were determined by transmission electron microscopy (TEM). Different emission energies for InGaN quantum wells (QWs) could be assigned to different side facets by room temperature cathodoluminescence (CL) measurements.

  11. Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells

    International Nuclear Information System (INIS)

    Bergbauer, W; Strassburg, M; Koelper, Ch; Linder, N; Roder, C; Laehnemann, J; Trampert, A; Fuendling, S; Li, S F; Wehmann, H-H; Waag, A

    2010-01-01

    We demonstrate the fabrication of N-face GaN nanorods by metal organic vapour phase epitaxy (MOVPE), using continuous-flux conditions. This is in contrast to other approaches reported so far, which have been based on growth modes far off the conventional growth regimes. For position control of nanorods an SiO 2 masking layer with a dense hole pattern on a c-plane sapphire substrate was used. Nanorods with InGaN/GaN heterostructures have been grown catalyst-free. High growth rates up to 25 μm h -1 were observed and a well-adjusted carrier gas mixture between hydrogen and nitrogen enabled homogeneous nanorod diameters down to 220 nm with aspect ratios of approximately 8:1. The structural quality and defect progression within nanorods were determined by transmission electron microscopy (TEM). Different emission energies for InGaN quantum wells (QWs) could be assigned to different side facets by room temperature cathodoluminescence (CL) measurements.

  12. Quantum Erasure: Quantum Interference Revisited

    OpenAIRE

    Walborn, Stephen P.; Cunha, Marcelo O. Terra; Pádua, Sebastião; Monken, Carlos H.

    2005-01-01

    Recent experiments in quantum optics have shed light on the foundations of quantum physics. Quantum erasers - modified quantum interference experiments - show that quantum entanglement is responsible for the complementarity principle.

  13. Quantum kinetic theory

    CERN Document Server

    Bonitz, Michael

    2016-01-01

    This book presents quantum kinetic theory in a comprehensive way. The focus is on density operator methods and on non-equilibrium Green functions. The theory allows to rigorously treat nonequilibrium dynamics in quantum many-body systems. Of particular interest are ultrafast processes in plasmas, condensed matter and trapped atoms that are stimulated by rapidly developing experiments with short pulse lasers and free electron lasers. To describe these experiments theoretically, the most powerful approach is given by non-Markovian quantum kinetic equations that are discussed in detail, including computational aspects.

  14. Sensitive measurement of nonlinear absorption and optical limiting in undoped and Fe-doped ZnO quantum dots using pulsed laser

    Science.gov (United States)

    Sharma, D.; Malik, B. P.; Gaur, A.

    2016-11-01

    Zinc oxide quantum dots (QDs) with Fe-doping at different concentrations were prepared by chemical co-precipitation method. The prepared QDs were characterized by UV-Vis spectroscopy, X-ray diffraction and Z-scan technique. The sizes of QDs were found to be within 4.6-6.6 nm range. The nonlinear parameters viz. two-photon absorption coefficient (βTPA) and two-photon absorption cross-section (σTPA) were extracted with the help of open aperture Z-scan technique using nanosecond Nd:YAG laser operating at wavelength 532 nm. Higher values of βTPA and σTPA for Fe doped ZnO implied that they were potential materials for development of photonics devices and sensor protection applications. Fe doped sample (3 % by wt) was found to be the best optical limiter with limiting threshold intensity of 0.64 TW/cm2.

  15. Maximally causal quantum mechanics

    International Nuclear Information System (INIS)

    Roy, S.M.

    1998-01-01

    We present a new causal quantum mechanics in one and two dimensions developed recently at TIFR by this author and V. Singh. In this theory both position and momentum for a system point have Hamiltonian evolution in such a way that the ensemble of system points leads to position and momentum probability densities agreeing exactly with ordinary quantum mechanics. (author)

  16. Phase-space quantum control

    International Nuclear Information System (INIS)

    Fechner, Susanne

    2008-01-01

    The von Neumann-representation introduced in this thesis describes each laser pulse in a one-to-one manner as a sum of bandwidth-limited, Gaussian laser pulses centered around different points in phase space. These pulses can be regarded as elementary building blocks from which every single laser pulse can be constructed. The von Neumann-representation combines different useful properties for applications in quantum control. First, it is a one-to-one map between the degrees of freedom of the pulse shaper and the phase-space representation of the corresponding shaped laser pulse. In other words: Every possible choice of pulse shaper parameters corresponds to exactly one von Neumann-representation and vice versa. Moreover, since temporal and spectral structures become immediately sizable, the von Neumann-representation, as well as the Husimi- or the Wigner-representations, allows for an intuitive interpretation of the represented laser pulse. (orig.)

  17. Quantum operations: technical or fundamental challenge?

    International Nuclear Information System (INIS)

    Mielnik, Bogdan

    2013-01-01

    A class of unitary operations generated by idealized, semiclassical fields is studied. The operations implemented by sharp potential kicks are revisited and the possibility of performing them by softly varying external fields is examined. The possibility of using the ion traps as ‘operation factories’ transforming quantum states is discussed. The non-perturbative algorithms indicate that the results of abstract δ-pulses of oscillator potentials can become real. Some of them, if empirically achieved, could be essential to examine certain atypical quantum ideas. In particular, simple dynamical manipulations might contribute to the Aharonov–Bohm criticism of the time–energy uncertainty principle, while some others may verify the existence of fundamental precision limits of the position measurements or the reality of ‘non-commutative geometries’. (paper)

  18. Quantum capacity of quantum black holes

    Science.gov (United States)

    Adami, Chris; Bradler, Kamil

    2014-03-01

    The fate of quantum entanglement interacting with a black hole has been an enduring mystery, not the least because standard curved space field theory does not address the interaction of black holes with matter. We discuss an effective Hamiltonian of matter interacting with a black hole that has a precise analogue in quantum optics and correctly reproduces both spontaneous and stimulated Hawking radiation with grey-body factors. We calculate the quantum capacity of this channel in the limit of perfect absorption, as well as in the limit of a perfectly reflecting black hole (a white hole). We find that the white hole is an optimal quantum cloner, and is isomorphic to the Unruh channel with positive quantum capacity. The complementary channel (across the horizon) is entanglement-breaking with zero capacity, avoiding a violation of the quantum no-cloning theorem. The black hole channel on the contrary has vanishing capacity, while its complement has positive capacity instead. Thus, quantum states can be reconstructed faithfully behind the black hole horizon, but not outside. This work sheds new light on black hole complementarity because it shows that black holes can both reflect and absorb quantum states without violating the no-cloning theorem, and makes quantum firewalls obsolete.

  19. Complex Nanostructures by Pulsed Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Noboyuki Koguchi

    2011-06-01

    Full Text Available What makes three dimensional semiconductor quantum nanostructures so attractive is the possibility to tune their electronic properties by careful design of their size and composition. These parameters set the confinement potential of electrons and holes, thus determining the electronic and optical properties of the nanostructure. An often overlooked parameter, which has an even more relevant effect on the electronic properties of the nanostructure, is shape. Gaining a strong control over the electronic properties via shape tuning is the key to access subtle electronic design possibilities. The Pulsed Dropled Epitaxy is an innovative growth method for the fabrication of quantum nanostructures with highly designable shapes and complex morphologies. With Pulsed Dropled Epitaxy it is possible to combine different nanostructures, namely quantum dots, quantum rings and quantum disks, with tunable sizes and densities, into a single multi-function nanostructure, thus allowing an unprecedented control over electronic properties.

  20. Bright Single InAsP Quantum Dots at Telecom Wavelengths in Position-Controlled InP Nanowires: The Role of the Photonic Waveguide.

    Science.gov (United States)

    Haffouz, Sofiane; Zeuner, Katharina D; Dalacu, Dan; Poole, Philip J; Lapointe, Jean; Poitras, Daniel; Mnaymneh, Khaled; Wu, Xiaohua; Couillard, Martin; Korkusinski, Marek; Schöll, Eva; Jöns, Klaus D; Zwiller, Valery; Williams, Robin L

    2018-05-09

    We report on the site-selected growth of bright single InAsP quantum dots embedded within InP photonic nanowire waveguides emitting at telecom wavelengths. We demonstrate a dramatic dependence of the emission rate on both the emission wavelength and the nanowire diameter. With an appropriately designed waveguide, tailored to the emission wavelength of the dot, an increase in the count rate by nearly 2 orders of magnitude (0.4 to 35 kcps) is obtained for quantum dots emitting in the telecom O-band, showing high single-photon purity with multiphoton emission probabilities down to 2%. Using emission-wavelength-optimized waveguides, we demonstrate bright, narrow-line-width emission from single InAsP quantum dots with an unprecedented tuning range of 880 to 1550 nm. These results pave the way toward efficient single-photon sources at telecom wavelengths using deterministically grown InAsP/InP nanowire quantum dots.

  1. Superconducting quantum bits

    International Nuclear Information System (INIS)

    Mooij, Hans

    2005-01-01

    Superconducting devices can be used to explore the boundaries between the quantum and classical worlds, and could also have applications in quantum information. The quantum world looks very different to the ordinary world. A quantum particle can, for instance, be in two places simultaneously, while its speed and position cannot both be measured with complete accuracy at the same time. Moreover, if its mass is small enough, a quantum particle can tunnel through energy barriers that its classical counterparts could never cross. Physicists are comfortable with the use of quantum mechanics to describe atomic and subatomic particles. However, in recent years we have discovered that micron-sized objects that have been produced using standard semiconductor-fabrication techniques - objects that are small on everyday scales but large compared with atoms - can also behave as quantum particles. These artificial quantum objects might one day be used as 'quantum bits' in a quantum computer that could perform certain computational tasks much faster than any classical computing device. Before then, however, these devices will allow us to explore the interface between the quantum and classical worlds, and to study how interactions with external degrees of freedom lead to a gradual disappearance of quantum behaviour. (U.K.)

  2. Optimal control and quantum simulations in superconducting quantum devices

    Energy Technology Data Exchange (ETDEWEB)

    Egger, Daniel J.

    2014-10-31

    Quantum optimal control theory is the science of steering quantum systems. In this thesis we show how to overcome the obstacles in implementing optimal control for superconducting quantum bits, a promising candidate for the creation of a quantum computer. Building such a device will require the tools of optimal control. We develop pulse shapes to solve a frequency crowding problem and create controlled-Z gates. A methodology is developed for the optimisation towards a target non-unitary process. We show how to tune-up control pulses for a generic quantum system in an automated way using a combination of open- and closed-loop optimal control. This will help scaling of quantum technologies since algorithms can calibrate control pulses far more efficiently than humans. Additionally we show how circuit QED can be brought to the novel regime of multi-mode ultrastrong coupling using a left-handed transmission line coupled to a right-handed one. We then propose to use this system as an analogue quantum simulator for the Spin-Boson model to show how dissipation arises in quantum systems.

  3. Quantum features of semiconductor quantum dots

    International Nuclear Information System (INIS)

    Lozada-Cassou, M.; Dong Shihai; Yu Jiang

    2004-01-01

    The exact solutions of the two-dimensional Schrodinger equation with the position-dependent mass for the square well potential in the semiconductor quantum dots system are obtained. The eigenvalues, which are closely related to the position-dependent masses μ1 and μ2, the potential well depth V0 and the radius of the quantum dots r0, can be calculated from two boundary conditions. We generalize this quantum system to three-dimensional case. The special cases for the angular momentum quantum number l=0, 1, 2 are studied in some detail. We find that the energy levels are proportional to the parameters μ2, V0 and r0 for l=0. The relations between them for l=1, 2 become very complicated. The scattering states of this quantum system are mentioned briefly

  4. Quantum optics

    National Research Council Canada - National Science Library

    Agarwal, G. S

    2013-01-01

    ..., quantum metrology, spin squeezing, control of decoherence and many other key topics. Readers are guided through the principles of quantum optics and their uses in a wide variety of areas including quantum information science and quantum mechanics...

  5. Controllability of multi-partite quantum systems and selective excitation of quantum dots

    International Nuclear Information System (INIS)

    Schirmer, S G; Pullen, I C H; Solomon, A I

    2005-01-01

    We consider the degrees of controllability of multi-partite quantum systems, as well as necessary and sufficient criteria for each case. The results are applied to the problem of simultaneous control of an ensemble of quantum dots with a single laser pulse. Finally, we apply optimal control techniques to demonstrate selective excitation of individual dots for a simultaneously controllable ensemble of quantum dots

  6. A wheel-shaped single-molecule magnet of [MnII 3MnIII 4]: quantum tunneling of magnetization under static and pulse magnetic fields.

    Science.gov (United States)

    Koizumi, Satoshi; Nihei, Masayuki; Shiga, Takuya; Nakano, Motohiro; Nojiri, Hiroyuki; Bircher, Roland; Waldmann, Oliver; Ochsenbein, Stefan T; Güdel, Hans U; Fernandez-Alonso, Felix; Oshio, Hiroki

    2007-01-01

    The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2* 4 H2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [MnII 3MnIII 4(5-NO2-hbide)6].5 C2H4Cl2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with chimT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol(-1) K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B 0 4 were estimated to be -0.283(1) K and -1.64(1)x10(-5) K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic data for an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (DeltaE) of 18.1 K and a pre-exponential factor of 1.63x10(-7) s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.

  7. Technique for long and absolute distance measurement based on laser pulse repetition frequency sweeping

    Science.gov (United States)

    Castro Alves, D.; Abreu, Manuel; Cabral, A.; Jost, Michael; Rebordão, J. M.

    2017-11-01

    In this work we present a technique to perform long and absolute distance measurements based on mode-locked diode lasers. Using a Michelson interferometer, it is possible to produce an optical cross-correlation between laser pulses of the reference arm with the pulses from the measurement arm, adjusting externally their degree of overlap either changing the pulse repetition frequency (PRF) or the position of the reference arm mirror for two (or more) fixed frequencies. The correlation of the travelling pulses for precision distance measurements relies on ultra-short pulse durations, as the uncertainty associated to the method is dependent on the laser pulse width as well as on a highly stable PRF. Mode-locked Diode lasers are a very appealing technology for its inherent characteristics, associated to compactness, size and efficiency, constituting a positive trade-off with regard to other mode-locked laser sources. Nevertheless, main current drawback is the non-availability of frequency-stable laser diodes. The laser used is a monolithic mode-locked semiconductor quantum-dot (QD) laser. The laser PRF is locked to an external stabilized RF reference. In this work we will present some of the preliminary results and discuss the importance of the requirements related to laser PRF stability in the final metrology system accuracy.

  8. Quantum Instantons and Quantum Chaos

    OpenAIRE

    Jirari, H.; Kröger, H.; Luo, X. Q.; Moriarty, K. J. M.; Rubin, S. G.

    1999-01-01

    Based on a closed form expression for the path integral of quantum transition amplitudes, we suggest rigorous definitions of both, quantum instantons and quantum chaos. As an example we compute the quantum instanton of the double well potential.

  9. Quantum metrology

    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)

  10. Effect of laser beam focus position on ion emission from plasmas produced by picosecond and sub-nanosecond laser pulses from solid targets

    Czech Academy of Sciences Publication Activity Database

    Woryna, E.; Badziak, J.; Makowski, J.; Parys, P.; Wolowski, J.; Krása, Josef; Láska, Leoš; Rohlena, Karel; Vankov, A. B.

    2001-01-01

    Roč. 31, č. 4 (2001), s. 791-798 ISSN 0078-5466 R&D Projects: GA AV ČR IAA1010105 Grant - others:KBN(PL) 2 P03B 082 19 Institutional research plan: CEZ:AV0Z1010921 Keywords : laser-produced plasma * laser beam focus position influence Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.298, year: 2001

  11. Quantum Distinction: Quantum Distinctiones!

    OpenAIRE

    Zeps, Dainis

    2009-01-01

    10 pages; How many distinctions, in Latin, quantum distinctiones. We suggest approach of anthropic principle based on anthropic reference system which should be applied equally both in theoretical physics and in mathematics. We come to principle that within reference system of life subject of mathematics (that of thinking) should be equated with subject of physics (that of nature). For this reason we enter notions of series of distinctions, quantum distinction, and argue that quantum distinct...

  12. Comparison Of Quantum Mechanical And Classical Trajectory Calculations Of Cross Sections For Ion-Atom Impact Ionization of Negative - And Positive -Ions For Heavy Ion Fusion Applications

    International Nuclear Information System (INIS)

    Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.

    2003-01-01

    Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I - and Cs + ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential

  13. Quantum beams

    International Nuclear Information System (INIS)

    Uesaka, Mitsuru

    2003-01-01

    Present state and future prospect are described on quantum beams for medical use. Efforts for compactness of linac for advanced cancer therapy have brought about the production of machines like Accuray's CyberKnife and TOMOTHERAPY (Tomo Therapy Inc.) where the acceleration frequency of X-band (9-11 GHz) is used. For cervical vein angiography by the X-band linac, a compact hard X-ray source is developed which is based on the (reverse) Compton scattering through laser-electron collision. More intense beam and laser are necessary at present. A compact machine generating the particle beam of 10 MeV-1 GeV (laser-plasma accelerator) for cancer therapy is also developed using the recent compression technique (chirped-pulse amplification) to generate laser of >10 TW. Tokyo University is studying for the electron beam with energy of GeV order, for the laser-based synchrotron X-ray, and for imaging by the short pulse ion beam. Development of advanced compact accelerators is globally attempted. In Japan, a virtual laboratory by National Institute of Radiological Sciences (NIRS), a working group of universities and research facilities through the Ministry of Education, Culture, Sports, Science and Technology, started in 2001 for practical manufacturing of the above-mentioned machines for cancer therapy and for angiography. Virtual Factory (Inc.), a business venture, is to be stood in future. (N.I.)

  14. Interaction of attosecond electromagnetic pulses with atoms: The exactly solvable model

    International Nuclear Information System (INIS)

    Popov, Yu. V.; Kouzakov, K. A.; Vinitsky, S. I.; Gusev, A. A.

    2007-01-01

    We consider the exactly solvable model of interaction of zero-duration electromagnetic pulses with an atom. The model has a number of peculiar properties which are outlined in the cases of a single pulse and two opposite pulses. In perspective, it can be useful in different fields of physics involving interaction of attosecond laser pulses with quantum systems

  15. Quantum speed limits in open system dynamics

    OpenAIRE

    del Campo, A.; Egusquiza, I. L.; Plenio, M. B.; Huelga, S. F.

    2012-01-01

    Bounds to the speed of evolution of a quantum system are of fundamental interest in quantum metrology, quantum chemical dynamics and quantum computation. We derive a time-energy uncertainty relation for open quantum systems undergoing a general, completely positive and trace preserving (CPT) evolution which provides a bound to the quantum speed limit. When the evolution is of the Lindblad form, the bound is analogous to the Mandelstam-Tamm relation which applies in the unitary case, with the ...

  16. Induced quantum conformal gravity

    International Nuclear Information System (INIS)

    Novozhilov, Y.V.; Vassilevich, D.V.

    1988-11-01

    Quantum gravity is considered as induced by matter degrees of freedom and related to the symmetry breakdown in the low energy region of a non-Abelian gauge theory of fundamental fields. An effective action for quantum conformal gravity is derived where both the gravitational constant and conformal kinetic term are positive. Relation with induced classical gravity is established. (author). 15 refs

  17. Pulse Synchronization System (PSS)

    International Nuclear Information System (INIS)

    1977-06-01

    This document is intended to serve as an operations manual, as well as a documentation of the backup analyses pertinent to the design as delivered. A history of earlier unsuccessful versions of the Pulse Synchronization System (PSS) is not included. The function of the PSS is to synchronize the time of arrival at the fusion target of laser pulses that are propagated through the 20 amplifier chains of the SHIVA laser. The positional accuracy requirement is +-1.5 mm (+-5 psec), and is obtained by the PSS with a wide margin factor

  18. S100 lathe bed pulse generator applied to pulsed nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Cernicchiaro, G.R.C.; Rudge, M.G.; Albuquerque, M.P.

    1989-01-01

    The project and construction of four channel pulse generator in the S100 standard plate and its control software for microcomputer are described. The microcomputer has total control on the pulse generator, which has seven programable parameters, defining the position of four pulses and the width for the three first ones. This pulse generator is controlled by a software developed in c language, and is used in pulsed nuclear magnetic resonance experiences. (M.C.K.) [pt

  19. Analytical investigation of one-dimensional Rydberg atoms interacting with half-cycle pulses

    International Nuclear Information System (INIS)

    Bersons, I.; Veilande, R.

    2004-01-01

    Classical, quantum-mechanical, and semiclassical expressions for the transition probability in one-dimensional Rydberg atom irradiated by short half-cycle pulse are derived and compared. The simple formulas obtained for excitation of Rydberg atom by two time delayed weak half-cycle pulses reproduce well the experimental data and the solutions of time-dependent Schroedinger equation. When the transferred momenta are stronger and positive, the transition probabilities exhibit fast oscillations with time delay between the pulses. The classical transition probability is constant in time. For negative transferred momenta a focusing phenomenon is observed, and there is a region in time delay, where the transition probabilities oscillate with the Kepler period

  20. Pulse plating

    CERN Document Server

    Hansal, Wolfgang E G; Green, Todd; Leisner, Peter; Reichenbach, Andreas

    2012-01-01

    The electrodeposition of metals using pulsed current has achieved practical importance in recent years. Although it has long been known that changes in potential, with or without polarity reversal, can significantly affect the deposition process, the practical application of this has been slow to be adopted. This can largely be explained in terms of the complex relationship between the current regime and its effect on the electrodeposition process. In order to harness these effects, an understanding of the anodic and cathodic electrochemical processes is necessary, together with the effects of polarity reversal and the rate of such reversals. In this new monograph, the basics of metal electrodeposition from solution are laid out in great detail in seven distinct chapters. With this knowledge, the reader is able to predict how a given pulse train profile can be adopted to achieve a desired outcome. Equally important is the choice of a suitable rectifier and the ancillary control circuits to enable pulse platin...

  1. Short pulse neutron generator

    Science.gov (United States)

    Elizondo-Decanini, Juan M.

    2016-08-02

    Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and the switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.

  2. Improving the precision of linear optics measurements based on turn-by-turn beam position monitor data after a pulsed excitation in lepton storage rings

    Directory of Open Access Journals (Sweden)

    L. Malina

    2017-08-01

    Full Text Available Beam optics control is of critical importance for machine performance and protection. Nowadays, turn-by-turn (TbT beam position monitor (BPM data are increasingly exploited as they allow for fast and simultaneous measurement of various optics quantities. Nevertheless, so far the best documented uncertainty of measured β-functions is of about 10‰ rms. In this paper we compare the β-functions of the ESRF storage ring measured from two different TbT techniques—the N-BPM and the Amplitude methods—with the ones inferred from a measurement of the orbit response matrix (ORM. We show how to improve the precision of TbT techniques by refining the Fourier transform of TbT data with properly chosen excitation amplitude. The precision of the N-BPM method is further improved by refining the phase advance measurement. This represents a step forward compared to standard TbT measurements. First experimental results showing the precision of β-functions pushed down to 4‰ both in TbT and ORM techniques are reported and commented.

  3. Attosecond pulse trains from long laser-gas interaction targets

    International Nuclear Information System (INIS)

    Hauri, C.P.; Lopez-Martens, R.; Varju, K.; Ruchon, T.; Gustafsson, E.; L'Huillier, A.

    2006-01-01

    Complete test of publication follows. Many experiments in attosecond physics require high XUV photon flux as well as a clean attosecond pulse train (APT) temporal structure. Temporal characterization of high-order harmonic generation (HHG) in long interaction targets is thus of high interest. HHG being a very inefficient process, a large effort has been made to increase the amount of XUV photons emitted per infrared laser pulse. Besides quasi phase-matching in a modulated capillary, loose driving laser focusing conditions and subsequent self-channeling have shown to significantly increase the conversion efficiency. We characterized the temporal structure of APTs generated during the self-channeling of an intense IR driving laser pulse. Our first results indicate, however, that the temporal structure of the APT generated during the HHG process might be affected by quantum path interference and spectral phase distortion due to the self-channeling process itself. In particular, our measurements show that the relative spectral phase between consecutive harmonics can strongly vary depending on the target length and the position of the laser focus with respect to the target. In general for short gas targets, no clean APT structure can be expected since the individual attosecond pulses carry significant chirp. For longer targets, however, we observe a flattening of the harmonic spectral phase, resulting in near-transform-limited attosecond pulse trains. A complete analysis of the process is complex and involves detailed knowledge of the spatial and temporal evolution of the self-channeling driver laser pulse throughout the gas target.

  4. Quantum walks, quantum gates, and quantum computers

    International Nuclear Information System (INIS)

    Hines, Andrew P.; Stamp, P. C. E.

    2007-01-01

    The physics of quantum walks on graphs is formulated in Hamiltonian language, both for simple quantum walks and for composite walks, where extra discrete degrees of freedom live at each node of the graph. It is shown how to map between quantum walk Hamiltonians and Hamiltonians for qubit systems and quantum circuits; this is done for both single-excitation and multiexcitation encodings. Specific examples of spin chains, as well as static and dynamic systems of qubits, are mapped to quantum walks, and walks on hyperlattices and hypercubes are mapped to various gate systems. We also show how to map a quantum circuit performing the quantum Fourier transform, the key element of Shor's algorithm, to a quantum walk system doing the same. The results herein are an essential preliminary to a Hamiltonian formulation of quantum walks in which coupling to a dynamic quantum environment is included

  5. Linear transformer driver for pulse generation

    Science.gov (United States)

    Kim, Alexander A; Mazarakis, Michael G; Sinebryukhov, Vadim A; Volkov, Sergey N; Kondratiev, Sergey S; Alexeenko, Vitaly M; Bayol, Frederic; Demol, Gauthier; Stygar, William A

    2015-04-07

    A linear transformer driver includes at least one ferrite ring positioned to accept a load. The linear transformer driver also includes a first power delivery module that includes a first charge storage devices and a first switch. The first power delivery module sends a first energy in the form of a first pulse to the load. The linear transformer driver also includes a second power delivery module including a second charge storage device and a second switch. The second power delivery module sends a second energy in the form of a second pulse to the load. The second pulse has a frequency that is approximately three times the frequency of the first pulse. The at least one ferrite ring is positioned to force the first pulse and the second pulse to the load by temporarily isolating the first pulse and the second pulse from an electrical ground.

  6. Quantum memory Quantum memory

    Science.gov (United States)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  7. Nonlinear Michelson interferometer for improved quantum metrology

    OpenAIRE

    Luis, Alfredo; Rivas, Ángel

    2015-01-01

    We examine quantum detection via a Michelson interferometer embedded in a gas with Kerr nonlinearity. This nonlinear interferometer is illuminated by pulses of classical light. This strategy combines the robustness against practical imperfections of classical light with the improvement provided by nonlinear processes. Regarding ultimate quantum limits, we stress that, as a difference with linear schemes, the nonlinearity introduces pulse duration as a new variable into play along with the ene...

  8. Powerful nanosecond pulse train generator

    International Nuclear Information System (INIS)

    Isakov, I.F.; Logachev, E.I.; Opekunov, M.S.; Pechenkin, S.A.; Remnev, G.E.; Usov, Yu.P.

    1987-01-01

    A generator permitting to shape on the load pulsed with the repetition frequency of 10 3 -10 6 Hz and more is described. The amplitude of shaped voltage pulses is up to 150 kV at pulse duration equal to 50 ns. The generator comprises connected in-series with the load two shaping and two transmission lines realized on the base of the KVI-300 low-ohmic cable. The shaping lines are supplied from two independently connected pulse voltage generators for obtaining time interval between pulses > 10 -6 s; they may be also supplied from one generator for obtaining time interval -6 s. At the expense of reducing losses in the discharge circuit the amplitude of the second pulse grows with increase of time interval between pulses up to 300 ns, further on the curve flat-topping exists. The described generator is used in high-current accelerators, in which the primary negative pulse results in generation of explosive-emission plasma, and the second positive pulse provides ion beam shaping including ions of heavy metal used for production of a potential electrode. The generator multipulse mode is used for successive ion acceleration in the transport system

  9. Free-Space Quantum Communication with a Portable Quantum Memory

    Science.gov (United States)

    Namazi, Mehdi; Vallone, Giuseppe; Jordaan, Bertus; Goham, Connor; Shahrokhshahi, Reihaneh; Villoresi, Paolo; Figueroa, Eden

    2017-12-01

    The realization of an elementary quantum network that is intrinsically secure and operates over long distances requires the interconnection of several quantum modules performing different tasks. In this work, we report the realization of a communication network functioning in a quantum regime, consisting of four different quantum modules: (i) a random polarization qubit generator, (ii) a free-space quantum-communication channel, (iii) an ultralow-noise portable quantum memory, and (iv) a qubit decoder, in a functional elementary quantum network possessing all capabilities needed for quantum-information distribution protocols. We create weak coherent pulses at the single-photon level encoding polarization states |H ⟩ , |V ⟩, |D ⟩, and |A ⟩ in a randomized sequence. The random qubits are sent over a free-space link and coupled into a dual-rail room-temperature quantum memory and after storage and retrieval are analyzed in a four-detector polarization analysis akin to the requirements of the BB84 protocol. We also show ultralow noise and fully portable operation, paving the way towards memory-assisted all-environment free-space quantum cryptographic networks.

  10. Quantum stochastics

    CERN Document Server

    Chang, Mou-Hsiung

    2015-01-01

    The classical probability theory initiated by Kolmogorov and its quantum counterpart, pioneered by von Neumann, were created at about the same time in the 1930s, but development of the quantum theory has trailed far behind. Although highly appealing, the quantum theory has a steep learning curve, requiring tools from both probability and analysis and a facility for combining the two viewpoints. This book is a systematic, self-contained account of the core of quantum probability and quantum stochastic processes for graduate students and researchers. The only assumed background is knowledge of the basic theory of Hilbert spaces, bounded linear operators, and classical Markov processes. From there, the book introduces additional tools from analysis, and then builds the quantum probability framework needed to support applications to quantum control and quantum information and communication. These include quantum noise, quantum stochastic calculus, stochastic quantum differential equations, quantum Markov semigrou...

  11. Practical quantum coin flipping

    International Nuclear Information System (INIS)

    Pappa, Anna; Diamanti, Eleni; Chailloux, Andre; Kerenidis, Iordanis

    2011-01-01

    We show that in the unconditional security model, a single quantum strong coin flip with security guarantees that are strictly better than in any classical protocol is possible to implement with current technology. Our protocol takes into account all aspects of an experimental implementation, including losses, multiphoton pulses emitted by practical photon sources, channel noise, detector dark counts, and finite quantum efficiency. We calculate the abort probability when both players are honest, as well as the probability of one player forcing his desired outcome. For a channel length up to 21 km and commonly used parameter values, we can achieve honest abort and cheating probabilities that are better than in any classical protocol. Our protocol is, in principle, implementable using attenuated laser pulses, with no need for entangled photons or any other specific resources.

  12. Quantum Computing

    OpenAIRE

    Scarani, Valerio

    1998-01-01

    The aim of this thesis was to explain what quantum computing is. The information for the thesis was gathered from books, scientific publications, and news articles. The analysis of the information revealed that quantum computing can be broken down to three areas: theories behind quantum computing explaining the structure of a quantum computer, known quantum algorithms, and the actual physical realizations of a quantum computer. The thesis reveals that moving from classical memor...

  13. Quantum Malware

    OpenAIRE

    Wu, Lian-Ao; Lidar, Daniel A.

    2005-01-01

    When quantum communication networks proliferate they will likely be subject to a new type of attack: by hackers, virus makers, and other malicious intruders. Here we introduce the concept of "quantum malware" to describe such human-made intrusions. We offer a simple solution for storage of quantum information in a manner which protects quantum networks from quantum malware. This solution involves swapping the quantum information at random times between the network and isolated, distributed an...

  14. Quantumness beyond quantum mechanics

    International Nuclear Information System (INIS)

    Sanz, Ángel S

    2012-01-01

    Bohmian mechanics allows us to understand quantum systems in the light of other quantum traits than the well-known ones (coherence, diffraction, interference, tunnelling, discreteness, entanglement, etc.). Here the discussion focusses precisely on two of these interesting aspects, which arise when quantum mechanics is thought within this theoretical framework: the non-crossing property, which allows for distinguishability without erasing interference patterns, and the possibility to define quantum probability tubes, along which the probability remains constant all the way. Furthermore, taking into account this hydrodynamic-like description as a link, it is also shown how this knowledge (concepts and ideas) can be straightforwardly transferred to other fields of physics (for example, the transmission of light along waveguides).

  15. Qubit lattice coherence induced by electromagnetic pulses in superconducting metamaterials.

    Science.gov (United States)

    Ivić, Z; Lazarides, N; Tsironis, G P

    2016-07-12

    Quantum bits (qubits) are at the heart of quantum information processing schemes. Currently, solid-state qubits, and in particular the superconducting ones, seem to satisfy the requirements for being the building blocks of viable quantum computers, since they exhibit relatively long coherence times, extremely low dissipation, and scalability. The possibility of achieving quantum coherence in macroscopic circuits comprising Josephson junctions, envisioned by Legett in the 1980's, was demonstrated for the first time in a charge qubit; since then, the exploitation of macroscopic quantum effects in low-capacitance Josephson junction circuits allowed for the realization of several kinds of superconducting qubits. Furthermore, coupling between qubits has been successfully achieved that was followed by the construction of multiple-qubit logic gates and the implementation of several algorithms. Here it is demonstrated that induced qubit lattice coherence as well as two remarkable quantum coherent optical phenomena, i.e., self-induced transparency and Dicke-type superradiance, may occur during light-pulse propagation in quantum metamaterials comprising superconducting charge qubits. The generated qubit lattice pulse forms a compound "quantum breather" that propagates in synchrony with the electromagnetic pulse. The experimental confirmation of such effects in superconducting quantum metamaterials may open a new pathway to potentially powerful quantum computing.

  16. Nonlinear Dynamics In Quantum Physics -- Quantum Chaos and Quantum Instantons

    OpenAIRE

    Kröger, H.

    2003-01-01

    We discuss the recently proposed quantum action - its interpretation, its motivation, its mathematical properties and its use in physics: quantum mechanical tunneling, quantum instantons and quantum chaos.

  17. Robust dynamical decoupling for quantum computing and quantum memory.

    Science.gov (United States)

    Souza, Alexandre M; Alvarez, Gonzalo A; Suter, Dieter

    2011-06-17

    Dynamical decoupling (DD) is a popular technique for protecting qubits from the environment. However, unless special care is taken, experimental errors in the control pulses used in this technique can destroy the quantum information instead of preserving it. Here, we investigate techniques for making DD sequences robust against different types of experimental errors while retaining good decoupling efficiency in a fluctuating environment. We present experimental data from solid-state nuclear spin qubits and introduce a new DD sequence that is suitable for quantum computing and quantum memory.

  18. Pulsed power

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    The key element of our pulsed power program is concentration of power in time and space by suppression of breakdown in dielectrics and in vacuum. Magnetically insulated vacuum transmission lines and magnetic suppression of insulator flashover have continued as the main reserch directions. Vacuum insulated line studies at Physics International have been expanded and a test bed at Sandia, called MITE (Magnetically Insulated Transmission Experiment), is under development. The choice for the baseline EBFA design will depend on the outcome of these studies and should be made in July 1977. The slow and intermediate speed pulsed power approaches to EBFA will be based on Proto I and Proto II results and several of the projected EBFA subsystems are presently being tested in Proto II. A further stage of power concentration, within the vacuum diode itself, would considerably ease the burden on dielectrics; methods of power multiplication involving magnetically imploded plasmas are being considered and tests have begun using the Ripple III apparatus

  19. Pulsed feedback defers cellular differentiation.

    Directory of Open Access Journals (Sweden)

    Joe H Levine

    2012-01-01

    Full Text Available Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable "polyphasic" positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a "timer" that operates over timescales much longer than a cell cycle.

  20. Tackling systematic errors in quantum logic gates with composite rotations

    International Nuclear Information System (INIS)

    Cummins, Holly K.; Llewellyn, Gavin; Jones, Jonathan A.

    2003-01-01

    We describe the use of composite rotations to combat systematic errors in single-qubit quantum logic gates and discuss three families of composite rotations which can be used to correct off-resonance and pulse length errors. Although developed and described within the context of nuclear magnetic resonance quantum computing, these sequences should be applicable to any implementation of quantum computation

  1. Quantum control with NMR methods: Application to quantum simulations

    International Nuclear Information System (INIS)

    Negrevergne, Camille

    2002-01-01

    Manipulating information according to quantum laws allows improvements in the efficiency of the way we treat certain problems. Liquid state Nuclear Magnetic Resonance methods allow us to initialize, manipulate and read the quantum state of a system of coupled spins. These methods have been used to realize an experimental small Quantum Information Processor (QIP) able to process information through around hundred elementary operations. One of the main themes of this work was to design, optimize and validate reliable RF-pulse sequences used to 'program' the QIP. Such techniques have been used to run a quantum simulation algorithm for anionic systems. Some experimental results have been obtained on the determination of Eigen energies and correlation function for a toy problem consisting of fermions on a lattice, showing an experimental proof of principle for such quantum simulations. (author) [fr

  2. Quantum random number generator

    Science.gov (United States)

    Soubusta, Jan; Haderka, Ondrej; Hendrych, Martin

    2001-03-01

    Since reflection or transmission of a quantum particle on a beamsplitter is inherently random quantum process, a device built on this principle does not suffer from drawbacks of neither pseudo-random computer generators or classical noise sources. Nevertheless, a number of physical conditions necessary for high quality random numbers generation must be satisfied. Luckily, in quantum optics realization they can be well controlled. We present an easy random number generator based on the division of weak light pulses on a beamsplitter. The randomness of the generated bit stream is supported by passing the data through series of 15 statistical test. The device generates at a rate of 109.7 kbit/s.

  3. SU-E-J-231: Comparison of Delineation Variability of Soft Tissue Volume and Position in Head-And-Neck Between Two T1-Weighted Pulse Sequences Using An MR-Simulator with Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Wong, O; Lo, G; Yuan, J; Law, M; Ding, A; Cheng, K; Chan, K; Cheung, K; Yu, S [Hong Kong Sanatorium & Hospital, Hong Kong (Hong Kong)

    2015-06-15

    Purpose: There is growing interests in applying MR-simulator(MR-sim) in radiotherapy but MR images subject to hardware, patient and pulse sequence dependent geometric distortion that may potentially influence target definition. This study aimed to evaluate the influence on head-and-neck tissue delineation, in terms of positional and volumetric variability, of two T1-weighted(T1w) MR sequences on a 1.5T MR-sim Methods: Four healthy volunteers were scanned (4 scans for each on different days) using both spin-echo (3DCUBE, TR/TE=500/14ms, TA=183s) and gradient-echo sequences (3DFSPGR, TE/TR=7/4ms, TA=173s) with identical coverage, voxel-size(0.8×0.8×1.0mm3), receiver-bandwidth(62.5kHz/pix) and geometric correction on a 1.5T MR-sim immobilized with personalized thermoplastic cast and head-rest. Under this setting, similar T1w contrast and signal-to-noise ratio were obtained, and factors other than sequence that might bias image distortion and tissue delineation were minimized. VOIs of parotid gland(PGR, PGL), pituitary gland(PIT) and eyeballs(EyeL, EyeR) were carefully drawn, and inter-scan coefficient-of-variation(CV) of VOI centroid position and volume were calculated for each subject. Mean and standard deviation(SD) of the CVs for four subjects were compared between sequences using Wilcoxon ranksum test. Results: The mean positional(<4%) and volumetric(<7%) CVs varied between tissues, majorly dependent on tissue inherent properties like volume, location, mobility and deformability. Smaller mean volumetric CV was found in 3DCUBE, probably due to its less proneness to tissue susceptibility, but only PGL showed significant difference(P<0.05). Positional CVs had no significant differences for all VOIs(P>0.05) between sequences, suggesting volumetric variation might be more sensitive to sequence-dependent delineation difference. Conclusion: Although 3DCUBE is considered less prone to tissue susceptibility-induced artifact and distortion, our preliminary data showed

  4. Quantum manipulation of two-color stationary light: Quantum wavelength conversion

    International Nuclear Information System (INIS)

    Moiseev, S. A.; Ham, B. S.

    2006-01-01

    We present a quantum manipulation of a traveling light pulse using electromagnetically induced transparency-based slow light phenomenon for the generation of two-color stationary light. We theoretically discuss the two-color stationary light for the quantum wavelength conversion process in terms of pulse area, energy transfer, and propagation directions. The condition of the two-color stationary light pulse generation has been found and the quantum light dynamics has been studied analytically in the adiabatic limit. The quantum frequency conversion rate of the traveling light is dependent on the spatial spreading of the two-color stationary light pulse and can be near unity in an optically dense medium for the optimal frequencies of the control laser fields

  5. Experiments with trapped ions and ultrafast laser pulses

    Science.gov (United States)

    Johnson, Kale Gifford

    Since the dawn of quantum information science, laser-cooled trapped atomic ions have been one of the most compelling systems for the physical realization of a quantum computer. By applying qubit state dependent forces to the ions, their collective motional modes can be used as a bus to realize entangling quantum gates. Ultrafast state-dependent kicks [1] can provide a universal set of quantum logic operations, in conjunction with ultrafast single qubit rotations [2], which uses only ultrafast laser pulses. This may present a clearer route to scaling a trapped ion processor [3]. In addition to the role that spin-dependent kicks (SDKs) play in quantum computation, their utility in fundamental quantum mechanics research is also apparent. In this thesis, we present a set of experiments which demonstrate some of the principle properties of SDKs including ion motion independence (we demonstrate single ion thermometry from the ground state to near room temperature and the largest Schrodinger cat state ever created in an oscillator), high speed operations (compared with conventional atom-laser interactions), and multi-qubit entanglement operations with speed that is not fundamentally limited by the trap oscillation frequency. We also present a method to provide higher stability in the radial mode ion oscillation frequencies of a linear radiofrequency (rf) Paul trap-a crucial factor when performing operations on the rf-sensitive modes. Finally, we present the highest atomic position sensitivity measurement of an isolated atom to date of 0.5 nm Hz. (-1/2) with a minimum uncertaintyof 1.7 nm using a 0.6 numerical aperature (NA) lens system, along with a method to correct aberrations and a direct position measurement of ion micromotion (the inherent oscillations of an ion trapped in an oscillating rf field). This development could be used to directly image atom motion in the quantum regime, along with sensing forces at the yoctonewton [10. (-24) N)] scale forgravity sensing

  6. Slow light and pulse propagation in semiconductor waveguides

    DEFF Research Database (Denmark)

    Hansen, Per Lunnemann

    This thesis concerns the propagation of optical pulses in semiconductor waveguide structures with particular focus on methods for achieving slow light or signal delays. Experimental pulse propagation measurements of pulses with a duration of 180 fs, transmitted through quantum well based waveguide...... structures, are presented. Simultaneous measurements of the pulse transmission and delay are measured as a function of input pulse energy for various applied electrical potentials. Electrically controlled pulse delay and advancement are demonstrated and compared with a theoretical model. The limits...... of the model as well as the underlying physical mechanisms are analysed and discussed. A method to achieve slow light by electromagnetically induced transparency (EIT) in an inhomogeneously broadened quantum dot medium is proposed. The basic principles of EIT are assessed and the main dissimilarities between...

  7. Holograms made with a pulsed dye laser

    International Nuclear Information System (INIS)

    Fernandez-Guasti, M.; Iturbe-Castillo, D.; Silva-Perez, A.; Gil-Villegas, A.; Gonzalez-Torres, H.; Lopez-Guerrero, R.

    1989-01-01

    We report the obtention of holograms with a nitrogen pumped dye laser, whose source is inherently pulsed. We review the advantages and posibilities of holograms of moving objects which are impossible to make with CW lasers. The lasers used in these experiments were designed and built in the quantum optics laboratory at the Universidad Autonoma Metropolitana-Iztapalapa. (Author)

  8. Quantum mechanics

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    The book is on quantum mechanics. The emphasis is on the basic concepts and the methodology. The chapters include: Breakdown of classical concepts; Quantum mechanical concepts; Basic postulates of quantum mechanics; solution of problems in quantum mechanics; Simple harmonic oscillator; and Angular Momentum

  9. Quantum matter

    International Nuclear Information System (INIS)

    Buechler, Hans Peter; Calcarco, Tommaso; Dressel, Martin

    2008-01-01

    The following topics are dealt with: Artificial atoms and molecules, tailored from solids, fractional flux quanta, molecular magnets, controlled interaction in quantum gases, the theory of quantum correlations in mott matter, cold gases, and mesoscopic systems, Bose-Einstein condensates on the chip, on the route to the quantum computer, a quantum computer in diamond. (HSI)

  10. Quantum fluctuations

    International Nuclear Information System (INIS)

    Reynaud, S.; Giacobino, S.; Zinn-Justin, J.

    1997-01-01

    This course is dedicated to present in a pedagogical manner the recent developments in peculiar fields concerned by quantum fluctuations: quantum noise in optics, light propagation through dielectric media, sub-Poissonian light generated by lasers and masers, quantum non-demolition measurements, quantum electrodynamics applied to cavities and electrical circuits involving superconducting tunnel junctions. (A.C.)

  11. Pulsed neutron source well logging system

    International Nuclear Information System (INIS)

    Dillingham, M.E.

    1975-01-01

    A pulsed neutron source with a chamber containing a plurality of alpha emitting strips and beryllium targets coaxially mounted is described. A pulsed source is provided by rotation of the target to on-off positions along with electromagnetic and magnetic devices for positive locking and rotation. (U.S.)

  12. Quantum radar

    CERN Document Server

    Lanzagorta, Marco

    2011-01-01

    This book offers a concise review of quantum radar theory. Our approach is pedagogical, making emphasis on the physics behind the operation of a hypothetical quantum radar. We concentrate our discussion on the two major models proposed to date: interferometric quantum radar and quantum illumination. In addition, this book offers some new results, including an analytical study of quantum interferometry in the X-band radar region with a variety of atmospheric conditions, a derivation of a quantum radar equation, and a discussion of quantum radar jamming.This book assumes the reader is familiar w

  13. Quantum information

    International Nuclear Information System (INIS)

    Kilin, Sergei Ya

    1999-01-01

    A new research direction known as quantum information is a multidisciplinary subject which involves quantum mechanics, optics, information theory, programming, discrete mathematics, laser physics and spectroscopy, and depends heavily on contributions from such areas as quantum computing, quantum teleportation and quantum cryptography, decoherence studies, and single-molecule and impurity spectroscopy. Some new results achieved in this rapidly growing field are discussed. (reviews of topical problems)

  14. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Kilin, Sergei Ya [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    1999-05-31

    A new research direction known as quantum information is a multidisciplinary subject which involves quantum mechanics, optics, information theory, programming, discrete mathematics, laser physics and spectroscopy, and depends heavily on contributions from such areas as quantum computing, quantum teleportation and quantum cryptography, decoherence studies, and single-molecule and impurity spectroscopy. Some new results achieved in this rapidly growing field are discussed. (reviews of topical problems)

  15. Quantum ontologies

    International Nuclear Information System (INIS)

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs

  16. PULSE COLUMN

    Science.gov (United States)

    Grimmett, E.S.

    1964-01-01

    This patent covers a continuous countercurrent liquidsolids contactor column having a number of contactor states each comprising a perforated plate, a layer of balls, and a downcomer tube; a liquid-pulsing piston; and a solids discharger formed of a conical section at the bottom of the column, and a tubular extension on the lowest downcomer terminating in the conical section. Between the conical section and the downcomer extension is formed a small annular opening, through which solids fall coming through the perforated plate of the lowest contactor stage. This annular opening is small enough that the pressure drop thereacross is greater than the pressure drop upward through the lowest contactor stage. (AEC)

  17. Pulse radiolysis

    International Nuclear Information System (INIS)

    Greenshields, H.; Seddon, W.A.

    1982-03-01

    This supplement to two bibliographies published in 1970 and 1972 lists 734 references to the literature of pulse radiolysis, arranged under eight broad subject headings. The references were compiled by searching Biological Abstracts, Chemical Abstracts, Nuclear Science Abstracts and the Weekly List of Papers in Radiation Chemistry issued by the Radiation Chemistry Data Center of Notre Dame University. Full bibliographic data is given for papers published in the period 1971 to 1974. A personal author index listing more than 600 authors and a similar number of co-authors is included

  18. Temporal Airy pulses control cell poration

    Directory of Open Access Journals (Sweden)

    S. Courvoisier

    2016-07-01

    Full Text Available We show that spectral phase shaping of fs-laser pulses can be used to optimize laser-cell membrane interactions in water environment. The energy and peak intensity thresholds required for cell poration with single pulse in the nJ range can be significantly reduced (25% reduction in energy and 88% reduction in peak intensity by using temporal Airy pulses, controlled by positive third order dispersion, as compared to bandwidth limited pulses. Temporal Airy pulses are also effective to control the morphology of the induced pores, with prospective applications from cellular to tissue opto-surgery and transfection.

  19. Quantum Computer Games: Quantum Minesweeper

    Science.gov (United States)

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

  20. Pulse pile-up. I: Short pulses

    International Nuclear Information System (INIS)

    Wilkinson, D.H.

    1990-07-01

    The search for rare large pulses against an intense background of smaller ones involves consideration of pulse pile-up. Approximate methods are presented, based on ruin theory, by which the probability of such pile-up may be estimated for pulses of arbitrary form and of arbitrary pulse-height distribution. These methods are checked against cases for which exact solutions are available. The present paper is concerned chiefly with short pulses of finite total duration. (Author) (5 refs., 24 figs.)

  1. The open quantum Brownian motions

    International Nuclear Information System (INIS)

    Bauer, Michel; Bernard, Denis; Tilloy, Antoine

    2014-01-01

    Using quantum parallelism on random walks as the original seed, we introduce new quantum stochastic processes, the open quantum Brownian motions. They describe the behaviors of quantum walkers—with internal degrees of freedom which serve as random gyroscopes—interacting with a series of probes which serve as quantum coins. These processes may also be viewed as the scaling limit of open quantum random walks and we develop this approach along three different lines: the quantum trajectory, the quantum dynamical map and the quantum stochastic differential equation. We also present a study of the simplest case, with a two level system as an internal gyroscope, illustrating the interplay between the ballistic and diffusive behaviors at work in these processes. Notation H z : orbital (walker) Hilbert space, C Z in the discrete, L 2 (R) in the continuum H c : internal spin (or gyroscope) Hilbert space H sys =H z ⊗H c : system Hilbert space H p : probe (or quantum coin) Hilbert space, H p =C 2 ρ t tot : density matrix for the total system (walker + internal spin + quantum coins) ρ-bar t : reduced density matrix on H sys : ρ-bar t =∫dxdy ρ-bar t (x,y)⊗|x〉 z 〈y| ρ-hat t : system density matrix in a quantum trajectory: ρ-hat t =∫dxdy ρ-hat t (x,y)⊗|x〉 z 〈y|. If diagonal and localized in position: ρ-hat t =ρ t ⊗|X t 〉 z 〈X t | ρ t : internal density matrix in a simple quantum trajectory X t : walker position in a simple quantum trajectory B t : normalized Brownian motion ξ t , ξ t † : quantum noises (paper)

  2. Random quantum operations

    International Nuclear Information System (INIS)

    Bruzda, Wojciech; Cappellini, Valerio; Sommers, Hans-Juergen; Zyczkowski, Karol

    2009-01-01

    We define a natural ensemble of trace preserving, completely positive quantum maps and present algorithms to generate them at random. Spectral properties of the superoperator Φ associated with a given quantum map are investigated and a quantum analogue of the Frobenius-Perron theorem is proved. We derive a general formula for the density of eigenvalues of Φ and show the connection with the Ginibre ensemble of real non-symmetric random matrices. Numerical investigations of the spectral gap imply that a generic state of the system iterated several times by a fixed generic map converges exponentially to an invariant state

  3. Quantum interaction. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Bruza, Peter [Queensland Univ. of Technology, Brisbane (Australia). Faculty of Science and Technology; Sofge, Donald [Navy Center for Applied Research in Artificial Intelligence, Washington, DC (United States). Naval Research Lab.; Lawless, William [Paine Coll., Augusta, GA (United States); Rijsbergen, Keith van [Glasgow Univ. (United Kingdom). Dept. of Computing Science; Klusch, Matthias (eds.) [German Research Center for Artificial Intelligence, Saarbruecken (Germany)

    2009-07-01

    This book constitutes the refereed proceedings of the Third International Symposium on Quantum Interaction, QI 2009, held in Saarbruecken, Germany, in March 2009. The 21 revised full papers presented together with the 3 position papers were carefully reviewed and selected from numerous submissions. The papers show the cross-disciplinary nature of quantum interaction covering topics such as computation, cognition, decision theory, information retrieval, information systems, social interaction, computational linguistics and finance. (orig.)

  4. Quantum interaction. Proceedings

    International Nuclear Information System (INIS)

    Bruza, Peter; Rijsbergen, Keith van

    2009-01-01

    This book constitutes the refereed proceedings of the Third International Symposium on Quantum Interaction, QI 2009, held in Saarbruecken, Germany, in March 2009. The 21 revised full papers presented together with the 3 position papers were carefully reviewed and selected from numerous submissions. The papers show the cross-disciplinary nature of quantum interaction covering topics such as computation, cognition, decision theory, information retrieval, information systems, social interaction, computational linguistics and finance. (orig.)

  5. Focus on Quantum Cryptography

    International Nuclear Information System (INIS)

    Kwiat, Paul G.

    2002-01-01

    Full text: In our modern era of telecommunications and the Internet, information has become a valuable commodity. Sometimes it must therefore be protected against theft - in this case, loss of secret information to an eavesdropper. Most of today's transactions are protected using encryption unproven to be secure against a computational attack by a classical computer and, in fact, the standardly used encryption algorithms are provably vulnerable to the mind-boggling parallelism of a quantum computer, should one ever be physically realized. Enter quantum cryptography. Underlying nearly all forms of encryption is the necessity for a truly secret key, a random string of zeros and ones; the basic notion of quantum cryptography is to employ single photon transmissions (or the closest attainable approximation to these) to distribute the random key material, while removing the threat of an undetected eavesdropper. Now, nearly twenty years since the seminal quantum cryptography paper by Bennett and Brassard (Bennett C H and Brassard G 1984 Proc. IEEE Int. Conf. on Computers, Systems, and Signal Processing (Bangalore) (New York: IEEE) pp 175-9), we take a look at several state-of-the-art implementations, and glimpse how future quantum cryptosystems might look. We start with papers from three of the world's leading experimental quantum cryptography efforts: Stucki et al and Bethune and Risk describe working systems for quantum key distribution (QKD) over telecommunications fibres (at 1550 nanometres and 1300 nanometres, respectively). The former's achievement of quantum key exchange over 67 kilometres of optical fibre is a world record, as is the experimental demonstration by Hughes et al of daylight free-space QKD over a 10 km atmospheric range. Next, Luetkenhaus and Jahma explore the possible vulnerabilities of such systems (which employ attenuated laser pulses instead of actual single photon states) to conceivable future eavesdropping technologies. Enzer et al have

  6. A Spatial Domain Quantum Watermarking Scheme

    International Nuclear Information System (INIS)

    Wei Zhan-Hong; Chen Xiu-Bo; Niu Xin-Xin; Yang Yi-Xian; Xu Shu-Jiang

    2016-01-01

    This paper presents a spatial domain quantum watermarking scheme. For a quantum watermarking scheme, a feasible quantum circuit is a key to achieve it. This paper gives a feasible quantum circuit for the presented scheme. In order to give the quantum circuit, a new quantum multi-control rotation gate, which can be achieved with quantum basic gates, is designed. With this quantum circuit, our scheme can arbitrarily control the embedding position of watermark images on carrier images with the aid of auxiliary qubits. Besides reversely acting the given quantum circuit, the paper gives another watermark extracting algorithm based on quantum measurements. Moreover, this paper also gives a new quantum image scrambling method and its quantum circuit. Differ from other quantum watermarking schemes, all given quantum circuits can be implemented with basic quantum gates. Moreover, the scheme is a spatial domain watermarking scheme, and is not based on any transform algorithm on quantum images. Meanwhile, it can make sure the watermark be secure even though the watermark has been found. With the given quantum circuit, this paper implements simulation experiments for the presented scheme. The experimental result shows that the scheme does well in the visual quality and the embedding capacity. (paper)

  7. Temporal compression of quantum-information-carrying photons using a photon-echo quantum memory approach

    International Nuclear Information System (INIS)

    Moiseev, S. A.; Tittel, W.

    2010-01-01

    We study quantum compression and decompression of light pulses that carry quantum information using a photon-echo quantum memory technique with controllable inhomogeneous broadening of an isolated atomic absorption line. We investigate media with differently broadened absorption profiles, transverse and longitudinal, finding that the recall efficiency can be as large as unity and that the quantum information encoded into the photonic qubits can remain unperturbed. Our results provide insight into reversible light-atom interaction and are interesting in view of future quantum communication networks, where pulse compression and decompression may play an important role in increasing the qubit rate or in mapping quantum information from photonic carriers with large optical bandwidth into atomic memories with smaller bandwidth.

  8. 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.

  9. Analytical optimal pulse shapes obtained with the aid of genetic algorithms

    International Nuclear Information System (INIS)

    Guerrero, Rubén D.; Arango, Carlos A.; Reyes, Andrés

    2015-01-01

    We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function using genetic algorithms. As a first application of the methodology, we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions

  10. Analytical optimal pulse shapes obtained with the aid of genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, Rubén D., E-mail: rdguerrerom@unal.edu.co [Department of Physics, Universidad Nacional de Colombia, Bogota (Colombia); Arango, Carlos A. [Department of Chemical Sciences, Universidad Icesi, Cali (Colombia); Reyes, Andrés [Department of Chemistry, Universidad Nacional de Colombia, Bogota (Colombia)

    2015-09-28

    We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function using genetic algorithms. As a first application of the methodology, we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.

  11. Intrinsic Dynamics of Quantum-Dash Lasers

    KAUST Repository

    Chen, Cheng; Djie, Hery Susanto; Hwang, James C. M.; Koch, Thomas L.; Lester, Luke F.; Ooi, Boon S.; Wang, Yang

    2011-01-01

    Temperature-dependent intrinsic modulation response of InAs/InAlGaAs quantum-dash lasers was investigated by using pulse optical injection modulation to minimize the effects of parasitics and self-heating. Compared to typical quantum-well lasers, the quantum-dash lasers were found to have comparable differential gain but approximately twice the gain compression factor, probably due to carrier heating by free-carrier absorption, as opposed to stimulated transition. Therefore, the narrower modulation bandwidth of the quantum-dash lasers than that of quantum-well lasers was attributed to their higher gain compression factor. In addition, as expected, quantum-dash lasers with relatively long and uniform dashes exhibit higher temperature stability than quantum-well lasers. However, the lasers with relatively short and nonuniform dashes exhibit stronger temperature dependence, probably due to their higher surface-to-volume ratio and nonuniform dash sizes. © 2011 IEEE.

  12. Intrinsic Dynamics of Quantum-Dash Lasers

    KAUST Repository

    Chen, Cheng

    2011-10-01

    Temperature-dependent intrinsic modulation response of InAs/InAlGaAs quantum-dash lasers was investigated by using pulse optical injection modulation to minimize the effects of parasitics and self-heating. Compared to typical quantum-well lasers, the quantum-dash lasers were found to have comparable differential gain but approximately twice the gain compression factor, probably due to carrier heating by free-carrier absorption, as opposed to stimulated transition. Therefore, the narrower modulation bandwidth of the quantum-dash lasers than that of quantum-well lasers was attributed to their higher gain compression factor. In addition, as expected, quantum-dash lasers with relatively long and uniform dashes exhibit higher temperature stability than quantum-well lasers. However, the lasers with relatively short and nonuniform dashes exhibit stronger temperature dependence, probably due to their higher surface-to-volume ratio and nonuniform dash sizes. © 2011 IEEE.

  13. Quantum key distribution with two-segment quantum repeaters

    Energy Technology Data Exchange (ETDEWEB)

    Kampermann, Hermann; Abruzzo, Silvestre; Bruss, Dagmar [Theoretische Physik III, Heinrich-Heine-Universitaet Duesseldorf (Germany)

    2014-07-01

    Quantum repeaters represent one possible way to achieve long-distance quantum key distribution. One way of improving the repeater rate and decreasing the memory coherence time is the usage of multiplexing. Motivated by the experimental fact that long-range connections are practically demanding, we extend the analysis of the quantum repeater multiplexing protocol to the case of short-range connections. We derive formulas for the repeater rate and we show that short-range connections lead to most of the benefits of a full-range multiplexing protocol. A less demanding QKD-protocol without quantum memories was recently introduced by Lo et al. We generalize this measurement-device-independent quantum key Distribution protocol to the scenario where the repeater Station contains also heralded quantum memories. We assume either single-photon sources or weak coherent pulse sources plus decay states. We show that it is possible to significantly outperform the original proposal, even in presence of decoherence of the quantum memory. We give formulas in terms of device imperfections i.e., the quantum bit error rate and the repeater rate.

  14. Quantum optics

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, P D [University of Queensland, St. Lucia, QLD (Australia).Physics Department

    1999-07-01

    Full text: Quantum optics in Australia has been an active research field for some years. I shall focus on recent developments in quantum and atom optics. Generally, the field as a whole is becoming more and more diverse, as technological developments drive experiments into new areas, and theorists either attempt to explain the new features, or else develop models for even more exotic ideas. The recent developments include quantum solitons, quantum computing, Bose-Einstein condensation, atom lasers, quantum cryptography, and novel tests of quantum mechanics. The talk will briefly cover current progress and outstanding problems in each of these areas. Copyright (1999) Australian Optical Society.

  15. Steering population transfer of the Na2 molecule by an ultrashort pulse train

    Science.gov (United States)

    Niu, Dong-Hua; Wang, Shuo; Zhan, Wei-Shen; Tao, Hong-Cai; Wang, Si-Qi

    2018-05-01

    We theoretically investigate the complete population transfer among quantum states of the Na2 molecule using ultrashort pulse trains using the time-dependent wave packet method. The population accumulation of the target state can be steered by controlling the laser parameters, such as the variable pulse pairs, the different pulse widths, the time delays and the repetition period between two contiguous pulses; in particular, the pulse pairs and the pulse widths have a great effect on the population transfer. The calculations show that the ultrashort pulse train is a feasible solution, which can steer the population transfer from the initial state to the target state efficiently with lower peak intensities.

  16. Observation of quantum Zeno effect in a superconducting flux qubit

    International Nuclear Information System (INIS)

    Kakuyanagi, K; Baba, T; Matsuzaki, Y; Nakano, H; Saito, S; Semba, K

    2015-01-01

    When a quantum state is subjected to frequent measurements, the time evolution of the quantum state is frozen. This is called the quantum Zeno effect. Here, we observe such an effect by performing frequent discrete measurements in a macroscopic quantum system, a superconducting quantum bit. The quantum Zeno effect induced by discrete measurements is similar to the original idea of the quantum Zeno effect. By using a Josephson bifurcation amplifier pulse readout, we have experimentally suppressed the time evolution of Rabi oscillation using projective measurements, and also observed the enhancement of the quantum state holding time by shortening the measurement period time. This is a crucial step to realize quantum information processing using the quantum Zeno effect. (papers)

  17. Quantum entanglement and quantum teleportation

    International Nuclear Information System (INIS)

    Shih, Y.H.

    2001-01-01

    One of the most surprising consequences of quantum mechanics is the entanglement of two or more distance particles. The ''ghost'' interference and the ''ghost'' image experiments demonstrated the astonishing nonlocal behavior of an entangled photon pair. Even though we still have questions in regard to fundamental issues of the entangled quantum systems, quantum entanglement has started to play important roles in quantum information and quantum computation. Quantum teleportation is one of the hot topics. We have demonstrated a quantum teleportation experiment recently. The experimental results proved the working principle of irreversibly teleporting an unknown arbitrary quantum state from one system to another distant system by disassembling into and then later reconstructing from purely classical information and nonclassical EPR correlations. The distinct feature of this experiment is that the complete set of Bell states can be distinguished in the Bell state measurement. Teleportation of a quantum state can thus occur with certainty in principle. (orig.)

  18. Multiplicative properties of quantum channels

    Science.gov (United States)

    Rahaman, Mizanur

    2017-08-01

    In this paper, we study the multiplicative behaviour of quantum channels, mathematically described by trace preserving, completely positive maps on matrix algebras. It turns out that the multiplicative domain of a unital quantum channel has a close connection to its spectral properties. A structure theorem (theorem 2.5), which reveals the automorphic property of an arbitrary unital quantum channel on a subalgebra, is presented. Various classes of quantum channels (irreducible, primitive, etc) are then analysed in terms of this stabilising subalgebra. The notion of the multiplicative index of a unital quantum channel is introduced, which measures the number of times a unital channel needs to be composed with itself for the multiplicative algebra to stabilise. We show that the maps that have trivial multiplicative domains are dense in completely bounded norm topology in the set of all unital completely positive maps. Some applications in quantum information theory are discussed.

  19. Molecular quantum control landscapes in von Neumann time-frequency phase space

    Science.gov (United States)

    Ruetzel, Stefan; Stolzenberger, Christoph; Fechner, Susanne; Dimler, Frank; Brixner, Tobias; Tannor, David J.

    2010-10-01

    Recently we introduced the von Neumann representation as a joint time-frequency description for femtosecond laser pulses and suggested its use as a basis for pulse shaping experiments. Here we use the von Neumann basis to represent multidimensional molecular control landscapes, providing insight into the molecular dynamics. We present three kinds of time-frequency phase space scanning procedures based on the von Neumann formalism: variation of intensity, time-frequency phase space position, and/or the relative phase of single subpulses. The shaped pulses produced are characterized via Fourier-transform spectral interferometry. Quantum control is demonstrated on the laser dye IR140 elucidating a time-frequency pump-dump mechanism.

  20. Practical continuous-variable quantum key distribution without finite sampling bandwidth effects.

    Science.gov (United States)

    Li, Huasheng; Wang, Chao; Huang, Peng; Huang, Duan; Wang, Tao; Zeng, Guihua

    2016-09-05

    In a practical continuous-variable quantum key distribution system, finite sampling bandwidth of the employed analog-to-digital converter at the receiver's side may lead to inaccurate results of pulse peak sampling. Then, errors in the parameters estimation resulted. Subsequently, the system performance decreases and security loopholes are exposed to eavesdroppers. In this paper, we propose a novel data acquisition scheme which consists of two parts, i.e., a dynamic delay adjusting module and a statistical power feedback-control algorithm. The proposed scheme may improve dramatically the data acquisition precision of pulse peak sampling and remove the finite sampling bandwidth effects. Moreover, the optimal peak sampling position of a pulse signal can be dynamically calibrated through monitoring the change of the statistical power of the sampled data in the proposed scheme. This helps to resist against some practical attacks, such as the well-known local oscillator calibration attack.

  1. Quantum logic using correlated one-dimensional quantum walks

    Science.gov (United States)

    Lahini, Yoav; Steinbrecher, Gregory R.; Bookatz, Adam D.; Englund, Dirk

    2018-01-01

    Quantum Walks are unitary processes describing the evolution of an initially localized wavefunction on a lattice potential. The complexity of the dynamics increases significantly when several indistinguishable quantum walkers propagate on the same lattice simultaneously, as these develop non-trivial spatial correlations that depend on the particle's quantum statistics, mutual interactions, initial positions, and the lattice potential. We show that even in the simplest case of a quantum walk on a one dimensional graph, these correlations can be shaped to yield a complete set of compact quantum logic operations. We provide detailed recipes for implementing quantum logic on one-dimensional quantum walks in two general cases. For non-interacting bosons—such as photons in waveguide lattices—we find high-fidelity probabilistic quantum gates that could be integrated into linear optics quantum computation schemes. For interacting quantum-walkers on a one-dimensional lattice—a situation that has recently been demonstrated using ultra-cold atoms—we find deterministic logic operations that are universal for quantum information processing. The suggested implementation requires minimal resources and a level of control that is within reach using recently demonstrated techniques. Further work is required to address error-correction.

  2. Relationship between quantum walks and relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Chandrashekar, C. M.; Banerjee, Subhashish; Srikanth, R.

    2010-01-01

    Quantum walk models have been used as an algorithmic tool for quantum computation and to describe various physical processes. This article revisits the relationship between relativistic quantum mechanics and the quantum walks. We show the similarities of the mathematical structure of the decoupled and coupled forms of the discrete-time quantum walk to that of the Klein-Gordon and Dirac equations, respectively. In the latter case, the coin emerges as an analog of the spinor degree of freedom. Discrete-time quantum walk as a coupled form of the continuous-time quantum walk is also shown by transforming the decoupled form of the discrete-time quantum walk to the Schroedinger form. By showing the coin to be a means to make the walk reversible and that the Dirac-like structure is a consequence of the coin use, our work suggests that the relativistic causal structure is a consequence of conservation of information. However, decoherence (modeled by projective measurements on position space) generates entropy that increases with time, making the walk irreversible and thereby producing an arrow of time. The Lieb-Robinson bound is used to highlight the causal structure of the quantum walk to put in perspective the relativistic structure of the quantum walk, the maximum speed of walk propagation, and earlier findings related to the finite spread of the walk probability distribution. We also present a two-dimensional quantum walk model on a two-state system to which the study can be extended.

  3. Quantum robots and quantum computers

    Energy Technology Data Exchange (ETDEWEB)

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  4. Quantum computers and quantum computations

    International Nuclear Information System (INIS)

    Valiev, Kamil' A

    2005-01-01

    This review outlines the principles of operation of quantum computers and their elements. The theory of ideal computers that do not interact with the environment and are immune to quantum decohering processes is presented. Decohering processes in quantum computers are investigated. The review considers methods for correcting quantum computing errors arising from the decoherence of the state of the quantum computer, as well as possible methods for the suppression of the decohering processes. A brief enumeration of proposed quantum computer realizations concludes the review. (reviews of topical problems)

  5. A single-atom quantum memory.

    Science.gov (United States)

    Specht, Holger P; Nölleke, Christian; Reiserer, Andreas; Uphoff, Manuel; Figueroa, Eden; Ritter, Stephan; Rempe, Gerhard

    2011-05-12

    The faithful storage of a quantum bit (qubit) of light is essential for long-distance quantum communication, quantum networking and distributed quantum computing. The required optical quantum memory must be able to receive and recreate the photonic qubit; additionally, it must store an unknown quantum state of light better than any classical device. So far, these two requirements have been met only by ensembles of material particles that store the information in collective excitations. Recent developments, however, have paved the way for an approach in which the information exchange occurs between single quanta of light and matter. This single-particle approach allows the material qubit to be addressed, which has fundamental advantages for realistic implementations. First, it enables a heralding mechanism that signals the successful storage of a photon by means of state detection; this can be used to combat inevitable losses and finite efficiencies. Second, it allows for individual qubit manipulations, opening up avenues for in situ processing of the stored quantum information. Here we demonstrate the most fundamental implementation of such a quantum memory, by mapping arbitrary polarization states of light into and out of a single atom trapped inside an optical cavity. The memory performance is tested with weak coherent pulses and analysed using full quantum process tomography. The average fidelity is measured to be 93%, and low decoherence rates result in qubit coherence times exceeding 180  microseconds. This makes our system a versatile quantum node with excellent prospects for applications in optical quantum gates and quantum repeaters.

  6. Quantum entanglement and position-momentum entropic squeezing of a moving Lambda-type three-level atom interacting with a single-mode quantized field with intensity-dependent coupling

    Science.gov (United States)

    Faghihi, M. J.; Tavassoly, M. K.

    2013-07-01

    In this paper, we study the interaction between a moving Λ-type three-level atom and a single-mode cavity field in the presence of intensity-dependent atom-field coupling. After obtaining the state vector of the entire system explicitly, we study the nonclassical features of the system such as quantum entanglement, position-momentum entropic squeezing, quadrature squeezing and sub-Poissonian statistics. According to the obtained numerical results we illustrate that the squeezed period, the duration of entropy squeezing and the maximal squeezing can be controlled by choosing the appropriate nonlinearity function together with entering the atomic motion effect by the suitable selection of the field-mode structure parameter. Also, the atomic motion, as well as the nonlinearity function, leads to the oscillatory behaviour of the degree of entanglement between the atom and field.

  7. Multiparty Quantum Secret Sharing of Quantum States Using Entanglement States

    International Nuclear Information System (INIS)

    Ying, Guo; Da-Zu, Huang; Gui-Hua, Zeng; Ho, Lee Moon

    2008-01-01

    A multi-partite-controlled quantum secret sharing scheme using several non-orthogonal entanglement states is presented with unconditional security. In this scheme, the participants share the secret quantum state by exchanging the secret polarization angles of the disordered travel particles. The security of the secret quantum state is also guaranteed by the non-orthogonal multi-partite-controlled entanglement states, the participants' secret polarizations, and the disorder of the travelling particles. Moreover, the present scheme is secure against the particle-number splitting attack and the intercept-and-resend attack. It may be still secure even if the distributed quantum state is embedded in a not-so-weak coherent-state pulse

  8. Preservation of quantum states via a super-Zeno effect on ensemble quantum computers

    International Nuclear Information System (INIS)

    Ting-Ting, Ren; Jun, Luo; Xian-Ping, Sun; Ming-Sheng, Zhan

    2009-01-01

    Following a recent proposal by Dhar et al (2006 Phys. Rev. Lett. 96 100405), we demonstrate experimentally the preservation of quantum states in a two-qubit system based on a super-Zeno effect using liquid-state nuclear magnetic resonance techniques. Using inverting radiofrequency pulses and delicately selecting time intervals between two pulses, we suppress the effect of decoherence of quantum states. We observe that preservation of the quantum state |11) with the super-Zeno effect is three times more efficient than the ordinary one with the standard Zeno effect. (general)

  9. Quantum mystery

    CERN Document Server

    Chanda, Rajat

    1997-01-01

    The book discusses the laws of quantum mechanics, several amazing quantum phenomena and some recent progress in understanding the connection between the quantum and the classical worlds. We show how paradoxes arise and how to resolve them. The significance of Bell's theorem and the remarkable experimental results on particle correlations are described in some detail. Finally, the current status of our understanding of quantum theory is summerised.

  10. Galois quantum systems

    International Nuclear Information System (INIS)

    Vourdas, A

    2005-01-01

    A finite quantum system in which the position and momentum take values in the Galois field GF(p l ) is constructed from a smaller quantum system in which the position and momentum take values in Z p , using field extension. The Galois trace is used in the definition of the Fourier transform. The Heisenberg-Weyl group of displacements and the Sp(2, GF(p l )) group of symplectic transformations are studied. A class of transformations inspired by the Frobenius maps in Galois fields is introduced. The relationship of this 'Galois quantum system' with its subsystems in which the position and momentum take values in subfields of GF(p l ) is discussed

  11. Method for pulse to pulse dose reproducibility applied to electron linear accelerators

    International Nuclear Information System (INIS)

    Ighigeanu, D.; Martin, D.; Oproiu, C.; Cirstea, E.; Craciun, G.

    2002-01-01

    An original method for obtaining programmed beam single shots and pulse trains with programmed pulse number, pulse repetition frequency, pulse duration and pulse dose is presented. It is particularly useful for automatic control of absorbed dose rate level, irradiation process control as well as in pulse radiolysis studies, single pulse dose measurement or for research experiments where pulse-to-pulse dose reproducibility is required. This method is applied to the electron linear accelerators, ALIN-10 of 6.23 MeV and 82 W and ALID-7, of 5.5 MeV and 670 W, built in NILPRP. In order to implement this method, the accelerator triggering system (ATS) consists of two branches: the gun branch and the magnetron branch. ATS, which synchronizes all the system units, delivers trigger pulses at a programmed repetition rate (up to 250 pulses/s) to the gun (80 kV, 10 A and 4 ms) and magnetron (45 kV, 100 A, and 4 ms).The accelerated electron beam existence is determined by the electron gun and magnetron pulses overlapping. The method consists in controlling the overlapping of pulses in order to deliver the beam in the desired sequence. This control is implemented by a discrete pulse position modulation of gun and/or magnetron pulses. The instabilities of the gun and magnetron transient regimes are avoided by operating the accelerator with no accelerated beam for a certain time. At the operator 'beam start' command, the ATS controls electron gun and magnetron pulses overlapping and the linac beam is generated. The pulse-to-pulse absorbed dose variation is thus considerably reduced. Programmed absorbed dose, irradiation time, beam pulse number or other external events may interrupt the coincidence between the gun and magnetron pulses. Slow absorbed dose variation is compensated by the control of the pulse duration and repetition frequency. Two methods are reported in the electron linear accelerators' development for obtaining the pulse to pulse dose reproducibility: the method

  12. Quantum criticality.

    Science.gov (United States)

    Coleman, Piers; Schofield, Andrew J

    2005-01-20

    As we mark the centenary of Albert Einstein's seminal contribution to both quantum mechanics and special relativity, we approach another anniversary--that of Einstein's foundation of the quantum theory of solids. But 100 years on, the same experimental measurement that puzzled Einstein and his contemporaries is forcing us to question our understanding of how quantum matter transforms at ultra-low temperatures.

  13. Quantum Computing

    Indian Academy of Sciences (India)

    In the first part of this article, we had looked at how quantum physics can be harnessed to make the building blocks of a quantum computer. In this concluding part, we look at algorithms which can exploit the power of this computational device, and some practical difficulties in building such a device. Quantum Algorithms.

  14. I, Quantum Robot: Quantum Mind control on a Quantum Computer

    OpenAIRE

    Zizzi, Paola

    2008-01-01

    The logic which describes quantum robots is not orthodox quantum logic, but a deductive calculus which reproduces the quantum tasks (computational processes, and actions) taking into account quantum superposition and quantum entanglement. A way toward the realization of intelligent quantum robots is to adopt a quantum metalanguage to control quantum robots. A physical implementation of a quantum metalanguage might be the use of coherent states in brain signals.

  15. PULSE Pilot Certification Results

    Directory of Open Access Journals (Sweden)

    Pamela Pape-Lindstrom

    2015-08-01

    Full Text Available The pilot certification process is an ambitious, nationwide endeavor designed to motivate important changes in life sciences education that are in line with the recommendations of the 2011 Vision and Change Report: A Call to Action (American Association for the Advancement of Science [AAAS], 2011.  It is the goal of the certification process to acknowledge departments that have progressed towards full implementation of the tenets of Vision and Change and to motivate departments that have not begun to adopt the recommendations to consider doing so.  More than 70 life science departments applied to be part of the pilot certification process, funded by a National Science Foundation grant, and eight were selected based on initial evidence of transformed and innovative educational practices.  The programs chosen represent a wide variety of schools, including two-year colleges, liberal-arts institutions, regional comprehensive colleges, research universities and minority serving institutions.  Outcomes from this pilot were released June 1, 2015 (www.pulsecommunity.org, with all eight programs being recognized as having progressed along a continuum of change.  Five levels of achievement were defined as PULSE Pilot Progression Levels.  Of the eight departments in the pilot, one achieved “PULSE Progression Level III: Accomplished”.  Six departments achieved “PULSE Progression Level II: Developing” and one pilot department achieved “PULSE Progression Level I: Beginning”.  All of the schools have made significant movement towards the recommendations of Vision and Change relative to a traditional life sciences curriculum.  Overall, the response from the eight pilot schools has been positive

  16. Quantum Logic and Quantum Reconstruction

    OpenAIRE

    Stairs, Allen

    2015-01-01

    Quantum logic understood as a reconstruction program had real successes and genuine limitations. This paper offers a synopsis of both and suggests a way of seeing quantum logic in a larger, still thriving context.

  17. Quantum dynamics of quantum bits

    International Nuclear Information System (INIS)

    Nguyen, Bich Ha

    2011-01-01

    The theory of coherent oscillations of the matrix elements of the density matrix of the two-state system as a quantum bit is presented. Different calculation methods are elaborated in the case of a free quantum bit. Then the most appropriate methods are applied to the study of the density matrices of the quantum bits interacting with a classical pumping radiation field as well as with the quantum electromagnetic field in a single-mode microcavity. The theory of decoherence of a quantum bit in Markovian approximation is presented. The decoherence of a quantum bit interacting with monoenergetic photons in a microcavity is also discussed. The content of the present work can be considered as an introduction to the study of the quantum dynamics of quantum bits. (review)

  18. Quantum sense and nonsense

    CERN Document Server

    Bricmont, Jean

    2017-01-01

    Permeated by the author's delightful humor, this little book explains, with nearly no mathematics, the main conceptual issues associated with quantum mechanics:  The issue of determinism. Does quantum mechanics signify the end of a deterministic word-view?  The role of the human subject or of the "observer" in science. Since Copernicus, science has increasingly tended to dethrone Man from his formerly held special position in the Universe. But quantum mechanics, with its emphasis on the notion of observation, may once more have given a central role to the human subject.  The issue of locality. Does quantum mechanics imply that instantaneous actions at a distance exist in Nature? In these pages the author offers a variety of views and answers - bad as well as good - to these questions. The reader will be both entertained and enlightened by Jean Bricmont's clear and incisive arguments.

  19. Quantum imaging technologies

    International Nuclear Information System (INIS)

    Malik, M.; Boyd, R.W.

    2014-01-01

    Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging that encompasses technologies such as quantum lithography, quantum ghost imaging, and high-dimensional quantum key distribution (QKD). The emergence of such quantum technologies also highlights the need for the development of accurate and efficient methods of measuring and characterizing the elusive quantum state itself. In this paper, we describe new technologies that use the quantum properties of light for security. The first of these is a technique that extends the principles behind QKD to the field of imaging and optical ranging. By applying the polarization-based BB84 protocol to individual photons in an active imaging system, we obtained images that are secure against any interceptresend jamming attacks. The second technology presented in this article is based on an extension of quantum ghost imaging, a technique that uses position-momentum entangled photons to create an image of an object without directly obtaining any spatial information from it. We used a holographic filtering technique to build a quantum ghost image identification system that uses a few pairs of photons to identify an object from a set of known objects. The third technology addressed in this document is a high-dimensional QKD system that uses orbital-angular-momentum (OAM) modes of light for encoding. Moving to a high-dimensional state space in QKD allows one to impress more information on each photon, as well as introduce higher levels of security. We discuss the development of two OAM-QKD protocols based on the BB84 and Ekert protocols of QKD. The fourth and final technology presented in this article is a relatively new technique called direct measurement that uses sequential weak and strong measurements to characterize a quantum state

  20. 2D quantum gravity from quantum entanglement.

    Science.gov (United States)

    Gliozzi, F

    2011-01-21

    In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

  1. Propagation delay of femtosecond pulses in an optical amplifier

    DEFF Research Database (Denmark)

    Poel, Mike van der; Mørk, Jesper; Hvam, Jørn Märcher

    of 2.6 THz, through a quantum-dot (QD) semiconductor amplifier (SOA) at room temperature. This extremely large bandwidth, on the other hand, is at the cost of a rather small group index change of ?ng=4*10-3. We have performed two types of femtosecond pulse slow-down and advancement experiments....... In the first experiment, we prepare a narrow peak or dip in the SOA gain spectrum by injection of a strong pump pulse4. The resulting dispersion feature is then probed by a weak pulse. In the second experiment, we measure self-slowdown or advancement as pulse energy isincreased5. In both cases, we perform...

  2. Quantum frames

    Science.gov (United States)

    Brown, Matthew J.

    2014-02-01

    The framework of quantum frames can help unravel some of the interpretive difficulties i the foundation of quantum mechanics. In this paper, I begin by tracing the origins of this concept in Bohr's discussion of quantum theory and his theory of complementarity. Engaging with various interpreters and followers of Bohr, I argue that the correct account of quantum frames must be extended beyond literal space-time reference frames to frames defined by relations between a quantum system and the exosystem or external physical frame, of which measurement contexts are a particularly important example. This approach provides superior solutions to key EPR-type measurement and locality paradoxes.

  3. Quantum Darwinism

    Science.gov (United States)

    Zurek, Wojciech Hubert

    2009-03-01

    Quantum Darwinism describes the proliferation, in the environment, of multiple records of selected states of a quantum system. It explains how the quantum fragility of a state of a single quantum system can lead to the classical robustness of states in their correlated multitude; shows how effective `wave-packet collapse' arises as a result of the proliferation throughout the environment of imprints of the state of the system; and provides a framework for the derivation of Born's rule, which relates the probabilities of detecting states to their amplitudes. Taken together, these three advances mark considerable progress towards settling the quantum measurement problem.

  4. Quantum equations from Brownian motions

    International Nuclear Information System (INIS)

    Rajput, B.S.

    2011-01-01

    Classical Schrodinger and Dirac equations have been derived from Brownian motions of a particle, it has been shown that the classical Schrodinger equation can be transformed to usual Schrodinger Quantum equation on applying Heisenberg uncertainty principle between position and momentum while Dirac Quantum equation follows it's classical counter part on applying Heisenberg uncertainly principle between energy and time without applying any analytical continuation. (author)

  5. Quantum dots

    International Nuclear Information System (INIS)

    Kouwenhoven, L.; Marcus, C.

    1998-01-01

    Quantum dots are man-made ''droplets'' of charge that can contain anything from a single electron to a collection of several thousand. Their typical dimensions range from nanometres to a few microns, and their size, shape and interactions can be precisely controlled through the use of advanced nanofabrication technology. The physics of quantum dots shows many parallels with the behaviour of naturally occurring quantum systems in atomic and nuclear physics. Indeed, quantum dots exemplify an important trend in condensed-matter physics in which researchers study man-made objects rather than real atoms or nuclei. As in an atom, the energy levels in a quantum dot become quantized due to the confinement of electrons. With quantum dots, however, an experimentalist can scan through the entire periodic table by simply changing a voltage. In this article the authors describe how quantum dots make it possible to explore new physics in regimes that cannot otherwise be accessed in the laboratory. (UK)

  6. Electromagnetically induced transparency with matched pulses

    International Nuclear Information System (INIS)

    Harris, S.E.

    1993-01-01

    In the last several years there have been studies and experiments showing how, by applying an additional laser beam, optically-thick transitions may be rendered nearly transparent to probing radiation. This transparency results from a quantum interference, very much like a Fano interference, which is established by the additional laser. This talk describes the difference between the quantum interference as exhibited by an independent atom and by an optically-thick ensemble of atoms. We find that an ensemble of atoms establishes transparency through a strong nonlinear interaction which, for a lambda system, tends to generate a matching temporal envelope on the complementary transition. For a ladder system, phase conjugate pulses are generated and, after a characteristic distance, establish transparency. The transparency of an optically-thick medium is therefore not a Beer's law superposition of the independent atom response. To transmit a pulse through an otherwise opaque media, the front edge of the complementary pulse should lead, in the manner of open-quotes counter-intuitiveclose quotes adiabatic transfer, the front edge of the pulse which is to be rendered transparent. Thereafter the pulses should be matched or, for a ladder system, phase-conjugately matched

  7. PUSPATI Triga Reactor pulsing parameters

    Energy Technology Data Exchange (ETDEWEB)

    Auu, Gui Ah; Abu, Puad Haji; Yunus, Yaziz [PUSPATI, Selangor (Malaysia)

    1984-06-01

    The pulsing experiment was carried out as part of the commissioning activites of PUSPATI TRIGA Reactor (PTR). Several parameters of PTR were deduced from the experiment. It was found that the maximum temperature of the fuel was far below the safety limit when the maximum allowable positive reactivity of $3.00 was inserted into the core. The peak power achieved was 1354 Mw.

  8. Quantum Phase Extraction in Isospectral Electronic Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Christopher

    2010-04-28

    Quantum phase is not a direct observable and is usually determined by interferometric methods. We present a method to map complete electron wave functions, including internal quantum phase information, from measured single-state probability densities. We harness the mathematical discovery of drum-like manifolds bearing different shapes but identical resonances, and construct quantum isospectral nanostructures possessing matching electronic structure but divergent physical structure. Quantum measurement (scanning tunneling microscopy) of these 'quantum drums' [degenerate two-dimensional electron states on the Cu(111) surface confined by individually positioned CO molecules] reveals that isospectrality provides an extra topological degree of freedom enabling robust quantum state transplantation and phase extraction.

  9. Quantum information. Teleporation - cryptography - quantum computer

    International Nuclear Information System (INIS)

    Breuer, Reinhard

    2010-01-01

    The following topics are dealt with: Reality in the test house, quantum teleportation, 100 years of quantum theory, the reality of quanta, interactionless quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view into the future of quantum optics. (HSI)

  10. Quantum symmetry in quantum theory

    International Nuclear Information System (INIS)

    Schomerus, V.

    1993-02-01

    Symmetry concepts have always been of great importance for physical problems like explicit calculations, classification or model building. More recently, new 'quantum symmetries' ((quasi) quantum groups) attracted much interest in quantum theory. It is shown that all these quantum symmetries permit a conventional formulation as symmetry in quantum mechanics. Symmetry transformations can act on the Hilbert space H of physical states such that the ground state is invariant and field operators transform covariantly. Models show that one must allow for 'truncation' in the tensor product of representations of a quantum symmetry. This means that the dimension of the tensor product of two representations of dimension σ 1 and σ 2 may be strictly smaller than σ 1 σ 2 . Consistency of the transformation law of field operators local braid relations leads us to expect, that (weak) quasi quantum groups are the most general symmetries in local quantum theory. The elements of the R-matrix which appears in these local braid relations turn out to be operators on H in general. It will be explained in detail how examples of field algebras with weak quasi quantum group symmetry can be obtained. Given a set of observable field with a finite number of superselection sectors, a quantum symmetry together with a complete set of covariant field operators which obey local braid relations are constructed. A covariant transformation law for adjoint fields is not automatic but will follow when the existence of an appropriate antipode is assumed. At the example of the chiral critical Ising model, non-uniqueness of the quantum symmetry will be demonstrated. Generalized quantum symmetries yield examples of gauge symmetries in non-commutative geometry. Quasi-quantum planes are introduced as the simplest examples of quasi-associative differential geometry. (Weak) quasi quantum groups can act on them by generalized derivations much as quantum groups do in non-commutative (differential-) geometry

  11. Spin gymnastics with selective radiofrequency pulses

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, R.; Kupce, E. [Cambridge Univ. (United Kingdom)

    1994-12-31

    Although high resolution NMR spectra are normally excited with short intense radiofrequency pulses, there is an entire family of new experiments that can be performed with frequency-selective or ``soft`` pulses. Time-consuming two-dimensional spectroscopy may be reduced to a much shorter one-dimensional version with much finer digitization in the frequency domain. A large number of soft pulses can be combined to form a ``polychromatic pulse`` that has uniform excitation over the entire range of proton shifts except for a rejection notch at the water frequency. Polychromatic pulses can also be used to create antiphase magnetization in preparation for a coherence transfer or double-quantum experiment. An excitation profile can be designed in the form of a ``template`` that exactly matches the spectrum of a given chemical compound but has zero excitation elsewhere. This is achieved by using the information in the experimental free induction decay to construct a suitable array of soft pulses that has the required excitation pattern. In this manner, interpenetrating spectra can be separated into the spectra of the pure components, for example those of a and b glucose. Selective Hartmann-Hahn coherence transfer experiments employ similar soft pulse techniques. If several such transfers are concatenated, the method may be used as a test to see whether a group of protons is linked in an unbroken chain by scalar spin-spin interactions. (authors). 24 refs., 18 figs.

  12. Simultaneous deterministic control of distant qubits in two semiconductor quantum dots.

    Science.gov (United States)

    Gamouras, A; Mathew, R; Freisem, S; Deppe, D G; Hall, K C

    2013-10-09

    In optimal quantum control (OQC), a target quantum state of matter is achieved by tailoring the phase and amplitude of the control Hamiltonian through femtosecond pulse-shaping techniques and powerful adaptive feedback algorithms. Motivated by recent applications of OQC in quantum information science as an approach to optimizing quantum gates in atomic and molecular systems, here we report the experimental implementation of OQC in a solid-state system consisting of distinguishable semiconductor quantum dots. We demonstrate simultaneous high-fidelity π and 2π single qubit gates in two different quantum dots using a single engineered infrared femtosecond pulse. These experiments enhance the scalability of semiconductor-based quantum hardware and lay the foundation for applications of pulse shaping to optimize quantum gates in other solid-state systems.

  13. Quantum random number generator based on quantum tunneling effect

    OpenAIRE

    Zhou, Haihan; Li, Junlin; Pan, Dong; Zhang, Weixing; Long, Guilu

    2017-01-01

    In this paper, we proposed an experimental implementation of quantum random number generator(QRNG) with inherent randomness of quantum tunneling effect of electrons. We exploited InGaAs/InP diodes, whose valance band and conduction band shared a quasi-constant energy barrier. We applied a bias voltage on the InGaAs/InP avalanche diode, which made the diode works under Geiger mode, and triggered the tunneling events with a periodic pulse. Finally, after data collection and post-processing, our...

  14. Reconfigurable optical implementation of quantum complex networks

    Science.gov (United States)

    Nokkala, J.; Arzani, F.; Galve, F.; Zambrini, R.; Maniscalco, S.; Piilo, J.; Treps, N.; Parigi, V.

    2018-05-01

    Network theory has played a dominant role in understanding the structure of complex systems and their dynamics. Recently, quantum complex networks, i.e. collections of quantum systems arranged in a non-regular topology, have been theoretically explored leading to significant progress in a multitude of diverse contexts including, e.g., quantum transport, open quantum systems, quantum communication, extreme violation of local realism, and quantum gravity theories. Despite important progress in several quantum platforms, the implementation of complex networks with arbitrary topology in quantum experiments is still a demanding task, especially if we require both a significant size of the network and the capability of generating arbitrary topology—from regular to any kind of non-trivial structure—in a single setup. Here we propose an all optical and reconfigurable implementation of quantum complex networks. The experimental proposal is based on optical frequency combs, parametric processes, pulse shaping and multimode measurements allowing the arbitrary control of the number of the nodes (optical modes) and topology of the links (interactions between the modes) within the network. Moreover, we also show how to simulate quantum dynamics within the network combined with the ability to address its individual nodes. To demonstrate the versatility of these features, we discuss the implementation of two recently proposed probing techniques for quantum complex networks and structured environments.

  15. Practical free space quantum cryptography

    International Nuclear Information System (INIS)

    Schmitt-Manderbach, T.; Weier, H.; Regner, N.; Kurtsiefer, C.; Weinfurter, H.

    2005-01-01

    Full text: Quantum cryptography, the secure key distribution between two parties, is the first practical application of quantum information technology. By encoding digital information into different polarization states of single photons, a string of key bits can be established between two parties, where laws of quantum mechanics ensure that a possible eavesdropper has negligible knowledge of. Having shown the feasibility of a long distance quantum key distribution scheme, the emphasis of this work is to incorporate the previously developed compact sender and receiver modules into a quantum cryptography system suitable for every-day use in metropolitan areas. The permanent installation with automatic alignment allows to investigate in detail the sensitivity of the free space optical link to weather conditions and air turbulences commonly encountered in urban areas. We report on a successful free space quantum cryptography experiment over a distance of 500 m between the rooftops of two university buildings using the BB84 protocol. The obtained bit error rates in first runs of this experiment using faint coherent pulses with an average photon number ranging from 0.1 to 1.0 was measured to be below 3 percent for experiments carried out during night, leading to average raw key rates (before error correction and privacy amplification) of 50 kBits per second. Thanks to its simplicity of implementation, our experiment brings free space quantum key distribution a big step closer to practical usability in metropolitan networks and on a level with fibre-based quantum cryptography that up to now offers the only ready-to-use systems available. Compact and automated free space hardware is also a prerequisite for a possible earth-satellite quantum key distribution system in order to break the distance limit of about 100 km of current quantum cryptography schemes. (author)

  16. Quantum information to the home

    Science.gov (United States)

    Choi, Iris; Young, Robert J.; Townsend, Paul D.

    2011-06-01

    Information encoded on individual quanta will play an important role in our future lives, much as classically encoded digital information does today. Combining quantum information carried by single photons with classical signals encoded on strong laser pulses in modern fibre-to-the-home (FTTH) networks is a significant challenge, the solution to which will facilitate the global distribution of quantum information to the home and with it a quantum internet [1]. In real-world networks, spontaneous Raman scattering in the optical fibre would induce crosstalk between the high-power classical channels and a single-photon quantum channel, such that the latter is unable to operate. Here, we show that the integration of quantum and classical information on an FTTH network is possible by performing quantum key distribution (QKD) on a network while simultaneously transferring realistic levels of classical data. Our novel scheme involves synchronously interleaving a channel of quantum data with the Raman scattered photons from a classical channel, exploiting the periodic minima in the instantaneous crosstalk and thereby enabling secure QKD to be performed.

  17. Quantum information to the home

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Iris; Young, Robert J; Townsend, Paul D, E-mail: paul.townsend@tyndall.ie [Photonic Systems Group, Tyndall National Institute and Department of Physics, University College Cork, Cork (Ireland)

    2011-06-15

    Information encoded on individual quanta will play an important role in our future lives, much as classically encoded digital information does today. Combining quantum information carried by single photons with classical signals encoded on strong laser pulses in modern fibre-to-the-home (FTTH) networks is a significant challenge, the solution to which will facilitate the global distribution of quantum information to the home and with it a quantum internet. In real-world networks, spontaneous Raman scattering in the optical fibre would induce crosstalk between the high-power classical channels and a single-photon quantum channel, such that the latter is unable to operate. Here, we show that the integration of quantum and classical information on an FTTH network is possible by performing quantum key distribution (QKD) on a network while simultaneously transferring realistic levels of classical data. Our novel scheme involves synchronously interleaving a channel of quantum data with the Raman scattered photons from a classical channel, exploiting the periodic minima in the instantaneous crosstalk and thereby enabling secure QKD to be performed.

  18. Quantum information to the home

    International Nuclear Information System (INIS)

    Choi, Iris; Young, Robert J; Townsend, Paul D

    2011-01-01

    Information encoded on individual quanta will play an important role in our future lives, much as classically encoded digital information does today. Combining quantum information carried by single photons with classical signals encoded on strong laser pulses in modern fibre-to-the-home (FTTH) networks is a significant challenge, the solution to which will facilitate the global distribution of quantum information to the home and with it a quantum internet. In real-world networks, spontaneous Raman scattering in the optical fibre would induce crosstalk between the high-power classical channels and a single-photon quantum channel, such that the latter is unable to operate. Here, we show that the integration of quantum and classical information on an FTTH network is possible by performing quantum key distribution (QKD) on a network while simultaneously transferring realistic levels of classical data. Our novel scheme involves synchronously interleaving a channel of quantum data with the Raman scattered photons from a classical channel, exploiting the periodic minima in the instantaneous crosstalk and thereby enabling secure QKD to be performed.

  19. Speeding up transmissions of unknown quantum information along Ising-type quantum channels

    International Nuclear Information System (INIS)

    Guo W J; Wei L F

    2017-01-01

    Quantum teleportation with entanglement channels and a series of two-qubit SWAP gates between the nearest-neighbor qubits are usually utilized to achieve the transfers of unknown quantum state from the sender to the distant receiver. In this paper, by simplifying the usual SWAP gates we propose an approach to speed up the transmissions of unknown quantum information, specifically including the single-qubit unknown state and two-qubit unknown entangled ones, by a series of entangling and disentangling operations between the remote qubits with distant interactions. The generic proposal is demonstrated specifically with experimentally-existing Ising-type quantum channels without transverse interaction; liquid NMR-molecules driven by global radio frequency electromagnetic pulses and capacitively-coupled Josephson circuits driven by local microwave pulses. The proposal should be particularly useful to set up the connections between the distant qubits in a chip of quantum computing. (paper)

  20. Efficient networks for quantum factoring

    International Nuclear Information System (INIS)

    Beckman, D.; Chari, A.N.; Devabhaktuni, S.; Preskill, J.

    1996-01-01

    We consider how to optimize memory use and computation time in operating a quantum computer. In particular, we estimate the number of memory quantum bits (qubits) and the number of operations required to perform factorization, using the algorithm suggested by Shor [in Proceedings of the 35th Annual Symposium on Foundations of Computer Science, edited by S. Goldwasser (IEEE Computer Society, Los Alamitos, CA, 1994), p. 124]. A K-bit number can be factored in time of order K 3 using a machine capable of storing 5K+1 qubits. Evaluation of the modular exponential function (the bottleneck of Shor close-quote s algorithm) could be achieved with about 72K 3 elementary quantum gates; implementation using a linear ion trap would require about 396K 3 laser pulses. A proof-of-principle demonstration of quantum factoring (factorization of 15) could be performed with only 6 trapped ions and 38 laser pulses. Though the ion trap may never be a useful computer, it will be a powerful device for exploring experimentally the properties of entangled quantum states. copyright 1996 The American Physical Society

  1. A quantum-rovibrational-state-selected study of the proton-transfer reaction H2+(X2Σ: v+ = 1-3; N+ = 0-3) + Ne → NeH+ + H using the pulsed field ionization-photoion method: observation of the rotational effect near the reaction threshold.

    Science.gov (United States)

    Xiong, Bo; Chang, Yih-Chung; Ng, Cheuk-Yiu

    2017-07-19

    Using the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully prepared H 2 + (X 2 Σ: v + = 1-3; N + = 0-5) ions in the form of an ion beam in single quantum-rovibrational-states with high purity, high intensity, and narrow laboratory kinetic energy spread (ΔE lab ≈ 0.05 eV). This VUV-PFI-PI ion source, when coupled with the double-quadrupole double-octupole ion-molecule reaction apparatus, has made possible a systematic examination of the vibrational- as well as rotational-state effects on the proton transfer reaction of H 2 + (X 2 Σ: v + ; N + ) + Ne. Here, we present the integral cross sections [σ(v + ; N + )'s] for the H 2 + (v + = 1-3; N + = 0-3) + Ne → NeH + + H reaction observed in the center-of-mass kinetic energy (E cm ) range of 0.05-2.00 eV. The σ(v + = 1, N + = 1) exhibits a distinct E cm onset, which is found to agree with the endothermicity of 0.27 eV for the proton transfer process after taking into account of experimental uncertainties. Strong v + -vibrational enhancements are observed for σ(v + = 1-3, N + ) in the E cm range of 0.05-2.00 eV. While rotational excitations appear to have little effect on σ(v + = 3, N + ), a careful search leads to the observation of moderate N + -rotational enhancements at v + = 2: σ(v + = 2; N + = 0) quantum dynamics predictions. We hope that these new experimental results would further motivate more rigorous theoretical calculations on the dynamics of this prototypical ion-molecule reaction.

  2. Fixed points of quantum operations

    International Nuclear Information System (INIS)

    Arias, A.; Gheondea, A.; Gudder, S.

    2002-01-01

    Quantum operations frequently occur in quantum measurement theory, quantum probability, quantum computation, and quantum information theory. If an operator A is invariant under a quantum operation φ, we call A a φ-fixed point. Physically, the φ-fixed points are the operators that are not disturbed by the action of φ. Our main purpose is to answer the following question. If A is a φ-fixed point, is A compatible with the operation elements of φ? We shall show in general that the answer is no and we shall give some sufficient conditions under which the answer is yes. Our results will follow from some general theorems concerning completely positive maps and injectivity of operator systems and von Neumann algebras

  3. Random pulse generator

    International Nuclear Information System (INIS)

    Guo Ya'nan; Jin Dapeng; Zhao Dixin; Liu Zhen'an; Qiao Qiao; Chinese Academy of Sciences, Beijing

    2007-01-01

    Due to the randomness of radioactive decay and nuclear reaction, the signals from detectors are random in time. But normal pulse generator generates periodical pulses. To measure the performances of nuclear electronic devices under random inputs, a random generator is necessary. Types of random pulse generator are reviewed, 2 digital random pulse generators are introduced. (authors)

  4. Complex characterization of short-pulse propagation through InAs/InP quantum-dash optical amplifiers: From the quasi-linear to the two-photon-dominated regime

    DEFF Research Database (Denmark)

    Capua, Amir; Saal, Abigael; Karni, Ouri

    2012-01-01

    We describe direct measurements at a high temporal resolution of the changes experienced by the phase and amplitude of an ultra-short pulse upon propagation through an inhomogenously broadened semiconductor nanostructured optical gain medium. Using a cross frequency-resolved optical gating techni...

  5. Multi-party Semi-quantum Key Agreement with Delegating Quantum Computation

    Science.gov (United States)

    Liu, Wen-Jie; Chen, Zhen-Yu; Ji, Sai; Wang, Hai-Bin; Zhang, Jun

    2017-10-01

    A multi-party semi-quantum key agreement (SQKA) protocol based on delegating quantum computation (DQC) model is proposed by taking Bell states as quantum resources. In the proposed protocol, the participants only need the ability of accessing quantum channel and preparing single photons {|0〉, |1〉, |+〉, |-〉}, while the complicated quantum operations, such as the unitary operations and Bell measurement, will be delegated to the remote quantum center. Compared with previous quantum key agreement protocols, this client-server model is more feasible in the early days of the emergence of quantum computers. In order to prevent the attacks from outside eavesdroppers, inner participants and quantum center, two single photon sequences are randomly inserted into Bell states: the first sequence is used to perform the quantum channel detection, while the second is applied to disorder the positions of message qubits, which guarantees the security of the protocol.

  6. Programmable pulse generator

    International Nuclear Information System (INIS)

    Xue Zhihua; Lou Binqiao; Duan Xiaohui

    2002-01-01

    The author introduces the design of programmable pulse generator that is based on a micro-controller and controlled by RS232 interface of personal computer. The whole system has good stability. The pulse generator can produce TTL pulse and analog pulse. The pulse frequency can be selected by EPLD. The voltage amplitude and pulse width of analog pulse can be adjusted by analog switches and digitally-controlled potentiometers. The software development tools of computer is National Instruments LabView5.1. The front panel of this virtual instrumentation is intuitive and easy-to-use. Parameters can be selected and changed conveniently by knob and slide

  7. Quantum games as quantum types

    Science.gov (United States)

    Delbecque, Yannick

    In this thesis, we present a new model for higher-order quantum programming languages. The proposed model is an adaptation of the probabilistic game semantics developed by Danos and Harmer [DH02]: we expand it with quantum strategies which enable one to represent quantum states and quantum operations. Some of the basic properties of these strategies are established and then used to construct denotational semantics for three quantum programming languages. The first of these languages is a formalisation of the measurement calculus proposed by Danos et al. [DKP07]. The other two are new: they are higher-order quantum programming languages. Previous attempts to define a denotational semantics for higher-order quantum programming languages have failed. We identify some of the key reasons for this and base the design of our higher-order languages on these observations. The game semantics proposed in this thesis is the first denotational semantics for a lambda-calculus equipped with quantum types and with extra operations which allow one to program quantum algorithms. The results presented validate the two different approaches used in the design of these two new higher-order languages: a first one where quantum states are used through references and a second one where they are introduced as constants in the language. The quantum strategies presented in this thesis allow one to understand the constraints that must be imposed on quantum type systems with higher-order types. The most significant constraint is the fact that abstraction over part of the tensor product of many unknown quantum states must not be allowed. Quantum strategies are a new mathematical model which describes the interaction between classical and quantum data using system-environment dialogues. The interactions between the different parts of a quantum system are described using the rich structure generated by composition of strategies. This approach has enough generality to be put in relation with other

  8. Upconversion-based receivers for quantum hacking-resistant quantum key distribution

    Science.gov (United States)

    Jain, Nitin; Kanter, Gregory S.

    2016-07-01

    We propose a novel upconversion (sum frequency generation)-based quantum-optical system design that can be employed as a receiver (Bob) in practical quantum key distribution systems. The pump governing the upconversion process is produced and utilized inside the physical receiver, making its access or control unrealistic for an external adversary (Eve). This pump facilitates several properties which permit Bob to define and control the modes that can participate in the quantum measurement. Furthermore, by manipulating and monitoring the characteristics of the pump pulses, Bob can detect a wide range of quantum hacking attacks launched by Eve.

  9. From quantum transitions to electronic motions

    Science.gov (United States)

    Krausz, Ferenc

    2017-01-01

    Laser spectroscopy and chromoscopy permit precision measurement of quantum transitions and captures atomic-scale dynamics, respectively. Frequency- and time-domain metrology ranks among the supreme laser disciplines in fundamental science. For decades, these fields evolved independently, without interaction and synergy between them. This has changed profoundly with controlling the position of the equidistant frequency spikes of a mode-locked laser oscillator. By the self-referencing technique invented by Theodor Hänsch, the comb can be coherently linked to microwaves and used for precision measurements of energy differences between quantum states. The resultant optical frequency synthesis has revolutionized precision spectroscopy. Locking the comb lines to the resonator round-trip frequency by the same approach has given rise to laser pulses with controlled field oscillations. This article reviews, from a personal perspective, how the bridge between frequency- and time-resolved metrology emerged on the turn of the millennium and how synthesized several-cycle laser fields have been instrumental in establishing the basic tools and techniques for attosecond science.

  10. Quantum measurement

    CERN Document Server

    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....

  11. Quantum Optics

    CERN Document Server

    Walls, D F

    2007-01-01

    Quantum Optics gives a comprehensive coverage of developments in quantum optics over the past years. In the early chapters the formalism of quantum optics is elucidated and the main techniques are introduced. These are applied in the later chapters to problems such as squeezed states of light, resonance fluorescence, laser theory, quantum theory of four-wave mixing, quantum non-demolition measurements, Bell's inequalities, and atom optics. Experimental results are used to illustrate the theory throughout. This yields the most comprehensive and up-to-date coverage of experiment and theory in quantum optics in any textbook. More than 40 exercises helps readers test their understanding and provide practice in quantitative problem solving.

  12. Quantum gravity

    International Nuclear Information System (INIS)

    Markov, M.A.; West, P.C.

    1984-01-01

    This book discusses the state of the art of quantum gravity, quantum effects in cosmology, quantum black-hole physics, recent developments in supergravity, and quantum gauge theories. Topics considered include the problems of general relativity, pregeometry, complete cosmological theories, quantum fluctuations in cosmology and galaxy formation, a new inflationary universe scenario, grand unified phase transitions and the early Universe, the generalized second law of thermodynamics, vacuum polarization near black holes, the relativity of vacuum, black hole evaporations and their cosmological consequences, currents in supersymmetric theories, the Kaluza-Klein theories, gauge algebra and quantization, and twistor theory. This volume constitutes the proceedings of the Second Seminar on Quantum Gravity held in Moscow in 1981

  13. Quantum Capacity under Adversarial Quantum Noise: Arbitrarily Varying Quantum Channels

    Science.gov (United States)

    Ahlswede, Rudolf; Bjelaković, Igor; Boche, Holger; Nötzel, Janis

    2013-01-01

    We investigate entanglement transmission over an unknown channel in the presence of a third party (called the adversary), which is enabled to choose the channel from a given set of memoryless but non-stationary channels without informing the legitimate sender and receiver about the particular choice that he made. This channel model is called an arbitrarily varying quantum channel (AVQC). We derive a quantum version of Ahlswede's dichotomy for classical arbitrarily varying channels. This includes a regularized formula for the common randomness-assisted capacity for entanglement transmission of an AVQC. Quite surprisingly and in contrast to the classical analog of the problem involving the maximal and average error probability, we find that the capacity for entanglement transmission of an AVQC always equals its strong subspace transmission capacity. These results are accompanied by different notions of symmetrizability (zero-capacity conditions) as well as by conditions for an AVQC to have a capacity described by a single-letter formula. In the final part of the paper the capacity of the erasure-AVQC is computed and some light shed on the connection between AVQCs and zero-error capacities. Additionally, we show by entirely elementary and operational arguments motivated by the theory of AVQCs that the quantum, classical, and entanglement-assisted zero-error capacities of quantum channels are generically zero and are discontinuous at every positivity point.

  14. Synchronization in Quantum Key Distribution Systems

    Directory of Open Access Journals (Sweden)

    Anton Pljonkin

    2017-10-01

    Full Text Available In the description of quantum key distribution systems, much attention is paid to the operation of quantum cryptography protocols. The main problem is the insufficient study of the synchronization process of quantum key distribution systems. This paper contains a general description of quantum cryptography principles. A two-line fiber-optic quantum key distribution system with phase coding of photon states in transceiver and coding station synchronization mode was examined. A quantum key distribution system was built on the basis of the scheme with automatic compensation of polarization mode distortions. Single-photon avalanche diodes were used as optical radiation detecting devices. It was estimated how the parameters used in quantum key distribution systems of optical detectors affect the detection of the time frame with attenuated optical pulse in synchronization mode with respect to its probabilistic and time-domain characteristics. A design method was given for the process that detects the time frame that includes an optical pulse during synchronization. This paper describes the main quantum communication channel attack methods by removing a portion of optical emission. This paper describes the developed synchronization algorithm that takes into account the time required to restore the photodetector’s operation state after the photon has been registered during synchronization. The computer simulation results of the developed synchronization algorithm were analyzed. The efficiency of the developed algorithm with respect to synchronization process protection from unauthorized gathering of optical emission is demonstrated herein.

  15. Superadiabatic holonomic quantum computation in cavity QED

    Science.gov (United States)

    Liu, Bao-Jie; Huang, Zhen-Hua; Xue, Zheng-Yuan; Zhang, Xin-Ding

    2017-06-01

    Adiabatic quantum control is a powerful tool for quantum engineering and a key component in some quantum computation models, where accurate control over the timing of the involved pulses is not needed. However, the adiabatic condition requires that the process be very slow and thus limits its application in quantum computation, where quantum gates are preferred to be fast due to the limited coherent times of the quantum systems. Here, we propose a feasible scheme to implement universal holonomic quantum computation based on non-Abelian geometric phases with superadiabatic quantum control, where the adiabatic manipulation is sped up while retaining its robustness against errors in the timing control. Consolidating the advantages of both strategies, our proposal is thus both robust and fast. The cavity QED system is adopted as a typical example to illustrate the merits where the proposed scheme can be realized in a tripod configuration by appropriately controlling the pulse shapes and their relative strength. To demonstrate the distinct performance of our proposal, we also compare our scheme with the conventional adiabatic strategy.

  16. Quantum Locality?

    OpenAIRE

    Stapp, Henry P.

    2011-01-01

    Robert Griffiths has recently addressed, within the framework of a 'consistent quantum theory' that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues that the putative proofs of this property that involve hidden variables include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. O...

  17. Quantum ratchets

    OpenAIRE

    Grifoni, Milena

    1997-01-01

    In this thesis, ratchet systems operating in the quantum regime are investigated. Ratchet systems, also known as Brownian motors, are periodic systems presenting an intrinsic asymmetry which can be exploited to extract work out of unbiased forces. As a model for ratchet systems, we consider the motion of a particle in a one-dimensional periodic and asymmetric potential, interacting with a thermal environment, and subject to an unbiased driving force. In quantum ratchets, intrinsic quantum flu...

  18. Quantum space and quantum completeness

    Science.gov (United States)

    Jurić, Tajron

    2018-05-01

    Motivated by the question whether quantum gravity can "smear out" the classical singularity we analyze a certain quantum space and its quantum-mechanical completeness. Classical singularity is understood as a geodesic incompleteness, while quantum completeness requires a unique unitary time evolution for test fields propagating on an underlying background. Here the crucial point is that quantum completeness renders the Hamiltonian (or spatial part of the wave operator) to be essentially self-adjoint in order to generate a unique time evolution. We examine a model of quantum space which consists of a noncommutative BTZ black hole probed by a test scalar field. We show that the quantum gravity (noncommutative) effect is to enlarge the domain of BTZ parameters for which the relevant wave operator is essentially self-adjoint. This means that the corresponding quantum space is quantum complete for a larger range of BTZ parameters rendering the conclusion that in the quantum space one observes the effect of "smearing out" the singularity.

  19. Correlated nuclear and electronic dynamics in photoionized systems studied by quantum and mixed quantum-classical approaches

    International Nuclear Information System (INIS)

    Li, Zheng

    2014-09-01

    The advent of free electron lasers and high harmonic sources enables the investigation of electronic and nuclear dynamics of molecules and solids with atomic spatial resolution and femtosecond/attosecond time resolution, using bright and ultrashort laser pulses of frequency from terahertz to hard x-ray range. With the help of ultrashort laser pulses, the nuclear and electronic dynamics can be initiated, monitored and actively controlled at the typical time scale in the femtosecond to attosecond realm. Meanwhile, theoretical tools are required to describe the underlying mechanism. This doctoral thesis focuses on the development of theoretical tools based on full quantum mechanical multiconfiguration time-dependent Hartree (MCTDH) and mixed quantum classical approaches, which can be applied to describe the dynamical behavior of gas phase molecules and strongly correlated solids in the presence of ultrashort laser pulses. In the first part of this thesis, the focus is on the motion of electron holes in gas phase molecular ions created by extreme ultraviolet (XUV) photoionization and watched by spectroscopic approaches. The XUV photons create electron-hole in the valence orbitals of molecules by photoionization, the electron hole, as a positively charged quasi-particle, can then interact with the nuclei and the rest of electrons, leading to coupled non-Born-Oppenheimer dynamics. I present our study on electron-hole relaxation dynamics in valence ionized molecular ions of moderate size, using quantum wave packet and mixed quantum-classical approaches, using photoionized [H + (H 2 O) n ] + molecular ion as example. We have shown that the coupled motion of the electron-hole and the nuclei can be mapped out with femtosecond resolution by core-level x-ray transient absorption spectroscopy. Furthermore, in specific cases, the XUV photon can create a coherent electron hole, that can maintain its coherence to time scales of ∝ 1 picosecond. Employing XUV pump - IR probe

  20. Quantum mechanics

    International Nuclear Information System (INIS)

    Basdevant, J.L.; Dalibard, J.; Joffre, M.

    2008-01-01

    All physics is quantum from elementary particles to stars and to the big-bang via semi-conductors and chemistry. This theory is very subtle and we are not able to explain it without the help of mathematic tools. This book presents the principles of quantum mechanics and describes its mathematical formalism (wave function, Schroedinger equation, quantum operators, spin, Hamiltonians, collisions,..). We find numerous applications in the fields of new technologies (maser, quantum computer, cryptography,..) and in astrophysics. A series of about 90 exercises with their answers is included. This book is based on a physics course at a graduate level. (A.C.)

  1. Quantum information

    International Nuclear Information System (INIS)

    Rodgers, P.

    1998-01-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  2. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, P

    1998-03-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  3. Quantum computation

    International Nuclear Information System (INIS)

    Deutsch, D.

    1992-01-01

    As computers become ever more complex, they inevitably become smaller. This leads to a need for components which are fabricated and operate on increasingly smaller size scales. Quantum theory is already taken into account in microelectronics design. This article explores how quantum theory will need to be incorporated into computers in future in order to give them their components functionality. Computation tasks which depend on quantum effects will become possible. Physicists may have to reconsider their perspective on computation in the light of understanding developed in connection with universal quantum computers. (UK)

  4. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, P

    1998-03-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  5. Quantum Dots

    Science.gov (United States)

    Tartakovskii, Alexander

    2012-07-01

    Part I. Nanostructure Design and Structural Properties of Epitaxially Grown Quantum Dots and Nanowires: 1. Growth of III/V semiconductor quantum dots C. Schneider, S. Hofling and A. Forchel; 2. Single semiconductor quantum dots in nanowires: growth, optics, and devices M. E. Reimer, N. Akopian, M. Barkelid, G. Bulgarini, R. Heeres, M. Hocevar, B. J. Witek, E. Bakkers and V. Zwiller; 3. Atomic scale analysis of self-assembled quantum dots by cross-sectional scanning tunneling microscopy and atom probe tomography J. G. Keizer and P. M. Koenraad; Part II. Manipulation of Individual Quantum States in Quantum Dots Using Optical Techniques: 4. Studies of the hole spin in self-assembled quantum dots using optical techniques B. D. Gerardot and R. J. Warburton; 5. Resonance fluorescence from a single quantum dot A. N. Vamivakas, C. Matthiesen, Y. Zhao, C.-Y. Lu and M. Atature; 6. Coherent control of quantum dot excitons using ultra-fast optical techniques A. J. Ramsay and A. M. Fox; 7. Optical probing of holes in quantum dot molecules: structure, symmetry, and spin M. F. Doty and J. I. Climente; Part III. Optical Properties of Quantum Dots in Photonic Cavities and Plasmon-Coupled Dots: 8. Deterministic light-matter coupling using single quantum dots P. Senellart; 9. Quantum dots in photonic crystal cavities A. Faraon, D. Englund, I. Fushman, A. Majumdar and J. Vukovic; 10. Photon statistics in quantum dot micropillar emission M. Asmann and M. Bayer; 11. Nanoplasmonics with colloidal quantum dots V. Temnov and U. Woggon; Part IV. Quantum Dot Nano-Laboratory: Magnetic Ions and Nuclear Spins in a Dot: 12. Dynamics and optical control of an individual Mn spin in a quantum dot L. Besombes, C. Le Gall, H. Boukari and H. Mariette; 13. Optical spectroscopy of InAs/GaAs quantum dots doped with a single Mn atom O. Krebs and A. Lemaitre; 14. Nuclear spin effects in quantum dot optics B. Urbaszek, B. Eble, T. Amand and X. Marie; Part V. Electron Transport in Quantum Dots Fabricated by

  6. Pulsed water jet generated by pulse multiplication

    Czech Academy of Sciences Publication Activity Database

    Dvorský, R.; Sitek, Libor; Sochor, T.

    2016-01-01

    Roč. 23, č. 4 (2016), s. 959-967 ISSN 1330-3651 R&D Projects: GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : high- pressure pulses * pulse intensifier * pulsed water jet * water hammer effect Subject RIV: JQ - Machines ; Tools Impact factor: 0.723, year: 2016 http://hrcak.srce.hr/163752?lang=en

  7. Vector pulsing soliton of self-induced transparency in waveguide

    International Nuclear Information System (INIS)

    Adamashvili, G.T.

    2015-01-01

    A theory of an optical resonance vector pulsing soliton in waveguide is developed. A thin transition layer containing semiconductor quantum dots forms the boundary between the waveguide and one of the connected media. Analytical and numerical solutions for the optical vector pulsing soliton in waveguide are obtained. The vector pulsing soliton in the presence of excitonic and bi-excitonic excitations is compared with the soliton for waveguide TM-modes with parameters that can be used in modern optical experiments. It is shown that these nonlinear waves have significantly different parameters and shapes. - Highlights: • An optical vector pulsing soliton in a planar waveguide is presented. • Explicit form of the optical vector pulsing soliton are obtained. • The vector pulsing soliton and the soliton have different parameters and profiles

  8. Quantum Strategies and Local Operations

    Science.gov (United States)

    Gutoski, Gus

    2010-02-01

    This thesis is divided into two parts. In Part I we introduce a new formalism for quantum strategies, which specify the actions of one party in any multi-party interaction involving the exchange of multiple quantum messages among the parties. This formalism associates with each strategy a single positive semidefinite operator acting only upon the tensor product of the input and output message spaces for the strategy. We establish three fundamental properties of this new representation for quantum strategies and we list several applications, including a quantum version of von Neumann's celebrated 1928 Min-Max Theorem for zero-sum games and an efficient algorithm for computing the value of such a game. In Part II we establish several properties of a class of quantum operations that can be implemented locally with shared quantum entanglement or classical randomness. In particular, we establish the existence of a ball of local operations with shared randomness lying within the space spanned by the no-signaling operations and centred at the completely noisy channel. The existence of this ball is employed to prove that the weak membership problem for local operations with shared entanglement is strongly NP-hard. We also provide characterizations of local operations in terms of linear functionals that are positive and "completely" positive on a certain cone of Hermitian operators, under a natural notion of complete positivity appropriate to that cone. We end the thesis with a discussion of the properties of no-signaling quantum operations.

  9. Laser-pulsed relativistic electron gun

    International Nuclear Information System (INIS)

    Sherman, N.K.

    1986-01-01

    A relativistic (β ≅ 0.8) electron gun with good emittance and subnanosecond pulse duration which can be synchronized to picosecond laser pulses is being developed at NRC for use in studies of particle acceleration by lasers. Bursts of electron pulses exceeding 280 keV in energy have been extracted into air form a laser-driven vacuum photodiode. Trains of 5 ps pulses of ultraviolet UV light illuminate a magnesium cathode. Photoelectrons emitted from the cathode are accelerated in a graded electrostatic potential set up by a 360 kV Marx-generator. The UV pulses are obtained by doubling the frequency of a 606 nm dye laser modelocked at 160 MHz. Electron energies were measured by residual range in an echelon of Al foils. Total charge per burst was measured by picoammeter. Time structure of the bursts has been examined with plastic scintillator and a fast photomultiplier. Tests on a low voltage photodiode achieved a current density of 180 A/cm/sup 2/ from an Mg cathode, with quantum efficiency of 2.4 x 10/sup -6/ electron per UV photon. The brevity and intensity of the laser pulses cause the electric charge collected per pulse to increase linearly with bias voltage rather than according to the Langmuir-Child law. Gun emittance is about 150 mm-msr and beam brightness is about 1A/cm/sup 2/-sr. Estimated duration of individual electron pulses of a burst is about 400 ps with instantaneous current of about 0.1 mA. Energy spread within one pulse is expected to be about 15%. This gun has the potential to be a useful source of relativistic electrons for laser acceleration studies

  10. Highly Supersonic Ion Pulses in a Collisionless Magnetized Plasma

    DEFF Research Database (Denmark)

    Juul Rasmussen, Jens; Schrittwieser, R.

    1982-01-01

    The initial transient response of a collisionless plasma to a high positive voltage step is investigated. Four different pulses are observed. An electron plasma wave pulse is followed by an ion burst. The latter is overtaken and absorbed by a highly supersonic ion pulse. Thereafter, an ion...

  11. Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses

    DEFF Research Database (Denmark)

    Hansen, Jonas Lerche; Holmegaard, Lotte; Kalhøj, Line

    2011-01-01

    are quantum-state selected using a deflector and three-dimensionally (3D) aligned and oriented adiabatically using an elliptically polarized laser pulse in combination with a static electric field. A characteristic splitting in the molecular frame photoelectron momentum distribution reveals the position...... of the nodal planes of the molecular orbitals from which ionization occurs. The experimental results are supported by a theoretical tunneling model that includes and quantifies the splitting in the momentum distribution. The focus of the present article is to understand strong-field ionization from 3D...

  12. Application of quantum key distribution for mutual identification - experimental realization

    International Nuclear Information System (INIS)

    Dusek, M.; Haderka, O.; Hendrych, M.

    1998-01-01

    A secure quantum identification system combining a classical identification procedure and quantum key distribution is proposed. Each identification sequence is always used just once and new sequences are 're fuelled' from a shared secret key transferred over a quantum channel. The question of authentication of information sent over a public channel is discussed. An apparatus using two unbalanced Mach-Zehnder interferometers has been built, and quantum key distribution and 'quantum identification' have been successfully tested through a single-mode optical fibre at 830 nm, employing low intensity coherent states (below 0,1 photons per pulse). (author)

  13. QUANTUM AND CLASSICAL CORRELATIONS IN GAUSSIAN OPEN QUANTUM SYSTEMS

    Directory of Open Access Journals (Sweden)

    Aurelian ISAR

    2015-01-01

    Full Text Available In the framework of the theory of open systems based on completely positive quantum dynamical semigroups, we give a description of the continuous-variable quantum correlations (quantum entanglement and quantum discord for a system consisting of two noninteracting bosonic modes embedded in a thermal environment. We solve the Kossakowski-Lindblad master equation for the time evolution of the considered system and describe the entanglement and discord in terms of the covariance matrix for Gaussian input states. For all values of the temperature of the thermal reservoir, an initial separable Gaussian state remains separable for all times. We study the time evolution of logarithmic negativity, which characterizes the degree of entanglement, and show that in the case of an entangled initial squeezed thermal state, entanglement suppression takes place for all temperatures of the environment, including zero temperature. We analyze the time evolution of the Gaussian quantum discord, which is a measure of all quantum correlations in the bipartite state, including entanglement, and show that it decays asymptotically in time under the effect of the thermal bath. This is in contrast with the sudden death of entanglement. Before the suppression of the entanglement, the qualitative evolution of quantum discord is very similar to that of the entanglement. We describe also the time evolution of the degree of classical correlations and of quantum mutual information, which measures the total correlations of the quantum system.

  14. Practical pulse engineering: Gradient ascent without matrix exponentiation

    Science.gov (United States)

    Bhole, Gaurav; Jones, Jonathan A.

    2018-06-01

    Since 2005, there has been a huge growth in the use of engineered control pulses to perform desired quantum operations in systems such as nuclear magnetic resonance quantum information processors. These approaches, which build on the original gradient ascent pulse engineering algorithm, remain computationally intensive because of the need to calculate matrix exponentials for each time step in the control pulse. In this study, we discuss how the propagators for each time step can be approximated using the Trotter-Suzuki formula, and a further speedup achieved by avoiding unnecessary operations. The resulting procedure can provide substantial speed gain with negligible costs in the propagator error, providing a more practical approach to pulse engineering.

  15. General solution to inhomogeneous dephasing and smooth pulse dynamical decoupling

    Science.gov (United States)

    Zeng, Junkai; Deng, Xiu-Hao; Russo, Antonio; Barnes, Edwin

    2018-03-01

    In order to achieve the high-fidelity quantum control needed for a broad range of quantum information technologies, reducing the effects of noise and system inhomogeneities is an essential task. It is well known that a system can be decoupled from noise or made insensitive to inhomogeneous dephasing dynamically by using carefully designed pulse sequences based on square or delta-function waveforms such as Hahn spin echo or CPMG. However, such ideal pulses are often challenging to implement experimentally with high fidelity. Here, we uncover a new geometrical framework for visualizing all possible driving fields, which enables one to generate an unlimited number of smooth, experimentally feasible pulses that perform dynamical decoupling or dynamically corrected gates to arbitrarily high order. We demonstrate that this scheme can significantly enhance the fidelity of single-qubit operations in the presence of noise and when realistic limitations on pulse rise times and amplitudes are taken into account.

  16. Channel's Concurrence and Quantum Teleportation

    Institute of Scientific and Technical Information of China (English)

    LING Yin-Sheng

    2005-01-01

    Concurrence can measure the entanglement property of a system. If the channel is a pure state, positive concurrence state can afford the good performance in the teleportation process. If the channel ia a mixed state, positive concurrence state cannot assure the good performance in the teleportation. The conditions of the positive concurrence and the quantum teleportation in the Heisenberg spin ring is derived.

  17. Quantum group and quantum symmetry

    International Nuclear Information System (INIS)

    Chang Zhe.

    1994-05-01

    This is a self-contained review on the theory of quantum group and its applications to modern physics. A brief introduction is given to the Yang-Baxter equation in integrable quantum field theory and lattice statistical physics. The quantum group is primarily introduced as a systematic method for solving the Yang-Baxter equation. Quantum group theory is presented within the framework of quantum double through quantizing Lie bi-algebra. Both the highest weight and the cyclic representations are investigated for the quantum group and emphasis is laid on the new features of representations for q being a root of unity. Quantum symmetries are explored in selected topics of modern physics. For a Hamiltonian system the quantum symmetry is an enlarged symmetry that maintains invariance of equations of motion and allows a deformation of the Hamiltonian and symplectic form. The configuration space of the integrable lattice model is analyzed in terms of the representation theory of quantum group. By means of constructing the Young operators of quantum group, the Schroedinger equation of the model is transformed to be a set of coupled linear equations that can be solved by the standard method. Quantum symmetry of the minimal model and the WZNW model in conformal field theory is a hidden symmetry expressed in terms of screened vertex operators, and has a deep interplay with the Virasoro algebra. In quantum group approach a complete description for vibrating and rotating diatomic molecules is given. The exact selection rules and wave functions are obtained. The Taylor expansion of the analytic formulas of the approach reproduces the famous Dunham expansion. (author). 133 refs, 20 figs

  18. Quantum information. Teleportation - cryptography - quantum computer

    International Nuclear Information System (INIS)

    Koenneker, Carsten

    2012-01-01

    The following topics are dealt with: Reality in the test facility, quantum teleportation, the reality of quanta, interaction-free quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view in the future of quantum optics. (HSI)

  19. Interaction between two stopped light pulses

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yi-Hsin, E-mail: yhchen920@gmail.com; Lee, Meng-Jung, E-mail: yhchen920@gmail.com; Hung, Weilun, E-mail: yhchen920@gmail.com; Yu, Ite A., E-mail: yu@phys.nthu.edu.tw [Department of Physics and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Ying-Cheng [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan and Department of Physics and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Yong-Fan [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2014-03-05

    The efficiency of a nonlinear optical process is proportional to the interaction time. We report a scheme of all-optical switching based on two motionless light pulses via the effect of electromagnetically induced transparency. One pulse was stopped as the stationary light pulse (SLP) and the other was stopped as stored light. The time of their interaction via the medium can be prolonged and, hence, the optical nonlinearity is greatly enhanced. Using a large optical density (OD) of 190, we achieved a very long interaction time of 6.9 μs. This can be analogous to the scheme of trapping light pulses by an optical cavity with a Q factor of 8×10{sup 9}. With the approach of using moving light pulses in the best situation, a switch can only be activated at 2 photons per atomic absorption cross section. With the approach of employing a SLP and a stored light pulse, a switch at only 0.56 photons was achieved and the efficiency is significantly improved. Moreover, the simulation results are in good agreement with the experimental data and show that the efficiency can be further improved by increasing the OD of the medium. Our work advances the technology in quantum information manipulation utilizing photons.

  20. Interaction between two stopped light pulses

    International Nuclear Information System (INIS)

    Chen, Yi-Hsin; Lee, Meng-Jung; Hung, Weilun; Yu, Ite A.; Chen, Ying-Cheng; Chen, Yong-Fan

    2014-01-01

    The efficiency of a nonlinear optical process is proportional to the interaction time. We report a scheme of all-optical switching based on two motionless light pulses via the effect of electromagnetically induced transparency. One pulse was stopped as the stationary light pulse (SLP) and the other was stopped as stored light. The time of their interaction via the medium can be prolonged and, hence, the optical nonlinearity is greatly enhanced. Using a large optical density (OD) of 190, we achieved a very long interaction time of 6.9 μs. This can be analogous to the scheme of trapping light pulses by an optical cavity with a Q factor of 8×10 9 . With the approach of using moving light pulses in the best situation, a switch can only be activated at 2 photons per atomic absorption cross section. With the approach of employing a SLP and a stored light pulse, a switch at only 0.56 photons was achieved and the efficiency is significantly improved. Moreover, the simulation results are in good agreement with the experimental data and show that the efficiency can be further improved by increasing the OD of the medium. Our work advances the technology in quantum information manipulation utilizing photons

  1. Quantum ensembles of quantum classifiers.

    Science.gov (United States)

    Schuld, Maria; Petruccione, Francesco

    2018-02-09

    Quantum machine learning witnesses an increasing amount of quantum algorithms for data-driven decision making, a problem with potential applications ranging from automated image recognition to medical diagnosis. Many of those algorithms are implementations of quantum classifiers, or models for the classification of data inputs with a quantum computer. Following the success of collective decision making with ensembles in classical machine learning, this paper introduces the concept of quantum ensembles of quantum classifiers. Creating the ensemble corresponds to a state preparation routine, after which the quantum classifiers are evaluated in parallel and their combined decision is accessed by a single-qubit measurement. This framework naturally allows for exponentially large ensembles in which - similar to Bayesian learning - the individual classifiers do not have to be trained. As an example, we analyse an exponentially large quantum ensemble in which each classifier is weighed according to its performance in classifying the training data, leading to new results for quantum as well as classical machine learning.

  2. Quantum computer games: quantum minesweeper

    Science.gov (United States)

    Gordon, Michal; Gordon, Goren

    2010-07-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical minesweeper the goal of the game is to discover all the mines laid out on a board without triggering them, in the quantum version there are several classical boards in superposition. The goal is to know the exact quantum state, i.e. the precise layout of all the mines in all the superposed classical boards. The player can perform three types of measurement: a classical measurement that probabilistically collapses the superposition; a quantum interaction-free measurement that can detect a mine without triggering it; and an entanglement measurement that provides non-local information. The application of the concepts taught by quantum minesweeper to one-way quantum computing are also presented.

  3. Quantum Physics Without Quantum Philosophy

    CERN Document Server

    Dürr, Detlef; Zanghì, Nino

    2013-01-01

    It has often been claimed that without drastic conceptual innovations a genuine explanation of quantum interference effects and quantum randomness is impossible. This book concerns Bohmian mechanics, a simple particle theory that is a counterexample to such claims. The gentle introduction and other contributions collected here show how the phenomena of non-relativistic quantum mechanics, from Heisenberg's uncertainty principle to non-commuting observables, emerge from the Bohmian motion of particles, the natural particle motion associated with Schrödinger's equation. This book will be of value to all students and researchers in physics with an interest in the meaning of quantum theory as well as to philosophers of science.

  4. Intersubunit distances in full-length, dimeric, bacterial phytochrome Agp1, as measured by pulsed electron-electron double resonance (PELDOR) between different spin label positions, remain unchanged upon photoconversion.

    Science.gov (United States)

    Kacprzak, Sylwia; Njimona, Ibrahim; Renz, Anja; Feng, Juan; Reijerse, Edward; Lubitz, Wolfgang; Krauss, Norbert; Scheerer, Patrick; Nagano, Soshichiro; Lamparter, Tilman; Weber, Stefan

    2017-05-05

    Bacterial phytochromes are dimeric light-regulated histidine kinases that convert red light into signaling events. Light absorption by the N-terminal photosensory core module (PCM) causes the proteins to switch between two spectrally distinct forms, Pr and Pfr, thus resulting in a conformational change that modulates the C-terminal histidine kinase region. To provide further insights into structural details of photoactivation, we investigated the full-length Agp1 bacteriophytochrome from the soil bacterium Agrobacterium fabrum using a combined spectroscopic and modeling approach. We generated seven mutants suitable for spin labeling to enable application of pulsed EPR techniques. The distances between attached spin labels were measured using pulsed electron-electron double resonance spectroscopy to probe the arrangement of the subunits within the dimer. We found very good agreement of experimental and calculated distances for the histidine-kinase region when both subunits are in a parallel orientation. However, experimental distance distributions surprisingly showed only limited agreement with either parallel- or antiparallel-arranged dimer structures when spin labels were placed into the PCM region. This observation indicates that the arrangements of the PCM subunits in the full-length protein dimer in solution differ significantly from that in the PCM crystals. The pulsed electron-electron double resonance data presented here revealed either no or only minor changes of distance distributions upon Pr-to-Pfr photoconversion. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  5. Few-cycle isolated attosecond pulses

    International Nuclear Information System (INIS)

    Sansone, G.; Benedetti, E.; Calegari, F.; Stagira, S.; Vozzi, C.; Silvestri De, S.; Nisoli, M.

    2006-01-01

    Complete test of publication follows. In the last few years the field of attosecond science has shown impressive and rapid progress, mainly due to the introduction of novel experimental methods for the characterization of extreme ultraviolet (XUV) pulses and attosecond electron wave packets. This development has been also triggered by significant improvements in the control of the electric field of the driving infrared pulses. Particularly interesting for the applications is the generation of isolated attosecond XUV pulses using few-cycle driving pulses. In this case significant progresses have been achieved thanks to the stabilization of the carrier-envelope phase (CEP) of amplified light pulses. In this work we demonstrate that the polarization gating (PG) method with few-cycle phase-stabilized driving pulses allows one to generate few-cycle isolated attosecond pulses tunable on a very broad spectral region. The PG method is based on temporal modulation of the ellipticity of a light pulse, which confines the XUV emission in the temporal gate where the polarization is close to linear. The time-dependent polarization of phase-stabilized sub-6-fs pulses, generated by the hollow fiber technique, has been obtained using two birefringent plates. It is possible to create a linear polarization gate, whose position is imposed by the intensity profile of the pulse whilst the emission time is linked to the CEP of the electric field. The pulses have been analyzed by using a flat-field spectrometer. Continuous XUV spectra, corresponding to the production of isolated attosecond pulses, have been generated for particular CEP values. Upon changing the rotation of the first plate it was possible to tune the XUV emission in a broad spectra range. We have then achieved a complete temporal characterization of the generated isolated attosecond pulses using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG CRAB). The measured parabolic phase

  6. Optical UWB pulse generator using an N tap microwave photonic filter and phase inversion adaptable to different pulse modulation formats.

    Science.gov (United States)

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2009-03-30

    We propose theoretically and demonstrate experimentally an optical architecture for flexible Ultra-Wideband pulse generation. It is based on an N-tap reconfigurable microwave photonic filter fed by a laser array by using phase inversion in a Mach-Zehnder modulator. Since a large number of positive and negative coefficients can be easily implemented, UWB pulses fitted to the FCC mask requirements can be generated. As an example, a four tap pulse generator is experimentally demonstrated which complies with the FCC regulation. The proposed pulse generator allows different pulse modulation formats since the amplitude, polarity and time delay of generated pulse is controlled.

  7. Laser pulse stacking method

    Science.gov (United States)

    Moses, E.I.

    1992-12-01

    A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.

  8. Quantum control of light using electromagnetically induced transparency

    International Nuclear Information System (INIS)

    Andre, A; Eisaman, M D; Walsworth, R L; Zibrov, A S; Lukin, M D

    2005-01-01

    We present an overview of recent theoretical and experimental work on the control of the propagation and quantum properties of light using electromagnetically induced transparency in atomic ensembles. Specifically, we discuss techniques for the generation and storage of few-photon quantum-mechanical states of light as well as novel approaches to manipulate weak pulses of light via enhanced nonlinear optical processes

  9. Some double resonance and multiple quantum NMR studies in solids

    Energy Technology Data Exchange (ETDEWEB)

    Wemmer, D.E.

    1978-08-01

    The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of /sup 13/C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D/sub 2/O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, ..delta..sigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO/sub 3/.D/sub 2/O, ..cap alpha..,..beta.. d-2 HMB and ..cap alpha..,..beta..,..gamma.. d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules ..delta..m = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made.

  10. Some double resonance and multiple quantum NMR studies in solids

    International Nuclear Information System (INIS)

    Wemmer, D.E.

    1978-08-01

    The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of 13 C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D 2 O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, Δsigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO 3 .D 2 O, α,β d-2 HMB and α,β,γ d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules Δm = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made

  11. Rydberg atoms ionization by microwave field and electromagnetic pulses

    International Nuclear Information System (INIS)

    Kaulakys, B.; Vilutis, G.

    1995-01-01

    A simple theory of the Rydberg atoms ionization by electromagnetic pulses and microwave field is presented. The analysis is based on the scale transformation which reduces the number of parameters and reveals the functional dependencies of the processes. It is shown that the observed ionization of Rydberg atoms by subpicosecond electromagnetic pulses scale classically. The threshold electric field required to ionise a Rydberg state may be simply evaluated in the photonic basis approach for the quantum dynamics or from the multiphoton ionization theory

  12. Quantum Computing

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 9. Quantum Computing - Building Blocks of a Quantum Computer. C S Vijay Vishal Gupta. General Article Volume 5 Issue 9 September 2000 pp 69-81. Fulltext. Click here to view fulltext PDF. Permanent link:

  13. Quantum spacetime

    International Nuclear Information System (INIS)

    Doplicher, S.

    1996-01-01

    We review some recent result and work in progress on the quantum structure of spacetime at scales comparable with the Planck length; the models discussed here are operationally motivated by the limitations in the accuracy of localization of events in spacetime imposed by the interplay between quantum mechanics and classical general relativity. (orig.)

  14. Pulse to pulse klystron diagnosis system

    International Nuclear Information System (INIS)

    Nowak, J.; Davidson, V.; Genova, L.; Johnson, R.; Reagan, D.

    1981-03-01

    This report describes a system used to study the behavior of SLAC high powered klystrons operating with a twice normal pulse width of 5 μs. At present, up to eight of the klystrons installed along the accelerator can be operated with long pulses and monitored by this system. The report will also discuss some of the recent findings and investigations

  15. Laser coherent control of quantum dynamics at the CSIR: NLC

    CSIR Research Space (South Africa)

    Botha, L

    2010-09-01

    Full Text Available reaction channels. The principle used is controlled interference of the quantum wave functions via time domain shaped ultra-short pulses. The time/frequency product of a pulse is a constant, determined by Heisenberg’s uncertainty principle, therefore, a...

  16. Decoherence control in quantum computing with simple chirped ...

    Indian Academy of Sciences (India)

    We show how the use of optimally shaped pulses to guide the time evolution of a system ('coherent control') can be an effective approach towards quantum computation logic. We demonstrate this with selective control of decoherence for a multilevel system with a simple linearly chirped pulse. We use a multiphoton ...

  17. Quantum photonics

    CERN Document Server

    Pearsall, Thomas P

    2017-01-01

    This textbook employs a pedagogical approach that facilitates access to the fundamentals of Quantum Photonics. It contains an introductory description of the quantum properties of photons through the second quantization of the electromagnetic field, introducing stimulated and spontaneous emission of photons at the quantum level. Schrödinger’s equation is used to describe the behavior of electrons in a one-dimensional potential. Tunneling through a barrier is used to introduce the concept of non­locality of an electron at the quantum level, which is closely-related to quantum confinement tunneling, resonant tunneling, and the origin of energy bands in both periodic (crystalline) and aperiodic (non-crystalline) materials. Introducing the concepts of reciprocal space, Brillouin zones, and Bloch’s theorem, the determination of electronic band structure using the pseudopotential method is presented, allowing direct computation of the band structures of most group IV, group III-V, and group II-VI semiconducto...

  18. Quantum cosmology

    International Nuclear Information System (INIS)

    Hawking, S.W.

    1984-01-01

    The subject of these lectures is quantum effects in cosmology. The author deals first with situations in which the gravitational field can be treated as a classical, unquantized background on which the quantum matter fields propagate. This is the case with inflation at the GUT era. Nevertheless the curvature of spacetime can have important effects on the behaviour of the quantum fields and on the development of long-range correlations. He then turns to the question of the quantization of the gravitational field itself. The plan of these lectures is as follows: Euclidean approach to quantum field theory in flat space; the extension of techniques to quantum fields on a curved background with the four-sphere, the Euclidean version of De Sitter space as a particular example; the GUT era; quantization of the gravitational field by Euclidean path integrals; mini superspace model. (Auth.)

  19. Quantum mechanics

    CERN Document Server

    Rae, Alastair I M

    2016-01-01

    A Thorough Update of One of the Most Highly Regarded Textbooks on Quantum Mechanics Continuing to offer an exceptionally clear, up-to-date treatment of the subject, Quantum Mechanics, Sixth Edition explains the concepts of quantum mechanics for undergraduate students in physics and related disciplines and provides the foundation necessary for other specialized courses. This sixth edition builds on its highly praised predecessors to make the text even more accessible to a wider audience. It is now divided into five parts that separately cover broad topics suitable for any general course on quantum mechanics. New to the Sixth Edition * Three chapters that review prerequisite physics and mathematics, laying out the notation, formalism, and physical basis necessary for the rest of the book * Short descriptions of numerous applications relevant to the physics discussed, giving students a brief look at what quantum mechanics has made possible industrially and scientifically * Additional end-of-chapter problems with...

  20. Quantum magnetism

    CERN Document Server

    Richter, Johannes; Farnell, Damian; Bishop, Raymod

    2004-01-01

    The investigation of magnetic systems where quantum effects play a dominant role has become a very active branch of solid-state-physics research in its own right. The first three chapters of the "Quantum Magnetism" survey conceptual problems and provide insights into the classes of systems considered, namely one-dimensional, two-dimensional and molecular magnets. The following chapters introduce the methods used in the field of quantum magnetism, including spin wave analysis, exact diagonalization, quantum field theory, coupled cluster methods and the Bethe ansatz. The book closes with a chapter on quantum phase transitions and a contribution that puts the wealth of phenomena into the context of experimental solid-state physics. Closing a gap in the literature, this volume is intended both as an introductory text at postgraduate level and as a modern, comprehensive reference for researchers in the field.