Geometric quenches in quantum integrable systems
Mossel, J.; Palacios, G.; Caux, J.S.
2010-01-01
We consider the generic problem of suddenly changing the geometry of an integrable, one-dimensional many-body quantum system. We show how the physics of an initial quantum state released into a bigger system can be completely described within the framework of the algebraic Bethe ansatz, by providing
Generalized thermalization for integrable system under quantum quench
Muralidharan, Sushruth; Shankaranarayanan, S
2016-01-01
We investigate equilibration and generalized thermalization of quantum Harmonic chain --- an integrable system which in the thermodynamic limit mimics a free scalar field --- under global quantum quench. The quench action we consider is connecting two disjoint harmonic chains of different sizes and the system jumps between two integrable settings. We verify the validity of the Generalized Gibbs Ensemble description for this system and also identify equilibration between the subsystems as in classical systems. Using Bogoliubov transformations, we show that the eigenstates of the system prior to the quench evolve towards the Gibbs Generalized Ensemble description. Further, through the phase space properties of a Generalized Gibbs Ensemble and the strength of stimulated emission, we identify the necessary criterion on the initial states for the thermalization at late times, which is satisfied by the system in the thermodynamic limit.
Quantum quenches during inflation
Carrilho, Pedro
2016-01-01
We propose a new technique to study fast transitions during inflation, by studying the dynamics of quantum quenches in an $O(N)$ scalar field theory in de Sitter spacetime. We compute the time evolution of the system using a non-perturbative large-$N$ limit approach. We derive the self-consistent mass equation for several physically relevant transitions of the parameters of the theory, in a slow motion approximation. Our computations reveal that the effective mass after the quench evolves in the direction of recovering its value before the quench, but stopping at a different asymptotic value, in which the mass is strictly positive. Furthermore, we tentatively find situations in which the effective mass can be temporarily negative, thus breaking the $O(N)$ symmetry of the system for a certain time, only to then come back to a positive value, restoring the symmetry. We argue the relevance of our new method in a cosmological scenario.
On the theory of quantum quenches in near-critical systems
Delfino, Gesualdo; Viti, Jacopo
2017-02-01
The theory of quantum quenches in near-critical one-dimensional systems formulated in Delfino (2014 J. Phys. A: Math. Theor. 402001) yields analytic predictions for the dynamics, unveils a qualitative difference between non-interacting and interacting systems, with undamped oscillations of one-point functions occurring only in the latter case, and explains the presence and role of different time scales. Here we examine additional aspects, determining in particular the relaxation value of one-point functions for small quenches. For a class of quenches we relate this value to the scaling dimensions of the operators. We argue that the E 8 spectrum of the Ising chain can be more accessible through a quench than at equilibrium, while for a quench of the plane anisotropy in the XYZ chain we obtain that the one-point function of the quench operator switches from damped to undamped oscillations at Δ =1/2 .
On the theory of quantum quenches in near-critical systems
Delfino, Gesualdo
2016-01-01
The theory of quantum quenches in near-critical one-dimensional systems formulated in [J. Phys. A 47 (2014) 402001] yields analytic predictions for the dynamics, unveils a qualitative difference between non-interacting and interacting systems, with undamped oscillations of one-point functions occurring only in the latter case, and explains the presence of different time scales. Here we examine additional aspects, obtaining in particular the expression for the relaxation value of one-point functions for small quenches. We argue that the $E_8$ spectrum of the Ising chain is more accessible through a quench than at equilibrium, while for a quench of the plane anisotropy in the XYZ chain we obtain that the one-point function of the quench operator switches from damped to undamped oscillations at $\\Delta=1/2$.
Universality in fast quantum quenches
Das, Sumit R; Myers, Robert C
2014-01-01
We expand on the investigation of the universal scaling properties in the early time behaviour of fast but smooth quantum quenches in a general $d$-dimensional conformal field theory deformed by a relevant operator of dimension $\\Delta$ with a time-dependent coupling. The quench consists of changing the coupling from an initial constant value $\\lambda_1$ by an amount of the order of $\\delta \\lambda$ to some other final value $\\lambda_2$, over a time scale $\\delta t$. In the fast quench limit where $\\delta t$ is smaller than all other length scales in the problem, $ \\delta t \\ll \\lambda_1^{1/(\\Delta-d)}, \\lambda_2^{1/(\\Delta-d)}, \\delta \\lambda^{1/(\\Delta-d)}$, the energy (density) injected into the system scales as $\\delta{\\cal E} \\sim (\\delta \\lambda)^2 (\\delta t)^{d-2\\Delta}$. Similarly, the change in the expectation value of the quenched operator at times earlier than the endpoint of the quench scales as $\\langle {\\cal O}_\\Delta\\rangle \\sim \\delta \\lambda\\, (\\delta t)^{d-2\\Delta}$, with further logarithmic...
Dworak, Lars; Reuss, Andreas J.; Zastrow, Marc; Rück-Braun, Karola; Wachtveitl, Josef
2014-11-01
A photochromic Förster resonance energy transfer (FRET) system was employed to disentangle the fluorescence quenching mechanisms in quantum dot/photochromic dye hybrids. In the off-state of the dye the main quenching mechanism is FRET whereas the moderate quenching in the on-state is due to non-FRET pathways opened up upon assembly.A photochromic Förster resonance energy transfer (FRET) system was employed to disentangle the fluorescence quenching mechanisms in quantum dot/photochromic dye hybrids. In the off-state of the dye the main quenching mechanism is FRET whereas the moderate quenching in the on-state is due to non-FRET pathways opened up upon assembly. Electronic supplementary information (ESI) available: QD and DTE synthesis, preparation of the DTE/QD coupled system, TEM image of the nanocrystals and experimental details. See DOI: 10.1039/c4nr05144k
Crossover physics in the nonequilibrium dynamics of quenched quantum impurity systems.
Vasseur, Romain; Trinh, Kien; Haas, Stephan; Saleur, Hubert
2013-06-14
A general framework is proposed to tackle analytically local quantum quenches in integrable impurity systems, combining a mapping onto a boundary problem with the form factor approach to boundary-condition-changing operators introduced by Lesage and Saleur [Phys. Rev. Lett. 80, 4370 (1998)]. We discuss how to compute exactly the following two central quantities of interest: the Loschmidt echo and the distribution of the work done during the quantum quench. Our results display an interesting crossover physics characterized by the energy scale T(b) of the impurity corresponding to the Kondo temperature. We discuss in detail the noninteracting case as a paradigm and benchmark for more complicated integrable impurity models and check our results using numerical methods.
Real-time evolution of quenched quantum systems
Energy Technology Data Exchange (ETDEWEB)
Moeckel, Michael
2009-06-24
Detailed geometries in heterostructures allow for nonequilibrium transport measurements in correlated systems, pump-probe experiments for time-resolved study of many-body relaxation in molecules and solids and ultracold atom gases loaded onto optical lattices for high control of system parameters in real time. In all of these fields of research the nonequilibrium properties of a Fermi liquid can be relevant. A first approach to their understanding is the main content of this thesis. At the beginning I collect a variety of nonequilibrium phenomena and introduce to basic questions and concepts for their study. The key observation of this thesis, namely a characteristic mismatch of expectation values in equilibrium and nonequilibrium, is first illustrated for the squeezed oscillator. Afterwards, these observations are generalized to a larger class of one-particle models. Then the nonequilibrium behavior of a Fermi liquid is examined by analyzing the Fermi liquid phase of the Hubbard model in more than one dimension. After a sudden switch-on of a weak two-particle interaction to the noninteracting Fermi gas the relaxation of the many-body system is observed. For this purpose, the flow equation transformation is implemented for the Hubbard Hamiltonian. Then the discussion of the momentum distribution function and of the kinetic energy displays a three-step relaxation behavior of the Fermi liquid from the initial perturbation until thermalization is reached. In order to extend the study of sudden switching to arbitrary switching processes the calculation is repeated using the Keldysh perturbation theory. (orig.)
Topological blocking in quantum quench dynamics
Kells, G.; Sen, D.; Slingerland, J. K.; Vishveshwara, S.
2014-06-01
We study the nonequilibrium dynamics of quenching through a quantum critical point in topological systems, focusing on one of their defining features: ground-state degeneracies and associated topological sectors. We present the notion of "topological blocking," experienced by the dynamics due to a mismatch in degeneracies between two phases, and we argue that the dynamic evolution of the quench depends strongly on the topological sector being probed. We demonstrate this interplay between quench and topology in models stemming from two extensively studied systems, the transverse Ising chain and the Kitaev honeycomb model. Through nonlocal maps of each of these systems, we effectively study spinless fermionic p-wave paired topological superconductors. Confining the systems to ring and toroidal geometries, respectively, enables us to cleanly address degeneracies, subtle issues of fermion occupation and parity, and mismatches between topological sectors. We show that various features of the quench, which are related to Kibble-Zurek physics, are sensitive to the topological sector being probed, in particular, the overlap between the time-evolved initial ground state and an appropriate low-energy state of the final Hamiltonian. While most of our study is confined to translationally invariant systems, where momentum is a convenient quantum number, we briefly consider the effect of disorder and illustrate how this can influence the quench in a qualitatively different way depending on the topological sector considered.
Simulating Zeno physics by a quantum quench with superconducting circuits
Tong, Qing-Jun; An, Jun-Hong; Kwek, L. C.; Luo, Hong-Gang; Oh, C. H.
2014-06-01
Studying out-of-equilibrium physics in quantum systems under quantum quench is of vast experimental and theoretical interest. Using periodic quantum quenches, we present an experimentally accessible scheme to simulate the quantum Zeno and anti-Zeno effects in an open quantum system of a single superconducting qubit interacting with an array of transmission line resonators. The scheme is based on the following two observations: First, compared with conventional systems, the short-time nonexponential decay in our superconducting circuit system is readily observed; and second, a quench-off process mimics an ideal projective measurement when its time duration is sufficiently long. Our results show the active role of quantum quench in quantum simulation and control.
Kleine, Christian; Mußhoff, Julian; Anders, Frithjof B.
2014-12-01
The energy-dependent scattering of fermions from a localized orbital at an energy-dependent rate Γ (ɛ ) ∝|ɛ| r gives rise to quantum critical points (QCPs) in the pseudogap single-impurity Anderson model separating a local moment phase with an unscreened spin moment from a strong-coupling phase which slightly deviates from the screened phase of standard Kondo problem. Using the time-dependent numerical renormalization group (TD-NRG) approach we show that local dynamic properties always equilibrate towards a steady-state value even for quenches across the QCP but with systematic deviations from the thermal equilibrium depending on the distance to the critical coupling. Local nonequilibrium properties are presented for interaction quenches and hybridization quenches. We augment our numerical data by an analytical calculation that becomes exact at short times and find excellent agreement between the numerics and the analytical theory. For interaction quenches within the screened phase we find a universal function for the time-dependent local double occupancy. We trace back the discrepancy between our results and the data obtained by a time-dependent Gutzwiller variational approach to restrictions of the wave-function ansatz in the Gutzwiller theory: while the NRG ground states properly account for the formation of an extended spin moment which decouples from the system in the unscreened phase, the Gutzwiller ansatz only allows the formation of the spin moment on the local impurity orbital.
Quantum quench and scaling of entanglement entropy
Caputa, Paweł; Das, Sumit R.; Nozaki, Masahiro; Tomiya, Akio
2017-09-01
Global quantum quench with a finite quench rate which crosses critical points is known to lead to universal scaling of correlation functions as functions of the quench rate. In this work, we explore scaling properties of the entanglement entropy of a subsystem in a harmonic chain during a mass quench which asymptotes to finite constant values at early and late times and for which the dynamics is exactly solvable. When the initial state is the ground state, we find that for large enough subsystem sizes the entanglement entropy becomes independent of size. This is consistent with Kibble-Zurek scaling for slow quenches, and with recently discussed ;fast quench scaling; for quenches fast compared to physical scales, but slow compared to UV cutoff scales.
Response functions after a quantum quench
Marcuzzi, Matteo; Gambassi, Andrea
2014-04-01
The response of physical systems to external perturbations can be used to probe both their equilibrium and nonequilibrium dynamics. While response and correlation functions are related in equilibrium by fluctuation-dissipation theorems, out of equilibrium they provide complementary information on the dynamics. In the past years, a method has been devised to map the quantum dynamics of an isolated extended system after a quench onto a static theory with boundaries in imaginary time; up to now, however, the focus was entirely on symmetrized correlation functions. Here we provide a prescription which, in principle, allows one to retrieve the whole set of relevant dynamical quantities characterizing the evolution, including linear response functions. We illustrate this construction with some relevant examples, showing in the process the emergence of light-cone effects similar to those observed in correlation functions.
Bridging global and local quantum quenches in conformal field theories
Wen, Xueda
2016-01-01
Entanglement evolutions after a global quantum quench and a local quantum quench in 1+1 dimensional conformal field theories (CFTs) show qualitatively different behaviors, and are studied within two different setups. In this work, we bridge global and local quantum quenches in (1+1)-d CFTs in the same setup, by studying the entanglement evolution from a specific inhomogeneous initial state. By utilizing conformal mappings, this inhomogeneous quantum quench is analytically solvable. It is found that the entanglement evolution shows a global quantum quench feature in the short time limit, and a local quantum quench feature in the long time limit. The same features are observed in single-point correlation functions of primary fields. We provide a clear physical picture for the underlying reason.
Quantum Quenches in Free Field Theory: Universal Scaling at Any Rate
Das, Sumit R; Myers, Robert C
2016-01-01
Quantum quenches display universal scaling in several regimes. For quenches which start from a gapped phase and cross a critical point, with a rate slow compared to the initial gap, many systems obey Kibble-Zurek scaling. More recently, a different scaling behaviour has been shown to occur when the quench rate is fast compared to all other physical scales, but still slow compared to the UV cutoff. We investigate the passage from fast to slow quenches in scalar and fermionic free field theories with time dependent masses for which the dynamics can be solved exactly for all quench rates. We find that renormalized one point functions smoothly cross over between the regimes.
Ma, Qiang; Yu, Wei; Huang, Hui; Su, Xingguang
2011-01-01
In this paper, we attempted to develop a novel application of Mn-doped ZnSe quantum dots (Mn: ZnSe d-dots) as probes to detect L-tyrosine (L-Tyr). The bio-conjugates of horseradish peroxidase (HRP)-conjugated Mn: ZnSe d-dots were used in the enzyme catalyzed reaction of L-Tyr with H(2)O(2.) Compared with traditional CdTe QDs, Mn: ZnSe d-dots have better biocompatibility and less negative impact on enzyme catalyzed system. In HRP-conjugated Mn: ZnSe-L-Tyr-H(2)O(2) system, electron transfer occurred between Mn: ZnSe d-dots and HRP. It resulted in the luminescence quenching of the Mn: ZnSe d-dots., which can be used to detect L-Tyr. The coupling of efficient quenching of Mn: ZnSe d-dots photoluminescence (PL) and the effective enzyme-catalysis can afford a simple and sensitive method for L-Tyr detection. The Mn: ZnSe d-dots-enzyme catalyzed system displays great potential in the development of enzyme-based biosensing systems for various analytes.
The LHC quench protection system
2009-01-01
The new quench protection system (QPS) has the crucial roles of providing an early warning for any part of the superconducting coils and busbars that develop high resistance, as well as triggering the switch-off of the machine. Over 2000 new detectors will be installed around the LHC to make sure every busbar segment between magnets is monitored and protected. One of the major consolidation activities for the LHC is the addition of two new detectors to the quench protection system. A magnet quench occurs when part of the superconducting cable becomes normally-conducting. When the protection system detects an increased resistance the huge amount of energy stored in the magnet chains is safely extracted and ‘dumped’ into specially designed resistors. In the case of the main dipole chain, the stored energy in a single LHC sector is roughly the same as the kinetic energy of a passenger jet at cruising speed. The first new detector is designed to monitor the superconducting...
Chiocchetta, Alessio; Tavora, Marco; Gambassi, Andrea; Mitra, Aditi
2016-10-01
We investigate the effects of fluctuations on the dynamics of an isolated quantum system represented by a (ϕ2)2 field theory with O (N ) symmetry after a quench in d >2 spatial dimensions. A perturbative renormalization-group approach involving a dimensional expansion in ɛ =4 -d is employed in order to study the evolution within a prethermal regime controlled by elastic dephasing. In particular, we focus on a quench from a disordered initial state to the critical point, which introduces an effective temporal boundary in the evolution. At this boundary, the relevant fields acquire an anomalous scaling dimension, while the evolution of both the order parameter and its correlation and response functions display universal aging. Since the relevant excitations propagate ballistically, a light cone in real space emerges. At longer times, the onset of inelastic scattering appears as secularly growing self-generated dissipation in the effective Keldysh field theory, with the strength of the dissipative vertices providing an estimate for the time needed to leave the prethermal regime.
Rajak, Atanu; Divakaran, Uma
2016-04-01
We study the effect of two simultaneous local quenches on the evolution of the Loschmidt echo (LE) and entanglement entropy (EE) of a one dimensional transverse Ising model. In this work, one of the local quenches involves the connection of two spin-1/2 chains at a certain time and the other corresponds to a sudden change in the magnitude of the transverse field at a given site in one of the spin chains. We numerically calculate the dynamics associated with the LE and the EE as a result of such double quenches, and discuss the various timescales involved in this problem using the picture of quasiparticles (QPs) generated as a result of such quenches. We perform a detailed analysis of the probability of QPs produced at the two sites and the nature of the QPs in various phases, and obtain interesting results. More specifically, we find partial reflection of these QPs at the defect center or the site of h-quench, resulting in new timescales which have never been reported before.
Quench Dynamics in Confined 1+1-Dimensional Systems
Engelhardt, Dalit
2015-01-01
We present a scheme for investigating the response of confined 1+1-dimensional systems to a quantum quench and consider the extent to which a system whose post-quench dynamics are near-integrable may be analyzed by an application of boundary CFT techniques. As the main example we present a model of a split-momentum quench in a finite 1D geometry, a setup analogous to that of the experiment of Kinoshita, Wenger, and Weiss [Nature 440, 900 (2006)]. We analytically derive the form of the expected momentum distributions and describe how such information may be used to assess the extent of integrability breaking in realistic systems.
Momentum-Space Entanglement and Loschmidt Echo in Luttinger Liquids after a Quantum Quench.
Dóra, Balázs; Lundgren, Rex; Selover, Mark; Pollmann, Frank
2016-07-01
Luttinger liquids (LLs) arise by coupling left- and right-moving particles through interactions in one dimension. This most natural partitioning of LLs is investigated by the momentum-space entanglement after a quantum quench using analytical and numerical methods. We show that the momentum-space entanglement spectrum of a LL possesses many universal features both in equilibrium and after a quantum quench. The largest entanglement eigenvalue is identical to the Loschmidt echo, i.e., the overlap of the disentangled and final wave functions of the system. The second largest eigenvalue is the overlap of the first excited state of the disentangled system with zero total momentum and the final wave function. The entanglement gap is universal both in equilibrium and after a quantum quench. The momentum-space entanglement entropy is always extensive and saturates fast to a time independent value after the quench, in sharp contrast to a spatial bipartitioning.
Momentum-Space Entanglement and Loschmidt Echo in Luttinger Liquids after a Quantum Quench
Dóra, Balázs; Lundgren, Rex; Selover, Mark; Pollmann, Frank
2016-07-01
Luttinger liquids (LLs) arise by coupling left- and right-moving particles through interactions in one dimension. This most natural partitioning of LLs is investigated by the momentum-space entanglement after a quantum quench using analytical and numerical methods. We show that the momentum-space entanglement spectrum of a LL possesses many universal features both in equilibrium and after a quantum quench. The largest entanglement eigenvalue is identical to the Loschmidt echo, i.e., the overlap of the disentangled and final wave functions of the system. The second largest eigenvalue is the overlap of the first excited state of the disentangled system with zero total momentum and the final wave function. The entanglement gap is universal both in equilibrium and after a quantum quench. The momentum-space entanglement entropy is always extensive and saturates fast to a time independent value after the quench, in sharp contrast to a spatial bipartitioning.
DEFF Research Database (Denmark)
Nysteen, Anders; Nielsen, Per Kær; Mørk, Jesper
2013-01-01
by photoluminescence excitation spectroscopy of a single quantum dot. We also investigate the implications for cavity QED, i.e., a coupled quantum dot-cavity system, and demonstrate that the phonon scattering may be strongly quenched. The quenching is explained by a balancing between the deformation potential...
Local quenches in frustrated quantum spin chains: global vs. subsystem equilibration
Diez, Mathias; Haas, Stephan; Venuti, Lorenzo Campos; Zanardi, Paolo
2010-01-01
We study the equilibration behavior following local quenches, using frustrated quantum spin chains as an example of interacting closed quantum systems. Specifically, we examine the statistics of the time series of the Loschmidt echo, the trace distance of the time-evolved local density matrix to its average state, and the local magnetization. Depending on the quench parameters, the equilibration statistics of these quantities show features of good or poor equilibration, indicated by Gaussian, exponential or bistable distribution functions. These universal functions provide valuable tools to characterize the various time-evolution responses and give insight into the plethora of equilibration phenomena in complex quantum systems.
Sudden interaction quench in the quantum sine-Gordon model
Energy Technology Data Exchange (ETDEWEB)
Sabio, Javier [Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Ines de la Cruz 3, E-28049 Madrid (Spain); Kehrein, Stefan, E-mail: javier.sabio@icmm.csic.e [Arnold-Sommerfeld-Center for Theoretical Physics, Center for NanoSciences and Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Theresienstrasse 37, 80333 Muenchen (Germany)
2010-05-15
We study a sudden interaction quench in the weak-coupling regime of the quantum sine-Gordon model. The real time dynamics of the bosonic mode occupation numbers is calculated using the flow equation method. While we cannot prove results for the asymptotic long-time limit, we can establish the existence of an extended regime in time where the mode occupation numbers relax to twice their equilibrium values. This factor two indicates a non-equilibrium distribution and is a universal feature of weak interaction quenches. The weak-coupling quantum sine-Gordon model therefore turns out to be on the borderline between thermalization and non-thermalization.
Entrapment in phospholipid vesicles quenches photoactivity of quantum dots.
Generalov, Roman; Kavaliauskiene, Simona; Westrøm, Sara; Chen, Wei; Kristensen, Solveig; Juzenas, Petras
2011-01-01
Quantum dots have emerged with great promise for biological applications as fluorescent markers for immunostaining, labels for intracellular trafficking, and photosensitizers for photodynamic therapy. However, upon entry into a cell, quantum dots are trapped and their fluorescence is quenched in endocytic vesicles such as endosomes and lysosomes. In this study, the photophysical properties of quantum dots were investigated in liposomes as an in vitro vesicle model. Entrapment of quantum dots in liposomes decreases their fluorescence lifetime and intensity. Generation of free radicals by liposomal quantum dots is inhibited compared to that of free quantum dots. Nevertheless, quantum dot fluorescence lifetime and intensity increases due to photolysis of liposomes during irradiation. In addition, protein adsorption on the quantum dot surface and the acidic environment of vesicles also lead to quenching of quantum dot fluorescence, which reappears during irradiation. In conclusion, the in vitro model of phospholipid vesicles has demonstrated that those quantum dots that are fated to be entrapped in endocytic vesicles lose their fluorescence and ability to act as photosensitizers.
Entrapment in phospholipid vesicles quenches photoactivity of quantum dots
Directory of Open Access Journals (Sweden)
Generalov R
2011-09-01
Full Text Available Roman Generalov1,2, Simona Kavaliauskiene1, Sara Westrøm1, Wei Chen3, Solveig Kristensen2, Petras Juzenas11Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; 2School of Pharmacy, University of Oslo, Oslo, Norway; 3Department of Physics, The University of Texas at Arlington, Arlington, TX, USAAbstract: Quantum dots have emerged with great promise for biological applications as fluorescent markers for immunostaining, labels for intracellular trafficking, and photosensitizers for photodynamic therapy. However, upon entry into a cell, quantum dots are trapped and their fluorescence is quenched in endocytic vesicles such as endosomes and lysosomes. In this study, the photophysical properties of quantum dots were investigated in liposomes as an in vitro vesicle model. Entrapment of quantum dots in liposomes decreases their fluorescence lifetime and intensity. Generation of free radicals by liposomal quantum dots is inhibited compared to that of free quantum dots. Nevertheless, quantum dot fluorescence lifetime and intensity increases due to photolysis of liposomes during irradiation. In addition, protein adsorption on the quantum dot surface and the acidic environment of vesicles also lead to quenching of quantum dot fluorescence, which reappears during irradiation. In conclusion, the in vitro model of phospholipid vesicles has demonstrated that those quantum dots that are fated to be entrapped in endocytic vesicles lose their fluorescence and ability to act as photosensitizers.Keywords: fluorescence lifetime, free radicals, liposomes, lipodots, reactive oxygen species
Quantum quenches to the attractive one-dimensional Bose gas: exact results
Directory of Open Access Journals (Sweden)
Lorenzo Piroli, Pasquale Calabrese, Fabian H. L. Essler
2016-09-01
Full Text Available We study quantum quenches to the one-dimensional Bose gas with attractive interactions in the case when the initial state is an ideal one-dimensional Bose condensate. We focus on properties of the stationary state reached at late times after the quench. This displays a finite density of multi-particle bound states, whose rapidity distribution is determined exactly by means of the quench action method. We discuss the relevance of the multi-particle bound states for the physical properties of the system, computing in particular the stationary value of the local pair correlation function $g_2$.
Smooth and fast versus instantaneous quenches in quantum field theory
Das, Sumit R; Myers, Robert C
2015-01-01
We examine in detail the relationship between smooth fast quantum quenches, characterized by a time scale $\\delta t$, and instantaneous quenches, within the framework of exactly solvable mass quenches in free scalar field theory. We study UV finite quantities like correlators at finite spatial distances and the excess energy produced above the final ground state energy. We show that at late times and large distances (compared to the quench time scale) the correlator approaches the instantaneous quench correlator. At early times, we find that for small spatial separation and small $\\delta t$, the correlator scales universally with $\\delta t$, exactly as in the scaling of renormalized one point functions found in earlier work. At larger separation, the dependence on $\\delta t$ drops out. The excess energy also scales in a universal fashion: in the $m\\delta t \\rightarrow0$ limit it is finite for $d \\leq 3$ and agrees with the instantaneous quench, while it is divergent in higher dimensions. We argue that similar...
Overlaps after quantum quenches in the sine-Gordon model
Horváth, D. X.; Takács, G.
2017-08-01
We present a numerical computation of overlaps in mass quenches in sine-Gordon quantum field theory using truncated conformal space approach (TCSA). To improve the cut-off dependence of the method, we use a novel running coupling definition which has a general applicability in free boson TCSA. The numerical results for the first breather overlaps are compared with the analytic continuation of a previously proposed analytical Ansatz for the initial state in a related sinh-Gordon quench, and good agreement is found between the numerical data and the analytical prediction in a large energy range.
MSFC Electrostatic Levitator (ESL) Rapid Quench System
SanSoucie, Michael P.; Craven, Paul D.; Rogers, Jan R.
2014-01-01
The NASA Marshall Space Flight Center (MSFC) Electrostatic Levitator (ESL) Laboratory is a unique facility for investigators studying high-temperature materials. The laboratory boasts two levitators in which samples can be levitated, heated, melted, undercooled, and resolidified, all without the interference of a container or data-gathering instrument. The ESL main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy. Thereby allowing rapid quenching of undercooled liquid metals. Up to 8 quench vessels can be loaded into the quench wheel, which is indexed with LabVIEW control software. This allows up to 8 samples to be rapidly quenched before having to open the chamber. The system has been tested successfully on several zirconium samples. Future work will be done with other materials using different quench mediums. Microstructural analysis will also be done on successfully quench samples.
Universal corrections to entanglement entropy of local quantum quenches
David, Justin R; Kumar, S Prem
2016-01-01
We study the time evolution of single interval Renyi and entanglement entropies following local quantum quenches in two dimensional conformal field theories at finite temperature for which the locally excited states have a finite temporal width, \\epsilon. We show that, for local quenches produced by the action of a conformal primary field, the time dependence of Renyi and entanglement entropies at order \\epsilon^2 is universal. It is determined by the expectation value of the stress tensor in the replica geometry and proportional to the conformal dimension of the primary field generating the local excitation. We also show that in CFTs with a gravity dual, the \\epsilon^2 correction to the holographic entanglement entropy following a local quench precisely agrees with the CFT prediction. We then consider CFTs admitting a higher spin symmetry and turn on a higher spin chemical potential \\mu. We calculate the time dependence of the order \\epsilon^2 correction to the entanglement entropy for small \\mu, and show th...
Exact infinite-time statistics of the Loschmidt echo for a quantum quench
Venuti, Lorenzo Campos; Santra, Siddhartha; Zanardi, Paolo
2011-01-01
The equilibration dynamics of a closed quantum system is encoded in the long-time distribution function of generic observables. In this paper we consider the Loschmidt echo generalized to finite temperature, and show that we can obtain an exact expression for its long-time distribution for a closed system described by a quantum XY chain following a sudden quench. In the thermodynamic limit the logarithm of the Loschmidt echo becomes normally distributed, whereas for small quenches in the opposite, quasi-critical regime, the distribution function acquires a universal double-peaked form indicating poor equilibration. These findings, obtained by a central limit theorem-type result, extend to completely general models in the small-quench regime.
Quantum quenching of radiation losses in short laser pulses
Harvey, Chris; Ilderton, Anton; Marklund, Mattias
2016-01-01
Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.
Universal corrections to entanglement entropy of local quantum quenches
David, Justin R.; Khetrapal, Surbhi; Kumar, S. Prem
2016-08-01
We study the time evolution of single interval Rényi and entanglement entropies following local quantum quenches in two dimensional conformal field theories at finite temperature for which the locally excited states have a finite temporal width ɛ. We show that, for local quenches produced by the action of a conformal primary field, the time dependence of Rényi and entanglement entropies at order ɛ2 is universal. It is determined by the expectation value of the stress tensor in the replica geometry and proportional to the conformal dimension of the primary field generating the local excitation. We also show that in CFTs with a gravity dual, the ɛ2 correction to the holographic entanglement entropy following a local quench precisely agrees with the CFT prediction. We then consider CFTs admitting a higher spin symmetry and turn on a higher spin chemical potential μ. We calculate the time dependence of the order ɛ2 correction to the entanglement entropy for small μ, and show that the contribution at order μ 2 is universal. We verify our arguments against exact results for minimal models and the free fermion theory.
Quench echo and work statistics in integrable quantum field theories.
Pálmai, T; Sotiriadis, S
2014-11-01
We propose a boundary thermodynamic Bethe ansatz calculation technique to obtain the Loschmidt echo and the statistics of the work done when a global quantum quench is performed on an integrable quantum field theory. We derive an analytic expression for the lowest edge of the probability density function and find that it exhibits universal features, in the sense that its scaling form depends only on the statistics of excitations. We perform numerical calculations on the sinh-Gordon model, a deformation of the free boson theory, and we obtain that by turning on the interaction the density function develops fermionic properties. The calculations are facilitated by a previously unnoticed property of the thermodynamic Bethe ansatz construction.
Quantum phase transition and quench dynamics in the anisotropic Rabi model
Shen, Li-Tuo; Yang, Zhen-Biao; Wu, Huai-Zhi; Zheng, Shi-Biao
2017-01-01
We investigate the quantum phase transition (QPT) and quench dynamics in the anisotropic Rabi model when the ratio of the qubit transition frequency to the oscillator frequency approaches infinity. Based on the Schrieffer-Wolff transformation, we find an anti-Hermitian operator that maps the original Hamiltonian into a one-dimensional oscillator Hamiltonian within the spin-down subspace. We analytically derive the eigenenergy and eigenstate of the normal and superradiant phases and demonstrate that the system undergoes a second-order quantum phase transition at a critical border. The critical border is a straight line in a two-dimensional parameter space which essentially extends the dimensionality of QPT in the Rabi model. By combining the Kibble-Zurek mechanism and the adiabatic dynamics method, we find that the residual energy vanishes as the quench time tends to zero, which is a sharp contrast to the universal scaling where the residual energy diverges in the same limit.
Orlova, A O; Gromova, Yu A; Maslov, V G; Andreeva, O V; Baranov, A V; Fedorov, A V; Prudnikau, A V; Artemyev, M V; Berwick, K
2013-08-23
The photoluminescence response of semiconductor CdSe/ZnS quantum dots embedded in a borosilicate porous glass matrix to exposure to ammonia vapor is investigated. The formation of surface complexes on the quantum dots results in quenching of the photoluminescence and a shortening of the luminescence decay time. The process is reversible, desorption of ammonia molecules from the quantum dot surface causes the photoluminescence to recover. The sensitivity of the quantum dot luminescence intensity and decay time to the interaction time and the reversibility of the photoluminescence changes make the CdSe/ZnS quantum dots in porous glass system a candidate for use as an optical sensor of ammonia.
Orlova, A. O.; Gromova, Yu A.; Maslov, V. G.; Andreeva, O. V.; Baranov, A. V.; Fedorov, A. V.; Prudnikau, A. V.; Artemyev, M. V.; Berwick, K.
2013-08-01
The photoluminescence response of semiconductor CdSe/ZnS quantum dots embedded in a borosilicate porous glass matrix to exposure to ammonia vapor is investigated. The formation of surface complexes on the quantum dots results in quenching of the photoluminescence and a shortening of the luminescence decay time. The process is reversible, desorption of ammonia molecules from the quantum dot surface causes the photoluminescence to recover. The sensitivity of the quantum dot luminescence intensity and decay time to the interaction time and the reversibility of the photoluminescence changes make the CdSe/ZnS quantum dots in porous glass system a candidate for use as an optical sensor of ammonia.
Liu, Cheng-Wei
Phase transitions and their associated critical phenomena are of fundamental importance and play a crucial role in the development of statistical physics for both classical and quantum systems. Phase transitions embody diverse aspects of physics and also have numerous applications outside physics, e.g., in chemistry, biology, and combinatorial optimization problems in computer science. Many problems can be reduced to a system consisting of a large number of interacting agents, which under some circumstances (e.g., changes of external parameters) exhibit collective behavior; this type of scenario also underlies phase transitions. The theoretical understanding of equilibrium phase transitions was put on a solid footing with the establishment of the renormalization group. In contrast, non-equilibrium phase transition are relatively less understood and currently a very active research topic. One important milestone here is the Kibble-Zurek (KZ) mechanism, which provides a useful framework for describing a system with a transition point approached through a non-equilibrium quench process. I developed two efficient Monte Carlo techniques for studying phase transitions, one is for classical phase transition and the other is for quantum phase transitions, both are under the framework of KZ scaling. For classical phase transition, I develop a non-equilibrium quench (NEQ) simulation that can completely avoid the critical slowing down problem. For quantum phase transitions, I develop a new algorithm, named quasi-adiabatic quantum Monte Carlo (QAQMC) algorithm for studying quantum quenches. I demonstrate the utility of QAQMC quantum Ising model and obtain high-precision results at the transition point, in particular showing generalized dynamic scaling in the quantum system. To further extend the methods, I study more complex systems such as spin-glasses and random graphs. The techniques allow us to investigate the problems efficiently. From the classical perspective, using the
Protein trafficking rates assessed by quantum dot quenching with bromocresol green
Valentine, Cathleen D.; Verkman, A.S.; Haggie, Peter M.
2011-01-01
Quantum dots are bright, photostable fluorophores used extensively to investigate biological processes. Here, we report that bromocresol green at low micromolar concentrations rapidly, efficiently and reversibly quenches the fluorescence of commercial quantum dots having a wide range of functionalities. The broad utility of bromocresol green quenching of quantum dots in cell biology is demonstrated in quantitative assays of trafficking of the β2-adrenergic receptor and the cystic fibrosis tra...
Quantum Information Processing in Disordered and Complex Quantum Systems
De, A S; Ahufinger, V; Briegel, H J; Sanpera, A; Lewenstein, M; De, Aditi Sen; Sen, Ujjwal; Ahufinger, Veronica; Briegel, Hans J.; Sanpera, Anna; Lewenstein, Maciej
2005-01-01
We investigate quantum information processing and manipulations in disordered systems of ultracold atoms and trapped ions. First, we demonstrate generation of entanglement and local realization of quantum gates in a quantum spin glass system. Entanglement in such systems attains significantly high values, after quenched averaging, and has a stable positive value for arbitrary times. Complex systems with long range interactions, such as ion chains or dipolar atomic gases, can be modeled by neural network Hamiltonians. In such systems, we find the characteristic time of persistence of quenched averaged entanglement, and also find the time of its revival.
Correlations and diagonal entropy after quantum quenches in XXZ chains
Piroli, Lorenzo; Vernier, Eric; Calabrese, Pasquale; Rigol, Marcos
2017-02-01
We study quantum quenches in the XXZ spin-1 /2 Heisenberg chain from families of ferromagnetic and antiferromagnetic initial states. Using Bethe ansatz techniques, we compute short-range correlators in the complete generalized Gibbs ensemble (GGE), which takes into account all local and quasilocal conservation laws. We compare our results to exact diagonalization and numerical linked cluster expansion calculations for the diagonal ensemble, finding excellent agreement and thus providing a very accurate test for the validity of the complete GGE. Furthermore, we use exact diagonalization to compute the diagonal entropy in the postquench steady state. We show that the Yang-Yang entropy for the complete GGE is consistent with twice the value of the diagonal entropy in the largest chains or the extrapolated result in the thermodynamic limit. Finally, the complete GGE is quantitatively contrasted with the GGE built using only the local conserved charges (local GGE). The predictions of the two ensembles are found to differ significantly in the case of ferromagnetic initial states. Such initial states are better suited than others considered in the literature to experimentally test the validity of the complete GGE and contrast it to the failure of the local GGE.
System and method for quench protection of a superconductor
Huang, Xianrui; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas
2008-03-11
A system and method for protecting a superconductor from a quench condition. A quench protection system is provided to protect the superconductor from damage due to a quench condition. The quench protection system comprises a voltage detector operable to detect voltage across the superconductor. The system also comprises a frequency filter coupled to the voltage detector. The frequency filter is operable to couple voltage signals to a control circuit that are representative of a rise in superconductor voltage caused by a quench condition and to block voltage signals that are not. The system is operable to detect whether a quench condition exists in the superconductor based on the voltage signal received via the frequency filter and to initiate a protective action in response.
Jafari, R.
2016-05-01
We study the ground state fidelity, fidelity susceptibility, and quench dynamics of the extended quantum compass model in a transverse field. This model reveals a rich phase diagram which includes several critical surfaces depending on exchange couplings. We present a characterization of quantum phase transitions in terms of the ground state fidelity between two ground states obtained for two different values of external parameters. We also derive scaling relations describing the singular behavior of the fidelity susceptibility in the quantum critical surfaces. Moreover, we study the time evolution of the system after a critical quantum quench using the Loschmidt echo (LE). We find that the revival times of LE are given by {T}{rev}=N/2{v}{max}, where N is the size of the system and v max is the maximum of the lower bound group velocity of quasi-particles. Although the fidelity susceptibility shows the same exponent in all critical surfaces, the structure of the revivals after critical quantum quenches displays two different regimes reflecting different equilibration dynamics.
Assay of ceftazidime and cefepime based on fluorescence quenching of carbon quantum dots.
Huang, Yu; Zhang, Ying; Yan, Zhengyu; Liao, Shenghua
2015-11-01
A novel and sensitive method for the determination of ceftazidime and cefepime in an active pharmaceutical ingredient (API) has been developed based on the fluorescence quenching of poly(ethylene glycol) (PEG)2000-capped carbon quantum dots (CQDs) prepared using a chemical oxidation method. The quenching of fluorescence intensity is proportional to the concentration of ceftazidime and cefepime over the range of 0.33-3.30 and 0.24-2.40 µg/mL, respectively. The mode of interaction between PEG2000-capped CQDs and ceftazidime/cefepime in aqueous solutions was investigated using a fluorescence, UV/Vis and Fourier transform infrared spectrometry (FTIR) at physiological pH. UV/Vis and FTIR spectra demonstrated that ground state compounds were formed through hydrophobic interaction the fluorescence quenching of CQDs caused by ceftazidime and cefepime. The quenching constants decreased with increases in temperature, which was consistent with static quenching.
Energy Technology Data Exchange (ETDEWEB)
Baride, Aravind [Department of Chemistry, University of South Dakota, Vermillion, SD 57069 (United States); Engebretson, Daniel [Biomedical Engineering, University of South Dakota, Vermillion, SD 57069 (United States); Berry, Mary T. [Department of Chemistry, University of South Dakota, Vermillion, SD 57069 (United States); Stanley May, P., E-mail: smay@usd.edu [Department of Chemistry, University of South Dakota, Vermillion, SD 57069 (United States)
2013-09-15
The photoinduced release of highly fluorescent 7-diethylamino coumarin (7DEAC) from CdSe quantum dots (QD) modified with a thiocinnamate ligand (11-mercapto undecyl-E-3-(4-(N,N-diethylamino)-2-hydroxy phenyl) propenoate, [4DEATC]) has been previously described. Coumarin fluorescence was used to ‘report’ the photochemical reaction. The current study quantifies the quenching effect of the QDs on the coumarin emission in this system. A systematic study is presented on the quenching of 7DEAC by CdSe and CdSe/ZnS quantum dots capped with 2-[2-(2-methoxyethoxy)ethoxy] ethanethiol (PEG-thiol). A new method for the functionalization of CdSe and CdSe/ZnS QDs with PEG-thiol was developed, which does not require isolation of the as-synthesized QDs. Stern–Volmer analysis was applied to quantify the effect of the PEG-CdSe and PEG-CdSe/ZnS on 7DEAC emission. The Stern–Volmer constant, K{sub SV}, was shown to be inversely proportional to temperature for quenching by PEG-CdSe, and the fluorescence lifetime of 7DEAC was shown to be independent of PEG-CdSe concentration. Room-temperature K{sub SV} values were similar for the PEG-CdSe and PEG-CdSe/ZnS quenchers. The large magnitude of K{sub SV}, the temperature dependence of K{sub SV}, the lifetime data, and the similarity of K{sub SV} values for the core and core–shell QD quenchers are all consistent with a static quenching mechanism. Assuming a static quenching mechanism, the temperature dependence of the coumarin-QD binding constant, K{sub b}, was used to estimate the ΔH and ΔS for the binding process. -- Highlights: • Quenching of a coumarin derivative by CdSe and CdSe/ZnS quantum dots is demonstrated • Stern–Volmer analysis is performed as a function of temperature • Fluorescence lifetime analysis was used to support Stern–Volmer analysis • Data overwhelmingly support quenching via a Static Mechanism • Quenching of coumarin by quantum dots is significant and must be considered in any release and report
Sudeep, P K; Emrick, Todd
2009-12-22
Silicon quantum dots (QDs) were prepared with a corona of di-n-octyl phosphine oxides, by performing hydrosilylation chemistry on the surface of hydrogen-terminated Si QDs. These novel Si QDs proved well-suited to serve as "ligands" for other semiconductor QDs, such as CdSe, by interaction of the phosphine oxide corona with the CdSe surface. A pronounced photoluminescence quenching of CdSe quantum dots was observed upon introduction of the phosphine oxide functionalized Si QDs to a CdSe QD solution. Surface functionalization of the Si QDs proved critically important to observing these effects, as conventional (alkane-covered) Si QD samples gave no evidence of electronic interactions with TOPO-covered CdSe. In a comparative system, phosphine oxide terminated oligo(phenylene vinylene) molecules acting as CdSe QD ligands provide a similar fluorescence quenching, with exciton decay kinetics supporting the formation of an electronically interacting hybrid materials system.
Kurzmann, Annika; Ludwig, Arne; Wieck, Andreas D; Lorke, Axel; Geller, Martin
2016-05-11
In quantum dots (QDs), the Auger recombination is a nonradiative process in which the electron-hole recombination energy is transferred to an additional carrier. It has been studied mostly in colloidal QDs, where the Auger recombination time is in the picosecond range and efficiently quenches the light emission. In self-assembled QDs, on the other hand, the influence of Auger recombination on the optical properties is in general neglected, assuming that it is masked by other processes such as spin and charge fluctuations. Here, we use time-resolved resonance fluorescence to analyze the Auger recombination and its influence on the optical properties of a single self-assembled QD. From excitation-power-dependent measurements, we find a long Auger recombination time of about 500 ns and a quenching of the trion transition by about 80%. Furthermore, we observe a broadening of the trion transition line width by up to a factor of 2. With a model based on rate equations, we are able to identify the interplay between tunneling and Auger rate as the underlying mechanism for the reduced intensity and the broadening of the line width. This demonstrates that self-assembled QDs can serve as an ideal model system to study how the charge recapture process, given by the band-structure surrounding the confined carriers, influences the Auger process. Our findings are not only relevant for improving the emission properties of colloidal QD-based emitters and dyes, which have recently entered the consumer market, but also of interest for more visionary applications, such as quantum information technologies, based on self-assembled quantum dots.
Memory-preserving equilibration after a quantum quench in a one-dimensional critical model
Sotiriadis, Spyros
2016-09-01
One of the fundamental principles of statistical physics is that only partial information about a system's state is required for its macroscopic description. This is not only true for thermal ensembles, but also for the unconventional ensemble, known as generalized Gibbs ensemble (GGE), that is expected to describe the relaxation of integrable systems after a quantum quench. By analytically studying the quench dynamics in a prototypical one-dimensional critical model, the massless free bosonic field theory, we find evidence of a novel type of equilibration characterized by the preservation of an enormous amount of memory of the initial state that is accessible by local measurements. In particular, we show that the equilibration retains memory of non-Gaussian initial correlations, in contrast to the case of massive free evolution which erases all such memory. The GGE in its standard form, being a Gaussian ensemble, fails to predict correctly the equilibrium values of local observables, unless the initial state is Gaussian itself. Our findings show that the equilibration of a broad class of quenches whose evolution is described by Luttinger liquid theory with an initial state that is non-Gaussian in terms of the bosonic field, is not correctly captured by the corresponding bosonic GGE, raising doubts about the validity of the latter in general one-dimensional gapless integrable systems such as the Lieb-Liniger model. We also propose that the same experiment by which the GGE was recently observed [Langen et al., Science 348, 207 (2015), 10.1126/science.1257026] can also be used to observe its failure, simply by starting from a non-Gaussian initial state.
ZnSe quantum dots based fluorescence quenching method for determination of paeoniflorin
Energy Technology Data Exchange (ETDEWEB)
Chen, Zhi [Center of Analysis, Guangdong Medical College, Dongguan 523808 (China); School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Chen, Jiayi; Liang, Qiaowen [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Wu, Dudu [Center of Analysis, Guangdong Medical College, Dongguan 523808 (China); Zeng, Yuaner, E-mail: zengyuaner@126.com [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Jiang, Bin, E-mail: gzjiangbin@hotmail.com [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China)
2014-01-15
Water soluble ZnSe quantum dots (QDs) modified by mercaptoacetic acid (MAA) were used to determinate paeoniflorin in aqueous solutions by the fluorescence spectroscopic technique. The results showed that the fluorescence of the modified ZnSe QDs could be quenched by paeoniflorin effectively in physiological buffer solution. The optimum fluorescence intensity was found to be at incubation time 10 min, pH 7.0 and temperature 25 °C. Under the optimal conditions, the detection limit of paeoniflorin was 7.30×10{sup −7} mol L{sup −1}. Moreover, the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching rate constant K{sub q} (1.02×10{sup 13} L mol{sup −1} s{sup −1}). -- Highlights: • The fluorescence intensity of ZnSe QDs could be quenched by paeoniflorin. • Foreign substance showed insignificant effect for determination of paeoniflorin. • The quenching mechanism was discussed to be a static quenching procedure.
New Initial Conditions for Quantum Field Simulations after a Quench
Salle, M; Vink, Jeroen C
2002-01-01
We investigate a new way of using the quantum fluctuations in the vacuum as initial conditions for subsequent classical field dynamics. This method avoids problems with renormalization and leads to better thermalization.
Huang, Hao; Dorn, August; Nair, Gautham P; Bulović, Vladimir; Bawendi, Moungi G
2007-12-01
We demonstrate reversible quenching of the photoluminescence from single CdSe/ZnS colloidal quantum dots embedded in thin films of the molecular organic semiconductor N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) in a layered device structure. Our analysis, based on current and charge carrier density, points toward field ionization as the dominant photoluminescence quenching mechanism. Blinking traces from individual quantum dots reveal that the photoluminescence amplitude decreases continuously as a function of increasing forward bias even at the single quantum dot level. In addition, we show that quantum dot photoluminescence is quenched by aluminum tris(8-hydroxyquinoline) (Alq3) in chloroform solutions as well as in thin solid films of Alq3 whereas TPD has little effect. This highlights the importance of chemical compatibility between semiconductor nanocrystals and surrounding organic semiconductors. Our study helps elucidate elementary interactions between quantum dots and organic semiconductors, knowledge needed for designing efficient quantum dot organic optoelectronic devices.
Infinite-time average of local fields in an integrable quantum field theory after a quantum quench.
Mussardo, G
2013-09-06
The infinite-time average of the expectation values of local fields of any interacting quantum theory after a global quench process are key quantities for matching theoretical and experimental results. For quantum integrable field theories, we show that they can be obtained by an ensemble average that employs a particular limit of the form factors of local fields and quantities extracted by the generalized Bethe ansatz.
Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.
2016-01-01
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu–Goldstone modes and massive Anderson–Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble–Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition. PMID:27503886
Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.
2016-08-01
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition.
Quenching of semiconductor quantum dot photoluminescence by a pi-conjugated polymer.
Selmarten, Donald; Jones, Marcus; Rumbles, Garry; Yu, Pingrong; Nedeljkovic, Jovan; Shaheen, Sean
2005-08-25
In this communication we discuss the possibility of hole transfer between a photoexcited semiconductor quantum dot and a pi-conjugated polymer. This charge-transfer event will be investigated (exploited) on the basis of its implication toward a solar energy conversion scheme. Experimentally, we show that the steady-state photoluminescence (PL) of a solution of InP quantum dots is quenched by the introduction of solvated poly(3-hexylthiophene). Time-resolved PL experiments on these solutions are also presented. It was observed that the PL transients did not significantly change upon the addition of the conductive polymer. These new results indicate that said PL quenching is static in nature. This suggests that in solution, the quantum dot and the polymer exhibit a strong intermolecular interaction. As the two species encounter each other through diffusion, the polymer quenches the quantum dot photoluminescence without altering the population's PL lifetime. This new evidence suggests that the polymer and the quantum dot form a relatively stable complex.
Near-infrared induced optical quenching effects on mid-infrared quantum cascade lasers
Energy Technology Data Exchange (ETDEWEB)
Guo, Dingkai, E-mail: dingk1@umbc.edu; Talukder, Muhammad Anisuzzaman; Chen, Xing [Department of Computer Science and Electrical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Cai, Hong [Center of Advanced Studies in Photonics Research (CASPR), University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Johnson, Anthony M.; Choa, Fow-Sen [Department of Computer Science and Electrical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Center of Advanced Studies in Photonics Research (CASPR), University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Khurgin, Jacob B. [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
2014-06-23
In space communications, atmospheric absorption and Rayleigh scattering are the dominant channel impairments. Transmission using mid-infrared (MIR) wavelengths offers the benefits of lower loss and less scintillation effects. In this work, we report the telecom wavelengths (1.55 μm and 1.3 μm) induced optical quenching effects on MIR quantum cascade lasers (QCLs), when QCLs are operated well above their thresholds. The QCL output power can be near 100% quenched using 20 mW of near-infrared (NIR) power, and the quenching effect depends on the input NIR intensity as well as wavelength. Time resolved measurement was conducted to explore the quenching mechanism. The measured recovery time is around 14 ns, which indicates that NIR generated electron-hole pairs may play a key role in the quenching process. The photocarrier created local field and band bending can effectively deteriorate the dipole transition matrix element and quench the QCL. As a result, MIR QCLs can be used as an optical modulator and switch controlled by NIR lasers. They can also be used as “converters” to convert telecom optical signals into MIR optical signals.
NASA MSFC Electrostatic Levitator (ESL) Rapid Quench System
SanSoucie, Michael P.; Craven, Paul D.
2014-01-01
Electrostatic levitation, a form of containerless processing, is an important tool in materials research. Levitated specimens are free from contact with a container; therefore, heterogeneous nucleation on container walls is not possible. This allows studies of deeply undercooled melts. Furthermore, studies of high-temperature, highly reactive materials are also possible. Studies of the solidification and crystallization of undercooled melts is vital to the understanding of microstructure development, particularly the formation of alloys with unique properties by rapid solidification. The NASA Marshall Space Flight Center (MSFC) Electrostatic Levitator (ESL) lab has recently been upgraded to allow for rapid quenching of levitated materials. The ESL Rapid Quench System uses a small crucible-like vessel that can be partially filled with a low melting point material, such as a Gallium alloy, as a quench medium. An undercooled sample can be dropped into the vessel to rapidly quench the sample. A carousel with nine vessels sits below the bottom electrode assembly. This system allows up to nine rapid quenches before having to break vacuum and remove the vessels. This new Rapid Quench System will allow materials science studies of undercooled materials and new materials development. In this presentation, the system is described and initial results are presented.
Entrapment in phospholipid vesicles quenches photoactivity of quantum dots
Generalov R; Kavaliauskiene S; Westrøm S; Chen W; Kristensen S; Juzenas P
2011-01-01
Roman Generalov1,2, Simona Kavaliauskiene1, Sara Westrøm1, Wei Chen3, Solveig Kristensen2, Petras Juzenas11Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; 2School of Pharmacy, University of Oslo, Oslo, Norway; 3Department of Physics, The University of Texas at Arlington, Arlington, TX, USAAbstract: Quantum dots have emerged with great promise for biological applications as fluorescent markers for imm...
Exact solution for the quench dynamics of a nested integrable system
Mestyán, Márton; Bertini, Bruno; Piroli, Lorenzo; Calabrese, Pasquale
2017-08-01
Integrable models provide an exact description for a wide variety of physical phenomena. For example nested integrable systems contain different species of interacting particles with a rich phenomenology in their collective behavior, which is the origin of the unconventional phenomenon of spin-charge separation. So far, however, most of the theoretical work in the study of non-equilibrium dynamics of integrable systems has focussed on models with an elementary (i.e. not nested) Bethe ansatz. In this work we explicitly investigate quantum quenches in nested integrable systems, by generalizing the application of the quench action approach. Specifically, we consider the spin-1 Lai-Sutherland model, described, in the thermodynamic limit, by the theory of two different species of Bethe-ansatz particles, each one forming an infinite number of bound states. We focus on the situation where the quench dynamics starts from a simple matrix product state for which the overlaps with the eigenstates of the Hamiltonian are known. We fully characterize the post-quench steady state and perform several consistency checks for the validity of our results. Finally, we provide predictions for the propagation of entanglement and mutual information after the quench, which can be used as signature of the quasi-particle content of the model.
First experience with the new Coupling Loss Induced Quench system
Ravaioli, E; Dudarev, A V; Kirby, G; Sperin, K A; ten Kate, H H J; Verweij, A P
2014-01-01
New-generation high-field superconducting magnets pose a challenge relating to the protection of the coil winding pack in the case of a quench. The high stored energy per unit volume calls for a very efficient quench detection and fast quench propagation in order to avoid damage due to overheating. A new protection system called Coupling-Loss Induced Quench (CLIQ) was recently, developed and tested at CERN. This method provokes a fast change in the magnet transport current by means of a capacitive discharge. The resulting change in the local magnetic field induces inter-filament and inter-strand coupling losses which heat up the superconductor and eventually initiate a quench in a large fraction of the coil winding pack. The method is extensively tested on a Nb-Ti single-wire test solenoid magnet in the CERN Cryogenic Laboratory in order to assess its performance, optimize its operating parameters, and study new electrical configurations. Each parameter is thoroughly analyzed and its impact on the quench effi...
Prethermalization in a Nonintegrable Quantum Spin Chain after a Quench
Marcuzzi, Matteo; Marino, Jamir; Gambassi, Andrea; Silva, Alessandro
2013-11-01
We study the dynamics of a quantum Ising chain after the sudden introduction of a nonintegrable long-range interaction. Via an exact mapping onto a fully connected lattice of hard-core bosons, we show that a prethermal state emerges and we investigate its features by focusing on a class of physically relevant observables. In order to gain insight into the eventual thermalization, we outline a diagrammatic approach which complements the study of the previous quasistationary state and provides the basis for a self-consistent solution of the kinetic equation. This analysis suggests that both the temporal decay towards the prethermal state and the crossover to the eventual thermal one may occur algebraically.
Holographic geometry of cMERA for quantum quenches and finite temperature
Mollabashi, Ali; Naozaki, Masahiro; Ryu, Shinsei; Takayanagi, Tadashi
2014-03-01
We study the time evolution of cMERA (continuous MERA) under quantum quenches in free field theories. We calculate the corresponding holographic metric using the proposal in arXiv:1208.3469 and confirm that it qualitatively agrees with its gravity dual given by a half of the AdS black hole spacetime, argued by Hartman and Maldacena in arXiv:1303.1080. By doubling the cMERA for the quantum quench, we give an explicit construction of finite temperature cMERA. We also study cMERA in the presence of chemical potential and show that there is an enhancement of metric in the infrared region corresponding to the Fermi energy.
Holographic geometry of cMERA for quantum quenches and finite temperature
Energy Technology Data Exchange (ETDEWEB)
Mollabashi, Ali [School of physics, Institute for Research in Fundamental Sciences (IPM),Tehran (Iran, Islamic Republic of); Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Naozaki, Masahiro [Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Ryu, Shinsei [Department of Physics, University of Illinois at Urbana-Champaign,1110 West Green St, Urbana IL 61801 (United States); Takayanagi, Tadashi [Yukawa Institute for Theoretical Physics, Kyoto University,Kyoto 606-8502 (Japan); Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo,Kashiwa, Chiba 277-8582 (Japan)
2014-03-21
We study the time evolution of cMERA (continuous MERA) under quantum quenches in free field theories. We calculate the corresponding holographic metric using the proposal in http://arxiv.org/abs/1208.3469 and confirm that it qualitatively agrees with its gravity dual given by a half of the AdS black hole spacetime, argued by Hartman and Maldacena in http://arxiv.org/abs/1303.1080. By doubling the cMERA for the quantum quench, we give an explicit construction of finite temperature cMERA. We also study cMERA in the presence of chemical potential and show that there is an enhancement of metric in the infrared region corresponding to the Fermi energy.
Thermalization and revivals after a quantum quench in conformal field theory.
Cardy, John
2014-06-06
We consider a quantum quench in a finite system of length L described by a 1+1-dimensional conformal field theory (CFT), of central charge c, from a state with finite energy density corresponding to an inverse temperature β≪L. For times t such that ℓ/2
Old and New Scaling Laws in Quantum Quench
Das, Sumit R
2016-01-01
The response of a many body system to a time dependent coupling which passes through or approaches a critical point displays universal scaling behavior. In some regimes, scaling laws have been known since the 1970's. Recently holographic techniques have been used to understand the origins of such scaling. Along the way, new scaling behaviors in other regimes have been found in holographic models, which have later been shown to hold in a generic field theory regardless of holography. This contribution summarizes recent work on these various scaling regimes.
Burgarth, Daniel; Yuasa, Kazuya
2011-01-01
The aim of quantum system identification is to estimate the ingredients inside a black box, in which some quantum-mechanical unitary process takes place, by just looking at its input-output behavior. Here we establish a basic and general framework for quantum system identification, that allows us to classify how much knowledge about the quantum system is attainable, in principle, from a given experimental setup. Prior knowledge on some elements of the black box helps the system identification...
Rotational Quenching Study in Isovalent H+ + CO and H+ + CS Systems
Kaur, Rajwant; Dhilip Kumar, T. J.
2016-06-01
Cooling and trapping of polar molecules has attracted attention at cold and ultracold temperatures. Extended study of molecular inelastic collision processes of polar interstellar species with proton finds an important astrophysical application to model interstellar medium. Present study includes computation of rate coefficient for molecular rotational quenching process in proton collision with isovalent CO and CS molecules using quantum dynamical close-coupling calculations. Full dimensional ab initio potential energy surfaces have been computed for the ground state for both the systems using internally contracted multireference configuration interaction method and basis sets. Quantum scattering calculations for rotational quenching of isovalent species are studied in the rigid-rotor approximation with CX (X=O, S) bond length fixed at an experimental equilibrium value of 2.138 and 2.900 a.u., respectively. Asymptotic potentials are computed using the dipole and quadrupole moments, and the dipole polarizability components. The resulting long-range potentials with the short-range ab initio interaction potentials have been fitted to study the anisotropy of the rigid-rotor surface using the multipolar expansion coefficients. Rotational quenching cross-section and corresponding rates from j=4 level of CX to lower j' levels have been obtained and found to obey Wigner's threshold law at ultra cold temperatures.
Enhancement of Charge Transfer and Quenching of Photoluminescence of Capped CdS Quantum Dots
Mehata, Mohan Singh
2015-07-01
Quantum dots (Q-dots) of cadmium sulfide (CdS) with three different capping ligands, 1-butanethiol (BT), 2-mercaptoethanol (ME) and benzyl mercaptan (BM) have been investigated. An external electric field of variable strength of 0.2-1.0 MV cm-1 was applied to the sample of capped CdS Q-dots doped in a poly(methyl methacrylate) (PMMA) films. Field-induced changes in optical absorption of capped CdS Q-dots were observed in terms of purely the second-derivative of the absorption spectrum (the Stark shift), indicating an enhancement in electric dipole moment following transition to the first exciton state. The enhancement depends on the shape and size of the Q-dots prepared using different capping ligands. Field induced-change in photoluminescence (PL) reveals similar changes, an enhancement in charge-transfer (CT) character in exciton state. PL of capped CdS Q-dots is significantly quenched in presence of external electric field. The strong field-induced quenching occurs as a result of the increased charge separation resulting exciton dissociation. Thus, understanding the CT character and field-induced PL quenching of CdS Q-dots is important for photovoltaic, LEDs and biological applications.
Advanced quantum communication systems
Jeffrey, Evan Robert
Quantum communication provides several examples of communication protocols which cannot be implemented securely using only classical communication. Currently, the most widely known of these is quantum cryptography, which allows secure key exchange between parties sharing a quantum channel subject to an eavesdropper. This thesis explores and extends the realm of quantum communication. Two new quantum communication protocols are described. The first is a new form of quantum cryptography---relativistic quantum cryptography---which increases communication efficiency by exploiting a relativistic bound on the power of an eavesdropper, in addition to the usual quantum mechanical restrictions intrinsic to quantum cryptography. By doing so, we have observed over 170% improvement in communication efficiency over a similar protocol not utilizing relativity. A second protocol, Quantum Orienteering, allows two cooperating parties to communicate a specific direction in space. This application shows the possibility of using joint measurements, or projections onto an entangled state, in order to extract the maximum useful information from quantum bits. For two-qubit communication, the maximal fidelity of communication using only separable operations is 73.6%, while joint measurements can improve the efficiency to 78.9%. In addition to implementing these protocols, we have improved several resources for quantum communication and quantum computing. Specifically, we have developed improved sources of polarization-entangled photons, a low-loss quantum memory for polarization qubits, and a quantum random number generator. These tools may be applied to a wide variety of future quantum and classical information systems.
Banerjee, D; Dalmonte, M; Müller, M; Rico, E; Stebler, P; Wiese, U-J; Zoller, P
2012-10-26
Using a Fermi-Bose mixture of ultracold atoms in an optical lattice, we construct a quantum simulator for a U(1) gauge theory coupled to fermionic matter. The construction is based on quantum links which realize continuous gauge symmetry with discrete quantum variables. At low energies, quantum link models with staggered fermions emerge from a Hubbard-type model which can be quantum simulated. This allows us to investigate string breaking as well as the real-time evolution after a quench in gauge theories, which are inaccessible to classical simulation methods.
Banerjee D.; Dalmonte M.; Muller M; Rico E.; Stebler P.; Wiese U.-J.; Zoller P.
2012-01-01
Using a Fermi-Bose mixture of ultra-cold atoms in an optical lattice, we construct a quantum simulator for a U(1) gauge theory coupled to fermionic matter. The construction is based on quantum links which realize continuous gauge symmetry with discrete quantum variables. At low energies, quantum link models with staggered fermions emerge from a Hubbard-type model which can be quantum simulated. This allows us to investigate string breaking as well as the real-time evolution after a quench in ...
Fluctuation theorem in dynamical systems with quenched disorder
Drocco, Jeffrey; Olson Reichhardt, Cynthia; Reichhardt, Charles
2010-03-01
We demonstrate that the fluctuation theorem of Gallavotti and Cohen can be used to characterize far from equilibrium dynamical nonthermal systems in the presence of quenched disorder where strong fluctuations or crackling noise occur. By observing the frequency of entropy-destroying trajectories, we show that the theorem holds in specific dynamical regimes near the threshold for motion, indicating that these systems might be ideal candidates for understanding what types of nonthermal fluctuations could be used in constructing generalized fluctuation theorems. We also discuss how the theorem could be tested with global or local probes in systems such as superconducting vortices, magnetic domain walls, stripe phases, Coulomb glasses and earthquake models.
Open quantum system identification
Schirmer, Sophie G; Zhou, Weiwei; Gong, Erling; Zhang, Ming
2012-01-01
Engineering quantum systems offers great opportunities both technologically and scientifically for communication, computation, and simulation. The construction and operation of large scale quantum information devices presents a grand challenge and a major issue is the effective control of coherent dynamics. This is often in the presence of decoherence which further complicates the task of determining the behaviour of the system. Here, we show how to determine open system Markovian dynamics of a quantum system with restricted initialisation and partial output state information.
Sorting quantum systems efficiently
Ionicioiu, Radu
2016-05-01
Measuring the state of a quantum system is a fundamental process in quantum mechanics and plays an essential role in quantum information and quantum technologies. One method to measure a quantum observable is to sort the system in different spatial modes according to the measured value, followed by single-particle detectors on each mode. Examples of quantum sorters are polarizing beam-splitters (PBS) – which direct photons according to their polarization – and Stern-Gerlach devices. Here we propose a general scheme to sort a quantum system according to the value of any d-dimensional degree of freedom, such as spin, orbital angular momentum (OAM), wavelength etc. Our scheme is universal, works at the single-particle level and has a theoretical efficiency of 100%. As an application we design an efficient OAM sorter consisting of a single multi-path interferometer which is suitable for a photonic chip implementation.
Design and Implementation of Quench Protection in the EAST Cryogenic Control System
Institute of Scientific and Technical Information of China (English)
ZHOU Zhiwei; BAI Hongyu; ZHUANG Ming; HU Liangbing; XIA Genhai
2009-01-01
An outline of the complete design of the cryogenic system, including the detection of quench signals, the processing flow after a quench and the concrete measures of pressure release for EAST is described in this paper. The hardware and software configurations on DeltaV DCS are illustrated in detail. The results of quench protection testing in cooling experiments are also analyzed.
Quantum coherence and correlations in quantum system
Xi, Zhengjun; Li, Yongming; Fan, Heng
2015-01-01
Criteria of measure quantifying quantum coherence, a unique property of quantum system, are proposed recently. In this paper, we first give an uncertainty-like expression relating the coherence and the entropy of quantum system. This finding allows us to discuss the relations between the entanglement and the coherence. Further, we discuss in detail the relations among the coherence, the discord and the deficit in the bipartite quantum system. We show that, the one-way quantum deficit is equal to the sum between quantum discord and the relative entropy of coherence of measured subsystem. PMID:26094795
Ivanov, Mikhail; Dubernet, Marie-Lise; Babikov, Dmitri
2014-04-07
The mixed quantum/classical theory (MQCT) formulated in the space-fixed reference frame is used to compute quenching cross sections of several rotationally excited states of water molecule by impact of He atom in a broad range of collision energies, and is tested against the full-quantum calculations on the same potential energy surface. In current implementation of MQCT method, there are two major sources of errors: one affects results at energies below 10 cm(-1), while the other shows up at energies above 500 cm(-1). Namely, when the collision energy E is below the state-to-state transition energy ΔE the MQCT method becomes less accurate due to its intrinsic classical approximation, although employment of the average-velocity principle (scaling of collision energy in order to satisfy microscopic reversibility) helps dramatically. At higher energies, MQCT is expected to be accurate but in current implementation, in order to make calculations computationally affordable, we had to cut off the basis set size. This can be avoided by using a more efficient body-fixed formulation of MQCT. Overall, the errors of MQCT method are within 20% of the full-quantum results almost everywhere through four-orders-of-magnitude range of collision energies, except near resonances, where the errors are somewhat larger.
Controllability of Quantum Systems
Schirmer, S G; Solomon, A I
2003-01-01
An overview and synthesis of results and criteria for open-loop controllability of Hamiltonian quantum systems obtained using Lie group and Lie algebra techniques is presented. Negative results for open-loop controllability of dissipative systems are discussed, and the superiority of closed-loop (feedback) control for quantum systems is established.
First experience with the new coupling loss induced quench system
Ravaioli, E.; Datskov, V.I.; Dudarev, A.V.; Kirby, G.; Sperin, K.A.; Kate, ten H.H.J.; Verweij, A.P.
2014-01-01
New-generation high-ﬁeld superconducting magnets pose a challenge relating to the protection of the coil winding pack in the case of a quench. The high stored energy per unit volume calls for a very efﬁcient quench detection and fast quench propagation in order to avoid damage due to overheating. A
Energy Technology Data Exchange (ETDEWEB)
Liu, Qi; Huang, Aizhen; Wang, Nan, E-mail: nwang@hust.edu.cn; Zheng, Guan; Zhu, Lihua
2015-05-15
Analysis of perfluorooctanoic acid (PFOA) usually requires a combination of high-performance liquid chromatography and mass spectrometry, which is expensive and time-consuming. In the present work, water-soluble CdS quantum dots (QDs) were employed to develop a simple and rapid fluorometric method for the determination of PFOA. Strongly fluorescent CdS QDs were prepared by using 3-mercaptopropionic acid (MPA) as a stabilizer. It was observed that PFOA strongly quenched the fluorescence emission of the MPA-CdS QDs because PFOA promotes the aggregation of MPA-CdS QDs through a fluorine–fluorine affinity interaction. Under optimum conditions, the fluorescence intensity of MPA-CdS QDs was observed to decrease linearly with an increase in the concentration of PFOA from 0.5 to 40 μmol L{sup −1}, with a limit of detection of 0.3 μmol L{sup −1}. This new method was successfully implemented for the analysis of PFOA-spiked textile samples, with recoveries ranging from 95% to 113%. - Highlights: • PFOA significantly quenched the fluorescence emission of quantum dots (QDs). • A rapid and simple fluorescence sensor was proposed for determining PFOA by QDs. • PFOA determination could be completed within approximately 10 min. • The developed method had a working range of 0.5 to 40 μmol L{sup −1} and a detection limit of 0.3 μmol L{sup −1}.
Quantum system identification.
Burgarth, Daniel; Yuasa, Kazuya
2012-02-24
The aim of quantum system identification is to estimate the ingredients inside a black box, in which some quantum-mechanical unitary process takes place, by just looking at its input-output behavior. Here we establish a basic and general framework for quantum system identification, that allows us to classify how much knowledge about the quantum system is attainable, in principle, from a given experimental setup. We show that controllable closed quantum systems can be estimated up to unitary conjugation. Prior knowledge on some elements of the black box helps the system identification. We present an example in which a Bell measurement is more efficient to identify the system. When the topology of the system is known, the framework enables us to establish a general criterion for the estimability of the coupling constants in its Hamiltonian.
Fluctuation theorem in driven nonthermal systems with quenched disorder
Energy Technology Data Exchange (ETDEWEB)
Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, C J [Los Alamos National Laboratory; Drocco, J A [PRINCETON UNIV.
2009-01-01
We demonstrate that the fluctuation theorem of Evans and Searles can be used to characterize the class of dynamics that arises in nonthermal systems of collectively interacting particles driven over random quenched disorder. By observing the frequency of entropy-destroying trajectories, we show that there are specific dynamical regimes near depinning in which this theorem holds. Hence the fluctuation theorem can be used to characterize a significantly wider class of non-equilibrium systems than previously considered. We discuss how the fluctuation theorem could be tested in specific systems where noisy dynamics appear at the transition from a pinned to a moving phase such as in vortices in type-II superconductors, magnetic domain walls, and dislocation dynamics.
Li, Jingzhou; Dong, Hongxing; Zhang, Saifeng; Ma, Yunfei; Wang, Jun; Zhang, Long
2016-09-28
Two-photon (TP) three-dimensional solid matrices have potential applications in high density optical data reading and storage, infrared-pumped visible displays, lasers, etc. Such technologies will benefit greatly from the advantageous properties of TP materials including tunable emission wavelength, photostability, and simple chemical processing. Here, this ideal TP solid is made possible by using a facile sol-gel process to engineer colloid quantum dots into silica gel glass. Characterization using an open-aperture Z-scan technique shows that the solid matrices exhibited significant TP optical properties with a TP absorption coefficient of (9.41 ± 0.39) × 10(-2) cm GW(-1) and a third-order nonlinear figure of merit of (7.30 ± 0.30) × 10(-14) esu cm. In addition, the dependence of the TP properties on high-temperature thermal treatment is studied in detail to obtain a clear insight for practical applications. The results illustrate that the sample can maintain stable TP performance below the synthesis temperature of the CdTe/CdS colloidal quantum dots. Furthermore, the mechanisms for thermal quenching of photoluminescence under different temperature regimes are clarified as a function of the composition.
Mandal, Gautam
2013-01-01
Quantum quench dynamics is considered in a one dimensional unitary matrix model with a single trace potential. This model is integrable and has been studied in the context of non-critical string theory. We find dynamical phase transitions, and study the role of the quantum critical point. In course of the time evolutions, we find evidence of selective equilibration for a certain class of observables. The equilibrium is governed by the Generalized Gibbs Ensemble (GGE) and differs from the standard Gibbs ensemble. We compute the production of entropy which is O(N) for large N matrices. An important feature of the equilibration is the appearance of an energy cascade, reminiscent of the Richardson cascade in turbulence, where we find flow of energy from initial long wavelength modes to progressively shorter wavelength excitations. We discuss possible implication of the equilibration and of GGE in string theories and higher spin theories. In another related study, we compute time evolutions in a double trace unita...
Dusek, Miloslav; Haderka, Ondrej; Hendrych, Martin; Myska, Robert
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 ``refuelled'' from a shared provably secret key transferred through the quantum channel. Two identification protocols are devised. The first protocol can be applied when legitimate users have an unjammable public channel at their disposal. The deception probability is derived for the case of ...
Light quenching and dark states in colloidal solutions of semiconductor CdSe/ZnS quantum dots
Danilov, V. V.; Panfutova, A. S.; Shilov, V. B.; Belousova, I. M.; Ermolaeva, G. M.; Khrebtov, A. I.
2014-06-01
The photodynamics of optical limiting in colloidal solutions of different-size CdSe/ZnS quantum dots is studied. The behavior of the dependences points to a multistage process that includes the bleaching and optical limiting stages. The limiting photodynamics is compared with luminescence dynamics of quantum dots under conditions of high-power excitation. It is shown that the optical limiting efficiency in such media is determined by the position of exciting radiation with respect to the main exciton absorption band of the quantum dot. The roles played by so-called dark states and light quenching in limiting photodynamics are discussed.
Holographic study on the jet quenching parameter in anisotropic systems
Wang, Luying
2016-01-01
We first calculate the jet quenching parameter of an anisotropic plasma with a U(1) chemical potential via the AdS/CFT duality. The effects of charge, anisotropy parameter and quark motion direction on the jet quenching parameter are investigated. We then discuss the situation of anisotropic black brane in the IR region. We study both the jet quenching parameters along the longitudinal direction and transverse plane.
Holographic study of the jet quenching parameter in anisotropic systems
Energy Technology Data Exchange (ETDEWEB)
Wang, Luying [Shanghai University, Department of Physics, Shanghai (China); Wu, Shang-Yu [National Chiao Tung University, Department of Electrophysics, Hsinchu (China)
2016-11-15
We first calculate the jet quenching parameter of an anisotropic plasma with a U(1) chemical potential via AdS/CFT duality. The effects of charge, anisotropy parameter, and quark motion direction on the jet quenching parameter are investigated. We then discuss the situation of an anisotropic black brane in the IR region. We study both the jet quenching parameters along the longitudinal direction and the transverse plane. (orig.)
Raginsky, M
2003-01-01
We formulate and study, in general terms, the problem of quantum system identification, i.e., the determination (or estimation) of unknown quantum channels through their action on suitably chosen input density operators. We also present a quantitative analysis of the worst-case performance of these schemes.
Burgarth, Daniel
2011-01-01
The aim of quantum system identification is to estimate the ingredients inside a black box, in which some quantum-mechanical unitary process takes place, by just looking at its input-output behavior. Here we establish a basic and general framework for quantum system identification, that allows us to classify how much knowledge about the quantum system is attainable, in principle, from a given experimental setup. Prior knowledge on some elements of the black box helps the system identification. We present an example in which a Bell measurement is more efficient to identify the system. When the topology of the system is known, the framework enables us to establish a general criterion for the estimability of the coupling constants in its Hamiltonian.
Weiss, Ulrich
2008-01-01
Major advances in the quantum theory of macroscopic systems, in combination with stunning experimental achievements, have brightened the field and brought it to the attention of the general community in natural sciences. Today, working knowledge of dissipative quantum mechanics is an essential tool for many physicists. This book - originally published in 1990 and republished in 1999 as an enlarged second edition - delves much deeper than ever before into the fundamental concepts, methods, and applications of quantum dissipative systems, including the most recent developments. In this third edi
Weiss, Ulrich
1993-01-01
This book deals with the statistical mechanics and dynamics of open quantum systems moving irreversibly under the influence of a dissipative environment. The basic concepts and methods are described on the basis of a microscopic description with emphasis on the functional integral approach. The general theory for the time evolution of the density matrix of the damped system is developed. Many of the sophisticated ideas in the field are explained with simple models. The discussion includes, among others, the interplay between thermal and quantum fluctuations, quantum statistical decay, macrosco
Energy Technology Data Exchange (ETDEWEB)
Borissevitch, I.E., E-mail: iourib@ffclrp.usp.br [Departamento de Fisica, Faculdade de Filosofia Ciencia e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes 3900, Ribeirao Preto, SP (Brazil); Parra, G.G. [Departamento de Fisica, Faculdade de Filosofia Ciencia e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes 3900, Ribeirao Preto, SP (Brazil); Zagidullin, V.E.; Lukashev, E.P.; Knox, P.P.; Paschenko, V.Z.; Rubin, A.B. [Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Vorobyovy Gory, 119991 Moscow (Russian Federation)
2013-02-15
In this work we report on the study of the interaction of CdSe/ZnS-PEGOH 570 Quantum Dot (QD) with negatively charged meso-tetrakis(p-sulfonato-phenyl)porphyrin (TPPS{sub 4}) using optical absorption and fluorescence spectroscopies accompanied with time resolved 'single photon counting' and dynamic and resonance light scattering techniques. In the steady-state experiments the QD luminescence quenching by TPPS{sub 4} was well approximated by a square law. In the time-resolved experiments we observed a typical multi-exponential luminescence decay curve, successfully fitted by a bi-exponential approximation. At QD interaction with porphyrin the time quenching of both components was described by a linear Stern-Volmer dependence. The discrepancy between Stern-Volmer dependences in the steady-state and time resolved experiments may be due to formation of mixed m(TPPS{sub 4})+n(QD) complexes, in which one TPPS{sub 4} molecule can quench several excited QDs. This idea is in accordance with the dynamic and resonance light scattering data, which demonstrate an increase of the scattering particle size at the TPPS{sub 4} addition to QD solutions. - Highlights: Black-Right-Pointing-Pointer Quantum Dot luminescence quenching by TPPS porphyrin was studied in water solutions. Black-Right-Pointing-Pointer The size of particles in QD solutions possessed increase at the TPPS4 addition. Black-Right-Pointing-Pointer Quenching of the QD luminescence by TPPS4 is realized in contact QD-porphyrin complexes. Black-Right-Pointing-Pointer The formation of mixed quantum dot-porphyrin aggregates takes place.
Finite and profinite quantum systems
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 ...
Equilibration and GGE in interacting-to-free Quantum Quenches in dimensions $d>1$
Sotiriadis, Spyros
2016-01-01
Ground states of interacting QFTs are non-gaussian states, i.e. their connected n-point correlation functions do not vanish for n>2, in contrast to the free QFT case. We show that when the ground state of an interacting QFT evolves under a free massive QFT for a long time (a scenario that can be realised by a Quantum Quench), the connected correlation functions decay and all local physical observables equilibrate to values that are given by a gaussian density matrix that keeps memory only of the two-point initial correlation function. The argument hinges upon the fundamental physical principle of cluster decomposition, which is valid for the ground state of a general QFT. An analogous result was already known to be valid in the case of d=1 spatial dimensions, where it is a special case of the so-called Generalised Gibbs Ensemble (GGE) hypothesis, and we now generalise it to higher dimensions. Moreover in the case of massless free evolution, despite the fact that the evolution may not lead to equilibration but...
Energy Technology Data Exchange (ETDEWEB)
Rivasseau, Vincent [Paris-Sud Univ. Orsay (France). Laboratoire de Physique Theorique; Seiringer, Robert [McGill Univ., Montreal, QC (Canada). Dept. of Mathematics and Statistics; Solovej, Jan Philip [Copenhagen Univ. (Denmark). Dept. of Mathematics; Spencer, Thomas [Institute for Advanced Study, Princeton, NJ (United States). School of Mathematics
2012-11-01
The book is based on the lectures given at the CIME school ''Quantum many body systems'' held in the summer of 2010. It provides a tutorial introduction to recent advances in the mathematics of interacting systems, written by four leading experts in the field: V. Rivasseau illustrates the applications of constructive Quantum Field Theory to 2D interacting electrons and their relation to quantum gravity; R. Seiringer describes a proof of Bose-Einstein condensation in the Gross-Pitaevski limit and explains the effects of rotating traps and the emergence of lattices of quantized vortices; J.-P. Solovej gives an introduction to the theory of quantum Coulomb systems and to the functional analytic methods used to prove their thermodynamic stability; finally, T. Spencer explains the supersymmetric approach to Anderson localization and its relation to the theory of random matrices. All the lectures are characterized by their mathematical rigor combined with physical insights.
Relaxation of the entanglement spectrum in quench dynamics of topological systems
Jhu, Yi-Hao; Chen, Pochung; Chung, Ming-Chiang
2017-07-01
In this paper, we investigate how the entanglement spectrum relaxes to its steady-state values in one-dimensional quadratic systems after a quantum quench. In particular, we apply saddle-point expansion to dimerized chains and 1D p-wave superconductors. We found the entanglement spectrum to always exhibit a power-law relaxation superimposed with oscillations at certain characteristic angular frequencies. For dimerized chains, we found the exponent ν of the power-law decay to always be 3/2 . For 1D p-wave superconductors, however, we found that, depending on the initial and final Hamiltonian, the exponent ν can take its value from a limited list of values, the smallest possible of which is ν=1/2 , which leads to a very slow convergence to its steady-state value.
Energy Extracting and Quench Protection System in the LHC
Abu Siam, Mansour
2016-01-01
quadrupole magnets. The electromagnets are built of special cables that operate in superconducting state by cooling them to 1.9K (-271.3℃); the superconducting magnets of the LHC are powered in about 1700 electrical circuits. A phenomenon called quench can spontaneously occur in superconducting magnets, which means that the superconductivity is lost in part of their windings. The energy stored within the magnet, up to 1.3 GJ, can cause severe damage. In order to protect the superconducting elements after a resistive transition, the energy is dissipated into a dump resistor installed in series with the magnet chain that is switched into the circuit by opening circuit breakers. The system described above is utilized for magnets installed in the LHC that operate under currents ranging from 600A up to 13kA. For the next LHC upgrade (High Luminosity) there is a need for circuit breakers capable of interrupting high DC currents in a solely inductive circuit within one millisecond and under development of very hig...
Energy Technology Data Exchange (ETDEWEB)
Micheli, Fiorenza de [Centro de Estudios Cientificos, Arturo Prat 514, Valdivia (Chile); Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4059, Valparaiso (Chile); Zanelli, Jorge [Centro de Estudios Cientificos, Arturo Prat 514, Valdivia (Chile); Universidad Andres Bello, Av. Republica 440, Santiago (Chile)
2012-10-15
A degenerate dynamical system is characterized by a symplectic structure whose rank is not constant throughout phase space. Its phase space is divided into causally disconnected, nonoverlapping regions in each of which the rank of the symplectic matrix is constant, and there are no classical orbits connecting two different regions. Here the question of whether this classical disconnectedness survives quantization is addressed. Our conclusion is that in irreducible degenerate systems-in which the degeneracy cannot be eliminated by redefining variables in the action-the disconnectedness is maintained in the quantum theory: there is no quantum tunnelling across degeneracy surfaces. This shows that the degeneracy surfaces are boundaries separating distinct physical systems, not only classically, but in the quantum realm as well. The relevance of this feature for gravitation and Chern-Simons theories in higher dimensions cannot be overstated.
Indian Academy of Sciences (India)
Victor Mukherjee; Uma Divakaran; Amit Dutta; Diptiman Sen
2008-08-01
In this paper we review the quenching dynamics of a quantum spin-1/2 chain in the presence of a transverse field, when the transverse field or the anisotropic interaction is quenched at a slow but uniform rate. We also extend the results to the cases in which the system starts with any arbitrary initial condition as opposed to the initial fully magnetically aligned state which has been extensively studied earlier. The evolution is non-adiabatic in the time interval when the parameters are close to their critical values, and is adiabatic otherwise. The density of defects produced due to non-adiabatic transitions is calculated by mapping the many-particle system to an equivalent Landau–Zener problem. We show that in one dimension the density of defects in the final state scales as $1/\\sqrt{}$ irrespective of the initial condition, where is the quenching time-scale. However, the magnitude of density of defects is found to depend on the initial condition.
Merkl, Jan-Philip; Wolter, Christopher; Flessau, Sandra; Schmidtke, Christian; Ostermann, Johannes; Feld, Artur; Mews, Alf; Weller, Horst
2016-04-14
Detailed steady-state and time-resolved fluorescence quenching measurements give deep insight into ion transport through nanometer thick diblock copolymer membranes, which were assembled as biocompatible shell material around CdSe/CdS quantum dot in quantum rods. We discuss the role of polymer chain length, intermolecular cross-linking and nanopore formation by analysing electron transfer processes from the photoexcited QDQRs to Cu(II) ions, which accumulate in the polymer membrane. Fluorescence investigations on single particle level additionally allow identifying ensemble inhomogeneities.
Quantum Cybernetics and Complex Quantum Systems Science - A Quantum Connectionist Exploration
Gonçalves, Carlos Pedro
2014-01-01
Quantum cybernetics and its connections to complex quantum systems science is addressed from the perspective of complex quantum computing systems. In this way, the notion of an autonomous quantum computing system is introduced in regards to quantum artificial intelligence, and applied to quantum artificial neural networks, considered as autonomous quantum computing systems, which leads to a quantum connectionist framework within quantum cybernetics for complex quantum computing systems. Sever...
Quantum Cybernetics and Complex Quantum Systems Science - A Quantum Connectionist Exploration
Gonçalves, Carlos Pedro
2014-01-01
Quantum cybernetics and its connections to complex quantum systems science is addressed from the perspective of complex quantum computing systems. In this way, the notion of an autonomous quantum computing system is introduced in regards to quantum artificial intelligence, and applied to quantum artificial neural networks, considered as autonomous quantum computing systems, which leads to a quantum connectionist framework within quantum cybernetics for complex quantum computing systems. Sever...
Scheme of thinking quantum systems
Yukalov, V I
2009-01-01
A general approach describing quantum decision procedures is developed. The approach can be applied to quantum information processing, quantum computing, creation of artificial quantum intelligence, as well as to analyzing decision processes of human decision makers. Our basic point is to consider an active quantum system possessing its own strategic state. Processing information by such a system is analogous to the cognitive processes associated to decision making by humans. The algebra of probability operators, associated with the possible options available to the decision maker, plays the role of the algebra of observables in quantum theory of measurements. A scheme is advanced for a practical realization of decision procedures by thinking quantum systems. Such thinking quantum systems can be realized by using spin lattices, systems of magnetic molecules, cold atoms trapped in optical lattices, ensembles of quantum dots, or multilevel atomic systems interacting with electromagnetic field.
Scheme of thinking quantum systems
Yukalov, V. I.; Sornette, D.
2009-11-01
A general approach describing quantum decision procedures is developed. The approach can be applied to quantum information processing, quantum computing, creation of artificial quantum intelligence, as well as to analyzing decision processes of human decision makers. Our basic point is to consider an active quantum system possessing its own strategic state. Processing information by such a system is analogous to the cognitive processes associated to decision making by humans. The algebra of probability operators, associated with the possible options available to the decision maker, plays the role of the algebra of observables in quantum theory of measurements. A scheme is advanced for a practical realization of decision procedures by thinking quantum systems. Such thinking quantum systems can be realized by using spin lattices, systems of magnetic molecules, cold atoms trapped in optical lattices, ensembles of quantum dots, or multilevel atomic systems interacting with electromagnetic field.
Santhosh, Kotni; Patra, Satyajit; Soumya, S; Khara, Dinesh Chandra; Samanta, Anunay
2011-10-24
Fluorescence quenching of CdS quantum dots (QDs) by 4-azetidinyl-7-nitrobenz-2-oxa-1,3-diazole (NBD), where the two quenching partners satisfy the spectral overlap criterion necessary for Förster resonance energy transfer (FRET), is studied by steady-state and time-resolved fluorescence techniques. The fluorescence quenching of the QDs is accompanied by an enhancement of the acceptor fluorescence and a reduction of the average fluorescence lifetime of the donor. Even though these observations are suggestive of a dynamic energy transfer process, it is shown that the quenching actually proceeds through a static interaction between the quenching partners and is probably mediated by charge-transfer interactions. The bimolecular quenching rate constant estimated from the Stern-Volmer plot of the fluorescence intensities, is found to be exceptionally high and unrealistic for the dynamic quenching process. Hence, a kinetic model is employed for the estimation of actual quencher/QD ratio dependent exciton quenching rate constants of the fluorescence quenching of CdS by NBD. The present results point to the need for a deeper analysis of the experimental quenching data to avoid erroneous conclusions.
Quantum iterated function systems.
Łoziński, Artur; Zyczkowski, Karol; Słomczyński, Wojciech
2003-10-01
An iterated function system (IFS) is defined by specifying a set of functions in a classical phase space, which act randomly on an initial point. In an analogous way, we define a quantum IFS (QIFS), where functions act randomly with prescribed probabilities in the Hilbert space. In a more general setting, a QIFS consists of completely positive maps acting in the space of density operators. This formalism is designed to describe certain problems of nonunitary quantum dynamics. We present exemplary classical IFSs, the invariant measure of which exhibits fractal structure, and study properties of the corresponding QIFSs and their invariant states.
Nonequilibrium quantum dynamics in optomechanical systems
Patil, Yogesh Sharad; Cheung, Hil F. H.; Shaffer, Airlia; Wang, Ke; Vengalattore, Mukund
2016-05-01
The thermalization dynamics of isolated quantum systems has so far been explored in the context of cold atomic systems containing a large number of particles and modes. Quantum optomechanical systems offer prospects of studying such dynamics in a qualitatively different regime - with few individually addressable modes amenable to continuous quantum measurement and thermalization times that vastly exceed those observed in cold atomic systems. We have experimentally realized a dynamical continuous phase transition in a quantum compatible nondegenerate mechanical parametric oscillator. This system is formally equivalent to the optical parametric amplifiers whose dynamics have been a subject of intense theoretical study. We experimentally verify its phase diagram and observe nonequilibrium behavior that was only theorized, but never directly observed, in the context of optical parametric amplifiers. We discuss prospects of using nonequilibrium protocols such as quenches in optomechanical systems to amplify weak nonclassical correlations and to realize macroscopic nonclassical states. This work was supported by the DARPA QuASAR program through a Grant from the ARO and the ARO MURI on non-equilibrium manybody dynamics.
Cao, Ming; Liu, Meigui; Cao, Chun; Xia, Yunsheng; Bao, Linjun; Jin, Yingqiong; Yang, Song; Zhu, Changqing
2010-03-01
A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5 × 10 -8 and 8.0 × 10 -6 mol L -1 with a detection limit of 6.0 × 10 -9 mol L -1. The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.
Directory of Open Access Journals (Sweden)
Eduard I. Zenkevich
2012-01-01
Full Text Available We review recent experimental work to utilize the size dependence of the luminescence quenching of colloidal semiconductor quantum dots induced by functionalized porphyrin molecules attached to the surface to describe a photoluminescence (PL quenching process which is different from usual models of charge transfer (CT or Foerster resonant energy transfer (FRET. Steady-state and picosecond time-resolved measurements were carried out for nanocomposites based on colloidal CdSe/ZnS and CdSe quantum dots (QDs of various sizes and surfacely attached tetra-mesopyridyl-substituted porphyrin molecules (“Quantum Dot-Porphyrin” nanocomposites, in toluene at 295 K. It was found that the major part of the observed strong quenching of QD PL in “QD-Porphyrin” nanocomposites can neither be assigned to FRET nor to photoinduced charge transfer between the QD and the chromophore. This PL quenching depends on QD size and shell and is stronger for smaller quantum dots: QD PL quenching rate constants scale inversely with the QD diameter. Based on the comparison of experimental data and quantum mechanical calculations, it has been concluded that QD PL quenching in “QD-Porphyrin” nanocomposites can be understood in terms of a tunneling of the electron (of the excited electron-hole pair followed by a (self- localization of the electron or formation of trap states. The major contribution to PL quenching is found to be proportional to the calculated quantum-confined exciton wave function at the QD surface. Our findings highlight that single functionalized molecules can be considered as one of the probes for the complex interface physics and dynamics of colloidal semiconductor QD.
Quantum critical points in quantum impurity systems
Energy Technology Data Exchange (ETDEWEB)
Lee, Hyun Jung [Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Universitaet Augsburg (Germany); Bulla, Ralf [Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Universitaet Augsburg (Germany)]. E-mail: bulla@cpfs.mpg.de
2005-04-30
The numerical renormalization group method is used to investigate zero-temperature phase transitions in quantum impurity systems, in particular in the soft-gap Anderson model, where an impurity couples to a non-trivial fermionic bath. In this case, zero-temperature phase transitions occur between two different phases whose fixed points can be built up of non-interacting single-particle states. However, the quantum critical point cannot be described by non-interacting fermionic or bosonic excitations.
Quantum critical points in quantum impurity systems
Lee, Hyun Jung; Bulla, Ralf
2005-04-01
The numerical renormalization group method is used to investigate zero-temperature phase transitions in quantum impurity systems, in particular in the soft-gap Anderson model, where an impurity couples to a non-trivial fermionic bath. In this case, zero-temperature phase transitions occur between two different phases whose fixed points can be built up of non-interacting single-particle states. However, the quantum critical point cannot be described by non-interacting fermionic or bosonic excitations.
Quench characteristics of 6 T conduction-cooled NbTi magnet system
Kar, S.; Soni, V.; Konduru, P.; Sharma, R. G.; Kanjilal, D.; Datta, T. S.
2015-12-01
Conduction-cooled superconducting magnets are cooled by cryocooler alone through the conductive thermal links. The limited refrigeration capacity and conductive cooling make the magnets more prone to quench. We have studied the quench characteristics of a 6 T conduction-cooled NbTi magnet system in detail in this paper. The NbTi magnet has been designed for 102 A with 31% current margin to achieve 0.8 K temperature margin. During a training quench at 101.2 A, the outer surface of the NbTi magnet reached 53.25 K and the temperature of the 2nd stage cold head of the cryocooler reached 15.8 K. Conductive cooling by the cryocooler makes the post-quench recovery of the NbTi magnet in 40 minutes. The maximum sweep rate is 6 A/min for thermally stable operation of this conduction-cooled NbTi magnet. We have done an intentional quench at a sweep rate of 8 A/min. The maximum hot-spot temperature and the post-quench current decay have been simulated using a finite element analysis (FEA) code. Post-quench distribution of the dumped energy in the different components of the magnet system is also presented.
Energy Technology Data Exchange (ETDEWEB)
Zhou, Jing; Han, Tongqian; Ma, Hongmin; Yan, Tao; Pang, Xuehui [Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China); Li, Yueyun [School of Chemical Engineering, Shandong University of Technology, Zibo 255049 (China); Wei, Qin, E-mail: sdjndxwq@163.com [Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China)
2015-08-19
Nitrogen-doped carbon quantum dots (N-CQDs) with an average diameter of 2 nm were synthesized by carbonization of diethylene triamine pentacetate acid (DTPA). The simple prepared N-CQDs showed excellent electrochemiluminescence (ECL) property and were used as luminophors to fabricate a sandwich-type ECL immunosensor. Aminated graphene (NH{sub 2}-G) was also synthesized and used as a label of secondary antibody. The labeled NH{sub 2}-G could effectively quench the ECL of N-CQDs modified on electrodes due to ECL resonance energy transfer (ERET). Immunological recognition which induced ECL quenching enabled the quantitative determination of biomarkers. Alpha fetoprotein (AFP) was selected as a model analyte to investigate the analytical performance of the proposed immunosensor. Under optimal conditions, a good linear relationship between ECL intensity and the logarithm of AFP concentration was obtained in the range of 0.01–100 ng mL{sup −1} with the detection limit of 3.3 pg mL{sup −1}. The proposed ECL immunosensor showed good stability, acceptable selectivity and reproducibility. - Highlights: • ECL behavior of N-CQDs was investigated. • NH{sub 2}-G for quenching N-CQDs emission was investigated. • The linearly range of the immunosensor for AFP was 0.01 ng/mL–100 ng/mL.
Reduced thermal quenching in indium-rich self-organized InGaN/GaN quantum dots
Elafandy, Rami T.
2012-01-01
Differences in optical and structural properties of indium rich (27), indium gallium nitride (InGaN) self-organized quantum dots (QDs), with red wavelength emission, and the two dimensional underlying wetting layer (WL) are investigated. Temperature dependent micro-photoluminescence (?PL) reveals a decrease in thermal quenching of the QDs integrated intensity compared to that of the WL. This difference in behaviour is due to the 3-D localization of carriers within the QDs preventing them from thermalization to nearby traps causing an increase in the internal quantum efficiency of the device. Excitation power dependent ?PL shows a slower increase of the QDs PL signal compared to the WL PL which is believed to be due to the QDs saturation. © 2012 American Institute of Physics.
Emergent topology and dynamical quantum phase transitions in two-dimensional closed quantum systems
Bhattacharya, Utso; Dutta, Amit
2017-07-01
Dynamical quantum phase transitions (DQPTs) manifested in the nonanalyticities in the temporal evolution of a closed quantum system generated by the time-independent final Hamiltonian, following a quench (or ramping) of a parameter of the Hamiltonian, is an emerging frontier of nonequilibrium quantum dynamics. We, here, introduce the notion of a dynamical topological order parameter (DTOP) that characterizes these DQPTs occurring in quenched (or ramped) two-dimensional closed quantum systems; this is quite a nontrivial generalization of the notion of DTOP introduced in Budich and Heyl [Phys. Rev. B 93, 085416 (2016), 10.1103/PhysRevB.93.085416] for one-dimensional situations. This DTOP is obtained from the "gauge-invariant" Pancharatnam phase extracted from the Loschmidt overlap, i.e., the modulus of the overlap between the initially prepared state and its time-evolved counterpart reached following a temporal evolution generated by the time-independent final Hamiltonian. This generic proposal is illustrated considering DQPTs occurring in the subsequent temporal evolution following a sudden quench of the staggered mass of the topological Haldane model on a hexagonal lattice where it stays fixed to zero or unity and makes a discontinuous jump between these two values at critical times at which DQPTs occur. What is remarkable is that while the topology of the equilibrium model is characterized by the Chern number, the emergent topology associated with the DQPTs is characterized by a generalized winding number.
Phenomenology of Holographic Quenches
da Silva, Emilia; Lopez, Esperanza; Mas, Javier; Serantes, Alexandre
2015-10-01
We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.
Gan, Zhixing; Gui, Qingfeng; Shan, Yun; Pan, Pengfei; Zhang, Ning; Zhang, Lifa
2016-09-01
By cutting MoS2 microcrystals to quantum dots (QDs) of sizes below 10 nm, the photoluminescence (PL) at ca. 450 nm can be detected easily due to the quantum confinement effects across the 2D planes. The PL is stable under continuous irradiation of UV light but gradually quenches when treated with an increasing concentration of hydrogen peroxide. Time-resolved PL and Raman spectra imply that H2O2 causes the partial oxidation of MoS2 QDs. First-principles calculations reveal that the MoS2 QDs with oxygen impurity are of indirect bandgap structures showing no notable PL. And absorption spectra verify that the PL of MoS2 QDs quenched by H2O2 is attributed to the oxidation. The integrated PL intensity and H2O2 concentration show an exponential relationship in the range of 2-20 μM, suggesting that MoS2 QDs are potential fluorescent probes for hydrogen peroxide sensing in a physiological environment.
Quantum Iterated Function Systems
Lozinski, A; Slomczynski, W; Lozinski, Artur; Zyczkowski, Karol; Slomczynski, Wojciech
2003-01-01
Iterated functions system (IFS) is defined by specifying a set of functions in a classical phase space, which act randomly on the initial point. In an analogous way, we define quantum iterated functions system (QIFS), where functions act randomly with prescribed probabilities in the Hilbert space. In a more general setting a QIFS consists of completely positive maps acting in the space of density operators. We present exemplary classical IFSs, the invariant measure of which exhibits fractal structure, and study properties of the corresponding QIFSs and their invariant state.
Iqbal, A
2002-01-01
We find quantum mechanics playing a role in evolutionary dynamics described by the notion of an Evolutionary Stable Strategy (ESS). An ESS being a refinement of Nash equilibrium concept is a stable strategy in an evolutionary game with replicator dynamic as the underlying process. We investigate ESSs in two and three player symmetric quantum games played by the proposed scheme of applying $^{\\prime}$identity$^{\\prime}$ and $^{\\prime}$Pauli spin-flip$^{\\prime}$ operators on an initial state with classical probabilities. The mixed Nash equilibrium (NE) we search for is not affected by a switchover between two forms of the game, one quantized and other classical, however it is an ESS when the game is played classically.We show no such mixed NE exists for two player games but there is a class of three player games where they do exist.Our results imply that an evolutionary approach originating with Darwin's idea of natural selection can be used even for quantum systems. It also indicates the possibility of genetic...
Duality quantum algorithm efficiently simulates open quantum systems
Shi-Jie Wei; Dong Ruan; Gui-Lu Long
2016-01-01
Because of inevitable coupling with the environment, nearly all practical quantum systems are open system, where the evolution is not necessarily unitary. In this paper, we propose a duality quantum algorithm for simulating Hamiltonian evolution of an open quantum system. In contrast to unitary evolution in a usual quantum computer, the evolution operator in a duality quantum computer is a linear combination of unitary operators. In this duality quantum algorithm, the time evolution of the op...
Quantum fluctuations in mesoscopic systems
Benatti, F.; Carollo, F.; Floreanini, R.; Narnhofer, H.
2017-10-01
Recent experimental results point to the existence of coherent quantum phenomena in systems made of a large number of particles, despite the fact that for many-body systems the presence of decoherence is hardly negligible and emerging classicality is expected. This behaviour hinges on collective observables, named quantum fluctuations, that retain a quantum character even in the thermodynamic limit: they provide useful tools for studying properties of many-body systems at the mesoscopic level, in-between the quantum microscopic scale and the classical macroscopic one. We herein present the general theory of quantum fluctuations in mesoscopic systems, and study their dynamics in a quantum open system setting, taking into account the unavoidable effects of dissipation and noise induced by the external environment. As in the case of microscopic systems, decoherence is not always the only dominating effect at the mesoscopic scale: certain types of environment can provide means for entangling collective fluctuations through a purely noisy mechanism.
Semenov, Alexander; Ivanov, Mikhail; Babikov, Dmitri
2013-08-21
The mixed quantum/classical approach is applied to the problem of ro-vibrational energy transfer in the inelastic collisions of CO(v = 1) with He atom, in order to predict the quenching rate coefficient in a broad range of temperatures 5 quantum/classical theory, because the vibrational quantum in CO molecule is rather large and the quencher is very light (He atom). For heavier quenchers and closer to dissociation limit of the molecule, the mixed quantum/classical theory is expected to work even better.
Institute of Scientific and Technical Information of China (English)
周小东; 张少锋; 周思华
2015-01-01
利用金属蒸发真空多弧离子源注入机，将Au离子注入到高纯石英玻璃来制备镶嵌有Au 纳米颗粒的衬底材料，随后将化学方法合成的CdTe量子点旋涂在玻璃衬底上制备了Au纳米颗粒和CdTe量子点复合体系。通过对镶嵌有Au纳米颗粒的衬底进行热退火处理来控制Au纳米颗粒的生长和分布，系统研究了Au纳米颗粒的局域表面等离子体共振对CdTe量子点光致发光性能的影响。利用光学吸收谱、原子力显微镜、透射电子显微镜和光致发光谱对样品进行了表征和测试。光致发光谱表明， Au纳米颗粒的局域表面等离子体对CdTe量子点的发光有增强效应也有猝灭效应。深入分析了Au纳米颗粒和CdTe量子点之间的相互作用过程，提出了关于Au-CdTe 纳米复合体系中CdTe 发光增强和猝灭的新机理。该实验结果为利用金属纳米颗粒表面等离子体技术制备高发光性能的光电子器件提供了较好的参考。%New composite systems consisting of Au nanoparticles (NPs) and CdTe quantum dots (QDs) are fabricated by spin coating chemically synthesizing CdTe QDs on silica substrates which have already been implanted by Ag ions through using a metal vapor vacuum arc (MEVVA) ion source implanter. By thermally annealing the Au ions implanted silica substrates, the growth and redistribution of Au NPs can be controlled, the influence of localized surface plasmon (LSP) of Au NPs on the photoluminescence (PL) of CdTe QDs is well studied. The optical properties, surface morphologies, microstructures, and light emission properties of the Au-ion implanted samples are investigated by using optical ab-sorption spectroscopy, atomic force microscopy, transmission electron microscopy and PL spectra measurements. PL spectra show that the PL intensities from Au NPs and CdTe QDs composite systems can be enhanced or quenched compared with those of CdTe QDs directly spin coated on bare silica
Quantum Effects in Biological Systems
2016-01-01
Since the last decade the study of quantum mechanical phenomena in biological systems has become a vibrant field of research. Initially sparked by evidence of quantum effects in energy transport that is instrumental for photosynthesis, quantum biology asks the question of how methods and models from quantum theory can help us to understand fundamental mechanisms in living organisms. This approach entails a paradigm change challenging the related disciplines: The successful framework of quantum theory is taken out of its low-temperature, microscopic regimes and applied to hot and dense macroscopic environments, thereby extending the toolbox of biology and biochemistry at the same time. The Quantum Effects in Biological Systems conference is a platform for researchers from biology, chemistry and physics to present and discuss the latest developments in the field of quantum biology. After meetings in Lisbon (2009), Harvard (2010), Ulm (2011), Berkeley (2012), Vienna (2013), Singapore (2014) and Florence (2015),...
Dorfner, F.; Heidrich-Meisner, F.
2016-06-01
We study properties of the single-site reduced density matrix in the Bose-Bose resonance model as a function of system parameters. This model describes a single-component Bose gas with a resonant coupling to a diatomic molecular state, here defined on a lattice. A main goal is to demonstrate that the eigenstates of the single-site reduced density matrix have structures that are characteristic for the various quantum phases of this system. Since the Hamiltonian conserves only the global particle number but not the number of bosons and molecules individually, these eigenstates, referred to as optimal modes, can be nontrivial linear combinations of bare eigenstates of the molecular and boson particle number. We numerically analyze the optimal modes and their weights, the latter giving the importance of the corresponding state, in the ground state of the Bose-Bose resonance model. We find that the single-site von Neumann entropy is sensitive to the location of the phase boundaries. We explain the structure of the optimal modes and their weight spectra using perturbation theory and via a comparison to results for the single-component Bose-Hubbard model. We further study the dynamical evolution of the optimal modes and of the single-site entanglement entropy in two quantum quenches that cross phase boundaries of the model and show that these quantities are thermal in the steady state. For our numerical calculations, we use the density-matrix renormalization group method for ground-state calculations and time evolution in a Krylov subspace for the quench dynamics as well as exact diagonalization.
Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan
2016-11-15
Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development.
Quantum walks public key cryptographic system
Vlachou, C; Rodrigues, J.; Mateus, P.; Paunković, N.; Souto, A.
2016-01-01
Quantum Cryptography is a rapidly developing field of research that benefits from the properties of Quantum Mechanics in performing cryptographic tasks. Quantum walks are a powerful model for quantum computation and very promising for quantum information processing. In this paper, we present a quantum public-key cryptographic system based on quantum walks. In particular, in the proposed protocol the public key is given by a quantum state generated by performing a quantum walk. We show that th...
Zhou, Jing; Han, Tongqian; Ma, Hongmin; Yan, Tao; Pang, Xuehui; Li, Yueyun; Wei, Qin
2015-08-19
Nitrogen-doped carbon quantum dots (N-CQDs) with an average diameter of 2 nm were synthesized by carbonization of diethylene triamine pentacetate acid (DTPA). The simple prepared N-CQDs showed excellent electrochemiluminescence (ECL) property and were used as luminophors to fabricate a sandwich-type ECL immunosensor. Aminated graphene (NH2-G) was also synthesized and used as a label of secondary antibody. The labeled NH2-G could effectively quench the ECL of N-CQDs modified on electrodes due to ECL resonance energy transfer (ERET). Immunological recognition which induced ECL quenching enabled the quantitative determination of biomarkers. Alpha fetoprotein (AFP) was selected as a model analyte to investigate the analytical performance of the proposed immunosensor. Under optimal conditions, a good linear relationship between ECL intensity and the logarithm of AFP concentration was obtained in the range of 0.01-100 ng mL(-1) with the detection limit of 3.3 pg mL(-1). The proposed ECL immunosensor showed good stability, acceptable selectivity and reproducibility. Copyright © 2015 Elsevier B.V. All rights reserved.
Molina-García, L; Llorent-Martínez, E J; Fernández-de Córdova, M L; Santos, J L M; Rodrigues, S S M; Ruiz-Medina, A
2013-06-01
The field of light-emitting nanoparticles has experienced an enormous development over the past two decades. The fluorescence of these nanometer-size crystalline particles, called quantum dots (QDs), can be both quenched and enhanced by different compounds. Since a high percentage of articles related to QDs are focused on theoretical studies, the development of analytical methods with real applications is an important step in order to progressively demonstrate the versatility of these particles. Moreover, taking into account that most of the QDs-based analytical methods are non-automated, the development of automated flow methodologies is still a field that presents an important analytical potential. With this purpose, two automatic methodologies, multicommutated flow injection analysis and sequential injection analysis, have been here applied to the analysis of quinolones in pharmaceutical formulations, making use of the quenching effect caused by the analytes over mercaptopropionic acid-capped CdTe QDs fluorescence. Both methodologies were compared in terms of versatility, sample throughput, sensitivity, etc., and applied to the determination of five quinolones in pharmaceutical preparations available in the Spanish Pharmacopoeia. The detection limits ranged between 26 and 50μmolL(-1), and Relative Standard Deviations lower than 3% were observed in all cases.
Iqbal, A.; Toor, A. H.
2002-03-01
We investigate the role of quantum mechanical effects in the central stability concept of evolutionary game theory, i.e., an evolutionarily stable strategy (ESS). Using two and three-player symmetric quantum games we show how the presence of quantum phenomenon of entanglement can be crucial to decide the course of evolutionary dynamics in a population of interacting individuals.
Quench Protection System Optimization for the High Luminosity LHC Nb $_3$Sn Quadrupoles
Ravaioli, E; Auchmann, B; Ferracin, P; Maciejewski, M; Rodriguez-Mateos, F; Sabbi, GL; Todesco, E; Verweij, A P
2017-01-01
The upgrade of the large hadron collider to achieve higher luminosity requires the installation of twenty-four 150 mm aperture, 12 T, $Nb_3Sn$ quadrupole magnets close to the two interaction regions at ATLAS and CMS. The protection of these high-field magnets after a quench is particularly challenging due to the high stored energy density, which calls for a fast, effective, and reliable protection system. Three design options for the quench protection system of the inner triplet circuit are analyzed, including quench heaters attached to the coil's outer and inner layer, Coupling-Loss Induced Quench (CLIQ), and combinations of those. The discharge of the magnet circuit and the electromagnetic and thermal transients occurring in the coils are simulated by means of the TALES and LEDET programs. The sensitivity to strand parameters and the effects of several failure cases on the coil's hot-spot temperature and peak voltages to ground are assessed. A protection system based only on quench heaters attached to the o...
Institute of Scientific and Technical Information of China (English)
应和平; 董绍静; 张剑波
2003-01-01
With an exact chiral symmetry, overlap fermions allow us to reach very light quark region. In the minimummps = 179 MeV, the quenched chiral logarithm diverge is examined. The chiral logarithm parameter δ is calculatedfrom both the pseudo-scalar meson mass mp2s diverge channel and the pseudo-scalar decay constant f p channel.In both the cases, we obtain δ = 0.25 ± 0.03. We also observe that the quenchedchiral logarithm diverge occursonly in the mps ≤400 MeV region.
Feedback control of quantum system
Institute of Scientific and Technical Information of China (English)
DONG Dao-yi; CHEN Zong-hai; ZHANG Chen-bin; CHEN Chun-lin
2006-01-01
Feedback is a significant strategy for the control of quantum system.Information acquisition is the greatest difficulty in quantum feedback applications.After discussing several basic methods for information acquisition,we review three kinds of quantum feedback control strategies:quantum feedback control with measurement,coherent quantum feedback,and quantum feedback control based on cloning and recognition.The first feedback strategy can effectively acquire information,but it destroys the coherence in feedback loop.On the contrary,coherent quantum feedback does not destroy the coherence,but the capability of information acquisition is limited.However,the third feedback scheme gives a compromise between information acquisition and measurement disturbance.
Quantum point contacts in quantum wire systems
Energy Technology Data Exchange (ETDEWEB)
Sternemann, E.; Buchholz, S.S.; Fischer, S.F.; Kunze, U. [Werkstoffe und Nanoelektronik, Ruhr-Universitaet Bochum (Germany); Reuter, D.; Wieck, A.D. [Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum (Germany)
2010-07-01
Quantum point contacts (QPCs) attract high interest for applications as magnetic focussing, beam splitting (quantum Hall edge states), spin filtering and electron thermometry. Here, we investigate QPCs in complex quantum wire (QWR) systems such as quantum rings. The QPCs were realized by lithographical definition of a short (150 nm) constriction (170 nm width) in (a) a 540 nm wide QWR and (b) 520 nm wide QWR leads of a QWR ring as in. Nanogates on top of the constrictions allow for the control of occupied modes in the QPCs. The devices are based on a GaAs/AlGaAs heterostructure with a 2DEG 55 nm below the surface, patterned by electron beam lithography and wet-chemical etching. Two- and four-terminal conductance measurements at temperatures between 23 mK and 4.2 K were performed using lock-in technique. Our measurements reveal that QPCs in 1D nanostructures can be prepared to show subband separations of 6 meV, clear conductance quantization as well as the 0.7 anomaly. We further show that electron injection across a QPC into a QWR ring allows for electron interference (Aharonov-Bohm effect).
Quantum Effects in Biological Systems
Roy, Sisir
2014-07-01
The debates about the trivial and non-trivial effects in biological systems have drawn much attention during the last decade or so. What might these non-trivial sorts of quantum effects be? There is no consensus so far among the physicists and biologists regarding the meaning of "non-trivial quantum effects". However, there is no doubt about the implications of the challenging research into quantum effects relevant to biology such as coherent excitations of biomolecules and photosynthesis, quantum tunneling of protons, van der Waals forces, ultrafast dynamics through conical intersections, and phonon-assisted electron tunneling as the basis for our sense of smell, environment assisted transport of ions and entanglement in ion channels, role of quantum vacuum in consciousness. Several authors have discussed the non-trivial quantum effects and classified them into four broad categories: (a) Quantum life principle; (b) Quantum computing in the brain; (c) Quantum computing in genetics; and (d) Quantum consciousness. First, I will review the above developments. I will then discuss in detail the ion transport in the ion channel and the relevance of quantum theory in brain function. The ion transport in the ion channel plays a key role in information processing by the brain.
Decoherence in quantum spin systems
De Raedt, H; Dobrovitski, VV; Landau, DP; Lewis, SP; Schuttler, HB
2003-01-01
Computer simulations of decoherence in quantum spin systems require the solution of the time-dependent Schrodinger equation for interacting quantum spin systems over extended periods of time. We use exact diagonalization, the Chebyshev polynomial technique, four Suzuki-formula algorithms, and the sh
CLIQ – Coupling-Loss Induced Quench System for Protecting Superconducting Magnets
Ravaioli, E; Kirby, G; ten Kate, H H J; Verweij, A P
2014-01-01
The recently developed Coupling-Loss-Induced Quench (CLIQ) protection system is a new method for initiating a fast and voluminous transition to the normal state for protecting high energy density superconducting magnets. Upon quench detection, CLIQ is triggered to generate an oscillating current in the magnet coil by means of a capacitive discharge. This in turn introduces a high coupling loss in the superconductor which provokes a quick transition to the normal state of the coil windings. The system is now implemented for the protection of a two meter long superconducting quadrupole magnet and characterized in the CERN magnet test facility. Various CLIQ configurations with different current injection points are tested and the results compared to similar transients lately measured with a not optimized configuration. Test results convincingly show that the newly tested design allows for a more global quench initiation and thus a faster discharge of the magnet energy. Moreover, the performance of CLIQ for reduc...
Güven, Can; Hinczewski, Michael; Berker, A. Nihat
2011-03-01
The tensor renormalization-group method, developed by Levin and Nave, brings systematic improvability to the position-space renormalization-group method and yields essentially exact results for phase diagrams and entire thermodynamic functions. The method, previously used on systems with no quenched randomness, is extended in this study to systems with quenched randomness. Local magnetizations and correlation functions as a function of spin separation are calculated as tensor products subject to renormalization-group transformation. Phase diagrams are extracted from the long-distance behavior of the correlation functions. The approach is illustrated with the quenched bond-diluted Ising model on the triangular lattice. An accurate phase diagram is obtained in temperature and bond-dilution probability for the entire temperature range down to the percolation threshold at zero temperature. This research was supported by the Alexander von Humboldt Foundation, the Scientific and Technological Research Council of Turkey (TÜBITAK), and the Academy of Sciences of Turkey.
Temperature Intelligent Control System of Large-Scale Standing Quench Furnace
Institute of Scientific and Technical Information of China (English)
HE Jian-jun; YU Shou-yi
2005-01-01
Considering some characteristics of large-scale standing quench furnace, such as greatheat inertia, evident time lag, strong coupling influence, hard to establish exact mathematical models of plant and etc, an artificial intelligent fuzzy control algorithm is put forward in this paper Through adjusting the on-off ratio of electric heating elements, the temperature in furnace is controlled accurately. This paper describes structure and qualities of the large-scale standing quench furnace briefly, introduces constitution of control system, and expounds principle and implementation of intelligent control algorithm. The applied results prove that the intelligent control system can completely satisfy the technological requirements. Namely, it can realize fast increasing temperature with a little overshoot, exact holding temperature, and well-distributed temperature in quench furnace. It has raised the output and quality of aluminum material, and brought the outstanding economic and social benefits.
Güven, Can; Hinczewski, Michael; Berker, A Nihat
2010-11-01
The tensor renormalization-group method, developed by Levin and Nave, brings systematic improvability to the position-space renormalization-group method and yields essentially exact results for phase diagrams and entire thermodynamic functions. The method, previously used on systems with no quenched randomness, is extended in this study to systems with quenched randomness. Local magnetizations and correlation functions as a function of spin separation are calculated as tensor products subject to renormalization-group transformation. Phase diagrams are extracted from the long-distance behavior of the correlation functions. The approach is illustrated with the quenched bond-diluted Ising model on the triangular lattice. An accurate phase diagram is obtained in temperature and bond-dilution probability for the entire temperature range down to the percolation threshold at zero temperature.
Bahder, T B
2004-01-01
A quantum positioning system (QPS) is proposed that can provide a user with all four of his space-time coordinates. The user must carry a corner cube reflector, a good clock, and have a two-way classical channel of communication with the origin of the reference frame. Four pairs of entangled photons (biphotons) are sent through four interferometers: three interferometers are used to determine the user's spatial position, and an additional interferometer is used to synchronize the user's clock to coordinate time in the reference frame. The spatial positioning part of the QPS is similar to a classical time-of-arrival (TOA) system, however, a classical TOA system (such as GPS) must have synchronized clocks that keep coordinate time and therefore the clocks must have long-term stability, whereas in the QPS only a photon coincidence counter is needed and the clocks need only have short-term stability. Several scenarios are considered for a QPS: one is a terrestrial system and another is a space-based-system compos...
Quantum technologies with hybrid systems.
Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg
2015-03-31
An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.
Quantum technologies with hybrid systems
Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg
2015-01-01
An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field. PMID:25737558
Propagation of Disturbances in Degenerate Quantum Systems
Chancellor, Nicholas
2011-01-01
Disturbances in gapless quantum many-body models are known to travel an unlimited distance throughout the system. Here, we explore this phenomenon in finite clusters with degenerate ground states. The specific model studied here is the one-dimensional J1-J2 Heisenberg Hamiltonian at and close to the Majumdar-Ghosh point. Both open and periodic boundary conditions are considered. Quenches are performed using a local magnetic field. The degenerate Majumdar-Ghosh ground state allows disturbances which carry quantum entanglement to propagate throughout the system, and thus dephase the entire system within the degenerate subspace. These disturbances can also carry polarization, but not energy, as all energy is stored locally. The local evolution of the part of the system where energy is stored drives the rest of the system through long-range entanglement. We also examine approximations for the ground state of this Hamiltonian in the strong field limit, and study how couplings away from the Majumdar-Ghosh point aff...
Energy Technology Data Exchange (ETDEWEB)
Barmettler, Peter; Gritsev, Vladimir [Department of Physics, University of Fribourg, CH-1700 Fribourg (Switzerland); Punk, Matthias [CPHT, Ecole Polytechnique, 91128 Palaiseau (France); Demler, Eugene [Department of Physics, Harvard University, Cambridge, MA 02138 (United States); Altman, Ehud, E-mail: peter.barmettler@cpht.polytechnique.f [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)
2010-05-15
Recent experimental achievements in controlling ultracold gases in optical lattices open a new perspective on quantum many-body physics. In these experimental setups, it is possible to study coherent time evolution of isolated quantum systems. These dynamics reveal new physics beyond the low-energy properties that are usually relevant in solid-state many-body systems. In this paper, we study the time evolution of antiferromagnetic order in the Heisenberg chain after a sudden change of the anisotropy parameter, using various numerical and analytical methods. As a generic result, we find that the order parameter, which can show oscillatory or non-oscillatory dynamics, decays exponentially except for the effectively non-interacting case of the XX limit. For weakly ordered initial states, we also find evidence for an algebraic correction to the exponential law. The study is based on numerical simulations using a numerical matrix product method for infinite system sizes (iMPS), for which we provide a detailed description and an error analysis. Additionally, we investigate in detail the exactly solvable XX limit. These results are compared to approximative analytical approaches including an effective description by the XZ model as well as by mean-field, Luttinger-liquid and sine-Gordon theories. The comparison reveals which aspects of non-equilibrium dynamics can, as in equilibrium, be described by low-energy theories and which are the novel phenomena specific to quantum quench dynamics. The relevance of the energetically high part of the spectrum is illustrated by means of a full numerical diagonalization of the Hamiltonian.
Noncommutative mathematics for quantum systems
Franz, Uwe
2016-01-01
Noncommutative mathematics is a significant new trend of mathematics. Initially motivated by the development of quantum physics, the idea of 'making theory noncommutative' has been extended to many areas of pure and applied mathematics. This book is divided into two parts. The first part provides an introduction to quantum probability, focusing on the notion of independence in quantum probability and on the theory of quantum stochastic processes with independent and stationary increments. The second part provides an introduction to quantum dynamical systems, discussing analogies with fundamental problems studied in classical dynamics. The desire to build an extension of the classical theory provides new, original ways to understand well-known 'commutative' results. On the other hand the richness of the quantum mathematical world presents completely novel phenomena, never encountered in the classical setting. This book will be useful to students and researchers in noncommutative probability, mathematical physi...
Decoherence in infinite quantum systems
Energy Technology Data Exchange (ETDEWEB)
Blanchard, Philippe; Hellmich, Mario [Faculty of Physics, University of Bielefeld, Universitaetsstr. 25, 33615 Bielefeld (Germany); Bundesamt fuer Strahlenschutz (Federal Office for Radiation Protection), Willy-Brandt-Strasse 5, 38226 Salzgitter (Germany)
2012-09-01
We review and discuss a notion of decoherence formulated in the algebraic framework of quantum physics. Besides presenting some sufficient conditions for the appearance of decoherence in the case of Markovian time evolutions we provide an overview over possible decoherence scenarios. The framework for decoherence we establish is sufficiently general to accommodate quantum systems with infinitely many degrees of freedom.
Relaxation of antiferromagnetic order in spin-1/2 chains following a quantum quench.
Barmettler, Peter; Punk, Matthias; Gritsev, Vladimir; Demler, Eugene; Altman, Ehud
2009-04-03
We study the unitary time evolution of antiferromagnetic order in anisotropic Heisenberg chains that are initially prepared in a pure quantum state far from equilibrium. Our analysis indicates that the antiferromagnetic order imprinted in the initial state vanishes exponentially. Depending on the anisotropy parameter, oscillatory or nonoscillatory relaxation dynamics is observed. Furthermore, the corresponding relaxation time exhibits a minimum at the critical point, in contrast to the usual notion of critical slowing down, from which a maximum is expected.
An FPGA-based quench detection and protection system for superconducting accelerator magnets
Energy Technology Data Exchange (ETDEWEB)
Carcagno, R.H.; Feher, S.; Lamm, M.; Makulski, A.; Nehring, R.; Orris, D.F.; Pischalnikov, Y.; Tartaglia, M.; /Fermilab
2005-05-01
A new quench detection and protection system for superconducting accelerator magnets was developed for the Fermilab's Magnet Test Facility (MTF). This system is based on a Field-Programmable Gate Array (FPGA) module, and it is made of mostly commercially available, integrated hardware and software components. It provides all the functions of our existing VME-based quench detection and protection system, but in addition the new system is easily scalable to protect multiple magnets powered independently and a more powerful user interface and analysis tools. The new system has been used successfully for testing LHC Interaction Region Quadrupoles correctors and High Field Magnet HFDM04. In this paper we describe the system and present results.
Quantum dissipation in unbounded systems.
Maddox, Jeremy B; Bittner, Eric R
2002-02-01
In recent years trajectory based methodologies have become increasingly popular for evaluating the time evolution of quantum systems. A revival of the de Broglie--Bohm interpretation of quantum mechanics has spawned several such techniques for examining quantum dynamics from a hydrodynamic perspective. Using techniques similar to those found in computational fluid dynamics one can construct the wave function of a quantum system at any time from the trajectories of a discrete ensemble of hydrodynamic fluid elements (Bohm particles) which evolve according to nonclassical equations of motion. Until very recently these schemes have been limited to conservative systems. In this paper, we present our methodology for including the effects of a thermal environment into the hydrodynamic formulation of quantum dynamics. We derive hydrodynamic equations of motion from the Caldeira-Leggett master equation for the reduced density matrix and give a brief overview of our computational scheme that incorporates an adaptive Lagrangian mesh. Our applications focus upon the dissipative dynamics of open unbounded quantum systems. Using both the Wigner phase space representation and the linear entropy, we probe the breakdown of the Markov approximation of the bath dynamics at low temperatures. We suggest a criteria for rationalizing the validity of the Markov approximation in open unbound systems and discuss decoherence, energy relaxation, and quantum/classical correspondence in the context of the Bohmian paths.
New, Coupling Loss Induced, Quench Protection System for Superconducting Accelerator Magnets
Ravaioli, E; Giloux, C; Kirby, G; ten Kate, H H J; Verweij, A P
2014-01-01
Email Print Request Permissions Save to Project A new and promising method for the protection of superconducting high-field magnets is developed and tested on the so-called MQXC quadrupole magnet at the CERN magnet test facility. The method relies on a capacitive discharge system inducing, during a few periods, an oscillation of the transport current in the superconducting cable of the coil. The corresponding fast change of the local magnetic field introduces a high coupling-current loss, which, in turn, causes a fast quench of a large fraction of the coil due to enhanced temperature. Results of measured discharges at various levels of transport current are presented and compared to discharges by quenching the coils using conventional quench heaters and an energy extraction system. The hot-spot temperature in the quenching coil is deduced from the coil voltage and current. The results are compared to simulations carried out using a lumped-element dynamic electro-thermal model of the so-called MQX...
Design and implementation of quench detection instrumentation for TF magnet system of SST-1
Energy Technology Data Exchange (ETDEWEB)
Khristi, Y.; Sharma, A.N.; Doshi, K.; Banaudha, M.; Prasad, U.; Varmora, P.; Patel, D.; Pradhan, S., E-mail: subrata.s.pradhan@gmail.com
2014-05-15
Steady State Superconducting Tokamak-1 (SST-1) at Institute for Plasma Research (IPR), India is now in engineering validation phase. The assembled Toroidal Field (TF) magnet system of SST-1 will be operated at 10 kA of nominal current at helium cooled condition of 4.5 K. A reliable and fail proof quench detection (QD) system is essential for the safety and the investment protection requirements of the magnets. This QD system needs to continuously monitor all the superconducting coils, which include 16 TF magnets, return-loop, bus bars and current leads. In case of any event initiating the normal resistive zone and reaching thermal run-away, the QD system needs to trigger the magnet protection circuits. Precision instrumentation and control system with 204 signal channels had been developed for detection of quench anywhere in the entire TF magnet system. In the present configuration of quench detection scheme, the voltage drop across each double pancake (DP) of each TF coil are compared with its two adjacent DPs for the detection of normal zone and cancelation of inductive couples. Two identical redundant systems with one out of two configurations are successfully commissioned and tested at IPR. This paper describes the design and implementation of the QD system, Installation experience, validation test and initial results from the recent SST-1 magnet system charging.
Institute of Scientific and Technical Information of China (English)
XIA Yun-Sheng; CAO Chun; ZHU Chang-Qing
2007-01-01
Three different size CdTe quantum dots (QDs) capped by 3-mercaptopropionic acid (MPA) have been prepared in aqueous solutions,and their interactions with Cu2+ and Hg2+ have been investigated.The opposite size-dependent fluorescence quenching of CdTe QDs by Hg2+ and Cu2+ was observed: Hg2+ quenched smaller particles more efficiently than larger ones while larger particles were more markedly quenched by Cu2+.Based on the different size responses,Hg2+ and Cu2+ were respectively detected with high sensitivity and selectivity,for the first time,using the QDs with different sizes but the same components and capping ligands.
Quenching of the quantum Hall effect in graphene with scrolled edges.
Cresti, Alessandro; Fogler, Michael M; Guinea, Francisco; Castro Neto, A H; Roche, Stephan
2012-04-20
Edge nanoscrolls are shown to strongly influence transport properties of suspended graphene in the quantum Hall regime. The relatively long arclength of the scrolls in combination with their compact transverse size results in formation of many nonchiral transport channels in the scrolls. They short circuit the bulk current paths and inhibit the observation of the quantized two-terminal resistance. Unlike competing theoretical proposals, this mechanism of disrupting the Hall quantization in suspended graphene is not caused by ill-chosen placement of the contacts, singular elastic strains, or a small sample size.
Preconditioned quantum linear system algorithm.
Clader, B D; Jacobs, B C; Sprouse, C R
2013-06-21
We describe a quantum algorithm that generalizes the quantum linear system algorithm [Harrow et al., Phys. Rev. Lett. 103, 150502 (2009)] to arbitrary problem specifications. We develop a state preparation routine that can initialize generic states, show how simple ancilla measurements can be used to calculate many quantities of interest, and integrate a quantum-compatible preconditioner that greatly expands the number of problems that can achieve exponential speedup over classical linear systems solvers. To demonstrate the algorithm's applicability, we show how it can be used to compute the electromagnetic scattering cross section of an arbitrary target exponentially faster than the best classical algorithm.
Screening in quantum charged systems
Martin, Ph. A.; Gruber, Ch.
1984-07-01
For stationary states of quantum charged systems in ν dimensions, ν>=2, it is proven that the reduced-density matrices satisfy a set of sum rules whenever the clustering is faster than |x|-(ν+l). These sum rules, describing the screening properties, are analogous to those previously derived for classical systems. For neutral quantum fluids, it is shown that the clustering cannot be faster than the decay of the force.
Quantum contextuality in complex systems
Cabello, Adan
2010-01-01
We show that, for a system of several qubits, there is an inequality for the correlations between three compatible dichotomic measurements which must be satisfied by any noncontextual theory, but is violated by any quantum state. Remarkably, the violation grows exponentially with the number of qubits, and the tolerated error per correlation also increases with the number of qubits, showing that state-independent quantum contextuality is experimentally observable in complex systems.
Universal blind quantum computation for hybrid system
Huang, He-Liang; Bao, Wan-Su; Li, Tan; Li, Feng-Guang; Fu, Xiang-Qun; Zhang, Shuo; Zhang, Hai-Long; Wang, Xiang
2017-08-01
As progress on the development of building quantum computer continues to advance, first-generation practical quantum computers will be available for ordinary users in the cloud style similar to IBM's Quantum Experience nowadays. Clients can remotely access the quantum servers using some simple devices. In such a situation, it is of prime importance to keep the security of the client's information. Blind quantum computation protocols enable a client with limited quantum technology to delegate her quantum computation to a quantum server without leaking any privacy. To date, blind quantum computation has been considered only for an individual quantum system. However, practical universal quantum computer is likely to be a hybrid system. Here, we take the first step to construct a framework of blind quantum computation for the hybrid system, which provides a more feasible way for scalable blind quantum computation.
Spin diffusion from an inhomogeneous quench in an integrable system
Ljubotina, Marko; Žnidarič, Marko; Prosen, Tomaž
2017-07-01
Generalized hydrodynamics predicts universal ballistic transport in integrable lattice systems when prepared in generic inhomogeneous initial states. However, the ballistic contribution to transport can vanish in systems with additional discrete symmetries. Here we perform large scale numerical simulations of spin dynamics in the anisotropic Heisenberg XXZ spin 1/2 chain starting from an inhomogeneous mixed initial state which is symmetric with respect to a combination of spin reversal and spatial reflection. In the isotropic and easy-axis regimes we find non-ballistic spin transport which we analyse in detail in terms of scaling exponents of the transported magnetization and scaling profiles of the spin density. While in the easy-axis regime we find accurate evidence of normal diffusion, the spin transport in the isotropic case is clearly super-diffusive, with the scaling exponent very close to 2/3, but with universal scaling dynamics which obeys the diffusion equation in nonlinearly scaled time.
An Efficient Fluid-Dynamic Analysis to Improve Industrial Quenching Systems
Directory of Open Access Journals (Sweden)
Manuel de J. Barrena-Rodríguez
2017-05-01
Full Text Available This paper addresses the problem of understanding the relationship between fluid flow and heat transfer in industrial quenching systems. It also presents an efficient analysis to design or optimize long standing quenching tanks to increase productivity. The study case is automotive leaf springs quenched in an oil-tank agitated with submerged jets. This analysis combined an efficient numerical prediction of the detailed isothermal flow field in the whole tank with the thermal characterization of steel probes in plant and laboratory during quenching. These measurements were used to determine the heat flow by solving the inverse heat conduction problem. Differences between laboratory and plant heat flux results were attributed to the difference in surface area size between samples. A proposed correlation between isothermal wall shear stress and heat flux at the surface of the steel component, based on the Reynolds-Colburn analogy, provided the connection between thermal characterization and computed isothermal fluid flow. The present approach allowed the identification of the potential benefits of changes in the tank design and the evaluation of operating conditions while using a much shorter computing time and storage memory than full-domain fluid flow calculations.
Song, Nianhui; Zhu, Haiming; Liu, Zheng; Huang, Zhuangqun; Wu, David; Lian, Tianquan
2013-02-26
Integrating quantum dots (QDs) into modern optoelectronic devices requires an understanding of how a transparent conducting substrate affects the properties of QDs, especially their excited-state dynamics. Here, the exciton quenching dynamics of core/multishell (CdSe/CdS(3ML)ZnCdS(2ML)ZnS(2ML)) quantum dots deposited on glass, tin oxide (SnO₂), and antimony (Sb)-doped tin oxide (ATO) films are studied by transient absorption and single QD fluorescence spectroscopic methods. By comparing ensemble-averaged fluorescence decay and transient absorption kinetics, we show that, for QDs on SnO₂, the exciton is quenched by electron transfer from the QD to SnO₂. At the QD-ATO interface, much faster exciton quenching rates are observed and attributed to fast Auger recombination in charged QDs formed by Fermi level equilibration between the QD and n-doped ATO. Single QDs on SnO₂ and ATO show similar blinking dynamics with correlated fluctuations of emission intensities and lifetimes. Compared to QDs on SnO₂, QDs on ATO films show larger variation of average exciton quenching rates, which is attributed to a broad distribution of the number of charges and nature of charging sites on the QD surface.
Quantum Dot Systems: a versatile platform for quantum simulations
Barthelemy, P.J.C.; Vandersypen, L.M.K.
2013-01-01
Quantum mechanics often results in extremely complex phenomena, especially when the quantum system under consideration is composed of many interacting particles. The states of these many-body systems live in a space so large that classical numerical calculations cannot compute them. Quantum simulati
Quantum Dot Systems: a versatile platform for quantum simulations
Barthelemy, P.J.C.; Vandersypen, L.M.K.
2013-01-01
Quantum mechanics often results in extremely complex phenomena, especially when the quantum system under consideration is composed of many interacting particles. The states of these many-body systems live in a space so large that classical numerical calculations cannot compute them. Quantum
Shen, Yizhong; Liu, Shaopu; He, Youqiu
2014-03-01
Water-soluble glutathione (GSH)-capped core/shell CdTe/CdS quantum dots (QDs) were synthesized. In pH5.4 sodium phosphate buffer medium, the interaction between GSH-CdTe/CdS QDs and sanguinarine (SA) was investigated by spectroscopic methods, including fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy. Addition of SA to GSH-CdTe/CdS QDs results in fluorescence quenching of GSH-CdTe/CdS QDs. Quenching intensity was in proportion to the concentration of SA in a certain range. Investigation of the quenching mechanism, proved that the fluorescence quenching of GSH-CdTe/CdS QDs by SA is a result of electron transfer. Based on the quenching of the fluorescence of GSH-CdTe/CdS QDs by SA, a novel, simple, rapid and specific method for SA determination was proposed. The detection limit for SA was 3.4 ng/mL and the quantitative determination range was 0.2-40.0 µg/mL with a correlation coefficient of 0.9988. The method has been applied to the determination of SA in synthetic samples and fresh urine samples of healthy human with satisfactory results.
Introduction to quantum spin systems
Directory of Open Access Journals (Sweden)
A. Langari
2008-06-01
Full Text Available This manuscript is the collection of lectures given in the summer school on strongly correlated electron systems held at Isfahan university of technology, June 2007. A short overview on quantum magnetism and spin systems is presented. The numerical exact diagonalization (Lanczos alghorithm is explained in a pedagogical ground. This is a method to get some ground state properties on finite cluster of lattice models. Two extensions of Lanczos method to get the excited states and also finite temperature properties of quantum models are also explained. The basic notions of quantum phase transition is discussed in term of Ising model in transverse field. Its phase diagram and critical properties are explained using the quantum renormalization group approach. Most of the topics are in tutorial level with hints to recent research activities.
Chemla, D. S.; Bar-Joseph, I.; Klingshirn, C.; Miller, D. A. B.; Kuo, J. M.
1987-03-01
Absorption switching in a semiconductor quantum well by electrically varying the charge density in the quantum well conducting channel of a selectively doped heterostructure transistor is reported for the first time. The phase-space absorption quenching (PAQ) is observed at room temperature in an InGaAs/InAlAs grown on InP FET, and it shows large absorption coefficient changes with relatively broad spectral bandwidth. This PAQ is large enough to be used for direct optical determination of the logic state of the FET.
Nussinov, Zohar; Johnson, Patrick; Graf, Matthias J.; Balatsky, Alexander V.
2013-05-01
length scales that increase far more slowly than the relaxation time as a putative critical transition is approached. Similar results may hold for spin-liquid-type as well as interacting electronic systems. We suggest ways to analyze experimental data in order to adduce such phenomena. Our approach may be used to analyze other quenched quantum systems.
Quantum walk public-key cryptographic system
Vlachou, C.; Rodrigues, J.; Mateus, P.; Paunković, N.; Souto, A.
2015-12-01
Quantum Cryptography is a rapidly developing field of research that benefits from the properties of Quantum Mechanics in performing cryptographic tasks. Quantum walks are a powerful model for quantum computation and very promising for quantum information processing. In this paper, we present a quantum public-key cryptographic system based on quantum walks. In particular, in the proposed protocol the public-key is given by a quantum state generated by performing a quantum walk. We show that the protocol is secure and analyze the complexity of public key generation and encryption/decryption procedures.
Duality quantum algorithm efficiently simulates open quantum systems.
Wei, Shi-Jie; Ruan, Dong; Long, Gui-Lu
2016-07-28
Because of inevitable coupling with the environment, nearly all practical quantum systems are open system, where the evolution is not necessarily unitary. In this paper, we propose a duality quantum algorithm for simulating Hamiltonian evolution of an open quantum system. In contrast to unitary evolution in a usual quantum computer, the evolution operator in a duality quantum computer is a linear combination of unitary operators. In this duality quantum algorithm, the time evolution of the open quantum system is realized by using Kraus operators which is naturally implemented in duality quantum computer. This duality quantum algorithm has two distinct advantages compared to existing quantum simulation algorithms with unitary evolution operations. Firstly, the query complexity of the algorithm is O(d(3)) in contrast to O(d(4)) in existing unitary simulation algorithm, where d is the dimension of the open quantum system. Secondly, By using a truncated Taylor series of the evolution operators, this duality quantum algorithm provides an exponential improvement in precision compared with previous unitary simulation algorithm.
Duality quantum algorithm efficiently simulates open quantum systems
Wei, Shi-Jie; Ruan, Dong; Long, Gui-Lu
2016-07-01
Because of inevitable coupling with the environment, nearly all practical quantum systems are open system, where the evolution is not necessarily unitary. In this paper, we propose a duality quantum algorithm for simulating Hamiltonian evolution of an open quantum system. In contrast to unitary evolution in a usual quantum computer, the evolution operator in a duality quantum computer is a linear combination of unitary operators. In this duality quantum algorithm, the time evolution of the open quantum system is realized by using Kraus operators which is naturally implemented in duality quantum computer. This duality quantum algorithm has two distinct advantages compared to existing quantum simulation algorithms with unitary evolution operations. Firstly, the query complexity of the algorithm is O(d3) in contrast to O(d4) in existing unitary simulation algorithm, where d is the dimension of the open quantum system. Secondly, By using a truncated Taylor series of the evolution operators, this duality quantum algorithm provides an exponential improvement in precision compared with previous unitary simulation algorithm.
Eigenstate Gibbs ensemble in integrable quantum systems
Nandy, Sourav; Sen, Arnab; Das, Arnab; Dhar, Abhishek
2016-12-01
The eigenstate thermalization hypothesis conjectures that for a thermodynamically large system in one of its energy eigenstates, the reduced density matrix describing any finite subsystem is determined solely by a set of relevant conserved quantities. In a chaotic quantum system, only the energy is expected to play that role and hence eigenstates appear locally thermal. Integrable systems, on the other hand, possess an extensive number of such conserved quantities and therefore the reduced density matrix requires specification of all the corresponding parameters (generalized Gibbs ensemble). However, here we show by unbiased statistical sampling of the individual eigenstates with a given finite energy density that the local description of an overwhelming majority of these states of even such an integrable system is actually Gibbs-like, i.e., requires only the energy density of the eigenstate. Rare eigenstates that cannot be represented by the Gibbs ensemble can also be sampled efficiently by our method and their local properties are then shown to be described by appropriately truncated generalized Gibbs ensembles. We further show that the presence of these rare eigenstates differentiates the model from the chaotic case and leads to the system being described by a generalized Gibbs ensemble at long time under a unitary dynamics following a sudden quench, even when the initial state is a typical (Gibbs-like) eigenstate of the prequench Hamiltonian.
Quantum dynamics in open quantum-classical systems.
Kapral, Raymond
2015-02-25
Often quantum systems are not isolated and interactions with their environments must be taken into account. In such open quantum systems these environmental interactions can lead to decoherence and dissipation, which have a marked influence on the properties of the quantum system. In many instances the environment is well-approximated by classical mechanics, so that one is led to consider the dynamics of open quantum-classical systems. Since a full quantum dynamical description of large many-body systems is not currently feasible, mixed quantum-classical methods can provide accurate and computationally tractable ways to follow the dynamics of both the system and its environment. This review focuses on quantum-classical Liouville dynamics, one of several quantum-classical descriptions, and discusses the problems that arise when one attempts to combine quantum and classical mechanics, coherence and decoherence in quantum-classical systems, nonadiabatic dynamics, surface-hopping and mean-field theories and their relation to quantum-classical Liouville dynamics, as well as methods for simulating the dynamics.
Quantum energy teleportation in a quantum Hall system
Energy Technology Data Exchange (ETDEWEB)
Yusa, Go; Izumida, Wataru; Hotta, Masahiro [Department of Physics, Tohoku University, Sendai 980-8578 (Japan)
2011-09-15
We propose an experimental method for a quantum protocol termed quantum energy teleportation (QET), which allows energy transportation to a remote location without physical carriers. Using a quantum Hall system as a realistic model, we discuss the physical significance of QET and estimate the order of energy gain using reasonable experimental parameters.
2013-02-15
Matthew James, Andre Carvalho and Michael Hush completed some work analyzing cross-phase modulation using single photon quantum filtering techniques...ANU Michael Hush January – June, 2012, Postdoc, ANU Matthew R. James Professor, Australian National University Ian R. Petersen Professor...appear, IEEE Trans. Aut. Control., 2013. A. R. R. Carvalho, M. R. Hush , and M. R. James, “Cavity driven by a single photon: Conditional dynamics and
2008-03-15
Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39-18 Publications: 1) W. Wasilewski and...K. Banaszek, Protecting an optical qubit against photon loss, Phys. Rev. A 75, 042316 (2007) 2) K. Banaszek and W. Wasilewski , Linear-optics...manipulations of photon-loss codes, Proceedings of NATO Advanced Research Workshop "Quantum Communication and Security" 3) W. Wasilewski , P. Kolenderski
Dynamical quenching of tunneling in molecular magnets
Energy Technology Data Exchange (ETDEWEB)
José Santander, María, E-mail: maria.jose.noemi@gmail.com [Recursos Educativos Quántica, Santiago (Chile); Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Nunez, Alvaro S., E-mail: alnunez@dfi.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile); Roldán-Molina, A. [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Avenida Universidad 330, Curauma, Valparaíso (Chile); Troncoso, Roberto E., E-mail: r.troncoso.c@gmail.com [Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Avda. Ecuador 3493, Santiago 9170124 (Chile); Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso (Chile)
2015-12-15
It is shown that a single molecular magnet placed in a rapidly oscillating magnetic field displays the phenomenon of quenching of tunneling processes. The results open a way to manipulate the quantum states of molecular magnets by means of radiation in the terahertz range. Our analysis separates the time evolution into slow and fast components thereby obtaining an effective theory for the slow dynamics. This effective theory presents quenching of the tunnel effect, in particular, stands out its difference with the so-called coherent destruction of tunneling. We support our prediction with numerical evidence based on an exact solution of Schrödinger's equation. - Highlights: • Single molecular magnets under rapidly oscillating magnetic fields is studied. • It is shown that this system displays the quenching of tunneling processes. • Our findings provide a control of quantum molecular magnets via terahertz radiation.
Effective Constraints for Quantum Systems
Bojowald, Martin; Skirzewski, Aureliano; Tsobanjan, Artur
2008-01-01
An effective formalism for quantum constrained systems is presented which allows manageable derivations of solutions and observables, including a treatment of physical reality conditions without requiring full knowledge of the physical inner product. Instead of a state equation from a constraint operator, an infinite system of constraint functions on the quantum phase space of expectation values and moments of states is used. The examples of linear constraints as well as the free non-relativistic particle in parameterized form illustrate how standard problems of constrained systems can be dealt with in this framework.
Hypothesis testing with open quantum systems.
Mølmer, Klaus
2015-01-30
Using a quantum circuit model we derive the maximal ability to distinguish which of several candidate Hamiltonians describe an open quantum system. This theory, in particular, provides the maximum information retrievable from continuous quantum measurement records, available when a quantum system is perturbatively coupled to a broadband quantized environment.
Open Quantum Systems An Introduction
Rivas, ´Angel
2012-01-01
In this volume the fundamental theory of open quantum systems is revised in the light of modern developments in the field. A unified approach to the quantum evolution of open systems is presented by merging concepts and methods traditionally employed by different communities, such as quantum optics, condensed matter, chemical physics and mathematical physics. The mathematical structure and the general properties of the dynamical maps underlying open system dynamics are explained in detail. The microscopic derivation of dynamical equations, including both Markovian and non-Markovian evolutions, is also discussed. Because of the step-by-step explanations, this work is a useful reference to novices in this field. However, experienced researches can also benefit from the presentation of recent results.
Pillai, Sreenadh Sasidharan; Yukawa, Hiroshi; Onoshima, Daisuke; Biju, Vasudevanpillai; Baba, Yoshinobu
2015-12-17
Quantum dots (QDs) have recently been investigated as fluorescent probes for detecting a very small number of biomolecules and live cells; however, the establishment of molecular imaging technology with on-off control of QD fluorescence remains to be established. Here we have achieved the fluorescence off state of QDs with the conjugation of black hole quencher (BHQ) molecules intermediated with peptide by using streptavidin-QDs585 and biotin-pep-BHQ-1. The fluorescence of streptavidin-QDs585 was decreased by the addition of biotin-pep-BHQ-1 in a dose-dependent manner. It has been suggested that the decrease in QDs585 fluorescence occurred through a Förster resonance energy transfer (FRET) mechanism from the analysis of fluorescence intensity and lifetime of streptavidin-QDs585 and QDs585-pep-BHQ-1. QDs585 fluorescence could be quenched by more than 60% efficiency in this system. The sequence of intermediate peptide (pep) was GPLGVRGK, which can be cleaved by matrix metalloproteinases (MMPs) produced by cancer cells. QDs585-pep-BHQ-1 is thus expected to detect the MMP production by the recovery of QDs585 fluorescence as a new bioanalytical agent for molecular imaging.
Quantum cloning attacks against PUF-based quantum authentication systems
Yao, Yao; Gao, Ming; Li, Mo; Zhang, Jian
2016-08-01
With the advent of physical unclonable functions (PUFs), PUF-based quantum authentication systems have been proposed for security purposes, and recently, proof-of-principle experiment has been demonstrated. As a further step toward completing the security analysis, we investigate quantum cloning attacks against PUF-based quantum authentication systems and prove that quantum cloning attacks outperform the so-called challenge-estimation attacks. We present the analytical expression of the false-accept probability by use of the corresponding optimal quantum cloning machines and extend the previous results in the literature. In light of these findings, an explicit comparison is made between PUF-based quantum authentication systems and quantum key distribution protocols in the context of cloning attacks. Moreover, from an experimental perspective, a trade-off between the average photon number and the detection efficiency is discussed in detail.
Fluorescence quenching of CdTe quantum dots by gardenoside%栀子甙对碲化镉量子点的荧光淬灭作用
Institute of Scientific and Technical Information of China (English)
张浩; 王芳; 马静; 卞伟
2015-01-01
CdTe quantum dots were synthesized in aqueous solution with 3‐mercaptopropionic acid as the stabilizer .The fluorescence quenching of 3‐mercaptopropionic acid stabilized CdTe quantum dots by gardenoside was investigated with fluorescence spectrometry .The effects of concentration of quan‐tum dots ,pH of buffer solution ,and reaction time on the fluorescence intensity of gardenoside/CdTe quantum dots system were examined .The optimum condition for the determination of gardenoside was established ,and the possible reaction mechanisms between gardenoside and as‐prepared CdTe quan‐tum dots were primarily studied .Results indicate that ,under the optimal experimental conditions ,the relative fluorescence intensity decreases linearly with the gardenoside concentration in the range of 2 × 10 - 7 -4 × 10 - 6 mol/L ,while the detection limit and relative standard deviation are 1 .4 × 10 - 7 mol/L and 0 .355% ,respectively .Moreover ,common metal cations ,sugars and amino acids have almost no apparent effect on the determination of gardenoside .In one word ,the present route can be readily used for the determination of gardenoside in the body fluid of human ;and the interaction between gardeno‐side and CdTe quantum dots is possibly dominated by dynamic quenching process .%以3‐巯基丙酸作为稳定剂，在水溶液中合成了 CdTe 量子点；采用荧光光谱法初步研究了栀子甙对巯基丙酸稳定的 CdTe 量子点的荧光淬灭作用，考察了量子点浓度、pH 、反应时间等多种因素对量子点‐栀子甙体系荧光强度的影响，确定了测定栀子甙的最佳实验条件；并初步探讨了栀子甙与该量子点相互作用的可能反应机理．结果表明，在最佳实验条件下，巯基丙酸稳定的 CdTe 量子点对栀子甙检测的线性范围为2×10－7～4×10－6 mol／L ，检出限为1．4×10－7 mol／L ，相对标准偏差为0．355％；且常见的金属阳离子、糖类和氨基酸对栀
Dynamic quenchers in fluorescently labeled membranes. Theory for quenching in a three-phase system.
Omann, G M; Glaser, M
1985-05-01
The theory for quenching of fluorescently labeled membranes by dynamic quenchers is described for a three-phase system: a fluorescently labeled membrane, a nonlabeled membrane, and an aqueous phase. Two different experimental protocols are possible to determine quenching parameters. Using the first protocol, partition coefficients and bimolecular quenching constants were determined for a hydrophobic quencher in carbazole-labeled membranes in the presence of an unlabeled reference membrane. These parameters determined for 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) using this three-phase analysis were in good agreement with values determined by a two-phase analysis without the reference lipid. Hence, the theory was verified. In the second protocol, the quencher partition coefficient was determined for unlabeled membranes in the presence of a carbazole-labeled reference membrane. Partition coefficients for DDE determined by this method were the same as partition coefficients determined for carbazole-labeled membranes using the two-phase analysis. The greater ease in determining partition coefficients and bimolecular quenching constants by the three-phase analysis and, in particular, the ability to determine the partition coefficient in unlabeled membranes make the three-phase analysis especially useful. This method was used to study the effect varying the membrane lipid composition has on the partition coefficient. The data indicate that partition coefficients of DDE in fluid membranes are not dramatically dependent upon polar head group composition, fatty acid composition, or cholesterol content. However, partitioning into gel-phase lipids is at least 100-fold less than fluid-phase lipids.
Dynamics of complex quantum systems
Akulin, Vladimir M
2014-01-01
This book gathers together a range of similar problems that can be encountered in different fields of modern quantum physics and that have common features with regard to multilevel quantum systems. The main motivation was to examine from a uniform standpoint various models and approaches that have been developed in atomic, molecular, condensed matter, chemical, laser and nuclear physics in various contexts. The book should help senior-level undergraduate, graduate students and researchers putting particular problems in these fields into a broader scientific context and thereby taking advantage of well-established techniques used in adjacent fields. This second edition has been expanded to include substantial new material (e.g. new sections on Dynamic Localization and on Euclidean Random Matrices and new chapters on Entanglement, Open Quantum Systems, and Coherence Protection). It is based on the author’s lectures at the Moscow Institute of Physics and Technology, at the CNRS Aimé Cotton Laboratory, and on ...
Dynamics of Non- interacting System with Long-Range Correlated Quenched Impurities
Institute of Scientific and Technical Information of China (English)
CHEN Yuan
2003-01-01
The theoretic renormalization group approach is applied to the study of the critical behavior of non-interacting system with long-range correlated quenched impurities, which has a power-like correlations r-(d-ρ). Totwo-loop order, the asymptotic scaling laws and the critical exponents are studied in the frame of a double (ε, ρ)expansion with ρ of order ε = 4 - d. In d ＜ 4, it is argued that the initial slip exponent θ = 0 together with the dynamicexponent z ＜ 2 is exact in this kind of random system.
OPERATIONAL EXPERIENCE WITH BEAM ABORT SYSTEM FOR SUPERCONDUCTING UNDULATOR QUENCH MITIGATION*
Energy Technology Data Exchange (ETDEWEB)
Harkay, Katherine C.; Dooling, Jeffrey C.; Sajaev, Vadim; Wang, Ju
2017-06-25
A beam abort system has been implemented in the Advanced Photon Source storage ring. The abort system works in tandem with the existing machine protection system (MPS), and its purpose is to control the beam loss location and, thereby, minimize beam loss-induced quenches at the two superconducting undulators (SCUs). The abort system consists of a dedicated horizontal kicker designed to kick out all the bunches in a few turns after being triggered by MPS. The abort system concept was developed on the basis of single- and multi-particle tracking simulations using elegant and bench measurements of the kicker pulse. Performance of the abort system—kick amplitudes and loss distributions of all bunches—was analyzed using beam position monitor (BPM) turn histories, and agrees reasonably well with the model. Beam loss locations indicated by the BPMs are consistent with the fast fiber-optic beam loss monitor (BLM) diagnostics described elsewhere [1,2]. Operational experience with the abort system, various issues that were encountered, limitations of the system, and quench statistics are described.
Khan, S.; Lima, A. A.; Aucelio, R. Q.
2017-01-01
The determination of captopril was performed by measuring the photoluminescence quenching of pH sensitive mercaptopropanoic acid capped CdTe quantum dots. Under optimum conditions, the calibration model (log F0/F as a function of the concentration of captopril) was linear up to 8 × 10-6 mol/L (1.7 μg/mL) and the limit of detection (xb - 3sb) was 2.7 × 10-7 mol/L (18 ng/mL). A possible mechanism for quenching is proposed. The method was applied in the determination of captopril in two commercial pharmaceutical formulations, indicating that it can be used for simple and fast quantitative control of commercial medicines or pharmaceutical preparations.
Quantum Indeterminacy of Cosmic Systems
Energy Technology Data Exchange (ETDEWEB)
Hogan, Craig J. [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
2013-12-30
It is shown that quantum uncertainty of motion in systems controlled mainly by gravity generally grows with orbital timescale $H^{-1}$, and dominates classical motion for trajectories separated by distances less than $\\approx H^{-3/5}$ in Planck units. For example, the cosmological metric today becomes indeterminate at macroscopic separations, $H_0^{-3/5}\\approx 60$ meters. Estimates suggest that entangled non-localized quantum states of geometry and matter may significantly affect fluctuations during inflation, and connect the scale of dark energy to that of strong interactions.
Quantum Indeterminacy of Cosmic Systems
Energy Technology Data Exchange (ETDEWEB)
Hogan, Craig J. [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
2013-12-30
It is shown that quantum uncertainty of motion in systems controlled mainly by gravity generally grows with orbital timescale $H^{-1}$, and dominates classical motion for trajectories separated by distances less than $\\approx H^{-3/5}$ in Planck units. For example, the cosmological metric today becomes indeterminate at macroscopic separations, $H_0^{-3/5}\\approx 60$ meters. Estimates suggest that entangled non-localized quantum states of geometry and matter may significantly affect fluctuations during inflation, and connect the scale of dark energy to that of strong interactions.
Polygamy of entanglement in multipartite quantum systems
Kim, Jeong San
2009-08-01
We show that bipartite entanglement distribution (or entanglement of assistance) in multipartite quantum systems is by nature polygamous. We first provide an analytical upper bound for the concurrence of assistance in bipartite quantum systems and derive a polygamy inequality of multipartite entanglement in arbitrary-dimensional quantum systems.
Quantum phase transitions in constrained Bose systems
Bonnes, Lars
2011-01-01
This doctoral thesis studies low dimensional quantum systems that can be realized in recent cold atom experiments. From the viewpoint of quantum statistical mechanics, the main emphasis is on the detailed study of the different quantum and thermal phases and their transitions using numerical methods, such as quantum Monte Carlo and the Tensor Network Renormalization Group. The first part of this work deals with a lattice Boson model subject to strong three-body losses. In a quantum-Zeno li...
Overview of progress in quantum systems control
Institute of Scientific and Technical Information of China (English)
CONG Shuang; ZHENG Yisong; JI Beichen; DAI Yi
2007-01-01
The development of the theory on quantum systems control in the last 20 years is reviewed in detail.The research on the controllability of quantum systems is first introduced,then the study on the quantum open-loop control methods often used for controlling simple quantum systems is analyzed briefly.The learning control method and the feedback control method are mainly discussed for they are two important methods in quantum systems control and their advantages and disadvantages are presented.According to the trends in quantum systems control development,the paper predicts the future trends of its development and applications.A complete design procedure necessary for the quantum control system is presented.Finally,several vital problems hindering the advancement of quantum control are pointed out.
Understanding quantum work in a quantum many-body system.
Wang, Qian; Quan, H T
2017-03-01
Based on previous studies in a single-particle system in both the integrable [Jarzynski, Quan, and Rahav, Phys. Rev. X 5, 031038 (2015)2160-330810.1103/PhysRevX.5.031038] and the chaotic systems [Zhu, Gong, Wu, and Quan, Phys. Rev. E 93, 062108 (2016)1539-375510.1103/PhysRevE.93.062108], we study the the correspondence principle between quantum and classical work distributions in a quantum many-body system. Even though the interaction and the indistinguishability of identical particles increase the complexity of the system, we find that for a quantum many-body system the quantum work distribution still converges to its classical counterpart in the semiclassical limit. Our results imply that there exists a correspondence principle between quantum and classical work distributions in an interacting quantum many-body system, especially in the large particle number limit, and further justify the definition of quantum work via two-point energy measurements in quantum many-body systems.
Quenching vibrations by collisions in cold traps: A quantum study for MgH+(X1 +) with 4He(1S)
Indian Academy of Sciences (India)
Domenico Caruso; Mario Tacconi; Franco A Gianturco; Ersin Yurtsever
2012-01-01
Quantum dynamics of superelastic collisions involving vibrational levels of MgH+(X1 +) ions in cold traps, interacting with 4He(1S) as a buffer gas at relative temperatures down to millikelvins, is discussed using an ab initio computed potential energy surface. The relative efficiency of collisional cooling with respect to collisional quenching of the internal vibrations is examined from the results of the relative sizes of the relevant cross sections in relation to predicting actual behaviour in cold traps. The present study indicates the feasibility of cooling vibrationally `hot’, trapped ions with the buffer gas.
Quantum hysteresis in coupled qubit-radiation systems
Acevedo, O. L.; Rodriguez, F. J.; Quiroga, L.; Johnson, N. F.
2012-02-01
We study theoretically the dynamical response of a set of solid-state qubits arbitrarily coupled to a radiation field which is confined in a cavity. Driving the coupling strength in round trips, between weak and strong values, we quantify the hysteresis or irreversible quantum dynamics. The matter-radiation system is modeled as a finite-size Dicke model which has previously been used to describe equilibrium (including quantum phase transition) properties of systems such as quantum dots in a microcavity, and superconducting circuit QED. Here we extend this model to address non-equilibrium situations. Analyzing the system's quantum fidelity, we find that the near-adiabatic regime exhibits the richest phenomena, with a strong asymmetry in the internal collective dynamics depending on which phase is chosen as the starting point. We identify significant deviations from the conventional Landau-Zener-Stuckelberg formulae, in particular from cycles starting in the superradiant phase. In the diabatic or impulsive regime, the system remains quenched and there is little hysteresis. By contrast, depending on the specifications of the cycle, the radiation subsystem can exhibit the emergence of non-classicality, complexity and sub-Planckian structures as evidenced by its Wigner function.
Quantum Computing in Solid State Systems
Ruggiero, B; Granata, C
2006-01-01
The aim of Quantum Computation in Solid State Systems is to report on recent theoretical and experimental results on the macroscopic quantum coherence of mesoscopic systems, as well as on solid state realization of qubits and quantum gates. Particular attention has been given to coherence effects in Josephson devices. Other solid state systems, including quantum dots, optical, ion, and spin devices which exhibit macroscopic quantum coherence are also discussed. Quantum Computation in Solid State Systems discusses experimental implementation of quantum computing and information processing devices, and in particular observations of quantum behavior in several solid state systems. On the theoretical side, the complementary expertise of the contributors provides models of the various structures in connection with the problem of minimizing decoherence.
Eigenfunctions in chaotic quantum systems
Energy Technology Data Exchange (ETDEWEB)
Baecker, Arnd
2007-07-01
The structure of wavefunctions of quantum systems strongly depends on the underlying classical dynamics. In this text a selection of articles on eigenfunctions in systems with fully chaotic dynamics and systems with a mixed phase space is summarized. Of particular interest are statistical properties like amplitude distribution and spatial autocorrelation function and the implication of eigenfunction structures on transport properties. For systems with a mixed phase space the separation into regular and chaotic states does not always hold away from the semiclassical limit, such that chaotic states may completely penetrate into the region of the regular island. The consequences of this flooding are discussed and universal aspects highlighted. (orig.)
Perturbative approach to Markovian open quantum systems.
Li, Andy C Y; Petruccione, F; Koch, Jens
2014-05-08
The exact treatment of Markovian open quantum systems, when based on numerical diagonalization of the Liouville super-operator or averaging over quantum trajectories, is severely limited by Hilbert space size. Perturbation theory, standard in the investigation of closed quantum systems, has remained much less developed for open quantum systems where a direct application to the Lindblad master equation is desirable. We present such a perturbative treatment which will be useful for an analytical understanding of open quantum systems and for numerical calculation of system observables which would otherwise be impractical.
A Diffusion Equation for Quantum Adiabatic Systems
Jain, S R
1998-01-01
For ergodic adiabatic quantum systems, we study the evolution of energy distribution as the system evolves in time. Starting from the von Neumann equation for the density operator, we obtain the quantum analogue of the Smoluchowski equation on coarse-graining over the energy spectrum. This result brings out the precise notion of quantum diffusion.
Logical entropy of quantum dynamical systems
Directory of Open Access Journals (Sweden)
Ebrahimzadeh Abolfazl
2016-01-01
Full Text Available This paper introduces the concepts of logical entropy and conditional logical entropy of hnite partitions on a quantum logic. Some of their ergodic properties are presented. Also logical entropy of a quantum dynamical system is dehned and ergodic properties of dynamical systems on a quantum logic are investigated. Finally, the version of Kolmogorov-Sinai theorem is proved.
Wei, Xiaoling; Wang, Xiaojun; Gong, Qi; Wang, Lisheng; Zhou, Shiwu
2015-01-01
This study shows that alizarin red (AR) only slightly quenched fluorescence for acridine orange (AO) in an AR/AO mixed solution at pH = 5-6. The reduced fluorescent signal was closely and linearly associated with the level of MT added to the system, which is the basis for a new quantitative MT assay method using the fluorescence quenching reaction in the AO-AR system. The results show that under optimal conditions, this method had a 14.9-43.5 mg L-1 linear detection range with a 1.38 mg L-1 detection limit and 1.24% precision. In addition, this method was used to determine the MT levels in the commercially available MT-containing pesticides and suppositories, which showed a 96.6-103% recovery. Therefore, this method has multiple advantages, including simple and fast operation, high accuracy and low cost. Moreover, herein, we investigated the underlying mechanism in-depth using an ultraviolet (UV) spectroscopic technique.
Critical relaxation with overdamped quasiparticles in open quantum systems
Lang, Johannes; Piazza, Francesco
2016-09-01
We study the late-time relaxation following a quench in an open quantum many-body system. We consider the open Dicke model, describing the infinite-range interactions between N atoms and a single, lossy electromagnetic mode. We show that the dynamical phase transition at a critical atom-light coupling is characterized by the interplay between reservoir-driven and intrinsic relaxation processes in the absence of number conservation. Above the critical coupling, small fluctuations in the occupation of the dominant quasiparticle mode start to grow in time, while the quasiparticle lifetime remains finite due to losses. Near the critical interaction strength, we observe a crossover between exponential and power-law 1 /τ relaxation, the latter driven by collisions between quasiparticles. For a quench exactly to the critical coupling, the power-law relaxation extends to infinite times, but the finite lifetime of quasiparticles prevents aging from appearing in two-times response and correlation functions. We predict our results to be accessible to quench experiments with ultracold bosons in optical resonators.
Resonances in open quantum systems
Eleuch, Hichem; Rotter, Ingrid
2017-02-01
The Hamilton operator of an open quantum system is non-Hermitian. Its eigenvalues are generally complex and provide not only the energies but also the lifetimes of the states of the system. The states may couple via the common environment of scattering wave functions into which the system is embedded. This causes an external mixing (EM) of the states. Mathematically, EM is related to the existence of singular (the so-called exceptional) points. The eigenfunctions of a non-Hermitian operator are biorthogonal, in contrast to the orthogonal eigenfunctions of a Hermitian operator. A quantitative measure for the ratio between biorthogonality and orthogonality is the phase rigidity of the wave functions. At and near an exceptional point (EP), the phase rigidity takes its minimum value. The lifetimes of two nearby eigenstates of a quantum system bifurcate under the influence of an EP. At the parameter value of maximum width bifurcation, the phase rigidity approaches the value one, meaning that the two eigenfunctions become orthogonal. However, the eigenfunctions are externally mixed at this parameter value. The S matrix and therewith the cross section do contain, in the one-channel case, almost no information on the EM of the states. The situation is completely different in the case with two (or more) channels where the resonance structure is strongly influenced by the EM of the states and interesting features of non-Hermitian quantum physics are revealed. We provide numerical results for two and three nearby eigenstates of a non-Hermitian Hamilton operator that are embedded in one common continuum and are influenced by two adjoining EPs. The results are discussed. They are of interest for an experimental test of the non-Hermitian quantum physics as well as for applications.
Quantum chaotic attractor in a dissipative system
Liu, W V; Schieve, William C.
1997-01-01
A dissipative quantum system is treated here by coupling it with a heat bath of harmonic oscillators. Through quantum Langevin equations and Ehrenfest's theorem, we establish explicitly the quantum Duffing equations with a double-well potential chosen. A quantum noise term appears the only driving force in dynamics. Numerical studies show that the chaotic attractor exists in this system while chaos is certainly forbidden in the classical counterpart.
Dissipative properties of quantum systems.
Grecos, A P; Prigogine, I
1972-06-01
We consider the dissipative properties of large quantum systems from the point of view of kinetic theory. The existence of a nontrivial collision operator imposes restrictions on the possible collisional invariants of the system. We consider a model in which a discrete level is coupled to a set of quantum states and which, in the limit of a large "volume," becomes the Friedrichs model. Because of its simplicity this model allows a direct calculation of the collision operator as well as of related operators and the constants of the motion. For a degenerate spectrum the calculations become more involved but the conclusions remain simple. The special role played by the invariants that are functions of the Hamiltonion is shown to be a direct consequence of the existence of a nonvanishing collision operator. For a class of observables we obtain ergodic behavior, and this reformulation of the ergodic problem may be used in statistical mechanics to study the ergodicity of large quantum systems containing a small physical parameter such as the coupling constant or the concentration.
Quantum state engineering in hybrid open quantum systems
Joshi, Chaitanya; Larson, Jonas; Spiller, Timothy P.
2016-04-01
We investigate a possibility to generate nonclassical states in light-matter coupled noisy quantum systems, namely, the anisotropic Rabi and Dicke models. In these hybrid quantum systems, a competing influence of coherent internal dynamics and environment-induced dissipation drives the system into nonequilibrium steady states (NESSs). Explicitly, for the anisotropic Rabi model, the steady state is given by an incoherent mixture of two states of opposite parities, but as each parity state displays light-matter entanglement, we also find that the full state is entangled. Furthermore, as a natural extension of the anisotropic Rabi model to an infinite spin subsystem, we next explored the NESS of the anisotropic Dicke model. The NESS of this linearized Dicke model is also an inseparable state of light and matter. With an aim to enrich the dynamics beyond the sustainable entanglement found for the NESS of these hybrid quantum systems, we also propose to combine an all-optical feedback strategy for quantum state protection and for establishing quantum control in these systems. Our present work further elucidates the relevance of such hybrid open quantum systems for potential applications in quantum architectures.
Simulation of n-qubit quantum systems. III. Quantum operations
Radtke, T.; Fritzsche, S.
2007-05-01
During the last decade, several quantum information protocols, such as quantum key distribution, teleportation or quantum computation, have attracted a lot of interest. Despite the recent success and research efforts in quantum information processing, however, we are just at the beginning of understanding the role of entanglement and the behavior of quantum systems in noisy environments, i.e. for nonideal implementations. Therefore, in order to facilitate the investigation of entanglement and decoherence in n-qubit quantum registers, here we present a revised version of the FEYNMAN program for working with quantum operations and their associated (Jamiołkowski) dual states. Based on the implementation of several popular decoherence models, we provide tools especially for the quantitative analysis of quantum operations. Apart from the implementation of different noise models, the current program extension may help investigate the fragility of many quantum states, one of the main obstacles in realizing quantum information protocols today. Program summaryTitle of program: Feynman Catalogue identifier: ADWE_v3_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWE_v3_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: None Operating systems: Any system that supports MAPLE; tested under Microsoft Windows XP, SuSe Linux 10 Program language used:MAPLE 10 Typical time and memory requirements: Most commands that act upon quantum registers with five or less qubits take ⩽10 seconds of processor time (on a Pentium 4 processor with ⩾2 GHz or equivalent) and 5-20 MB of memory. Especially when working with symbolic expressions, however, the memory and time requirements critically depend on the number of qubits in the quantum registers, owing to the exponential dimension growth of the associated Hilbert space. For example, complex (symbolic) noise models (with several Kraus operators) for multi-qubit systems
Could nanostructure be unspeakable quantum system?
Aristov, V V
2010-01-01
Heisenberg, Bohr and others were forced to renounce on the description of the objective reality as the aim of physics because of the paradoxical quantum phenomena observed on the atomic level. The contemporary quantum mechanics created on the base of their positivism point of view must divide the world into speakable apparatus which amplifies microscopic events to macroscopic consequences and unspeakable quantum system. Examination of the quantum phenomena corroborates the confidence expressed by creators of quantum theory that the renunciation of realism should not apply on our everyday macroscopic world. Nanostructures may be considered for the present as a boundary of realistic description for all phenomena including the quantum one.
Periodically driven ergodic and many-body localized quantum systems
Energy Technology Data Exchange (ETDEWEB)
Ponte, Pedro [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada); Department of Physics and Astronomy, University of Waterloo, ON N2L 3G1 (Canada); Chandran, Anushya [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada); Papić, Z., E-mail: zpapic@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada); Institute for Quantum Computing, Waterloo, ON N2L 3G1 (Canada); Abanin, Dmitry A. [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada); Institute for Quantum Computing, Waterloo, ON N2L 3G1 (Canada)
2015-02-15
We study dynamics of isolated quantum many-body systems whose Hamiltonian is switched between two different operators periodically in time. The eigenvalue problem of the associated Floquet operator maps onto an effective hopping problem. Using the effective model, we establish conditions on the spectral properties of the two Hamiltonians for the system to localize in energy space. We find that ergodic systems always delocalize in energy space and heat up to infinite temperature, for both local and global driving. In contrast, many-body localized systems with quenched disorder remain localized at finite energy. We support our conclusions by numerical simulations of disordered spin chains. We argue that our results hold for general driving protocols, and discuss their experimental implications.
Optimal Control of Finite Dimensional Quantum Systems
Mendonca, Paulo E M F
2009-01-01
This thesis addresses the problem of developing a quantum counter-part of the well established classical theory of control. We dwell on the fundamental fact that quantum states are generally not perfectly distinguishable, and quantum measurements typically introduce noise in the system being measured. Because of these, it is generally not clear whether the central concept of the classical control theory -- that of observing the system and then applying feedback -- is always useful in the quantum setting. We center our investigations around the problem of transforming the state of a quantum system into a given target state, when the system can be prepared in different ways, and the target state depends on the choice of preparation. We call this the "quantum tracking problem" and show how it can be formulated as an optimization problem that can be approached both numerically and analytically. This problem provides a simple route to the characterization of the quantum trade-off between information gain and distu...
Past Quantum States of a Monitored System
DEFF Research Database (Denmark)
Gammelmark, Søren; Julsgaard, Brian; Mølmer, Klaus
2013-01-01
A density matrix ρ(t) yields probabilistic information about the outcome of measurements on a quantum system. We introduce here the past quantum state, which, at time T, accounts for the state of a quantum system at earlier times tstate Ξ(t) is composed of two objects, ρ......(t) and E(t), conditioned on the dynamics and the probing of the system until t and in the time interval [t, T], respectively. The past quantum state is characterized by its ability to make better predictions for the unknown outcome of any measurement at t than the conventional quantum state at that time....... On the one hand, our formalism shows how smoothing procedures for estimation of past classical signals by a quantum probe [M. Tsang, Phys. Rev. Lett. 102 250403 (2009)] apply also to describe the past state of the quantum system itself. On the other hand, it generalizes theories of pre- and postselected...
Classical equations for quantum systems
Energy Technology Data Exchange (ETDEWEB)
Gell-Mann, M. (Theoretical Astrophysics Group (T-6), Los Alamos National Laboratory, Los Alamos, New Mexico 87545) (United States) (Santa Fe Institute, 1660 Old Pecos Trail, Santa Fe, New Mexico 87501); Hartle, J.B. (Department of Physics, University of California enSanta Barbara, Santa Barbara, (California) 93106)
1993-04-15
The origin of the phenomenological deterministic laws that approximately govern the quasiclassical domain of familiar experience is considered in the context of the quantum mechanics of closed systems such as the universe as a whole. A formulation of quantum mechanics is used that predicts probabilities for the individual members of a set of alternative coarse-grained histories that [ital decohere], which means that there is negligible quantum interference between the individual histories in the set. We investigate the requirements for coarse grainings to yield decoherent sets of histories that are quasiclassical, i.e., such that the individual histories obey, with high probability, effective classical equations of motion interrupted continually by small fluctuations and occasionally by large ones. We discuss these requirements generally but study them specifically for coarse grainings of the type that follows a distinguished subset of a complete set of variables while ignoring the rest. More coarse graining is needed to achieve decoherence than would be suggested by naive arguments based on the uncertainty principle. Even coarser graining is required in the distinguished variables for them to have the necessary inertia to approach classical predictability in the presence of the noise consisting of the fluctuations that typical mechanisms of decoherence produce. We describe the derivation of phenomenological equations of motion explicitly for a particular class of models.
Energy Technology Data Exchange (ETDEWEB)
Khan, Sarzamin; Carneiro, Leonardo S.A. [Chemistry Department, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro-RJ (Brazil); Romani, Eric C.; Larrudé, Dunieskys G. [Physics Department, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro-RJ (Brazil); Aucelio, Ricardo Q., E-mail: aucelior@puc-rio.br [Chemistry Department, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro-RJ (Brazil)
2014-12-15
The determination of L-thyroxine is proposed based on the photoluminescence quenching effect caused on the L-cysteine modified ZnS quantum dots (L-cysteine ZnS QDs) aqueous dispersion. Under optimum conditions, the analytical response followed a Stern–Volmer model and the experimental conditions were adjusted to enable a robust and reproducible photoluminescence signal. The linear response observed in the quantum dots aqueous dispersion covered the L-thyroxine concentration from the LOQ (2.0×10{sup −8} mol L{sup −1}) to 4.0×10{sup −6} mol L{sup −1}. The approach was tested in the determination of L-thyroxine in pharmaceutical formulations used to treat patients with thyroid gland disorder. The percent recoveries in controlled samples were between 93.3 and 103%. Analyte fortified saliva was also evaluated as a possible sample for L-thyroxine monitoring of a patient under treatment. It was identified a static type of photoluminescence quenching caused by L-thyroxine. - Highlights: • L-cysteine ZnS QDs were used as a photoluminescent probe to detect L-thyroxine. • Intensity of probe decreases following a Stern–Volmer model. • The method can detect down ng L{sup −1} levels of L-thyroxine in the probe dispersion. • Method was used to determinate of L-thyroxine in saliva and in pharmaceuticals. • Mechanism of interaction between L-thyroxine and quantum dots was studied.
Zhang, Kun; Zheng, Xin; Shen, Dong-sheng; Wang, Mei-zhen; Feng, Hua-jun; He, Hong-zhen; Wang, Shuo; Wang, Jue-hua
2015-04-01
The introduction of a gene, strain, or microbial consortium into an indigenous bacterial population is known as bioaugmentation. This technique has been proposed as an effective strategy for accelerating and enhancing the removal of recalcitrant and toxic compounds during wastewater treatment. In this study, three types of reactors were used to test whether quorum sensing plays an important role in bioaugmented systems. Reverse transcriptase polymerase chain reaction showed that the inoculated strain, HF-1, successfully colonized in the bioaugmented reactor. Meanwhile, no HF-1 colonization was observed in the quorum-quenching and non-bioaugmented reactors. Removal of nicotine in the bioaugmented reactor was almost 100%, and removal of total organic carbon (TOC) was higher than 50%. However, less than 20% of nicotine and 30% of TOC was removed in quorum-quenching and non-bioaugmented reactors. Moreover, the release of acylated homoserine lactones reached the threshold for HF-1 biofilm formation in bioaugmented reactors but not in quorum-quenching or non-bioaugmented reactors. The addition of porcine kidney acylase I, a quenching reagent, to the quorum-quenching reactor hampered the colonization of HF-1. Together, these results demonstrate that quorum sensing plays an important role in HF-1 colonization of bioaugmented systems.
Adiabatic and Non-adiabatic quenches in a Spin-1 Bose Einstein Condensate
Boguslawski, Matthew; Hebbe Madhusudhana, Bharath; Anquez, Martin; Robbins, Bryce; Barrios, Maryrose; Hoang, Thai; Chapman, Michael
2016-05-01
A quantum phase transition (QPT) is observed in a wide range of phenomena. We have studied the dynamics of a spin-1 ferromagnetic Bose-Einstein condensate for both adiabatic and non-adiabatic quenches through a QPT. At the quantum critical point (QCP), finite size effects lead to a non-zero gap, which makes an adiabatic quench possible through the QPT. We experimentally demonstrate such a quench, which is forbidden at the mean field level. For faster quenches through the QCP, the vanishing energy gap causes the reaction timescale of the system to diverge, preventing the system from adiabatically following the ground state. We measure the temporal evolution of the spin populations for different quench speeds and determine the exponents characterizing the scaling of the onset of excitations, which are in good agreement with the predictions of Kibble-Zurek mechanism.
Caux, Jean-Sébastien
2016-06-01
We give a pedagogical introduction to the methodology of the Quench Action, which is an effective representation for the calculation of time-dependent expectation values of physical operators following a generic out-of-equilibrium state preparation protocol (for example a quantum quench). The representation, originally introduced in Caux and Essler (2013 Phys. Rev. Lett. 110 257203), is founded on a mixture of exact data for overlaps together with variational reasonings. It is argued to be quite generally valid and thermodynamically exact for arbitrary times after the quench (from short times all the way up to the steady state), and applicable to a wide class of physically relevant observables. Here, we introduce the method and its language, give an overview of some recent results, suggest a roadmap and offer some perspectives on possible future research directions.
Quantum mechanics in complex systems
Hoehn, Ross Douglas
This document should be considered in its separation; there are three distinct topics contained within and three distinct chapters within the body of works. In a similar fashion, this abstract should be considered in three parts. Firstly, we explored the existence of multiply-charged atomic ions by having developed a new set of dimensional scaling equations as well as a series of relativistic augmentations to the standard dimensional scaling procedure and to the self-consistent field calculations. Secondly, we propose a novel method of predicting drug efficacy in hopes to facilitate the discovery of new small molecule therapeutics by modeling the agonist-protein system as being similar to the process of Inelastic Electron Tunneling Spectroscopy. Finally, we facilitate the instruction in basic quantum mechanical topics through the use of quantum games; this method of approach allows for the generation of exercises with the intent of conveying the fundamental concepts within a first year quantum mechanics classroom. Furthermore, no to be mentioned within the body of the text, yet presented in appendix form, certain works modeling the proliferation of cells types within the confines of man-made lattices for the purpose of facilitating artificial vascular transplants. In Chapter 2, we present a theoretical framework which describes multiply-charged atomic ions, their stability within super-intense laser fields, also lay corrections to the systems due to relativistic effects. Dimensional scaling calculations with relativistic corrections for systems: H, H-, H 2-, He, He-, He2-, He3- within super-intense laser fields were completed. Also completed were three-dimensional self consistent field calculations to verify the dimensionally scaled quantities. With the aforementioned methods the system's ability to stably bind 'additional' electrons through the development of multiple isolated regions of high potential energy leading to nodes of high electron density is shown
Joint system quantum descriptions arising from local quantumness
Cooney, Tom; Navascues, Miguel; Perez-Garcia, David; Villanueva, Ignacio
2012-01-01
Bipartite correlations generated by non-signalling physical systems that admit a finite-dimensional local quantum description cannot exceed the quantum limits, i.e., they can always be interpreted as distant measurements of a bipartite quantum state. Here we consider the effect of dropping the assumption of finite dimensionality. Remarkably, we find that the same result holds provided that we relax the tensor structure of space-like separated measurements to mere commutativity. We argue why an extension of this result to tensor representations seems unlikely.
2016-01-01
We present a new open-source Python package for exact diagonalization and quantum dynamics of spin(-photon) chains, called QuSpin, supporting the use of various symmetries and (imaginary) time evolution for chains up to 32 sites in length. The package is well-suited to study, among others, quantum quenches at finite and infinite times, the Eigenstate Thermalisation hypothesis, many-body localisation and other dynamical phase transitions, periodically-driven (Floquet) systems, adiabatic and co...
A study of Quantum Correlations in Open Quantum Systems
Chakrabarty, Indranil; Siddharth, Nana
2010-01-01
In this work, we study quantum correlations in mixed states. The states studied are modelled by a two-qubit system interacting with its environment via a quantum nondemolition (purely dephasing) as well as dissipative type of interaction. The entanglement dynamics of this two qubit system is analyzed and the existence of entangled states which do not violate Bell's inequality, but can still be useful as a potential resource for teleportation are reported. In addition, a comparative study of various measures of quantum correlations, like Concurrence, Bell's inequality, Discord and Teleportation fidelity, is made on these states, generated by the above evolutions. Interestingly, examples are found, of states, where entanglement is vanishing, but discord is non-vanishing, bringing out the fact that entanglement is a subset of quantum correlations.
Quantum speed limits in open system dynamics.
del Campo, A; Egusquiza, I L; Plenio, M B; Huelga, S F
2013-02-01
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 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 role of the Hamiltonian being played by the adjoint of the generator of the dynamical semigroup. The utility of the new bound is exemplified in different scenarios, ranging from the estimation of the passage time to the determination of precision limits for quantum metrology in the presence of dephasing noise.
Zhou, Jinwei; Lukin, Leonid V; Braun, Charles L
2008-08-21
Photoinduced transient dipole experiments are used to measure the effective charge separation distance, which is equivalent to the photoinduced change in dipole moment divided by the electron charge of flexible electron-donor/acceptor systems, D-(CH2)n-A, where D is 4- N,N-dimethylaniline, A is 9-anthryl, and n = 3, 4. We find that the dipole moments increase strongly with solvent polarity. For the compound with n = 4 (DBA4), analysis of dipole signals indicates that the effective charge separation distances in toluene, 1,4-dioxane, ethyl acetate, tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 2-methylpentanone-3, 3-pentanone, and benzonitrile are 2.2, 2.5, 4.5, 4.7, 5.5, 5.5, 4.8, and 6.3 A, respectively. These values can be understood as the root-mean-square charge separation distance in the solutions of different solvents. We assume that the folded contact configuration has a separation distance of 3.5 A, the extended, solvent-separated configuration has a separation distance of 8.0 A, and that they are the only two stable species after electron-transfer quenching. The formation efficiencies of contact radical ion pairs (CRIPs) and solvent-separated radical ion pairs (SSRIPs) are estimated in different solvents. The results indicate that a significant fraction of the ion pairs exist as solvent-separated ion pairs when the dielectric constant of the solvent is larger than 10. These results indicate that electron-transfer quenching can indeed happen at large separations in polar solvents. They also reveal that there is a barrier for ion pairs formed at large separations, hindering collapse to a contact separation of around 3.5 A.
Quantum ratchets in dissipative chaotic systems.
Carlo, Gabriel G; Benenti, Giuliano; Casati, Giulio; Shepelyansky, Dima L
2005-04-29
Using the method of quantum trajectories, we study a quantum chaotic dissipative ratchet appearing for particles in a pulsed asymmetric potential in the presence of a dissipative environment. The system is characterized by directed transport emerging from a quantum strange attractor. This model exhibits, in the limit of small effective Planck constant, a transition from quantum to classical behavior, in agreement with the correspondence principle. We also discuss parameter values suitable for the implementation of the quantum ratchet effect with cold atoms in optical lattices.
Hybrid quantum systems of atoms and ions
Zipkes, Christoph; Palzer, Stefan; Sias, Carlo; Köhl, Michael
2010-01-01
In recent years, ultracold atoms have emerged as an exceptionally controllable experimental system to investigate fundamental physics, ranging from quantum information science to simulations of condensed matter models. Here we go one step further and explore how cold atoms can be combined with other quantum systems to create new quantum hybrids with tailored properties. Coupling atomic quantum many-body states to an independently controllable single-particle gives access to a wealth of novel physics and to completely new detection and manipulation techniques. We report on recent experiments in which we have for the first time deterministically placed a single ion into an atomic Bose Einstein condensate. A trapped ion, which currently constitutes the most pristine single particle quantum system, can be observed and manipulated at the single particle level. In this single-particle/many-body composite quantum system we show sympathetic cooling of the ion and observe chemical reactions of single particles in situ...
Hybrid quantum systems of atoms and ions
Energy Technology Data Exchange (ETDEWEB)
Zipkes, Christoph; Ratschbacher, Lothar; Palzer, Stefan; Sias, Carlo; Koehl, Michael [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
2011-01-10
In recent years, ultracold atoms have emerged as an exceptionally controllable experimental system to investigate fundamental physics, ranging from quantum information science to simulations of condensed matter models. Here we go one step further and explore how cold atoms can be combined with other quantum systems to create new quantum hybrids with tailored properties. Coupling atomic quantum many-body states to an independently controllable single-particle gives access to a wealth of novel physics and to completely new detection and manipulation techniques. We report on recent experiments in which we have for the first time deterministically placed a single ion into an atomic Bose Einstein condensate. A trapped ion, which currently constitutes the most pristine single particle quantum system, can be observed and manipulated at the single particle level. In this single-particle/many-body composite quantum system we show sympathetic cooling of the ion and observe chemical reactions of single particles in situ.
Quantum Q systems: from cluster algebras to quantum current algebras
Di Francesco, Philippe; Kedem, Rinat
2017-02-01
This paper gives a new algebraic interpretation for the algebra generated by the quantum cluster variables of the A_r quantum Q-system (Di Francesco and Kedem in Int Math Res Not IMRN 10:2593-2642, 2014). We show that the algebra can be described as a quotient of the localization of the quantum algebra U_{√{q}}({n}[u,u^{-1}])subset U_{√{q}}(widehat{{sl}}_2), in the Drinfeld presentation. The generating current is made up of a subset of the cluster variables which satisfy the Q-system, which we call fundamental. The other cluster variables are given by a quantum determinant-type formula, and are polynomials in the fundamental generators. The conserved quantities of the discrete evolution (Di Francesco and Kedem in Adv Math 228(1):97-152, 2011) described by quantum Q-system generate the Cartan currents at level 0, in a non-standard polarization. The rest of the quantum affine algebra is also described in terms of cluster variables.
Quantum Q systems: from cluster algebras to quantum current algebras
Di Francesco, Philippe; Kedem, Rinat
2016-11-01
This paper gives a new algebraic interpretation for the algebra generated by the quantum cluster variables of the A_r quantum Q-system (Di Francesco and Kedem in Int Math Res Not IMRN 10:2593-2642, 2014). We show that the algebra can be described as a quotient of the localization of the quantum algebra U_{√{q}}({{n}}[u,u^{-1}])subset U_{√{q}}(widehat{{{sl}}}_2) , in the Drinfeld presentation. The generating current is made up of a subset of the cluster variables which satisfy the Q-system, which we call fundamental. The other cluster variables are given by a quantum determinant-type formula, and are polynomials in the fundamental generators. The conserved quantities of the discrete evolution (Di Francesco and Kedem in Adv Math 228(1):97-152, 2011) described by quantum Q-system generate the Cartan currents at level 0, in a non-standard polarization. The rest of the quantum affine algebra is also described in terms of cluster variables.
Quantum chaos in open systems a quantum state diffusion analysis
Brun, T A; Schack, R; Brun, Todd A; Percival, Ian C; Schack, Rudiger
1995-01-01
Except for the universe, all quantum systems are open, and according to quantum state diffusion theory, many systems localize to wave packets in the neighborhood of phase space points. This is due to decoherence from the interaction with the environment, and makes the quasiclassical limit of such systems both more realistic and simpler in many respects than the more familiar quasiclassical limit for closed systems. A linearized version of this theory leads to the correct classical dynamics in the macroscopic limit, even for nonlinear and chaotic systems. We apply the theory to the forced, damped Duffing oscillator, comparing the numerical results of the full and linearized equations, and argue that this can be used to make explicit calculations in the decoherent histories formalism of quantum mechanics.
Quasi-Periodically Driven Quantum Systems
Verdeny, Albert; Puig, Joaquim; Mintert, Florian
2016-10-01
Floquet theory provides rigorous foundations for the theory of periodically driven quantum systems. In the case of non-periodic driving, however, the situation is not so well understood. Here, we provide a critical review of the theoretical framework developed for quasi-periodically driven quantum systems. Although the theoretical footing is still under development, we argue that quasi-periodically driven quantum systems can be treated with generalisations of Floquet theory in suitable parameter regimes. Moreover, we provide a generalisation of the Floquet-Magnus expansion and argue that quasi-periodic driving offers a promising route for quantum simulations.
Dwiecki, Krzysztof; Neunert, Grażyna; Nogala-Kałucka, Małgorzata; Polewski, Krzysztof
2015-01-01
Changes of the photoluminescent properties of QD in the presence of oxidized catechin (CQ) were investigated by absorption, steady-state fluorescence, fluorescence lifetime and dynamic light scattering measurements. Photoluminescence intensity and fluorescence lifetime was decreasing with increasing CQ concentration. Dynamic light scattering technique found the hydrodynamic diameter of QD suspension in water is in range of 45 nm, whereas in presence of CQ increased to mean values of 67 nm. Calculated from absorption peak position of excition band indicated on average QD size of 3.2 nm. Emission spectroscopy and time-resolved emission studies confirmed preservation of electronic band structure in QD-CQ aggregates. On basis of the presented results, the elucidated mechanism of QD fluorescence quenching is a result of the interaction between QD and CQ due to electron transfer and electrostatic attraction. The results of fluorescence quenching of water-soluble CdTe quantum dot (QD) capped with thiocarboxylic acid were used to implement a simple and fast method to determine the presence of native antioxidant quinones in aqueous solutions. Feasibility studies on this method carried out with oxidized catechin showed a linear relation between the QD emission and quencher concentration, in range from 1 up to 200 μM. The wide linear range of concentration dependence makes it possible to apply this method for the fast and sensitive detection of quinones in solutions.
Nurerk, Piyaluk; Kanatharana, Proespichaya; Bunkoed, Opas
2016-03-01
CdTe quantum dots (QDs) capped with different stabilizers, i.e. thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA) and glutathione (GSH) were investigated as fluorescent probes for the determination of Cu(2+). The stabilizer was shown to play an important role in both the sensitivity and selectivity for the determination of Cu(2+). TGA-capped CdTe QDs showed the highest sensitivity, followed by the MPA and GSH-capped CdTe QDs, respectively. The TGA- and MPA-capped CdTe QDs were not selective for Cu(2+) that was affected by Ag(+). The GSH-capped CdTe QDs were insensitive to Ag(+) and were used to determine Cu(2+) in water samples. Under optimal conditions, quenching of the fluorescence intensity (F0/F) increased linearly with the concentration of Cu(2+) over a range of 0.10-4.0 µg/mL and the detection limit was 0.06 µg/mL. The developed method was successfully applied to the determination of Cu(2+) in water samples. Good recoveries of 93-104%, with a relative standard deviation of < 6% demonstrated that the developed simple method was accurate and reliable. The quenching mechanisms were also described.
Classical and quantum phases of low-dimensional dipolar systems
Energy Technology Data Exchange (ETDEWEB)
Cartarius, Florian
2016-09-22
In this thesis we present a detailed study of the phase diagram of ultracold bosonic atoms confined along a tight atomic wave guide, along which they experience an optical lattice potential. In this quasi-one dimensional model we analyse the interplay between interactions and quantum fluctuations in (i) determining the non-equilibrium steady state after a quench and (ii) giving rise to novel equilibrium phases, when the interactions combine the s-wave contact interaction and the anisotropic long range dipole-dipole interactions. In detail, in the first part of the thesis we study the depinning of a gas of impenetrable bosons following the sudden switch of of the optical lattice. By means of a Bose-Fermi mapping we infer the exact quantum dynamical evolution and show that in the thermodynamic limit the system is in a non-equilibrium steady state without quasi-long range order. In the second part of the thesis, we study the effect of quantum fluctuations on the linear-zigzag instability in the ground state of ultracold dipolar bosons, as a function of the strength of the transverse confinement. We first analyse the linear-zigzag instability in the classical regime, and then use our results to develop a multi-mode Bose-Hubbard model for the system. We then develop several numerical methods, to determine the ground state.
Adiabatic Quantum Search in Open Systems.
Wild, Dominik S; Gopalakrishnan, Sarang; Knap, Michael; Yao, Norman Y; Lukin, Mikhail D
2016-10-07
Adiabatic quantum algorithms represent a promising approach to universal quantum computation. In isolated systems, a key limitation to such algorithms is the presence of avoided level crossings, where gaps become extremely small. In open quantum systems, the fundamental robustness of adiabatic algorithms remains unresolved. Here, we study the dynamics near an avoided level crossing associated with the adiabatic quantum search algorithm, when the system is coupled to a generic environment. At zero temperature, we find that the algorithm remains scalable provided the noise spectral density of the environment decays sufficiently fast at low frequencies. By contrast, higher order scattering processes render the algorithm inefficient at any finite temperature regardless of the spectral density, implying that no quantum speedup can be achieved. Extensions and implications for other adiabatic quantum algorithms will be discussed.
Tailoring superradiance to design artificial quantum systems
Longo, Paolo; Keitel, Christoph H.; Evers, Jörg
2016-03-01
Cooperative phenomena arising due to the coupling of individual atoms via the radiation field are a cornerstone of modern quantum and optical physics. Recent experiments on x-ray quantum optics added a new twist to this line of research by exploiting superradiance in order to construct artificial quantum systems. However, so far, systematic approaches to deliberately design superradiance properties are lacking, impeding the desired implementation of more advanced quantum optical schemes. Here, we develop an analytical framework for the engineering of single-photon superradiance in extended media applicable across the entire electromagnetic spectrum, and show how it can be used to tailor the properties of an artificial quantum system. This “reverse engineering” of superradiance not only provides an avenue towards non-linear and quantum mechanical phenomena at x-ray energies, but also leads to a unified view on and a better understanding of superradiance across different physical systems.
Tailoring superradiance to design artificial quantum systems.
Longo, Paolo; Keitel, Christoph H; Evers, Jörg
2016-03-24
Cooperative phenomena arising due to the coupling of individual atoms via the radiation field are a cornerstone of modern quantum and optical physics. Recent experiments on x-ray quantum optics added a new twist to this line of research by exploiting superradiance in order to construct artificial quantum systems. However, so far, systematic approaches to deliberately design superradiance properties are lacking, impeding the desired implementation of more advanced quantum optical schemes. Here, we develop an analytical framework for the engineering of single-photon superradiance in extended media applicable across the entire electromagnetic spectrum, and show how it can be used to tailor the properties of an artificial quantum system. This "reverse engineering" of superradiance not only provides an avenue towards non-linear and quantum mechanical phenomena at x-ray energies, but also leads to a unified view on and a better understanding of superradiance across different physical systems.
Adiabatic Quantum Search in Open Systems
Wild, Dominik S.; Gopalakrishnan, Sarang; Knap, Michael; Yao, Norman Y.; Lukin, Mikhail D.
2016-10-01
Adiabatic quantum algorithms represent a promising approach to universal quantum computation. In isolated systems, a key limitation to such algorithms is the presence of avoided level crossings, where gaps become extremely small. In open quantum systems, the fundamental robustness of adiabatic algorithms remains unresolved. Here, we study the dynamics near an avoided level crossing associated with the adiabatic quantum search algorithm, when the system is coupled to a generic environment. At zero temperature, we find that the algorithm remains scalable provided the noise spectral density of the environment decays sufficiently fast at low frequencies. By contrast, higher order scattering processes render the algorithm inefficient at any finite temperature regardless of the spectral density, implying that no quantum speedup can be achieved. Extensions and implications for other adiabatic quantum algorithms will be discussed.
Linear response theory for quantum open systems
Wei, J. H.; Yan, YiJing
2011-01-01
Basing on the theory of Feynman's influence functional and its hierarchical equations of motion, we develop a linear response theory for quantum open systems. Our theory provides an effective way to calculate dynamical observables of a quantum open system at its steady-state, which can be applied to various fields of non-equilibrium condensed matter physics.
BANDWIDTH OF QUANTUM OPTICAL COMMUNICATION SYSTEM
Directory of Open Access Journals (Sweden)
I. R. Gulakov
2012-01-01
Full Text Available Impact of registered optical radiation intensity, overvoltage, dimensions of photosensitive surface, structure of p-n junction and avalanche photodetectors dead time operating in the photon counting mode on quantum optical system capacity has been carried out in this investigation. As a result, the quantum optical system maximum capacity of 81 kbit/s has been obtained.
Advances in InGaAs/InP single-photon detector systems for quantum communication
Zhang, Jun; Zbinden, Hugo; Pan, Jian-Wei
2015-01-01
Single-photon detectors (SPDs) are the most sensitive instruments for light detection. In the near-infrared range, SPDs based on III-V compound semiconductor avalanche photodiodes have been extensively used during the past two decades for diverse applications due to their advantages in practicality including small size, low cost and easy operation. In the past decade, the rapid developments and increasing demands in quantum information science have served as key drivers to improve the device performance of single-photon avalanche diodes and to invent new avalanche quenching techniques. This Review aims to introduce the technology advances of InGaAs/InP single-photon detector systems in the telecom wavelengths and the relevant quantum communication applications, and particularly to highlight recent emerging techniques such as high-frequency gating at GHz rates and free-running operation using negative-feedback avalanche diodes. Future perspectives of both the devices and quenching techniques are summarized.
Quantum information theory with Gaussian systems
Energy Technology Data Exchange (ETDEWEB)
Krueger, O.
2006-04-06
This thesis applies ideas and concepts from quantum information theory to systems of continuous-variables such as the quantum harmonic oscillator. The focus is on three topics: the cloning of coherent states, Gaussian quantum cellular automata and Gaussian private channels. Cloning was investigated both for finite-dimensional and for continuous-variable systems. We construct a private quantum channel for the sequential encryption of coherent states with a classical key, where the key elements have finite precision. For the case of independent one-mode input states, we explicitly estimate this precision, i.e. the number of key bits needed per input state, in terms of these parameters. (orig.)
Classical Equations for Quantum Systems
Gell-Mann, Murray; Gell-Mann, Murray; Hartle, James B.
1993-01-01
The origin of the phenomenological deterministic laws that approximately govern the quasiclassical domain of familiar experience is considered in the context of the quantum mechanics of closed systems such as the universe as a whole. We investigate the requirements for coarse grainings to yield decoherent sets of histories that are quasiclassical, i.e. such that the individual histories obey, with high probability, effective classical equations of motion interrupted continually by small fluctuations and occasionally by large ones. We discuss these requirements generally but study them specifically for coarse grainings of the type that follows a distinguished subset of a complete set of variables while ignoring the rest. More coarse graining is needed to achieve decoherence than would be suggested by naive arguments based on the uncertainty principle. Even coarser graining is required in the distinguished variables for them to have the necessary inertia to approach classical predictability in the presence of t...
Coherent Dynamics of Complex Quantum Systems
Akulin, Vladimir M
2006-01-01
A large number of modern problems in physics, chemistry, and quantum electronics require a consideration of population dynamics in complex multilevel quantum systems. The purpose of this book is to provide a systematic treatment of these questions and to present a number of exactly solvable problems. It considers the different dynamical problems frequently encountered in different areas of physics from the same perspective, based mainly on the fundamental ideas of group theory and on the idea of ensemble average. Also treated are concepts of complete quantum control and correction of decoherence induced errors that are complementary to the idea of ensemble average. "Coherent Dynamics of Complex Quantum Systems" is aimed at senior-level undergraduate students in the areas of Atomic, Molecular, and Laser Physics, Physical Chemistry, Quantum Optics and Quantum Informatics. It should help them put particular problems in these fields into a broader scientific context and thereby take advantage of the well-elabora...
Quantum Dynamics of Nonlinear Cavity Systems
Nation, Paul D.
2010-01-01
We investigate the quantum dynamics of three different configurations of nonlinear cavity systems. To begin, we carry out a quantum analysis of a dc superconducting quantum interference device (SQUID) mechanical displacement detector comprised of a SQUID with a mechanically compliant loop segment. The SQUID is approximated by a nonlinear current-dependent inductor, inducing a flux tunable nonlinear Duffing term in the cavity equation of motion. Expressions are derived for the detector signal ...
Quantum equilibria for macroscopic systems
Energy Technology Data Exchange (ETDEWEB)
Grib, A [Department of Theoretical Physics and Astronomy, Russian State Pedagogical University, St. Petersburg (Russian Federation); Khrennikov, A [Centre for Mathematical Modelling in Physics and Cognitive Sciences Vaexjoe University (Sweden); Parfionov, G [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation); Starkov, K [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation)
2006-06-30
Nash equilibria are found for some quantum games with particles with spin-1/2 for which two spin projections on different directions in space are measured. Examples of macroscopic games with the same equilibria are given. Mixed strategies for participants of these games are calculated using probability amplitudes according to the rules of quantum mechanics in spite of the macroscopic nature of the game and absence of Planck's constant. A possible role of quantum logical lattices for the existence of macroscopic quantum equilibria is discussed. Some examples for spin-1 cases are also considered.
Non-perturbative description of quantum systems
Feranchuk, Ilya; Le, Van-Hoang; Ulyanenkov, Alexander
2015-01-01
This book introduces systematically the operator method for the solution of the Schrödinger equation. This method permits to describe the states of quantum systems in the entire range of parameters of Hamiltonian with a predefined accuracy. The operator method is unique compared with other non-perturbative methods due to its ability to deliver in zeroth approximation the uniformly suitable estimate for both ground and excited states of quantum system. The method has been generalized for the application to quantum statistics and quantum field theory. In this book, the numerous applications of operator method for various physical systems are demonstrated. Simple models are used to illustrate the basic principles of the method which are further used for the solution of complex problems of quantum theory for many-particle systems. The results obtained are supplemented by numerical calculations, presented as tables and figures.
Simulation of n-qubit quantum systems. V. Quantum measurements
Radtke, T.; Fritzsche, S.
2010-02-01
The FEYNMAN program has been developed during the last years to support case studies on the dynamics and entanglement of n-qubit quantum registers. Apart from basic transformations and (gate) operations, it currently supports a good number of separability criteria and entanglement measures, quantum channels as well as the parametrizations of various frequently applied objects in quantum information theory, such as (pure and mixed) quantum states, hermitian and unitary matrices or classical probability distributions. With the present update of the FEYNMAN program, we provide a simple access to (the simulation of) quantum measurements. This includes not only the widely-applied projective measurements upon the eigenspaces of some given operator but also single-qubit measurements in various pre- and user-defined bases as well as the support for two-qubit Bell measurements. In addition, we help perform generalized and POVM measurements. Knowing the importance of measurements for many quantum information protocols, e.g., one-way computing, we hope that this update makes the FEYNMAN code an attractive and versatile tool for both, research and education. New version program summaryProgram title: FEYNMAN Catalogue identifier: ADWE_v5_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWE_v5_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 27 210 No. of bytes in distributed program, including test data, etc.: 1 960 471 Distribution format: tar.gz Programming language: Maple 12 Computer: Any computer with Maple software installed Operating system: Any system that supports Maple; the program has been tested under Microsoft Windows XP and Linux Classification: 4.15 Catalogue identifier of previous version: ADWE_v4_0 Journal reference of previous version: Comput. Phys. Commun
System size dependence of nuclear modification and azimuthal anisotropy of jet quenching
De, Somnath
2011-01-01
We investigate the system size dependence of jet-quenching by analyzing transverse momentum spectra of neutral pions in Au+Au and Cu+Cu collisions at $\\sqrt{s_{\\textrm{NN}}}$ =200 GeV for different centralities. The fast partons are assumed to lose energy by radiating gluons as they traverse the plasma and undergo multiple collisions. The energy loss per collision, $\\epsilon$, is taken as proportional $E$ (where $E$ is the energy of the parton), proportional to $\\sqrt{E}$, or a constant depending on whether the formation time of the gluon is less than the mean path, greater than the mean free path but less than the path length, or greater than the path length of the partons, respectively. NLO pQCD is used to evaluate pion production by modifying the fragmentation function to account for the energy loss. We reproduce the nuclear modification factor $R_\\textrm{AA}$ by treating $\\epsilon$ as the only free parameter, depending on the centrality and the mechanism of energy loss. These values are seen to provide nu...
Charifoulline, Z; Denz, R; Siemko, A; Steckert, J
2012-01-01
The interconnections between the LHC main magnets are made of soldered joints (splices) of two superconducting cables stabilized by a copper bus-bar. After the 2008 LHC incident, caused by a defective interconnection, a new layer of high resolution magnet circuit quench protection (nQPS) has been developed and integrated with the existing systems. It allowed mapping of the resistances of all superconducting splices during the 2009 commissioning campaign. Since April 2010, when the LHC was successfully restarted at 3.5 TeV, every bus bar interconnection is constantly monitored by the nQPS electronics. The acquired data are saved to the LHC Logging Database. The paper will briefly describe the data analysis method and will present the results from the two years of resistance measurements. Although no splice was found with resistance higher than 3.3 n and no significant degradation in time was observed so far, the monitoring of splices will stay active till the end of LHC 4 TeV run. The detected outliers wil...
Collapse and Revival in Holographic Quenches
da Silva, Emilia; Mas, Javier; Serantes, Alexandre
2014-01-01
We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.
Collapse and revival in holographic quenches
da Silva, Emilia; Lopez, Esperanza; Mas, Javier; Serantes, Alexandre
2015-04-01
We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.
Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems
Gogolin, Christian; Eisert, Jens
2016-05-01
We review selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics. We cover topics such as equilibration and thermalisation in pure state statistical mechanics, the eigenstate thermalisation hypothesis, the equivalence of ensembles, non-equilibration dynamics following global and local quenches as well as ramps. We also address initial state independence, absence of thermalisation, and many-body localisation. We elucidate the role played by key concepts for these phenomena, such as Lieb-Robinson bounds, entanglement growth, typicality arguments, quantum maximum entropy principles and the generalised Gibbs ensembles, and quantum (non-)integrability. We put emphasis on rigorous approaches and present the most important results in a unified language.
Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems.
Gogolin, Christian; Eisert, Jens
2016-05-01
We review selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics. We cover topics such as equilibration and thermalisation in pure state statistical mechanics, the eigenstate thermalisation hypothesis, the equivalence of ensembles, non-equilibration dynamics following global and local quenches as well as ramps. We also address initial state independence, absence of thermalisation, and many-body localisation. We elucidate the role played by key concepts for these phenomena, such as Lieb-Robinson bounds, entanglement growth, typicality arguments, quantum maximum entropy principles and the generalised Gibbs ensembles, and quantum (non-)integrability. We put emphasis on rigorous approaches and present the most important results in a unified language.
Limpens, R.; Gregorkiewicz, T.
2013-01-01
The percentage of dark silicon nanocrystals, i.e., the nanocrystals that are not able to radiatively recombine after absorption of a photon, is investigated by combining measurements of external and internal quantum efficiencies. The study is conducted on samples prepared by co-sputtering and subseq
O2(a1Δ) Quenching In The O/O2/O3 System
Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.
2010-10-01
The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ)+O+M→2O2+M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O2(a1Δ) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ) quenching were followed by observing the 1268 nm fluorescence of the O2a1Δ-X3∑ transition. Fast quenching of O2(a1Δ) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.
Limit cycles in quantum systems
Energy Technology Data Exchange (ETDEWEB)
Niemann, Patrick
2015-04-27
In this thesis we investigate Limit Cycles in Quantum Systems. Limit cycles are a renormalization group (RG) topology. When degrees of freedom are integrated out, the coupling constants flow periodically in a closed curve. The presence of limit cycles is restricted by the necessary condition of discrete scale invariance. A signature of discrete scale invariance and limit cycles is log-periodic behavior. The first part of this thesis is concerned with the study of limit cycles with the similarity renormalization group (SRG). Limit cycles are mainly investigated within conventional renormalization group frameworks, where degrees of freedom, which are larger than a given cutoff, are integrated out. In contrast, in the SRG potentials are unitarily transformed and thereby obtain a band-diagonal structure. The width of the band structure can be regarded as an effective cutoff. We investigate the appearance of limit cycles in the SRG evolution. Our aim is to extract signatures as well as the scaling factor of the limit cycle. We consider the 1/R{sup 2}-potential in a two-body system and a three-body system with large scattering lengths. Both systems display a limit cycle. Besides the frequently used kinetic energy generator we apply the exponential and the inverse generator. In the second part of this thesis, Limit Cycles at Finite Density, we examine the pole structure of the scattering amplitude for distinguishable fermions at zero temperature in the medium. Unequal masses and a filled Fermi sphere for each fermion species are considered. We focus on negative scattering lengths and the unitary limit. The properties of the three-body spectrum in the medium and implications for the phase structure of ultracold Fermi gases are discussed.
Lippert, Lisa G; Hallock, Jeffrey T; Dadosh, Tali; Diroll, Benjamin T; Murray, Christopher B; Goldman, Yale E
2016-03-16
We developed methods to solubilize, coat, and functionalize with NeutrAvidin elongated semiconductor nanocrystals (quantum nanorods, QRs) for use in single molecule polarized fluorescence microscopy. Three different ligands were compared with regard to efficacy for attaching NeutrAvidin using the "zero-length cross-linker" 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). Biotin-4-fluorescene (B4F), a fluorophore that is quenched when bound to avidin proteins, was used to quantify biotin binding activity of the NeutrAvidin coated QRs and biotin binding activity of commercially available streptavidin coated quantum dots (QDs). All three coating methods produced QRs with NeutrAvidin coating density comparable to the streptavidin coating density of the commercially available quantum dots (QDs) in the B4F assay. One type of QD available from the supplier (ITK QDs) exhibited ∼5-fold higher streptavidin surface density compared to our QRs, whereas the other type of QD (PEG QDs) had 5-fold lower density. The number of streptavidins per QD increased from ∼7 streptavidin tetramers for the smallest QDs emitting fluorescence at 525 nm (QD525) to ∼20 tetramers for larger, longer wavelength QDs (QD655, QD705, and QD800). QRs coated with NeutrAvidin using mercaptoundecanoicacid (MUA) and QDs coated with streptavidin bound to biotinylated cytoplasmic dynein in single molecule TIRF microscopy assays, whereas Poly(maleic anhydride-alt-1-ocatdecene) (PMAOD) or glutathione (GSH) QRs did not bind cytoplasmic dynein. The coating methods require optimization of conditions and concentrations to balance between substantial NeutrAvidin binding vs tendency of QRs to aggregate and degrade over time.
Energy Technology Data Exchange (ETDEWEB)
Huang Yabei; Liu Benzhi; Yu Zhang [School of Chemistry and Materials Science, Huaibei Coal Normal College, Huaibei 235000 (China); Zi Yanqin, E-mail: ziyanqin@163.co [School of Chemistry and Materials Science, Huaibei Coal Normal College, Huaibei 235000 (China)
2010-03-15
Prulifloxacin is a kind of new oral taking antibiotic of fluoroquinolone. Conjugation reaction of prulifloxacin with trypsin in Britton-Robinson buffer solution of pH 7.96 was analyzed by UV-vis spectrophotometry and fluorescence spectrometry. The intrinsic fluorescence of trypsin was strongly quenched by prulifloxacin. This effect was rationalized in terms of a static quenching procedure. The binding parameters have been evaluated by fluorescence quenching methods. Negative values DELTAG{sup 0} for the formation of prulifloxacin-trypsin complex implied that both hydrogen bonds and hydrophobic interactions might play a significant role in prulifloxacin binding to trypsin. The binding distance deduced from the efficiency of energy transfer was 0.84 nm for prulifloxacin-trypsin. Furthermore, association constants and binding mechanism were successfully derived from the fluorescence spectra. UV-vis detections supported a change in the secondary structure of proteins caused by the interaction of prulifloxacin with trypsin.
The fluorescence quenching and resonance Rayleigh scattering enhancement of ET-CPM system
Institute of Scientific and Technical Information of China (English)
YANG JiDong; ZHOU Shang
2009-01-01
In pH 4.4 BR buffer medium, erythrosine (ET) and Chlorphensmine Maleate (CPM) could form ion-as-sociation complex, which led to the quenching of fluorescence and synchronous fluorescence, and the significant enhancement of resonance Rayleigh scattering(RRS) of erythrosine. Furthermore, a new RRS spectrum would appear, and the maximum RRS wavelength was located at about 578 rim. The quenched fluorescence and enhanced RRS intensity was directly proportional to the concentration of CPM in the ranges of 0.24-8.0 μg/mL, and 0.008-3.6 μg/mL, respectively. The method has been ap-plied to determine CPM in urine samples with satisfactory results. The mechanisms of the RRS en-hancement and fluorescence quenching were discussed as well.
Robust quantum correlations in out-of-equilibrium matter-light systems
Acevedo, O. L.; Quiroga, L.; Rodríguez, F. J.; Johnson, N. F.
2015-09-01
High precision macroscopic quantum control in interacting light-matter systems remains a significant goal toward novel information processing and ultra-precise metrology. We show that the out-of-equilibrium behavior of a paradigmatic light-matter system (Dicke model) reveals two successive stages of enhanced quantum correlations beyond the traditional schemes of near-adiabatic and sudden quenches. The first stage features magnification of matter-only and light-only entanglement and squeezing due to effective nonlinear self-interactions. The second stage results from a highly entangled light-matter state, with enhanced superradiance and signatures of chaotic and highly quantum states. We show that these new effects scale up consistently with matter system size, and are reliable even in dissipative environments.
Energy Technology Data Exchange (ETDEWEB)
Yang Benhui; Stancil, P. C. [Department of Physics and Astronomy and the Center for Simulational Physics, The University of Georgia, Athens, GA 30602 (United States); Balakrishnan, N. [Department of Chemistry, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Forrey, R. C. [Department of Physics, Penn State University, Berks Campus, Reading, PA 19610 (United States); Bowman, J. M. [Department of Chemistry, Emory University, Atlanta, GA 30322 (United States)
2013-07-01
New quantum scattering calculations for rotational deexcitation transitions of CO induced by H collisions using two CO-H potential energy surfaces (PESs) from Shepler et al. are reported. State-to-state rate coefficients are computed for temperatures ranging from 1 to 3000 K for CO(v = 0, j) deexcitation from j = 1 to 5 to all lower j' levels, with j being the rotational quantum number. Different resonance structures in the cross sections are attributed to the differences in the anisotropy and the long-range van der Waals well depths of the two PESs. These differences affect rate coefficients at low temperatures and give an indication of the uncertainty of the results. Significant discrepancies are found between the current rate coefficients and previous results computed using earlier potentials, while the current results satisfy expected propensity rules. Astrophysical applications to modeling far infrared and submillimeter observations are briefly discussed.
Quantum Simulation for Open-System Dynamics
Wang, Dong-Sheng; de Oliveira, Marcos Cesar; Berry, Dominic; Sanders, Barry
2013-03-01
Simulations are essential for predicting and explaining properties of physical and mathematical systems yet so far have been restricted to classical and closed quantum systems. Although forays have been made into open-system quantum simulation, the strict algorithmic aspect has not been explored yet is necessary to account fully for resource consumption to deliver bounded-error answers to computational questions. An open-system quantum simulator would encompass classical and closed-system simulation and also solve outstanding problems concerning, e.g. dynamical phase transitions in non-equilibrium systems, establishing long-range order via dissipation, verifying the simulatability of open-system dynamics on a quantum Turing machine. We construct an efficient autonomous algorithm for designing an efficient quantum circuit to simulate many-body open-system dynamics described by a local Hamiltonian plus decoherence due to separate baths for each particle. The execution time and number of gates for the quantum simulator both scale polynomially with the system size. DSW funded by USARO. MCO funded by AITF and Brazilian agencies CNPq and FAPESP through Instituto Nacional de Ciencia e Tecnologia-Informacao Quantica (INCT-IQ). DWB funded by ARC Future Fellowship (FT100100761). BCS funded by AITF, CIFAR, NSERC and USARO.
Institute of Scientific and Technical Information of China (English)
Martin; M.F.Choi
2010-01-01
The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10~(-7)-1.0×10~(-3) mol L~(-1) and a detection limit 1.0×10~(-7) mol L~(-1) of catechol were obtained.o-Quinone intermediate produ...
Workshop on quantum stochastic differential equations for the quantum simulation of physical systems
2016-09-22
SECURITY CLASSIFICATION OF: This is a report on the “Workshop on quantum stochastic differential equations for the quantum simulation of physical ...mathematical tools to the quantum simulation of physical systems of interest to the Army. There were participants from US Government agencies, industry, and... quantum stochastic differential equations for the quantum simulation of physical systems Report Title This is a report on the “Workshop on quantum
Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems
Directory of Open Access Journals (Sweden)
P. Marini
2016-05-01
Full Text Available We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4π detector array to the forward angle VAMOS magnetic spectrometer, allowed to reconstruct the mass, charge and excitation energy of the decaying hot projectile-like sources. By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosons and fermions could be correlated to the excitation energy of the reconstructed system. The results are consistent with the production of dilute mixed systems of bosons and fermions, where bosons experience higher phase-space and energy density as compared to the surrounding fermionic gas. Our findings recall phenomena observed in the study of Bose condensates and Fermi gases in atomic traps despite the different scales.
de Paor, A. M.
Hide (Nonlinear Processes in Geophysics, 1998) has produced a new mathematical model of a self-exciting homopolar dynamo driving a series- wound motor, as a continuing contribution to the theory of the geomagnetic field. By a process of exact perturbation analysis, followed by combination and partial solution of differential equations, the complete nonlinear quenching of current fluctuations reported by Hide in the case that a parameter ɛ has the value 1 is proved via the Popov theorem from feedback system stability theory.
Quantum entanglement in condensed matter systems
Energy Technology Data Exchange (ETDEWEB)
Laflorencie, Nicolas, E-mail: laflo@irsamc.ups-tlse.fr
2016-08-03
This review focuses on the field of quantum entanglement applied to condensed matter physics systems with strong correlations, a domain which has rapidly grown over the last decade. By tracing out part of the degrees of freedom of correlated quantum systems, useful and non-trivial information can be obtained through the study of the reduced density matrix, whose eigenvalue spectrum (the entanglement spectrum) and the associated Rényi entropies are now well recognized to contain key features. In particular, the celebrated area law for the entanglement entropy of ground-states will be discussed from the perspective of its subleading corrections which encode universal details of various quantum states of matter, e.g. symmetry breaking states or topological order. Going beyond entropies, the study of the low-lying part of the entanglement spectrum also allows to diagnose topological properties or give a direct access to the excitation spectrum of the edges, and may also raise significant questions about the underlying entanglement Hamiltonian. All these powerful tools can be further applied to shed some light on disordered quantum systems where impurity/disorder can conspire with quantum fluctuations to induce non-trivial effects. Disordered quantum spin systems, the Kondo effect, or the many-body localization problem, which have all been successfully (re)visited through the prism of quantum entanglement, will be discussed in detail. Finally, the issue of experimental access to entanglement measurement will be addressed, together with its most recent developments.
Quantum entanglement in condensed matter systems
Laflorencie, Nicolas
2016-08-01
This review focuses on the field of quantum entanglement applied to condensed matter physics systems with strong correlations, a domain which has rapidly grown over the last decade. By tracing out part of the degrees of freedom of correlated quantum systems, useful and non-trivial information can be obtained through the study of the reduced density matrix, whose eigenvalue spectrum (the entanglement spectrum) and the associated Rényi entropies are now well recognized to contain key features. In particular, the celebrated area law for the entanglement entropy of ground-states will be discussed from the perspective of its subleading corrections which encode universal details of various quantum states of matter, e.g. symmetry breaking states or topological order. Going beyond entropies, the study of the low-lying part of the entanglement spectrum also allows to diagnose topological properties or give a direct access to the excitation spectrum of the edges, and may also raise significant questions about the underlying entanglement Hamiltonian. All these powerful tools can be further applied to shed some light on disordered quantum systems where impurity/disorder can conspire with quantum fluctuations to induce non-trivial effects. Disordered quantum spin systems, the Kondo effect, or the many-body localization problem, which have all been successfully (re)visited through the prism of quantum entanglement, will be discussed in detail. Finally, the issue of experimental access to entanglement measurement will be addressed, together with its most recent developments.
An Application of Quantum Finite Automata to Interactive Proof Systems
Nishimura, H; Nishimura, Harumichi; Yamakami, Tomoyuki
2004-01-01
Quantum finite automata have been studied intensively since their introduction in late 1990s as a natural model of a quantum computer with finite-dimensional quantum memory space. This paper seeks their direct application to interactive proof systems in which a mighty quantum prover communicates with a quantum-automaton verifier through a common communication cell. Our quantum interactive proof systems are juxtaposed to Dwork-Stockmeyer's classical interactive proof systems whose verifiers are two-way probabilistic automata. We demonstrate strengths and weaknesses of our systems and further study how various restrictions on the behaviors of quantum-automaton verifiers affect the power of quantum interactive proof systems.
Emergent "Quantum" Theory in Complex Adaptive Systems.
Minic, Djordje; Pajevic, Sinisa
2016-04-30
Motivated by the question of stability, in this letter we argue that an effective quantum-like theory can emerge in complex adaptive systems. In the concrete example of stochastic Lotka-Volterra dynamics, the relevant effective "Planck constant" associated with such emergent "quantum" theory has the dimensions of the square of the unit of time. Such an emergent quantum-like theory has inherently non-classical stability as well as coherent properties that are not, in principle, endangered by thermal fluctuations and therefore might be of crucial importance in complex adaptive systems.
Open quantum systems and error correction
Shabani Barzegar, Alireza
Quantum effects can be harnessed to manipulate information in a desired way. Quantum systems which are designed for this purpose are suffering from harming interaction with their surrounding environment or inaccuracy in control forces. Engineering different methods to combat errors in quantum devices are highly demanding. In this thesis, I focus on realistic formulations of quantum error correction methods. A realistic formulation is the one that incorporates experimental challenges. This thesis is presented in two sections of open quantum system and quantum error correction. Chapters 2 and 3 cover the material on open quantum system theory. It is essential to first study a noise process then to contemplate methods to cancel its effect. In the second chapter, I present the non-completely positive formulation of quantum maps. Most of these results are published in [Shabani and Lidar, 2009b,a], except a subsection on geometric characterization of positivity domain of a quantum map. The real-time formulation of the dynamics is the topic of the third chapter. After introducing the concept of Markovian regime, A new post-Markovian quantum master equation is derived, published in [Shabani and Lidar, 2005a]. The section of quantum error correction is presented in three chapters of 4, 5, 6 and 7. In chapter 4, we introduce a generalized theory of decoherence-free subspaces and subsystems (DFSs), which do not require accurate initialization (published in [Shabani and Lidar, 2005b]). In Chapter 5, we present a semidefinite program optimization approach to quantum error correction that yields codes and recovery procedures that are robust against significant variations in the noise channel. Our approach allows us to optimize the encoding, recovery, or both, and is amenable to approximations that significantly improve computational cost while retaining fidelity (see [Kosut et al., 2008] for a published version). Chapter 6 is devoted to a theory of quantum error correction (QEC
Quantum Hysteresis in Coupled Light–Matter Systems
Directory of Open Access Journals (Sweden)
Fernando J. Gómez-Ruiz
2016-09-01
Full Text Available We investigate the non-equilibrium quantum dynamics of a canonical light–matter system—namely, the Dicke model—when the light–matter interaction is ramped up and down through a cycle across the quantum phase transition. Our calculations reveal a rich set of dynamical behaviors determined by the cycle times, ranging from the slow, near adiabatic regime through to the fast, sudden quench regime. As the cycle time decreases, we uncover a crossover from an oscillatory exchange of quantum information between light and matter that approaches a reversible adiabatic process, to a dispersive regime that generates large values of light–matter entanglement. The phenomena uncovered in this work have implications in quantum control, quantum interferometry, as well as in quantum information theory.
Barbante, Gregory J; Kebede, Noah; Hindson, Christopher M; Doeven, Egan H; Zammit, Elizabeth M; Hanson, Graeme R; Hogan, Conor F; Francis, Paul S
2014-10-20
We demonstrate a new approach to manipulate the selective emission in mixed electrogenerated chemiluminescence (ECL) systems, where subtle changes in co-reactant properties are exploited to control the relative electron-transfer processes of excitation and quenching. Two closely related tertiary-amine co-reactants, tri-n-propylamine and N,N-diisopropylethylamine, generate remarkably different emission profiles: one provides distinct green and red ECL from [Ir(ppy)3] (ppy=2-phenylpyridinato-C2,N) and a [Ru(bpy)3](2+) (bpy=2,2'-bipyridine) derivative at different applied potentials, whereas the other generates both emissions simultaneously across a wide potential range. These phenomena can be rationalized through the relative exergonicities of electron-transfer quenching of the excited states, in conjunction with the change in concentration of the quenchers over the applied potential range.
Wittenburg, Kay
1994-06-01
The beam-loss-monitors (BLMs) in the HERA-proton-ring (HERAp) must fulfill the following requirements: They have to measure losses sensitive and fast enough to prevent the superconducting magnets from beam loss induced quenching; the dynamic range of the monitors must exceed several decades in order to measure losses during beam lifetimes of hundreds of hours as well as the much stronger losses that may quench superconducting magnets; they have to be insensitive to the synchrotron radiation of the adjacent electron-ring (HERAe); and their radiation hardness must allow a monitor-lifetime of a few years of HERA operation. These requirements are well satisfied by the HERAp-BLM-System.
Quantum liquids in correlated systems
Kusminskiy, Silvia Viola
Particular aspects of two different relevant systems in contemporary Condensed Matter Physics are studied: heavy fermion materials and the newly discovered graphene (an atom thick layer of graphite), specifically its bilayer. On one hand, the physics of heavy fermion materials under strong external magnetic fields is analyzed from a mean field point of view. The evolution of the heavy fermion ground state under the application of a magnetic field is investigated. A richer version of the usual hybridization mean field theory is presented, which allows for hybridization in both the singlet and triplet channels and incorporates a self-consistent Weiss field. It is shown that for a magnetic field strength B⋆, at a filling-dependent fraction of the zero-field hybridization gap, the spin up quasiparticle band becomes fully polarized---an event marked by a sudden jump in the magnetic susceptibility. The system exhibits a kind of quantum rigidity in which the susceptibility (and several other physical observables) are insensitive to further increases in field strength. This behavior ends abruptly with the collapse of the hybridization order parameter in a first-order transition to the normal metallic state. It is argued that the feature at B⋆ corresponds to the "metamagnetic transition" in YbRh2Si2. These results are in good agreement with recent experimental measurements. For the case of the graphene bilayer, the effect of electron-electron interactions on the properties of a graphene bilayer is studied within the Hartree-Fock-Thomas-Fermi theory. It is found that the electronic compressibility is rather different from those of either the two-dimensional electron gas or ordinary semiconductors. An inherent competition between the contributions coming from intra-band exchange interactions and inter-band interactions leads to a non-monotonic behavior of the compressibility as a function of carrier density. Also analyzed is the effect of the interactions on the
Excess entropy production in quantum system: Quantum master equation approach
Nakajima, Satoshi; Tokura, Yasuhiro
2016-01-01
For open systems described by the quantum master equation (QME), we investigate the excess entropy production under quasistatic operations between nonequilibrium steady states. The average entropy production is composed of the time integral of the instantaneous steady entropy production rate and the excess entropy production. We define average entropy production rate using the average energy and particle currents, which are calculated by using the full counting statistics with QME. The excess...
Porcel, Rosa; Redondo-Gómez, Susana; Mateos-Naranjo, Enrique; Aroca, Ricardo; Garcia, Rosalva; Ruiz-Lozano, Juan Manuel
2015-08-01
Rice is the most important food crop in the world and is a primary source of food for more than half of the world population. However, salinity is considered the most common abiotic stress reducing its productivity. Soil salinity inhibits photosynthetic processes, which can induce an over-reduction of the reaction centres in photosystem II (PSII), damaging the photosynthetic machinery. The arbuscular mycorrhizal (AM) symbiosis may improve host plant tolerance to salinity, but it is not clear how the AM symbiosis affects the plant photosynthetic capacity, particularly the efficiency of PSII. This study aimed at determining the influence of the AM symbiosis on the performance of PSII in rice plants subjected to salinity. Photosynthetic activity, plant gas-exchange parameters, accumulation of photosynthetic pigments and rubisco activity and gene expression were also measured in order to analyse comprehensively the response of the photosynthetic processes to AM symbiosis and salinity. Results showed that the AM symbiosis enhanced the actual quantum yield of PSII photochemistry and reduced the quantum yield of non-photochemical quenching in rice plants subjected to salinity. AM rice plants maintained higher net photosynthetic rate, stomatal conductance and transpiration rate than nonAM plants. Thus, we propose that AM rice plants had a higher photochemical efficiency for CO2 fixation and solar energy utilization and this increases plant salt tolerance by preventing the injury to the photosystems reaction centres and by allowing a better utilization of light energy in photochemical processes. All these processes translated into higher photosynthetic and rubisco activities in AM rice plants and improved plant biomass production under salinity.
Holographic Quenches with a Gap
da Silva, Emilia; Mas, Javier; Serantes, Alexandre
2016-01-01
In order to holographically model quenches with a gapped final hamiltonian, we consider a gravity-scalar theory in anti-de Sitter space with an infrared hard wall. We allow a time dependent profile for the scalar field at the wall. This induces an energy exchange between bulk and wall and generates an oscillating scalar pulse. We argue that such backgrounds are the counterpart of quantum revivals in the dual field theory. We perform a qualitative comparison with the quench dynamics of the massive Schwinger model, which has been recently analyzed using tensor network techniques. Agreement is found provided the width of the oscillating scalar pulse is inversely linked to the energy density communicated by the quench. We propose this to be a general feature of holographic quenches.
Holographic quenches with a gap
da Silva, Emilia; Lopez, Esperanza; Mas, Javier; Serantes, Alexandre
2016-06-01
In order to holographically model quenches with a gapped final hamiltonian, we consider a gravity-scalar theory in anti-de Sitter space with an infrared hard wall. We allow a time dependent profile for the scalar field at the wall. This induces an energy exchange between bulk and wall and generates an oscillating scalar pulse. We argue that such backgrounds are the counterpart of quantum revivals in the dual field theory. We perform a qualitative comparison with the quench dynamics of the massive Schwinger model, which has been recently analyzed using tensor network techniques. Agreement is found provided the width of the oscillating scalar pulse is inversely linked to the energy density communicated by the quench. We propose this to be a general feature of holographic quenches.
Editorial: Focus on Dynamics and Thermalization in Isolated Quantum Many-Body Systems
Cazalilla, M. A.; Rigol, M.
2010-05-01
understand many-body quantum systems. This focus issue of New Journal Physics brings together both experimentalists and theoreticians working on these problems to provide a comprehensive picture of the state of the field. Focus on Dynamics and Thermalization in Isolated Quantum Many-Body Systems Contents Spin squeezing of high-spin, spatially extended quantum fields Jay D Sau, Sabrina R Leslie, Marvin L Cohen and Dan M Stamper-Kurn Thermodynamic entropy of a many-body energy eigenstate J M Deutsch Ground states and dynamics of population-imbalanced Fermi condensates in one dimension Masaki Tezuka and Masahito Ueda Relaxation dynamics in the gapped XXZ spin-1/2 chain Jorn Mossel and Jean-Sébastien Caux Canonical thermalization Peter Reimann Minimally entangled typical thermal state algorithms E M Stoudenmire and Steven R White Manipulation of the dynamics of many-body systems via quantum control methods Julie Dinerman and Lea F Santos Multimode analysis of non-classical correlations in double-well Bose-Einstein condensates Andrew J Ferris and Matthew J Davis Thermalization in a quasi-one-dimensional ultracold bosonic gas I E Mazets and J Schmiedmayer Two simple systems with cold atoms: quantum chaos tests and non-equilibrium dynamics Cavan Stone, Yassine Ait El Aoud, Vladimir A Yurovsky and Maxim Olshanii On the speed of fluctuations around thermodynamic equilibrium Noah Linden, Sandu Popescu, Anthony J Short and Andreas Winter A quantum central limit theorem for non-equilibrium systems: exact local relaxation of correlated states M Cramer and J Eisert Quantum quench dynamics of the sine-Gordon model in some solvable limits A Iucci and M A Cazalilla Nonequilibrium quantum dynamics of atomic dark solitons A D Martin and J Ruostekoski Quantum quenches in the anisotropic spin-1⁄2 Heisenberg chain: different approaches to many-body dynamics far from equilibrium Peter Barmettler, Matthias Punk, Vladimir Gritsev, Eugene Demler and Ehud Altman Crossover from adiabatic to sudden
Yang, Qiong; Tan, Xuanping; Yang, Jidong
2016-02-01
A sensitive and simple method for the determination of enoxacin (ENX) was developed based on the fluorescence quenching effect of ENX for glutathione (GSH)-capped CdTe quantum dots (QDs). Under optimum conditions, a good linear relationship was obtained from 4.333 × 10(-9) mol⋅L(-1) to 1.4 × 10(-5) mol⋅L(-1) with a correlation coefficient (R) of 0.9987, and the detection limit (3σ/K) was 1.313 × 10(-9) mol⋅L(-1). The corresponding mechanism has been proposed on the basis of electron transfer supported by ultraviolet-visible (UV) light absorption, fluorescence spectroscopy, and the measurement of fluorescence lifetime. The method has been applied to the determination of ENX in pharmaceutical formulations (enoxacin gluconate injections and commercial tablets) with satisfactory results. The proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. Copyright © 2015 John Wiley & Sons, Ltd.
Noise management to achieve superiority in quantum information systems
Nemoto, Kae; Devitt, Simon; Munro, William J.
2017-06-01
Quantum information systems are expected to exhibit superiority compared with their classical counterparts. This superiority arises from the quantum coherences present in these quantum systems, which are obviously absent in classical ones. To exploit such quantum coherences, it is essential to control the phase information in the quantum state. The phase is analogue in nature, rather than binary. This makes quantum information technology fundamentally different from our classical digital information technology. In this paper, we analyse error sources and illustrate how these errors must be managed for the system to achieve the required fidelity and a quantum superiority. This article is part of the themed issue 'Quantum technology for the 21st century'.
Quantum optical properties in plasmonic systems
Ooi, C. H. Raymond
2015-04-01
Plasmonic metallic particle (MP) can affect the optical properties of a quantum system (QS) in a remarkable way. We develop a general quantum nonlinear formalism with exact vectorial description for the scattered photons by the QS. The formalism enables us to study the variations of the dielectric function and photon spectrum of the QS with the particle distance between QS and MP, exciting laser direction, polarization and phase in the presence of surface plasmon resonance (SPR) in the MP. The quantum formalism also serves as a powerful tool for studying the effects of these parameters on the nonclassical properties of the scattered photons. The plasmonic effect of nanoparticles has promising possibilities as it provides a new way for manipulating quantum optical properties of light in nanophotonic systems.
Note on quantum groups and integrable systems
Popolitov, A.
2016-01-01
The free-field formalism for quantum groups [preprint ITEP-M3/94, CRM-2202 hep-th/9409093] provides a special choice of coordinates on a quantum group. In these coordinates the construction of associated integrable system [arXiv:1207.1869] is especially simple. This choice also fits into general framework of cluster varieties [math.AG/0311245]—natural changes in coordinates are cluster mutations.
Toward simulating complex systems with quantum effects
Kenion-Hanrath, Rachel Lynn
Quantum effects like tunneling, coherence, and zero point energy often play a significant role in phenomena on the scales of atoms and molecules. However, the exact quantum treatment of a system scales exponentially with dimensionality, making it impractical for characterizing reaction rates and mechanisms in complex systems. An ongoing effort in the field of theoretical chemistry and physics is extending scalable, classical trajectory-based simulation methods capable of capturing quantum effects to describe dynamic processes in many-body systems; in the work presented here we explore two such techniques. First, we detail an explicit electron, path integral (PI)-based simulation protocol for predicting the rate of electron transfer in condensed-phase transition metal complex systems. Using a PI representation of the transferring electron and a classical representation of the transition metal complex and solvent atoms, we compute the outer sphere free energy barrier and dynamical recrossing factor of the electron transfer rate while accounting for quantum tunneling and zero point energy effects. We are able to achieve this employing only a single set of force field parameters to describe the system rather than parameterizing along the reaction coordinate. Following our success in describing a simple model system, we discuss our next steps in extending our protocol to technologically relevant materials systems. The latter half focuses on the Mixed Quantum-Classical Initial Value Representation (MQC-IVR) of real-time correlation functions, a semiclassical method which has demonstrated its ability to "tune'' between quantum- and classical-limit correlation functions while maintaining dynamic consistency. Specifically, this is achieved through a parameter that determines the quantumness of individual degrees of freedom. Here, we derive a semiclassical correction term for the MQC-IVR to systematically characterize the error introduced by different choices of simulation
Classical Boolean logic gates with quantum systems
Energy Technology Data Exchange (ETDEWEB)
Renaud, N; Joachim, C, E-mail: n-renaud@northwestern.edu [Nanoscience Group and MANA Satellite CEMES/CNRS, 29 rue J Marvig, BP 94347, 31055 Toulouse Cedex (France)
2011-04-15
An analytical method is proposed to implement any classical Boolean function in a small quantum system by taking the advantage of its electronic transport properties. The logical input, {alpha} = {l_brace}{alpha}{sub 1}, ..., {alpha}{sub N}{r_brace}, is used to control well-identified parameters of the Hamiltonian of the system noted H{sub 0}({alpha}). The logical output is encoded in the tunneling current intensity passing through the quantum system when connected to conducting electrodes. It is demonstrated how to implement the six symmetric two-input/one-output Boolean functions in a quantum system. This system can be switched from one logic function to another by changing its structural parameters. The stability of the logic gates is discussed, perturbing the Hamiltonian with noise sources and studying the effect of decoherence.
Open quantum systems far from equilibrium
Schaller, Gernot
2014-01-01
This monograph provides graduate students and also professional researchers aiming to understand the dynamics of open quantum systems with a valuable and self-contained toolbox. Special focus is laid on the link between microscopic models and the resulting open-system dynamics. This includes how to derive the celebrated Lindblad master equation without applying the rotating wave approximation. As typical representatives for non-equilibrium configurations it treats systems coupled to multiple reservoirs (including the description of quantum transport), driven systems, and feedback-controlled quantum systems. Each method is illustrated with easy-to-follow examples from recent research. Exercises and short summaries at the end of every chapter enable the reader to approach the frontiers of current research quickly and make the book useful for quick reference.
Inhomogeneous Thermal Quenches
Sohrabi, Kiyoumars A
2015-01-01
We describe holographic thermal quenches that are inhomogeneous in space. The main characteristic of the quench is to take the system far from its equilibrium configuration. Except special extreme cases, the problem has no analytic solution. Using the numerical holography methods, we study different observables that measure thermalization such as the time evolution of the horizon, two-point Wightman function and entanglement entropy (EE). Having an extra nontrivial spacial direction, allows us to study this peculiar generalization since we categorize the problem based on whether we do the measurements along this special direction or perpendicular to it. Exciting new features appear that are absent in the common computations in the literature, the appearance of negative EE valleys surrounding the positive EE hills and abrupt quenches that occupy the whole space at their universal limit are some of the results of this paper. We have tried to provide physical explanations wherever possible. The physical picture ...
Quantum hacking: attacking practical quantum key distribution systems
Qi, Bing; Fung, Chi-Hang Fred; Zhao, Yi; Ma, Xiongfeng; Tamaki, Kiyoshi; Chen, Christine; Lo, Hoi-Kwong
2007-09-01
Quantum key distribution (QKD) can, in principle, provide unconditional security based on the fundamental laws of physics. Unfortunately, a practical QKD system may contain overlooked imperfections and violate some of the assumptions in a security proof. Here, we report two types of eavesdropping attacks against a practical QKD system. The first one is "time-shift" attack, which is applicable to QKD systems with gated single photon detectors (SPDs). In this attack, the eavesdropper, Eve, exploits the time mismatch between the open windows of the two SPDs. She can acquire a significant amount of information on the final key by simply shifting the quantum signals forwards or backwards in time domain. Our experimental results in [9] with a commercial QKD system demonstrate that, under this attack, the original QKD system is breakable. This is the first experimental demonstration of a feasible attack against a commercial QKD system. This is a surprising result. The second one is "phase-remapping" attack [10]. Here, Eve exploits the fact that a practical phase modulator has a finite response time. In principle, Eve could change the encoded phase value by time-shifting the signal pulse relative to the reference pulse.
Decoherence in Field Theory General Couplings and Slow Quenches
Lombardo, F C; Rivers, R J
2003-01-01
We study the onset of a classical order parameter after a second-order phase transition in quantum field theory. We consider a quantum scalar field theory in which the system-field (long-wavelength modes), interacts with its environment, represented both by a set of scalar fields and by its own short-wavelength modes. We compute the decoherence times for the system-field modes and compare them with the other time scales of the model. We analyze different couplings between the system and the environment for both instantaneous and slow quenches. Within our approximations decoherence is in general a short time event.
Hamiltonian truncation approach to quenches in the Ising field theory
Rakovszky, Tibor; Collura, Mario; Kormos, Márton; Takács, Gábor
2016-01-01
In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1+1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while...
Dynamical Outcomes of Quenching: Reflections on a Conical Intersection
Lehman, Julia H.; Lester, Marsha I.
2014-04-01
This review focuses on experimental studies of the dynamical outcomes following collisional quenching of electronically excited OH A2Î£+ radicals by molecular partners. The experimental observables include the branching between reactive and nonreactive decay channels, kinetic energy release, and quantum state distributions of the products. Complementary theoretical investigations reveal regions of strong nonadiabatic coupling, known as conical intersections, which facilitate the quenching process. The dynamical outcomes observed experimentally are connected to the local forces and geometric properties of the nuclei in the conical intersection region. Dynamical calculations for the benchmark OH-H2 system are in good accord with experimental observations, demonstrating that the outcomes reflect the strong coupling in the conical intersection region as the system evolves from the excited electronic state to quenched products.
Witnessing Quantum Coherence: from solid-state to biological systems
Li, Che-Ming; Chen, Yueh-Nan; Chen, Guang-Yin; Nori, Franco; 10.1038/srep00885
2012-01-01
Quantum coherence is one of the primary non-classical features of quantum systems. While protocols such as the Leggett-Garg inequality (LGI) and quantum tomography can be used to test for the existence of quantum coherence and dynamics in a given system, unambiguously detecting inherent "quantumness" still faces serious obstacles in terms of experimental feasibility and efficiency, particularly in complex systems. Here we introduce two "quantum witnesses" to efficiently verify quantum coherence and dynamics in the time domain, without the expense and burden of non-invasive measurements or full tomographic processes. Using several physical examples, including quantum transport in solid-state nanostructures and in biological organisms, we show that these quantum witnesses are robust and have a much finer resolution in their detection window than the LGI has. These robust quantum indicators may assist in reducing the experimental overhead in unambiguously verifying quantum coherence in complex systems.
Superconducting Quantum Arrays for Broadband RF Systems
Kornev, V.; Sharafiev, A.; Soloviev, I.; Kolotinskiy, N.; Mukhanov, O.
2014-05-01
Superconducting Quantum Arrays (SQAs), homogenous arrays of Superconducting Quantum Cells, are developed for implementation of broadband radio frequency (RF) systems capable of providing highly linear magnetic signal to voltage transfer with high dynamic range, including active electrically small antennas (ESAs). Among the proposed quantum cells which are bi-SQUID and Differential Quantum Cell (DQC), the latter delivered better performance for SQAs. A prototype of the transformer-less active ESA based on a 2D SQA with nonsuperconducting electric connection of the DQCs was fabricated using HYPRES niobium process with critical current density 4.5 kA/cm2. The measured voltage response is characterized by a peak-to-peak swing of ~100 mV and steepness of ~6500 μV/μT.
Stochastic description for open quantum systems
Calzetta, E A; Verdaguer, E; Calzetta, Esteban; Roura, Albert; Verdaguer, Enric
2000-01-01
A linear open quantum system consisting of a harmonic oscillator coupled linearly to an infinite set of independent harmonic oscillators is considered; these oscillators have a general spectral density function and are initially in thermal equilibrium. Using the influence functional formalism a formal Langevin equation can be introduced to describe the system's fully quantum properties even beyond the semiclassical regime. It is shown that the reduced Wigner function for the system is exactly the formal distribution function resulting from averaging both over the initial conditions and the stochastic source of the formal Langevin equation. The master equation for the reduced density matrix is then obtained in the same way a Fokker-Planck equation can always be derived from a Langevin equation characterizing a stochastic process. We also show that the quantum correlation functions for the system can be deduced within the stochastic description provided by the Langevin equation. It is emphasized that when the s...
Quantum scaling in many-body systems
Continentino, Mucio A
2001-01-01
This book on quantum phase transitions has been written by one of the pioneers in the application of scaling ideas to many-body systems - a new and exciting subject that has relevance to many areas of condensed matter and theoretical physics. One of the few books on the subject, it emphasizes strongly correlated electronic systems. Although dealing with complex problems in statistical mechanics, it does not lose sight of the experiments and the actual physical systems which motivate the theoretical work. The book starts by presenting the scaling theory of quantum critical phenomena. Critical e
On the Velocity of Moving Relativistic Unstable Quantum Systems
Directory of Open Access Journals (Sweden)
K. Urbanowski
2015-01-01
Full Text Available We study properties of moving relativistic quantum unstable systems. We show that in contrast to the properties of classical particles and quantum stable objects the velocity of freely moving relativistic quantum unstable systems cannot be constant in time. We show that this new quantum effect results from the fundamental principles of the quantum theory and physics: it is a consequence of the principle of conservation of energy and of the fact that the mass of the quantum unstable system is not defined. This effect can affect the form of the decay law of moving relativistic quantum unstable systems.
Scattering theory for open quantum systems
Energy Technology Data Exchange (ETDEWEB)
Behrndt, Jussi [Technische Univ. Berlin (Germany). Inst. fuer Mathematik; Malamud, Mark M. [Donetsk National University (Ukraine). Dept. of Mathematics; Neidhardt, Hagen [Weierstrass-Institut fuer Angewandte Analysis und Stochastik (WIAS) im Forschungsverbund Berlin e.V. (Germany)
2006-07-01
Quantum systems which interact with their environment are often modeled by maximal dissipative operators or so-called Pseudo-Hamiltonians. In this paper the scattering theory for such open systems is considered. First it is assumed that a single maximal dissipative operator A{sub D} in a Hilbert space H is used to describe an open quantum system. In this case the minimal self-adjoint dilation K of A{sub D} can be regarded as the Hamiltonian of a closed system which contains the open system {l_brace}A{sub D},h{r_brace}, but since K is necessarily not semibounded from below, this model is difficult to interpret from a physical point of view. In the second part of the paper an open quantum system is modeled with a family {l_brace}A({mu}){r_brace} of maximal dissipative operators depending on energy {mu}, and it is shown that the open system can be embedded into a closed system where the Hamiltonian is semibounded. Surprisingly it turns out that the corresponding scattering matrix can be completely recovered from scattering matrices of single Pseudo-Hamiltonians as in the first part of the paper. The general results are applied to a class of Sturm-Liouville operators arising in dissipative and quantum transmitting Schroedinger-Poisson systems. (orig.)
Statistical thermodynamics of polymer quantum systems
Chacón-Acosta, Guillermo; Dagdug, Leonardo; Morales-Técotl, Hugo A
2011-01-01
Polymer quantum systems are mechanical models quantized similarly as loop quantum gravity. It is actually in quantizing gravity that the polymer term holds proper as the quantum geometry excitations yield a reminiscent of a polymer material. In such an approach both non-singular cosmological models and a microscopic basis for the entropy of some black holes have arisen. Also important physical questions for these systems involve thermodynamics. With this motivation, in this work, we study the statistical thermodynamics of two one dimensional {\\em polymer} quantum systems: an ensemble of oscillators that describe a solid and a bunch of non-interacting particles in a box, which thus form an ideal gas. We first study the spectra of these polymer systems. It turns out useful for the analysis to consider the length scale required by the quantization and which we shall refer to as polymer length. The dynamics of the polymer oscillator can be given the form of that for the standard quantum pendulum. Depending on the...
Heisenberg Picture Approach to the Stability of Quantum Markov Systems
Pan, Yu; Amini, Hadis; Miao, Zibo; Gough, John; Ugrinovskii, Valery; James, Matthew R.
2014-01-01
Quantum Markovian systems, modeled as unitary dilations in the quantum stochastic calculus of Hudson and Parthasarathy, have become standard in current quantum technological applications. This paper investigates the stability theory of such systems. Lyapunov-type conditions in the Heisenberg picture are derived in order to stabilize the evolution of system operators as well as the underlying dynamics of the quantum states. In particular, using the quantum Markov semigroup associated with this...
On the velocity of moving relativistic unstable quantum systems
Urbanowski, K
2015-01-01
We study properties of moving relativistic quantum unstable systems. We show that in contrast to the properties of classical particles and quantum stable objects the velocity of moving freely relativistic quantum unstable systems can not be constant in time. We show that this effect results from the fundamental principles of the quantum theory and physics: It is a consequence of the principle of conservation of energy and of the fact that the mass of the quantum unstable system is not definite.
The quantum human central neural system.
Alexiou, Athanasios; Rekkas, John
2015-01-01
In this chapter we present Excess Entropy Production for human aging system as the sum of their respective subsystems and electrophysiological status. Additionally, we support the hypothesis of human brain and central neural system quantumness and we strongly suggest the theoretical and philosophical status of human brain as one of the unknown natural Dirac magnetic monopoles placed in the center of a Riemann sphere.
Quantum Aharonov-Bohm Billiard System
Chuu, D S; Chuu, Der-San; Lin, De-Hone
1999-01-01
The Green's functions of the two and three-dimensional relativistic Aharonov-Bohm (A-B) systems are given by the path integral approach. In addition the exact radial Green's functions of the spherical A-B quantum billiard system in two and three-dimensional are obtained via the perturbation techanique of $\\delta $-function.
Effective operator formalism for open quantum systems
DEFF Research Database (Denmark)
Reiter, Florentin; Sørensen, Anders Søndberg
2012-01-01
We present an effective operator formalism for open quantum systems. Employing perturbation theory and adiabatic elimination of excited states for a weakly driven system, we derive an effective master equation which reduces the evolution to the ground-state dynamics. The effective evolution...
Recent advances in quantum integrable systems
Energy Technology Data Exchange (ETDEWEB)
Amico, L.; Belavin, A.; Buffenoir, E.; Castro Alvaredo, A.; Caudrelier, V.; Chakrabarti, A.; Corrig, E.; Crampe, N.; Deguchi, T.; Dobrev, V.K.; Doikou, A.; Doyon, B.; Feher, L.; Fioravanti, D.; Gohmann, F.; Hallnas, M.; Jimbo, M.; Konno, N.C.H.; Korchemsky, G.; Kulish, P.; Lassalle, M.; Maillet, J.M.; McCoy, B.; Mintchev, M.; Pakuliak, S.; Quano, F.Y.Z.; Ragnisco, R.; Ravanini, F.; Rittenberg, V.; Rivasseau, V.; Rossi, M.; Satta, G.; Sedrakyan, T.; Shiraishi, J.; Suzuki, N.C.J.; Yamada, Y.; Zamolodchikov, A.; Ishimoto, Y.; Nagy, Z.; Posta, S.; Sedra, M.B.; Zuevskiy, A.; Gohmann, F
2005-07-01
This meeting was dedicated to different aspects of the theory of quantum integrable systems. The organizers have intended to concentrate on topics related to the study of correlation functions, to systems with boundaries and to models at roots of unity. This document gathers the abstracts of 32 contributions, most of the contributions are accompanied by the set of transparencies.
Quantum Algorithm for the Toeplitz Systems
Wan, Lin-Chun; Pan, Shi-Jie; Gao, Fei; Wen, Qiao-Yan
2016-01-01
Solving the Toeplitz systems, which is to find the vector $x$ such that $T_nx = b$ given a $n\\times n$ Toeplitz matrix $T_n$ and a vector $b$, has a variety of applications in mathematics and engineering. In this paper, we present a quantum algorithm for solving the Toeplitz systems, in which a quantum state encoding the solution with error $\\epsilon$ is generated. It is shown that our algorithm's complexity is nearly linear in the condition number, and polylog in the dimensions $n$ and in the inverse error $\\epsilon^{-1}$. This implies our algorithm is exponentially faster than the best classical algorithm for the same problem if the condition number of $T_n$ is $O(\\textrm{poly}(\\textrm{log}\\,n))$. Since no assumption on the sparseness of $T_n$ is demanded in our algorithm, the algorithm can serve as an example of quantum algorithms for solving non-sparse linear systems.
Adiabatic Theorem for Quantum Spin Systems
Bachmann, S.; De Roeck, W.; Fraas, M.
2017-08-01
The first proof of the quantum adiabatic theorem was given as early as 1928. Today, this theorem is increasingly applied in a many-body context, e.g., in quantum annealing and in studies of topological properties of matter. In this setup, the rate of variation ɛ of local terms is indeed small compared to the gap, but the rate of variation of the total, extensive Hamiltonian, is not. Therefore, applications to many-body systems are not covered by the proofs and arguments in the literature. In this Letter, we prove a version of the adiabatic theorem for gapped ground states of interacting quantum spin systems, under assumptions that remain valid in the thermodynamic limit. As an application, we give a mathematical proof of Kubo's linear response formula for a broad class of gapped interacting systems. We predict that the density of nonadiabatic excitations is exponentially small in the driving rate and the scaling of the exponent depends on the dimension.
Development of radiation tolerant components for the Quench Protection System at CERN
Bitterling, O.; Denz, R.; Steckert, J.; Uznanski, S.
2016-01-01
This paper describes the results of irradiation campaigns with the high resolution Analog to Digital Converter (ADC) ADS1281. This ADC will be used as part of a revised quench detection circuit for the 600 A corrector magnets at the CERN Large Hadron Collider (LHC) . To verify the radiation tolerance of the ADC an irradiation campaign using a proton beam, applying doses up to 3,4 kGy was conducted. The resulting data and an analysis of the found failure modes is discussed in this paper. Several mitigation measures are described that allow to reduce the error rate to levels acceptable for operation as part of the LHC QPS.
Heisenberg picture approach to the stability of quantum Markov systems
Energy Technology Data Exchange (ETDEWEB)
Pan, Yu, E-mail: yu.pan@anu.edu.au, E-mail: zibo.miao@anu.edu.au; Miao, Zibo, E-mail: yu.pan@anu.edu.au, E-mail: zibo.miao@anu.edu.au [Research School of Engineering, Australian National University, Canberra, ACT 0200 (Australia); Amini, Hadis, E-mail: nhamini@stanford.edu [Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States); Gough, John, E-mail: jug@aber.ac.uk [Institute of Mathematics and Physics, Aberystwyth University, SY23 3BZ Wales (United Kingdom); Ugrinovskii, Valery, E-mail: v.ugrinovskii@gmail.com [School of Engineering and Information Technology, University of New South Wales at ADFA, Canberra, ACT 2600 (Australia); James, Matthew R., E-mail: matthew.james@anu.edu.au [ARC Centre for Quantum Computation and Communication Technology, Research School of Engineering, Australian National University, Canberra, ACT 0200 (Australia)
2014-06-15
Quantum Markovian systems, modeled as unitary dilations in the quantum stochastic calculus of Hudson and Parthasarathy, have become standard in current quantum technological applications. This paper investigates the stability theory of such systems. Lyapunov-type conditions in the Heisenberg picture are derived in order to stabilize the evolution of system operators as well as the underlying dynamics of the quantum states. In particular, using the quantum Markov semigroup associated with this quantum stochastic differential equation, we derive sufficient conditions for the existence and stability of a unique and faithful invariant quantum state. Furthermore, this paper proves the quantum invariance principle, which extends the LaSalle invariance principle to quantum systems in the Heisenberg picture. These results are formulated in terms of algebraic constraints suitable for engineering quantum systems that are used in coherent feedback networks.
Heisenberg picture approach to the stability of quantum Markov systems
Pan, Yu; Amini, Hadis; Miao, Zibo; Gough, John; Ugrinovskii, Valery; James, Matthew R.
2014-06-01
Quantum Markovian systems, modeled as unitary dilations in the quantum stochastic calculus of Hudson and Parthasarathy, have become standard in current quantum technological applications. This paper investigates the stability theory of such systems. Lyapunov-type conditions in the Heisenberg picture are derived in order to stabilize the evolution of system operators as well as the underlying dynamics of the quantum states. In particular, using the quantum Markov semigroup associated with this quantum stochastic differential equation, we derive sufficient conditions for the existence and stability of a unique and faithful invariant quantum state. Furthermore, this paper proves the quantum invariance principle, which extends the LaSalle invariance principle to quantum systems in the Heisenberg picture. These results are formulated in terms of algebraic constraints suitable for engineering quantum systems that are used in coherent feedback networks.
Relativistic quantum metrology in open system dynamics.
Tian, Zehua; Wang, Jieci; Fan, Heng; Jing, Jiliang
2015-01-22
Quantum metrology studies the ultimate limit of precision in estimating a physical quantity if quantum strategies are exploited. Here we investigate the evolution of a two-level atom as a detector which interacts with a massless scalar field using the master equation approach for open quantum system. We employ local quantum estimation theory to estimate the Unruh temperature when probed by a uniformly accelerated detector in the Minkowski vacuum. In particular, we evaluate the Fisher information (FI) for population measurement, maximize its value over all possible detector preparations and evolution times, and compare its behavior with that of the quantum Fisher information (QFI). We find that the optimal precision of estimation is achieved when the detector evolves for a long enough time. Furthermore, we find that in this case the FI for population measurement is independent of initial preparations of the detector and is exactly equal to the QFI, which means that population measurement is optimal. This result demonstrates that the achievement of the ultimate bound of precision imposed by quantum mechanics is possible. Finally, we note that the same configuration is also available to the maximum of the QFI itself.
Time dilation in quantum systems and decoherence
Pikovski, Igor; Zych, Magdalena; Costa, Fabio; Brukner, Časlav
2017-02-01
Both quantum mechanics and general relativity are based on principles that defy our daily intuitions, such as time dilation, quantum interference and entanglement. Because the regimes where the two theories are typically tested are widely separated, their foundational principles are rarely jointly studied. Recent works have found that novel phenomena appear for quantum particles with an internal structure in the presence of time dilation, which can take place at low energies and in weak gravitational fields. Here we briefly review the effects of time dilation on quantum interference and generalize the results to a variety of systems. In addition, we provide an extended study of the basic principles of quantum theory and relativity that are of relevance for the effects and also address several questions that have been raised, such as the description in different reference frames, the role of the equivalence principle and the effective irreversibility of the decoherence. The manuscript clarifies some of the counterintuitive aspects arising when quantum phenomena and general relativistic effects are jointly considered.
Directory of Open Access Journals (Sweden)
A. M. de Paor
1998-01-01
Full Text Available Hide (Nonlinear Processes in Geophysics, 1998 has produced a new mathematical model of a self-exciting homopolar dynamo driving a series- wound motor, as a continuing contribution to the theory of the geomagnetic field. By a process of exact perturbation analysis, followed by combination and partial solution of differential equations, the complete nonlinear quenching of current fluctuations reported by Hide in the case that a parameter ε has the value 1 is proved via the Popov theorem from feedback system stability theory.
Network realization of triplet-type quantum stochastic systems
Zhou, Shaosheng; Fu, Shizhou; Chen, Yuping
2017-01-01
This paper focuses on a problem of network synthesis for a class of quantum stochastic systems. The systems under consideration are of triplet-type form and stem from linear quantum optics and linear quantum circuits. A new quantum network realization approach is proposed by generalizing the scattering operator from the scalar form to a unitary matrix in network components. It shows that the triplet-type quantum stochastic system can be approximated by a quantum network which consists of some one-degree-of-freedom generalized open-quantum harmonic oscillators (1DGQHOs) via series, concatenation and feedback connections.
Constraint algebra for interacting quantum systems
Fubini, S.; Roncadelli, M.
1988-04-01
We consider relativistic constrained systems interacting with external fields. We provide physical arguments to support the idea that the quantum constraint algebra should be the same as in the free quantum case. For systems with ordering ambiguities this principle is essential to obtain a unique quantization. This is shown explicitly in the case of a relativistic spinning particle, where our assumption about the constraint algebra plus invariance under general coordinate transformations leads to a unique S-matrix. On leave from Dipartimento di Fisica Nucleare e Teorica, Università di Pavia and INFN, I-27100 Pavia, Italy.
Storage of energy in confined quantum systems
Malbouisson, A. P. C.
2002-01-01
Using the non-perturbative method of {\\it dressed} states introduced in previous publications [N.P.Andion, A.P.C. Malbouisson and A. Mattos Neto, J.Phys.{\\bf A34}, 3735, (2001); G. Flores-Hidalgo, A.P.C. Malbouisson, Y.W. Milla, Phys. Rev. A, {\\bf 65}, 063314 (2002)], we study the evolution of a confined quantum mechanical system embedded in a {\\it ohmic} environment. Our approach furnishes a theoretical mechanism to control inhibition of the decay of excited quantum systems in cavities, in b...
Quons in a Quantum Dissipative System
Lee, Taejin
2015-01-01
String theory proves to be an imperative tool to explore the critical behavior of the quantum dissipative system. We discuss the quantum particles moving in two dimensions, in the presence of a uniform magnetic field, subject to a periodic potential and a dissipative force, which are described by the dissipative Wannier-Azbel-Hofstadter (DWAH) model. Using string theory formulation of the model, we find that the elementary excitations of the system at the generic points of the off-critical regions, in the zero temperature limit are quons, which satisfy q-deformed statistics.
Reversible part of a quantum dynamical system
2016-01-01
In this work a quantum dynamical system $(\\mathfrak M,\\Phi, \\varphi)$ is constituted by a von Neumann algebra $\\mathfrak M$, by a unital Schwartz map $\\Phi:\\mathfrak{M\\rightarrow M}$ and by a $\\Phi$-invariant normal faithful state $\\varphi$ on $\\mathfrak M$. The ergodic properties of a quantum dynamical system, depends on its reversible part $(\\mathfrak{D}_\\infty,\\Phi_\\infty, \\varphi_\\infty)$. It is constituted by a von Neumann sub-algebra $\\mathfrak{D}_\\infty$ of $\\mathfrak M$ by an automorp...
Teleportation in an indivisible quantum system
Directory of Open Access Journals (Sweden)
Kiktenko E.O.
2016-01-01
Full Text Available Teleportation protocol is conventionally treated as a method for quantum state transfer between two spatially separated physical carriers. Recent experimental progress in manipulation with high-dimensional quantum systems opens a new framework for implementation of teleportation protocols. We show that the one-qubit teleportation can be considered as a state transfer between subspaces of the whole Hilbert space of an indivisible eight-dimensional system. We explicitly show all corresponding operations and discuss an alternative way of implementation of similar tasks.
First-principles derivation of density-functional formalism for quenched-annealed systems
Lafuente, Luis; Cuesta, José A.
2006-10-01
We derive from first principles (without resorting to the replica trick) a density-functional theory for fluids in quenched disordered matrices (QA-DFT). We show that the disorder-averaged free energy of the fluid is a functional of the average density profile of the fluid as well as the pair correlation of the fluid and matrix particles. For practical reasons it is preferable to use another functional: the disorder-averaged free energy plus the fluid-matrix interaction energy, which, for fixed fluid-matrix interaction potential, is a functional only of the average density profile of the fluid. When the matrix is created as a quenched configuration of another fluid, the functional can be regarded as depending on the density profile of the matrix fluid as well. In this situation, the replica Ornstein-Zernike equations which do not contain the blocking parts of the correlations can be obtained as functional identities in this formalism, provided the second derivative of this functional is interpreted as the connected part of the direct correlation function. The blocking correlations are totally absent from QA-DFT, but nevertheless the thermodynamics can be entirely obtained from the functional. We apply the formalism to obtain the exact functional for an ideal fluid in an arbitrary matrix, and discuss possible approximations for nonideal fluids.
Feshbach Projection Formalism for Open Quantum Systems
Chruściński, Dariusz; Kossakowski, Andrzej
2013-08-01
We provide a new approach to open quantum systems which is based on the Feshbach projection method. Instead of looking for a master equation for the dynamical map acting in the space of density operators we provide the corresponding equation for the evolution in the Hilbert space of the amplitude operators. Its solution enables one to construct a legitimate quantum evolution (completely positive and trace preserving). Our approach, contrary to the standard Nakajima-Zwanzig method, allows for a series of consistent approximations resulting in a legitimate quantum evolution. The new scheme is illustrated by the well-known spin-boson model beyond the rotating wave approximation. It is shown that the presence of counterrotating terms dramatically changes the asymptotic evolution of the system.
Quantum frustrated and correlated electron systems
Directory of Open Access Journals (Sweden)
P Thalmeier
2008-06-01
Full Text Available Quantum phases and fluctuations in correlated electron systems with frustration and competing interactions are reviewed. In the localized moment case the S=1/2 J1 - J2 - model on a square lattice exhibits a rich phase diagram with magnetic as well as exotic hidden order phases due to the interplay of frustration and quantum fluctuations. Their signature in magnetocaloric quantities and the high field magnetization are surveyed. The possible quantum phase transitions are discussed and applied to layered vanadium oxides. In itinerant electron systems frustration is an emergent property caused by electron correlations. It leads to enhanced spin fluctuations in a very large region of momentum space and therefore may cause heavy fermion type low temperature anomalies as in the 3d spinel compound LiV2O4 . Competing on-site and inter-site electronic interactions in Kondo compounds are responsible for the quantum phase transition between nonmagnetic Kondo singlet phase and magnetic phase such as observed in many 4f compounds. They may be described by Kondo lattice and simplified Kondo necklace type models. Their quantum phase transitions are investigated by numerical exact diagonalization and analytical bond operator methods respectively.
Quantum emulation of quasiperiodic systems
Senaratne, Ruwan; Geiger, Zachary; Fujiwara, Kurt; Singh, Kevin; Rajagopal, Shankari; Weld, David
2016-05-01
Tunable quasiperiodic optical traps can enable quantum emulation of electronic phenomena in quasicrystals. A 1D bichromatic lattice or a Gaussian beam intersecting a 2D square lattice in a direct analogy of the ``cut-and-project'' construction can be used to create tunable 1D quasiperiodic potentials for cold neutral atoms. We report on progress towards the observation of singular continuous diffraction patterns, fractal energy spectra, and Bloch oscillations in these synthetic quasicrystals. We will also discuss the existence of edge states which can be topologically pumped across the lattice by varying a phasonic parameter. We acknowledge support from the ONR, the ARO and the PECASE and DURIP programs, the AFOSR, the Alfred P. Sloan foundation and the President's Research Catalyst Award from the University of California Office of the President.
Lyapunov control of quantum systems with impulsive control fields.
Yang, Wei; Sun, Jitao
2013-01-01
We investigate the Lyapunov control of finite-dimensional quantum systems with impulsive control fields, where the studied quantum systems are governed by the Schrödinger equation. By three different Lyapunov functions and the invariant principle of impulsive systems, we study the convergence of quantum systems with impulsive control fields and propose new results for the mentioned quantum systems in the form of sufficient conditions. Two numerical simulations are presented to illustrate the effectiveness of the proposed control method.
EDITORIAL: CAMOP: Quantum Non-Stationary Systems CAMOP: Quantum Non-Stationary Systems
Dodonov, Victor V.; Man'ko, Margarita A.
2010-09-01
Although time-dependent quantum systems have been studied since the very beginning of quantum mechanics, they continue to attract the attention of many researchers, and almost every decade new important discoveries or new fields of application are made. Among the impressive results or by-products of these studies, one should note the discovery of the path integral method in the 1940s, coherent and squeezed states in the 1960-70s, quantum tunneling in Josephson contacts and SQUIDs in the 1960s, the theory of time-dependent quantum invariants in the 1960-70s, different forms of quantum master equations in the 1960-70s, the Zeno effect in the 1970s, the concept of geometric phase in the 1980s, decoherence of macroscopic superpositions in the 1980s, quantum non-demolition measurements in the 1980s, dynamics of particles in quantum traps and cavity QED in the 1980-90s, and time-dependent processes in mesoscopic quantum devices in the 1990s. All these topics continue to be the subject of many publications. Now we are witnessing a new wave of interest in quantum non-stationary systems in different areas, from cosmology (the very first moments of the Universe) and quantum field theory (particle pair creation in ultra-strong fields) to elementary particle physics (neutrino oscillations). A rapid increase in the number of theoretical and experimental works on time-dependent phenomena is also observed in quantum optics, quantum information theory and condensed matter physics. Time-dependent tunneling and time-dependent transport in nano-structures are examples of such phenomena. Another emerging direction of study, stimulated by impressive progress in experimental techniques, is related to attempts to observe the quantum behavior of macroscopic objects, such as mirrors interacting with quantum fields in nano-resonators. Quantum effects manifest themselves in the dynamics of nano-electromechanical systems; they are dominant in the quite new and very promising field of circuit
Topics on the stochastical treatement of an open quantum system
Sturzu, I
2002-01-01
The paper shortly presents the role of Stochastic Processes Theory in the present day Quantum Theory, and the relation to Operational Quantum Physics. The dynamics of an open quantum system is studied on a usual example from Quantum Optics, suggesting the definition of a Neumark-type dilation for the non-thermal states.
Classical system boundaries cannot be determined within quantum Darwinism
Fields, Chris
Multiple observers who interact with environmental encodings of the states of a macroscopic quantum system S as required by quantum Darwinism cannot demonstrate that they are jointly observing S without a joint a priori assumption of a classical boundary separating S from its environment E. Quantum Darwinism cannot, therefore, be regarded as providing a purely quantum-mechanical explanation of the "emergence" of classicality.
Quantum dynamics of biological systems and dust plasma nanoparticles
Lasukov, V. V.; Lasukova, T. V.; Lasukova, O. V.
2012-12-01
A quantum solution of the Fisher-Kolmogorov-Petrovskii-Piskunov equation with convection and linear diffusion is obtained which can provide the basis for the quantum biology and quantum microphysics equation. On this basis, quantum emission of biological systems, separate microorganisms (cells or bacteria), and dust plasma particles is investigated.
Quantum Entanglement in Optical Lattice Systems
2015-02-18
SECURITY CLASSIFICATION OF: Optical lattice systems provide an ideal platform for investigating entanglement because of their unprecedented level of...ABSTRACT Final report for ARO grant entitled "Quantum Entanglement in Optical Lattice Systems" Report Title Optical lattice systems provide an ideal ...2010): 0. doi: 10.1103/PhysRevA.82.063612 D. Blume, K. Daily. Breakdown of Universality for Unequal-Mass Fermi Gases with Infinite Scattering Length
Cui, Ping
The thesis comprises two major themes of quantum statistical dynamics. One is the development of quantum dissipation theory (QDT). It covers the establishment of some basic relations of quantum statistical dynamics, the construction of several nonequivalent complete second-order formulations, and the development of exact QDT. Another is related to the applications of quantum statistical dynamics to a variety of research fields. In particular, unconventional but novel theories of the electron transfer in Debye solvents, quantum transport, and quantum measurement are developed on the basis of QDT formulations. The thesis is organized as follows. In Chapter 1, we present some background knowledge in relation to the aforementioned two themes of this thesis. The key quantity in QDT is the reduced density operator rho(t) ≡ trBrho T(t); i.e., the partial trace of the total system and bath composite rhoT(t) over the bath degrees of freedom. QDT governs the evolution of reduced density operator, where the effects of bath are treated in a quantum statistical manner. In principle, the reduced density operator contains all dynamics information of interest. However, the conventional quantum transport theory is formulated in terms of nonequilibrium Green's function. The newly emerging field of quantum measurement in relation to quantum information and quantum computing does exploit a sort of QDT formalism. Besides the background of the relevant theoretical development, some representative experiments on molecular nanojunctions are also briefly discussed. In chapter 2, we outline some basic (including new) relations that highlight several important issues on QDT. The content includes the background of nonequilibrium quantum statistical mechanics, the general description of the total composite Hamiltonian with stochastic system-bath interaction, a novel parameterization scheme for bath correlation functions, a newly developed exact theory of driven Brownian oscillator (DBO
System and method for making quantum dots
Bakr, Osman M.
2015-05-28
Embodiments of the present disclosure provide for methods of making quantum dots (QDs) (passivated or unpassivated) using a continuous flow process, systems for making QDs using a continuous flow process, and the like. In one or more embodiments, the QDs produced using embodiments of the present disclosure can be used in solar photovoltaic cells, bio-imaging, IR emitters, or LEDs.
Quantum Phase Transitions in a Finite System
Leviatan, A
2006-01-01
A general procedure for studying finite-N effects in quantum phase transitions of finite systems is presented and applied to the critical-point dynamics of nuclei undergoing a shape-phase transition of second-order (continuous), and of first-order with an arbitrary barrier.
Eigenstate tracking in open quantum systems
Jing, Jun; Sarandy, Marcelo S.; Lidar, Daniel A.; Luo, Da-Wei; Wu, Lian-Ao
2016-10-01
Keeping a quantum system in a given instantaneous eigenstate is a control problem with numerous applications, e.g., in quantum information processing. The problem is even more challenging in the setting of open quantum systems, where environment-mediated transitions introduce additional decoherence channels. Adiabatic passage is a well-established solution but requires a sufficiently slow evolution time that is dictated by the adiabatic theorem. Here we develop a systematic projection theory formulation for the transitionless evolution of general open quantum systems described by time-local master equations. We derive a time-convolutionless dynamical equation for the target instantaneous eigenstate of a given time-dependent Hamiltonian. A transitionless dynamics then arises in terms of a competition between the average Hamiltonian gap and the decoherence rate, which implies optimal adiabaticity timescales. We show how eigenstate tracking can be accomplished via control pulses, without explicitly incorporating counter-diabatic driving, thus offering an alternative route to accelerate adiabaticity. We examine rectangular pulses, chaotic signals, and white noise, and find that, remarkably, the effectiveness of eigenstate tracking hardly depends on the details of the control functions. In all cases the control protocol keeps the system in the desired instantaneous eigenstate throughout the entire evolution, along an accelerated adiabatic path.
Lithography system using quantum entangled photons
Williams, Colin (Inventor); Dowling, Jonathan (Inventor); della Rossa, Giovanni (Inventor)
2002-01-01
A system of etching using quantum entangled particles to get shorter interference fringes. An interferometer is used to obtain an interference fringe. N entangled photons are input to the interferometer. This reduces the distance between interference fringes by n, where again n is the number of entangled photons.
Optimal control of complex atomic quantum systems
van Frank, S.; Bonneau, M.; Schmiedmayer, J.; Hild, S.; Gross, C.; Cheneau, M.; Bloch, I.; Pichler, T.; Negretti, A.; Calarco, T.; Montangero, S.
2016-10-01
Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control has been achieved on systems of increasing complexity. However, this control is still sub-optimal. In many scenarios, achieving a fast transformation is crucial to fight against decoherence and imperfection effects. Optimal control theory is believed to be the ideal candidate to bridge the gap between early stage proof-of-principle demonstrations and experimental protocols suitable for practical applications. Indeed, it can engineer protocols at the quantum speed limit – the fastest achievable timescale of the transformation. Here, we demonstrate such potential by computing theoretically and verifying experimentally the optimal transformations in two very different interacting systems: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We also show that such processes are robust with respect to perturbations, including temperature and atom number fluctuations.
Duality in the quantum Hall system
Lütken, C. A.; Ross, G. G.
1992-05-01
We suggest that a unified description of the integer and fractional phases of the quantum Hall system may be possible if the scaling diagram of transport coefficients is invariant under linear fractional (modular) transformations. In this model the hierarchy of states, as well as the observed universality of critical exponents, are consequences of a discrete SL(2,openZ) symmetry acting on the parameter space of an effective quantum-field theory. Available scaling data on the position of delocalization fixed points in the integer case and the position of mobility fixed points in the fractional case agree with the model within experimental accuracy.
Effective Hamiltonian approach to periodically perturbed quantum optical systems
Energy Technology Data Exchange (ETDEWEB)
Sainz, I. [Centro Universitario de los Lagos, Universidad de Guadalajara, Enrique Diaz de Leon, 47460 Lagos de Moreno, Jal. (Mexico)]. E-mail: isa@culagos.udg.mx; Klimov, A.B. [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410 Guadalajara, Jal. (Mexico)]. E-mail: klimov@cencar.udg.mx; Saavedra, C. [Center for Quantum Optics and Quantum Information, Departamento de Fisica, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)]. E-mail: csaaved@udec.cl
2006-02-20
We apply the method of Lie-type transformations to Floquet Hamiltonians for periodically perturbed quantum systems. Some typical examples of driven quantum systems are considered in the framework of this approach and corresponding effective time dependent Hamiltonians are found.
Information Geometry in Time Dependent Quantum Systems and the Geometric Phase
Dey, Anshuman; Roy, Pratim; Sarkar, Tapobrata
2016-01-01
We study information theoretic geometry in time dependent quantum mechanical systems. First, we discuss global properties of the parameter manifold for two level systems exemplified by i) Rabi oscillations and ii) quenching dynamics of the XY spin chain in a transverse magnetic field, when driven across anisotropic criticality. Next, we comment upon the nature of the geometric phase from classical holonomy analyses of such parameter manifolds. In the context of the transverse XY model in the thermodynamic limit, our results are in contradiction to those in the existing literature, and we argue why the issue deserves a more careful analysis. Finally, we speculate on a novel geometric phase in the model, when driven across a quantum critical line.
Les Houches Summer School : Strongly Interacting Quantum Systems out of Equilibrium
Millis, Andrew J; Parcollet, Olivier; Saleur, Hubert; Cugliandolo, Leticia F
2016-01-01
Over the last decade new experimental tools and theoretical concepts are providing new insights into collective nonequilibrium behavior of quantum systems. The exquisite control provided by laser trapping and cooling techniques allows us to observe the behavior of condensed bose and degenerate Fermi gases under nonequilibrium drive or after quenches' in which a Hamiltonian parameter is suddenly or slowly changed. On the solid state front, high intensity short-time pulses and fast (femtosecond) probes allow solids to be put into highly excited states and probed before relaxation and dissipation occur. Experimental developments are matched by progress in theoretical techniques ranging from exact solutions of strongly interacting nonequilibrium models to new approaches to nonequilibrium numerics. The summer school Strongly interacting quantum systems out of equilibrium' held at the Les Houches School of Physics as its XCIX session was designed to summarize this progress, lay out the open questions and define dir...
Global canonical symmetry in a quantum system
Institute of Scientific and Technical Information of China (English)
李子平
1996-01-01
Based on the phase-space path integral for a system with a regular or singular Lagrangian the generalized canonical Ward identities under the global symmetry transformation in extended phase space are deduced respectively, thus the relations among Green functions can be found. The connection between canonical symmetries and conservation laws at the quantum level is established. It is pointed out that this connection in classical theories, in general, is no longer always preserved in quantum theories. The advantage of our formulation is that we do not need to carry out the integration over the canonical momenta in phase-space generating functional as usually performed. A precise discussion of quantization for a nonlinear sigma model with Hopf and Chern-Simons terms is reexamined. The property of fractional spin at quantum level has been clarified.
Dynamics of quantum trajectories in chaotic systems
Wisniacki, D A; Benito, R M
2003-01-01
Quantum trajectories defined in the de Broglie--Bohm theory provide a causal way to interpret physical phenomena. In this Letter, we use this formalism to analyze the short time dynamics induced by unstable periodic orbits in a classically chaotic system, a situation in which scars are known to play a very important role. We find that the topologies of the quantum orbits are much more complicated than that of the scarring and associated periodic orbits, since the former have quantum interference built in. Thus scar wave functions are necessary to analyze the corresponding dynamics. Moreover, these topologies imply different return routes to the vicinity of the initial positions, and this reflects in the existence of different contributions in each peak of the survival probability function.
Simple quantum systems in the momentum representation
Núñez-Yépez, H N; Martínez y Romero, R P; Salas-Brito, A L
2000-01-01
The momentum representation is seldom used in quantum mechanics courses. Some students are thence surprised by the change in viewpoint when, in doing advanced work, they have to use the momentum rather than the coordinate representation. In this work, we give an introduction to quantum mechanics in momentum space, where the Schrödinger equation becomes an integral equation. To this end we discuss standard problems, namely, the free particle, the quantum motion under a constant potential, a particle interacting with a potential step, and the motion of a particle under a harmonic potential. What is not so standard is that they are all conceived from momentum space and hence they, with the exception of the free particle, are not equivalent to the coordinate space ones with the same names. All the problems are solved within the momentum representation making no reference to the systems they correspond to in the coordinate representation.
Edge reconstructions in fractional quantum Hall systems.
Joglekar, Yogesh; Nguyen, Hoang; Murthy, Ganpathy
2003-03-01
Two dimensional electron systems exhibiting fractional quantum Hall effects are characterized by a quantized Hall conductance and a dissipationless bulk. The transport in these systems occurs only at the edges where gapless excitations are possible [1]. We present a microscopic calculation of these egde-states at filling factors ν=1/3 and ν=2/5 using the Hamiltonian theory of the fractional quantum Hall effect [2]. We find that the quantum Hall egde undergoes a reconstruction as the confining potential, produced by the background charge density, softens [3,4]. Our results have implications to the tunneling experiments into the edge of a fractional quantum Hall system [5]. 1: X. G.Wen, Phys. Rev. Lett. 64, 2206 (1990). 2: R. Shankar and G. Murthy, Phys. Rev. Lett. 79, 4437 (1997). 3: C. de C. Chamon and X. G. Wen, Phys. Rev. B 49, 8227 (1994). 4: X. Wan, K. Yang, and E. H. Razayi, Phys. Rev. Lett. 88, 056802 (2002). 5: A.M.Chang et al., Phys. Rev. Lett. 86, 143 (2000).
Periodic thermodynamics of open quantum systems
Brandner, Kay; Seifert, Udo
2016-06-01
The thermodynamics of quantum systems coupled to periodically modulated heat baths and work reservoirs is developed. By identifying affinities and fluxes, the first and the second law are formulated consistently. In the linear response regime, entropy production becomes a quadratic form in the affinities. Specializing to Lindblad dynamics, we identify the corresponding kinetic coefficients in terms of correlation functions of the unperturbed dynamics. Reciprocity relations follow from symmetries with respect to time reversal. The kinetic coefficients can be split into a classical and a quantum contribution subject to an additional constraint, which follows from a natural detailed balance condition. This constraint implies universal bounds on efficiency and power of quantum heat engines. In particular, we show that Carnot efficiency cannot be reached whenever quantum coherence effects are present, i.e., when the Hamiltonian used for work extraction does not commute with the bare system Hamiltonian. For illustration, we specialize our universal results to a driven two-level system in contact with a heat bath of sinusoidally modulated temperature.
Periodic thermodynamics of open quantum systems.
Brandner, Kay; Seifert, Udo
2016-06-01
The thermodynamics of quantum systems coupled to periodically modulated heat baths and work reservoirs is developed. By identifying affinities and fluxes, the first and the second law are formulated consistently. In the linear response regime, entropy production becomes a quadratic form in the affinities. Specializing to Lindblad dynamics, we identify the corresponding kinetic coefficients in terms of correlation functions of the unperturbed dynamics. Reciprocity relations follow from symmetries with respect to time reversal. The kinetic coefficients can be split into a classical and a quantum contribution subject to an additional constraint, which follows from a natural detailed balance condition. This constraint implies universal bounds on efficiency and power of quantum heat engines. In particular, we show that Carnot efficiency cannot be reached whenever quantum coherence effects are present, i.e., when the Hamiltonian used for work extraction does not commute with the bare system Hamiltonian. For illustration, we specialize our universal results to a driven two-level system in contact with a heat bath of sinusoidally modulated temperature.
Statistical entropy of open quantum systems
Durão, L. M. M.; Caldeira, A. O.
2016-12-01
Dissipative quantum systems are frequently described within the framework of the so-called "system-plus-reservoir" approach. In this work we assign their description to the Maximum Entropy Formalism and compare the resulting thermodynamic properties with those of the well-established approaches. Due to the non-negligible coupling to the heat reservoir, these systems are nonextensive by nature, and the former task may require the use of nonextensive parameter dependent informational entropies. In doing so, we address the problem of choosing appropriate forms of those entropies in order to describe a consistent thermodynamics for dissipative quantum systems. Nevertheless, even having chosen the most successful and popular forms of those entropies, we have proven our model to be a counterexample where this sort of approach leads us to wrong results.
Security of practical quantum key distribution systems
Energy Technology Data Exchange (ETDEWEB)
Jain, Nitin
2015-02-24
This thesis deals with practical security aspects of quantum key distribution (QKD) systems. At the heart of the theoretical model of any QKD system lies a quantum-mechanical security proof that guarantees perfect secrecy of messages - based on certain assumptions. However, in practice, deviations between the theoretical model and the physical implementation could be exploited by an attacker to break the security of the system. These deviations may arise from technical limitations and operational imperfections in the physical implementation and/or unrealistic assumptions and insufficient constraints in the theoretical model. In this thesis, we experimentally investigate in depth several such deviations. We demonstrate the resultant vulnerabilities via proof-of-principle attacks on a commercial QKD system from ID Quantique. We also propose countermeasures against the investigated loopholes to secure both existing and future QKD implementations.
Notions of controllability for quantum mechanical systems
Albertini, F
2001-01-01
In this paper, we define four different notions of controllability of physical interest for multilevel quantum mechanical systems. These notions involve the possibility of driving the evolution operator as well as the state of the system. We establish the connections among these different notions as well as methods to verify controllability. The paper also contains results on the relation between the controllability in arbitrary small time of a system varying on a compact transformation Lie group and the corresponding system on the associated homogeneous space. As an application, we prove that, for the system of two interacting spin 1/2 particles, not every state transfer can be obtained in arbitrary small time.
Geometric measure of quantum discord for an arbitrary state of a bipartite quantum system
Hassan, Ali Saif M; Joag, Pramod S
2010-01-01
Quantum discord, as introduced by Olliver and Zurek [Phys. Rev. Lett. \\textbf{88}, 017901 (2001)], is a measure of the discrepancy between quantum versions of two classically equivalent expressions for mutual information. Dakic, Vedral, and Brukner [arXiv:1004.0190 (2010)] introduced a geometric measure of quantum discord and derived an explicit formula for any two-qubit state. Luo and Fu [Phys. Rev. A \\textbf{82}, 034302 (2010)] introduced another form for geometric measure of quantum discord. We find an exact formula for the geometric measure of quantum discord for an arbitrary state of a $m\\times n$ bipartite quantum system.
Quantum computation in a quantum-dot-Majorana-fermion hybrid system
Xue, Zheng-Yuan
2012-01-01
We propose a scheme to implement universal quantum computation in a quantum-dot-Majorana-fermion hybrid system. Quantum information is encoded on pairs of Majorana fermions, which live on the the interface between topologically trivial and nontrivial sections of a quantum nanowire deposited on an s-wave superconductor. Universal single-qubit gates on topological qubit can be achieved. A measurement-based two-qubit Controlled-Not gate is produced with the help of parity measurements assisted by the quantum-dot and followed by prescribed single-qubit gates. The parity measurement, on the quantum-dot and a topological qubit, is achieved by the Aharonov- Casher effect.
Quantum Monte Carlo approaches for correlated systems
Becca, Federico
2017-01-01
Over the past several decades, computational approaches to studying strongly-interacting systems have become increasingly varied and sophisticated. This book provides a comprehensive introduction to state-of-the-art quantum Monte Carlo techniques relevant for applications in correlated systems. Providing a clear overview of variational wave functions, and featuring a detailed presentation of stochastic samplings including Markov chains and Langevin dynamics, which are developed into a discussion of Monte Carlo methods. The variational technique is described, from foundations to a detailed description of its algorithms. Further topics discussed include optimisation techniques, real-time dynamics and projection methods, including Green's function, reptation and auxiliary-field Monte Carlo, from basic definitions to advanced algorithms for efficient codes, and the book concludes with recent developments on the continuum space. Quantum Monte Carlo Approaches for Correlated Systems provides an extensive reference ...
Multiple-state quantum Otto engine, 1D box system
Latifah, E.; Purwanto, A.
2014-03-01
Quantum heat engines produce work using quantum matter as their working substance. We studied adiabatic and isochoric processes and defined the general force according to quantum system. The processes and general force are used to evaluate a quantum Otto engine based on multiple-state of one dimensional box system and calculate the efficiency. As a result, the efficiency depends on the ratio of initial and final width of system under adiabatic processes.
Multiple-state quantum Otto engine, 1D box system
Energy Technology Data Exchange (ETDEWEB)
Latifah, E., E-mail: enylatifah@um.ac.id [Laboratory of Theoretical Physics and Natural Philosophy, Physics Department, Institut Teknologi Sepuluh Nopember, ITS, Surabaya, Indonesia and Physics Department, Malang State University (Indonesia); Purwanto, A. [Laboratory of Theoretical Physics and Natural Philosophy, Physics Department, Institut Teknologi Sepuluh Nopember, ITS, Surabaya (Indonesia)
2014-03-24
Quantum heat engines produce work using quantum matter as their working substance. We studied adiabatic and isochoric processes and defined the general force according to quantum system. The processes and general force are used to evaluate a quantum Otto engine based on multiple-state of one dimensional box system and calculate the efficiency. As a result, the efficiency depends on the ratio of initial and final width of system under adiabatic processes.
Mesoscopic systems: classical irreversibility and quantum coherence.
Barbara, Bernard
2012-09-28
Mesoscopic physics is a sub-discipline of condensed-matter physics that focuses on the properties of solids in a size range intermediate between bulk matter and individual atoms. In particular, it is characteristic of a domain where a certain number of interacting objects can easily be tuned between classical and quantum regimes, thus enabling studies at the border of the two. In magnetism, such a tuning was first realized with large-spin magnetic molecules called single-molecule magnets (SMMs) with archetype Mn(12)-ac. In general, the mesoscopic scale can be relatively large (e.g. micrometre-sized superconducting circuits), but, in magnetism, it is much smaller and can reach the atomic scale with rare earth (RE) ions. In all cases, it is shown how quantum relaxation can drastically reduce classical irreversibility. Taking the example of mesoscopic spin systems, the origin of irreversibility is discussed on the basis of the Landau-Zener model. A classical counterpart of this model is described enabling, in particular, intuitive understanding of most aspects of quantum spin dynamics. The spin dynamics of mesoscopic spin systems (SMM or RE systems) becomes coherent if they are well isolated. The study of the damping of their Rabi oscillations gives access to most relevant decoherence mechanisms by different environmental baths, including the electromagnetic bath of microwave excitation. This type of decoherence, clearly seen with spin systems, is easily recovered in quantum simulations. It is also observed with other types of qubits such as a single spin in a quantum dot or a superconducting loop, despite the presence of other competitive decoherence mechanisms. As in the molecular magnet V(15), the leading decoherence terms of superconducting qubits seem to be associated with a non-Markovian channel in which short-living entanglements with distributions of two-level systems (nuclear spins, impurity spins and/or charges) leading to 1/f noise induce τ(1)-like
Controllability of multi-partite quantum systems and selective excitation of quantum dots
Energy Technology Data Exchange (ETDEWEB)
Schirmer, S G [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Pullen, I C H [Department of Applied Mathematics and Computing, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Solomon, A I [Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
2005-10-01
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.
Classical synchronization indicates persistent entanglement in isolated quantum systems
Witthaut, Dirk; Wimberger, Sandro; Burioni, Raffaella; Timme, Marc
2017-04-01
Synchronization and entanglement constitute fundamental collective phenomena in multi-unit classical and quantum systems, respectively, both equally implying coordinated system states. Here, we present a direct link for a class of isolated quantum many-body systems, demonstrating that synchronization emerges as an intrinsic system feature. Intriguingly, quantum coherence and entanglement arise persistently through the same transition as synchronization. This direct link between classical and quantum cooperative phenomena may further our understanding of strongly correlated quantum systems and can be readily observed in state-of-the-art experiments, for example, with ultracold atoms.
Multimode optomechanical system in the quantum regime
Nielsen, William H P; Møller, Christoffer B; Polzik, Eugene S; Schliesser, Albert
2016-01-01
We realise a simple and robust optomechanical system with a multitude of long-lived ($Q>10^7$) mechanical modes in a phononic-bandgap shielded membrane resonator. An optical mode of a compact Fabry-Perot resonator detects these modes' motion with a measurement rate ($96~\\mathrm{kHz}$) that exceeds the mechanical decoherence rates already at moderate cryogenic temperatures ($10\\,\\mathrm{K}$). Reaching this quantum regime entails, i.~a., quantum measurement backaction exceeding thermal forces, and thus detectable optomechanical quantum correlations. In particular, we observe ponderomotive squeezing of the output light mediated by a multitude of mechanical resonator modes, with quantum noise suppression up to -2.4 dB (-3.6 dB if corrected for detection losses) and bandwidths $\\lesssim 90\\,\\mathrm{ kHz}$. The multi-mode nature of the employed membrane and Fabry-Perot resonators lends itself to hybrid entanglement schemes involving multiple electromagnetic, mechanical, and spin degrees of freedom.
Path integrals for dimerized quantum spin systems
Energy Technology Data Exchange (ETDEWEB)
Foussats, Adriana, E-mail: afoussats@gmail.co [Facultad de Ciencias Exactas, Ingenieria y Agrimensura and Instituto de Fisica Rosario (UNR-CONICET), Av. Pellegrini 250, 2000 Rosario (Argentina); Greco, Andres [Facultad de Ciencias Exactas, Ingenieria y Agrimensura and Instituto de Fisica Rosario (UNR-CONICET), Av. Pellegrini 250, 2000 Rosario (Argentina); Muramatsu, Alejandro [Institut fuer Theoretische Physik III, Universitaet Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart (Germany)
2011-01-11
Dimerized quantum spin systems may appear under several circumstances, e.g. by a modulation of the antiferromagnetic exchange coupling in space, or in frustrated quantum antiferromagnets. In general, such systems display a quantum phase transition to a Neel state as a function of a suitable coupling constant. We present here two path-integral formulations appropriate for spin S=1/2 dimerized systems. The first one deals with a description of the dimers degrees of freedom in an SO(4) manifold, while the second one provides a path-integral for the bond-operators introduced by Sachdev and Bhatt. The path-integral quantization is performed using the Faddeev-Jackiw symplectic formalism for constrained systems, such that the measures and constraints that result from the algebra of the operators is provided in both cases. As an example we consider a spin-Peierls chain, and show how to arrive at the corresponding field-theory, starting with both an SO(4) formulation and bond-operators.
Institute of Scientific and Technical Information of China (English)
Ji Ying-Hua; Hu Ju-Ju; Hu Yan
2012-01-01
We investigate the influence of environmental decoherence on the dynamics of a coupled qubit system and quantum correlation.We analyse the relationship between concurrence and the degree of initial entanglement or the purity of initial quantum state,and also their relationship with quantum discord.The results show that the decrease of the purity of an initial quantum state can induce the attenuation of concurrence or quantum discord,but the attenuation of quantum discord is obviously slower than the concurrence's,correspondingly the survival time of quantum discord is longer.Further investigation reveals that the robustness of quantum discord and concurrence relies on the entanglement degree of the initial quantum state.The higher the degree of entanglement,the more robust the quantum discord is than concurrence.And the reverse is equally true.Birth and death happen to quantum discord periodically and a newborn quantum discord comes into being under a certain condition,so does the concurrence.
Quantum Correlations Relativity for Continuous-Variables Bipartite Systems
Dugic, M; Jeknic-Dugic, J
2011-01-01
Based on the so-called Entanglement Relativity, we point out relativity of the more general non-classical (quantum) correlations for the continuous-variables bipartite systems. Our observation points out that quantum processing resources based on the non-classical correlations (non-zero quantum discord) are ubiquitous in such systems.
Isochronous classical systems and quantum systems with equally spaced spectra
Energy Technology Data Exchange (ETDEWEB)
Carinena, J F; Perelomov, A M; Ranada, M F [Departamento de Fisica Teorica, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza (Spain)
2007-11-15
We study isoperiodic classical systems, what allows us to find the classical isochronous systems, i.e. having a period independent of the energy. The corresponding quantum analog, systems with an equally spaced spectrum are analysed by looking for possible creation-like differential operators. The harmonic oscillator and the isotonic oscillator are the two main essentially unique examples of such situation.
Artificial quantum thermal bath: Engineering temperature for a many-body quantum system
Shabani, Alireza; Neven, Hartmut
2016-11-01
Temperature determines the relative probability of observing a physical system in an energy state when that system is energetically in equilibrium with its environment. In this paper we present a theory for engineering the temperature of a quantum system different from its ambient temperature. We define criteria for an engineered quantum bath that, when coupled to a quantum system with Hamiltonian H , drives the system to the equilibrium state e/-H/TTr (e-H /T) with a tunable parameter T . This is basically an analog counterpart of the digital quantum metropolis algorithm. For a system of superconducting qubits, we propose a circuit-QED approximate realization of such an engineered thermal bath consisting of driven lossy resonators. Our proposal opens the path to simulate thermodynamical properties of many-body quantum systems of size not accessible to classical simulations. Also we discuss how an artificial thermal bath can serve as a temperature knob for a hybrid quantum-thermal annealer.
Li, Jun; Lu, Dawei; Luo, Zhihuang; Laflamme, Raymond; Peng, Xinhua; Du, Jiangfeng
2016-07-01
Precisely characterizing and controlling realistic quantum systems under noises is a challenging frontier in quantum sciences and technologies. In developing reliable controls for open quantum systems, one is often confronted with the problem of the lack of knowledge on the system controllability. The purpose of this paper is to give a numerical approach to this problem, that is, to approximately compute the reachable set of states for coherently controlled quantum Markovian systems. The approximation consists of setting both upper and lower bounds for system's reachable region of states. Furthermore, we apply our reachability analysis to the control of the relaxation dynamics of a two-qubit nuclear magnetic resonance spin system. We implement some experimental tasks of quantum state engineering in this open system at a near optimal performance in view of purity: e.g., increasing polarization and preparing pseudopure states. These results demonstrate the usefulness of our theory and show interesting and promising applications of environment-assisted quantum dynamics.
The Quantum as an Emergent System
Grössing, G.; Fussy, S.; Mesa Pascasio, J.; Schwabl, H.
2012-05-01
Double slit interference is explained with the aid of what we call "21st century classical physics". We model a particle as an oscillator ("bouncer") in a thermal context, which is given by some assumed "zero-point" field of the vacuum. In this way, the quantum is understood as an emergent system, i.e., a steady-state system maintained by a constant throughput of (vacuum) energy. To account for the particle's thermal environment, we introduce a "path excitation field", which derives from the thermodynamics of the zero-point vacuum and which represents all possible paths a particle can take via thermal path fluctuations. The intensity distribution on a screen behind a double slit is calculated, as well as the corresponding trajectories and the probability density current. Further, particular features of the relative phase are shown to be responsible for nonlocal effects not only in ordinary quantum theory, but also in our classical approach.
The Quantum as an Emergent System
Groessing, Gerhard; Pascasio, Johannes Mesa; Schwabl, Herbert; 10.1088/1742-6596/361/1/012008
2012-01-01
Double slit interference is explained with the aid of what we call "21stcentury classical physics". We model a particle as an oscillator ("bouncer") in a thermal context, which is given by some assumed "zero-point" field of the vacuum. In this way, the quantum is understood as an emergent system, i.e., a steady-state system maintained by a constant throughput of (vacuum) energy. To account for the particle's thermal environment, we introduce a "path excitation field", which derives from the thermodynamics of the zero-point vacuum and which represents all possible paths a particle can take via thermal path fluctuations. The intensity distribution on a screen behind a double slit is calculated, as well as the corresponding trajectories and the probability density current. Further, particular features of the relative phase are shown to be responsible for nonlocal effects not only in ordinary quantum theory, but also in our classical approach.
Measuring entanglement entropy in a quantum many-body system
Rispoli, Matthew; Preiss, Philipp; Tai, Eric; Lukin, Alex; Schittko, Robert; Kaufman, Adam; Ma, Ruichao; Islam, Rajibul; Greiner, Markus
2016-05-01
The presence of large-scale entanglement is a defining characteristic of exotic quantum phases of matter. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. However, measuring entanglement remains a challenge. This is especially true in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. We demonstrate a novel approach to the measurement of entanglement entropy of any bosonic system, using a quantum gas microscope with tailored potential landscapes. This protocol enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. In general, these experiments exemplify a method enabling the measurement and characterization of quantum phase transitions and in particular would be apt for studying systems such as magnetic ordering within the quantum Ising model.
Randomized control of open quantum systems
Viola, L
2006-01-01
The problem of open-loop dynamical control of generic open quantum systems is addressed. In particular, I focus on the task of effectively switching off environmental couplings responsible for unwanted decoherence and dissipation effects. After revisiting the standard framework for dynamical decoupling via deterministic controls, I describe a different approach whereby the controller intentionally acquires a random component. An explicit error bound on worst-case performance of stochastic decoupling is presented.
Quantum phase transition and entanglement in Li atom system
Institute of Scientific and Technical Information of China (English)
2008-01-01
By use of the exact diagonalization method, the quantum phase transition and en- tanglement in a 6-Li atom system are studied. It is found that entanglement appears before the quantum phase transition and disappears after it in this exactly solvable quantum system. The present results show that the von Neumann entropy, as a measure of entanglement, may reveal the quantum phase transition in this model.
Open quantum systems and random matrix theory
Mulhall, Declan
2014-10-01
A simple model for open quantum systems is analyzed with RMT. The system is coupled to the continuum in a minimal way. In this paper we see the effect of opening the system on the level statistics, in particular the level spacing, width distribution and Δ3(L) statistic are examined as a function of the strength of this coupling. The usual super-radiant state is observed, and it is seen that as it is formed, the level spacing and Δ3(L) statistic exhibit the signatures of missed levels.
Open quantum systems and random matrix theory
Energy Technology Data Exchange (ETDEWEB)
Mulhall, Declan [Department of Physics/Engineering, University of Scranton, Scranton, Pennsylvania 18510-4642 (United States)
2014-10-15
A simple model for open quantum systems is analyzed with RMT. The system is coupled to the continuum in a minimal way. In this paper we see the effect of opening the system on the level statistics, in particular the level spacing, width distribution and Δ{sub 3}(L) statistic are examined as a function of the strength of this coupling. The usual super-radiant state is observed, and it is seen that as it is formed, the level spacing and Δ{sub 3}(L) statistic exhibit the signatures of missed levels.
Open quantum systems and Random Matrix Theory
Mulhall, Declan
2014-01-01
A simple model for open quantum systems is analyzed with Random Matrix Theory. The system is coupled to the continuum in a minimal way. In this paper we see the effect of opening the system on the level statistics, in particular the $\\Delta_3(L)$ statistic, width distribution and level spacing are examined as a function of the strength of this coupling. A super-radiant transition is observed, and it is seen that as it is formed, the level spacing and $\\Delta_3(L)$ statistic exhibit the signatures of missed levels.
Open quantum systems and random matrix theory
Mulhall, Declan
2015-01-01
A simple model for open quantum systems is analyzed with random matrix theory. The system is coupled to the continuum in a minimal way. In this paper the effect on the level statistics of opening the system is seen. In particular the Δ3(L ) statistic, the width distribution and the level spacing are examined as a function of the strength of this coupling. The emergence of a super-radiant transition is observed. The level spacing and Δ3(L ) statistics exhibit the signatures of missed levels or intruder levels as the super-radiant state is formed.
Quantum Information Biology: From Theory of Open Quantum Systems to Adaptive Dynamics
Asano, Masanari; Basieva, Irina; Khrennikov, Andrei; Ohya, Masanori; Tanaka, Yoshiharu; Yamato, Ichiro
This chapter reviews quantum(-like) information biology (QIB). Here biology is treated widely as even covering cognition and its derivatives: psychology and decision making, sociology, and behavioral economics and finances. QIB provides an integrative description of information processing by bio-systems at all scales of life: from proteins and cells to cognition, ecological and social systems. Mathematically QIB is based on the theory of adaptive quantum systems (which covers also open quantum systems). Ideologically QIB is based on the quantum-like (QL) paradigm: complex bio-systems process information in accordance with the laws of quantum information and probability. This paradigm is supported by plenty of statistical bio-data collected at all bio-scales. QIB re ects the two fundamental principles: a) adaptivity; and, b) openness (bio-systems are fundamentally open). In addition, quantum adaptive dynamics provides the most generally possible mathematical representation of these principles.
Quantum scaling in many-body systems an approach to quantum phase transitions
Continentino, Mucio
2017-01-01
Quantum phase transitions are strongly relevant in a number of fields, ranging from condensed matter to cold atom physics and quantum field theory. This book, now in its second edition, approaches the problem of quantum phase transitions from a new and unifying perspective. Topics addressed include the concepts of scale and time invariance and their significance for quantum criticality, as well as brand new chapters on superfluid and superconductor quantum critical points, and quantum first order transitions. The renormalisation group in real and momentum space is also established as the proper language to describe the behaviour of systems close to a quantum phase transition. These phenomena introduce a number of theoretical challenges which are of major importance for driving new experiments. Being strongly motivated and oriented towards understanding experimental results, this is an excellent text for graduates, as well as theorists, experimentalists and those with an interest in quantum criticality.
Ultracold Quantum Gases and Lattice Systems: Quantum Simulation of Lattice Gauge Theories
Wiese, U -J
2013-01-01
Abelian and non-Abelian gauge theories are of central importance in many areas of physics. In condensed matter physics, Abelian U(1) lattice gauge theories arise in the description of certain quantum spin liquids. In quantum information theory, Kitaev's toric code is a Z(2) lattice gauge theory. In particle physics, Quantum Chromodynamics (QCD), the non-Abelian SU(3) gauge theory of the strong interactions between quarks and gluons, is non-perturbatively regularized on a lattice. Quantum link models extend the concept of lattice gauge theories beyond the Wilson formulation, and are well suited for both digital and analog quantum simulation using ultracold atomic gases in optical lattices. Since quantum simulators do not suffer from the notorious sign problem, they open the door to studies of the real-time evolution of strongly coupled quantum systems, which are impossible with classical simulation methods. A plethora of interesting lattice gauge theories suggests itself for quantum simulation, which should al...
Transient Loschmidt echo in quenched Ising chains
Lupo, Carla; Schiró, Marco
2016-07-01
We study the response to sudden local perturbations of highly excited quantum Ising spin chains. The key quantity encoding this response is the overlap between time-dependent wave functions, which we write as a transient Loschmidt Echo. Its asymptotics at long time differences contain crucial information about the structure of the highly excited nonequilibrium environment induced by the quench. We compute the echo perturbatively for a weak local quench but for arbitrarily large global quench, using a cumulant expansion. Our perturbative results suggest that the echo decays exponentially, rather than power law as in the low-energy orthogonality catastrophe, a further example of quench-induced decoherence already found in the case of quenched Luttinger liquids. The emerging decoherence scale is set by the strength of the local potential and the bulk excitation energy.
Noise management to achieve superiority in quantum information systems.
Nemoto, Kae; Devitt, Simon; Munro, William J
2017-08-06
Quantum information systems are expected to exhibit superiority compared with their classical counterparts. This superiority arises from the quantum coherences present in these quantum systems, which are obviously absent in classical ones. To exploit such quantum coherences, it is essential to control the phase information in the quantum state. The phase is analogue in nature, rather than binary. This makes quantum information technology fundamentally different from our classical digital information technology. In this paper, we analyse error sources and illustrate how these errors must be managed for the system to achieve the required fidelity and a quantum superiority.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).
Samadi, Naser; Narimani, Saeedeh
2016-06-01
In this paper, L-cysteine (Cys) coated CdS quantum dots (QDs) have been prepared, which have excellent water-solubility and are highly stable in aqueous solution. These QDs is proposed as sensitizers for the determination of Ceftriaxone. The quantum dot nanoparticles were structurally and optically characterized by Ultra Violet-Visible absorption Spectroscopy (UV-vis absorption spectroscopy), Fourier transform infrared spectroscopy (FT-IR spectra) and photoluminescence (PL) emission spectroscopy. High resolution transmission electron microscopy (HRTEM) confirms that the Cys-CdS QDs have a spherical structure with good crystallinity. Therefore, a new simple and selective PL analysis system was developed for the determination of Ceftriaxone (CFX). Under the optimum conditions, The response of L-Cys capped CdS QDs as the probe was linearly proportional to the concentration of Ceftriaxone ions in the range of 1.6 × 10- 9-1.1 × 10- 3 M with a correlation coefficient (R2) of 0.9902. The limit of detection of this system was found to be 1.3 nM. This method is simple, sensitive and low cost.
Samadi, Naser; Narimani, Saeedeh
2016-06-15
In this paper, l-cysteine (Cys) coated CdS quantum dots (QDs) have been prepared, which have excellent water-solubility and are highly stable in aqueous solution. These QDs is proposed as sensitizers for the determination of Ceftriaxone. The quantum dot nanoparticles were structurally and optically characterized by Ultra Violet-Visible absorption Spectroscopy (UV-vis absorption spectroscopy), Fourier transform infrared spectroscopy (FT-IR spectra) and photoluminescence (PL) emission spectroscopy. High resolution transmission electron microscopy (HRTEM) confirms that the Cys-CdS QDs have a spherical structure with good crystallinity. Therefore, a new simple and selective PL analysis system was developed for the determination of Ceftriaxone (CFX). Under the optimum conditions, The response of l-Cys capped CdS QDs as the probe was linearly proportional to the concentration of Ceftriaxone ions in the range of 1.6×10(-9)-1.1×10(-3)M with a correlation coefficient (R2) of 0.9902. The limit of detection of this system was found to be 1.3nM. This method is simple, sensitive and low cost.
Colloquium: Non-Markovian dynamics in open quantum systems
Breuer, Heinz-Peter; Laine, Elsi-Mari; Piilo, Jyrki; Vacchini, Bassano
2016-04-01
The dynamical behavior of open quantum systems plays a key role in many applications of quantum mechanics, examples ranging from fundamental problems, such as the environment-induced decay of quantum coherence and relaxation in many-body systems, to applications in condensed matter theory, quantum transport, quantum chemistry, and quantum information. In close analogy to a classical Markovian stochastic process, the interaction of an open quantum system with a noisy environment is often modeled phenomenologically by means of a dynamical semigroup with a corresponding time-independent generator in Lindblad form, which describes a memoryless dynamics of the open system typically leading to an irreversible loss of characteristic quantum features. However, in many applications open systems exhibit pronounced memory effects and a revival of genuine quantum properties such as quantum coherence, correlations, and entanglement. Here recent theoretical results on the rich non-Markovian quantum dynamics of open systems are discussed, paying particular attention to the rigorous mathematical definition, to the physical interpretation and classification, as well as to the quantification of quantum memory effects. The general theory is illustrated by a series of physical examples. The analysis reveals that memory effects of the open system dynamics reflect characteristic features of the environment which opens a new perspective for applications, namely, to exploit a small open system as a quantum probe signifying nontrivial features of the environment it is interacting with. This Colloquium further explores the various physical sources of non-Markovian quantum dynamics, such as structured environmental spectral densities, nonlocal correlations between environmental degrees of freedom, and correlations in the initial system-environment state, in addition to developing schemes for their local detection. Recent experiments addressing the detection, quantification, and control of
Coherent manipulation of single quantum systems in the solid state
Childress, Lilian Isabel
2007-12-01
The controlled, coherent manipulation of quantum-mechanical systems is an important challenge in modern science and engineering, with significant applications in quantum information science. Solid-state quantum systems such as electronic spins, nuclear spins, and superconducting islands are among the most promising candidates for realization of quantum bits (qubits). However, in contrast to isolated atomic systems, these solid-state qubits couple to a complex environment which often results in rapid loss of coherence, and, in general, is difficult to understand. Additionally, the strong interactions which make solid-state quantum systems attractive can typically only occur between neighboring systems, leading to difficulties in coupling arbitrary pairs of quantum bits. This thesis presents experimental progress in understanding and controlling the complex environment of a solid-state quantum bit, and theoretical techniques for extending the distance over which certain quantum bits can interact coherently. Coherent manipulation of an individual electron spin associated with a nitrogen-vacancy center in diamond is used to gain insight into its mesoscopic environment. Furthermore, techniques for exploiting coherent interactions between the electron spin and a subset of the environment are developed and demonstrated, leading to controlled interactions with single isolated nuclear spins. The quantum register thus formed by a coupled electron and nuclear spin provides the basis for a theoretical proposal for fault-tolerant long-distance quantum communication with minimal physical resource requirements. Finally, we consider a mechanism for long-distance coupling between quantum dots based on chip-scale cavity quantum electrodynamics.
Preparing ground States of quantum many-body systems on a quantum computer.
Poulin, David; Wocjan, Pawel
2009-04-03
Preparing the ground state of a system of interacting classical particles is an NP-hard problem. Thus, there is in general no better algorithm to solve this problem than exhaustively going through all N configurations of the system to determine the one with lowest energy, requiring a running time proportional to N. A quantum computer, if it could be built, could solve this problem in time sqrt[N]. Here, we present a powerful extension of this result to the case of interacting quantum particles, demonstrating that a quantum computer can prepare the ground state of a quantum system as efficiently as it does for classical systems.
Quasi locality of the GGE in interacting-to-free quenches in relativistic field theories
Bastianello, Alvise
2016-01-01
We study the quench dynamics in continuous relativistic quantum field theory, more specifically the locality properties of the large time stationary state. After a quantum quench in a one-dimensional integrable model, the expectation values of local observables are expected to relax to a Generalised Gibbs Ensemble (GGE), constructed out of the conserved charges of the model. Quenching to a free bosonic theory, it has been shown that the system indeed relaxes to a GGE described by the momentum mode occupation numbers. Here we address the question whether the latter can be equivalently described by a GGE constructed with only local charges. We show that, in marked contrast to the lattice case, this is always impossible in continuous field theories and instead the recently discovered quasilocal charges are necessary. In particular we show that the discrepancy between the exact steady state and the local GGE is clearly manifested as a difference in the large distance behaviour of the two point correlation functio...
Decoherence, delocalization and irreversibility in quantum chaotic systems
Shiokawa, K; Shiokawa, K; Hu, B L
1995-01-01
Decoherence in quantum systems which are classically chaotic is studied. The Arnold cat map and the quantum kicked rotor are chosen as examples of linear and nonlinear chaotic systems. The Feynman-Vernon influence functional formalism is used to study the effect of the environment on the system. It is well-known that quantum coherence can obliterate many chaotic behavior in the corresponding classical system. But interaction with an environment can under general circumstances quickly diminish quantum coherence and reenact many classical chaotic behavior. How effective decoherence works to sustain chaos, and how the resultant behavior qualitatively differs from the quantum picture depend on the coupling of the system with the environment and the spectral density and temperature of the environment. We show how recurrence in the quantum cat map is lost and classical ergodicity is recovered due to the effect of the environment. Quantum coherence and diffusion suppression are instrumental to dynamical localization...
General System theory, Like-Quantum Semantics and Fuzzy Sets
Licata, Ignazio
2006-01-01
It is outlined the possibility to extend the quantum formalism in relation to the requirements of the general systems theory. It can be done by using a quantum semantics arising from the deep logical structure of quantum theory. It is so possible taking into account the logical openness relationship between observer and system. We are going to show how considering the truth-values of quantum propositions within the context of the fuzzy sets is here more useful for systemics . In conclusion we propose an example of formal quantum coherence.
Quantum information storage and state transfer based on spin systems
Song, Z
2004-01-01
The idea of quantum state storage is generalized to describe the coherent transfer of quantum information through a coherent data bus. In this universal framework, we comprehensively review our recent systematical investigations to explore the possibility of implementing the physical processes of quantum information storage and state transfer by using quantum spin systems, which may be an isotropic antiferromagnetic spin ladder system or a ferromagnetic Heisenberg spin chain. Our studies emphasize the physical mechanisms and the fundamental problems behind the various protocols for the storage and transfer of quantum information in solid state systems.
Vink, R L C; Fischer, T; Binder, K
2010-11-01
In systems belonging to the universality class of the random field Ising model, the standard hyperscaling relation between critical exponents does not hold, but is replaced with a modified hyperscaling relation. As a result, standard formulations of finite-size scaling near critical points break down. In this work, the consequences of modified hyperscaling are analyzed in detail. The most striking outcome is that the free-energy cost ΔF of interface formation at the critical point is no longer a universal constant, but instead increases as a power law with system size, ΔF∝L(θ), with θ as the violation of hyperscaling critical exponent and L as the linear extension of the system. This modified behavior facilitates a number of numerical approaches that can be used to locate critical points in random field systems from finite-size simulation data. We test and confirm the approaches on two random field systems in three dimensions, namely, the random field Ising model and the demixing transition in the Widom-Rowlinson fluid with quenched obstacles.
Non-Markovian Dynamics of Quantum Systems
Chruściński, Dariusz; Kossakowski, Andrzej
2011-01-01
We analyze a local approach to the non-Markovian evolution of open quantum systems. It turns out that any dynamical map representing evolution of such a system may be described either by non-local master equation with memory kernel or equivalently by equation which is local in time. The price one pays for the local approach is that the corresponding generator might be highly singular and it keeps the memory about the starting point 't0'. Remarkably, singularities of generator may lead to interesting physical phenomena like revival of coherence or sudden death and revival of entanglement.
Parallel decoherence in composite quantum systems
Indian Academy of Sciences (India)
M Dugići; J Jeknić-Dugić
2012-08-01
For the standard quantum Brownian motion (QBM) model, we point out the occurrence of simultaneous (parallel), mutually irreducible and autonomous decoherence processes. Besides the standard Brownian particle, we show that there is at least another system undergoing the dynamics described by the QBM model. We do this by selecting the two mutually irreducible, global structures (decompositions into subsystems) of the composite system of the QBM model. The generalization of this observation is a new, challenging task in the foundations of the decoherence theory. We do not place our findings in any interpretational context.
Twisted CFT and bilayer Quantum Hall systems
Cristofano, G; Naddeo, A
2003-01-01
We identify the impurity interactions of the recently proposed CFT description of a bilayer Quantum Hall system at filling nu =m/(pm+2) in Mod. Phys. Lett. A 15 (2000) 1679. Such a CFT is obtained by m-reduction on the one layer system, with a resulting pairing symmetry and presence of quasi-holes. For the m=2 case boundary terms are shown to describe an impurity interaction which allows for a localized tunnel of the Kondo problem type. The presence of an anomalous fixed point is evidenced at finite coupling which is unstable with respect to unbalance and flows to a vacuum state with no quasi-holes.
Effective operator formalism for open quantum systems
DEFF Research Database (Denmark)
Reiter, Florentin; Sørensen, Anders Søndberg
2012-01-01
We present an effective operator formalism for open quantum systems. Employing perturbation theory and adiabatic elimination of excited states for a weakly driven system, we derive an effective master equation which reduces the evolution to the ground-state dynamics. The effective evolution...... involves a single effective Hamiltonian and one effective Lindblad operator for each naturally occurring decay process. Simple expressions are derived for the effective operators which can be directly applied to reach effective equations of motion for the ground states. We compare our method...
Optimal state estimation for d-dimensional quantum systems
Bruss, D
1999-01-01
We establish a connection between optimal quantum cloning and optimal state estimation for d-dimensional quantum systems. In this way we derive an upper limit on the fidelity of state estimation for d-dimensional pure quantum states and, furthermore, for generalized inputs supported on the symmetric subspace.
Quantum Sensing of Noisy and Complex Systems under Dynamical Control
Directory of Open Access Journals (Sweden)
Gershon Kurizki
2016-12-01
Full Text Available We review our unified optimized approach to the dynamical control of quantum-probe interactions with noisy and complex systems viewed as thermal baths. We show that this control, in conjunction with tools of quantum estimation theory, may be used for inferring the spectral and spatial characteristics of such baths with high precision. This approach constitutes a new avenue in quantum sensing, dubbed quantum noise spectroscopy.
Quantum Entanglement for Systems of Identical Bosons. I General Theory
Dalton, Bryan; Goold, John; Garraway, Barry; Reid, Margaret
2015-01-01
These two accompanying papers treat two mode entanglement for systems of identical massive bosons and the relationship to spin squeezing and other quantum correlation effects. Entanglement is a key quantum feature of composite systems where the probabilities for joint measurements on the composite sub-systems are no longer determined from measurement probabilities on the separate sub-systems. We focus on the meaning of entanglement, the quantum paradoxes associated with entangled states, and ...
Thermalization and Pseudolocality in Extended Quantum Systems
Doyon, Benjamin
2017-04-01
Recently, it was understood that modified concepts of locality played an important role in the study of extended quantum systems out of equilibrium, in particular in so-called generalized Gibbs ensembles. In this paper, we rigorously study pseudolocal charges and their involvement in time evolutions and in the thermalization process of arbitrary states with strong enough clustering properties. We show that the densities of pseudolocal charges form a Hilbert space, with inner product determined by thermodynamic susceptibilities. Using this, we define the family of pseudolocal states, which are determined by pseudolocal charges. This family includes thermal Gibbs states at high enough temperatures, as well as (a precise definition of) generalized Gibbs ensembles. We prove that the family of pseudolocal states is preserved by finite time evolution, and that, under certain conditions, the stationary state emerging at infinite time is a generalized Gibbs ensemble with respect to the evolution dynamics. If the evolution dynamics does not admit any conserved pseudolocal charges other than the evolution Hamiltonian, we show that any stationary pseudolocal state with respect to these dynamics is a thermal Gibbs state, and that Gibbs thermalization occurs. The framework is that of translation-invariant states on hypercubic quantum lattices of any dimensionality (including quantum chains) and finite-range Hamiltonians, and does not involve integrability.
Advanced Topic: Quasi-Hermitian Quantum Systems
Curtright, Thomas L.; Fairlie, David B.; Zachos, Cosmas K.
2014-11-01
So far, the discussion has limited itself to hermitian operators and systems. However, superficially non-hermitian Hamiltonian quantum systems are also of considerable current interest, especially in the context of PT symmetric models [Ben07, Mos05], although many of the main ideas appeared earlier [SGH92, XA96]. For such systems, the Hilbert space structure is at first sight very different from that for hermitian Hamiltonian systems, inasmuch as the dual wavefunctions are not just the complex conjugates of the wavefunctions, or, equivalently, the Hilbert space metric is not the usual one. While it is possible to keep most of the compact Dirac notation in analyzing such systems, here we work with explicit functions and avoid abstract notation, in the hope to fully expose all the structure, rather than to hide it...
Ravaioli, Emmanuele; Datskov, Vladimir I.; Desbiolles, Vincent; Feuvrier, Jerome; Kirby, Glyn; Maciejewski, Michal; Sperin, Kevin A.; Kate, ten Herman H.J.; Verweij, Arjan P.; Willering, G.
2015-01-01
The recently developed Coupling-Loss-Induced Quench (CLIQ) protection system is a new method for initiating a fast and voluminous transition to the normal state for protecting high energy density superconducting magnets. Its simple and robust electrical design, its lower failure rate, and its more e
Nichols, Kevin Paul; Gardeniers, Han J.G.E.
2007-01-01
A digital microfluidic system based on electrowetting has been developed to facilitate the investigation of pre-steady-state reaction kinetics using rapid quenching and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The device consists of individually ad
Fano Effect and Quantum Entanglement in Hybrid Semiconductor Quantum Dot-Metal Nanoparticle System
Directory of Open Access Journals (Sweden)
Yong He
2017-06-01
Full Text Available In this paper, we review the investigation for the light-matter interaction between surface plasmon field in metal nanoparticle (MNP and the excitons in semiconductor quantum dots (SQDs in hybrid SQD-MNP system under the full quantum description. The exciton-plasmon interaction gives rise to the modified decay rate and the exciton energy shift which are related to the exciton energy by using a quantum transformation method. We illustrate the responses of the hybrid SQD-MNP system to external field, and reveal Fano effect shown in the absorption spectrum. We demonstrate quantum entanglement between two SQD mediated by surface plasmon field. In the absence of a laser field, concurrence of quantum entanglement will disappear after a few ns. If the laser field is present, the steady states appear, so that quantum entanglement produced will reach a steady-state entanglement. Because one of all optical pathways to induce Fano effect refers to the generation of quantum entangled states, It is shown that the concurrence of quantum entanglement can be obtained by observation for Fano effect. In a hybrid system including two MNP and a SQD, because the two Fano quantum interference processes share a segment of all optical pathways, there is correlation between the Fano effects of the two MNP. The investigations for the light-matter interaction in hybrid SQD-MNP system can pave the way for the development of the optical processing devices and quantum information based on the exciton-plasmon interaction.
Fano Effect and Quantum Entanglement in Hybrid Semiconductor Quantum Dot-Metal Nanoparticle System
He, Yong; Zhu, Ka-Di
2017-01-01
In this paper, we review the investigation for the light-matter interaction between surface plasmon field in metal nanoparticle (MNP) and the excitons in semiconductor quantum dots (SQDs) in hybrid SQD-MNP system under the full quantum description. The exciton-plasmon interaction gives rise to the modified decay rate and the exciton energy shift which are related to the exciton energy by using a quantum transformation method. We illustrate the responses of the hybrid SQD-MNP system to external field, and reveal Fano effect shown in the absorption spectrum. We demonstrate quantum entanglement between two SQD mediated by surface plasmon field. In the absence of a laser field, concurrence of quantum entanglement will disappear after a few ns. If the laser field is present, the steady states appear, so that quantum entanglement produced will reach a steady-state entanglement. Because one of all optical pathways to induce Fano effect refers to the generation of quantum entangled states, It is shown that the concurrence of quantum entanglement can be obtained by observation for Fano effect. In a hybrid system including two MNP and a SQD, because the two Fano quantum interference processes share a segment of all optical pathways, there is correlation between the Fano effects of the two MNP. The investigations for the light-matter interaction in hybrid SQD-MNP system can pave the way for the development of the optical processing devices and quantum information based on the exciton-plasmon interaction. PMID:28632165
Fano Effect and Quantum Entanglement in Hybrid Semiconductor Quantum Dot-Metal Nanoparticle System.
He, Yong; Zhu, Ka-Di
2017-06-20
In this paper, we review the investigation for the light-matter interaction between surface plasmon field in metal nanoparticle (MNP) and the excitons in semiconductor quantum dots (SQDs) in hybrid SQD-MNP system under the full quantum description. The exciton-plasmon interaction gives rise to the modified decay rate and the exciton energy shift which are related to the exciton energy by using a quantum transformation method. We illustrate the responses of the hybrid SQD-MNP system to external field, and reveal Fano effect shown in the absorption spectrum. We demonstrate quantum entanglement between two SQD mediated by surface plasmon field. In the absence of a laser field, concurrence of quantum entanglement will disappear after a few ns. If the laser field is present, the steady states appear, so that quantum entanglement produced will reach a steady-state entanglement. Because one of all optical pathways to induce Fano effect refers to the generation of quantum entangled states, It is shown that the concurrence of quantum entanglement can be obtained by observation for Fano effect. In a hybrid system including two MNP and a SQD, because the two Fano quantum interference processes share a segment of all optical pathways, there is correlation between the Fano effects of the two MNP. The investigations for the light-matter interaction in hybrid SQD-MNP system can pave the way for the development of the optical processing devices and quantum information based on the exciton-plasmon interaction.
The transition to chaos conservative classical systems and quantum manifestations
Reichl, Linda E
2004-01-01
This book provides a thorough and comprehensive discussion of classical and quantum chaos theory for bounded systems and for scattering processes Specific discussions include • Noether’s theorem, integrability, KAM theory, and a definition of chaotic behavior • Area-preserving maps, quantum billiards, semiclassical quantization, chaotic scattering, scaling in classical and quantum dynamics, dynamic localization, dynamic tunneling, effects of chaos in periodically driven systems and stochastic systems • Random matrix theory and supersymmetry The book is divided into several parts Chapters 2 through 4 deal with the dynamics of nonlinear conservative classical systems Chapter 5 and several appendices give a thorough grounding in random matrix theory and supersymmetry techniques Chapters 6 and 7 discuss the manifestations of chaos in bounded quantum systems and open quantum systems respectively Chapter 8 focuses on the semiclassical description of quantum systems with underlying classical chaos, and Chapt...
On the notion of a macroscopic quantum system
Khrenikov, A Yu
2004-01-01
We analyse the notion of macroscopic quantum system from the point of view of the statistical structure of quantum theory. We come to conclusion that the presence of interference of probabilities should be used the main characteristic of quantumness (in the opposition to N. Bohr who permanently emphasized the crucial role of quantum action). In the light of recent experiments with statistical ensembles of people who produced interference of probabilities for special pairs of questions (which can be considered as measurements on people) human being should be considered as a macroscopic quantum system. There is also discussed relation with experiments of A. Zeilinger on interference of probabilities for macromoleculas.
Environment-assisted quantum transport in ordered systems
Kassal, Ivan
2012-01-01
Noise-assisted transport in quantum systems occurs when quantum time-evolution and decoherence conspire to produce a transport efficiency that is higher than what would be seen in either the purely quantum or purely classical cases. It has been understood as the suppression of coherent quantum localization through noise, which brings detuned quantum levels into resonance and thus facilitates transport. We report several new mechanisms of environment-assisted transport in ordered systems, in which there is no localization to be overcome.
Hamiltonian truncation approach to quenches in the Ising field theory
Directory of Open Access Journals (Sweden)
T. Rakovszky
2016-10-01
Full Text Available In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1+1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.
Hamiltonian truncation approach to quenches in the Ising field theory
Rakovszky, T.; Mestyán, M.; Collura, M.; Kormos, M.; Takács, G.
2016-10-01
In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1 + 1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.
Quantum MIMO n-Systems and Conditions for Stability
Mansourbeigi, Seyed M H
2009-01-01
In this paper we present some conditions for the (strong) stabilizability of an n-D Quantum MIMO system P(X). It contains two parts. The first part is to introduce the n-D Quantum MIMO systems where the coefficients vary in the algebra of Q-meromorphic functions. Then we introduce some conditions for the stabilizability of these systems. The second part is to show that this Quantum system has the n-D system as its quantum limit and the results for the SISO,SIMO,MISO,MIMO are obtained again as special cases.
Measuring entanglement entropy in a quantum many-body system.
Islam, Rajibul; Ma, Ruichao; Preiss, Philipp M; Tai, M Eric; Lukin, Alexander; Rispoli, Matthew; Greiner, Markus
2015-12-01
Entanglement is one of the most intriguing features of quantum mechanics. It describes non-local correlations between quantum objects, and is at the heart of quantum information sciences. Entanglement is now being studied in diverse fields ranging from condensed matter to quantum gravity. However, measuring entanglement remains a challenge. This is especially so in systems of interacting delocalized particles, for which a direct experimental measurement of spatial entanglement has been elusive. Here, we measure entanglement in such a system of itinerant particles using quantum interference of many-body twins. Making use of our single-site-resolved control of ultracold bosonic atoms in optical lattices, we prepare two identical copies of a many-body state and interfere them. This enables us to directly measure quantum purity, Rényi entanglement entropy, and mutual information. These experiments pave the way for using entanglement to characterize quantum phases and dynamics of strongly correlated many-body systems.
Linear dynamical quantum systems analysis, synthesis, and control
Nurdin, Hendra I
2017-01-01
This monograph provides an in-depth treatment of the class of linear-dynamical quantum systems. The monograph presents a detailed account of the mathematical modeling of these systems using linear algebra and quantum stochastic calculus as the main tools for a treatment that emphasizes a system-theoretic point of view and the control-theoretic formulations of quantum versions of familiar problems from the classical (non-quantum) setting, including estimation and filtering, realization theory, and feedback control. Both measurement-based feedback control (i.e., feedback control by a classical system involving a continuous-time measurement process) and coherent feedback control (i.e., feedback control by another quantum system without the intervention of any measurements in the feedback loop) are treated. Researchers and graduates studying systems and control theory, quantum probability and stochastics or stochastic control whether from backgrounds in mechanical or electrical engineering or applied mathematics ...
The Dalton quantum chemistry program system
DEFF Research Database (Denmark)
Aidas, Kestutis; Angeli, C.; Bak, K.L.
2014-01-01
Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self-consistent-field, Møller–Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide vari......-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from http://www.daltonprogram.org for a number of UNIX platforms....
Blockspin Cluster Algorithms for Quantum Spin Systems
Wiese, U J
1992-01-01
Cluster algorithms are developed for simulating quantum spin systems like the one- and two-dimensional Heisenberg ferro- and anti-ferromagnets. The corresponding two- and three-dimensional classical spin models with four-spin couplings are maped to blockspin models with two-blockspin interactions. Clusters of blockspins are updated collectively. The efficiency of the method is investigated in detail for one-dimensional spin chains. Then in most cases the new algorithms solve the problems of slowing down from which standard algorithms are suffering.
Quantum-like behavior without quantum physics I : Kinematics of neural-like systems.
Selesnick, S A; Rawling, J P; Piccinini, Gualtiero
2017-07-13
Recently there has been much interest in the possible quantum-like behavior of the human brain in such functions as cognition, the mental lexicon, memory, etc., producing a vast literature. These studies are both empirical and theoretical, the tenets of the theory in question being mainly, and apparently inevitably, those of quantum physics itself, for lack of other arenas in which quantum-like properties are presumed to obtain. However, attempts to explain this behavior on the basis of actual quantum physics going on at the atomic or molecular level within some element of brain or neuronal anatomy (other than the ordinary quantum physics that underlies everything), do not seem to survive much scrutiny. Moreover, it has been found empirically that the usual physics-like Hilbert space model seems not to apply in detail to human cognition in the large. In this paper we lay the groundwork for a theory that might explain the provenance of quantum-like behavior in complex systems whose internal structure is essentially hidden or inaccessible. The approach is via the logic obeyed by these systems which is similar to, but not identical with, the logic obeyed by actual quantum systems. The results reveal certain effects in such systems which, though quantum-like, are not identical to the kinds of quantum effects found in physics. These effects increase with the size of the system.
Validation of Quench Simulation and Simulation of the TWIN Solenoid
Pots, Rosalinde Hendrika
2015-01-01
For the Future Circular Collider at CERN a multi-purpose detector is proposed. The 6T TWIN Solenoid, a very large magnet system with a stored energy of 53 GJ, is being designed. It is important to protect the magnet against quenches in the system. Therefore several existing quench protection systems are evaluated and simulations have be performed on quenches in the TWIN Solenoid. The simulations on quenches in the TWIN Solenoid have been performed with promising results; the hotspot temperatures do not exceed 120 K and layer to layer voltages stay below 500 V. Adding quench heaters to the system might improve the quench protection system further.
Limit theorems for dilute quantum systems leading to quantum poisson processes
Alicki, Robert; Rudnicki, Sławomir; Sadowski, Sławomir
1993-12-01
The limit theorems for sums of independent or correlated operators representing observables of dilute quantum systems and leading to quantum Poisson processes are proved. Examples of systems of unstable particles and a Fermi lattice gas are discussed. For the latter, relations between low density limit and central limit are given.
Nonlinear Dynamics and Quantum Transport in Small Systems
2012-02-22
Dynamics and Quantum Transport in Small Systems.” The PI is Ying-Cheng Lai from Arizona State University. The duration of the project was 12/1/2008...military systems may contain some graphene components. To understand various fundamental aspects of quantum transport dynamics is key to developing...conductance fluctuations, not seen previously in any quantum transport systems. This phenomenon has profound implications to the development of graphene
Relaxation and thermalization of nonequilibrium quantum systems in the semiclassical limit
Hipolito, Rafael Stockschneider
We discuss the development and application of semiclassical techniques to study dynamics and relaxation in quantum mechanical systems out of equilibrium, relevant to ultracold atomic gases. Due to the unprecedented amount of control in these systems, experimentalists have a lot of freedom in designing Hamiltonians, including the spatial dimension. Another advantage present in these systems is the fact that time scales are slow enough, in contradistinction with usual condensed matter systems, so that it is possible to follow nonequilibrium dynamics and relaxation after quantum quenches. The advent of these experiments has motivated us to further understand these systems. With this goal in mind, we apply a semiclassical phase space technique called Truncated Wigner Approximation (TWA) to study dynamics in the weakly interacting, semiclassical limit. In our study, we will further confine ourselves to one dimensional systems where thermalization is poorly understood due to the fact that generic one dimensional Hamiltonians lie close to integrable models. Due to the peculiarity of systems in low dimensions, such as the prohibition of true long range order, these systems relax in an interesting way, and we generically find the emergence of long-lived metastable states. In particular, we find it is possible to design Hamiltonians that share features with the Fermi-Pasta-Ulam model, and these systems relax to a metastable state where different momentum mode energies live at different temperatures.
Characterizing and quantifying frustration in quantum many-body systems.
Giampaolo, S M; Gualdi, G; Monras, A; Illuminati, F
2011-12-23
We present a general scheme for the study of frustration in quantum systems. We introduce a universal measure of frustration for arbitrary quantum systems and we relate it to a class of entanglement monotones via an exact inequality. If all the (pure) ground states of a given Hamiltonian saturate the inequality, then the system is said to be inequality saturating. We introduce sufficient conditions for a quantum spin system to be inequality saturating and confirm them with extensive numerical tests. These conditions provide a generalization to the quantum domain of the Toulouse criteria for classical frustration-free systems. The models satisfying these conditions can be reasonably identified as geometrically unfrustrated and subject to frustration of purely quantum origin. Our results therefore establish a unified framework for studying the intertwining of geometric and quantum contributions to frustration.
Statistical mechanics of quantum-classical systems with holonomic constraints.
Sergi, Alessandro
2006-01-14
The statistical mechanics of quantum-classical systems with holonomic constraints is formulated rigorously by unifying the classical Dirac bracket and the quantum-classical bracket in matrix form. The resulting Dirac quantum-classical theory, which conserves the holonomic constraints exactly, is then used to formulate time evolution and statistical mechanics. The correct momentum-jump approximation for constrained systems arises naturally from this formalism. Finally, in analogy with what was found in the classical case, it is shown that the rigorous linear-response function of constrained quantum-classical systems contains nontrivial additional terms which are absent in the response of unconstrained systems.
Probability representation of kinetic equation for open quantum system
Man'ko, V I; Shchukin, E V
2003-01-01
The tomographic probability distribution is used to decribe the kinetic equations for open quantum systems. Damped oscillator is studied. Purity parameter evolution for different damping regime is considered.
Asymptotically open quantum systems; Asymptotisch offene Quantensysteme
Energy Technology Data Exchange (ETDEWEB)
Westrich, M.
2008-04-15
In the present thesis we investigate the structure of time-dependent equations of motion in quantum mechanics.We start from two coupled systems with an autonomous equation of motion. A limit, in which the dynamics of one of the two systems has a decoupled evolution and imposes a non-autonomous evolution for the second system is identified. A result due to K. Hepp that provides a classical limit for dynamics turns out to be part and parcel for this limit and is generalized in our work. The method introduced by J.S. Howland for the solution of the time-dependent Schroedinger equation is interpreted as such a limit. Moreover, we associate our limit with the modern theory of quantization. (orig.)
Nonequilibrium critical scaling in quantum thermodynamics
Bayat, Abolfazl; Apollaro, Tony J. G.; Paganelli, Simone; De Chiara, Gabriele; Johannesson, Henrik; Bose, Sougato; Sodano, Pasquale
2016-05-01
The emerging field of quantum thermodynamics is contributing important results and insights into archetypal many-body problems, including quantum phase transitions. Still, the question whether out-of-equilibrium quantities, such as fluctuations of work, exhibit critical scaling after a sudden quench in a closed system has remained elusive. Here, we take a novel approach to the problem by studying a quench across an impurity quantum critical point. By performing density matrix renormalization group computations on the two-impurity Kondo model, we are able to establish that the irreversible work produced in a quench exhibits finite-size scaling at quantum criticality. This scaling faithfully predicts the equilibrium critical exponents for the crossover length and the order parameter of the model, and, moreover, implies an exponent for the rescaled irreversible work. By connecting the irreversible work to the two-impurity spin correlation function, our findings can be tested experimentally.
Quantum simulation of disordered systems with cold atoms
Garreau, Jean-Claude
2017-01-01
This paper reviews the physics of quantum disorder in relation with a series of experiments using laser-cooled atoms exposed to "kicks" of a standing wave, realizing a paradigmatic model of quantum chaos, the kicked rotor. This dynamical system can be mapped onto a tight-binding Hamiltonian with pseudo-disorder, formally equivalent to the Anderson model of quantum disorder, with quantum chaos playing the role of disorder. This provides a very good quantum simulator for the Anderson physics. xml:lang="fr"
Topological defects from doping and quenched disorder in artificial ice systems
Energy Technology Data Exchange (ETDEWEB)
Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, A [BABES-BOLYAI UNIV
2010-01-01
We examine the ice-rule obeying and ice-rule breaking vertices in an artificial spin ice system created using magnetic vortices in type-II superconductors with nanostructured pinning arrays. We show that this system can be doped by changing the external field to move the number of vortices away from commensurability and create sites that contain two or zero vortices. For a square ice, the doping leads to the formation of a grain boundary of vertices that do not obey the ice rules. In commensurate systems where the ice rules are obeyed, we can introduce random disorder at the individual pinning sites to create regions where vortices may not be able to flip from one side of the trap to another. For weak disorder, all of the vertices still obey the ice rules, while at intermediate levels of disorder we find grain boundaries of vertices which do not obey the ice rules. For strong disorder it is possible to create isolated paired vertices that do not obey the ice rules. In summary, we have shown that an artificial square ice can be created using vortices in a type-II superconductor interacting with a periodic array of pinning sites where each site has a double well potential. By defining the direction of the effective spin according to the side of the double well occupied by the vortex, we find that this system obeys the ice rules for square ice. We add disorder to the system in the form of randomness of the height of the potential barrier at the center of the well, and obtain vertex configurations using a rotating drive protocol which is similar to the shaking ac magnetic field used in nanomagnetic systems. For weak disorder the entire system still obeys the square ice rules. For intermediate disorder, ice-rule breaking vertices appear and form grain boundaries, while for strong disorder there are both gain boundaries and isolated paired defects. In a system with uniform potential barrier heights, we introduce disorder by moving away from commensurability and creating
New, coupling loss induced, quench protection system for superconducting accelerator magnets
Ravaioli, E.; Datskov, V.I.; Giloux, C.; Kirby, G.; Kate, ten H.H.J.; Verweij, A.P.
2014-01-01
A new and promising method for the protection of superconducting high-field magnets is developed and tested on the so-called MQXC quadrupole magnet in the CERN magnet test facility. The method relies on a capacitive discharge system inducing during a few periods an oscillation of the transport curre
Deformed oscillator algebras for two dimensional quantum superintegrable systems
Bonatsos, Dennis; Kokkotas, K D; Bonatsos, Dennis
1994-01-01
Quantum superintegrable systems in two dimensions are obtained from their classical counterparts, the quantum integrals of motion being obtained from the corresponding classical integrals by a symmetrization procedure. For each quantum superintegrable systema deformed oscillator algebra, characterized by a structure function specific for each system, is constructed, the generators of the algebra being functions of the quantum integrals of motion. The energy eigenvalues corresponding to a state with finite dimensional degeneracy can then be obtained in an economical way from solving a system of two equations satisfied by the structure function, the results being in agreement to the ones obtained from the solution of the relevant Schrodinger equation. The method shows how quantum algebraic techniques can simplify the study of quantum superintegrable systems, especially in two dimensions.
Tagit, Oya; Tomczak, Nikodem; Benetti, Edmondo M.; Cesa, Yanina; Blum, Christian; Subramaniam, Vinod; Herek, Jennifer L.; Vancso, G. Julius
2009-01-01
A thermo-responsive polymer/quantum dot platform based on poly(N-isopropyl acrylamide) (PNIPAM) brushes 'grafted from' a gold substrate and quantum dots (QDs) covalently attached to the PNIPAM layer is presented. The PNIPAM brushes are grafted from the gold surface using an iniferter-initiated contr
Gurarie, V
2004-01-01
We examine two-dimensional conformal field theories (CFTs) at central charge c=0. These arise typically in the description of critical systems with quenched disorder, but also in other contexts including dilute self-avoiding polymers and percolation. We show that such CFTs must in general possess, in addition to their stress energy tensor T(z), an extra field whose holomorphic part, t(z), has conformal weight two. The singular part of the Operator Product Expansion (OPE) between T(z) and t(z) is uniquely fixed up to a single number b, defining a new `anomaly' which is a characteristic of any c=0 CFT, and which may be used to distinguish between different such CFTs. The extra field t(z) is not primary (unless b=0), and is a so-called `logarithmic operator' except in special cases which include affine (Kac-Moody) Lie-super current algebras. The number b controls the question of whether Virasoro null-vectors arising at certain conformal weights contained in the c=0 Kac table may be set to zero or not, in these n...
Suh, Hwa-Jin; Lee, Kyung-Seok; Kim, Seong-Ryul; Shin, Myoung-Ho; Park, Sanggyu; Park, Shin
2011-02-07
The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effect and total phenolic contents were evaluated for the screening of singlet oxygen ((1)O(2)) quenching efficacy of various seed extracts from Rumex crispus L. The butanol and ethyl-acetate extracts displayed remarkable effect of DPPH as compared to positive control ascorbic acid. The concentrations (QC(50)) of butanol and ethyl-acetate extracts required to exert 50% reducing effect on (1)O(2) were found to be 116 and 82 μg mL(-1), respectively. Both extracts were also found to protect the in vitro biological system from the detrimental effect of (1)O(2) on type II photosensitization in Escherichia coli, red blood cell, lactate dehydrogenase and histidine. Among all the tested extracts, the ethyl-acetate and butanol extracts contained higher amount of total phenolic contents. The results suggest that our study may contribute to the development of new bioactive products with potential applications to reduce photo-produced oxidative stress involving reactive oxygen species in living organisms. Copyright © 2010 Elsevier B.V. All rights reserved.
Coulomb crystallization in classical and quantum systems
Bonitz, Michael
2007-11-01
Coulomb crystallization occurs in one-component plasmas when the average interaction energy exceeds the kinetic energy by about two orders of magnitude. A simple road to reach such strong coupling consists in using external confinement potentials the strength of which controls the density. This has been succsessfully realized with ions in traps and storage rings and also in dusty plasma. Recently a three-dimensional spherical confinement could be created [1] which allows to produce spherical dust crystals containing concentric shells. I will give an overview on our recent results for these ``Yukawa balls'' and compare them to experiments. The shell structure of these systems can be very well explained by using an isotropic statically screened pair interaction. Further, the thermodynamic properties of these systems, such as the radial density distribution are discussed based on an analytical theory [3]. I then will discuss Coulomb crystallization in trapped quantum systems, such as mesoscopic electron and electron hole plasmas in coupled layers [4,5]. These systems show a very rich correlation behavior, including liquid and solid like states and bound states (excitons, biexcitons) and their crystals. On the other hand, also collective quantum and spin effects are observed, including Bose-Einstein condensation and superfluidity of bound electron-hole pairs [4]. Finally, I consider Coulomb crystallization in two-component neutral plasmas in three dimensions. I discuss the necessary conditions for crystals of heavy charges to exist in the presence of a light component which typically is in the Fermi gas or liquid state. It can be shown that their exists a critical ratio of the masses of the species of the order of 80 [5] which is confirmed by Quantum Monte Carlo simulations [6]. Familiar examples are crystals of nuclei in the core of White dwarf stars, but the results also suggest the existence of other crystals, including proton or α-particle crystals in dense matter
Work on the LHC new Quench Protection System (nQPS), January 2010
Maximilien Brice
2010-01-01
Teams working on improving the electrical reliability of the connection between the Instrumentation Feedthrough Systems (IFS) on the magnets and the nQPS equipment. These operations are necessary to ensure that higher currents can be safely handled. Wearing of helmets in the LHC tunnel is obligatory However, people performing delicate tasks at a fixed position where there is no danger of falling objects are authorised to remove them for the duration of their work.
Device-independent certification of high-dimensional quantum systems.
D'Ambrosio, Vincenzo; Bisesto, Fabrizio; Sciarrino, Fabio; Barra, Johanna F; Lima, Gustavo; Cabello, Adán
2014-04-11
An important problem in quantum information processing is the certification of the dimension of quantum systems without making assumptions about the devices used to prepare and measure them, that is, in a device-independent manner. A crucial question is whether such certification is experimentally feasible for high-dimensional quantum systems. Here we experimentally witness in a device-independent manner the generation of six-dimensional quantum systems encoded in the orbital angular momentum of single photons and show that the same method can be scaled, at least, up to dimension 13.
关于湿法熄焦系统中水锤现象防护的比较%Measures for water hammer prevention in wet quenching system
Institute of Scientific and Technical Information of China (English)
张春才; 张晓光
2014-01-01
介绍了水锤现象的成因、危害、机理及防护措施，通过对比分析国内几种典型湿法熄焦工艺中水锤现象的防护措施，发现在熄焦水泵出口选用缓闭止回阀，在熄焦水输送管道中部选用自动液力阀，可防止湿法熄焦系统中水锤现象发生。%With description of the cause , harmfulness , mechanism and prevention measures against water hammer , and by analyzing several typical measures for water hammer prevention in wet quenching system ,this paper concluded that delay-close check valve can be selected at the outlet of quenching pump and automatic hydraulic pump can be used on the pipeline carrying quenching water so that the water hammer can be effectively avoided in the wet quenching process .
Quantum dynamics of bio-molecular systems in noisy environments
Huelga S.F.; Plenio M.B.
2012-01-01
We discuss three different aspects of the quantum dynamics of bio-molecular systems and more generally complex networks in the presence of strongly coupled environments. Firstly, we make a case for the systematic study of fundamental structural elements underlying the quantum dynamics of these systems, identify such elements and explore the resulting interplay of quantum dynamics and environmental decoherence. Secondly, we critically examine some existing approaches to the numerical descripti...
Capacities of linear quantum optical systems
Lupo, Cosmo; Giovannetti, Vittorio; Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth
2012-06-01
A wide variety of communication channels employ the quantized electromagnetic field to convey information. Their communication capacity crucially depends on losses associated to spatial characteristics of the channel such as diffraction and antenna design. Here we focus on the communication via a finite pupil, showing that diffraction is formally described as a memory channel. By exploiting this equivalence we then compute the communication capacity of an optical refocusing system, modeled as a converging lens. Even though loss of information originates from the finite pupil of the lens, we show that the presence of the refocusing system can substantially enhance the communication capacity. We mainly concentrate on communication of classical information, the extension to quantum information being straightforward.
Capacities of linear quantum optical systems
Lupo, Cosmo; Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth
2012-01-01
A wide variety of communication channels employ the quantized electromagnetic field to convey information. Their communication capacity crucially depends on losses associated to spatial characteristics of the channel such as diffraction and antenna design. Here we focus on the communication via a finite pupil, showing that diffraction is formally described as a memory channel. By exploiting this equivalence we then compute the communication capacity of an optical refocusing system, modeled as a converging lens. Even though loss of information originates from the finite pupil of the lens, we show that the presence of the refocusing system can substantially enhance the communication capacity. We mainly concentrate on communication of classical information, the extension to quantum information being straightforward.
Phase transitions in open quantum systems
Jung, C; Rotter, I
1999-01-01
We consider the behaviour of open quantum systems in dependence on the coupling to one decay channel by introducing the coupling parameter $\\alpha$ being proportional to the average degree of overlapping. Under critical conditions, a reorganization of the spectrum takes place which creates a bifurcation of the time scales with respect to the lifetimes of the resonance states. We derive analytically the conditions under which the reorganization process can be understood as a second-order phase transition and illustrate our results by numerical investigations. The conditions are fulfilled e.g. for a picket fence with equal coupling of the states to the continuum. Energy dependencies within the system are included. We consider also the generic case of an unfolded Gaussian Orthogonal Ensemble. In all these cases, the reorganization of the spectrum occurs at the critical value $\\alpha_{crit}$ of the control parameter globally over the whole energy range of the spectrum. All states act cooperatively.
Relating the quantum mechanics of discrete systems to standard canonical quantum mechanics
Hooft, Gerard t
2012-01-01
Discrete quantum mechanics is here defined to be a quantum theory of wave functions defined on integers P_i and Q_i, while canonical quantum mechanics is assumed to be based on wave functions on the real numbers, R^n. We study reversible mappings from the position operators q_i and their quantum canonical operators p_i of a canonical theory, onto the discrete, commuting operators Q_i and P_i. In this paper we are particularly interested in harmonic oscillators. In the discrete system, these t...
Quantum statistical gravity: time dilation due to local information in many-body quantum systems
Sels, Dries; Wouters, Michiel
2017-08-01
We propose a generic mechanism for the emergence of a gravitational potential that acts on all classical objects in a quantum system. Our conjecture is based on the analysis of mutual information in many-body quantum systems. Since measurements in quantum systems affect the surroundings through entanglement, a measurement at one position reduces the entropy in its neighbourhood. This reduction in entropy can be described by a local temperature, that is directly related to the gravitational potential. A crucial ingredient in our argument is that ideal classical mechanical motion occurs at constant probability. This definition is motivated by the analysis of entropic forces in classical systems.
Efficient numerical solution of excitation number conserving quantum systems
Zhang, Zheyong; Ding, Jianping; Wang, Hui-Tian
2017-08-01
A system composed of a harmonic oscillator coupled to a two-level atom is one of the quantum systems, which can be completely solved. Although this system is simple, it is never a easy work for the quantum calculations, especially when the system consists of many such simple constituent parts. In this paper, we present a programming method, by which the calculation tasks for the matrix representation of the Hamiltonian of system can be automatically fulfilled. Coupled-cavity array systems are used to demonstrate our programming method. Some quantum properties of these systems are also discussed.
Stroncik, Nicole A.; Klügel, Andreas; Hansteen, Thor H.
2009-05-01
A thermobarometric and petrologic study of basanites erupted from young volcanic cones along the submarine portions of the three El Hierro rift zones (NE-Rift, NW-Rift and S-Ridge) has been performed to reconstruct magma plumbing and storage beneath the island. Mineral-melt thermobarometry applied to naturally quenched glass and clinopyroxene rims yields pressures ranging from 350 to 1070 MPa with about 80% of the calculated pressures being in the range of 600-800 MPa. This corresponds to a depth range of 19-26 km, implying that the main level of final crystal fractionation is within the uppermost mantle. No systematic dependence between sample locality and fractionation pressures could be observed. Olivine and clinopyroxene crystals in the rocks are complexly zoned and have, on an inter-sample as well as on an intra-sample scale, highly variable core and rim compositions. This can best be explained by mixing of multiply saturated (olivine, magnetite, clinopyroxene, ilmenite), moderately evolved magmas with more mafic magmas being either only saturated with olivine + spinel or with olivine + spinel + clinopyroxene. The inter-sample differences indicate derivation from small, isolated magma chambers which have undergone distinct fractionation and mixing histories. This is in contrast to oceanic intraplate volcanoes situated on plumes with high melt supply rates, e.g. Kilauea Volcano (Hawaii), where magma is mainly transported through a central conduit system and stored in a shallow magma chamber prior to injection into the rift zones. The plumbing system beneath El Hierro rather resembles the magma storage systems beneath, e.g. Madeira or La Palma, indicating that small, intermittent magma chambers might be a common feature of oceanic islands fed by plumes with relatively low fluxes, which results in only limited and periodic magma supply.
Quantum algorithm for linear systems of equations.
Harrow, Aram W; Hassidim, Avinatan; Lloyd, Seth
2009-10-09
Solving linear systems of equations is a common problem that arises both on its own and as a subroutine in more complex problems: given a matrix A and a vector b(-->), find a vector x(-->) such that Ax(-->) = b(-->). We consider the case where one does not need to know the solution x(-->) itself, but rather an approximation of the expectation value of some operator associated with x(-->), e.g., x(-->)(dagger) Mx(-->) for some matrix M. In this case, when A is sparse, N x N and has condition number kappa, the fastest known classical algorithms can find x(-->) and estimate x(-->)(dagger) Mx(-->) in time scaling roughly as N square root(kappa). Here, we exhibit a quantum algorithm for estimating x(-->)(dagger) Mx(-->) whose runtime is a polynomial of log(N) and kappa. Indeed, for small values of kappa [i.e., poly log(N)], we prove (using some common complexity-theoretic assumptions) that any classical algorithm for this problem generically requires exponentially more time than our quantum algorithm.
Quantum Computing in Fock Space Systems
Berezin, Alexander A.
1997-04-01
Fock space system (FSS) has unfixed number (N) of particles and/or degrees of freedom. In quantum computing (QC) main requirement is sustainability of coherent Q-superpositions. This normally favoured by low noise environment. High excitation/high temperature (T) limit is hence discarded as unfeasible for QC. Conversely, if N is itself a quantized variable, the dimensionality of Hilbert basis for qubits may increase faster (say, N-exponentially) than thermal noise (likely, in powers of N and T). Hence coherency may win over T-randomization. For this type of QC speed (S) of factorization of long integers (with D digits) may increase with D (for 'ordinary' QC speed polynomially decreases with D). This (apparent) paradox rests on non-monotonic bijectivity (cf. Georg Cantor's diagonal counting of rational numbers). This brings entire aleph-null structurality ("Babylonian Library" of infinite informational content of integer field) to superposition determining state of quantum analogue of Turing machine head. Structure of integer infinititude (e.g. distribution of primes) results in direct "Platonic pressure" resembling semi-virtual Casimir efect (presure of cut-off vibrational modes). This "effect", the embodiment of Pythagorean "Number is everything", renders Godelian barrier arbitrary thin and hence FSS-based QC can in principle be unlimitedly efficient (e.g. D/S may tend to zero when D tends to infinity).
Emulation of complex open quantum systems using superconducting qubits
Mostame, Sarah; Huh, Joonsuk; Kreisbeck, Christoph; Kerman, Andrew J.; Fujita, Takatoshi; Eisfeld, Alexander; Aspuru-Guzik, Alán
2017-02-01
With quantum computers being out of reach for now, quantum simulators are alternative devices for efficient and accurate simulation of problems that are challenging to tackle using conventional computers. Quantum simulators are classified into analog and digital, with the possibility of constructing "hybrid" simulators by combining both techniques. Here we focus on analog quantum simulators of open quantum systems and address the limit that they can beat classical computers. In particular, as an example, we discuss simulation of the chlorosome light-harvesting antenna from green sulfur bacteria with over 250 phonon modes coupled to each electronic state. Furthermore, we propose physical setups that can be used to reproduce the quantum dynamics of a standard and multiple-mode Holstein model. The proposed scheme is based on currently available technology of superconducting circuits consist of flux qubits and quantum oscillators.
Hybrid quantum systems with ultracold spins and optomechanics
Shaffer, Airlia; Patil, Yogesh Sharad; Cheung, Hil F. H.; Wang, Ke; Date, Aditya; Schwab, Keith; Meystre, Pierre; Vengalattore, Mukund
2016-05-01
Linear cavity optomechanics has enabled radiation pressure cooling and sensing of mechanical resonators at the quantum limits. However, exciting and unrealized avenues such as generating massive macroscopic nonclassical states, quantum signal transduction, and phonon-based manybody physics each require strong, nonlinear interactions. In our group, we are exploring three approaches to realizing strong optomechanical nonlinearities - i. using atomically thin graphene membranes, ii. coupling optomechanical systems with ultracold atomic spins, and iii. using microtoroidal optomechanical resonators strongly coupled to atoms trapped in their evanescent fields. We describe our progress in each of these efforts and discuss ongoing studies on various aspects of quantum enhanced metrology, nonequilibrium dynamics of open quantum systems and quantum transduction using these novel hybrid quantum systems. This work is supported by the DARPA QuASAR program through a Grant from the ARO.
Software Systems for High-performance Quantum Computing
Energy Technology Data Exchange (ETDEWEB)
Humble, Travis S [ORNL; Britt, Keith A [ORNL
2016-01-01
Quantum computing promises new opportunities for solving hard computational problems, but harnessing this novelty requires breakthrough concepts in the design, operation, and application of computing systems. We define some of the challenges facing the development of quantum computing systems as well as software-based approaches that can be used to overcome these challenges. Following a brief overview of the state of the art, we present models for the quantum programming and execution models, the development of architectures for hybrid high-performance computing systems, and the realization of software stacks for quantum networking. This leads to a discussion of the role that conventional computing plays in the quantum paradigm and how some of the current challenges for exascale computing overlap with those facing quantum computing.
Correlation Functions in Open Quantum-Classical Systems
Directory of Open Access Journals (Sweden)
Chang-Yu Hsieh
2013-12-01
Full Text Available Quantum time correlation functions are often the principal objects of interest in experimental investigations of the dynamics of quantum systems. For instance, transport properties, such as diffusion and reaction rate coefficients, can be obtained by integrating these functions. The evaluation of such correlation functions entails sampling from quantum equilibrium density operators and quantum time evolution of operators. For condensed phase and complex systems, where quantum dynamics is difficult to carry out, approximations must often be made to compute these functions. We present a general scheme for the computation of correlation functions, which preserves the full quantum equilibrium structure of the system and approximates the time evolution with quantum-classical Liouville dynamics. Several aspects of the scheme are discussed, including a practical and general approach to sample the quantum equilibrium density, the properties of the quantum-classical Liouville equation in the context of correlation function computations, simulation schemes for the approximate dynamics and their interpretation and connections to other approximate quantum dynamical methods.
Renner, R.; Cirac, J. I.
2009-03-01
We show that the quantum de Finetti theorem holds for states on infinite-dimensional systems, provided they satisfy certain experimentally verifiable conditions. This result can be applied to prove the security of quantum key distribution based on weak coherent states or other continuous variable states against general attacks.
Dynamical algebra of observables in dissipative quantum systems
Alipour, Sahar; Chruściński, Dariusz; Facchi, Paolo; Marmo, Giuseppe; Pascazio, Saverio; Rezakhani, Ali T.
2017-02-01
Dynamics and features of quantum systems can be drastically different from classical systems. Dissipation is understood as a general mechanism through which quantum systems may lose part or all of their quantum aspects. Here we discuss a method to analyze behaviors of dissipative quantum systems in an algebraic sense. This method employs a time-dependent product between system’s observables which is induced by the underlying dissipative dynamics. We argue that the long-time limit of the algebra of observables defined with this product yields a contractive algebra which reflects the loss of some quantum features of the dissipative system, and it bears relevant information about irreversibility. We illustrate this result through several examples of dissipation in various Markovian and non-Markovian systems.
An Operator-Based Exact Treatment of Open Quantum Systems
Nicolosi, S
2005-01-01
"Quantum mechanics must be regarded as open systems. On one hand, this is due to the fact that, like in classical physics, any realistic system is subjected to a coupling to an uncontrollable environment which influences it in a non-negligible way. The theory of open quantum systems thus plays a major role in many applications of quantum physics since perfect isolation of quantum system is not possible and since a complete microscopic description or control of the environment degrees of freedom is not feasible or only partially so" [1]. Practical considerations therefore force one to seek for a simpler, effectively probabilistic description in terms of an open system. There is a close physical and mathematical connection between the evolution of an open system, the state changes induced by quantum measurements, and the classical notion of a stochastic process. The paper provides a bibliographic review of this interrelations, it shows the mathematical equivalence between markovian master equation and generaliz...
Pillai, Sreenadh Sasidharan; Yukawa, Hiroshi; Onoshima, Daisuke; Biju, Vasudevanpillai; Baba, Yoshinobu
2017-01-01
The steady state and time-resolved photoluminescence quenching of streptavidin modified CdSe/ZnS quantum dots (QDs) instigated by biotin-peptide-BHQ-1 (biotin-pep-BHQ-1) molecule was investigated. Here, we have achieved an efficient photoluminescence (PL) quenching of QDs with the conjugation of dark quencher (black hole quencher-BHQ) molecules intermediated with the GPLGVRGK peptide. The luminescence of streptavidin-QDs585 was decreased upon titration with a nano molar concentration of the biotin-GPLGVRGK-BHQ-1 molecule. It has been suggested that the decrease of QDs PL occurred through a Förster resonance energy transfer (FRET) mechanism from the analysis of steady state photoluminescence intensity measurements as well as time resolved lifetime measurements of streptavidin-QDs and QDs-(pep-BHQ-1)n conjugates. The sequence of intermediate peptide GPLG↓VRGK can act as a target material for matrix metalloproteinases-2 (MMP-2) produced by cancer cells at its Gly and Val region, shown by the down-headed arrow. Interestingly, here the reported self-assembled QDs-(pep-BHQ-1)n conjugates could detect the presence MMP-2 at a detection limit of 1 ng/mL with a clear luminescence recovery.
Quantum Phase Transitions in Conventional Matrix Product Systems
Zhu, Jing-Min; Huang, Fei; Chang, Yan
2017-02-01
For matrix product states(MPSs) of one-dimensional spin-1/2 chains, we investigate a new kind of conventional quantum phase transition(QPT). We find that the system has two different ferromagnetic phases; on the line of the two ferromagnetic phases coexisting equally, the system in the thermodynamic limit is in an isolated mediate-coupling state described by a paramagnetic state and is in the same state as the renormalization group fixed point state, the expectation values of the physical quantities are discontinuous, and any two spin blocks of the system have the same geometry quantum discord(GQD) within the range of open interval (0,0.25) and the same classical correlation(CC) within the range of open interval (0,0.75) compared to any phase having no any kind of correlation. We not only realize the control of QPTs but also realize the control of quantum correlation of quantum many-body systems on the critical line by adjusting the environment parameters, which may have potential application in quantum information fields and is helpful to comprehensively and deeply understand the quantum correlation, and the organization and structure of quantum correlation especially for long-range quantum correlation of quantum many-body systems.
Ultracold atoms for simulation of many body quantum systems
Hutchinson, David A. W.
2017-01-01
Feynman famously proposed simulating quantum physics using other, better controlled, quantum systems. This vision is now a reality within the realm of ultracold atomic physics. We discuss how these systems can be used to simulate many body physics, concentrating the Berezinskii-Kosterlitz-Thouless transition in 2D physics and the role of disorder.
Quantum Discrete Fourier Transform in an Ion Trap System
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2007-01-01
We propose two schemes for the implementation of quantum discrete Fourier transform in the ion trap system. In each scheme we design a tunable two-qubit phase gate as the main ingredient. The experimental implementation of the schemes would be an important step toward complex quantum computation in the ion trap system.
Quantum-classical correspondence in steady states of nonadiabatic systems
Energy Technology Data Exchange (ETDEWEB)
Fujii, Mikiya; Yamashita, Koichi [Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Tokyo 113-8656 (Japan); CREST, JST, Tokyo 113-8656 (Japan)
2015-12-31
We first present nonadiabatic path integral which is exact formulation of quantum dynamics in nonadiabatic systems. Then, by applying the stationary phase approximations to the nonadiabatic path integral, a semiclassical quantization condition, i.e., quantum-classical correspondence, for steady states of nonadiabatic systems is presented as a nonadiabatic trace formula. The present quantum-classical correspondence indicates that a set of primitive hopping periodic orbits, which are invariant under time evolution in the phase space of the slow degree of freedom, should be quantized. The semiclassical quantization is then applied to a simple nonadiabatic model and accurately reproduces exact quantum energy levels.
Experimental quantum simulation of entanglement in many-body systems.
Zhang, Jingfu; Wei, Tzu-Chieh; Laflamme, Raymond
2011-07-01
We employ a nuclear magnetic resonance (NMR) quantum information processor to simulate the ground state of an XXZ spin chain and measure its NMR analog of entanglement, or pseudoentanglement. The observed pseudoentanglement for a small-size system already displays a singularity, a signature which is qualitatively similar to that in the thermodynamical limit across quantum phase transitions, including an infinite-order critical point. The experimental results illustrate a successful approach to investigate quantum correlations in many-body systems using quantum simulators.
Experimental Quantum Simulation of Entanglement in Many-body Systems
Zhang, Jingfu; Laflamme, Raymond
2011-01-01
We employ a nuclear magnetic resonance (NMR) quantum information processor to simulate the ground state of an XXZ spin chain and measure its NMR analog of entanglement, or pseudo-entanglement. The observed pseudo-entanglement for a small system size already displays singularity, a signature which is qualitatively similar to that in thermodynamical limit across quantum phase transitions, including an infinite-order critical point. The experimental results illustrate a successful approach to investigate quantum correlations in many-body systems using quantum simulators.
Automated drawing system of quantum energy levels
Stampoultzis, M.; Sinatkas, J.; Tsakstara, V.; Kosmas, T. S.
2014-03-01
The purpose of this work is to derive an automated system that provides advantageous drawings of energy spectra for quantum systems (nuclei, atoms, molecules, etc.) required in various physical sciences. The automation involves the development of appropriate computational code and graphical imaging system based on raw data insertion, theoretical calculations and experimental or bibliographic data insertion. The system determines the appropriate scale to depict graphically with the best possible way in the available space. The presently developed code operates locally and the results are displayed on the screen and can be exported to a PostScript file. We note its main features to arrange and visualize in the available space the energy levels with their identity, taking care the existence in the final diagram the least auxiliary deviations. Future improvements can be the use of Java and the availability on the Internet. The work involves the automated plotting of energy levels in molecules, atoms, nuclei and other types of quantized energy spectra. The automation involves the development of an appropriate computational code and graphical imaging system.
Quantum integrable systems. Quantitative methods in biology
Feverati, Giovanni
2011-01-01
Quantum integrable systems have very strong mathematical properties that allow an exact description of their energetic spectrum. From the Bethe equations, I formulate the Baxter "T-Q" relation, that is the starting point of two complementary approaches based on nonlinear integral equations. The first one is known as thermodynamic Bethe ansatz, the second one as Kl\\"umper-Batchelor-Pearce-Destri- de Vega. I show the steps toward the derivation of the equations for some of the models concerned. I study the infrared and ultraviolet limits and discuss the numerical approach. Higher rank integrals of motion can be obtained, so gaining some control on the eigenvectors. After, I discuss the Hubbard model in relation to the N = 4 supersymmetric gauge theory. The Hubbard model describes hopping electrons on a lattice. In the second part, I present an evolutionary model based on Turing machines. The goal is to describe aspects of the real biological evolution, or Darwinism, by letting evolve populations of algorithms. ...
Slow scrambling in disordered quantum systems
Swingle, Brian
2016-01-01
Recent work has studied the growth of commutators as a probe of chaos and information scrambling in quantum many-body systems. In this work we study the effect of static disorder on the growth of commutators in a variety of contexts. We find generically that disorder slows the onset of scrambling, and, in the case of a many-body localized state, partially halts it. We access the many-body localized state using a standard fixed point Hamiltonian, and we show that operators exhibit slow logarithmic growth under time evolution. We compare the result with the expected growth of commutators in both localized and delocalized non-interacting disordered models. Finally, based on a scaling argument, we state a conjecture about the effect of weak interactions on the growth of commutators in an interacting diffusive metal.
Thermalization and pseudolocality in extended quantum systems
Doyon, Benjamin
2015-01-01
Recently, it was understood that extended concepts of locality played important roles in the study of extended quantum systems out of equilibrium, in particular in so-called generalized Gibbs ensembles. In this paper, we rigorously study pseudolocal charges and their involvement in time evolutions and in the thermalization process of arbitrary states with strong enough clustering properties. We show that the densities of pseudolocal charges form a Hilbert space, with inner product determined by response functions. Using this, we define the family of pseudolocal states: clustering states connected to the infinite-temperature state by paths whose tangents are actions of pseudolocal charges. This family includes thermal Gibbs states, as well as (a precise definition of) generalized Gibbs ensembles. We prove that the family of pseudolocal states is preserved by finite time evolution, and that, under certain conditions, the stationary state emerging at infinite time is a generalized Gibbs ensemble with respect to ...
Dynamical quantum phase transitions (Review Article)
Zvyagin, A. A.
2016-11-01
During recent years the interest to dynamics of quantum systems has grown considerably. Quantum many body systems out of equilibrium often manifest behavior, different from the one predicted by standard statistical mechanics and thermodynamics in equilibrium. Since the dynamics of a many-body quantum system typically involve many excited eigenstates, with a non-thermal distribution, the time evolution of such a system provides an unique way for investigation of non-equilibrium quantum statistical mechanics. Last decade such new subjects like quantum quenches, thermalization, pre-thermalization, equilibration, generalized Gibbs ensemble, etc. are among the most attractive topics of investigation in modern quantum physics. One of the most interesting themes in the study of dynamics of quantum many-body systems out of equilibrium is connected with the recently proposed important concept of dynamical quantum phase transitions. During the last few years a great progress has been achieved in studying of those singularities in the time dependence of characteristics of quantum mechanical systems, in particular, in understanding how the quantum critical points of equilibrium thermodynamics affect their dynamical properties. Dynamical quantum phase transitions reveal universality, scaling, connection to the topology, and many other interesting features. Here we review the recent achievements of this quickly developing part of low-temperature quantum physics. The study of dynamical quantum phase transitions is especially important in context of their connection to the problem of the modern theory of quantum information, where namely non-equilibrium dynamics of many-body quantum system plays the major role.
Quantum correlations in non-inertial cavity systems
Harsij, Zeynab; Mirza, Behrouz
2016-10-01
Non-inertial cavities are utilized to store and send Quantum Information between mode pairs. A two-cavity system is considered where one is inertial and the other accelerated in a finite time. Maclaurian series are applied to expand the related Bogoliubov coefficients and the problem is treated perturbatively. It is shown that Quantum Discord, which is a measure of quantumness of correlations, is degraded periodically. This is almost in agreement with previous results reached in accelerated systems where increment of acceleration decreases the degree of quantum correlations. As another finding of the study, it is explicitly shown that degradation of Quantum Discord disappears when the state is in a single cavity which is accelerated for a finite time. This feature makes accelerating cavities useful instruments in Quantum Information Theory.
Fate of classical solitons in one-dimensional quantum systems.
Energy Technology Data Exchange (ETDEWEB)
Pustilnik, M.; Matveev, K. A.
2015-11-23
We study one-dimensional quantum systems near the classical limit described by the Korteweg-de Vries (KdV) equation. The excitations near this limit are the well-known solitons and phonons. The classical description breaks down at long wavelengths, where quantum effects become dominant. Focusing on the spectra of the elementary excitations, we describe analytically the entire classical-to-quantum crossover. We show that the ultimate quantum fate of the classical KdV excitations is to become fermionic quasiparticles and quasiholes. We discuss in detail two exactly solvable models exhibiting such crossover, the Lieb-Liniger model of bosons with weak contact repulsion and the quantum Toda model, and argue that the results obtained for these models are universally applicable to all quantum one-dimensional systems with a well-defined classical limit described by the KdV equation.
Strong polygamy of quantum correlations in multi-party quantum systems
San Kim, Jeong
2014-10-01
We propose a new type of polygamy inequality for multi-party quantum entanglement. We first consider the possible amount of bipartite entanglement distributed between a fixed party and any subset of the rest parties in a multi-party quantum system. By using the summation of these distributed entanglements, we provide an upper bound of the distributed entanglement between a party and the rest in multi-party quantum systems. We then show that this upper bound also plays as a lower bound of the usual polygamy inequality, therefore the strong polygamy of multi-party quantum entanglement. For the case of multi-party pure states, we further show that the strong polygamy of entanglement implies the strong polygamy of quantum discord.
Quantum-biological control of energy transfer in hybrid quantum dot-metallic nanoparticle systems
Sadeghi, Seyed M.; Hood, Brady; Patty, Kira
2016-09-01
We show theoretically that when a semiconductor quantum dot and metallic nanoparticle system interacts with a laser field, quantum coherence can introduce a new landscape for the dynamics of Forster resonance energy transfer (FRET). We predict adsorption of biological molecules to such a hybrid system can trigger dramatic changes in the way energy is transferred, blocking FRET while the distance between the quantum dot and metallic nanoparticle (R) and other structural specifications remain unchanged. We study the impact of variation of R on the FRET rate in the presence of quantum coherence and its ultrafast decay, offering a characteristically different dependency than the standard 1/R6. Application of the results for quantum nanosensors is discussed.
A real-time spectrum acquisition system design based on quantum dots-quantum well detector
Zhang, S. H.; Guo, F. M.
2016-01-01
In this paper, we studied the structure characteristics of quantum dots-quantum well photodetector with response wavelength range from 400 nm to 1000 nm. It has the characteristics of high sensitivity, low dark current and the high conductance gain. According to the properties of the quantum dots-quantum well photodetectors, we designed a new type of capacitive transimpedence amplifier (CTIA) readout circuit structure with the advantages of adjustable gain, wide bandwidth and high driving ability. We have implemented the chip packaging between CTIA-CDS structure readout circuit and quantum dots detector and tested the readout response characteristics. According to the timing signals requirements of our readout circuit, we designed a real-time spectral data acquisition system based on FPGA and ARM. Parallel processing mode of programmable devices makes the system has high sensitivity and high transmission rate. In addition, we realized blind pixel compensation and smoothing filter algorithm processing to the real time spectrum data by using C++. Through the fluorescence spectrum measurement of carbon quantum dots and the signal acquisition system and computer software system to realize the collection of the spectrum signal processing and analysis, we verified the excellent characteristics of detector. It meets the design requirements of quantum dot spectrum acquisition system with the characteristics of short integration time, real-time and portability.
Quantum Cost Efficient Reversible BCD Adder for Nanotechnology Based Systems
Islam, Md Saiful; Begum, Zerina
2011-01-01
Reversible logic allows low power dissipating circuit design and founds its application in cryptography, digital signal processing, quantum and optical information processing. This paper presents a novel quantum cost efficient reversible BCD adder for nanotechnology based systems using PFAG gate. It has been demonstrated that the proposed design offers less hardware complexity and requires minimum number of garbage outputs than the existing counterparts. The remarkable property of the proposed designs is that its quantum realization is given in NMR technology.
Approach to Equilibrium for Quantum Systems with Continuous Spectrum
Laura, Roberto
Considering quantum states as functionals acting on observables to give their mean values, it is possible to deal with quantum systems with continuous spectrum, generalizing the concept of trace. Generalized observables and states are defined for a quantum oscillator linearly coupled to a scalar field, and the analytic expression for time evolution is obtained. The "final" state (t → ∞) is presented as a weak limit. Finite and infinite number of exited modes of the field are considered.
Quantum Chaos in Physical Systems: from Super Conductors to Quarks
Bittner, Elmar; Markum, Harald; Pullirsch, Rainer
2001-01-01
This article is the written version of a talk delivered at the Bexbach Colloquium of Science 2000 and starts with an introduction into quantum chaos and its relationship to classical chaos. The Bohigas-Giannoni-Schmit conjecture is formulated and evaluated within random-matrix theory. Several examples of physical systems exhibiting quantum chaos ranging from nuclear to solid state physics are presented. The presentation concludes with recent research work on quantum chromodynamics and the qua...
Advanced-Retarded Differential Equations in Quantum Photonic Systems
Alvarez-Rodriguez, Unai; Perez-Leija, Armando; Egusquiza, Iñigo L.; Gräfe, Markus; Sanz, Mikel; Lamata, Lucas; Szameit, Alexander; Solano, Enrique
2017-01-01
We propose the realization of photonic circuits whose dynamics is governed by advanced-retarded differential equations. Beyond their mathematical interest, these photonic configurations enable the implementation of quantum feedback and feedforward without requiring any intermediate measurement. We show how this protocol can be applied to implement interesting delay effects in the quantum regime, as well as in the classical limit. Our results elucidate the potential of the protocol as a promising route towards integrated quantum control systems on a chip. PMID:28230090
Detective quantum efficiency of the LODOX system
de Villiers, Mattieu; de Jager, Gerhard
2003-06-01
The Detective Quantum Efficiency (DQE) of a digital x-ray imaging system describes how much of the signal to noise ratio of the incident radiation is sustained in the resultant digital image. This measure of dose efficiency is suitable for the comparison of detectors produced by different manufacturers. The International Electrotechnical Commission (IEC) stipulates standard methods and conditions for the measurement of the DQE for single exposure imaging systems such as flat panel detectors. This paper shows how the calculation is adapted for DQE measurements of scanning systems. In this paper it is described how to measure the presampled Modulation Transfer Function (MTF) using an edge test method and how to extract the horizontal and vertical components of the Noise Power Spectrum (NPS) in a way that is insensitive to structured noise patterns often found in scanned images. The calculation of the total number of incident photons from the radiation dose measurement is explained and results are provided for the Lodox low dose full body digital x-ray scanning system which is developed in South Africa.
Gain and loss in open quantum systems
Eleuch, Hichem; Rotter, Ingrid
2017-06-01
Photosynthesis is the basic process used by plants to convert light energy in reaction centers into chemical energy. The high efficiency of this process is not yet understood today. Using the formalism for the description of open quantum systems by means of a non-Hermitian Hamilton operator, we consider initially the interplay of gain (acceptor) and loss (donor). Near singular points it causes fluctuations of the cross section which appear without any excitation of internal degrees of freedom of the system. This process occurs therefore very quickly and with high efficiency. We then consider the excitation of resonance states of the system by means of these fluctuations. This second step of the whole process takes place much slower than the first one, because it involves the excitation of internal degrees of freedom of the system. The two-step process as a whole is highly efficient, and the decay is biexponential. We provide, if possible, the results of analytical studies, otherwise characteristic numerical results. The similarities of the obtained results to light harvesting in photosynthetic organisms are discussed.
Effects of symmetry breaking in finite quantum systems
Energy Technology Data Exchange (ETDEWEB)
Birman, J.L. [Department of Physics, City College, City University of New York, New York, NY 10031 (United States); Nazmitdinov, R.G. [Departament de Fisica, Universitat de les Illes Balears, Palma de Mallorca 07122 (Spain); Bogolubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Yukalov, V.I., E-mail: yukalov@theor.jinr.ru [Bogolubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation)
2013-05-15
The review considers the peculiarities of symmetry breaking and symmetry transformations and the related physical effects in finite quantum systems. Some types of symmetry in finite systems can be broken only asymptotically. However, with a sufficiently large number of particles, crossover transitions become sharp, so that symmetry breaking happens similarly to that in macroscopic systems. This concerns, in particular, global gauge symmetry breaking, related to Bose–Einstein condensation and superconductivity, or isotropy breaking, related to the generation of quantum vortices, and the stratification in multicomponent mixtures. A special type of symmetry transformation, characteristic only for finite systems, is the change of shape symmetry. These phenomena are illustrated by the examples of several typical mesoscopic systems, such as trapped atoms, quantum dots, atomic nuclei, and metallic grains. The specific features of the review are: (i) the emphasis on the peculiarities of the symmetry breaking in finite mesoscopic systems; (ii) the analysis of common properties of physically different finite quantum systems; (iii) the manifestations of symmetry breaking in the spectra of collective excitations in finite quantum systems. The analysis of these features allows for the better understanding of the intimate relation between the type of symmetry and other physical properties of quantum systems. This also makes it possible to predict new effects by employing the analogies between finite quantum systems of different physical nature.
Entangled Systems New Directions in Quantum Physics
Audretsch, Jürgen
2007-01-01
An introductory textbook for advanced students of physics, chemistry and computer science, covering an area of physics that has lately witnessed rapid expansion. The topics treated here include quantum information, quantum communication, quantum computing, teleportation and hidden parameters, thus imparting not only a well-founded understanding of quantum theory as such, but also a solid basis of knowledge from which readers can follow the rapid development of the topic or delve deeper into a more specialized branch of research. Commented recommendations for further reading as well as end-of-chapter problems help the reader to quickly access the theoretical basics of future key technologies
Classical and quantum simulations of many-body systems
Energy Technology Data Exchange (ETDEWEB)
Murg, Valentin
2008-04-07
This thesis is devoted to recent developments in the fields of classical and quantum simulations of many-body systems. We describe new classical algorithms that overcome problems apparent in conventional renormalization group and Monte Carlo methods. These algorithms make possible the detailed study of finite temperature properties of 2-D classical and 1-D quantum systems, the investigation of ground states of 2-D frustrated or fermionic systems and the analysis of time evolutions of 2-D quantum systems. Furthermore, we propose new 'analog' quantum simulators that are able to realize interesting models such as a Tonks-Girardeau gas or a frustrated spin-1/2 XY model on a trigonal lattice. These quantum simulators make use of optical lattices and trapped ions and are technically feasible. In fact, the Tonks-Girardeau gas has been realized experimentally and we provide a detailed comparison between the experimental data and the theoretical predictions. (orig.)
Bioanalytical Applications of Fluorenscence Quenching.
1986-02-10
interaction of different cyclodextrin systems with the polynuclear aromatic compound, pyrene.(7 ) There are other cases where the Stern-Volmer plot deviates... encapsulated in lecithin liposomes. In this manner the fluorescence is self-quenched. When the liposomes are disrupted, the dye is released and
Wavefunction controllability for finite-dimensional bilinear quantum systems
Energy Technology Data Exchange (ETDEWEB)
Turinici, Gabriel [INRIA Rocquencourt, Domaine de Voluceau, Rocquencourt, BP 105, 78153 Le Chesnay Cedex (France); Rabitz, Herschel [Department of Chemistry, Princeton University, Princeton, NJ 08544-1009 (United States)
2003-03-14
We present controllability results for quantum systems interacting with lasers. Exact controllability for the wavefunction in these bilinear systems is proved in the finite-dimensional case under very natural hypotheses.
The Rabi Oscillation in Subdynamic System for Quantum Computing
Directory of Open Access Journals (Sweden)
Bi Qiao
2015-01-01
Full Text Available A quantum computation for the Rabi oscillation based on quantum dots in the subdynamic system is presented. The working states of the original Rabi oscillation are transformed to the eigenvectors of subdynamic system. Then the dissipation and decoherence of the system are only shown in the change of the eigenvalues as phase errors since the eigenvectors are fixed. This allows both dissipation and decoherence controlling to be easier by only correcting relevant phase errors. This method can be extended to general quantum computation systems.
Dynamics of genuine multipartite correlations in open quantum systems
Grimsmo, Arne L; Skagerstam, Bo-Sture K
2012-01-01
We propose a measure for genuine multipartite correlations suited for the study of dynamics in open quantum systems. This measure is contextual in the sense that it depends on how information is read from the environment. It is used to study an interacting collective system of atoms undergoing phase transitions as external parameters are varied. We show that the steady state of the system can have a significant degree of genuine multipartite quantum and classical correlations, and that the proposed measure can serve as a witness of critical behavior in quantum systems.
Using a quantum dot system to realize perfect state transfer
Institute of Scientific and Technical Information of China (English)
Li Ji; Wu Shi-Hai; Zhang Wen-Wen; Xi Xiao-Qiang
2011-01-01
There are some disadvantages to Nikolopoulos et al.'s protocol [Nikolopoulos G M,Petrosyan D and Lambropoulos P 2004 Europhys.Lett.65 297] where a quantum dot system is used to realize quantum communication.To overcome these disadvantages,we propose a protocol that uses a quantum dot array to construct a four-qubit spin chain to realize perfect quantum state transfer (PQST).First,we calculate the interaction relation for PQST in the spin chain.Second,we review the interaction between the quantum dots in the Heitler-London approach.Third,we present a detailed program for designing the proper parameters of a quantum dot array to realize PQST.
Quantum Arnol'd Diffusion in a Simple Nonlinear System
Demikhovskii, V Y; Malyshev, A I
2002-01-01
We study the fingerprint of the Arnol'd diffusion in a quantum system of two coupled nonlinear oscillators with a two-frequency external force. In the classical description, this peculiar diffusion is due to the onset of a weak chaos in a narrow stochastic layer near the separatrix of the coupling resonance. We have found that global dependence of the quantum diffusion coefficient on model parameters mimics, to some extent, the classical data. However, the quantum diffusion happens to be slower that the classical one. Another result is the dynamical localization that leads to a saturation of the diffusion after some characteristic time. We show that this effect has the same nature as for the studied earlier dynamical localization in the presence of global chaos. The quantum Arnol'd diffusion represents a new type of quantum dynamics and can be observed, for example, in 2D semiconductor structures (quantum billiards) perturbed by time-periodic external fields.
Computational physics simulation of classical and quantum systems
Scherer, Philipp O J
2017-01-01
This textbook presents basic numerical methods and applies them to a large variety of physical models in multiple computer experiments. Classical algorithms and more recent methods are explained. Partial differential equations are treated generally comparing important methods, and equations of motion are solved by a large number of simple as well as more sophisticated methods. Several modern algorithms for quantum wavepacket motion are compared. The first part of the book discusses the basic numerical methods, while the second part simulates classical and quantum systems. Simple but non-trivial examples from a broad range of physical topics offer readers insights into the numerical treatment but also the simulated problems. Rotational motion is studied in detail, as are simple quantum systems. A two-level system in an external field demonstrates elementary principles from quantum optics and simulation of a quantum bit. Principles of molecular dynamics are shown. Modern bounda ry element methods are presented ...
Bayesian parameter inference from continuously monitored quantum systems
DEFF Research Database (Denmark)
Gammelmark, Søren; Mølmer, Klaus
2013-01-01
We review the introduction of likelihood functions and Fisher information in classical estimation theory, and we show how they can be defined in a very similar manner within quantum measurement theory. We show that the stochastic master equations describing the dynamics of a quantum system subject...
Security Proof for Quantum Key Distribution Using Qudit Systems
Sheridan, Lana
2010-01-01
We provide security bounds against coherent attacks for two families of quantum key distribution protocols that use $d$-dimensional quantum systems. In the asymptotic regime, both the secret key rate for fixed noise and the robustness to noise increase with $d$. The finite-key corrections are found to be almost insensitive to $d\\lesssim 20$.
Speed limits for quantum gates in multiqubit systems
Ashhab, S.; De Groot, P.C.; Nori, F.
2012-01-01
We use analytical and numerical calculations to obtain speed limits for various unitary quantum operations in multiqubit systems under typical experimental conditions. The operations that we consider include single-, two-, and three-qubit gates, as well as quantum-state transfer in a chain of qubits
Quantum-Classical Connection for Hydrogen Atom-Like Systems
Syam, Debapriyo; Roy, Arup
2011-01-01
The Bohr-Sommerfeld quantum theory specifies the rules of quantization for circular and elliptical orbits for a one-electron hydrogen atom-like system. This article illustrates how a formula connecting the principal quantum number "n" and the length of the major axis of an elliptical orbit may be arrived at starting from the quantum…
Phase-modulation transmission system for quantum cryptography.
Mérolla, J M; Mazurenko, Y; Goedgebuer, J P; Porte, H; Rhodes, W T
1999-01-15
We describe a new method for quantum key distribution that utilizes phase modulation of sidebands of modulation by use of integrated electro-optic modulators at the transmitting and receiving modules. The system is shown to produce constructive or destructive interference with unity visibility, which should allow quantum cryptography to be carried out with high flexibility by use of conventional devices.
Analysis of superconducting cavity quench events at SSRF
Institute of Scientific and Technical Information of China (English)
HOU Hong-Tao; LI Zheng; LIU Jian-Fei; ZHAO Yu-Bin; ZHAO Shen-jie; ZHANG Zhi-Gang; LUO Chen; FENG Zi-Qiang; MAO Dong-Qing; ZHENG Xiang
2011-01-01
Quench is important and dangerous to superconducting RF cavities. This paper illustrates the mechanism of quench and how a quench detector works, and analyzes the quench events happening during beam operations and cavity conditioning. We find that the quench protection is mostly triggered by some reasons such as fluctuation of cavity voltage, multipacting or arc, rather than a real cavity thermal breakdown. The results will be beneficial to optimize the operation parameters of superconducting cavities, to discover the real reasons for beam trip by quench interlock, and to improve the operation stability of superconducting RF systems.
Spectroscopic studies in open quantum systems
Rotter, I; Pichugin, K N; Seba, P
2000-01-01
The spectroscopic properties of an open quantum system are determined by theeigenvalues and eigenfunctions of an effective Hamiltonian H consisting of theHamiltonian H_0 of the corresponding closed system and a non-Hermitiancorrection term W arising from the interaction via the continuum of decaychannels. The eigenvalues E_R of H are complex. They are the poles of theS-matrix and provide both the energies and widths of the states. We illustratethe interplay between Re(H) and Im(H) by means of the different interferencephenomena between two neighboured resonance states. Level repulsion along thereal axis appears if the interaction is caused mainly by Re(H) while abifurcation of the widths appears if the interaction occurs mainly due toIm(H). We then calculate the poles of the S-matrix and the correspondingwavefunctions for a rectangular microwave resonator with a scatter as afunction of the area of the resonator as well as of the degree of opening to aguide. The calculations are performed by using the method o...
Precise semiconductor nanotubes and nanocorrugated quantum systems
Prinz, V. Ya.
2004-08-01
A concept in precise nanostructuring permitting the formation of solid-state nanoshells of various shapes from monocrystalline InGaAs/GaAs or Si/GeSi strained heterofilms, or from metal-semiconductor, metal-metal and hybrid films is outlined. Ultra-thin strained films released from the massive substrate tend to acquire a new equilibrium shape for which their elastic energy is minimal. Bending off from the substrate or rolling into cylindrical objects, the films form nanotubes, rings, helices, open and closed 3D nanoshells and their ordered arrays. The present work focuses on the set of newly proposed methods and realized processes constituting a fabrication technology for these free-standing precise nanoobjects and systems. New results on the formation of spatially periodic structures, nanocorrugated systems, shells with the minimum radius of curvature of ∼1 nm, and assembling these shells in even more complex architectures, for example, quantum-dots molecules, are described. The fabricated nanoshells offer much promise as building blocks for nanoelectronic and nanomechanic devices, their fabrication technology being quite compatible with the well-established integrated-circuit technology.
Implementing quantum electrodynamics with ultracold atomic systems
Kasper, V.; Hebenstreit, F.; Jendrzejewski, F.; Oberthaler, M. K.; Berges, J.
2017-02-01
We discuss the experimental engineering of model systems for the description of quantum electrodynamics (QED) in one spatial dimension via a mixture of bosonic 23Na and fermionic 6Li atoms. The local gauge symmetry is realized in an optical superlattice, using heteronuclear boson–fermion spin-changing interactions which preserve the total spin in every local collision. We consider a large number of bosons residing in the coherent state of a Bose–Einstein condensate on each link between the fermion lattice sites, such that the behavior of lattice QED in the continuum limit can be recovered. The discussion about the range of possible experimental parameters builds, in particular, upon experiences with related setups of fermions interacting with coherent samples of bosonic atoms. We determine the atomic system’s parameters required for the description of fundamental QED processes, such as Schwinger pair production and string breaking. This is achieved by benchmark calculations of the atomic system and of QED itself using functional integral techniques. Our results demonstrate that the dynamics of one-dimensional QED may be realized with ultracold atoms using state-of-the-art experimental resources. The experimental setup proposed may provide a unique access to longstanding open questions for which classical computational methods are no longer applicable.
Spectroscopic studies in open quantum systems
Rotter; Persson; Pichugin; Seba
2000-07-01
The Hamiltonian H of an open quantum system is non-Hermitian. Its complex eigenvalues E(R) are the poles of the S matrix and provide both the energies and widths of the states. We illustrate the interplay between Re(H) and Im(H) by means of the different interference phenomena between two neighboring resonance states. Level repulsion may occur along the real or imaginary axis (the latter is called resonance trapping). In any case, the eigenvalues of the two states avoid crossing in the complex plane. We then calculate the poles of the S matrix and the corresponding wave functions for a rectangular microwave resonator with a scatter as a function of the area of the resonator as well as of the degree of opening to a waveguide. The calculations are performed by using the method of exterior complex scaling. Re(H) and Im(H) cause changes in the structure of the wave functions which are permanent, as a rule. The resonance picture obtained from the microwave resonator shows all the characteristic features known from the study of many-body systems in spite of the absence of two-body forces. The effects arising from the interplay between resonance trapping and level repulsion along the real axis are not involved in the statistical theory (random matrix theory).
Energy transfer processes in semiconductor quantum dots: bacteriorhodopsin hybrid system
Rakovich, Aliaksandra; Sukhanova, Alyona; Bouchonville, Nicolas; Molinari, Michael; Troyon, Michel; Cohen, Jacques H. M.; Rakovich, Yury; Donegan, John F.; Nabiev, Igor
2009-05-01
The potential impact of nanoscience on energy transfer processes in biomolecules was investigated on the example of a complex between fluorescent semiconductor nanocrystals and photochromic membrane protein. The interactions between colloidal CdTe quantum dots (QDs) and bacteriorhodopsin (bR) protein were studied by a variety of spectroscopic techniques, including integrated and time-resolved fluorescence spectroscopies, zeta potential and size measurement, and fluorescence correlation spectroscopy. QDs' luminescence was found to be strongly modulated by bacteriorhodopsin, but in a controllable way. Decreasing emission lifetimes and blue shifts in QDs' emission at increasing protein concentrations suggest that quenching occurs via Förster resonance energy transfer. On the other hand, concave Stern-Volmer plots and sigmoidal photoluminescence quenching curves imply that the self-assembling of NCs and bR exists, and the number of nanocrystals (NCs) per bacteriorhodopsin contributing to energy transfer can be determined from the inflection points of sigmoidal curves. This number was found to be highly dependent not only on the spectral overlap between NC emission and bR absorption bands, but also on nanocrystal surface charge. These results demonstrate the potential of how inorganic nanoscale materials can be employed to improve the generic molecular functions of biomolecules. The observed interactions between CdTe nanocrystals and bacteriorhodopsin can provide the basis for the development of novel functional materials with unique photonic properties and applications in areas such as all-optical switching, photovoltaics and data storage.
Quantum spin systems on infinite lattices a concise introduction
Naaijkens, Pieter
2017-01-01
This course-based primer offers readers a concise introduction to the description of quantum mechanical systems with infinitely many degrees of freedom – and quantum spin systems in particular – using the operator algebraic approach. Here, the observables are modeled using elements of some operator algebra, usually a C*-algebra. This text introduces readers to the framework and the necessary mathematical tools without assuming much mathematical background, making it more accessible than advanced monographs. The book also highlights the usefulness of the so-called thermodynamic limit of quantum spin systems, which is the limit of infinite system size. For example, this makes it possible to clearly distinguish between local and global properties, without having to keep track of the system size. Together with Lieb-Robinson bounds, which play a similar role in quantum spin systems to that of the speed of light in relativistic theories, this approach allows ideas from relativistic field theories to be implemen...
Test of quantum thermalization in the two-dimensional transverse-field Ising model
Blaß, Benjamin; Rieger, Heiko
2016-12-01
We study the quantum relaxation of the two-dimensional transverse-field Ising model after global quenches with a real-time variational Monte Carlo method and address the question whether this non-integrable, two-dimensional system thermalizes or not. We consider both interaction quenches in the paramagnetic phase and field quenches in the ferromagnetic phase and compare the time-averaged probability distributions of non-conserved quantities like magnetization and correlation functions to the thermal distributions according to the canonical Gibbs ensemble obtained with quantum Monte Carlo simulations at temperatures defined by the excess energy in the system. We find that the occurrence of thermalization crucially depends on the quench parameters: While after the interaction quenches in the paramagnetic phase thermalization can be observed, our results for the field quenches in the ferromagnetic phase show clear deviations from the thermal system. These deviations increase with the quench strength and become especially clear comparing the shape of the thermal and the time-averaged distributions, the latter ones indicating that the system does not completely lose the memory of its initial state even for strong quenches. We discuss our results with respect to a recently formulated theorem on generalized thermalization in quantum systems.
Model-Checking Linear-Time Properties of Quantum Systems
Ying, Mingsheng; Yu, Nengkun; Feng, Yuan
2011-01-01
We define a formal framework for reasoning about linear-time properties of quantum systems in which quantum automata are employed in the modeling of systems and certain closed subspaces of state (Hilbert) spaces are used as the atomic propositions about the behavior of systems. We provide an algorithm for verifying invariants of quantum automata. Then automata-based model-checking technique is generalized for the verification of safety properties recognizable by reversible automata and omega-properties recognizable by reversible Buechi automata.
Evaluation of the Quantum II yeast identification system.
Kiehn, T E; Edwards, F F; Tom, D; LIEBERMAN, G; Bernard, E M; Armstrong, D.
1985-01-01
We compared three methods for identifying clinical yeast isolates: Abbott Quantum II, API 20C, and a modified BBL Minitek system. The API 20C and modified Minitek systems agreed on the identification of 243 of 245 yeasts (99.2%). The Quantum II system correctly identified 197 (80.4%), incorrectly identified 19 (7.8%), and did not identify 29 (11.8%) of the yeasts. Most of the misidentifications with the Quantum II occurred because assimilation or biochemical results were false-positive. Sixte...