Quantum harmonic oscillator in a thermal bath

NASA Technical Reports Server (NTRS)

Zhang, Yuhong

1993-01-01

The influence functional path-integral treatment of quantum Brownian motion is briefly reviewed. A newly derived exact master equation of a quantum harmonic oscillator coupled to a general environment at arbitrary temperature is discussed. It is applied to the problem of loss of quantum coherence.

Production of a sterile species: Quantum kinetics

NASA Astrophysics Data System (ADS)

Boyanovsky, D.; Ho, C. M.

2007-10-01

Production of a sterile species is studied within an effective model of active-sterile neutrino mixing in a medium in thermal equilibrium. The quantum kinetic equations for the distribution functions and coherences are obtained from two independent methods: the effective action and the quantum master equation. The decoherence time scale for active-sterile oscillations is τdec=2/Γaa, but the evolution of the distribution functions is determined by the two different time scales associated with the damping rates of the quasiparticle modes in the medium: Γ1=Γaacos⁡2θm; Γ2=Γaasin⁡2θm where Γaa is the interaction rate of the active species in the absence of mixing and θm the mixing angle in the medium. These two time scales are widely different away from Mikheyev-Smirnov-Wolfenstein resonances and preclude the kinetic description of active-sterile production in terms of a simple rate equation. We give the complete set of quantum kinetic equations for the active and sterile populations and coherences and discuss in detail the various approximations. A generalization of the active-sterile transition probability in a medium is provided via the quantum master equation. We derive explicitly the usual quantum kinetic equations in terms of the “polarization vector” and show their equivalence to those obtained from the quantum master equation and effective action.

Sharp peaks in the conductance of a double quantum dot and a quantum-dot spin valve at high temperatures: A hierarchical quantum master equation approach

NASA Astrophysics Data System (ADS)

Wenderoth, S.; Bätge, J.; Härtle, R.

2016-09-01

We study sharp peaks in the conductance-voltage characteristics of a double quantum dot and a quantum dot spin valve that are located around zero bias. The peaks share similarities with a Kondo peak but can be clearly distinguished, in particular as they occur at high temperatures. The underlying physical mechanism is a strong current suppression that is quenched in bias-voltage dependent ways by exchange interactions. Our theoretical results are based on the quantum master equation methodology, including the Born-Markov approximation and a numerically exact, hierarchical scheme, which we extend here to the spin-valve case. The comparison of exact and approximate results allows us to reveal the underlying physical mechanisms, the role of first-, second- and beyond-second-order processes and the robustness of the effect.

Operator Approach to the Master Equation for the One-Step Process

NASA Astrophysics Data System (ADS)

Hnatič, M.; Eferina, E. G.; Korolkova, A. V.; Kulyabov, D. S.; Sevastyanov, L. A.

2016-02-01

Background. Presentation of the probability as an intrinsic property of the nature leads researchers to switch from deterministic to stochastic description of the phenomena. The kinetics of the interaction has recently attracted attention because it often occurs in the physical, chemical, technical, biological, environmental, economic, and sociological systems. However, there are no general methods for the direct study of this equation. The expansion of the equation in a formal Taylor series (the so called Kramers-Moyal's expansion) is used in the procedure of stochastization of one-step processes. Purpose. However, this does not eliminate the need for the study of the master equation. Method. It is proposed to use quantum field perturbation theory for the statistical systems (the so-called Doi method). Results: This work is a methodological material that describes the principles of master equation solution based on quantum field perturbation theory methods. The characteristic property of the work is that it is intelligible for non-specialists in quantum field theory. Conclusions: We show the full equivalence of the operator and combinatorial methods of obtaining and study of the one-step process master equation.

Decoherence in adiabatic quantum computation

NASA Astrophysics Data System (ADS)

Albash, Tameem; Lidar, Daniel A.

2015-06-01

Recent experiments with increasingly larger numbers of qubits have sparked renewed interest in adiabatic quantum computation, and in particular quantum annealing. A central question that is repeatedly asked is whether quantum features of the evolution can survive over the long time scales used for quantum annealing relative to standard measures of the decoherence time. We reconsider the role of decoherence in adiabatic quantum computation and quantum annealing using the adiabatic quantum master-equation formalism. We restrict ourselves to the weak-coupling and singular-coupling limits, which correspond to decoherence in the energy eigenbasis and in the computational basis, respectively. We demonstrate that decoherence in the instantaneous energy eigenbasis does not necessarily detrimentally affect adiabatic quantum computation, and in particular that a short single-qubit T2 time need not imply adverse consequences for the success of the quantum adiabatic algorithm. We further demonstrate that boundary cancellation methods, designed to improve the fidelity of adiabatic quantum computing in the closed-system setting, remain beneficial in the open-system setting. To address the high computational cost of master-equation simulations, we also demonstrate that a quantum Monte Carlo algorithm that explicitly accounts for a thermal bosonic bath can be used to interpolate between classical and quantum annealing. Our study highlights and clarifies the significantly different role played by decoherence in the adiabatic and circuit models of quantum computing.

Fourier's law of heat conduction: quantum mechanical master equation analysis.

PubMed

Wu, Lian-Ao; Segal, Dvira

2008-06-01

We derive the macroscopic Fourier's Law of heat conduction from the exact gain-loss time convolutionless quantum master equation under three assumptions for the interaction kernel. To second order in the interaction, we show that the first two assumptions are natural results of the long time limit. The third assumption can be satisfied by a family of interactions consisting of an exchange effect. The pure exchange model directly leads to energy diffusion in a weakly coupled spin- 12 chain.

Telegraph noise in Markovian master equation for electron transport through molecular junctions

NASA Astrophysics Data System (ADS)

Kosov, Daniel S.

2018-05-01

We present a theoretical approach to solve the Markovian master equation for quantum transport with stochastic telegraph noise. Considering probabilities as functionals of a random telegraph process, we use Novikov's functional method to convert the stochastic master equation to a set of deterministic differential equations. The equations are then solved in the Laplace space, and the expression for the probability vector averaged over the ensemble of realisations of the stochastic process is obtained. We apply the theory to study the manifestations of telegraph noise in the transport properties of molecular junctions. We consider the quantum electron transport in a resonant-level molecule as well as polaronic regime transport in a molecular junction with electron-vibration interaction.

High-power arrays of quantum cascade laser master-oscillator power-amplifiers.

PubMed

Rauter, Patrick; Menzel, Stefan; Goyal, Anish K; Wang, Christine A; Sanchez, Antonio; Turner, George; Capasso, Federico

2013-02-25

We report on multi-wavelength arrays of master-oscillator power-amplifier quantum cascade lasers operating at wavelengths between 9.2 and 9.8 μm. All elements of the high-performance array feature longitudinal (spectral) as well as transverse single-mode emission at peak powers between 2.7 and 10 W at room temperature. The performance of two arrays that are based on different seed-section designs is thoroughly studied and compared. High output power and excellent beam quality render the arrays highly suitable for stand-off spectroscopy applications.

Supersymmetric quantum spin chains and classical integrable systems

NASA Astrophysics Data System (ADS)

Tsuboi, Zengo; Zabrodin, Anton; Zotov, Andrei

2015-05-01

For integrable inhomogeneous supersymmetric spin chains (generalized graded magnets) constructed employing Y( gl( N| M))-invariant R-matrices in finite-dimensional representations we introduce the master T-operator which is a sort of generating function for the family of commuting quantum transfer matrices. Any eigenvalue of the master T-operator is the tau-function of the classical mKP hierarchy. It is a polynomial in the spectral parameter which is identified with the 0-th time of the hierarchy. This implies a remarkable relation between the quantum supersymmetric spin chains and classical many-body integrable systems of particles of the Ruijsenaars-Schneider type. As an outcome, we obtain a system of algebraic equations for the spectrum of the spin chain Hamiltonians.

Memory Effects and Nonequilibrium Correlations in the Dynamics of Open Quantum Systems

NASA Astrophysics Data System (ADS)

Morozov, V. G.

2018-01-01

We propose a systematic approach to the dynamics of open quantum systems in the framework of Zubarev's nonequilibrium statistical operator method. The approach is based on the relation between ensemble means of the Hubbard operators and the matrix elements of the reduced statistical operator of an open quantum system. This key relation allows deriving master equations for open systems following a scheme conceptually identical to the scheme used to derive kinetic equations for distribution functions. The advantage of the proposed formalism is that some relevant dynamical correlations between an open system and its environment can be taken into account. To illustrate the method, we derive a non-Markovian master equation containing the contribution of nonequilibrium correlations associated with energy conservation.

Selected Aspects of Markovian and Non-Markovian Quantum Master Equations

NASA Astrophysics Data System (ADS)

Lendi, K.

A few particular marked properties of quantum dynamical equations accounting for general relaxation and dissipation are selected and summarized in brief. Most results derive from the universal concept of complete positivity. The considerations mainly regard genuinely irreversible processes as characterized by a unique asymptotically stationary final state for arbitrary initial conditions. From ordinary Markovian master equations and associated quantum dynamical semigroup time-evolution, derivations of higher order Onsager coefficients and related entropy production are discussed. For general processes including non-faithful states a regularized version of quantum relative entropy is introduced. Further considerations extend to time-dependent infinitesimal generators of time-evolution and to a possible description of propagation of initial states entangled between open system and environment. In the coherence-vector representation of the full non-Markovian equations including entangled initial states, first results are outlined towards identifying mathematical properties of a restricted class of trial integral-kernel functions suited to phenomenological applications.

Computation of the asymptotic states of modulated open quantum systems with a numerically exact realization of the quantum trajectory method

NASA Astrophysics Data System (ADS)

Volokitin, V.; Liniov, A.; Meyerov, I.; Hartmann, M.; Ivanchenko, M.; Hänggi, P.; Denisov, S.

2017-11-01

Quantum systems out of equilibrium are presently a subject of active research, both in theoretical and experimental domains. In this work, we consider time-periodically modulated quantum systems that are in contact with a stationary environment. Within the framework of a quantum master equation, the asymptotic states of such systems are described by time-periodic density operators. Resolution of these operators constitutes a nontrivial computational task. Approaches based on spectral and iterative methods are restricted to systems with the dimension of the hosting Hilbert space dim H =N ≲300 , while the direct long-time numerical integration of the master equation becomes increasingly problematic for N ≳400 , especially when the coupling to the environment is weak. To go beyond this limit, we use the quantum trajectory method, which unravels the master equation for the density operator into a set of stochastic processes for wave functions. The asymptotic density matrix is calculated by performing a statistical sampling over the ensemble of quantum trajectories, preceded by a long transient propagation. We follow the ideology of event-driven programming and construct a new algorithmic realization of the method. The algorithm is computationally efficient, allowing for long "leaps" forward in time. It is also numerically exact, in the sense that, being given the list of uniformly distributed (on the unit interval) random numbers, {η1,η2,...,ηn} , one could propagate a quantum trajectory (with ηi's as norm thresholds) in a numerically exact way. By using a scalable N -particle quantum model, we demonstrate that the algorithm allows us to resolve the asymptotic density operator of the model system with N =2000 states on a regular-size computer cluster, thus reaching the scale on which numerical studies of modulated Hamiltonian systems are currently performed.

Computation of the asymptotic states of modulated open quantum systems with a numerically exact realization of the quantum trajectory method.

PubMed

Volokitin, V; Liniov, A; Meyerov, I; Hartmann, M; Ivanchenko, M; Hänggi, P; Denisov, S

2017-11-01

Quantum systems out of equilibrium are presently a subject of active research, both in theoretical and experimental domains. In this work, we consider time-periodically modulated quantum systems that are in contact with a stationary environment. Within the framework of a quantum master equation, the asymptotic states of such systems are described by time-periodic density operators. Resolution of these operators constitutes a nontrivial computational task. Approaches based on spectral and iterative methods are restricted to systems with the dimension of the hosting Hilbert space dimH=N≲300, while the direct long-time numerical integration of the master equation becomes increasingly problematic for N≳400, especially when the coupling to the environment is weak. To go beyond this limit, we use the quantum trajectory method, which unravels the master equation for the density operator into a set of stochastic processes for wave functions. The asymptotic density matrix is calculated by performing a statistical sampling over the ensemble of quantum trajectories, preceded by a long transient propagation. We follow the ideology of event-driven programming and construct a new algorithmic realization of the method. The algorithm is computationally efficient, allowing for long "leaps" forward in time. It is also numerically exact, in the sense that, being given the list of uniformly distributed (on the unit interval) random numbers, {η_{1},η_{2},...,η_{n}}, one could propagate a quantum trajectory (with η_{i}'s as norm thresholds) in a numerically exact way. By using a scalable N-particle quantum model, we demonstrate that the algorithm allows us to resolve the asymptotic density operator of the model system with N=2000 states on a regular-size computer cluster, thus reaching the scale on which numerical studies of modulated Hamiltonian systems are currently performed.

Linear and nonlinear spectroscopy from quantum master equations.

PubMed

Fetherolf, Jonathan H; Berkelbach, Timothy C

2017-12-28

We investigate the accuracy of the second-order time-convolutionless (TCL2) quantum master equation for the calculation of linear and nonlinear spectroscopies of multichromophore systems. We show that even for systems with non-adiabatic coupling, the TCL2 master equation predicts linear absorption spectra that are accurate over an extremely broad range of parameters and well beyond what would be expected based on the perturbative nature of the approach; non-equilibrium population dynamics calculated with TCL2 for identical parameters are significantly less accurate. For third-order (two-dimensional) spectroscopy, the importance of population dynamics and the violation of the so-called quantum regression theorem degrade the accuracy of TCL2 dynamics. To correct these failures, we combine the TCL2 approach with a classical ensemble sampling of slow microscopic bath degrees of freedom, leading to an efficient hybrid quantum-classical scheme that displays excellent accuracy over a wide range of parameters. In the spectroscopic setting, the success of such a hybrid scheme can be understood through its separate treatment of homogeneous and inhomogeneous broadening. Importantly, the presented approach has the computational scaling of TCL2, with the modest addition of an embarrassingly parallel prefactor associated with ensemble sampling. The presented approach can be understood as a generalized inhomogeneous cumulant expansion technique, capable of treating multilevel systems with non-adiabatic dynamics.

Linear and nonlinear spectroscopy from quantum master equations

NASA Astrophysics Data System (ADS)

Fetherolf, Jonathan H.; Berkelbach, Timothy C.

2017-12-01

We investigate the accuracy of the second-order time-convolutionless (TCL2) quantum master equation for the calculation of linear and nonlinear spectroscopies of multichromophore systems. We show that even for systems with non-adiabatic coupling, the TCL2 master equation predicts linear absorption spectra that are accurate over an extremely broad range of parameters and well beyond what would be expected based on the perturbative nature of the approach; non-equilibrium population dynamics calculated with TCL2 for identical parameters are significantly less accurate. For third-order (two-dimensional) spectroscopy, the importance of population dynamics and the violation of the so-called quantum regression theorem degrade the accuracy of TCL2 dynamics. To correct these failures, we combine the TCL2 approach with a classical ensemble sampling of slow microscopic bath degrees of freedom, leading to an efficient hybrid quantum-classical scheme that displays excellent accuracy over a wide range of parameters. In the spectroscopic setting, the success of such a hybrid scheme can be understood through its separate treatment of homogeneous and inhomogeneous broadening. Importantly, the presented approach has the computational scaling of TCL2, with the modest addition of an embarrassingly parallel prefactor associated with ensemble sampling. The presented approach can be understood as a generalized inhomogeneous cumulant expansion technique, capable of treating multilevel systems with non-adiabatic dynamics.

Markovian master equations for quantum thermal machines: local versus global approach

NASA Astrophysics Data System (ADS)

Hofer, Patrick P.; Perarnau-Llobet, Martí; Miranda, L. David M.; Haack, Géraldine; Silva, Ralph; Bohr Brask, Jonatan; Brunner, Nicolas

2017-12-01

The study of quantum thermal machines, and more generally of open quantum systems, often relies on master equations. Two approaches are mainly followed. On the one hand, there is the widely used, but often criticized, local approach, where machine sub-systems locally couple to thermal baths. On the other hand, in the more established global approach, thermal baths couple to global degrees of freedom of the machine. There has been debate as to which of these two conceptually different approaches should be used in situations out of thermal equilibrium. Here we compare the local and global approaches against an exact solution for a particular class of thermal machines. We consider thermodynamically relevant observables, such as heat currents, as well as the quantum state of the machine. Our results show that the use of a local master equation is generally well justified. In particular, for weak inter-system coupling, the local approach agrees with the exact solution, whereas the global approach fails for non-equilibrium situations. For intermediate coupling, the local and the global approach both agree with the exact solution and for strong coupling, the global approach is preferable. These results are backed by detailed derivations of the regimes of validity for the respective approaches.

On the accuracy of the Padé-resummed master equation approach to dissipative quantum dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hsing-Ta; Reichman, David R.; Berkelbach, Timothy C.

2016-04-21

Well-defined criteria are proposed for assessing the accuracy of quantum master equations whose memory functions are approximated by Padé resummation of the first two moments in the electronic coupling. These criteria partition the parameter space into distinct levels of expected accuracy, ranging from quantitatively accurate regimes to regions of parameter space where the approach is not expected to be applicable. Extensive comparison of Padé-resummed master equations with numerically exact results in the context of the spin–boson model demonstrates that the proposed criteria correctly demarcate the regions of parameter space where the Padé approximation is reliable. The applicability analysis we presentmore » is not confined to the specifics of the Hamiltonian under consideration and should provide guidelines for other classes of resummation techniques.« less

Hierarchical quantum master equation approach to electronic-vibrational coupling in nonequilibrium transport through nanosystems

NASA Astrophysics Data System (ADS)

Schinabeck, C.; Erpenbeck, A.; Härtle, R.; Thoss, M.

2016-11-01

Within the hierarchical quantum master equation (HQME) framework, an approach is presented, which allows a numerically exact description of nonequilibrium charge transport in nanosystems with strong electronic-vibrational coupling. The method is applied to a generic model of vibrationally coupled transport considering a broad spectrum of parameters ranging from the nonadiabatic to the adiabatic regime and including both resonant and off-resonant transport. We show that nonequilibrium effects are important in all these regimes. In particular, in the off-resonant transport regime, the inelastic cotunneling signal is analyzed for a vibrational mode in full nonequilibrium, revealing a complex interplay of different transport processes and deviations from the commonly used G0/2 rule of thumb. In addition, the HQME approach is used to benchmark approximate master equation and nonequilibrium Green's function methods.

Calculating work in weakly driven quantum master equations: Backward and forward equations

NASA Astrophysics Data System (ADS)

Liu, Fei

2016-01-01

I present a technical report indicating that the two methods used for calculating characteristic functions for the work distribution in weakly driven quantum master equations are equivalent. One involves applying the notion of quantum jump trajectory [Phys. Rev. E 89, 042122 (2014), 10.1103/PhysRevE.89.042122], while the other is based on two energy measurements on the combined system and reservoir [Silaev et al., Phys. Rev. E 90, 022103 (2014), 10.1103/PhysRevE.90.022103]. These represent backward and forward methods, respectively, which adopt a very similar approach to that of the Kolmogorov backward and forward equations used in classical stochastic theory. The microscopic basis for the former method is also clarified. In addition, a previously unnoticed equality related to the heat is also revealed.

Simulation of quantum dynamics based on the quantum stochastic differential equation.

PubMed

Li, Ming

2013-01-01

The quantum stochastic differential equation derived from the Lindblad form quantum master equation is investigated. The general formulation in terms of environment operators representing the quantum state diffusion is given. The numerical simulation algorithm of stochastic process of direct photodetection of a driven two-level system for the predictions of the dynamical behavior is proposed. The effectiveness and superiority of the algorithm are verified by the performance analysis of the accuracy and the computational cost in comparison with the classical Runge-Kutta algorithm.

Quantum Chemistry, 5th Edition by Ira N. Levine

NASA Astrophysics Data System (ADS)

Hinde, Robert J.

2000-12-01

Of course, there is no one- or two-week shortcut by which nonspecialists can master enough quantum mechanics to become informed users of quantum chemical techniques. Nevertheless, a text that integrated the fundamentals of quantum theory with a rigorous introduction to quantum chemistry could help instructors design a class that would benefit both these nonspecialists and graduate students in physical chemistry. Could such a class overcome the (undeserved) stigma associated with the physical chemistry curriculum? That remains to be seen.

Non-Markovian stochastic Schrödinger equations: Generalization to real-valued noise using quantum-measurement theory

NASA Astrophysics Data System (ADS)

Gambetta, Jay; Wiseman, H. M.

2002-07-01

Do stochastic Schrödinger equations, also known as unravelings, have a physical interpretation? In the Markovian limit, where the system on average obeys a master equation, the answer is yes. Markovian stochastic Schrödinger equations generate quantum trajectories for the system state conditioned on continuously monitoring the bath. For a given master equation, there are many different unravelings, corresponding to different sorts of measurement on the bath. In this paper we address the non-Markovian case, and in particular the sort of stochastic Schrödinger equation introduced by Strunz, Diósi, and Gisin [Phys. Rev. Lett. 82, 1801 (1999)]. Using a quantum-measurement theory approach, we rederive their unraveling that involves complex-valued Gaussian noise. We also derive an unraveling involving real-valued Gaussian noise. We show that in the Markovian limit, these two unravelings correspond to heterodyne and homodyne detection, respectively. Although we use quantum-measurement theory to define these unravelings, we conclude that the stochastic evolution of the system state is not a true quantum trajectory, as the identity of the state through time is a fiction.

Perturbation expansions of stochastic wavefunctions for open quantum systems

NASA Astrophysics Data System (ADS)

Ke, Yaling; Zhao, Yi

2017-11-01

Based on the stochastic unravelling of the reduced density operator in the Feynman path integral formalism for an open quantum system in touch with harmonic environments, a new non-Markovian stochastic Schrödinger equation (NMSSE) has been established that allows for the systematic perturbation expansion in the system-bath coupling to arbitrary order. This NMSSE can be transformed in a facile manner into the other two NMSSEs, i.e., non-Markovian quantum state diffusion and time-dependent wavepacket diffusion method. Benchmarked by numerically exact results, we have conducted a comparative study of the proposed method in its lowest order approximation, with perturbative quantum master equations in the symmetric spin-boson model and the realistic Fenna-Matthews-Olson complex. It is found that our method outperforms the second-order time-convolutionless quantum master equation in the whole parameter regime and even far better than the fourth-order in the slow bath and high temperature cases. Besides, the method is applicable on an equal footing for any kind of spectral density function and is expected to be a powerful tool to explore the quantum dynamics of large-scale systems, benefiting from the wavefunction framework and the time-local appearance within a single stochastic trajectory.

Dynamics of open quantum systems by interpolation of von Neumann and classical master equations, and its application to quantum annealing

NASA Astrophysics Data System (ADS)

Kadowaki, Tadashi

2018-02-01

We propose a method to interpolate dynamics of von Neumann and classical master equations with an arbitrary mixing parameter to investigate the thermal effects in quantum dynamics. The two dynamics are mixed by intervening to continuously modify their solutions, thus coupling them indirectly instead of directly introducing a coupling term. This maintains the quantum system in a pure state even after the introduction of thermal effects and obtains not only a density matrix but also a state vector representation. Further, we demonstrate that the dynamics of a two-level system can be rewritten as a set of standard differential equations, resulting in quantum dynamics that includes thermal relaxation. These equations are equivalent to the optical Bloch equations at the weak coupling and asymptotic limits, implying that the dynamics cause thermal effects naturally. Numerical simulations of ferromagnetic and frustrated systems support this idea. Finally, we use this method to study thermal effects in quantum annealing, revealing nontrivial performance improvements for a spin glass model over a certain range of annealing time. This result may enable us to optimize the annealing time of real annealing machines.

Accuracy of perturbative master equations.

PubMed

Fleming, C H; Cummings, N I

2011-03-01

We consider open quantum systems with dynamics described by master equations that have perturbative expansions in the system-environment interaction. We show that, contrary to intuition, full-time solutions of order-2n accuracy require an order-(2n+2) master equation. We give two examples of such inaccuracies in the solutions to an order-2n master equation: order-2n inaccuracies in the steady state of the system and order-2n positivity violations. We show how these arise in a specific example for which exact solutions are available. This result has a wide-ranging impact on the validity of coupling (or friction) sensitive results derived from second-order convolutionless, Nakajima-Zwanzig, Redfield, and Born-Markov master equations.

Kraus operator solutions to a fermionic master equation describing a thermal bath and their matrix representation

NASA Astrophysics Data System (ADS)

Xiang-Guo, Meng; Ji-Suo, Wang; Hong-Yi, Fan; Cheng-Wei, Xia

2016-04-01

We solve the fermionic master equation for a thermal bath to obtain its explicit Kraus operator solutions via the fermionic state approach. The normalization condition of the Kraus operators is proved. The matrix representation for these solutions is obtained, which is incongruous with the result in the book completed by Nielsen and Chuang [Quantum Computation and Quantum Information, Cambridge University Press, 2000]. As especial cases, we also present the Kraus operator solutions to master equations for describing the amplitude-decay model and the diffusion process at finite temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11347026), the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2013AM012 and ZR2012AM004), and the Research Fund for the Doctoral Program and Scientific Research Project of Liaocheng University, Shandong Province, China.

Non-additive dissipation in open quantum networks out of equilibrium

NASA Astrophysics Data System (ADS)

Mitchison, Mark T.; Plenio, Martin B.

2018-03-01

We theoretically study a simple non-equilibrium quantum network whose dynamics can be expressed and exactly solved in terms of a time-local master equation. Specifically, we consider a pair of coupled fermionic modes, each one locally exchanging energy and particles with an independent, macroscopic thermal reservoir. We show that the generator of the asymptotic master equation is not additive, i.e. it cannot be expressed as a sum of contributions describing the action of each reservoir alone. Instead, we identify an additional interference term that generates coherences in the energy eigenbasis, associated with the current of conserved particles flowing in the steady state. Notably, non-additivity arises even for wide-band reservoirs coupled arbitrarily weakly to the system. Our results shed light on the non-trivial interplay between multiple thermal noise sources in modular open quantum systems.

Wheeled Pro(p)file of Batalin-Vilkovisky Formalism

NASA Astrophysics Data System (ADS)

Merkulov, S. A.

2010-05-01

Using a technique of wheeled props we establish a correspondence between the homotopy theory of unimodular Lie 1-bialgebras and the famous Batalin-Vilkovisky formalism. Solutions of the so-called quantum master equation satisfying certain boundary conditions are proven to be in 1-1 correspondence with representations of a wheeled dg prop which, on the one hand, is isomorphic to the cobar construction of the prop of unimodular Lie 1-bialgebras and, on the other hand, is quasi-isomorphic to the dg wheeled prop of unimodular Poisson structures. These results allow us to apply properadic methods for computing formulae for a homotopy transfer of a unimodular Lie 1-bialgebra structure on an arbitrary complex to the associated quantum master function on its cohomology. It is proven that in the category of quantum BV manifolds associated with the homotopy theory of unimodular Lie 1-bialgebras quasi-isomorphisms are equivalence relations. It is shown that Losev-Mnev’s BF theory for unimodular Lie algebras can be naturally extended to the case of unimodular Lie 1-bialgebras (and, eventually, to the case of unimodular Poisson structures). Using a finite-dimensional version of the Batalin-Vilkovisky quantization formalism it is rigorously proven that the Feynman integrals computing the effective action of this new BF theory describe precisely homotopy transfer formulae obtained within the wheeled properadic approach to the quantum master equation. Quantum corrections (which are present in our BF model to all orders of the Planck constant) correspond precisely to what are often called “higher Massey products” in the homological algebra.

FAST TRACK COMMUNICATION: Semiclassical Klein Kramers and Smoluchowski equations for the Brownian motion of a particle in an external potential

NASA Astrophysics Data System (ADS)

Coffey, W. T.; Kalmykov, Yu P.; Titov, S. V.; Mulligan, B. P.

2007-01-01

The quantum Brownian motion of a particle in an external potential V(x) is treated using the master equation for the Wigner distribution function W(x, p, t) in phase space (x, p). A heuristic method of determination of diffusion coefficients in the master equation is proposed. The time evolution equation so obtained contains explicit quantum correction terms up to o(planck4) and in the classical limit, planck → 0, reduces to the Klein-Kramers equation. For a quantum oscillator, the method yields an evolution equation for W(x, p, t) coinciding with that of Agarwal (1971 Phys. Rev. A 4 739). In the non-inertial regime, by applying the Brinkman expansion of the momentum distribution in Weber functions (Brinkman 1956 Physica 22 29), the corresponding semiclassical Smoluchowski equation is derived.

Quantum-like model of brain's functioning: decision making from decoherence.

PubMed

Asano, Masanari; Ohya, Masanori; Tanaka, Yoshiharu; Basieva, Irina; Khrennikov, Andrei

2011-07-21

We present a quantum-like model of decision making in games of the Prisoner's Dilemma type. By this model the brain processes information by using representation of mental states in a complex Hilbert space. Driven by the master equation the mental state of a player, say Alice, approaches an equilibrium point in the space of density matrices (representing mental states). This equilibrium state determines Alice's mixed (i.e., probabilistic) strategy. We use a master equation in which quantum physics describes the process of decoherence as the result of interaction with environment. Thus our model is a model of thinking through decoherence of the initially pure mental state. Decoherence is induced by the interaction with memory and the external mental environment. We study (numerically) the dynamics of quantum entropy of Alice's mental state in the process of decision making. We also consider classical entropy corresponding to Alice's choices. We introduce a measure of Alice's diffidence as the difference between classical and quantum entropies of Alice's mental state. We see that (at least in our model example) diffidence decreases (approaching zero) in the process of decision making. Finally, we discuss the problem of neuronal realization of quantum-like dynamics in the brain; especially roles played by lateral prefrontal cortex or/and orbitofrontal cortex. Copyright © 2011 Elsevier Ltd. All rights reserved.

QuTiP: An open-source Python framework for the dynamics of open quantum systems

NASA Astrophysics Data System (ADS)

Johansson, J. R.; Nation, P. D.; Nori, Franco

2012-08-01

We present an object-oriented open-source framework for solving the dynamics of open quantum systems written in Python. Arbitrary Hamiltonians, including time-dependent systems, may be built up from operators and states defined by a quantum object class, and then passed on to a choice of master equation or Monte Carlo solvers. We give an overview of the basic structure for the framework before detailing the numerical simulation of open system dynamics. Several examples are given to illustrate the build up to a complete calculation. Finally, we measure the performance of our library against that of current implementations. The framework described here is particularly well suited to the fields of quantum optics, superconducting circuit devices, nanomechanics, and trapped ions, while also being ideal for use in classroom instruction. Catalogue identifier: AEMB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEMB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 16 482 No. of bytes in distributed program, including test data, etc.: 213 438 Distribution format: tar.gz Programming language: Python Computer: i386, x86-64 Operating system: Linux, Mac OSX, Windows RAM: 2+ Gigabytes Classification: 7 External routines: NumPy (http://numpy.scipy.org/), SciPy (http://www.scipy.org/), Matplotlib (http://matplotlib.sourceforge.net/) Nature of problem: Dynamics of open quantum systems. Solution method: Numerical solutions to Lindblad master equation or Monte Carlo wave function method. Restrictions: Problems must meet the criteria for using the master equation in Lindblad form. Running time: A few seconds up to several tens of minutes, depending on size of underlying Hilbert space.

Efficient quantum state transfer in an engineered chain of quantum bits

NASA Astrophysics Data System (ADS)

Sandberg, Martin; Knill, Emanuel; Kapit, Eliot; Vissers, Michael R.; Pappas, David P.

2016-03-01

We present a method of performing quantum state transfer in a chain of superconducting quantum bits. Our protocol is based on engineering the energy levels of the qubits in the chain and tuning them all simultaneously with an external flux bias. The system is designed to allow sequential adiabatic state transfers, resulting in on-demand quantum state transfer from one end of the chain to the other. Numerical simulations of the master equation using realistic parameters for capacitive nearest-neighbor coupling, energy relaxation, and dephasing show that fast, high-fidelity state transfer should be feasible using this method.

QmeQ 1.0: An open-source Python package for calculations of transport through quantum dot devices

NASA Astrophysics Data System (ADS)

Kiršanskas, Gediminas; Pedersen, Jonas Nyvold; Karlström, Olov; Leijnse, Martin; Wacker, Andreas

2017-12-01

QmeQ is an open-source Python package for numerical modeling of transport through quantum dot devices with strong electron-electron interactions using various approximate master equation approaches. The package provides a framework for calculating stationary particle or energy currents driven by differences in chemical potentials or temperatures between the leads which are tunnel coupled to the quantum dots. The electronic structures of the quantum dots are described by their single-particle states and the Coulomb matrix elements between the states. When transport is treated perturbatively to lowest order in the tunneling couplings, the possible approaches are Pauli (classical), first-order Redfield, and first-order von Neumann master equations, and a particular form of the Lindblad equation. When all processes involving two-particle excitations in the leads are of interest, the second-order von Neumann approach can be applied. All these approaches are implemented in QmeQ. We here give an overview of the basic structure of the package, give examples of transport calculations, and outline the range of applicability of the different approximate approaches.

Eternal non-Markovianity: from random unitary to Markov chain realisations.

PubMed

Megier, Nina; Chruściński, Dariusz; Piilo, Jyrki; Strunz, Walter T

2017-07-25

The theoretical description of quantum dynamics in an intriguing way does not necessarily imply the underlying dynamics is indeed intriguing. Here we show how a known very interesting master equation with an always negative decay rate [eternal non-Markovianity (ENM)] arises from simple stochastic Schrödinger dynamics (random unitary dynamics). Equivalently, it may be seen as arising from a mixture of Markov (semi-group) open system dynamics. Both these approaches lead to a more general family of CPT maps, characterized by a point within a parameter triangle. Our results show how ENM quantum dynamics can be realised easily in the laboratory. Moreover, we find a quantum time-continuously measured (quantum trajectory) realisation of the dynamics of the ENM master equation based on unitary transformations and projective measurements in an extended Hilbert space, guided by a classical Markov process. Furthermore, a Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) representation of the dynamics in an extended Hilbert space can be found, with a remarkable property: there is no dynamics in the ancilla state. Finally, analogous constructions for two qubits extend these results from non-CP-divisible to non-P-divisible dynamics.

Hierarchical Equation of Motion Investigation of Decoherence and Relaxation Dynamics in Nonequilibrium Transport through Interacting Quantum Dots

NASA Astrophysics Data System (ADS)

Hartle, Rainer; Cohen, Guy; Reichman, David R.; Millis, Andrew J.

2014-03-01

A recently developed hierarchical quantum master equation approach is used to investigate nonequilibrium electron transport through an interacting double quantum dot system in the regime where the inter-dot coupling is weaker than the coupling to the electrodes. The corresponding eigenstates provide tunneling paths that may interfere constructively or destructively, depending on the energy of the tunneling electrons. Electron-electron interactions are shown to quench these interference effects in bias-voltage dependent ways, leading, in particular, to negative differential resistance, population inversion and an enhanced broadening of resonances in the respective transport characteristics. Relaxation times are found to be very long, and to be correlated with very slow dynamics of the inter-dot coherences (off diagonal density matrix elements). The ability of the hierarchical quantum master equation approach to access very long time scales is crucial for the study of this physics. This work is supported by the National Science Foundation (NSF DMR-1006282 and NSF CHE-1213247), the Yad Hanadiv-Rothschild Foundation (via a Rothschild Fellowship for GC) and the Alexander von Humboldt Foundation (via a Feodor Lynen fellowship for RH).

Generalized Master Equation with Non-Markovian Multichromophoric Förster Resonance Energy Transfer for Modular Exciton Densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Seogjoo; Hoyer, Stephan; Fleming, Graham

2014-10-31

A generalized master equation (GME) governing quantum evolution of modular exciton density (MED) is derived for large scale light harvesting systems composed of weakly interacting modules of multiple chromophores. The GME-MED offers a practical framework to incorporate real time coherent quantum dynamics calculations of small length scales into dynamics over large length scales, and also provides a non-Markovian generalization and rigorous derivation of the Pauli master equation employing multichromophoric Förster resonance energy transfer rates. A test of the GME-MED for four sites of the Fenna-Matthews-Olson complex demonstrates how coherent dynamics of excitonic populations over coupled chromophores can be accurately describedmore » by transitions between subgroups (modules) of delocalized excitons. Application of the GME-MED to the exciton dynamics between a pair of light harvesting complexes in purple bacteria demonstrates its promise as a computationally efficient tool to investigate large scale exciton dynamics in complex environments.« less

Stability of continuous-time quantum filters with measurement imperfections

NASA Astrophysics Data System (ADS)

Amini, H.; Pellegrini, C.; Rouchon, P.

2014-07-01

The fidelity between the state of a continuously observed quantum system and the state of its associated quantum filter, is shown to be always a submartingale. The observed system is assumed to be governed by a continuous-time Stochastic Master Equation (SME), driven simultaneously by Wiener and Poisson processes and that takes into account incompleteness and errors in measurements. This stability result is the continuous-time counterpart of a similar stability result already established for discrete-time quantum systems and where the measurement imperfections are modelled by a left stochastic matrix.

Quantum simulation of dissipative processes without reservoir engineering

DOE PAGES

Di Candia, R.; Pedernales, J. S.; del Campo, A.; ...

2015-05-29

We present a quantum algorithm to simulate general finite dimensional Lindblad master equations without the requirement of engineering the system-environment interactions. The proposed method is able to simulate both Markovian and non-Markovian quantum dynamics. It consists in the quantum computation of the dissipative corrections to the unitary evolution of the system of interest, via the reconstruction of the response functions associated with the Lindblad operators. Our approach is equally applicable to dynamics generated by effectively non-Hermitian Hamiltonians. We confirm the quality of our method providing specific error bounds that quantify its accuracy.

Non-Markovian quantum Brownian motion in one dimension in electric fields

NASA Astrophysics Data System (ADS)

Shen, H. Z.; Su, S. L.; Zhou, Y. H.; Yi, X. X.

2018-04-01

Quantum Brownian motion is the random motion of quantum particles suspended in a field (or an effective field) resulting from their collision with fast-moving modes in the field. It provides us with a fundamental model to understand various physical features concerning open systems in chemistry, condensed-matter physics, biophysics, and optomechanics. In this paper, without either the Born-Markovian or rotating-wave approximation, we derive a master equation for a charged-Brownian particle in one dimension coupled with a thermal reservoir in electric fields. The effect of the reservoir and the electric fields is manifested as time-dependent coefficients and coherent terms, respectively, in the master equation. The two-photon correlation between the Brownian particle and the reservoir can induce nontrivial squeezing dynamics to the particle. We derive a current equation including the source from the driving fields, transient current from the system flowing into the environment, and the two-photon current caused by the non-rotating-wave term. The presented results then are compared with that given by the rotating-wave approximation in the weak-coupling limit, and these results are extended to a more general quantum network involving an arbitrary number of coupled-Brownian particles. The presented formalism might open a way to better understand exactly the non-Markovian quantum network.

Multiple re-encounter approach to radical pair reactions and the role of nonlinear master equations.

PubMed

Clausen, Jens; Guerreschi, Gian Giacomo; Tiersch, Markus; Briegel, Hans J

2014-08-07

We formulate a multiple-encounter model of the radical pair mechanism that is based on a random coupling of the radical pair to a minimal model environment. These occasional pulse-like couplings correspond to the radical encounters and give rise to both dephasing and recombination. While this is in agreement with the original model of Haberkorn and its extensions that assume additional dephasing, we show how a nonlinear master equation may be constructed to describe the conditional evolution of the radical pairs prior to the detection of their recombination. We propose a nonlinear master equation for the evolution of an ensemble of independently evolving radical pairs whose nonlinearity depends on the record of the fluorescence signal. We also reformulate Haberkorn's original argument on the physicality of reaction operators using the terminology of quantum optics/open quantum systems. Our model allows one to describe multiple encounters within the exponential model and connects this with the master equation approach. We include hitherto neglected effects of the encounters, such as a separate dephasing in the triplet subspace, and predict potential new effects, such as Grover reflections of radical spins, that may be observed if the strength and time of the encounters can be experimentally controlled.

Quantum dynamics of a two-atom-qubit system

NASA Astrophysics Data System (ADS)

Van Hieu, Nguyen; Bich Ha, Nguyen; Linh, Le Thi Ha

2009-09-01

A physical model of the quantum information exchange between two qubits is studied theoretically. The qubits are two identical two-level atoms, the physical mechanism of the quantum information exchange is the mutual dependence of the reduced density matrices of two qubits generated by their couplings with a multimode radiation field. The Lehmberg-Agarwal master equation is exactly solved. The explicit form of the mutual dependence of two reduced density matrices is established. The application to study the entanglement of two qubits is discussed.

Current rectification in a double quantum dot through fermionic reservoir engineering

NASA Astrophysics Data System (ADS)

Malz, Daniel; Nunnenkamp, Andreas

2018-04-01

Reservoir engineering is a powerful tool for the robust generation of quantum states or transport properties. Using both a weak-coupling quantum master equation and the exact solution, we show that directional transport of electrons through a double quantum dot can be achieved through an appropriately designed electronic environment. Directionality is attained through the interference of coherent and dissipative coupling. The relative phase is tuned with an external magnetic field, such that directionality can be reversed, as well as turned on and off dynamically. Our work introduces fermionic-reservoir engineering, paving the way to a new class of nanoelectronic devices.

Generalized Gibbs state with modified Redfield solution: Exact agreement up to second order

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thingna, Juzar; Wang, Jian-Sheng; Haenggi, Peter

A novel scheme for the steady state solution of the standard Redfield quantum master equation is developed which yields agreement with the exact result for the corresponding reduced density matrix up to second order in the system-bath coupling strength. We achieve this objective by use of an analytic continuation of the off-diagonal matrix elements of the Redfield solution towards its diagonal limit. Notably, our scheme does not require the provision of yet higher order relaxation tensors. Testing this modified method for a heat bath consisting of a collection of harmonic oscillators we assess that the system relaxes towards its correctmore » coupling-dependent, generalized quantum Gibbs state in second order. We numerically compare our formulation for a damped quantum harmonic system with the nonequilibrium Green's function formalism: we find good agreement at low temperatures for coupling strengths that are even larger than expected from the very regime of validity of the second-order Redfield quantum master equation. Yet another advantage of our method is that it markedly reduces the numerical complexity of the problem; thus, allowing to study efficiently large-sized system Hilbert spaces.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao Xiaoqiang; Wang Hongfu; Zhang Shou

We present an approach for implementation of a 1->3 orbital state quantum cloning machine based on the quantum Zeno dynamics via manipulating three rf superconducting quantum interference device (SQUID) qubits to resonantly interact with a superconducting cavity assisted by classical fields. Through appropriate modulation of the coupling constants between rf SQUIDs and classical fields, the quantum cloning machine can be realized within one step. We also discuss the effects of decoherence such as spontaneous emission and the loss of cavity in virtue of master equation. The numerical simulation result reveals that the quantum cloning machine is especially robust against themore » cavity decay, since all qubits evolve in the decoherence-free subspace with respect to cavity decay due to the quantum Zeno dynamics.« less

Ultrastable light sources in the crossover from superradiance to lasing

NASA Astrophysics Data System (ADS)

Xu, Minghui; Tieri, David; Holland, Murray

2013-05-01

We theoretically investigate the crossover from steady-state superradiance to optical lasing. An exact solution of the quantum master equation is difficult to obtain due to the exponential scaling of the Hilbert space dimension with system size. However, since Lindblad operators in the master equation are invariant under SU(4) transformations, we are able to reduce the exponential scaling of the problem to cubic by expanding the density matrix in terms of an SU(4) basis. In this way, we obtain exact quantum solutions of the superradiance-laser crossover. We use this theory to investigate the potential for ultrastable lasers in the millihertz linewidth regime, and find the behavior of important observables, such as intensity, linewidth, spin-correlation, and entanglement. This work was supported by the DARPA QUASAR program and NSF.

Terahertz master-oscillator power-amplifier quantum cascade laser with a grating coupler of extremely low reflectivity.

PubMed

Zhu, Huan; Zhu, Haiqing; Wang, Fangfang; Chang, Gaolei; Yu, Chenren; Yan, Quan; Chen, Jianxin; Li, Lianhe; Davies, A Giles; Linfield, Edmund H; Tang, Zhou; Chen, Pingping; Lu, Wei; Xu, Gangyi; He, Li

2018-01-22

A terahertz master-oscillation power-amplifier quantum cascade laser (THz-MOPA-QCL) is demonstrated where a grating coupler is employed to efficiently extract the THz radiation. By maximizing the group velocity and eliminating the scattering of THz wave in the grating coupler, the residue reflectivity is reduced down to the order of 10 -3 . A buried DFB grating and a tapered preamplifier are proposed to improve the seed power and to reduce the gain saturation, respectively. The THz-MOPA-QCL exhibits single-mode emission, a single-lobed beam with a narrow divergence angle of 18° × 16°, and a pulsed output power of 136 mW at 20 K, which is 36 times that of a second-order DFB laser from the same material.

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

PubMed

Kim, Jimyung; Delfyett, Peter J

2008-07-21

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

Quantum information processing in the radical-pair mechanism: Haberkorn's theory violates the Ozawa entropy bound

NASA Astrophysics Data System (ADS)

Mouloudakis, K.; Kominis, I. K.

2017-02-01

Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We show here that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures, and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction. By considering Groenewold's information, the quantum information extracted during the reaction, we reproduce the known and unravel other magnetic-field effects not conveyed by reaction yields.

Application of quantum master equation for long-term prognosis of asset-prices

NASA Astrophysics Data System (ADS)

Khrennikova, Polina

2016-05-01

This study combines the disciplines of behavioral finance and an extension of econophysics, namely the concepts and mathematical structure of quantum physics. We apply the formalism of quantum theory to model the dynamics of some correlated financial assets, where the proposed model can be potentially applied for developing a long-term prognosis of asset price formation. At the informational level, the asset price states interact with each other by the means of a ;financial bath;. The latter is composed of agents' expectations about the future developments of asset prices on the finance market, as well as financially important information from mass-media, society, and politicians. One of the essential behavioral factors leading to the quantum-like dynamics of asset prices is the irrationality of agents' expectations operating on the finance market. These expectations lead to a deeper type of uncertainty concerning the future price dynamics of the assets, than given by a classical probability theory, e.g., in the framework of the classical financial mathematics, which is based on the theory of stochastic processes. The quantum dimension of the uncertainty in price dynamics is expressed in the form of the price-states superposition and entanglement between the prices of the different financial assets. In our model, the resolution of this deep quantum uncertainty is mathematically captured with the aid of the quantum master equation (its quantum Markov approximation). We illustrate our model of preparation of a future asset price prognosis by a numerical simulation, involving two correlated assets. Their returns interact more intensively, than understood by a classical statistical correlation. The model predictions can be extended to more complex models to obtain price configuration for multiple assets and portfolios.

Quantum transport under ac drive from the leads: A Redfield quantum master equation approach

NASA Astrophysics Data System (ADS)

Purkayastha, Archak; Dubi, Yonatan

2017-08-01

Evaluating the time-dependent dynamics of driven open quantum systems is relevant for a theoretical description of many systems, including molecular junctions, quantum dots, cavity-QED experiments, cold atoms experiments, and more. Here, we formulate a rigorous microscopic theory of an out-of-equilibrium open quantum system of noninteracting particles on a lattice weakly coupled bilinearly to multiple baths and driven by periodically varying thermodynamic parameters like temperature and chemical potential of the bath. The particles can be either bosonic or fermionic and the lattice can be of any dimension and geometry. Based on the Redfield quantum master equation under Born-Markov approximation, we derive a linear differential equation for an equal time two point correlation matrix, sometimes also called a single-particle density matrix, from which various physical observables, for example, current, can be calculated. Various interesting physical effects, such as resonance, can be directly read off from the equations. Thus, our theory is quite general and gives quite transparent and easy-to-calculate results. We validate our theory by comparing with exact numerical simulations. We apply our method to a generic open quantum system, namely, a double quantum dot coupled to leads with modulating chemical potentials. The two most important experimentally relevant insights from this are as follows: (i) Time-dependent measurements of current for symmetric oscillating voltages (with zero instantaneous voltage bias) can point to the degree of asymmetry in the system-bath coupling and (ii) under certain conditions time-dependent currents can exceed time-averaged currents by several orders of magnitude, and can therefore be detected even when the average current is below the measurement threshold.

Evolution of quantum-like modeling in decision making processes

NASA Astrophysics Data System (ADS)

Khrennikova, Polina

2012-12-01

The application of the mathematical formalism of quantum mechanics to model behavioral patterns in social science and economics is a novel and constantly emerging field. The aim of the so called 'quantum like' models is to model the decision making processes in a macroscopic setting, capturing the particular 'context' in which the decisions are taken. Several subsequent empirical findings proved that when making a decision people tend to violate the axioms of expected utility theory and Savage's Sure Thing principle, thus violating the law of total probability. A quantum probability formula was devised to describe more accurately the decision making processes. A next step in the development of QL-modeling in decision making was the application of Schrödinger equation to describe the evolution of people's mental states. A shortcoming of Schrödinger equation is its inability to capture dynamics of an open system; the brain of the decision maker can be regarded as such, actively interacting with the external environment. Recently the master equation, by which quantum physics describes the process of decoherence as the result of interaction of the mental state with the environmental 'bath', was introduced for modeling the human decision making. The external environment and memory can be referred to as a complex 'context' influencing the final decision outcomes. The master equation can be considered as a pioneering and promising apparatus for modeling the dynamics of decision making in different contexts.

Open groups of constraints. Integrating arbitrary involutions

NASA Astrophysics Data System (ADS)

Batalin, Igor; Marnelius, Robert

1998-11-01

A new type of quantum master equation is presented which is expressed in terms of a recently introduced quantum antibracket. The equation involves only two operators: an extended nilpotent BFV-BRST charge and an extended ghost charge. It is proposed to determine the generalized quantum Maurer-Cartan equations for arbitrary open groups. These groups are the integration of constraints in arbitrary involutions. The only condition for this is that the constraint operators may be embedded in an odd nilpotent operator, the BFV-BRST charge. The proposal is verified at the quasigroup level. The integration formulas are also used to construct a generating operator for quantum antibrackets of operators in arbitrary involutions.

Quantum Prisoners' Dilemma in Fluctuating Massless Scalar Field

NASA Astrophysics Data System (ADS)

Huang, Zhiming

2017-12-01

Quantum systems are easily affected by external environment. In this paper, we investigate the influences of external massless scalar field to quantum Prisoners' Dilemma (QPD) game. We firstly derive the master equation that describes the system evolution with initial maximally entangled state. Then, we discuss the effects of a fluctuating massless scalar field on the game's properties such as payoff, Nash equilibrium, and symmetry. We find that for different game strategies, vacuum fluctuation has different effects on payoff. Nash equilibrium is broken but the symmetry of the game is not violated.

Nonequilibrium-thermodynamics approach to open quantum systems

NASA Astrophysics Data System (ADS)

Semin, Vitalii; Petruccione, Francesco

2014-11-01

Open quantum systems are studied from the thermodynamical point of view unifying the principle of maximum informational entropy and the hypothesis of relaxation times hierarchy. The result of the unification is a non-Markovian and local-in-time master equation that provides a direct connection for dynamical and thermodynamical properties of open quantum systems. The power of the approach is illustrated by the application to the damped harmonic oscillator and the damped driven two-level system, resulting in analytical expressions for the non-Markovian and nonequilibrium entropy and inverse temperature.

Dark channels in resonant tunneling transport through artificial atoms.

PubMed

Vaz, Eduardo; Kyriakidis, Jordan

2008-07-14

We investigate sequential tunneling through a multilevel quantum dot confining multiple electrons in the regime where several channels are available for transport within the bias window. By analyzing solutions to the master equations of the reduced density matrix, we give general conditions on when the presence of a second transport channel in the bias window quenches transport through the quantum dot. These conditions are in terms of distinct tunneling anisotropies which may aid in explaining the occurrence of negative differential conductance in quantum dots in the nonlinear regime.

Shot-noise at a Fermi-edge singularity: Non-Markovian dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ubbelohde, N.; Maire, N.; Haug, R. J.

2013-12-04

For an InAs quantum dot we study the current shot noise at a Fermi-edge singularity in low temperature cross-correlation measurements. In the regime of the interaction effect the strong suppression of noise observed at zero magnetic field and the sequence of enhancement and suppression in magnetic field go beyond a Markovian master equation model. Qualitative and quantitative agreement can however be achieved by a generalized master equation model taking non-Markovian dynamics into account.

Quantum friction in arbitrarily directed motion

DOE PAGES

Klatt, J.; Farías, M. Belen; Dalvit, D. A. R.; ...

2017-05-30

In quantum friction, the electromagnetic fluctuation-induced frictional force decelerating an atom which moves past a macroscopic dielectric body, has so far eluded experimental evidence despite more than three decades of theoretical studies. Inspired by the recent finding that dynamical corrections to such an atom's internal dynamics are enhanced by one order of magnitude for vertical motion—compared with the paradigmatic setup of parallel motion—here we generalize quantum friction calculations to arbitrary angles between the atom's direction of motion and the surface in front of which it moves. Motivated by the disagreement between quantum friction calculations based on Markovian quantum master equationsmore » and time-dependent perturbation theory, we carry out our derivations of the quantum frictional force for arbitrary angles by employing both methods and compare them.« less

Non-Markovian Investigation of an Autonomous Quantum Heat Engine

NASA Astrophysics Data System (ADS)

Goyal, Ketan

A systematic study of a quantum heat engine is presented in this thesis. In particular, we study heat conduction through a two-two level composite system, which is then connected to a photon cavity to extract work, forming an autonomous quantum heat engine. The question as to what extent quantum effects such as quantum coherence and correlations impact thermodynamic properties of such a system is addressed. The investigated heat engine has been previously studied using the popular Born-Markovian quantum master equation under weak internal coupling approximation. However, we show that the used approach is quite limited in addressing such problems as it is incapable of correctly accounting for the quantum effects. By using a non-Markovian approach involving hierarchical equations of motion, we show that quantum coherence and correlations between system and environments play a significant role in energy transfer processes of heat conduction and work.

High fidelity quantum teleportation assistance with quantum neural network

NASA Astrophysics Data System (ADS)

Huang, Chunhui; Wu, Bichun

2014-09-01

In this paper, a high fidelity scheme of quantum teleportation based on quantum neural network (QNN) is proposed. The QNN is composed of multi-bit control-not gates. The quantum teleportation of a qubit state via two-qubit entangled channels is investigated by solving the master equation in Lindblad operators with a noisy environment. To ensure the security of quantum teleportation, the indirect training of QNN is employed. Only 10% of teleported information is extracted for the training of QNN parameters. Then the outputs are corrected by the other QNN at Bob's side. We build a random series of numbers ranged in [0, π] as inputs and simulate the properties of our teleportation scheme. The results show that the fidelity of quantum teleportation system is significantly improved to approach 1 by the error-correction of QNN. It illustrates that the distortion can be eliminated perfectly and the high fidelity of quantum teleportation could be implemented.

Steady bipartite coherence induced by non-equilibrium environment

NASA Astrophysics Data System (ADS)

Huangfu, Yong; Jing, Jun

2018-01-01

We study the steady state of two coupled two-level atoms interacting with a non-equilibrium environment that consists of two heat baths at different temperatures. Specifically, we analyze four cases with respect to the configuration about the interactions between atoms and heat baths. Using secular approximation, the conventional master equation usually neglects steady-state coherence, even when the system is coupled with a non-equilibrium environment. When employing the master equation with no secular approximation, we find that the system coherence in our model, denoted by the off-diagonal terms in the reduced density matrix spanned by the eigenvectors of the system Hamiltonian, would survive after a long-time decoherence evolution. The absolute value of residual coherence in the system relies on different configurations of interaction channels between the system and the heat baths. We find that a large steady quantum coherence term can be achieved when the two atoms are resonant. The absolute value of quantum coherence decreases in the presence of additional atom-bath interaction channels. Our work sheds new light on the mechanism of steady-state coherence in microscopic quantum systems in non-equilibrium environments.

The weak coupling limit as a quantum functional central limit

NASA Astrophysics Data System (ADS)

Accardi, L.; Frigerio, A.; Lu, Y. G.

1990-08-01

We show that, in the weak coupling limit, the laser model process converges weakly in the sense of the matrix elements to a quantum diffusion whose equation is explicitly obtained. We prove convergence, in the same sense, of the Heisenberg evolution of an observable of the system to the solution of a quantum Langevin equation. As a corollary of this result, via the quantum Feynman-Kac technique, one can recover previous results on the quantum master equation for reduced evolutions of open systems. When applied to some particular model (e.g. the free Boson gas) our results allow to interpret the Lamb shift as an Ito correction term and to express the pumping rates in terms of quantities related to the original Hamiltonian model.

Quantum dynamics intervened by repeated nonselective measurements

NASA Astrophysics Data System (ADS)

Filippov, Sergey N.

We derive the theory of open quantum system dynamics intervened by a series of nonselective measurements. We analyze the cases of time-independent and time-dependent Hamiltonian dynamics between the measurements and find the approximate master equation in the stroboscopic limit. We also consider a situation, in which the measurement basis changes in time, and illustrate it by nonselective measurements in the basis of diabatic states of the Landau-Zener model.

A quantum extended Kalman filter

NASA Astrophysics Data System (ADS)

Emzir, Muhammad F.; Woolley, Matthew J.; Petersen, Ian R.

2017-06-01

In quantum physics, a stochastic master equation (SME) estimates the state (density operator) of a quantum system in the Schrödinger picture based on a record of measurements made on the system. In the Heisenberg picture, the SME is a quantum filter. For a linear quantum system subject to linear measurements and Gaussian noise, the dynamics may be described by quantum stochastic differential equations (QSDEs), also known as quantum Langevin equations, and the quantum filter reduces to a so-called quantum Kalman filter. In this article, we introduce a quantum extended Kalman filter (quantum EKF), which applies a commutative approximation and a time-varying linearization to systems of nonlinear QSDEs. We will show that there are conditions under which a filter similar to a classical EKF can be implemented for quantum systems. The boundedness of estimation errors and the filtering problem with ‘state-dependent’ covariances for process and measurement noises are also discussed. We demonstrate the effectiveness of the quantum EKF by applying it to systems that involve multiple modes, nonlinear Hamiltonians, and simultaneous jump-diffusive measurements.

Open Group Transformations Within the Sp(2)-Formalism

NASA Astrophysics Data System (ADS)

Batalin, Igor; Marnelius, Robert

Previously we have shown that open groups whose generators are in arbitrary involutions may be quantized within a ghost extended framework in terms of the nilpotent BFV-BRST charge operator. Here we show that they may also be quantized within an Sp(2)-frame in which there are two odd anticommuting operators called Sp(2)-charges. Previous results for finite open group transformations are generalized to the Sp(2)-formalism. We show that in order to define open group transformations on the whole ghost extended space we need Sp(2)-charges in the nonminimal sector which contains dynamical Lagrange multipliers. We give an Sp(2)-version of the quantum master equation with extended Sp(2)-charges and a master charge of a more involved form, which is proposed to represent the integrability conditions of defining operators of connection operators and which therefore should encode the generalized quantum Maurer-Cartan equations for arbitrary open groups. General solutions of this master equation are given in explicit form. A further extended Sp(2)-formalism is proposed in which the group parameters are quadrupled to a supersymmetric set and from which all results may be derived.

Convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation and rate constants: Case study of the spin-boson model.

PubMed

Xu, Meng; Yan, Yaming; Liu, Yanying; Shi, Qiang

2018-04-28

The Nakajima-Zwanzig generalized master equation provides a formally exact framework to simulate quantum dynamics in condensed phases. Yet, the exact memory kernel is hard to obtain and calculations based on perturbative expansions are often employed. By using the spin-boson model as an example, we assess the convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation. The exact memory kernels are calculated by combining the hierarchical equation of motion approach and the Dyson expansion of the exact memory kernel. High order expansions of the memory kernels are obtained by extending our previous work to calculate perturbative expansions of open system quantum dynamics [M. Xu et al., J. Chem. Phys. 146, 064102 (2017)]. It is found that the high order expansions do not necessarily converge in certain parameter regimes where the exact kernel show a long memory time, especially in cases of slow bath, weak system-bath coupling, and low temperature. Effectiveness of the Padé and Landau-Zener resummation approaches is tested, and the convergence of higher order rate constants beyond Fermi's golden rule is investigated.

Convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation and rate constants: Case study of the spin-boson model

NASA Astrophysics Data System (ADS)

Xu, Meng; Yan, Yaming; Liu, Yanying; Shi, Qiang

2018-04-01

The Nakajima-Zwanzig generalized master equation provides a formally exact framework to simulate quantum dynamics in condensed phases. Yet, the exact memory kernel is hard to obtain and calculations based on perturbative expansions are often employed. By using the spin-boson model as an example, we assess the convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation. The exact memory kernels are calculated by combining the hierarchical equation of motion approach and the Dyson expansion of the exact memory kernel. High order expansions of the memory kernels are obtained by extending our previous work to calculate perturbative expansions of open system quantum dynamics [M. Xu et al., J. Chem. Phys. 146, 064102 (2017)]. It is found that the high order expansions do not necessarily converge in certain parameter regimes where the exact kernel show a long memory time, especially in cases of slow bath, weak system-bath coupling, and low temperature. Effectiveness of the Padé and Landau-Zener resummation approaches is tested, and the convergence of higher order rate constants beyond Fermi's golden rule is investigated.

Noise induced quantum effects in photosynthetic complexes

NASA Astrophysics Data System (ADS)

Dorfman, Konstantin; Voronine, Dmitri; Mukamel, Shaul; Scully, Marlan

2012-02-01

Recent progress in coherent multidimensional optical spectroscopy revealed effects of quantum coherence coupled to population leading to population oscillations as evidence of quantum transport. Their description requires reevaluation of the currently used methods and approximations. We identify couplings between coherences and populations as the noise-induced cross-terms in the master equation generated via Agarwal-Fano interference that have been shown earlier to enhance the quantum yield in a photocell. We investigated a broad range of typical parameter regimes, which may be applied to a variety of photosynthetic complexes. We demonstrate that quantum coherence may be induced in photosynthetic complexes under natural conditions of incoherent light from the sun. This demonstrates that a photosynthetic reaction center may be viewed as a biological quantum heat engine that transforms high-energy thermal photon radiation into low entropy electron flux.

Bath-induced correlations in an infinite-dimensional Hilbert space

NASA Astrophysics Data System (ADS)

Nizama, Marco; Cáceres, Manuel O.

2017-09-01

Quantum correlations between two free spinless dissipative distinguishable particles (interacting with a thermal bath) are studied analytically using the quantum master equation and tools of quantum information. Bath-induced coherence and correlations in an infinite-dimensional Hilbert space are shown. We show that for temperature T> 0 the time-evolution of the reduced density matrix cannot be written as the direct product of two independent particles. We have found a time-scale that characterizes the time when the bath-induced coherence is maximum before being wiped out by dissipation (purity, relative entropy, spatial dispersion, and mirror correlations are studied). The Wigner function associated to the Wannier lattice (where the dissipative quantum walks move) is studied as an indirect measure of the induced correlations among particles. We have supported the quantum character of the correlations by analyzing the geometric quantum discord.

Quantum Brownian motion with inhomogeneous damping and diffusion

NASA Astrophysics Data System (ADS)

Massignan, Pietro; Lampo, Aniello; Wehr, Jan; Lewenstein, Maciej

2015-03-01

We analyze the microscopic model of quantum Brownian motion, describing a Brownian particle interacting with a bosonic bath through a coupling which is linear in the creation and annihilation operators of the bath, but may be a nonlinear function of the position of the particle. Physically, this corresponds to a configuration in which damping and diffusion are spatially inhomogeneous. We derive systematically the quantum master equation for the Brownian particle in the Born-Markov approximation and we discuss the appearance of additional terms, for various polynomials forms of the coupling. We discuss the cases of linear and quadratic coupling in great detail and we derive, using Wigner function techniques, the stationary solutions of the master equation for a Brownian particle in a harmonic trapping potential. We predict quite generally Gaussian stationary states, and we compute the aspect ratio and the spread of the distributions. In particular, we find that these solutions may be squeezed (superlocalized) with respect to the position of the Brownian particle. We analyze various restrictions to the validity of our theory posed by non-Markovian effects and by the Heisenberg principle. We further study the dynamical stability of the system, by applying a Gaussian approximation to the time-dependent Wigner function, and we compute the decoherence rates of coherent quantum superpositions in position space. Finally, we propose a possible experimental realization of the physics discussed here, by considering an impurity particle embedded in a degenerate quantum gas.

On the Perturbative Equivalence Between the Hamiltonian and Lagrangian Quantizations

NASA Astrophysics Data System (ADS)

Batalin, I. A.; Tyutin, I. V.

The Hamiltonian (BFV) and Lagrangian (BV) quantization schemes are proved to be perturbatively equivalent to each other. It is shown in particular that the quantum master equation being treated perturbatively possesses a local formal solution.

Stabilization of the Simplest Criegee Intermediate from the Reaction between Ozone and Ethylene: A High-Level Quantum Chemical and Kinetic Analysis of Ozonolysis.

PubMed

Nguyen, Thanh Lam; Lee, Hyunwoo; Matthews, Devin A; McCarthy, Michael C; Stanton, John F

2015-06-04

The fraction of the collisionally stabilized Criegee species CH2OO produced from the ozonolysis of ethylene is calculated using a two-dimensional (E, J)-grained master equation technique and semiclassical transition-state theory based on the potential energy surface obtained from high-accuracy quantum chemical calculations. Our calculated yield of 42 ± 6% for the stabilized CH2OO agrees well, within experimental error, with available (indirect) experimental results. Inclusion of angular momentum in the master equation is found to play an essential role in bringing the theoretical results into agreement with the experiment. Additionally, yields of HO and HO2 radical products are predicted to be 13 ± 6% and 17 ± 6%, respectively. In the kinetic simulation, the HO radical product is produced mostly from the stepwise decomposition mechanism of primary ozonide rather than from dissociation of hot CH2OO.

BFV quantization on hermitian symmetric spaces

NASA Astrophysics Data System (ADS)

Fradkin, E. S.; Linetsky, V. Ya.

1995-02-01

Gauge-invariant BFV approach to geometric quantization is applied to the case of hermitian symmetric spaces G/ H. In particular, gauge invariant quantization on the Lobachevski plane and sphere is carried out. Due to the presence of symmetry, master equations for the first-class constraints, quantum observables and physical quantum states are exactly solvable. BFV-BRST operator defines a flat G-connection in the Fock bundle over G/ H. Physical quantum states are covariantly constant sections with respect to this connection and are shown to coincide with the generalized coherent states for the group G. Vacuum expectation values of the quantum observables commuting with the quantum first-class constraints reduce to the covariant symbols of Berezin. The gauge-invariant approach to quantization on symplectic manifolds synthesizes geometric, deformation and Berezin quantization approaches.

Hybrid quantum-classical modeling of quantum dot devices

NASA Astrophysics Data System (ADS)

Kantner, Markus; Mittnenzweig, Markus; Koprucki, Thomas

2017-11-01

The design of electrically driven quantum dot devices for quantum optical applications asks for modeling approaches combining classical device physics with quantum mechanics. We connect the well-established fields of semiclassical semiconductor transport theory and the theory of open quantum systems to meet this requirement. By coupling the van Roosbroeck system with a quantum master equation in Lindblad form, we introduce a new hybrid quantum-classical modeling approach, which provides a comprehensive description of quantum dot devices on multiple scales: it enables the calculation of quantum optical figures of merit and the spatially resolved simulation of the current flow in realistic semiconductor device geometries in a unified way. We construct the interface between both theories in such a way, that the resulting hybrid system obeys the fundamental axioms of (non)equilibrium thermodynamics. We show that our approach guarantees the conservation of charge, consistency with the thermodynamic equilibrium and the second law of thermodynamics. The feasibility of the approach is demonstrated by numerical simulations of an electrically driven single-photon source based on a single quantum dot in the stationary and transient operation regime.

Non-Markovian dynamics of open quantum systems

NASA Astrophysics Data System (ADS)

Fleming, Chris H.

An open quantum system is a quantum system that interacts with some environment whose degrees of freedom have been coarse grained away. This model describes non-equilibrium processes more general than scattering-matrix formulations. Furthermore, the microscopically-derived environment provides a model of noise, dissipation and decoherence far more general than Markovian (white noise) models. The latter are fully characterized by Lindblad equations and can be motivated phenomenologically. Non-Markovian processes consistently account for backreaction with the environment and can incorporate effects such as finite temperature and spatial correlations. We consider linear systems with bilinear coupling to the environment, or quantum Brownian motion, and nonlinear systems with weak coupling to the environment. For linear systems we provide exact solutions with analytical results for a variety of spectral densities. Furthermore, we point out an important mathematical subtlety which led to incorrect master-equation coefficients in earlier derivations, given nonlocal dissipation. For nonlinear systems we provide perturbative solutions by translating the formalism of canonical perturbation theory into the context of master equations. It is shown that unavoidable degeneracy causes an unfortunate reduction in accuracy between perturbative master equations and their solutions. We also extend the famous theorem of Lindblad, Gorini, Kossakowski and Sudarshan on completely positivity to non-Markovian master equations. Our application is primarily to model atoms interacting via a common electromagnetic field. The electromagnetic field contains correlations in both space and time, which are related to its relativistic (photon-mediated) nature. As such, atoms residing in the same field experience different environmental effects depending upon their relative position and orientation. Our more accurate solutions were necessary to assess sudden death of entanglement at zero temperature. In contrast to previous claims, we found that all initial states of two-level atoms undergo finite-time disentanglement. We were also able to access regimes which cannot be described by Lindblad equations and other simpler methods, such as near resonance. Finally we revisit the infamous Abraham-Lorentz force, wherein a single particle in motion experiences backreaction from the electromagnetic field. This leads to a number of well-known problems including pre-acceleration and runaway solutions. We found a more a more-suitable open-system treatment of the nonrelativistic particle to be perfectly causal and dissipative without any extraneous requirements for finite size of the particle, weak coupling to the field, etc..

Dynamics and thermodynamics of linear quantum open systems.

PubMed

Martinez, Esteban A; Paz, Juan Pablo

2013-03-29

We analyze the evolution of the quantum state of networks of quantum oscillators coupled with arbitrary external environments. We show that the reduced density matrix of the network always obeys a local master equation with a simple analytical solution. We use this to study the emergence of thermodynamical laws in the long time regime demonstrating two main results: First, we show that it is impossible to build a quantum absorption refrigerator using linear networks (thus, nonlinearity is an essential resource for such refrigerators recently studied by Levy and Kosloff [Phys. Rev. Lett. 108, 070604 (2012)] and Levy et al. [Phys. Rev. B 85, 061126 (2012)]). Then, we show that the third law imposes constraints on the low frequency behavior of the environmental spectral densities.

Delayed feedback control in quantum transport.

PubMed

Emary, Clive

2013-09-28

Feedback control in quantum transport has been predicted to give rise to several interesting effects, among them quantum state stabilization and the realization of a mesoscopic Maxwell's daemon. These results were derived under the assumption that control operations on the system are affected instantaneously after the measurement of electronic jumps through it. In this contribution, I describe how to include a delay between detection and control operation in the master equation theory of feedback-controlled quantum transport. I investigate the consequences of delay for the state stabilization and Maxwell's daemon schemes. Furthermore, I describe how delay can be used as a tool to probe coherent oscillations of electrons within a transport system and how this formalism can be used to model finite detector bandwidth.

Multistate and multihypothesis discrimination with open quantum systems

NASA Astrophysics Data System (ADS)

Kiilerich, Alexander Holm; Mølmer, Klaus

2018-05-01

We show how an upper bound for the ability to discriminate any number N of candidates for the Hamiltonian governing the evolution of an open quantum system may be calculated by numerically efficient means. Our method applies an effective master-equation analysis to evaluate the pairwise overlaps between candidate full states of the system and its environment pertaining to the Hamiltonians. These overlaps are then used to construct an N -dimensional representation of the states. The optimal positive-operator valued measure (POVM) and the corresponding probability of assigning a false hypothesis may subsequently be evaluated by phrasing optimal discrimination of multiple nonorthogonal quantum states as a semidefinite programming problem. We provide three realistic examples of multihypothesis testing with open quantum systems.

Quantum turing machine and brain model represented by Fock space

NASA Astrophysics Data System (ADS)

Iriyama, Satoshi; Ohya, Masanori

2016-05-01

The adaptive dynamics is known as a new mathematics to treat with a complex phenomena, for example, chaos, quantum algorithm and psychological phenomena. In this paper, we briefly review the notion of the adaptive dynamics, and explain the definition of the generalized Turing machine (GTM) and recognition process represented by the Fock space. Moreover, we show that there exists the quantum channel which is described by the GKSL master equation to achieve the Chaos Amplifier used in [M. Ohya and I. V. Volovich, J. Opt. B 5(6) (2003) 639., M. Ohya and I. V. Volovich, Rep. Math. Phys. 52(1) (2003) 25.

Explanation of the quantum phenomenon of off-resonant cavity-mode emission

NASA Astrophysics Data System (ADS)

Echeverri-Arteaga, Santiago; Vinck-Posada, Herbert; Gómez, Edgar A.

2018-04-01

We theoretically investigate the unexpected occurrence of an extra emission peak that has been experimentally observed in off-resonant studies of cavity QED systems. Our results within the Markovian master equation approach successfully explain why the central peak arises, and how it reveals that the system is suffering a dynamical phase transition induced by the phonon-mediated coupling. Our findings are in qualitative agreement with previous reported experimental results, and the fundamental physics behind this quantum phenomenon is understood.

Continuous quantum measurement in spin environments

NASA Astrophysics Data System (ADS)

Xie, Dong; Wang, An Min

2015-08-01

We derive a stochastic master equation (SME) which describes the decoherence dynamics of a system in spin environments conditioned on the measurement record. Markovian and non-Markovian nature of environment can be revealed by a spectroscopy method based on weak continuous quantum measurement. On account of that correlated environments can lead to a non-local open system which exhibits strong non-Markovian effects although the local dynamics are Markovian, the spectroscopy method can be used to demonstrate that there is correlation between two environments.

Modular operads and the quantum open-closed homotopy algebra

NASA Astrophysics Data System (ADS)

Doubek, Martin; Jurčo, Branislav; Münster, Korbinian

2015-12-01

We verify that certain algebras appearing in string field theory are algebras over Feynman transform of modular operads which we describe explicitly. Equivalent description in terms of solutions of generalized BV master equations are explained from the operadic point of view.

High power diode laser Master Oscillator-Power Amplifier (MOPA)

NASA Technical Reports Server (NTRS)

Andrews, John R.; Mouroulis, P.; Wicks, G.

1994-01-01

High power multiple quantum well AlGaAs diode laser master oscillator - power amplifier (MOPA) systems were examined both experimentally and theoretically. For two pass operation, it was found that powers in excess of 0.3 W per 100 micrometers of facet length were achievable while maintaining diffraction-limited beam quality. Internal electrical-to-optical conversion efficiencies as high as 25 percent were observed at an internal amplifier gain of 9 dB. Theoretical modeling of multiple quantum well amplifiers was done using appropriate rate equations and a heuristic model of the carrier density dependent gain. The model gave a qualitative agreement with the experimental results. In addition, the model allowed exploration of a wider design space for the amplifiers. The model predicted that internal electrical-to-optical conversion efficiencies in excess of 50 percent should be achievable with careful system design. The model predicted that no global optimum design exists, but gain, efficiency, and optical confinement (coupling efficiency) can be mutually adjusted to meet a specific system requirement. A three quantum well, low optical confinement amplifier was fabricated using molecular beam epitaxial growth. Coherent beam combining of two high power amplifiers injected from a common master oscillator was also examined. Coherent beam combining with an efficiency of 93 percent resulted in a single beam having diffraction-limited characteristics. This beam combining efficiency is a world record result for such a system. Interferometric observations of the output of the amplifier indicated that spatial mode matching was a significant factor in the less than perfect beam combining. Finally, the system issues of arrays of amplifiers in a coherent beam combining system were investigated. Based upon experimentally observed parameters coherent beam combining could result in a megawatt-scale coherent beam with a 10 percent electrical-to-optical conversion efficiency.

Open quantum systems, effective Hamiltonians, and device characterization

NASA Astrophysics Data System (ADS)

Duffus, S. N. A.; Dwyer, V. M.; Everitt, M. J.

2017-10-01

High fidelity models, which are able to both support accurate device characterization and correctly account for environmental effects, are crucial to the engineering of scalable quantum technologies. As it ensures positivity of the density matrix, one preferred model of open systems describes the dynamics with a master equation in Lindblad form. In practice, Linblad operators are rarely derived from first principles, and often a particular form of annihilator is assumed. This results in dynamical models that miss those additional terms which must generally be added for the master equation to assume the Lindblad form, together with the other concomitant terms that must be assimilated into an effective Hamiltonian to produce the correct free evolution. In first principles derivations, such additional terms are often canceled (or countered), frequently in a somewhat ad hoc manner, leading to a number of competing models. Whilst the implications of this paper are quite general, to illustrate the point we focus here on an example anharmonic system; specifically that of a superconducting quantum interference device (SQUID) coupled to an Ohmic bath. The resulting master equation implies that the environment has a significant impact on the system's energy; we discuss the prospect of keeping or canceling this impact and note that, for the SQUID, monitoring the magnetic susceptibility under control of the capacitive coupling strength and the externally applied flux results in experimentally measurable differences between a number of these models. In particular, one should be able to determine whether a squeezing term of the form X ̂P ̂+P ̂X ̂ should be present in the effective Hamiltonian or not. If model generation is not performed correctly, device characterization will be prone to systemic errors.

Develop of a quantum electromechanical hybrid system

NASA Astrophysics Data System (ADS)

Hao, Yu; Rouxinol, Francisco; Brito, Frederico; Caldeira, Amir; Irish, Elinor; Lahaye, Matthew

In this poster, we will show our results from measurements of a hybrid quantum system composed of a superconducting transmon qubit-coupled and ultra-high frequency nano-mechanical resonator, embedded in a superconducting cavity. The transmon is capacitively coupled to a 3.4GHz nanoresonator and a T-filter-biased high-Q transmission line cavity. Single-tone and two-tone transmission spectroscopy measurements are used to probe the interactions between the cavity, qubit and mechanical resonator. These measurements are in good agreement with numerical simulations based upon a master equation for the tripartite system including dissipation. The results indicate that this system may be developed to serve as a platform for more advanced measurements with nanoresonators, including quantum state measurement, the exploration of nanoresonator quantum noise, and reservoir engineering.

Deriving Lindblad master equations with Keldysh diagrams: Correlated gain and loss in higher order perturbation theory

NASA Astrophysics Data System (ADS)

Müller, Clemens; Stace, Thomas M.

2017-01-01

Motivated by correlated decay processes producing gain, loss, and lasing in driven semiconductor quantum dots [Phys. Rev. Lett. 113, 036801 (2014), 10.1103/PhysRevLett.113.036801; Science 347, 285 (2015), 10.1126/science.aaa2501; Phys. Rev. Lett. 114, 196802 (2015), 10.1103/PhysRevLett.114.196802], we develop a theoretical technique by using Keldysh diagrammatic perturbation theory to derive a Lindblad master equation that goes beyond the usual second-order perturbation theory. We demonstrate the method on the driven dissipative Rabi model, including terms up to fourth order in the interaction between the qubit and both the resonator and environment. This results in a large class of Lindblad dissipators and associated rates which go beyond the terms that have previously been proposed to describe similar systems. All of the additional terms contribute to the system behavior at the same order of perturbation theory. We then apply these results to analyze the phonon-assisted steady-state gain of a microwave field driving a double quantum dot in a resonator. We show that resonator gain and loss are substantially affected by dephasing-assisted dissipative processes in the quantum-dot system. These additional processes, which go beyond recently proposed polaronic theories, are in good quantitative agreement with experimental observations.

Natural approach to quantum dissipation

NASA Astrophysics Data System (ADS)

Taj, David; Öttinger, Hans Christian

2015-12-01

The dissipative dynamics of a quantum system weakly coupled to one or several reservoirs is usually described in terms of a Lindblad generator. The popularity of this approach is certainly due to the linear character of the latter. However, while such linearity finds justification from an underlying Hamiltonian evolution in some scaling limit, it does not rely on solid physical motivations at small but finite values of the coupling constants, where the generator is typically used for applications. The Markovian quantum master equations we propose are instead supported by very natural thermodynamic arguments. They themselves arise from Markovian master equations for the system and the environment which preserve factorized states and mean energy and generate entropy at a non-negative rate. The dissipative structure is driven by an entropic map, called modular, which introduces nonlinearity. The generated modular dynamical semigroup (MDS) guarantees for the positivity of the time evolved state the correct steady state properties, the positivity of the entropy production, and a positive Onsager matrix with symmetry relations arising from Green-Kubo formulas. We show that the celebrated Davies Lindblad generator, obtained through the Born and the secular approximations, generates a MDS. In doing so we also provide a nonlinear MDS which is supported by a weak coupling argument and is free from the limitations of the Davies generator.

Excess Entropy Production in Quantum System: Quantum Master Equation Approach

NASA Astrophysics Data System (ADS)

Nakajima, Satoshi; Tokura, Yasuhiro

2017-12-01

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 propose to 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 entropy production is given by a line integral in the control parameter space and its integrand is called the Berry-Sinitsyn-Nemenman (BSN) vector. In the weakly nonequilibrium regime, we show that BSN vector is described by ln \\breve{ρ }_0 and ρ _0 where ρ _0 is the instantaneous steady state of the QME and \\breve{ρ }_0 is that of the QME which is given by reversing the sign of the Lamb shift term. If the system Hamiltonian is non-degenerate or the Lamb shift term is negligible, the excess entropy production approximately reduces to the difference between the von Neumann entropies of the system. Additionally, we point out that the expression of the entropy production obtained in the classical Markov jump process is different from our result and show that these are approximately equivalent only in the weakly nonequilibrium regime.

Many-body effects in transport through a quantum-dot cavity system

NASA Astrophysics Data System (ADS)

Dinu, I. V.; Moldoveanu, V.; Gartner, P.

2018-05-01

We theoretically describe electric transport through an optically active quantum dot embedded in a single-mode cavity, and coupled to source-drain particle reservoirs. The populations of various many-body configurations (e.g., excitons, trions, biexciton) and the photon-number occupancies are calculated from a master equation which is derived in the basis of dressed states. These take into account both the Coulomb and the light-matter interaction. The former is essential in the description of the transport, while for the latter we identify situations in which it can be neglected in the expression of tunneling rates. The fermionic nature of the particle reservoirs plays an important role in the argument. The master equation is numerically solved for the s -shell many-body configurations of disk-shaped quantum dots. If the cavity is tuned to the biexciton-exciton transition, the most efficient optical processes take place in a three-level Λ system. The alternative exciton-ground-state route is inhibited as nonresonant due to the biexciton binding energy. The steady-state current is analyzed as a function of the photon frequency and the coupling to the leads. An unexpected feature appears in its dependence on the cavity loss rate, which turns out to be nonmonotonic.

Geometry dependent suppression of collective quantum jumps in Rydberg atoms

NASA Astrophysics Data System (ADS)

Lees, Eitan; Clemens, James

2015-05-01

We consider N driven, damped Rydberg atoms in different spatial arrangements. Treating the atoms as two-level systems we model the coupling to the environment via the Lehmberg-Agarwal master equation which interpolates between fully independent and fully collective spontaneous emission depending on the specific locations of the atoms. We also include a collective dipole-dipole energy shift in the excited Rydberg state which leads to collective quantum jumps in the atomic excitation when the system is driven off resonance. We show that the quantum jumps are suppressed as the system makes a transition from independent to collective emission as the spacing of a linear array of atoms is decreased below the emission wavelength.

Electromagnetically induced transparency in a multilayered spherical quantum dot with hydrogenic impurity

NASA Astrophysics Data System (ADS)

Pavlović, Vladan; Šušnjar, Marko; Petrović, Katarina; Stevanović, Ljiljana

2018-04-01

In this paper the effects of size, hydrostatic pressure and temperature on electromagnetically induced transparency, as well as on absorption and the dispersion properties of multilayered spherical quantum dot with hydrogenic impurity are theoretically investigated. Energy eigenvalues and wavefunctions of quantum systems in three-level and four-level configurations are calculated using the shooting method, while optical properties are obtained using the density matrix formalism and master equations. It is shown that peaks of the optical properties experience a blue-shift with increasing hydrostatic pressure and red-shift with increasing temperature. The changes of optical properties as a consequence of changes in barrier wells widths are non-monotonic, and these changes are discussed in detail.

Overdamping by weakly coupled environments

NASA Astrophysics Data System (ADS)

Esposito, Massimiliano; Haake, Fritz

2005-12-01

A quantum system weakly interacting with a fast environment usually undergoes a relaxation with complex frequencies whose imaginary parts are damping rates quadratic in the coupling to the environment in accord with Fermi’s “golden rule.” We show for various models (spin damped by harmonic-oscillator or random-matrix baths, quantum diffusion, and quantum Brownian motion) that upon increasing the coupling up to a critical value still small enough to allow for weak-coupling Markovian master equations, a different relaxation regime can occur. In that regime, complex frequencies lose their real parts such that the process becomes overdamped. Our results call into question the standard belief that overdamping is exclusively a strong coupling feature.

Quantum heat engine with coupled superconducting resonators

NASA Astrophysics Data System (ADS)

Hardal, Ali Ü. C.; Aslan, Nur; Wilson, C. M.; Müstecaplıoǧlu, Özgür E.

2017-12-01

We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.

Quantum heat engine with coupled superconducting resonators.

PubMed

Hardal, Ali Ü C; Aslan, Nur; Wilson, C M; Müstecaplıoğlu, Özgür E

2017-12-01

We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.

Quantum Dynamics in Biological Systems

NASA Astrophysics Data System (ADS)

Shim, Sangwoo

In the first part of this dissertation, recent efforts to understand quantum mechanical effects in biological systems are discussed. Especially, long-lived quantum coherences observed during the electronic energy transfer process in the Fenna-Matthews-Olson complex at physiological condition are studied extensively using theories of open quantum systems. In addition to the usual master equation based approaches, the effect of the protein structure is investigated in atomistic detail through the combined application of quantum chemistry and molecular dynamics simulations. To evaluate the thermalized reduced density matrix, a path-integral Monte Carlo method with a novel importance sampling approach is developed for excitons coupled to an arbitrary phonon bath at a finite temperature. In the second part of the thesis, simulations of molecular systems and applications to vibrational spectra are discussed. First, the quantum dynamics of a molecule is simulated by combining semiclassical initial value representation and density funcitonal theory with analytic derivatives. A computationally-tractable approximation to the sum-of-states formalism of Raman spectra is subsequently discussed.

Fourier's law for quasi-one-dimensional chaotic quantum systems

NASA Astrophysics Data System (ADS)

Seligman, Thomas H.; Weidenmüller, Hans A.

2011-05-01

We derive Fourier's law for a completely coherent quasi-one-dimensional chaotic quantum system coupled locally to two heat baths at different temperatures. We solve the master equation to first order in the temperature difference. We show that the heat conductance can be expressed as a thermodynamic equilibrium coefficient taken at some intermediate temperature. We use that expression to show that for temperatures large compared to the mean level spacing of the system, the heat conductance is inversely proportional to the level density and, thus, inversely proportional to the length of the system.

Resonant Perturbation Theory of Decoherence and Relaxation of Quantum Bits

DOE PAGES

Merkli, M.; Berman, G. P.; Sigal, I. M.

2010-01-01

We describe our recenmore » t results on the resonant perturbation theory of decoherence and relaxation for quantum systems with many qubits. The approach represents a rigorous analysis of the phenomenon of decoherence and relaxation for general N -level systems coupled to reservoirs of bosonic fields. We derive a representation of the reduced dynamics valid for all times t ≥ 0 and for small but fixed interaction strength. Our approach does not involve master equation approximations and applies to a wide variety of systems which are not explicitly solvable.« less

Quantum localization of classical mechanics

NASA Astrophysics Data System (ADS)

Batalin, Igor A.; Lavrov, Peter M.

2016-07-01

Quantum localization of classical mechanics within the BRST-BFV and BV (or field-antifield) quantization methods are studied. It is shown that a special choice of gauge fixing functions (or BRST-BFV charge) together with the unitary limit leads to Hamiltonian localization in the path integral of the BRST-BFV formalism. In turn, we find that a special choice of gauge fixing functions being proportional to extremals of an initial non-degenerate classical action together with a very special solution of the classical master equation result in Lagrangian localization in the partition function of the BV formalism.

Protecting quantum Fisher information in curved space-time

NASA Astrophysics Data System (ADS)

Huang, Zhiming

2018-03-01

In this work, we investigate the quantum Fisher information (QFI) dynamics of a two-level atom interacting with quantized conformally coupled massless scalar fields in de Sitter-invariant vacuum. We first derive the master equation that governs its evolution. It is found that the QFI decays with evolution time. Furthermore, we propose two schemes to protect QFI by employing prior weak measurement (WM) and post measurement reversal (MR). We find that the first scheme can not always protect QFI and the second scheme has prominent advantage over the first scheme.

Non-Markovian dynamics in chiral quantum networks with spins and photons

NASA Astrophysics Data System (ADS)

Ramos, Tomás; Vermersch, Benoît; Hauke, Philipp; Pichler, Hannes; Zoller, Peter

2016-06-01

We study the dynamics of chiral quantum networks consisting of nodes coupled by unidirectional or asymmetric bidirectional quantum channels. In contrast to familiar photonic networks where driven two-level atoms exchange photons via 1D photonic nanostructures, we propose and study a setup where interactions between the atoms are mediated by spin excitations (magnons) in 1D X X spin chains representing spin waveguides. While Markovian quantum network theory eliminates quantum channels as structureless reservoirs in a Born-Markov approximation to obtain a master equation for the nodes, we are interested in non-Markovian dynamics. This arises from the nonlinear character of the dispersion with band-edge effects, and from finite spin propagation velocities leading to time delays in interactions. To account for the non-Markovian dynamics we treat the quantum degrees of freedom of the nodes and connecting channel as a composite spin system with the surrounding of the quantum network as a Markovian bath, allowing for an efficient solution with time-dependent density matrix renormalization-group techniques. We illustrate our approach showing non-Markovian effects in the driven-dissipative formation of quantum dimers, and we present examples for quantum information protocols involving quantum state transfer with engineered elements as basic building blocks of quantum spintronic circuits.

Uniqueness Of docosahexaenoic acid: A master Of DNA and A Quantum gate

USDA-ARS?s Scientific Manuscript database

The fossil record displays the sudden appearance of intracellular detail and the 32 phyla in what is known as the “Cambrian Explosion” at about 600 million years ago. The intracellular structures were made with membrane lipids which provided for organisation and specialisation. Oxidative metabolism...

High-Density Quantum Sensing with Dissipative First Order Transitions

NASA Astrophysics Data System (ADS)

Raghunandan, Meghana; Wrachtrup, Jörg; Weimer, Hendrik

2018-04-01

The sensing of external fields using quantum systems is a prime example of an emergent quantum technology. Generically, the sensitivity of a quantum sensor consisting of N independent particles is proportional to √{N }. However, interactions invariably occurring at high densities lead to a breakdown of the assumption of independence between the particles, posing a severe challenge for quantum sensors operating at the nanoscale. Here, we show that interactions in quantum sensors can be transformed from a nuisance into an advantage when strong interactions trigger a dissipative phase transition in an open quantum system. We demonstrate this behavior by analyzing dissipative quantum sensors based upon nitrogen-vacancy defect centers in diamond. Using both a variational method and a numerical simulation of the master equation describing the open quantum many-body system, we establish the existence of a dissipative first order transition that can be used for quantum sensing. We investigate the properties of this phase transition for two- and three-dimensional setups, demonstrating that the transition can be observed using current experimental technology. Finally, we show that quantum sensors based on dissipative phase transitions are particularly robust against imperfections such as disorder or decoherence, with the sensitivity of the sensor not being limited by the T2 coherence time of the device. Our results can readily be applied to other applications in quantum sensing and quantum metrology where interactions are currently a limiting factor.

High-Density Quantum Sensing with Dissipative First Order Transitions.

PubMed

Raghunandan, Meghana; Wrachtrup, Jörg; Weimer, Hendrik

2018-04-13

The sensing of external fields using quantum systems is a prime example of an emergent quantum technology. Generically, the sensitivity of a quantum sensor consisting of N independent particles is proportional to sqrt[N]. However, interactions invariably occurring at high densities lead to a breakdown of the assumption of independence between the particles, posing a severe challenge for quantum sensors operating at the nanoscale. Here, we show that interactions in quantum sensors can be transformed from a nuisance into an advantage when strong interactions trigger a dissipative phase transition in an open quantum system. We demonstrate this behavior by analyzing dissipative quantum sensors based upon nitrogen-vacancy defect centers in diamond. Using both a variational method and a numerical simulation of the master equation describing the open quantum many-body system, we establish the existence of a dissipative first order transition that can be used for quantum sensing. We investigate the properties of this phase transition for two- and three-dimensional setups, demonstrating that the transition can be observed using current experimental technology. Finally, we show that quantum sensors based on dissipative phase transitions are particularly robust against imperfections such as disorder or decoherence, with the sensitivity of the sensor not being limited by the T_{2} coherence time of the device. Our results can readily be applied to other applications in quantum sensing and quantum metrology where interactions are currently a limiting factor.

Canonical form of master equations and characterization of non-Markovianity

NASA Astrophysics Data System (ADS)

Hall, Michael J. W.; Cresser, James D.; Li, Li; Andersson, Erika

2014-04-01

Master equations govern the time evolution of a quantum system interacting with an environment, and may be written in a variety of forms. Time-independent or memoryless master equations, in particular, can be cast in the well-known Lindblad form. Any time-local master equation, Markovian or non-Markovian, may in fact also be written in a Lindblad-like form. A diagonalization procedure results in a unique, and in this sense canonical, representation of the equation, which may be used to fully characterize the non-Markovianity of the time evolution. Recently, several different measures of non-Markovianity have been presented which reflect, to varying degrees, the appearance of negative decoherence rates in the Lindblad-like form of the master equation. We therefore propose using the negative decoherence rates themselves, as they appear in the canonical form of the master equation, to completely characterize non-Markovianity. The advantages of this are especially apparent when more than one decoherence channel is present. We show that a measure proposed by Rivas et al. [Phys. Rev. Lett. 105, 050403 (2010), 10.1103/PhysRevLett.105.050403] is a surprisingly simple function of the canonical decoherence rates, and give an example of a master equation that is non-Markovian for all times t >0, but to which nearly all proposed measures are blind. We also give necessary and sufficient conditions for trace distance and volume measures to witness non-Markovianity, in terms of the Bloch damping matrix.

Dissipation-based entanglement via quantum Zeno dynamics and Rydberg antiblockade

NASA Astrophysics Data System (ADS)

Shao, X. Q.; Wu, J. H.; Yi, X. X.

2017-06-01

A scheme is proposed for dissipative generation of maximally entanglement between two Rydberg atoms in the context of cavity QED. The spontaneous emission of atoms combined with quantum Zeno dynamics and the Rydberg antiblockade guarantees a unique steady solution of the master equation of the system, which just corresponds to the antisymmetric Bell state |S > . The convergence rate can be accelerated by the ground-state blockade mechanism of Rydberg atoms. Meanwhile the effect of cavity decay is suppressed by the Zeno requirement, leading to a steady-state fidelity about 90 % as the single-atom cooperativity parameter C ≡g2/(κ γ ) =10 , and this restriction is further relaxed to C =5.2 once the quantum-jump-based feedback control is exploited.

Two-Photon Rabi Splitting in a Coupled System of a Nanocavity and Exciton Complexes.

PubMed

Qian, Chenjiang; Wu, Shiyao; Song, Feilong; Peng, Kai; Xie, Xin; Yang, Jingnan; Xiao, Shan; Steer, Matthew J; Thayne, Iain G; Tang, Chengchun; Zuo, Zhanchun; Jin, Kuijuan; Gu, Changzhi; Xu, Xiulai

2018-05-25

Two-photon Rabi splitting in a cavity-dot system provides a basis for multiqubit coherent control in a quantum photonic network. Here we report on two-photon Rabi splitting in a strongly coupled cavity-dot system. The quantum dot was grown intentionally large in size for a large oscillation strength and small biexciton binding energy. Both exciton and biexciton transitions couple to a high-quality-factor photonic crystal cavity with large coupling strengths over 130  μeV. Furthermore, the small binding energy enables the cavity to simultaneously couple with two exciton states. Thereby, two-photon Rabi splitting between the biexciton and cavity is achieved, which can be well reproduced by theoretical calculations with quantum master equations.

Two-Photon Rabi Splitting in a Coupled System of a Nanocavity and Exciton Complexes

NASA Astrophysics Data System (ADS)

Qian, Chenjiang; Wu, Shiyao; Song, Feilong; Peng, Kai; Xie, Xin; Yang, Jingnan; Xiao, Shan; Steer, Matthew J.; Thayne, Iain G.; Tang, Chengchun; Zuo, Zhanchun; Jin, Kuijuan; Gu, Changzhi; Xu, Xiulai

2018-05-01

Two-photon Rabi splitting in a cavity-dot system provides a basis for multiqubit coherent control in a quantum photonic network. Here we report on two-photon Rabi splitting in a strongly coupled cavity-dot system. The quantum dot was grown intentionally large in size for a large oscillation strength and small biexciton binding energy. Both exciton and biexciton transitions couple to a high-quality-factor photonic crystal cavity with large coupling strengths over 130 μ eV . Furthermore, the small binding energy enables the cavity to simultaneously couple with two exciton states. Thereby, two-photon Rabi splitting between the biexciton and cavity is achieved, which can be well reproduced by theoretical calculations with quantum master equations.

Distribution of tunnelling times for quantum electron transport.

PubMed

Rudge, Samuel L; Kosov, Daniel S

2016-03-28

In electron transport, the tunnelling time is the time taken for an electron to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for electron transport through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an electron jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.

Quantum teleportation through noisy channels with multi-qubit GHZ states

NASA Astrophysics Data System (ADS)

Espoukeh, Pakhshan; Pedram, Pouria

2014-08-01

We investigate two-party quantum teleportation through noisy channels for multi-qubit Greenberger-Horne-Zeilinger (GHZ) states and find which state loses less quantum information in the process. The dynamics of states is described by the master equation with the noisy channels that lead to the quantum channels to be mixed states. We analytically solve the Lindblad equation for -qubit GHZ states where Lindblad operators correspond to the Pauli matrices and describe the decoherence of states. Using the average fidelity, we show that 3GHZ state is more robust than GHZ state under most noisy channels. However, GHZ state preserves same quantum information with respect to Einstein-Podolsky-Rosen and 3GHZ states where the noise is in direction in which the fidelity remains unchanged. We explicitly show that Jung et al.'s conjecture (Phys Rev A 78:012312, 2008), namely "average fidelity with same-axis noisy channels is in general larger than average fidelity with different-axes noisy channels," is not valid for 3GHZ and 4GHZ states.

Performance of Continuous Quantum Thermal Devices Indirectly Connected to Environments

NASA Astrophysics Data System (ADS)

González, J.; Alonso, Daniel; Palao, José

2016-04-01

A general quantum thermodynamics network is composed of thermal devices connected to the environments through quantum wires. The coupling between the devices and the wires may introduce additional decay channels which modify the system performance with respect to the directly-coupled device. We analyze this effect in a quantum three-level device connected to a heat bath or to a work source through a two-level wire. The steady state heat currents are decomposed into the contributions of the set of simple circuits in the graph representing the master equation. Each circuit is associated with a mechanism in the device operation and the system performance can be described by a small number of circuit representatives of those mechanisms. Although in the limit of weak coupling between the device and the wire the new irreversible contributions can become small, they prevent the system from reaching the Carnot efficiency.

Super-Group Field Cosmology in Batalin-Vilkovisky Formulation

NASA Astrophysics Data System (ADS)

Upadhyay, Sudhaker

2016-09-01

In this paper we study the third quantized super-group field cosmology, a model in multiverse scenario, in Batalin-Vilkovisky (BV) formulation. Further, we propose the superfield/super-antifield dependent BRST symmetry transformations. Within this formulation we establish connection between the two different solutions of the quantum master equation within the BV formulation.

Cavity-coupled double-quantum dot at finite bias: Analogy with lasers and beyond

NASA Astrophysics Data System (ADS)

Kulkarni, Manas; Cotlet, Ovidiu; Türeci, Hakan E.

2014-09-01

We present a theoretical and experimental study of photonic and electronic transport properties of a voltage biased InAs semiconductor double quantum dot (DQD) that is dipole coupled to a superconducting transmission line resonator. We obtain the master equation for the reduced density matrix of the coupled system of cavity photons and DQD electrons accounting systematically for both the presence of phonons and the effect of leads at finite voltage bias. We subsequently derive analytical expressions for transmission, phase response, photon number, and the nonequilibrium steady-state electron current. We show that the coupled system under finite bias realizes an unconventional version of a single-atom laser and analyze the spectrum and the statistics of the photon flux leaving the cavity. In the transmission mode, the system behaves as a saturable single-atom amplifier for the incoming photon flux. Finally, we show that the back action of the photon emission on the steady-state current can be substantial. Our analytical results are compared to exact master equation results establishing regimes of validity of various analytical models. We compare our findings to available experimental measurements.

Partially coherent electron transport in terahertz quantum cascade lasers based on a Markovian master equation for the density matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jonasson, O.; Karimi, F.; Knezevic, I.

2016-08-01

We derive a Markovian master equation for the single-electron density matrix, applicable to quantum cascade lasers (QCLs). The equation conserves the positivity of the density matrix, includes off-diagonal elements (coherences) as well as in-plane dynamics, and accounts for electron scattering with phonons and impurities. We use the model to simulate a terahertz-frequency QCL, and compare the results with both experiment and simulation via nonequilibrium Green's functions (NEGF). We obtain very good agreement with both experiment and NEGF when the QCL is biased for optimal lasing. For the considered device, we show that the magnitude of coherences can be a significantmore » fraction of the diagonal matrix elements, which demonstrates their importance when describing THz QCLs. We show that the in-plane energy distribution can deviate far from a heated Maxwellian distribution, which suggests that the assumption of thermalized subbands in simplified density-matrix models is inadequate. As a result, we also show that the current density and subband occupations relax towards their steady-state values on very different time scales.« less

Non-local correlations via Wigner-Yanase skew information in two SC-qubit having mutual interaction under phase decoherence

NASA Astrophysics Data System (ADS)

Mohamed, Abdel-Baset A.

2017-10-01

An analytical solution of the master equation that describes a superconducting cavity containing two coupled superconducting charge qubits is obtained. Quantum-mechanical correlations based on Wigner-Yanase skew information, as local quantum uncertainty and uncertainty-induced quantum non-locality, are compared to the concurrence under the effects of the phase decoherence. Local quantum uncertainty exhibits sudden changes during its time evolution and revival process. Sudden death and sudden birth occur only for entanglement, depending on the initial state of the two coupled charge qubits, while the correlations of skew information does not vanish. The quantum correlations of skew information are found to be sensitive to the dephasing rate, the photons number in the cavity, the interaction strength between the two qubits, and the qubit distribution angle of the initial state. With a proper initial state, the stationary correlation of the skew information has a non-zero stationary value for a long time interval under the phase decoherence, that it may be useful in quantum information and computation processes.

Interferometric modulation of quantum cascade interactions

NASA Astrophysics Data System (ADS)

Cusumano, Stefano; Mari, Andrea; Giovannetti, Vittorio

2018-05-01

We consider many-body quantum systems dissipatively coupled by a cascade network, i.e., a setup in which interactions are mediated by unidirectional environmental modes propagating through a linear optical interferometer. In particular we are interested in the possibility of inducing different effective interactions by properly engineering an external dissipative network of beam splitters and phase shifters. In this work we first derive the general structure of the master equation for a symmetric class of translation-invariant cascade networks. Then we show how, by tuning the parameters of the interferometer, one can exploit interference effects to tailor a large variety of many-body interactions.

Intensity noise properties of a compact laser device based on a miniaturized MOPA system for spectroscopic applications

NASA Astrophysics Data System (ADS)

Baumgärtner, S.; Juhl, S.; Opalevs, D.; Sahm, A.; Hofmann, J.; Leisching, P.; Paschke, K.

2018-02-01

We present a novel compact laser device based on a semiconductor master-oscillator power-amplifier (MOPA) emitting at 772 nm, suitable for quantum optic and spectroscopy. The optical performance of the laser device is characterized. For miniaturized lasers the thermal management is challenging, we therefore perform thermal simulations and measurements. The first demonstrator is emitting more than 3 W optical power with a linewidth below 2lMHz. Using this MOPA design also compact devices for quantum optics (e.g. rubidium atomic clock) and seed lasers for frequency conversion can be realized [1].

Fermi’s golden rule, the origin and breakdown of Markovian master equations, and the relationship between oscillator baths and the random matrix model

NASA Astrophysics Data System (ADS)

Santra, Siddhartha; Cruikshank, Benjamin; Balu, Radhakrishnan; Jacobs, Kurt

2017-10-01

Fermi’s golden rule applies to a situation in which a single quantum state \\vert \\psi> is coupled to a near-continuum. This ‘quasi-continuum coupling’ structure results in a rate equation for the population of \\vert \\psi> . Here we show that the coupling of a quantum system to the standard model of a thermal environment, a bath of harmonic oscillators, can be decomposed into a ‘cascade’ made up of the quasi-continuum coupling structures of Fermi’s golden rule. This clarifies the connection between the physics of the golden rule and that of a thermal bath, and provides a non-rigorous but physically intuitive derivation of the Markovian master equation directly from the former. The exact solution to the Hamiltonian of the golden rule, known as the Bixon-Jortner model, generalized for an asymmetric spectrum, provides a window on how the evolution induced by the bath deviates from the master equation as one moves outside the Markovian regime. Our analysis also reveals the relationship between the oscillator bath and the ‘random matrix model’ (RMT) of a thermal bath. We show that the cascade structure is the one essential difference between the two models, and the lack of it prevents the RMT from generating transition rates that are independent of the initial state of the system. We suggest that the cascade structure is one of the generic elements of thermalizing many-body systems.

Adiabatic evolution of decoherence-free subspaces and its shortcuts

NASA Astrophysics Data System (ADS)

Wu, S. L.; Huang, X. L.; Li, H.; Yi, X. X.

2017-10-01

The adiabatic theorem and shortcuts to adiabaticity for time-dependent open quantum systems are explored in this paper. Starting from the definition of dynamical stable decoherence-free subspace, we show that, under a compact adiabatic condition, the quantum state remains in the time-dependent decoherence-free subspace with an extremely high purity, even though the dynamics of the open quantum system may not be adiabatic. The adiabatic condition mentioned here in the adiabatic theorem for open systems is very similar to that for closed quantum systems, except that the operators required to change slowly are the Lindblad operators. We also show that the adiabatic evolution of decoherence-free subspaces depends on the existence of instantaneous decoherence-free subspaces, which requires that the Hamiltonian of open quantum systems be engineered according to the incoherent control protocol. In addition, shortcuts to adiabaticity for adiabatic decoherence-free subspaces are also presented based on the transitionless quantum driving method. Finally, we provide an example that consists of a two-level system coupled to a broadband squeezed vacuum field to show our theory. Our approach employs Markovian master equations and the theory can apply to finite-dimensional quantum open systems.

Exploring Quantum Dynamics of Continuous Measurement with a Superconducting Qubit

NASA Astrophysics Data System (ADS)

Jadbabaie, Arian; Forouzani, Neda; Tan, Dian; Murch, Kater

Weak measurements obtain partial information about a quantum state with minimal backaction. This enables state tracking without immediate collapse to eigenstates, of interest to both experimental and theoretical physics. State tomography and continuous weak measurements may be used to reconstruct the evolution of a single system, known as a quantum trajectory. We examine experimental trajectories of a two-level system at varied measurement strengths with constant unitary drive. Our analysis is applied to a transmon qubit dispersively coupled to a 3D microwave cavity in the circuit QED architecture. The weakly coupled cavity acts as pointer system for QND measurements in the qubit's energy basis. Our results indicate a marked difference in state purity between two approaches for trajectory reconstruction: the Bayesian and Stochastic Master Equation (SME) formalisms. Further, we observe the transition from diffusive to jump-like trajectories, state purity evolution, and a novel, tilted form of the Quantum Zeno effect. This work provides new insight into quantum behavior and prompts further comparison of SME and Bayesian formalisms to understand the nature of quantum systems. Our results are applicable to a variety of fields, from stochastic thermodynamics to quantum control.

Endoreversible quantum heat engines in the linear response regime.

PubMed

Wang, Honghui; He, Jizhou; Wang, Jianhui

2017-07-01

We analyze general models of quantum heat engines operating a cycle of two adiabatic and two isothermal processes. We use the quantum master equation for a system to describe heat transfer current during a thermodynamic process in contact with a heat reservoir, with no use of phenomenological thermal conduction. We apply the endoreversibility description to such engine models working in the linear response regime and derive expressions of the efficiency and the power. By analyzing the entropy production rate along a single cycle, we identify the thermodynamic flux and force that a linear relation connects. From maximizing the power output, we find that such heat engines satisfy the tight-coupling condition and the efficiency at maximum power agrees with the Curzon-Ahlborn efficiency known as the upper bound in the linear response regime.

Rare quantum metastable states in the strongly dispersive Jaynes-Cummings oscillator

NASA Astrophysics Data System (ADS)

Mavrogordatos, Th. K.; Barratt, F.; Asari, U.; Szafulski, P.; Ginossar, E.; Szymańska, M. H.

2018-03-01

We present evidence of metastable rare quantum-fluctuation switching for the driven dissipative Jaynes-Cummings oscillator coupled to a zero-temperature bath in the strongly dispersive regime. We show that single-atom complex amplitude bistability is accompanied by the appearance of a low-amplitude long-lived transient state, hereinafter called the "dark state", having a distribution with quasi-Poissonian statistics both for the coupled qubit and cavity mode. We find that the dark state is linked to a spontaneous flipping of the qubit state, detuning the cavity to a low-photon response. The appearance of the dark state is correlated with the participation of the two metastable states in the dispersive bistability, as evidenced by the solution of the master equation and single quantum trajectories.

Synchronization of an optomechanical system to an external drive

NASA Astrophysics Data System (ADS)

Amitai, Ehud; Lörch, Niels; Nunnenkamp, Andreas; Walter, Stefan; Bruder, Christoph

2017-05-01

Optomechanical systems driven by an effective blue-detuned laser can exhibit self-sustained oscillations of the mechanical oscillator. These self-oscillations are a prerequisite for the observation of synchronization. Here, we study the synchronization of the mechanical oscillations to an external reference drive. We study two cases of reference drives: (1) an additional laser applied to the optical cavity; (2) a mechanical drive applied directly to the mechanical oscillator. Starting from a master equation description, we derive a microscopic Adler equation for both cases, valid in the classical regime in which the quantum shot noise of the mechanical self-oscillator does not play a role. Furthermore, we numerically show that, in both cases, synchronization arises also in the quantum regime. The optomechanical system is therefore a good candidate for the study of quantum synchronization.

Non-Markovian quantum jumps in excitonic energy transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebentrost, Patrick; Chakraborty, Rupak; Aspuru-Guzik, Alan

2009-01-01

We utilize the novel non-Markovian quantum jump (NMQJ) approach to stochastically simulate exciton dynamics derived from a time-convolutionless master equation. For relevant parameters and time scales, the time-dependent, oscillatory decoherence rates can have negative regions, a signature of non-Markovian behavior and of the revival of coherences. This can lead to non-Markovian population beatings for a dimer system at room temperature. We show that strong exciton-phonon coupling to low frequency modes can considerably modify transport properties. We observe increased excitontransport, which can be seen as an extension of recent environment-assisted quantum transport concepts to the non-Markovian regime. Within the NMQJ method,more » the Fenna–Matthew–Olson protein is investigated as a prototype for larger photosynthetic complexes.« less

Theory of remote entanglement via quantum-limited phase-preserving amplification

NASA Astrophysics Data System (ADS)

Silveri, Matti; Zalys-Geller, Evan; Hatridge, Michael; Leghtas, Zaki; Devoret, Michel H.; Girvin, S. M.

2016-06-01

We show that a quantum-limited phase-preserving amplifier can act as a which-path information eraser when followed by heterodyne detection. This "beam splitter with gain" implements a continuous joint measurement on the signal sources. As an application, we propose heralded concurrent remote entanglement generation between two qubits coupled dispersively to separate cavities. Dissimilar qubit-cavity pairs can be made indistinguishable by simple engineering of the cavity driving fields providing further experimental flexibility and the prospect for scalability. Additionally, we find an analytic solution for the stochastic master equation, a quantum filter, yielding a thorough physical understanding of the nonlinear measurement process leading to an entangled state of the qubits. We determine the concurrence of the entangled states and analyze its dependence on losses and measurement inefficiencies.

Protected Quantum Computation with Multiple Resonators in Ultrastrong Coupling Circuit QED

NASA Astrophysics Data System (ADS)

Nataf, Pierre; Ciuti, Cristiano

2011-11-01

We investigate theoretically the dynamical behavior of a qubit obtained with the two ground eigenstates of an ultrastrong coupling circuit-QED system consisting of a finite number of Josephson fluxonium atoms inductively coupled to a transmission line resonator. We show a universal set of quantum gates by using multiple transmission line resonators (each resonator represents a single qubit). We discuss the intrinsic “anisotropic” nature of noise sources for fluxonium artificial atoms. Through a master equation treatment with colored noise and many-level dynamics, we prove that, for a general class of anisotropic noise sources, the coherence time of the qubit and the fidelity of the quantum operations can be dramatically improved in an optimal regime of ultrastrong coupling, where the ground state is an entangled photonic “cat” state.

Analytic integration of real-virtual counterterms in NNLO jet cross sections I

NASA Astrophysics Data System (ADS)

Aglietti, Ugo; Del Duca, Vittorio; Duhr, Claude; Somogyi, Gábor; Trócsányi, Zoltán

2008-09-01

We present analytic evaluations of some integrals needed to give explicitly the integrated real-virtual counterterms, based on a recently proposed subtraction scheme for next-to-next-to-leading order (NNLO) jet cross sections. After an algebraic reduction of the integrals, integration-by-parts identities are used for the reduction to master integrals and for the computation of the master integrals themselves by means of differential equations. The results are written in terms of one- and two-dimensional harmonic polylogarithms, once an extension of the standard basis is made. We expect that the techniques described here will be useful in computing other integrals emerging in calculations in perturbative quantum field theories.

Antimatter

NASA Astrophysics Data System (ADS)

Fraser, Gordon

2002-03-01

1. Science fiction becomes science fact; 2. Mirror worlds; 3. An imbalanced kit of electrical parts; 4. The quantum master; 5. Positive proof; 6. The back passage of time; 7. The quark and the antiquark; 8. Broken mirrors; 9. The cosmic corkscrew; 10. Antiparticle collision course; 11. Setting a trap for antimatter; 12. Glue versus antichemistry; 13. Antimatter in action; 14. Antimatter of the utmost gravity.

Coherence enhanced quantum metrology in a nonequilibrium optical molecule

NASA Astrophysics Data System (ADS)

Wang, Zhihai; Wu, Wei; Cui, Guodong; Wang, Jin

2018-03-01

We explore the quantum metrology in an optical molecular system coupled to two environments with different temperatures, using a quantum master equation beyond secular approximation. We discover that the steady-state coherence originating from and sustained by the nonequilibrium condition can enhance quantum metrology. We also study the quantitative measures of the nonequilibrium condition in terms of the curl flux, heat current and entropy production at the steady state. They are found to grow with temperature difference. However, an apparent paradox arises considering the contrary behaviors of the steady-state coherence and the nonequilibrium measures in relation to the inter-cavity coupling strength. This paradox is resolved by decomposing the heat current into a population part and a coherence part. Only the latter, the coherence part of the heat current, is tightly connected to the steady-state coherence and behaves similarly with respect to the inter-cavity coupling strength. Interestingly, the coherence part of the heat current flows from the low-temperature reservoir to the high-temperature reservoir, opposite to the direction of the population heat current. Our work offers a viable way to enhance quantum metrology for open quantum systems through steady-state coherence sustained by the nonequilibrium condition, which can be controlled and manipulated to maximize its utility. The potential applications go beyond quantum metrology and extend to areas such as device designing, quantum computation and quantum technology in general.

Exact calculation of the time convolutionless master equation generator: Application to the nonequilibrium resonant level model

NASA Astrophysics Data System (ADS)

Kidon, Lyran; Wilner, Eli Y.; Rabani, Eran

2015-12-01

The generalized quantum master equation provides a powerful tool to describe the dynamics in quantum impurity models driven away from equilibrium. Two complementary approaches, one based on Nakajima-Zwanzig-Mori time-convolution (TC) and the other on the Tokuyama-Mori time-convolutionless (TCL) formulations provide a starting point to describe the time-evolution of the reduced density matrix. A key in both approaches is to obtain the so called "memory kernel" or "generator," going beyond second or fourth order perturbation techniques. While numerically converged techniques are available for the TC memory kernel, the canonical approach to obtain the TCL generator is based on inverting a super-operator in the full Hilbert space, which is difficult to perform and thus, nearly all applications of the TCL approach rely on a perturbative scheme of some sort. Here, the TCL generator is expressed using a reduced system propagator which can be obtained from system observables alone and requires the calculation of super-operators and their inverse in the reduced Hilbert space rather than the full one. This makes the formulation amenable to quantum impurity solvers or to diagrammatic techniques, such as the nonequilibrium Green's function. We implement the TCL approach for the resonant level model driven away from equilibrium and compare the time scales for the decay of the generator with that of the memory kernel in the TC approach. Furthermore, the effects of temperature, source-drain bias, and gate potential on the TCL/TC generators are discussed.

Wigner distribution function and entropy of the damped harmonic oscillator within the theory of the open quantum systems

NASA Technical Reports Server (NTRS)

Isar, Aurelian

1995-01-01

The harmonic oscillator with dissipation is studied within the framework of the Lindblad theory for open quantum systems. By using the Wang-Uhlenbeck method, the Fokker-Planck equation, obtained from the master equation for the density operator, is solved for the Wigner distribution function, subject to either the Gaussian type or the delta-function type of initial conditions. The obtained Wigner functions are two-dimensional Gaussians with different widths. Then a closed expression for the density operator is extracted. The entropy of the system is subsequently calculated and its temporal behavior shows that this quantity relaxes to its equilibrium value.

Correlated sequential tunneling in Tomonaga-Luttinger liquid quantum dots

NASA Astrophysics Data System (ADS)

Thorwart, M.; Egger, R.; Grifoni, M.

2005-02-01

We investigate tunneling through a quantum dot formed by two strong impurites in a spinless Tomonaga-Luttinger liquid. Upon employing a Markovian master equation approach, we compute the linear conductance due to sequential tunneling processes. Besides the previously used lowest-order Golden Rule rates describing uncorrelated sequential tunneling (UST) processes, we systematically include higher-order correlated sequential tunneling (CST) diagrams within the standard Weisskopf-Wigner approximation. We provide estimates for the parameter regions where CST effects are shown to dominate over UST. Focusing mainly on the temperature dependence of the conductance maximum, we discuss the relation of our results to previous theoretical and experimental results.

Theories of Matter, Space and Time, Volume 2; Quantum theories

NASA Astrophysics Data System (ADS)

Evans, N.; King, S. F.

2018-06-01

This book and its prequel Theories of Matter Space and Time: Classical Theories grew out of courses that we have both taught as part of the undergraduate degree program in Physics at Southampton University, UK. Our goal was to guide the full MPhys undergraduate cohort through some of the trickier areas of theoretical physics that we expect our undergraduates to master. Here we teach the student to understand first quantized relativistic quantum theories. We first quickly review the basics of quantum mechanics which should be familiar to the reader from a prior course. Then we will link the Schrödinger equation to the principle of least action introducing Feynman's path integral methods. Next, we present the relativistic wave equations of Klein, Gordon and Dirac. Finally, we convert Maxwell's equations of electromagnetism to a wave equation for photons and make contact with quantum electrodynamics (QED) at a first quantized level. Between the two volumes we hope to move a student's understanding from their prior courses to a place where they are ready, beyond, to embark on graduate level courses on quantum field theory.

Steady state conductance in a double quantum dot array: the nonequilibrium equation-of-motion Green function approach.

PubMed

Levy, Tal J; Rabani, Eran

2013-04-28

We study steady state transport through a double quantum dot array using the equation-of-motion approach to the nonequilibrium Green functions formalism. This popular technique relies on uncontrolled approximations to obtain a closure for a hierarchy of equations; however, its accuracy is questioned. We focus on 4 different closures, 2 of which were previously proposed in the context of the single quantum dot system (Anderson impurity model) and were extended to the double quantum dot array, and develop 2 new closures. Results for the differential conductance are compared to those attained by a master equation approach known to be accurate for weak system-leads couplings and high temperatures. While all 4 closures provide an accurate description of the Coulomb blockade and other transport properties in the single quantum dot case, they differ in the case of the double quantum dot array, where only one of the developed closures provides satisfactory results. This is rationalized by comparing the poles of the Green functions to the exact many-particle energy differences for the isolate system. Our analysis provides means to extend the equation-of-motion technique to more elaborate models of large bridge systems with strong electronic interactions.

Deterministic generation of remote entanglement with active quantum feedback

DOE PAGES

Martin, Leigh; Motzoi, Felix; Li, Hanhan; ...

2015-12-10

We develop and study protocols for deterministic remote entanglement generation using quantum feedback, without relying on an entangling Hamiltonian. In order to formulate the most effective experimentally feasible protocol, we introduce the notion of average-sense locally optimal feedback protocols, which do not require real-time quantum state estimation, a difficult component of real-time quantum feedback control. We use this notion of optimality to construct two protocols that can deterministically create maximal entanglement: a semiclassical feedback protocol for low-efficiency measurements and a quantum feedback protocol for high-efficiency measurements. The latter reduces to direct feedback in the continuous-time limit, whose dynamics can bemore » modeled by a Wiseman-Milburn feedback master equation, which yields an analytic solution in the limit of unit measurement efficiency. Our formalism can smoothly interpolate between continuous-time and discrete-time descriptions of feedback dynamics and we exploit this feature to derive a superior hybrid protocol for arbitrary nonunit measurement efficiency that switches between quantum and semiclassical protocols. Lastly, we show using simulations incorporating experimental imperfections that deterministic entanglement of remote superconducting qubits may be achieved with current technology using the continuous-time feedback protocol alone.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Zehua, E-mail: zehuatian@126.com; Wang, Jieci; Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081

We show how the use of entanglement can enhance the precision of the detection of the Unruh effect with an accelerated probe. We use a two-level atom interacting relativistically with a quantum field as the probe, and treat it as an open quantum system to derive the master equation governing its evolution. By means of quantum state discrimination, we detect the accelerated motion of the atom by examining its time evolving state. It turns out that the optimal strategy for the detection of the Unruh effect, to which the accelerated atom is sensitive, involves letting the atom-thermometer equilibrate with themore » thermal bath. However, introducing initial entanglement between the detector and an external degree of freedom leads to an enhancement of the sensitivity of the detector. Also, the maximum precision is attained within finite time, before equilibration takes place.« less

Quantum critical probing and simulation of colored quantum noise

NASA Astrophysics Data System (ADS)

Mascarenhas, Eduardo; de Vega, Inés

2017-12-01

We propose a protocol to simulate the evolution of a non-Markovian open quantum system by considering a collisional process with a many-body system, which plays the role of an environment. As a result of our protocol, the environment spatial correlations are mapped into the time correlations of a noise that drives the dynamics of the open system. Considering the weak coupling limit, the open system can also be considered as a probe of the environment properties. In this regard, when preparing the environment in its ground state, a measurement of the dynamics of the open system allows to determine the length of the environment spatial correlations and therefore its critical properties. To illustrate our proposal we simulate the full system dynamics with matrix-product-states and compare this to the reduced dynamics obtained with an approximated variational master equation.

Four-electron model for singlet and triplet excitation energy transfers with inclusion of coherence memory, inelastic tunneling and nuclear quantum effects

NASA Astrophysics Data System (ADS)

Suzuki, Yosuke; Ebina, Kuniyoshi; Tanaka, Shigenori

2016-08-01

A computational scheme to describe the coherent dynamics of excitation energy transfer (EET) in molecular systems is proposed on the basis of generalized master equations with memory kernels. This formalism takes into account those physical effects in electron-bath coupling system such as the spin symmetry of excitons, the inelastic electron tunneling and the quantum features of nuclear motions, thus providing a theoretical framework to perform an ab initio description of EET through molecular simulations for evaluating the spectral density and the temporal correlation function of electronic coupling. Some test calculations have then been carried out to investigate the dependence of exciton population dynamics on coherence memory, inelastic tunneling correlation time, magnitude of electronic coupling, quantum correction to temporal correlation function, reorganization energy and energy gap.

Optimal antibunching in passive photonic devices based on coupled nonlinear resonators

NASA Astrophysics Data System (ADS)

Ferretti, S.; Savona, V.; Gerace, D.

2013-02-01

We propose the use of weakly nonlinear passive materials for prospective applications in integrated quantum photonics. It is shown that strong enhancement of native optical nonlinearities by electromagnetic field confinement in photonic crystal resonators can lead to single-photon generation only exploiting the quantum interference of two coupled modes and the effect of photon blockade under resonant coherent driving. For realistic system parameters in state of the art microcavities, the efficiency of such a single-photon source is theoretically characterized by means of the second-order correlation function at zero-time delay as the main figure of merit, where major sources of loss and decoherence are taken into account within a standard master equation treatment. These results could stimulate the realization of integrated quantum photonic devices based on non-resonant material media, fully integrable with current semiconductor technology and matching the relevant telecom band operational wavelengths, as an alternative to single-photon nonlinear devices based on cavity quantum electrodynamics with artificial atoms or single atomic-like emitters.

Autonomous rotor heat engine

NASA Astrophysics Data System (ADS)

Roulet, Alexandre; Nimmrichter, Stefan; Arrazola, Juan Miguel; Seah, Stella; Scarani, Valerio

2017-06-01

The triumph of heat engines is their ability to convert the disordered energy of thermal sources into useful mechanical motion. In recent years, much effort has been devoted to generalizing thermodynamic notions to the quantum regime, partly motivated by the promise of surpassing classical heat engines. Here, we instead adopt a bottom-up approach: we propose a realistic autonomous heat engine that can serve as a test bed for quantum effects in the context of thermodynamics. Our model draws inspiration from actual piston engines and is built from closed-system Hamiltonians and weak bath coupling terms. We analytically derive the performance of the engine in the classical regime via a set of nonlinear Langevin equations. In the quantum case, we perform numerical simulations of the master equation. Finally, we perform a dynamic and thermodynamic analysis of the engine's behavior for several parameter regimes in both the classical and quantum case and find that the latter exhibits a consistently lower efficiency due to additional noise.

Two-color single-photon emission from InAs quantum dots: toward logic information management using quantum light.

PubMed

Rivas, David; Muñoz-Matutano, Guillermo; Canet-Ferrer, Josep; García-Calzada, Raúl; Trevisi, Giovanna; Seravalli, Luca; Frigeri, Paola; Martínez-Pastor, Juan P

2014-02-12

In this work, we propose the use of the Hanbury-Brown and Twiss interferometric technique and a switchable two-color excitation method for evaluating the exciton and noncorrelated electron-hole dynamics associated with single photon emission from indium arsenide (InAs) self-assembled quantum dots (QDs). Using a microstate master equation model we demonstrate that our single QDs are described by nonlinear exciton dynamics. The simultaneous detection of two-color, single photon emission from InAs QDs using these nonlinear dynamics was used to design a NOT AND logic transference function. This computational functionality combines the advantages of working with light/photons as input/output device parameters (all-optical system) and that of a nanodevice (QD size of ∼ 20 nm) while also providing high optical sensitivity (ultralow optical power operational requirements). These system features represent an important and interesting step toward the development of new prototypes for the incoming quantum information technologies.

Dynamics of quantum tomography in an open system

NASA Astrophysics Data System (ADS)

Uchiyama, Chikako

2015-06-01

In this study, we provide a way to describe the dynamics of quantum tomography in an open system with a generalized master equation, considering a case where the relevant system under tomographic measurement is influenced by the environment. We apply this to spin tomography because such situations typically occur in μSR (muon spin rotation/relaxation/resonance) experiments where microscopic features of the material are investigated by injecting muons as probes. As a typical example to describe the interaction between muons and a sample material, we use a spin-boson model where the relevant spin interacts with a bosonic environment. We describe the dynamics of a spin tomogram using a time-convolutionless type of generalized master equation that enables us to describe short time scales and/or low-temperature regions. Through numerical evaluation for the case of Ohmic spectral density with an exponential cutoff, a clear interdependency is found between the time evolution of elements of the density operator and a spin tomogram. The formulation in this paper may provide important fundamental information for the analysis of results from, for example, μSR experiments on short time scales and/or in low-temperature regions using spin tomography.

Dynamics of quantum correlation and coherence for two atoms coupled with a bath of fluctuating massless scalar field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhiming, E-mail: 465609785@qq.com; Situ, Haozhen, E-mail: situhaozhen@gmail.com

In this article, the dynamics of quantum correlation and coherence for two atoms interacting with a bath of fluctuating massless scalar field in the Minkowski vacuum is investigated. We firstly derive the master equation that describes the system evolution with initial Bell-diagonal state. Then we discuss the system evolution for three cases of different initial states: non-zero correlation separable state, maximally entangled state and zero correlation state. For non-zero correlation initial separable state, quantum correlation and coherence can be protected from vacuum fluctuations during long time evolution when the separation between the two atoms is relatively small. For maximally entangledmore » initial state, quantum correlation and coherence overall decrease with evolution time. However, for the zero correlation initial state, quantum correlation and coherence are firstly generated and then drop with evolution time; when separation is sufficiently small, they can survive from vacuum fluctuations. For three cases, quantum correlation and coherence first undergo decline and then fluctuate to relatively stable values with the increasing distance between the two atoms. Specially, for the case of zero correlation initial state, quantum correlation and coherence occur periodically revival at fixed zero points and revival amplitude declines gradually with increasing separation of two atoms.« less

Operation of a quantum dot in the finite-state machine mode: Single-electron dynamic memory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klymenko, M. V.; Klein, M.; Levine, R. D.

2016-07-14

A single electron dynamic memory is designed based on the non-equilibrium dynamics of charge states in electrostatically defined metallic quantum dots. Using the orthodox theory for computing the transfer rates and a master equation, we model the dynamical response of devices consisting of a charge sensor coupled to either a single and or a double quantum dot subjected to a pulsed gate voltage. We show that transition rates between charge states in metallic quantum dots are characterized by an asymmetry that can be controlled by the gate voltage. This effect is more pronounced when the switching between charge states correspondsmore » to a Markovian process involving electron transport through a chain of several quantum dots. By simulating the dynamics of electron transport we demonstrate that the quantum box operates as a finite-state machine that can be addressed by choosing suitable shapes and switching rates of the gate pulses. We further show that writing times in the ns range and retention memory times six orders of magnitude longer, in the ms range, can be achieved on the double quantum dot system using experimentally feasible parameters, thereby demonstrating that the device can operate as a dynamic single electron memory.« less

QuTiP 2: A Python framework for the dynamics of open quantum systems

NASA Astrophysics Data System (ADS)

Johansson, J. R.; Nation, P. D.; Nori, Franco

2013-04-01

We present version 2 of QuTiP, the Quantum Toolbox in Python. Compared to the preceding version [J.R. Johansson, P.D. Nation, F. Nori, Comput. Phys. Commun. 183 (2012) 1760.], we have introduced numerous new features, enhanced performance, and made changes in the Application Programming Interface (API) for improved functionality and consistency within the package, as well as increased compatibility with existing conventions used in other scientific software packages for Python. The most significant new features include efficient solvers for arbitrary time-dependent Hamiltonians and collapse operators, support for the Floquet formalism, and new solvers for Bloch-Redfield and Floquet-Markov master equations. Here we introduce these new features, demonstrate their use, and give a summary of the important backward-incompatible API changes introduced in this version. Catalog identifier: AEMB_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEMB_v2_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 33625 No. of bytes in distributed program, including test data, etc.: 410064 Distribution format: tar.gz Programming language: Python. Computer: i386, x86-64. Operating system: Linux, Mac OSX. RAM: 2+ Gigabytes Classification: 7. External routines: NumPy, SciPy, Matplotlib, Cython Catalog identifier of previous version: AEMB_v1_0 Journal reference of previous version: Comput. Phys. Comm. 183 (2012) 1760 Does the new version supercede the previous version?: Yes Nature of problem: Dynamics of open quantum systems Solution method: Numerical solutions to Lindblad, Floquet-Markov, and Bloch-Redfield master equations, as well as the Monte Carlo wave function method. Reasons for new version: Compared to the preceding version we have introduced numerous new features, enhanced performance, and made changes in the Application Programming Interface (API) for improved functionality and consistency within the package, as well as increased compatibility with existing conventions used in other scientific software packages for Python. The most significant new features include efficient solvers for arbitrary time-dependent Hamiltonians and collapse operators, support for the Floquet formalism, and new solvers for Bloch-Redfield and Floquet-Markov master equations. Restrictions: Problems must meet the criteria for using the master equation in Lindblad, Floquet-Markov, or Bloch-Redfield form. Running time: A few seconds up to several tens of hours, depending on size of the underlying Hilbert space.

Quantum Manybody Physics with Rydberg Polaritons

DTIC Science & Technology

2016-06-22

report, such as final, technical, interim, memorandum, master’s thesis, progress, quarterly, research , special, group study, etc. 3. DATES COVERED...for public release. Over the course of this grant, we have seen tremendous progress, both theoretically and experimentally , in our control of photonic...shown in multiple stages of construction at left and below, spans three optical tables in two rooms: One for the experimental control system

Rydberg blockade in three-atom systems

NASA Astrophysics Data System (ADS)

Barredo, Daniel; Ravets, Sylvain; Labuhn, Henning; Beguin, Lucas; Vernier, Aline; Chicireanu, Radu; Nogrette, Florence; Lahaye, Thierry; Browaeys, Antoine

2014-05-01

The control of individual neutral atoms in arrays of optical tweezers is a promising avenue for quantum science and technology. Here we demonstrate unprecedented control over a system of three Rydberg atoms arranged in linear and triangular configurations. The interaction between Rydberg atoms results in the observation of an almost perfect van der Waals blockade. When the single-atom Rabi frequency for excitation to the Rydberg state is comparable to the interaction energy, we directly observe the anisotropy of the interaction between nD-states. Using the independently measured two-body interaction energy shifts we fully reproduce the dynamics of the three-atom system with a model based on a master equation without any adjustable parameter. Combined with our ability to trap single atoms in arbitrary patterns of 2D arrays of up to 100 traps separated by a few microns, these results are very promising for a scalable implementation of quantum simulation of frustrated quantum magnetism with Rydberg atoms.

Temperature dependence of long coherence times of oxide charge qubits.

PubMed

Dey, A; Yarlagadda, S

2018-02-22

The ability to maintain coherence and control in a qubit is a major requirement for quantum computation. We show theoretically that long coherence times can be achieved at easily accessible temperatures (such as boiling point of liquid helium) in small (i.e., ~10 nanometers) charge qubits of oxide double quantum dots when only optical phonons are the source of decoherence. In the regime of strong electron-phonon coupling and in the non-adiabatic region, we employ a duality transformation to make the problem tractable and analyze the dynamics through a non-Markovian quantum master equation. We find that the system decoheres after a long time, despite the fact that no energy is exchanged with the bath. Detuning the dots to a fraction of the optical phonon energy, increasing the electron-phonon coupling, reducing the adiabaticity, or decreasing the temperature enhances the coherence time.

Key Reconciliation for High Performance Quantum Key Distribution

PubMed Central

Martinez-Mateo, Jesus; Elkouss, David; Martin, Vicente

2013-01-01

Quantum Key Distribution is carving its place among the tools used to secure communications. While a difficult technology, it enjoys benefits that set it apart from the rest, the most prominent is its provable security based on the laws of physics. QKD requires not only the mastering of signals at the quantum level, but also a classical processing to extract a secret-key from them. This postprocessing has been customarily studied in terms of the efficiency, a figure of merit that offers a biased view of the performance of real devices. Here we argue that it is the throughput the significant magnitude in practical QKD, specially in the case of high speed devices, where the differences are more marked, and give some examples contrasting the usual postprocessing schemes with new ones from modern coding theory. A good understanding of its implications is very important for the design of modern QKD devices. PMID:23546440

Understanding Hawking radiation in the framework of open quantum systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu Hongwei; Zhang Jialin

2008-01-15

We study the Hawking radiation in the framework of open quantum systems by examining the time evolution of a detector (modeled by a two-level atom) interacting with vacuum massless scalar fields. The dynamics of the detector is governed by a master equation obtained by tracing over the field degrees of freedom from the complete system. The nonunitary effects are studied by analyzing the time behavior of a particular observable of the detector, i.e., its admissible state, in the Unruh, Hartle-Hawking, as well as Boulware vacua outside a Schwarzschild black hole. We find that the detector in both the Unruh andmore » Hartle-Hawking vacua would spontaneously excite with a nonvanishing probability the same as what one would obtain if there is thermal radiation at the Hawking temperature from the black hole, thus reproducing the basic results concerning the Hawking effect in the framework of open quantum systems.« less

Onsets of hierarchy truncation and self–consistent Born approximation with quantum mechanics prescriptions invariance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hou-Dao; Yan, YiJing, E-mail: yyan@ust.hk; iChEM and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026

2015-12-07

The issue of efficient hierarchy truncation is related to many approximate theories. In this paper, we revisit this issue from both the numerical efficiency and quantum mechanics prescription invariance aspects. The latter requires that the truncation approximation made in Schrödinger picture, such as the quantum master equations and their self–consistent–Born–approximation improvements, should be transferable to their Heisenberg–picture correspondences, without further approximations. We address this issue with the dissipaton equation of motion (DEOM), which is a unique theory for the dynamics of not only reduced systems but also hybrid bath environments. We also highlight the DEOM theory is not only aboutmore » how its dynamical variables evolve in time, but also the underlying dissipaton algebra. We demonstrate this unique feature of DEOM with model systems and report some intriguing nonlinear Fano interferences characteristics that are experimentally measurable.« less

Microscopic theory of energy dissipation and decoherence in open systems: A quantum Fermi's golden rule

NASA Astrophysics Data System (ADS)

Taj, D.; Iotti, R. C.; Rossi, F.

2009-11-01

We shall revisit the conventional adiabatic or Markov approximation, which — contrary to the semiclassical case- does not preserve the positive-definite character of the corresponding density matrix, thus leading to highly non-physical results. To overcome this serious limitation, originally addressed by Davies and co-workers almost three decades ago, we shall propose an alternative more general adiabatic procedure, able to provide a reliable/robust treatment of energy-dissipation and dephasing processes in electronic quantum devices. Unlike standard master-equation formulations, our procedure guarantees a positive evolution for a variety of physical subsystem (including the common partial trace), and quantum scattering rates are well defined even for subsystems with internal structure/ continuous energy spectrum. We shall compare the proposed Markov dissipation model with the conventional one also through basic simulations of energy-relaxation versus decoherence channels in prototypical semiconductor nanodevices.

Dynamics of Entropy in Quantum-like Model of Decision Making

NASA Astrophysics Data System (ADS)

Basieva, Irina; Khrennikov, Andrei; Asano, Masanari; Ohya, Masanori; Tanaka, Yoshiharu

2011-03-01

We present a quantum-like model of decision making in games of the Prisoner's Dilemma type. By this model the brain processes information by using representation of mental states in complex Hilbert space. Driven by the master equation the mental state of a player, say Alice, approaches an equilibrium point in the space of density matrices. By using this equilibrium point Alice determines her mixed (i.e., probabilistic) strategy with respect to Bob. Thus our model is a model of thinking through decoherence of initially pure mental state. Decoherence is induced by interaction with memory and external environment. In this paper we study (numerically) dynamics of quantum entropy of Alice's state in the process of decision making. Our analysis demonstrates that this dynamics depends nontrivially on the initial state of Alice's mind on her own actions and her prediction state (for possible actions of Bob.)

The New Physics and Cosmology - Dialogues with the Dalai Lama

NASA Astrophysics Data System (ADS)

Zajonc, Arthur; Houshmand, Zara

2004-03-01

What happens when the Dalai Lama meets with leading physicists and a historian? This book is the carefully edited record of the fascinating discussions at a Mind and Life conference in which five leading physicists and a historian (David Finkelstein, George Greenstein, Piet Hut, Arthur Zajonc, Anton Zeilinger, and Tu Weiming) discussed with the Dalai Lama current thought in theoretical quantum physics, in the context of Buddhist philosophy. A contribution to the science-religion interface, and a useful explanation of our basic understanding of quantum reality, couched at a level that intelligent readers without a deep involvement in science can grasp. In the tradition of other popular books on resonances between modern quantum physics and Zen or Buddhist mystical traditions--notably The Dancing Wu Li Masters and The Tao of Physics , this book gives a clear and useful update of the genuine correspondences between these two rather disparate approaches to understanding the nature of reality.

Efficient steady-state solver for hierarchical quantum master equations

NASA Astrophysics Data System (ADS)

Zhang, Hou-Dao; Qiao, Qin; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing

2017-07-01

Steady states play pivotal roles in many equilibrium and non-equilibrium open system studies. Their accurate evaluations call for exact theories with rigorous treatment of system-bath interactions. Therein, the hierarchical equations-of-motion (HEOM) formalism is a nonperturbative and non-Markovian quantum dissipation theory, which can faithfully describe the dissipative dynamics and nonlinear response of open systems. Nevertheless, solving the steady states of open quantum systems via HEOM is often a challenging task, due to the vast number of dynamical quantities involved. In this work, we propose a self-consistent iteration approach that quickly solves the HEOM steady states. We demonstrate its high efficiency with accurate and fast evaluations of low-temperature thermal equilibrium of a model Fenna-Matthews-Olson pigment-protein complex. Numerically exact evaluation of thermal equilibrium Rényi entropies and stationary emission line shapes is presented with detailed discussion.

Critical behavior of dissipative two-dimensional spin lattices

NASA Astrophysics Data System (ADS)

Rota, R.; Storme, F.; Bartolo, N.; Fazio, R.; Ciuti, C.

2017-04-01

We explore critical properties of two-dimensional lattices of spins interacting via an anisotropic Heisenberg Hamiltonian that are subject to incoherent spin flips. We determine the steady-state solution of the master equation for the density matrix via the corner-space renormalization method. We investigate the finite-size scaling and critical exponent of the magnetic linear susceptibility associated with a dissipative ferromagnetic transition. We show that the von Neumann entropy increases across the critical point, revealing a strongly mixed character of the ferromagnetic phase. Entanglement is witnessed by the quantum Fisher information, which exhibits a critical behavior at the transition point, showing that quantum correlations play a crucial role in the transition.

Coupled qubits as a quantum heat switch

NASA Astrophysics Data System (ADS)

Karimi, B.; Pekola, J. P.; Campisi, M.; Fazio, R.

2017-12-01

We present a quantum heat switch based on coupled superconducting qubits, connected to two LC resonators that are terminated by resistors providing two heat baths. To describe the system, we use a standard second order master equation with respect to coupling to the baths. We find that this system can act as an efficient heat switch controlled by the applied magnetic flux. The flux influences the energy level separations of the system, and under some conditions, the finite coupling of the qubits enhances the transmitted power between the two baths, by an order of magnitude under realistic conditions. At the same time, the bandwidth at maximum power of the switch formed of the coupled qubits is narrowed.

Exact calculation of the time convolutionless master equation generator: Application to the nonequilibrium resonant level model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kidon, Lyran; The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 69978; Wilner, Eli Y.

2015-12-21

The generalized quantum master equation provides a powerful tool to describe the dynamics in quantum impurity models driven away from equilibrium. Two complementary approaches, one based on Nakajima–Zwanzig–Mori time-convolution (TC) and the other on the Tokuyama–Mori time-convolutionless (TCL) formulations provide a starting point to describe the time-evolution of the reduced density matrix. A key in both approaches is to obtain the so called “memory kernel” or “generator,” going beyond second or fourth order perturbation techniques. While numerically converged techniques are available for the TC memory kernel, the canonical approach to obtain the TCL generator is based on inverting a super-operatormore » in the full Hilbert space, which is difficult to perform and thus, nearly all applications of the TCL approach rely on a perturbative scheme of some sort. Here, the TCL generator is expressed using a reduced system propagator which can be obtained from system observables alone and requires the calculation of super-operators and their inverse in the reduced Hilbert space rather than the full one. This makes the formulation amenable to quantum impurity solvers or to diagrammatic techniques, such as the nonequilibrium Green’s function. We implement the TCL approach for the resonant level model driven away from equilibrium and compare the time scales for the decay of the generator with that of the memory kernel in the TC approach. Furthermore, the effects of temperature, source-drain bias, and gate potential on the TCL/TC generators are discussed.« less

Computational Role of Tunneling in a Programmable Quantum Annealer

NASA Technical Reports Server (NTRS)

Boixo, Sergio; Smelyanskiy, Vadim; Shabani, Alireza; Isakov, Sergei V.; Dykman, Mark; Amin, Mohammad; Mohseni, Masoud; Denchev, Vasil S.; Neven, Hartmut

2016-01-01

Quantum tunneling is a phenomenon in which a quantum state tunnels through energy barriers above the energy of the state itself. Tunneling has been hypothesized as an advantageous physical resource for optimization. Here we present the first experimental evidence of a computational role of multiqubit quantum tunneling in the evolution of a programmable quantum annealer. We developed a theoretical model based on a NIBA Quantum Master Equation to describe the multi-qubit dissipative cotunneling effects under the complex noise characteristics of such quantum devices.We start by considering a computational primitive, the simplest non-convex optimization problem consisting of just one global and one local minimum. The quantum evolutions enable tunneling to the global minimum while the corresponding classical paths are trapped in a false minimum. In our study the non-convex potentials are realized by frustrated networks of qubit clusters with strong intra-cluster coupling. We show that the collective effect of the quantum environment is suppressed in the critical phase during the evolution where quantum tunneling decides the right path to solution. In a later stage dissipation facilitates the multiqubit cotunneling leading to the solution state. The predictions of the model accurately describe the experimental data from the D-WaveII quantum annealer at NASA Ames. In our computational primitive the temperature dependence of the probability of success in the quantum model is opposite to that of the classical paths with thermal hopping. Specially, we provide an analysis of an optimization problem with sixteen qubits,demonstrating eight qubit cotunneling that increases success probabilities. Furthermore, we report results for larger problems with up to 200 qubits that contain the primitive as subproblems.

Quantum magnetism in different AMO systems.

NASA Astrophysics Data System (ADS)

Rey, Ana Maria

One of the most important goals of modern quantum sciences is to learn how to control and entangle many-body systems and use them to make powerful and improved quantum devices, materials and technologies. However, since performing full state tomography does not scale favorably with the number of particles, as the size of quantum systems grow, it becomes extremely challenging to identify, and quantify the buildup of quantum correlations and coherence. In this talk I will report on a protocol that we have developed and experimentally demonstrated in a trapped ion quantum magnet in a Penning trap, which can perform quantum simulations of Ising spin models. In those experiments strong spin-spin interactions can be engineered through optical dipole forces that excite phonons of the crystals. The number of ions can be varied from tens to hundreds with high fidelity control. The protocol uses time reversal of the many-body dynamics, to measure out-of-time-order correlation functions (OTOCs). By measuring a family of OTOCs as a function of a tunable parameter we obtain fine-grained information about the state of the system encoded in the multiple quantum coherence spectrum, extract the quantum state purity, and demonstrate the build-up of up to 8-body correlations. We also use the protocol and comparisons to a full solution of the master equation to investigate the impact of spin-motion entanglement and decoherence in the quantum dynamics. Future applications of this protocol could enable studies of manybody localization, quantum phase transitions, and tests of the holographic duality between quantum and gravitational systems. Supported by NSF-PHY-1521080, JILA-NSF PFC-1125844, ARO and AFOSR-MURI.

Quantum control and measurement of atomic spins in polarization spectroscopy

NASA Astrophysics Data System (ADS)

Deutsch, Ivan H.; Jessen, Poul S.

2010-03-01

Quantum control and measurement are two sides of the same coin. To affect a dynamical map, well-designed time-dependent control fields must be applied to the system of interest. To read out the quantum state, information about the system must be transferred to a probe field. We study a particular example of this dual action in the context of quantum control and measurement of atomic spins through the light-shift interaction with an off-resonant optical probe. By introducing an irreducible tensor decomposition, we identify the coupling of the Stokes vector of the light field with moments of the atomic spin state. This shows how polarization spectroscopy can be used for continuous weak measurement of atomic observables that evolve as a function of time. Simultaneously, the state-dependent light shift induced by the probe field can drive nonlinear dynamics of the spin, and can be used to generate arbitrary unitary transformations on the atoms. We revisit the derivation of the master equation in order to give a unified description of spin dynamics in the presence of both nonlinear dynamics and photon scattering. Based on this formalism, we review applications to quantum control, including the design of state-to-state mappings, and quantum-state reconstruction via continuous weak measurement on a dynamically controlled ensemble.

Deterministic quantum state transfer and remote entanglement using microwave photons.

PubMed

Kurpiers, P; Magnard, P; Walter, T; Royer, B; Pechal, M; Heinsoo, J; Salathé, Y; Akin, A; Storz, S; Besse, J-C; Gasparinetti, S; Blais, A; Wallraff, A

2018-06-01

Sharing information coherently between nodes of a quantum network is fundamental to distributed quantum information processing. In this scheme, the computation is divided into subroutines and performed on several smaller quantum registers that are connected by classical and quantum channels 1 . A direct quantum channel, which connects nodes deterministically rather than probabilistically, achieves larger entanglement rates between nodes and is advantageous for distributed fault-tolerant quantum computation 2 . Here we implement deterministic state-transfer and entanglement protocols between two superconducting qubits fabricated on separate chips. Superconducting circuits 3 constitute a universal quantum node 4 that is capable of sending, receiving, storing and processing quantum information 5-8 . Our implementation is based on an all-microwave cavity-assisted Raman process 9 , which entangles or transfers the qubit state of a transmon-type artificial atom 10 with a time-symmetric itinerant single photon. We transfer qubit states by absorbing these itinerant photons at the receiving node, with a probability of 98.1 ± 0.1 per cent, achieving a transfer-process fidelity of 80.02 ± 0.07 per cent for a protocol duration of only 180 nanoseconds. We also prepare remote entanglement on demand with a fidelity as high as 78.9 ± 0.1 per cent at a rate of 50 kilohertz. Our results are in excellent agreement with numerical simulations based on a master-equation description of the system. This deterministic protocol has the potential to be used for quantum computing distributed across different nodes of a cryogenic network.

Dynamical maps, quantum detailed balance, and the Petz recovery map

NASA Astrophysics Data System (ADS)

Alhambra, Álvaro M.; Woods, Mischa P.

2017-08-01

Markovian master equations (formally known as quantum dynamical semigroups) can be used to describe the evolution of a quantum state ρ when in contact with a memoryless thermal bath. This approach has had much success in describing the dynamics of real-life open quantum systems in the laboratory. Such dynamics increase the entropy of the state ρ and the bath until both systems reach thermal equilibrium, at which point entropy production stops. Our main result is to show that the entropy production at time t is bounded by the relative entropy between the original state and the state at time 2 t . The bound puts strong constraints on how quickly a state can thermalize, and we prove that the factor of 2 is tight. The proof makes use of a key physically relevant property of these dynamical semigroups, detailed balance, showing that this property is intimately connected with the field of recovery maps from quantum information theory. We envisage that the connections made here between the two fields will have further applications. We also use this connection to show that a similar relation can be derived when the fixed point is not thermal.

Stochastic theory of non-Markovian open quantum system

NASA Astrophysics Data System (ADS)

Zhao, Xinyu

In this thesis, a stochastic approach to solving non-Markovian open quantum system called "non-Markovian quantum state diffusion" (NMQSD) approach is discussed in details. The NMQSD approach can serve as an analytical and numerical tool to study the dynamics of the open quantum systems. We explore three main topics of the NMQSD approach. First, we extend the NMQSD approach to many-body open systems such as two-qubit system and coupled N-cavity system. Based on the exact NMQSD equations and the corresponding master equations, we investigate several interesting non-Markovian features due to the memory effect of the environment such as the entanglement generation in two-qubit system and the coherence and entanglement transfer between cavities. Second, we extend the original NMQSD approach to the case that system is coupled to a fermionic bath or a spin bath. By introducing the anti-commutative Grassmann noise and the fermionic coherent state, we derive a fermionic NMQSD equation and the corresponding master equation. The fermionic NMQSD is illustrated by several examples. In a single qubit dissipative example, we have explicitly demonstrated that the NMQSD approach and the ordinary quantum mechanics give rise to the exactly same results. We also show the difference between fermionic bath and bosonic bath. Third, we combine the bosonic and fermionic NMQSD approach to develop a unified NMQSD approach to study the case that an open system is coupled to a bosonic bath and a fermionic bath simultaneously. For all practical purposes, we develop a set of useful computer programs (NMQSD Toolbox) to implement the NMQSD equation in realistic computations. In particular, we develop an algorithm to calculate the exact O operator involved in the NMQSD equation. The NMQSD toolbox is designed to be user friendly, so it will be especially valuable for a non-expert who has interest to employ the NMQSD equation to solve a practical problem. Apart from the central topics on the NMQSD approach, we also study the environment-assisted error correction (EAEC) scheme. We have proposed two new schemes beyond the original EAEC scheme. Our schemes can be used to recover an unknown entangled initial state for a dephasing channel and recover an arbitrary unknown initial state for a dissipative channel using a generalized quantum measurement.

Fundamental Structure of Loop Quantum Gravity

NASA Astrophysics Data System (ADS)

Han, Muxin; Ma, Yongge; Huang, Weiming

In the recent twenty years, loop quantum gravity, a background independent approach to unify general relativity and quantum mechanics, has been widely investigated. The aim of loop quantum gravity is to construct a mathematically rigorous, background independent, non-perturbative quantum theory for a Lorentzian gravitational field on a four-dimensional manifold. In the approach, the principles of quantum mechanics are combined with those of general relativity naturally. Such a combination provides us a picture of, so-called, quantum Riemannian geometry, which is discrete on the fundamental scale. Imposing the quantum constraints in analogy from the classical ones, the quantum dynamics of gravity is being studied as one of the most important issues in loop quantum gravity. On the other hand, the semi-classical analysis is being carried out to test the classical limit of the quantum theory. In this review, the fundamental structure of loop quantum gravity is presented pedagogically. Our main aim is to help non-experts to understand the motivations, basic structures, as well as general results. It may also be beneficial to practitioners to gain insights from different perspectives on the theory. We will focus on the theoretical framework itself, rather than its applications, and do our best to write it in modern and precise langauge while keeping the presentation accessible for beginners. After reviewing the classical connection dynamical formalism of general relativity, as a foundation, the construction of the kinematical Ashtekar-Isham-Lewandowski representation is introduced in the content of quantum kinematics. The algebraic structure of quantum kinematics is also discussed. In the content of quantum dynamics, we mainly introduce the construction of a Hamiltonian constraint operator and the master constraint project. At last, some applications and recent advances are outlined. It should be noted that this strategy of quantizing gravity can also be extended to obtain other background-independent quantum gauge theories. There is no divergence within this background-independent and diffeomorphism-invariant quantization program of matter coupled to gravity.

Remarks on Chern-Simons Invariants

NASA Astrophysics Data System (ADS)

Cattaneo, Alberto S.; Mnëv, Pavel

2010-02-01

The perturbative Chern-Simons theory is studied in a finite-dimensional version or assuming that the propagator satisfies certain properties (as is the case, e.g., with the propagator defined by Axelrod and Singer). It turns out that the effective BV action is a function on cohomology (with shifted degrees) that solves the quantum master equation and is defined modulo certain canonical transformations that can be characterized completely. Out of it one obtains invariants.

Narrow linewidth diode laser modules for quantum optical sensor applications in the field and in space

NASA Astrophysics Data System (ADS)

Wicht, A.; Bawamia, A.; Krüger, M.; Kürbis, Ch.; Schiemangk, M.; Smol, R.; Peters, A.; Tränkle, G.

2017-02-01

We present the status of our efforts to develop very compact and robust diode laser modules specifically suited for quantum optics experiments in the field and in space. The paper describes why hybrid micro-integration and GaAs-diode laser technology is best suited to meet the needs of such applications. The electro-optical performance achieved with hybrid micro-integrated, medium linewidth, high power distributed-feedback master-oscillator-power-amplifier modules and with medium power, narrow linewidth extended cavity diode lasers emitting at 767 nm and 780 nm are briefly described and the status of space relevant stress tests and space heritage is summarized. We also describe the performance of an ECDL operating at 1070 nm. Further, a novel and versatile technology platform is introduced that allows for integration of any type of laser system or electro-optical module that can be constructed from two GaAs chips. This facilitates, for the first time, hybrid micro-integration, e.g. of extended cavity diode laser master-oscillator-poweramplifier modules, of dual-stage optical amplifiers, or of lasers with integrated, chip-based phase modulator. As an example we describe the implementation of an ECDL-MOPA designed for experiments on ultra-cold rubidium and potassium atoms on board a sounding rocket and give basic performance parameters.

Polaron effects on the performance of light-harvesting systems: a quantum heat engine perspective

NASA Astrophysics Data System (ADS)

Xu, Dazhi; Wang, Chen; Zhao, Yang; Cao, Jianshu

2016-02-01

We explore energy transfer in a generic three-level system, which is coupled to three non-equilibrium baths. Built on the concept of quantum heat engine, our three-level model describes non-equilibrium quantum processes including light-harvesting energy transfer, nano-scale heat transfer, photo-induced isomerization, and photovoltaics in double quantum-dots. In the context of light-harvesting, the excitation energy is first pumped up by sunlight, then is transferred via two excited states which are coupled to a phonon bath, and finally decays to the reaction center. The efficiency of this process is evaluated by steady state analysis via a polaron-transformed master equation; thus the entire range of the system-phonon coupling strength can be covered. We show that the coupling with the phonon bath not only modifies the steady state, resulting in population inversion, but also introduces a finite steady state coherence which optimizes the energy transfer flux and efficiency. In the strong coupling limit, the steady state coherence disappears and the efficiency recovers the heat engine limit given by Scovil and Schultz-Dubois (1959 Phys. Rev. Lett. 2 262).

From quantum stochastic differential equations to Gisin-Percival state diffusion

NASA Astrophysics Data System (ADS)

Parthasarathy, K. R.; Usha Devi, A. R.

2017-08-01

Starting from the quantum stochastic differential equations of Hudson and Parthasarathy [Commun. Math. Phys. 93, 301 (1984)] and exploiting the Wiener-Itô-Segal isomorphism between the boson Fock reservoir space Γ (L2(R+ ) ⊗(Cn⊕Cn ) ) and the Hilbert space L2(μ ) , where μ is the Wiener probability measure of a complex n-dimensional vector-valued standard Brownian motion {B (t ) ,t ≥0 } , we derive a non-linear stochastic Schrödinger equation describing a classical diffusion of states of a quantum system, driven by the Brownian motion B. Changing this Brownian motion by an appropriate Girsanov transformation, we arrive at the Gisin-Percival state diffusion equation [N. Gisin and J. Percival, J. Phys. A 167, 315 (1992)]. This approach also yields an explicit solution of the Gisin-Percival equation, in terms of the Hudson-Parthasarathy unitary process and a randomized Weyl displacement process. Irreversible dynamics of system density operators described by the well-known Gorini-Kossakowski-Sudarshan-Lindblad master equation is unraveled by coarse-graining over the Gisin-Percival quantum state trajectories.

Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling

NASA Astrophysics Data System (ADS)

Wang, Chen; Ren, Jie; Cao, Jianshu

2015-07-01

Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices.

Markov Chain-Like Quantum Biological Modeling of Mutations, Aging, and Evolution.

PubMed

Djordjevic, Ivan B

2015-08-24

Recent evidence suggests that quantum mechanics is relevant in photosynthesis, magnetoreception, enzymatic catalytic reactions, olfactory reception, photoreception, genetics, electron-transfer in proteins, and evolution; to mention few. In our recent paper published in Life, we have derived the operator-sum representation of a biological channel based on codon basekets, and determined the quantum channel model suitable for study of the quantum biological channel capacity. However, this model is essentially memoryless and it is not able to properly model the propagation of mutation errors in time, the process of aging, and evolution of genetic information through generations. To solve for these problems, we propose novel quantum mechanical models to accurately describe the process of creation spontaneous, induced, and adaptive mutations and their propagation in time. Different biological channel models with memory, proposed in this paper, include: (i) Markovian classical model, (ii) Markovian-like quantum model, and (iii) hybrid quantum-classical model. We then apply these models in a study of aging and evolution of quantum biological channel capacity through generations. We also discuss key differences of these models with respect to a multilevel symmetric channel-based Markovian model and a Kimura model-based Markovian process. These models are quite general and applicable to many open problems in biology, not only biological channel capacity, which is the main focus of the paper. We will show that the famous quantum Master equation approach, commonly used to describe different biological processes, is just the first-order approximation of the proposed quantum Markov chain-like model, when the observation interval tends to zero. One of the important implications of this model is that the aging phenotype becomes determined by different underlying transition probabilities in both programmed and random (damage) Markov chain-like models of aging, which are mutually coupled.

Markov Chain-Like Quantum Biological Modeling of Mutations, Aging, and Evolution

PubMed Central

Djordjevic, Ivan B.

2015-01-01

Recent evidence suggests that quantum mechanics is relevant in photosynthesis, magnetoreception, enzymatic catalytic reactions, olfactory reception, photoreception, genetics, electron-transfer in proteins, and evolution; to mention few. In our recent paper published in Life, we have derived the operator-sum representation of a biological channel based on codon basekets, and determined the quantum channel model suitable for study of the quantum biological channel capacity. However, this model is essentially memoryless and it is not able to properly model the propagation of mutation errors in time, the process of aging, and evolution of genetic information through generations. To solve for these problems, we propose novel quantum mechanical models to accurately describe the process of creation spontaneous, induced, and adaptive mutations and their propagation in time. Different biological channel models with memory, proposed in this paper, include: (i) Markovian classical model, (ii) Markovian-like quantum model, and (iii) hybrid quantum-classical model. We then apply these models in a study of aging and evolution of quantum biological channel capacity through generations. We also discuss key differences of these models with respect to a multilevel symmetric channel-based Markovian model and a Kimura model-based Markovian process. These models are quite general and applicable to many open problems in biology, not only biological channel capacity, which is the main focus of the paper. We will show that the famous quantum Master equation approach, commonly used to describe different biological processes, is just the first-order approximation of the proposed quantum Markov chain-like model, when the observation interval tends to zero. One of the important implications of this model is that the aging phenotype becomes determined by different underlying transition probabilities in both programmed and random (damage) Markov chain-like models of aging, which are mutually coupled. PMID:26305258

Open quantum system approach to the modeling of spin recombination reactions.

PubMed

Tiersch, M; Steiner, U E; Popescu, S; Briegel, H J

2012-04-26

In theories of spin-dependent radical pair reactions, the time evolution of the radical pair, including the effect of the chemical kinetics, is described by a master equation in the Liouville formalism. For the description of the chemical kinetics, a number of possible reaction operators have been formulated in the literature. In this work, we present a framework that allows for a unified description of the various proposed mechanisms and the forms of reaction operators for the spin-selective recombination processes. On the basis of the concept that master equations can be derived from a microscopic description of the spin system interacting with external degrees of freedom, it is possible to gain insight into the underlying microscopic processes and develop a systematic approach toward determining the specific form of the reaction operator in concrete scenarios.

Quantum fuel with multilevel atomic coherence for ultrahigh specific work in a photonic Carnot engine

NASA Astrophysics Data System (ADS)

Türkpençe, Deniz; Müstecaplıoǧlu, Özgür E.

2016-01-01

We investigate scaling of work and efficiency of a photonic Carnot engine with a number of quantum coherent resources. Specifically, we consider a generalization of the "phaseonium fuel" for the photonic Carnot engine, which was first introduced as a three-level atom with two lower states in a quantum coherent superposition by M. O. Scully, M. Suhail Zubairy, G. S. Agarwal, and H. Walther [Science 299, 862 (2003), 10.1126/science.1078955], to the case of N +1 level atoms with N coherent lower levels. We take into account atomic relaxation and dephasing as well as the cavity loss and derive a coarse-grained master equation to evaluate the work and efficiency analytically. Analytical results are verified by microscopic numerical examination of the thermalization dynamics. We find that efficiency and work scale quadratically with the number of quantum coherent levels. Quantum coherence boost to the specific energy (work output per unit mass of the resource) is a profound fundamental difference of quantum fuel from classical resources. We consider typical modern resonator set ups and conclude that multilevel phaseonium fuel can be utilized to overcome the decoherence in available systems. Preparation of the atomic coherences and the associated cost of coherence are analyzed and the engine operation within the bounds of the second law is verified. Our results bring the photonic Carnot engines much closer to the capabilities of current resonator technologies.

A flexible master oscillator for a pulse-burst laser system

NASA Astrophysics Data System (ADS)

Den Hartog, D. J.; Young, W. C.

2015-12-01

A new master oscillator is being installed in the pulse-burst laser system used for high-rep-rate Thomson scattering on the MST experiment. This new master oscillator will enable pulse repetition rates up to 1 MHz, with the ability to program a burst of pulses with arbitrary and varying time separation between each pulse. In addition, the energy of each master oscillator pulse can be adjusted to compensate for gain variations in the power amplifier section of the laser system. This flexibility is accomplished by chopping a CW laser source with a high-bandwidth acousto-optic modulator (AOM). The laser source is a Laser Quantum ventus 1064 diode-pumped solid-state laser with continuous output power variable from 100 to 500 mW. The 1064 nm, 2.7 mm diameter polarized beam is focused into the gallium phosphide crystal of a Brimrose AOM, which deflects the beam by approximately 60 mR when driven by the 400 MHz fixed frequency driver. Beam deflection is controlled by a simple digital input pulse, and is capable of producing deflected pulses of less than 20 ns width at repetition rates much greater than 1 MHz. These deflected pulses from the output of the AOM are collimated and propagated into the laser amplifier system, where they will be amplified to ~ 2 J/pulse and injected into the MST plasma.

Quantum to classical transition in quantum field theory

NASA Astrophysics Data System (ADS)

Lombardo, Fernando C.

1998-12-01

We study the quatum to classical transition process in the context of quantum field theory. Extending the influence functional formalism of Feynman and Vernon, we study the decoherence process for self-interacting quantum fields in flat space. We also use this formalism for arbitrary geometries to analyze the quantum to classical transition in quantum gravity. After summarizing the main results known for the quantum Brownian motion, we consider a self-interacting field theory in Minkowski spacetime. We compute a coarse grained effective action by integrating out the field modes with wavelength shorter than a critical value. From this effective action we obtain the evolution equation for the reduced density matrix (master equation). We compute the diffusion coefficients for this equation and analyze the decoherence induced on the long-wavelength modes. We generalize the results to the case of a conformally coupled scalar field in de Sitter spacetime. We show that the decoherence is effective as long as the critical wavelength is taken to be not shorter than the Hubble radius. On the other hand, we study the classical limit for scalar-tensorial models in two dimensions. We consider different couplings between the dilaton and the scalar field. We discuss the Hawking radiation process and, from an exact evaluation of the influence functional, we study the conditions by which decoherence ensures the validity of the semiclassical approximation in cosmological metrics. Finally we consider four dimensional models with massive scalar fields, arbitrary coupled to the geometry. We compute the Einstein-Langevin equations in order to study the effect of the fluctuations induced by the quantum fields on the classical geometry.

Exact Dynamics via Poisson Process: a unifying Monte Carlo paradigm

NASA Astrophysics Data System (ADS)

Gubernatis, James

2014-03-01

A common computational task is solving a set of ordinary differential equations (o.d.e.'s). A little known theorem says that the solution of any set of o.d.e.'s is exactly solved by the expectation value over a set of arbitary Poisson processes of a particular function of the elements of the matrix that defines the o.d.e.'s. The theorem thus provides a new starting point to develop real and imaginary-time continous-time solvers for quantum Monte Carlo algorithms, and several simple observations enable various quantum Monte Carlo techniques and variance reduction methods to transfer to a new context. I will state the theorem, note a transformation to a very simple computational scheme, and illustrate the use of some techniques from the directed-loop algorithm in context of the wavefunction Monte Carlo method that is used to solve the Lindblad master equation for the dynamics of open quantum systems. I will end by noting that as the theorem does not depend on the source of the o.d.e.'s coming from quantum mechanics, it also enables the transfer of continuous-time methods from quantum Monte Carlo to the simulation of various classical equations of motion heretofore only solved deterministically.

Quantum resonances and regularity islands in quantum maps

PubMed

Sokolov; Zhirov; Alonso; Casati

2000-05-01

We study analytically as well as numerically the dynamics of a quantum map near a quantum resonance of an order q. The map is embedded into a continuous unitary transformation generated by a time-independent quasi-Hamiltonian. Such a Hamiltonian generates at the very point of the resonance a local gauge transformation described by the unitary unimodular group SU(q). The resonant energy growth is attributed to the zero Liouville eigenmodes of the generator in the adjoint representation of the group while the nonzero modes yield saturating with time contribution. In a vicinity of a given resonance, the quasi-Hamiltonian is then found in the form of power expansion with respect to the detuning from the resonance. The problem is related in this way to the motion along a circle in a (q2 - 1)-component inhomogeneous "magnetic" field of a quantum particle with q intrinsic degrees of freedom described by the SU(q) group. This motion is in parallel with the classical phase oscillations near a nonlinear resonance. The most important role is played by the resonances with the orders much smaller than the typical localization length q < l. Such resonances master for exponentially long though finite times the motion in some domains around them. Explicit analytical solution is possible for a few lowest and strongest resonances.

Cavity QED at the quantum-classical boundary

NASA Astrophysics Data System (ADS)

Fink, J. M.; Steffen, L.; Bishop, L. S.; Wallraff, A.

2010-03-01

The quantum limit of cavity QED is characterized by a well resolved vacuum Rabi mode splitting spectrum. If the number of excitations n in the resonantly coupled matter-light system is increased from one, the nonlinear √n scaling of the dressed eigenstates is observed [1]. At very large photon numbers the transmission spectrum turns into a single Lorentzian line as expected from the correspondence principle. This classical limit emerges when the occupancy of the low energy dressed states is increased until the quantum nonlinearity of the available transitions becomes small compared to dephasing and relaxation rates [2]. We explore this quantum-classical crossover in a circuit QED system where we vary the thermal occupation of the resonator by 5 orders of magnitude using a quasi-thermal noise source. From vacuum Rabi spectra measured in linear response and from time resolved vacuum Rabi oscillation measurements we consistently extract cavity field temperatures between 100 mK and 10 K using a master equation model. The presented experimental approach is useful to determine the thermal occupation of a quantum system and offers the possibility to study entanglement and decoherence at elevated temperatures. [1] J. M. Fink et al. Nature 454, 315 (2008). [2] I. Rau, et al. Phys. Rev. B 70, 054521 (2004).

Relation between random walks and quantum walks

NASA Astrophysics Data System (ADS)

Boettcher, Stefan; Falkner, Stefan; Portugal, Renato

2015-05-01

Based on studies of four specific networks, we conjecture a general relation between the walk dimensions dw of discrete-time random walks and quantum walks with the (self-inverse) Grover coin. In each case, we find that dw of the quantum walk takes on exactly half the value found for the classical random walk on the same geometry. Since walks on homogeneous lattices satisfy this relation trivially, our results for heterogeneous networks suggest that such a relation holds irrespective of whether translational invariance is maintained or not. To develop our results, we extend the renormalization-group analysis (RG) of the stochastic master equation to one with a unitary propagator. As in the classical case, the solution ρ (x ,t ) in space and time of this quantum-walk equation exhibits a scaling collapse for a variable xdw/t in the weak limit, which defines dw and illuminates fundamental aspects of the walk dynamics, e.g., its mean-square displacement. We confirm the collapse for ρ (x ,t ) in each case with extensive numerical simulation. The exact values for dw themselves demonstrate that RG is a powerful complementary approach to study the asymptotics of quantum walks that weak-limit theorems have not been able to access, such as for systems lacking translational symmetries beyond simple trees.

Fokker-Planck equation of the reduced Wigner function associated to an Ohmic quantum Langevin dynamics

NASA Astrophysics Data System (ADS)

Colmenares, Pedro J.

2018-05-01

This article has to do with the derivation and solution of the Fokker-Planck equation associated to the momentum-integrated Wigner function of a particle subjected to a harmonic external field in contact with an ohmic thermal bath of quantum harmonic oscillators. The strategy employed is a simplified version of the phenomenological approach of Schramm, Jung, and Grabert of interpreting the operators as c numbers to derive the quantum master equation arising from a twofold transformation of the Wigner function of the entire phase space. The statistical properties of the random noise comes from the integral functional theory of Grabert, Schramm, and Ingold. By means of a single Wigner transformation, a simpler equation than that mentioned before is found. The Wigner function reproduces the known results of the classical limit. This allowed us to rewrite the underdamped classical Langevin equation as a first-order stochastic differential equation with time-dependent drift and diffusion terms.

Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling

PubMed Central

Wang, Chen; Ren, Jie; Cao, Jianshu

2015-01-01

Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices. PMID:26152705

Mid infrared quantum cascade laser operating in pure amplitude modulation for background-free trace gas spectroscopy.

PubMed

Bidaux, Yves; Bismuto, Alfredo; Patimisco, Pietro; Sampaolo, Angelo; Gresch, Tobias; Strubi, Gregory; Blaser, Stéphane; Tittel, Frank K; Spagnolo, Vincenzo; Muller, Antoine; Faist, Jérôme

2016-11-14

We present a single mode multi-section quantum cascade laser source composed of three different sections: master oscillator, gain and phase section. Non-uniform pumping of the QCL's gain reveals that the various laser sections are strongly coupled. Simulations of the electronic and optical properties of the laser (based on the density matrix and scattering matrix formalisms, respectively) were performed and a good agreement with measurements is obtained. In particular, a pure modulation of the laser output power can be achieved. This capability of the device is applied in tunable-laser spectroscopy of N₂O where background-free quartz enhanced photo acoustic spectral scans with nearly perfect Voigt line shapes for the selected absorption line are obtained.

Theoretical Transport Studies of Non-equilibrium Carriers Driven by High Electric Fields

DTIC Science & Technology

2012-04-25

for two different types of confinement. Motivated by our desire to understand scattering processes in quantum wires in a simple way, in the final...Π’s are probability propagators. The probability propagators can be found, for example, by solving a Master equation if the motion is fully inco - herent...shown that when the transport is coherent (i.e. there are no phase- breaking scattering processes ), the current in the conductor is related to the

C++QEDv2: The multi-array concept and compile-time algorithms in the definition of composite quantum systems

NASA Astrophysics Data System (ADS)

Vukics, András

2012-06-01

C++QED is a versatile framework for simulating open quantum dynamics. It allows to build arbitrarily complex quantum systems from elementary free subsystems and interactions, and simulate their time evolution with the available time-evolution drivers. Through this framework, we introduce a design which should be generic for high-level representations of composite quantum systems. It relies heavily on the object-oriented and generic programming paradigms on one hand, and on the other hand, compile-time algorithms, in particular C++ template-metaprogramming techniques. The core of the design is the data structure which represents the state vectors of composite quantum systems. This data structure models the multi-array concept. The use of template metaprogramming is not only crucial to the design, but with its use all computations pertaining to the layout of the simulated system can be shifted to compile time, hence cutting on runtime. Program summaryProgram title: C++QED Catalogue identifier: AELU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELU_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions:http://cpc.cs.qub.ac.uk/licence/aelu_v1_0.html. The C++QED package contains other software packages, Blitz, Boost and FLENS, all of which may be distributed freely but have individual license requirements. Please see individual packages for license conditions. No. of lines in distributed program, including test data, etc.: 597 974 No. of bytes in distributed program, including test data, etc.: 4 874 839 Distribution format: tar.gz Programming language: C++ Computer: i386-i686, x86_64 Operating system: In principle cross-platform, as yet tested only on UNIX-like systems (including Mac OS X). RAM: The framework itself takes about 60 MB, which is fully shared. The additional memory taken by the program which defines the actual physical system (script) is typically less than 1 MB. The memory storing the actual data scales with the system dimension for state-vector manipulations, and the square of the dimension for density-operator manipulations. This might easily be GBs, and often the memory of the machine limits the size of the simulated system. Classification: 4.3, 4.13, 6.2, 20 External routines: Boost C++ libraries (http://www.boost.org/), GNU Scientific Library (http://www.gnu.org/software/gsl/), Blitz++ (http://www.oonumerics.org/blitz/), Linear Algebra Package - Flexible Library for Efficient Numerical Solutions (http://flens.sourceforge.net/). Nature of problem: Definition of (open) composite quantum systems out of elementary building blocks [1]. Manipulation of such systems, with emphasis on dynamical simulations such as Master-equation evolution [2] and Monte Carlo wave-function simulation [3]. Solution method: Master equation, Monte Carlo wave-function method. Restrictions: Total dimensionality of the system. Master equation - few thousands. Monte Carlo wave-function trajectory - several millions. Unusual features: Because of the heavy use of compile-time algorithms, compilation of programs written in the framework may take a long time and much memory (up to several GBs). Additional comments: The framework is not a program, but provides and implements an application-programming interface for developing simulations in the indicated problem domain. Supplementary information: http://cppqed.sourceforge.net/. Running time: Depending on the magnitude of the problem, can vary from a few seconds to weeks.

Master equation for open two-band systems and its applications to Hall conductance

NASA Astrophysics Data System (ADS)

Shen, H. Z.; Zhang, S. S.; Dai, C. M.; Yi, X. X.

2018-02-01

Hall conductivity in the presence of a dephasing environment has recently been investigated with a dissipative term introduced phenomenologically. In this paper, we study the dissipative topological insulator (TI) and its topological transition in the presence of quantized electromagnetic environments. A Lindblad-type equation is derived to determine the dynamics of a two-band system. When the two-band model describes TIs, the environment may be the fluctuations of radiation that surround the TIs. We find the dependence of decay rates in the master equation on Bloch vectors in the two-band system, which leads to a mixing of the band occupations. Hence the environment-induced current is in general not perfectly topological in the presence of coupling to the environment, although deviations are small in the weak limit. As an illustration, we apply the Bloch-vector-dependent master equation to TIs and calculate the Hall conductance of tight-binding electrons in a two-dimensional lattice. The influence of environments on the Hall conductance is presented and discussed. The calculations show that the phase transition points of the TIs are robust against the quantized electromagnetic environment. The results might bridge the gap between quantum optics and topological photonic materials.

The Master Equation for Two-Level Accelerated Systems at Finite Temperature

NASA Astrophysics Data System (ADS)

Tomazelli, J. L.; Cunha, R. O.

2016-10-01

In this work, we study the behaviour of two weakly coupled quantum systems, described by a separable density operator; one of them is a single oscillator, representing a microscopic system, while the other is a set of oscillators which perform the role of a reservoir in thermal equilibrium. From the Liouville-Von Neumann equation for the reduced density operator, we devise the master equation that governs the evolution of the microscopic system, incorporating the effects of temperature via Thermofield Dynamics formalism by suitably redefining the vacuum of the macroscopic system. As applications, we initially investigate the behaviour of a Fermi oscillator in the presence of a heat bath consisting of a set of Fermi oscillators and that of an atomic two-level system interacting with a scalar radiation field, considered as a reservoir, by constructing the corresponding master equation which governs the time evolution of both sub-systems at finite temperature. Finally, we calculate the energy variation rates for the atom and the field, as well as the atomic population levels, both in the inertial case and at constant proper acceleration, considering the two-level system as a prototype of an Unruh detector, for admissible couplings of the radiation field.

Continuous measurement of an atomic current

NASA Astrophysics Data System (ADS)

Laflamme, C.; Yang, D.; Zoller, P.

2017-04-01

We are interested in dynamics of quantum many-body systems under continuous observation, and its physical realizations involving cold atoms in lattices. In the present work we focus on continuous measurement of atomic currents in lattice models, including the Hubbard model. We describe a Cavity QED setup, where measurement of a homodyne current provides a faithful representation of the atomic current as a function of time. We employ the quantum optical description in terms of a diffusive stochastic Schrödinger equation to follow the time evolution of the atomic system conditional to observing a given homodyne current trajectory, thus accounting for the competition between the Hamiltonian evolution and measurement back action. As an illustration, we discuss minimal models of atomic dynamics and continuous current measurement on rings with synthetic gauge fields, involving both real space and synthetic dimension lattices (represented by internal atomic states). Finally, by "not reading" the current measurements the time evolution of the atomic system is governed by a master equation, where—depending on the microscopic details of our CQED setups—we effectively engineer a current coupling of our system to a quantum reservoir. This provides interesting scenarios of dissipative dynamics generating "dark" pure quantum many-body states.

Effects of photon field on heat transport through a quantum wire attached to leads

NASA Astrophysics Data System (ADS)

Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

2018-01-01

We theoretically investigate photo-thermoelectric transport through a quantum wire in a photon cavity coupled to electron reservoirs with different temperatures. Our approach, based on a quantum master equation, allows us to investigate the influence of a quantized photon field on the heat current and thermoelectric transport in the system. We find that the heat current through the quantum wire is influenced by the photon field resulting in a negative heat current in certain cases. The characteristics of the transport are studied by tuning the ratio, ħωγ /kB ΔT, between the photon energy, ħωγ, and the thermal energy, kB ΔT. The thermoelectric transport is enhanced by the cavity photons when kB ΔT > ħωγ. By contrast, if kB ΔT < ħωγ, the photon field is dominant and a suppression in the thermoelectric transport can be found in the case when the cavity-photon field is close to a resonance with the two lowest one-electron states in the system. Our approach points to a new technique to amplify thermoelectric current in nano-devices.

Latest improvements on long wave p on n HgCdTe technology at Sofradir

NASA Astrophysics Data System (ADS)

Rubaldo, Laurent; Taalat, Rachid; Berthoz, Jocelyn; Maillard, Magalie; Péré-Laperne, Nicolas; Brunner, Alexandre; Guinedor, Pierre; Dargent, L.; Manissadjian, A.; Reibel, Y.; Kerlain, A.

2017-02-01

SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. As a result, strong and continuous development efforts are deployed to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, dark current, quantum efficiency, low excess noise and high operability. The actual trend in quantum IR detector development is the design of very small pixel, with the higher achievable operating temperature whatever the spectral band. Moreover maintaining the detector operability and image quality at higher temperature moreover for long wavelength is a major issue. This paper presents the recent developments achieved at Sofradir to meet this challenge for LW band MCT extrinsic p on n technology with a cut-off wavelength of 9.3μm at 90K. State of the art performances will be presented in terms of dark current, operability and NETD temperature dependency, quantum efficiency, MTF, and RFPN (Residual Fixed Pattern Noise) stability up to 100K.

Quantum modeling of ultrafast photoinduced charge separation

NASA Astrophysics Data System (ADS)

Rozzi, Carlo Andrea; Troiani, Filippo; Tavernelli, Ivano

2018-01-01

Phenomena involving electron transfer are ubiquitous in nature, photosynthesis and enzymes or protein activity being prominent examples. Their deep understanding thus represents a mandatory scientific goal. Moreover, controlling the separation of photogenerated charges is a crucial prerequisite in many applicative contexts, including quantum electronics, photo-electrochemical water splitting, photocatalytic dye degradation, and energy conversion. In particular, photoinduced charge separation is the pivotal step driving the storage of sun light into electrical or chemical energy. If properly mastered, these processes may also allow us to achieve a better command of information storage at the nanoscale, as required for the development of molecular electronics, optical switching, or quantum technologies, amongst others. In this Topical Review we survey recent progress in the understanding of ultrafast charge separation from photoexcited states. We report the state-of-the-art of the observation and theoretical description of charge separation phenomena in the ultrafast regime mainly focusing on molecular- and nano-sized solar energy conversion systems. In particular, we examine different proposed mechanisms driving ultrafast charge dynamics, with particular regard to the role of quantum coherence and electron-nuclear coupling, and link experimental observations to theoretical approaches based either on model Hamiltonians or on first principles simulations.

Quantum fuel with multilevel atomic coherence for ultrahigh specific work in a photonic Carnot engine.

PubMed

Türkpençe, Deniz; Müstecaplıoğlu, Özgür E

2016-01-01

We investigate scaling of work and efficiency of a photonic Carnot engine with a number of quantum coherent resources. Specifically, we consider a generalization of the "phaseonium fuel" for the photonic Carnot engine, which was first introduced as a three-level atom with two lower states in a quantum coherent superposition by M. O. Scully, M. Suhail Zubairy, G. S. Agarwal, and H. Walther [Science 299, 862 (2003)SCIEAS0036-807510.1126/science.1078955], to the case of N+1 level atoms with N coherent lower levels. We take into account atomic relaxation and dephasing as well as the cavity loss and derive a coarse-grained master equation to evaluate the work and efficiency analytically. Analytical results are verified by microscopic numerical examination of the thermalization dynamics. We find that efficiency and work scale quadratically with the number of quantum coherent levels. Quantum coherence boost to the specific energy (work output per unit mass of the resource) is a profound fundamental difference of quantum fuel from classical resources. We consider typical modern resonator set ups and conclude that multilevel phaseonium fuel can be utilized to overcome the decoherence in available systems. Preparation of the atomic coherences and the associated cost of coherence are analyzed and the engine operation within the bounds of the second law is verified. Our results bring the photonic Carnot engines much closer to the capabilities of current resonator technologies.

Quantum coherence effects in natural light-induced processes: cis-trans photoisomerization of model retinal under incoherent excitation.

PubMed

Tscherbul, Timur V; Brumer, Paul

2015-12-14

We present a theoretical study of quantum coherence effects in the primary cis-trans photoisomerization of retinal in rhodopsin induced by incoherent solar light. Using the partial secular Bloch-Redfield quantum master equation approach based on a two-state two-mode linear vibronic coupling model of the retinal chromophore [S. Hahn and G. Stock, J. Phys. Chem. B, 2000, 104, 1146-1149], we show that a sudden turn-on of incoherent pumping can generate substantial Fano coherences among the excited states of retinal. These coherences are the most pronounced in the regime where the matrix elements of the transition dipole moment between the ground and excited eigenstates are parallel to one another. We show that even when the transition dipole moments are perpendicular (implying the absence of light-induced Fano coherence) a small amount of excited-state coherence is still generated due to the coupling to intramolecular vibrational modes and the protein environment, causing depopulation of the excited eigenstates. The overall effect of the coherences on the steady-state population and on the photoproduct quantum yield is shown to be small; however we observe a significant transient effect on the formation of the trans photoproduct, enhancing the photoreaction quantum yield by ∼11% at 200 fs. These calculations suggest that coupling to intramolecular vibrational modes and the protein environment play an important role in photoreaction dynamics, suppressing oscillations in the quantum yield associated with Fano interference.

Generalized Quantum Theory and Mathematical Foundations of Quantum Field Theory

NASA Astrophysics Data System (ADS)

Maroun, Michael Anthony

This dissertation is divided into two main topics. The first is the generalization of quantum dynamics when the Schrodinger partial differential equation is not defined even in the weak mathematical sense because the potential function itself is a distribution in the spatial variable, the same variable that is used to define the kinetic energy operator, i.e. the Laplace operator. The procedure is an extension and broadening of the distributional calculus and offers spectral results as an alternative to the only other two known methods to date, namely a) the functional calculi; and b) non-standard analysis. Furthermore, the generalizations of quantum dynamics presented within give a resolution to the time asymmetry paradox created by multi-particle quantum mechanics due to the time evolution still being unitary. A consequence is the randomization of phases needed for the fundamental justification Pauli master equation. The second topic is foundations of the quantum theory of fields. The title is phrased as ``foundations'' to emphasize that there is no claim of uniqueness but rather a proposal is put forth, which is markedly different than that of constructive or axiomatic field theory. In particular, the space of fields is defined as a space of generalized functions with involutive symmetry maps (the CPT invariance) that affect the topology of the field space. The space of quantum fields is then endowed the Frechet property and interactions change the topology in such a way as to cause some field spaces to be incompatible with others. This is seen in the consequences of the Haag theorem. Various examples and discussions are given that elucidate a new view of the quantum theory of fields and its (lack of) mathematical structure.

Laser cooling of a trapped two-component Fermi gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Idziaszek, Z.; Centrum Fizyki Teoretycznej, Polska Akademia Nauk, 02-668 Warsaw; Santos, L.

2003-04-01

We study the collective Raman cooling of a trapped two-component Fermi gas using quantum master equation in the festina lente regime, where the heating due to photon reabsorption can be neglected. The Monte Carlo simulations show that three-dimensional temperatures of the order of 0.008T{sub F} can be achieved. We analyze the heating related to background losses, and show that our laser-cooling scheme can maintain the temperature of the gas without significant additional losses.

Quantum angular momentum diffusion of rigid bodies

NASA Astrophysics Data System (ADS)

Papendell, Birthe; Stickler, Benjamin A.; Hornberger, Klaus

2017-12-01

We show how to describe the diffusion of the quantized angular momentum vector of an arbitrarily shaped rigid rotor as induced by its collisional interaction with an environment. We present the general form of the Lindblad-type master equation and relate it to the orientational decoherence of an asymmetric nanoparticle in the limit of small anisotropies. The corresponding diffusion coefficients are derived for gas particles scattering off large molecules and for ambient photons scattering off dielectric particles, using the elastic scattering amplitudes.

C++QEDv2 Milestone 10: A C++/Python application-programming framework for simulating open quantum dynamics

NASA Astrophysics Data System (ADS)

Sandner, Raimar; Vukics, András

2014-09-01

The v2 Milestone 10 release of C++QED is primarily a feature release, which also corrects some problems of the previous release, especially as regards the build system. The adoption of C++11 features has led to many simplifications in the codebase. A full doxygen-based API manual [1] is now provided together with updated user guides. A largely automated, versatile new testsuite directed both towards computational and physics features allows for quickly spotting arising errors. The states of trajectories are now savable and recoverable with full binary precision, allowing for trajectory continuation regardless of evolution method (single/ensemble Monte Carlo wave-function or Master equation trajectory). As the main new feature, the framework now presents Python bindings to the highest-level programming interface, so that actual simulations for given composite quantum systems can now be performed from Python. Catalogue identifier: AELU_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELU_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: yes No. of lines in distributed program, including test data, etc.: 492422 No. of bytes in distributed program, including test data, etc.: 8070987 Distribution format: tar.gz Programming language: C++/Python. Computer: i386-i686, x86 64. Operating system: In principle cross-platform, as yet tested only on UNIX-like systems (including Mac OS X). RAM: The framework itself takes about 60MB, which is fully shared. The additional memory taken by the program which defines the actual physical system (script) is typically less than 1MB. The memory storing the actual data scales with the system dimension for state-vector manipulations, and the square of the dimension for density-operator manipulations. This might easily be GBs, and often the memory of the machine limits the size of the simulated system. Classification: 4.3, 4.13, 6.2. External routines: Boost C++ libraries, GNU Scientific Library, Blitz++, FLENS, NumPy, SciPy Catalogue identifier of previous version: AELU_v1_0 Journal reference of previous version: Comput. Phys. Comm. 183 (2012) 1381 Does the new version supersede the previous version?: Yes Nature of problem: Definition of (open) composite quantum systems out of elementary building blocks [2,3]. Manipulation of such systems, with emphasis on dynamical simulations such as Master-equation evolution [4] and Monte Carlo wave-function simulation [5]. Solution method: Master equation, Monte Carlo wave-function method Reasons for new version: The new version is mainly a feature release, but it does correct some problems of the previous version, especially as regards the build system. Summary of revisions: We give an example for a typical Python script implementing the ring-cavity system presented in Sec. 3.3 of Ref. [2]: Restrictions: Total dimensionality of the system. Master equation-few thousands. Monte Carlo wave-function trajectory-several millions. Unusual features: Because of the heavy use of compile-time algorithms, compilation of programs written in the framework may take a long time and much memory (up to several GBs). Additional comments: The framework is not a program, but provides and implements an application-programming interface for developing simulations in the indicated problem domain. We use several C++11 features which limits the range of supported compilers (g++ 4.7, clang++ 3.1) Documentation, http://cppqed.sourceforge.net/ Running time: Depending on the magnitude of the problem, can vary from a few seconds to weeks. References: [1] Entry point: http://cppqed.sf.net [2] A. Vukics, C++QEDv2: The multi-array concept and compile-time algorithms in the definition of composite quantum systems, Comp. Phys. Comm. 183(2012)1381. [3] A. Vukics, H. Ritsch, C++QED: an object-oriented framework for wave-function simulations of cavity QED systems, Eur. Phys. J. D 44 (2007) 585. [4] H. J. Carmichael, An Open Systems Approach to Quantum Optics, Springer, 1993. [5] J. Dalibard, Y. Castin, K. Molmer, Wave-function approach to dissipative processes in quantum optics, Phys. Rev. Lett. 68 (1992) 580.

Signatures of a quantum dynamical phase transition in a three-spin system in presence of a spin environment

NASA Astrophysics Data System (ADS)

Álvarez, Gonzalo A.; Levstein, Patricia R.; Pastawski, Horacio M.

2007-09-01

We have observed an environmentally induced quantum dynamical phase transition in the dynamics of a two-spin experimental swapping gate [G.A. Álvarez, E.P. Danieli, P.R. Levstein, H.M. Pastawski, J. Chem. Phys. 124 (2006) 194507]. There, the exchange of the coupled states |↑,↓> and |↓,↑> gives an oscillation with a Rabi frequency b/ℏ (the spin-spin coupling). The interaction, ℏ/τSE with a spin-bath degrades the oscillation with a characteristic decoherence time. We showed that the swapping regime is restricted only to bτSE≳ℏ. However, beyond a critical interaction with the environment the swapping freezes and the system enters to a Quantum Zeno dynamical phase where relaxation decreases as coupling with the environment increases. Here, we solve the quantum dynamics of a two-spin system coupled to a spin-bath within a Liouville-von Neumann quantum master equation and we compare the results with our previous work within the Keldysh formalism. Then, we extend the model to a three interacting spin system where only one is coupled to the environment. Beyond a critical interaction the two spins not coupled to the environment oscillate with the bare Rabi frequency and relax more slowly. This effect is more pronounced when the anisotropy of the system-environment (SE) interaction goes from a purely XY to an Ising interaction form.

Einstein-Podolsky-Rosen paradox implies a minimum achievable temperature

NASA Astrophysics Data System (ADS)

Rogers, David M.

2017-01-01

This work examines the thermodynamic consequences of the repeated partial projection model for coupling a quantum system to an arbitrary series of environments under feedback control. This paper provides observational definitions of heat and work that can be realized in current laboratory setups. In contrast to other definitions, it uses only properties of the environment and the measurement outcomes, avoiding references to the "measurement" of the central system's state in any basis. These definitions are consistent with the usual laws of thermodynamics at all temperatures, while never requiring complete projective measurement of the entire system. It is shown that the back action of measurement must be counted as work rather than heat to satisfy the second law. Comparisons are made to quantum jump (unravelling) and transition-probability based definitions, many of which appear as particular limits of the present model. These limits show that our total entropy production is a lower bound on traditional definitions of heat that trace out the measurement device. Examining the master equation approximation to the process at finite measurement rates, we show that most interactions with the environment make the system unable to reach absolute zero. We give an explicit formula for the minimum temperature achievable in repeatedly measured quantum systems. The phenomenon of minimum temperature offers an explanation of recent experiments aimed at testing fluctuation theorems in the quantum realm and places a fundamental purity limit on quantum computers.

Self-consistent quantum kinetic theory of diatomic molecule formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forrey, Robert C.

2015-07-14

A quantum kinetic theory of molecule formation is presented which includes three-body recombination and radiative association for a thermodynamically closed system which may or may not exchange energy with its surrounding at a constant temperature. The theory uses a Sturmian representation of a two-body continuum to achieve a steady-state solution of a governing master equation which is self-consistent in the sense that detailed balance between all bound and unbound states is rigorously enforced. The role of quasibound states in catalyzing the molecule formation is analyzed in complete detail. The theory is used to make three predictions which differ from conventionalmore » kinetic models. These predictions suggest significant modifications may be needed to phenomenological rate constants which are currently in wide use. Implications for models of low and high density systems are discussed.« less

Nanoscale phase engineering of thermal transport with a Josephson heat modulator.

PubMed

Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

2016-03-01

Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

Waiting time distribution revealing the internal spin dynamics in a double quantum dot

NASA Astrophysics Data System (ADS)

Ptaszyński, Krzysztof

2017-07-01

Waiting time distribution and the zero-frequency full counting statistics of unidirectional electron transport through a double quantum dot molecule attached to spin-polarized leads are analyzed using the quantum master equation. The waiting time distribution exhibits a nontrivial dependence on the value of the exchange coupling between the dots and the gradient of the applied magnetic field, which reveals the oscillations between the spin states of the molecule. The zero-frequency full counting statistics, on the other hand, is independent of the aforementioned quantities, thus giving no insight into the internal dynamics. The fact that the waiting time distribution and the zero-frequency full counting statistics give a nonequivalent information is associated with two factors. Firstly, it can be explained by the sensitivity to different timescales of the dynamics of the system. Secondly, it is associated with the presence of the correlation between subsequent waiting times, which makes the renewal theory, relating the full counting statistics and the waiting time distribution, no longer applicable. The study highlights the particular usefulness of the waiting time distribution for the analysis of the internal dynamics of mesoscopic systems.

Non-linear effects and thermoelectric efficiency of quantum dot-based single-electron transistors.

PubMed

Talbo, Vincent; Saint-Martin, Jérôme; Retailleau, Sylvie; Dollfus, Philippe

2017-11-01

By means of advanced numerical simulation, the thermoelectric properties of a Si-quantum dot-based single-electron transistor operating in sequential tunneling regime are investigated in terms of figure of merit, efficiency and power. By taking into account the phonon-induced collisional broadening of energy levels in the quantum dot, both heat and electrical currents are computed in a voltage range beyond the linear response. Using our homemade code consisting in a 3D Poisson-Schrödinger solver and the resolution of the Master equation, the Seebeck coefficient at low bias voltage appears to be material independent and nearly independent on the level broadening, which makes this device promising for metrology applications as a nanoscale standard of Seebeck coefficient. Besides, at higher voltage bias, the non-linear characteristics of the heat current are shown to be related to the multi-level effects. Finally, when considering only the electronic contribution to the thermal conductance, the single-electron transistor operating in generator regime is shown to exhibit very good efficiency at maximum power.

Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis

NASA Astrophysics Data System (ADS)

Tanabe, Katsuaki

2016-06-01

We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.

Quantum and Information Thermodynamics: A Unifying Framework Based on Repeated Interactions

NASA Astrophysics Data System (ADS)

Strasberg, Philipp; Schaller, Gernot; Brandes, Tobias; Esposito, Massimiliano

2017-04-01

We expand the standard thermodynamic framework of a system coupled to a thermal reservoir by considering a stream of independently prepared units repeatedly put into contact with the system. These units can be in any nonequilibrium state and interact with the system with an arbitrary strength and duration. We show that this stream constitutes an effective resource of nonequilibrium free energy, and we identify the conditions under which it behaves as a heat, work, or information reservoir. We also show that this setup provides a natural framework to analyze information erasure ("Landauer's principle") and feedback-controlled systems ("Maxwell's demon"). In the limit of a short system-unit interaction time, we further demonstrate that this setup can be used to provide a thermodynamically sound interpretation to many effective master equations. We discuss how nonautonomously driven systems, micromasers, lasing without inversion and the electronic Maxwell demon can be thermodynamically analyzed within our framework. While the present framework accounts for quantum features (e.g., squeezing, entanglement, coherence), we also show that quantum resources do not offer any advantage compared to classical ones in terms of the maximum extractable work.

Tailoring Quantum Dot Assemblies to Extend Exciton Coherence Times and Improve Exciton Transport

NASA Astrophysics Data System (ADS)

Seward, Kenton; Lin, Zhibin; Lusk, Mark

2012-02-01

The motion of excitons through nanostructured assemblies plays a central role in a wide range of physical phenomena including quantum computing, molecular electronics, photosynthetic processes, excitonic transistors and light emitting diodes. All of these technologies are severely handicapped, though, by quasi-particle lifetimes on the order of a nanosecond. The movement of excitons must therefore be as efficient as possible in order to move excitons meaningful distances. This is problematic for assemblies of small Si quantum dots (QDs), where excitons quickly localize and entangle with dot phonon modes. Ensuing exciton transport is then characterized by a classical random walk reduced to very short distances because of efficient recombination. We use a combination of master equation (Haken-Strobl) formalism and density functional theory to estimate the rate of decoherence in Si QD assemblies and its impact on exciton mobility. Exciton-phonon coupling and Coulomb interactions are calculated as a function of dot size, spacing and termination to minimize the rate of intra-dot phonon entanglement. This extends the time over which more efficient exciton transport, characterized by partial coherence, can be maintained.

Keldysh meets Lindblad: Correlated Gain and Loss in Higher Order Perturbation Theory

NASA Astrophysics Data System (ADS)

Stace, Tom; Mueller, Clemens

Motivated by correlated decay processes driving gain, loss and lasing in driven artificial quantum systems, we develop a theoretical technique using Keldysh diagrammatic perturbation theory to derive a Lindblad master equation that goes beyond the usual second order perturbation theory. We demonstrate the method on the driven dissipative Rabi model, including terms up to fourth order in the interaction between the qubit and both the resonator and environment. This results in a large class of Lindblad dissipators and associated rates which go beyond the terms that have previously been proposed to describe similar systems. All of the additional terms contribute to the system behaviour at the same order of perturbation theory. We then apply these results to analyse the phonon-assisted steady-state gain of a microwave field driving a double quantum-dot in a resonator. We show that resonator gain and loss are substantially affected by dephasing- assisted dissipative processes in the quantum-dot system. These additional processes, which go beyond recently proposed polaronic theories, are in good quantitative agreement with experimental observations.

An Application of the Theory of Open Quantum Systems to Model the Dynamics of Party Governance in the US Political System

NASA Astrophysics Data System (ADS)

Khrennikova, Polina; Haven, Emmanuel; Khrennikov, Andrei

2014-04-01

The Gorini-Kossakowski-Sudarshan-Lindblad equation allows us to model the process of decision making in US elections. The crucial point we attempt to make is that the voter's mental state can be represented as a superposition of two possible choices for either republicans or democrats. However, reality dictates a more complicated situation: typically a voter participates in two elections, i.e. the congress and the presidential elections. In both elections the voter has to decide between two choices. This very feature of the US election system requires that the mental state is represented by a 2-qubit state corresponding to the superposition of 4 different choices. The main issue is to describe the dynamics of the voters' mental states taking into account the mental and political environment. What is novel in this paper is that we apply the theory of open quantum systems to social science. The quantum master equation describes the resolution of uncertainty (represented in the form of superposition) to a definite choice.

Nanoscale phase engineering of thermal transport with a Josephson heat modulator

NASA Astrophysics Data System (ADS)

Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

2016-03-01

Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

Heat conduction in one-dimensional aperiodic quantum Ising chains.

PubMed

Li, Wenjuan; Tong, Peiqing

2011-03-01

The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling J{m} between the nearest-neighbor spins takes the two values J{A} and J{B} arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N{α}. By increasing the ratio of couplings, the exponent α can be modulated from α > -1 to α < -1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed.

Enhancing the performance of exchange-only qubits in triple-quantum-dots

NASA Astrophysics Data System (ADS)

Fei, Jianjia; Hung, Jo-Tzu; Koh, Teck Seng; Shim, Yun-Pil; Coppersmith, Susan; Hu, Xuedong; Friesen, Mark

2014-03-01

The exchange-only qubit has several potential advantages for quantum computation: all-electrical control, fast gate operations, and robustness against global magnetic noise. Such a device has recently been implemented in a GaAs triple-quantum-dot. In this talk, we discuss theoretical simulations of the fidelity of pulsed gate operations of the exchange-only qubit, based on a master equation approach. Our model accounts for several different dephasing mechanisms, including hyperfine interactions and charge noise arising from double-occupation errors and fluctuations of the detuning parameter. Our investigations indicate the optimal working regimes and maximum gate fidelities for these devices, in terms of experimentally tunable parameters. This work was supported by the Army Research Office, the National Science Foundation, and the United States Department of Defense. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the US Government. This work was supported by the Army Research Office, the National Science Foundation, and the United States Department of Defense.

Dissipative environment may improve the quantum annealing performances of the ferromagnetic p -spin model

NASA Astrophysics Data System (ADS)

Passarelli, G.; De Filippis, G.; Cataudella, V.; Lucignano, P.

2018-02-01

We investigate the quantum annealing of the ferromagnetic p -spin model in a dissipative environment (p =5 and p =7 ). This model, in the large-p limit, codifies Grover's algorithm for searching in an unsorted database [L. K. Grover, Proceedings of the 28th Annual ACM Symposium on Theory of Computing (ACM, New York, 1996), pp. 212-219]. The dissipative environment is described by a phonon bath in thermal equilibrium at finite temperature. The dynamics is studied in the framework of a Lindblad master equation for the reduced density matrix describing only the spins. Exploiting the symmetries of our model Hamiltonian, we can describe many spins and extrapolate expected trends for large N and p . While at weak system-bath coupling the dissipative environment has detrimental effects on the annealing results, we show that in the intermediate-coupling regime, the phonon bath seems to speed up the annealing at low temperatures. This improvement in the performance is likely not due to thermal fluctuation but rather arises from a correlated spin-bath state and persists even at zero temperature. This result may pave the way to a new scenario in which, by appropriately engineering the system-bath coupling, one may optimize quantum annealing performances below either the purely quantum or the classical limit.

Dynamical stability of the one-dimensional rigid Brownian rotator: the role of the rotator’s spatial size and shape

NASA Astrophysics Data System (ADS)

Jeknić-Dugić, Jasmina; Petrović, Igor; Arsenijević, Momir; Dugić, Miroljub

2018-05-01

We investigate dynamical stability of a single propeller-like shaped molecular cogwheel modelled as the fixed-axis rigid rotator. In the realistic situations, rotation of the finite-size cogwheel is subject to the environmentally-induced Brownian-motion effect that we describe by utilizing the quantum Caldeira-Leggett master equation. Assuming the initially narrow (classical-like) standard deviations for the angle and the angular momentum of the rotator, we investigate the dynamics of the first and second moments depending on the size, i.e. on the number of blades of both the free rotator as well as of the rotator in the external harmonic field. The larger the standard deviations, the less stable (i.e. less predictable) rotation. We detect the absence of the simple and straightforward rules for utilizing the rotator’s stability. Instead, a number of the size-related criteria appear whose combinations may provide the optimal rules for the rotator dynamical stability and possibly control. In the realistic situations, the quantum-mechanical corrections, albeit individually small, may effectively prove non-negligible, and also revealing subtlety of the transition from the quantum to the classical dynamics of the rotator. As to the latter, we detect a strong size-dependence of the transition to the classical dynamics beyond the quantum decoherence process.

Efficient determination of the Markovian time-evolution towards a steady-state of a complex open quantum system

NASA Astrophysics Data System (ADS)

Jonsson, Thorsteinn H.; Manolescu, Andrei; Goan, Hsi-Sheng; Abdullah, Nzar Rauf; Sitek, Anna; Tang, Chi-Shung; Gudmundsson, Vidar

2017-11-01

Master equations are commonly used to describe time evolution of open systems. We introduce a general computationally efficient method for calculating a Markovian solution of the Nakajima-Zwanzig generalized master equation. We do so for a time-dependent transport of interacting electrons through a complex nano scale system in a photon cavity. The central system, described by 120 many-body states in a Fock space, is weakly coupled to the external leads. The efficiency of the approach allows us to place the bias window defined by the external leads high into the many-body spectrum of the cavity photon-dressed states of the central system revealing a cascade of intermediate transitions as the system relaxes to a steady state. The very diverse relaxation times present in the open system, reflecting radiative or non-radiative transitions, require information about the time evolution through many orders of magnitude. In our approach, the generalized master equation is mapped from a many-body Fock space of states to a Liouville space of transitions. We show that this results in a linear equation which is solved exactly through an eigenvalue analysis, which supplies information on the steady state and the time evolution of the system.

Quantum dissipation theory and applications to quantum transport and quantum measurement in mesoscopic systems

NASA Astrophysics Data System (ADS)

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) systems, and its closely related solvation mode transformation of system-bath coupling Hamiltonian in general. The exact QDT of DBO systems is also used to clarify the validity of conventional QDT formulations that involve Markovian approximation. In Chapter 3, we develop three nonequivalent but all complete second-order QDT (CS-QDT) formulations. Two of them are of the conventional prescriptions in terms of time-local dissipation and memory kernel, respectively. The third one is called the correlated driving-dissipation equations of motion (CODDE). This novel CS-QDT combines the merits of the former two for its advantages in both the application and numerical implementation aspects. Also highlighted is the importance of correlated driving-dissipation effects on the dynamics of the reduced system. In Chapter 4, we construct an exact QDT formalism via the calculus on path integrals. The new theory aims at the efficient evaluation of non-Markovian dissipation beyond the weak system-bath interaction regime in the presence of time-dependent external field. By adopting exponential-like expansions for bath correlation function, hierarchical equations of motion formalism and continued fraction Liouville-space Green's function formalism are established. The latter will soon be used together with the Dyson equation technique for an efficient evaluation of non-perturbative reduced density matrix dynamics. The interplay between system-bath interaction strength, non-Markovian property, and the required level of hierarchy is also studied with the aid of simple spin-boson systems, together with the three proposed schemes to truncate the infinite hierarchy. In Chapter 5, we develop a nonperturbative theory of electron transfer (ET) in Debye solvents. The resulting exact and analytical rate expression is constructed on the basis of the aforementioned continued fraction Liouville-space Green's function formalism, together with the Dyson equation technique. Not only does it recover the celebrated Marcus' inversion and Kramers' turnover behaviors, the new theory also shows some distinct quantum solvation effects that can alter the ET mechanism. Moreover, the present theory predicts further for the ET reaction thermodynamics, such as equilibrium Gibbs free-energy and entropy, some interesting solvent-dependent features that are calling for experimental verification. In Chapter 6, we discuss the constructed QDTs, in terms of their unified mathematical structure that supports a linear dynamics space, and thus facilitates their applications to various physical problems. The involving details are exemplified with the CODDE form of QDT. As the linear space is concerned, we identify the Schrodinger versus Heisenberg picture and the forward versus backward propagation of the reduced, dissipative Liouville dynamics. For applications we discuss the reduced linear response theory and the optimal control problems, in which the correlated effects of non-Markovian dissipation and field driving are shown to be important. In Chapter 7, we turn to quantum transport, i.e., electric current through molecular or mesoscopic systems under finite applied voltage. By viewing the nonequilibrium transport setup as a quantum open system, we develop a reduced-density-matrix approach to quantum transport. The resulting current is explicitly expressed in terms of the molecular reduced density matrix by tracing out the degrees of freedom of the electrodes at finite bias and temperature. We propose a conditional quantum master equation theory, which is an extension of the conventional (or unconditional) QDT by tracing out the well-defined bath subsets individually, instead of the entire bath degrees of freedom. Both the current and the noise spectrum can be conveniently analyzed in terms of the conditional reduced density matrix dynamics. By far, the QDT (including the conditional one) has only been exploited in second-order form. A self-consistent Born approximation for the system-electrode coupling is further proposed to recover all existing nonlinear current-voltage behaviors including the nonequilibrium Kondo effect. Transport theory based on the exact QDT formalism will be developed in future. In Chapter 8, we study the quantum measurement of a qubit with a quantum-point-contact detector. On the basis of a unified quantum master equation (a form of QDT), we study the measurement-induced relaxation and dephasing of the qubit. Our treatment pays particular attention on the detailed-balance relation, which is a consequence of properly accounting for the energy exchange between the qubit and detector during the measurement process. We also derive a conditional quantum master equation for quantum measurement in general, and study the readout characteristics of the qubit measurement. Our theory is applicable to the quantum measurement at arbitrary voltage and temperature. A number of remarkable new features are found and highlighted in concern with their possible relevance to future experiments. In Chapter 9, we discuss the further development of QDT, aiming at an efficient evaluation of many-electron systems. This will be carried out by reducing the many-particle (Fermion or Boson) QDT to a single-particle one by exploring, e.g. the Wick's contraction theorem. It also results in a time-dependent density functional theory (TDDFT) for transport through complex large-scale (e.g. molecules) systems. Primary results of the TDDFT-QDT are reported. In Chapter 10, we summary the thesis, and comment and remark on the future work on both the theoretical and application aspects of QDT.

Can We Advance Macroscopic Quantum Systems Outside the Framework of Complex Decoherence Theory?

PubMed Central

Brezinski, Mark E; Rupnick, Maria

2016-01-01

Macroscopic quantum systems (MQS) are macroscopic systems driven by quantum rather than classical mechanics, a long studied area with minimal success till recently. Harnessing the benefits of quantum mechanics on a macroscopic level would revolutionize fields ranging from telecommunication to biology, the latter focused on here for reasons discussed. Contrary to misconceptions, there are no known physical laws that prevent the development of MQS. Instead, they are generally believed universally lost in complex systems from environmental entanglements (decoherence). But we argue success is achievable MQS with decoherence compensation developed, naturally or artificially, from top-down rather current reductionist approaches. This paper advances the MQS field by a complex systems approach to decoherence. First, why complex system decoherence approaches (top-down) are needed is discussed. Specifically, complex adaptive systems (CAS) are not amenable to reductionist models (and their master equations) because of emergent behaviour, approximation failures, not accounting for quantum compensatory mechanisms, ignoring path integrals, and the subentity problem. In addition, since MQS must exist within the context of the classical world, where rapid decoherence and prolonged coherence are both needed. Nature has already demonstrated this for quantum subsystems such as photosynthesis and magnetoreception. Second, we perform a preliminary study that illustrates a top-down approach to potential MQS. In summary, reductionist arguments against MQS are not justifiable. It is more likely they are not easily detectable in large intact classical systems or have been destroyed by reductionist experimental set-ups. This complex systems decoherence approach, using top down investigations, is critical to paradigm shifts in MQS research both in biological and non-biological systems. PMID:29200743

Can We Advance Macroscopic Quantum Systems Outside the Framework of Complex Decoherence Theory?

PubMed

Brezinski, Mark E; Rupnick, Maria

2014-07-01

Macroscopic quantum systems (MQS) are macroscopic systems driven by quantum rather than classical mechanics, a long studied area with minimal success till recently. Harnessing the benefits of quantum mechanics on a macroscopic level would revolutionize fields ranging from telecommunication to biology, the latter focused on here for reasons discussed. Contrary to misconceptions, there are no known physical laws that prevent the development of MQS. Instead, they are generally believed universally lost in complex systems from environmental entanglements (decoherence). But we argue success is achievable MQS with decoherence compensation developed, naturally or artificially, from top-down rather current reductionist approaches. This paper advances the MQS field by a complex systems approach to decoherence. First, why complex system decoherence approaches (top-down) are needed is discussed. Specifically, complex adaptive systems (CAS) are not amenable to reductionist models (and their master equations) because of emergent behaviour, approximation failures, not accounting for quantum compensatory mechanisms, ignoring path integrals, and the subentity problem. In addition, since MQS must exist within the context of the classical world, where rapid decoherence and prolonged coherence are both needed. Nature has already demonstrated this for quantum subsystems such as photosynthesis and magnetoreception. Second, we perform a preliminary study that illustrates a top-down approach to potential MQS. In summary, reductionist arguments against MQS are not justifiable. It is more likely they are not easily detectable in large intact classical systems or have been destroyed by reductionist experimental set-ups. This complex systems decoherence approach, using top down investigations, is critical to paradigm shifts in MQS research both in biological and non-biological systems.

Quantum thermal diode based on two interacting spinlike systems under different excitations.

PubMed

Ordonez-Miranda, Jose; Ezzahri, Younès; Joulain, Karl

2017-02-01

We demonstrate that two interacting spinlike systems characterized by different excitation frequencies and coupled to a thermal bath each, can be used as a quantum thermal diode capable of efficiently rectifying the heat current. This is done by deriving analytical expressions for both the heat current and rectification factor of the diode, based on the solution of a master equation for the density matrix. Higher rectification factors are obtained for lower heat currents, whose magnitude takes their maximum values for a given interaction coupling proportional to the temperature of the hotter thermal bath. It is shown that the rectification ability of the diode increases with the excitation frequencies difference, which drives the asymmetry of the heat current, when the temperatures of the thermal baths are inverted. Furthermore, explicit conditions for the optimization of the rectification factor and heat current are explicitly found.

Fully Quantum Fluctuation Theorems

NASA Astrophysics Data System (ADS)

Åberg, Johan

2018-02-01

Systems that are driven out of thermal equilibrium typically dissipate random quantities of energy on microscopic scales. Crooks fluctuation theorem relates the distribution of these random work costs to the corresponding distribution for the reverse process. By an analysis that explicitly incorporates the energy reservoir that donates the energy and the control system that implements the dynamic, we obtain a quantum generalization of Crooks theorem that not only includes the energy changes in the reservoir but also the full description of its evolution, including coherences. Moreover, this approach opens up the possibility for generalizations of the concept of fluctuation relations. Here, we introduce "conditional" fluctuation relations that are applicable to nonequilibrium systems, as well as approximate fluctuation relations that allow for the analysis of autonomous evolution generated by global time-independent Hamiltonians. We furthermore extend these notions to Markovian master equations, implicitly modeling the influence of the heat bath.

Blocking-state influence on shot noise and conductance in quantum dots

NASA Astrophysics Data System (ADS)

Harabula, M.-C.; Ranjan, V.; Haller, R.; Fülöp, G.; Schönenberger, C.

2018-03-01

Quantum dots (QDs) investigated through electron transport measurements often exhibit varying, state-dependent tunnel couplings to the leads. Under specific conditions, weakly coupled states can result in a strong suppression of the electrical current, and they are correspondingly called blocking states. Using the combination of conductance and shot noise measurements, we investigate blocking states in carbon nanotube (CNT) QDs. We report negative differential conductance and super-Poissonian noise. The enhanced noise is the signature of electron bunching, which originates from random switches between the strongly and weakly conducting states of the QD. Negative differential conductance appears here when the blocking state is an excited state. In this case, at the threshold voltage where the blocking state becomes populated, the current is reduced. Using a master equation approach, we provide numerical simulations reproducing both the conductance and the shot noise pattern observed in our measurements.

Classical mapping for Hubbard operators: Application to the double-Anderson model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Bin; Miller, William H.; Levy, Tal J.

A classical Cartesian mapping for Hubbard operators is developed to describe the nonequilibrium transport of an open quantum system with many electrons. The mapping of the Hubbard operators representing the many-body Hamiltonian is derived by using analogies from classical mappings of boson creation and annihilation operators vis-à-vis a coherent state representation. The approach provides qualitative results for a double quantum dot array (double Anderson impurity model) coupled to fermionic leads for a range of bias voltages, Coulomb couplings, and hopping terms. While the width and height of the conduction peaks show deviations from the master equation approach considered to bemore » accurate in the limit of weak system-leads couplings and high temperatures, the Hubbard mapping captures all transport channels involving transition between many electron states, some of which are not captured by approximate nonequilibrium Green function closures.« less

Full counting statistics and shot noise of cotunneling in quantum dots and single-molecule transistors

NASA Astrophysics Data System (ADS)

Kaasbjerg, Kristen; Belzig, Wolfgang

2015-06-01

We develop a conceptually simple scheme based on a master-equation approach to evaluate the full-counting statistics (FCS) of elastic and inelastic off-resonant tunneling (cotunneling) in quantum dots (QDs) and molecules. We demonstrate the method by showing that it reproduces known results for the FCS and shot noise in the cotunneling regime. For a QD with an excited state, we obtain an analytic expression for the cumulant generating function (CGF) taking into account elastic and inelastic cotunneling. From the CGF we find that the shot noise above the inelastic threshold in the cotunneling regime is inherently super-Poissonian when external relaxation is weak. Furthermore, a complete picture of the shot noise across the different transport regimes is given. In the case where the excited state is a blocking state, strongly enhanced shot noise is predicted both in the resonant and cotunneling regimes.

Correlated Coulomb Drag in Capacitively Coupled Quantum-Dot Structures.

PubMed

Kaasbjerg, Kristen; Jauho, Antti-Pekka

2016-05-13

We study theoretically Coulomb drag in capacitively coupled quantum dots (CQDs)-a bias-driven dot coupled to an unbiased dot where transport is due to Coulomb mediated energy transfer drag. To this end, we introduce a master-equation approach that accounts for higher-order tunneling (cotunneling) processes as well as energy-dependent lead couplings, and identify a mesoscopic Coulomb drag mechanism driven by nonlocal multielectron cotunneling processes. Our theory establishes the conditions for a nonzero drag as well as the direction of the drag current in terms of microscopic system parameters. Interestingly, the direction of the drag current is not determined by the drive current, but by an interplay between the energy-dependent lead couplings. Studying the drag mechanism in a graphene-based CQD heterostructure, we show that the predictions of our theory are consistent with recent experiments on Coulomb drag in CQD systems.

Phase-coherent engineering of electronic heat currents with a Josephson modulator

NASA Astrophysics Data System (ADS)

Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

In this contribution we report the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of electronic thermal currents. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase-engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

The effect of damping on a quantum system containing a Kerr-like medium

NASA Astrophysics Data System (ADS)

Mohamed, A.-B. A.; Sebawe Abdalla, M.; Obada, A.-S. F.

2018-05-01

An analytical description is given for a model which represents the interaction between Su(1,1) and Su(2) quantum systems taking into account Su(1,1)-cavity damping and Kerr medium properties. The analytic solution for the master equation of the density matrix is obtained. The examination of the effects of the damping parameter as well as the Kerr-like medium features is performed. The atomic inversion is discussed where the revivals and collapses phenomenon is realized at the considered period of time. Our study is extended to include the degree of entanglement where the system shows partial entanglement in all cases, however, disentanglement is also observed. The death and rebirth is seen in the system provided one selects the suitable values of the parameters. The correlation function of the system shows non-classical as well as classical behavior.

Geopotential measurements with synchronously linked optical lattice clocks

NASA Astrophysics Data System (ADS)

Takano, Tetsushi; Takamoto, Masao; Ushijima, Ichiro; Ohmae, Noriaki; Akatsuka, Tomoya; Yamaguchi, Atsushi; Kuroishi, Yuki; Munekane, Hiroshi; Miyahara, Basara; Katori, Hidetoshi

2016-10-01

According to Einstein's theory of relativity, the passage of time changes in a gravitational field. On Earth, raising a clock by 1 cm increases its apparent tick rate by 1.1 parts in 1018, allowing chronometric levelling through comparison of optical clocks. Here, we demonstrate such geopotential measurements by determining the height difference of master and slave clocks separated by 15 km with an uncertainty of 5 cm. A subharmonic of the master clock laser is delivered through a telecom fibre to synchronously operate the distant clocks. Clocks operated under such phase coherence reject clock laser noise and facilitate proposals for linking clocks and interferometers. Taken over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be 1,652.9(5.9) × 10-18, consistent with an independent measurement by levelling and gravimetry. Our system demonstrates a building block for an internet of clocks, which may constitute ‘quantum benchmarks’, serving as height references with dynamic responses.

Noisy Spins and the Richardson-Gaudin Model

NASA Astrophysics Data System (ADS)

Rowlands, Daniel A.; Lamacraft, Austen

2018-03-01

We study a system of spins (qubits) coupled to a common noisy environment, each precessing at its own frequency. The correlated noise experienced by the spins implies long-lived correlations that relax only due to the differing frequencies. We use a mapping to a non-Hermitian integrable Richardson-Gaudin model to find the exact spectrum of the quantum master equation in the high-temperature limit and, hence, determine the decay rate. Our solution can be used to evaluate the effect of inhomogeneous splittings on a system of qubits coupled to a common bath.

Master equations and the theory of stochastic path integrals

NASA Astrophysics Data System (ADS)

Weber, Markus F.; Frey, Erwin

2017-04-01

This review provides a pedagogic and self-contained introduction to master equations and to their representation by path integrals. Since the 1930s, master equations have served as a fundamental tool to understand the role of fluctuations in complex biological, chemical, and physical systems. Despite their simple appearance, analyses of master equations most often rely on low-noise approximations such as the Kramers-Moyal or the system size expansion, or require ad-hoc closure schemes for the derivation of low-order moment equations. We focus on numerical and analytical methods going beyond the low-noise limit and provide a unified framework for the study of master equations. After deriving the forward and backward master equations from the Chapman-Kolmogorov equation, we show how the two master equations can be cast into either of four linear partial differential equations (PDEs). Three of these PDEs are discussed in detail. The first PDE governs the time evolution of a generalized probability generating function whose basis depends on the stochastic process under consideration. Spectral methods, WKB approximations, and a variational approach have been proposed for the analysis of the PDE. The second PDE is novel and is obeyed by a distribution that is marginalized over an initial state. It proves useful for the computation of mean extinction times. The third PDE describes the time evolution of a ‘generating functional’, which generalizes the so-called Poisson representation. Subsequently, the solutions of the PDEs are expressed in terms of two path integrals: a ‘forward’ and a ‘backward’ path integral. Combined with inverse transformations, one obtains two distinct path integral representations of the conditional probability distribution solving the master equations. We exemplify both path integrals in analysing elementary chemical reactions. Moreover, we show how a well-known path integral representation of averaged observables can be recovered from them. Upon expanding the forward and the backward path integrals around stationary paths, we then discuss and extend a recent method for the computation of rare event probabilities. Besides, we also derive path integral representations for processes with continuous state spaces whose forward and backward master equations admit Kramers-Moyal expansions. A truncation of the backward expansion at the level of a diffusion approximation recovers a classic path integral representation of the (backward) Fokker-Planck equation. One can rewrite this path integral in terms of an Onsager-Machlup function and, for purely diffusive Brownian motion, it simplifies to the path integral of Wiener. To make this review accessible to a broad community, we have used the language of probability theory rather than quantum (field) theory and do not assume any knowledge of the latter. The probabilistic structures underpinning various technical concepts, such as coherent states, the Doi-shift, and normal-ordered observables, are thereby made explicit.

Master equations and the theory of stochastic path integrals.

PubMed

Weber, Markus F; Frey, Erwin

2017-04-01

This review provides a pedagogic and self-contained introduction to master equations and to their representation by path integrals. Since the 1930s, master equations have served as a fundamental tool to understand the role of fluctuations in complex biological, chemical, and physical systems. Despite their simple appearance, analyses of master equations most often rely on low-noise approximations such as the Kramers-Moyal or the system size expansion, or require ad-hoc closure schemes for the derivation of low-order moment equations. We focus on numerical and analytical methods going beyond the low-noise limit and provide a unified framework for the study of master equations. After deriving the forward and backward master equations from the Chapman-Kolmogorov equation, we show how the two master equations can be cast into either of four linear partial differential equations (PDEs). Three of these PDEs are discussed in detail. The first PDE governs the time evolution of a generalized probability generating function whose basis depends on the stochastic process under consideration. Spectral methods, WKB approximations, and a variational approach have been proposed for the analysis of the PDE. The second PDE is novel and is obeyed by a distribution that is marginalized over an initial state. It proves useful for the computation of mean extinction times. The third PDE describes the time evolution of a 'generating functional', which generalizes the so-called Poisson representation. Subsequently, the solutions of the PDEs are expressed in terms of two path integrals: a 'forward' and a 'backward' path integral. Combined with inverse transformations, one obtains two distinct path integral representations of the conditional probability distribution solving the master equations. We exemplify both path integrals in analysing elementary chemical reactions. Moreover, we show how a well-known path integral representation of averaged observables can be recovered from them. Upon expanding the forward and the backward path integrals around stationary paths, we then discuss and extend a recent method for the computation of rare event probabilities. Besides, we also derive path integral representations for processes with continuous state spaces whose forward and backward master equations admit Kramers-Moyal expansions. A truncation of the backward expansion at the level of a diffusion approximation recovers a classic path integral representation of the (backward) Fokker-Planck equation. One can rewrite this path integral in terms of an Onsager-Machlup function and, for purely diffusive Brownian motion, it simplifies to the path integral of Wiener. To make this review accessible to a broad community, we have used the language of probability theory rather than quantum (field) theory and do not assume any knowledge of the latter. The probabilistic structures underpinning various technical concepts, such as coherent states, the Doi-shift, and normal-ordered observables, are thereby made explicit.

Effects of system-bath coupling on a photosynthetic heat engine: A polaron master-equation approach

NASA Astrophysics Data System (ADS)

Qin, M.; Shen, H. Z.; Zhao, X. L.; Yi, X. X.

2017-07-01

Stimulated by suggestions of quantum effects in energy transport in photosynthesis, the fundamental principles responsible for the near-unit efficiency of the conversion of solar to chemical energy became active again in recent years. Under natural conditions, the formation of stable charge-separation states in bacteria and plant reaction centers is strongly affected by the coupling of electronic degrees of freedom to a wide range of vibrational motions. These inspire and motivate us to explore the effects of the environment on the operation of such complexes. In this paper, we apply the polaron master equation, which offers the possibilities to interpolate between weak and strong system-bath coupling, to study how system-bath couplings affect the exciton-transfer processes in the Photosystem II reaction center described by a quantum heat engine (QHE) model over a wide parameter range. The effects of bath correlation and temperature, together with the combined effects of these factors are also discussed in detail. We interpret these results in terms of noise-assisted transport effect and dynamical localization, which correspond to two mechanisms underpinning the transfer process in photosynthetic complexes: One is resonance energy transfer and the other is the dynamical localization effect captured by the polaron master equation. The effects of system-bath coupling and bath correlation are incorporated in the effective system-bath coupling strength determining whether noise-assisted transport effect or dynamical localization dominates the dynamics and temperature modulates the balance of the two mechanisms. Furthermore, these two mechanisms can be attributed to one physical origin: bath-induced fluctuations. The two mechanisms are manifestations of the dual role played by bath-induced fluctuations depending on the range of parameters. The origin and role of coherence are also discussed. It is the constructive interplay between noise and coherent dynamics, rather than the mere presence or absence of coherence or noise, that is responsible for the optimal heat engine performance. In addition, we find that the effective voltage of QHE exhibits superior robustness against the bath noise as long as the system-bath coupling is not very strong.

Conditional and unconditional Gaussian quantum dynamics

NASA Astrophysics Data System (ADS)

Genoni, Marco G.; Lami, Ludovico; Serafini, Alessio

2016-07-01

This article focuses on the general theory of open quantum systems in the Gaussian regime and explores a number of diverse ramifications and consequences of the theory. We shall first introduce the Gaussian framework in its full generality, including a classification of Gaussian (also known as 'general-dyne') quantum measurements. In doing so, we will give a compact proof for the parametrisation of the most general Gaussian completely positive map, which we believe to be missing in the existing literature. We will then move on to consider the linear coupling with a white noise bath, and derive the diffusion equations that describe the evolution of Gaussian states under such circumstances. Starting from these equations, we outline a constructive method to derive general master equations that apply outside the Gaussian regime. Next, we include the general-dyne monitoring of the environmental degrees of freedom and recover the Riccati equation for the conditional evolution of Gaussian states. Our derivation relies exclusively on the standard quantum mechanical update of the system state, through the evaluation of Gaussian overlaps. The parametrisation of the conditional dynamics we obtain is novel and, at variance with existing alternatives, directly ties in to physical detection schemes. We conclude our study with two examples of conditional dynamics that can be dealt with conveniently through our formalism, demonstrating how monitoring can suppress the noise in optical parametric processes as well as stabilise systems subject to diffusive scattering.

Single-photon absorption by single photosynthetic light-harvesting complexes

NASA Astrophysics Data System (ADS)

Chan, Herman C. H.; Gamel, Omar E.; Fleming, Graham R.; Whaley, K. Birgitta

2018-03-01

We provide a unified theoretical approach to the quantum dynamics of absorption of single photons and subsequent excitonic energy transfer in photosynthetic light-harvesting complexes. Our analysis combines a continuous mode < n > -photon quantum optical master equation for the chromophoric system with the hierarchy of equations of motion describing excitonic dynamics in presence of non-Markovian coupling to vibrations of the chromophores and surrounding protein. We apply the approach to simulation of absorption of single-photon coherent states by pigment-protein complexes containing between one and seven chromophores, and compare with results obtained by excitation using a thermal radiation field. We show that the values of excitation probability obtained under single-photon absorption conditions can be consistently related to bulk absorption cross-sections. Analysis of the timescale and efficiency of single-photon absorption by light-harvesting systems within this full quantum description of pigment-protein dynamics coupled to a quantum radiation field reveals a non-trivial dependence of the excitation probability and the excited state dynamics induced by exciton-phonon coupling during and subsequent to the pulse, on the bandwidth of the incident photon pulse. For bandwidths equal to the spectral bandwidth of Chlorophyll a, our results yield an estimation of an average time of ˜0.09 s for a single chlorophyll chromophore to absorb the energy equivalent of one (single-polarization) photon under irradiation by single-photon states at the intensity of sunlight.

Coupling optical and electrical gating for electronic readout of quantum dot dynamics

NASA Astrophysics Data System (ADS)

Vasudevan, Smitha; Walczak, Kamil; Ghosh, Avik W.

2010-08-01

We explore the coherent transfer of electronic signatures from a strongly correlated, optically gated nanoscale quantum dot to a weakly interacting, electrically backgated microscale channel. In this unique side-coupled “ T ” geometry for transport, we predict a mechanism for detecting Rabi oscillations induced in the dot through quantum, rather than electrostatic means. This detection shows up directly in the dc conductance-voltage spectrum as a field-tunable split in the Fano lineshape arising due to interference between the dipole coupled dot states and the channel continuum. The split is further modified by the Coulomb interactions within the dot that influence the detuning of the Rabi oscillations. Furthermore, time resolving the signal we see clear beats when the Rabi frequencies approach the intrinsic Bohr frequencies in the dot. Capturing these coupled dynamics requires attention to memory effects and quantum interference in the channel as well as many-body effects in the dot. We accomplish this coupling by combining a Fock-space master equation for the dot dynamics with the phase-coherent, non-Markovian time-dependent nonequilibrium Green’s function transport formalism in the channel through a properly evaluated self-energy and a Coulomb integral. The strength of the interactions can further be modulated using a backgate that controls the degree of hybridization and charge polarization at the transistor surface.

Thermoelectric properties of an interacting quantum dot based heat engine

NASA Astrophysics Data System (ADS)

Erdman, Paolo Andrea; Mazza, Francesco; Bosisio, Riccardo; Benenti, Giuliano; Fazio, Rosario; Taddei, Fabio

2017-06-01

We study the thermoelectric properties and heat-to-work conversion performance of an interacting, multilevel quantum dot (QD) weakly coupled to electronic reservoirs. We focus on the sequential tunneling regime. The dynamics of the charge in the QD is studied by means of master equations for the probabilities of occupation. From here we compute the charge and heat currents in the linear response regime. Assuming a generic multiterminal setup, and for low temperatures (quantum limit), we obtain analytical expressions for the transport coefficients which account for the interplay between interactions (charging energy) and level quantization. In the case of systems with two and three terminals we derive formulas for the power factor Q and the figure of merit Z T for a QD-based heat engine, identifying optimal working conditions which maximize output power and efficiency of heat-to-work conversion. Beyond the linear response we concentrate on the two-terminal setup. We first study the thermoelectric nonlinear coefficients assessing the consequences of large temperature and voltage biases, focusing on the breakdown of the Onsager reciprocal relation between thermopower and Peltier coefficient. We then investigate the conditions which optimize the performance of a heat engine, finding that in the quantum limit output power and efficiency at maximum power can almost be simultaneously maximized by choosing appropriate values of electrochemical potential and bias voltage. At last we study how energy level degeneracy can increase the output power.

Spin-lattice relaxation of individual solid-state spins

NASA Astrophysics Data System (ADS)

Norambuena, A.; Muñoz, E.; Dinani, H. T.; Jarmola, A.; Maletinsky, P.; Budker, D.; Maze, J. R.

2018-03-01

Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given to the dynamics of one-phonon processes below 1 K where our results agree with recent experimental findings and analytically describe the temperature and magnetic-field scaling. At higher temperatures, linear and second-order terms in the interaction Hamiltonian are considered and the temperature scaling is discussed for acoustic and quasilocalized phonons when appropriate. Our results, in addition to confirming a T5 temperature dependence of the longitudinal relaxation rate at higher temperatures, in agreement with experimental observations, provide a theoretical background for modeling the spin-lattice relaxation at a wide range of temperatures where different temperature scalings might be expected.

Open quantum systems and error correction

NASA Astrophysics Data System (ADS)

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) that applies to any linear map, in particular maps that are not completely positive (CP). This is a complementary to the second chapter which is published in [Shabani and Lidar, 2007]. In the last chapter 7 before the conclusion, a formulation for evaluating the performance of quantum error correcting codes for a general error model is presented, also published in [Shabani, 2005]. In this formulation, the correlation between errors is quantified by a Hamiltonian description of the noise process. In particular, we consider Calderbank-Shor-Steane codes and observe a better performance in the presence of correlated errors depending on the timing of the error recovery.

Quantum principle of sensing gravitational waves: From the zero-point fluctuations to the cosmological stochastic background of spacetime

NASA Astrophysics Data System (ADS)

Quiñones, Diego A.; Oniga, Teodora; Varcoe, Benjamin T. H.; Wang, Charles H.-T.

2017-08-01

We carry out a theoretical investigation on the collective dynamics of an ensemble of correlated atoms, subject to both vacuum fluctuations of spacetime and stochastic gravitational waves. A general approach is taken with the derivation of a quantum master equation capable of describing arbitrary confined nonrelativistic matter systems in an open quantum gravitational environment. It enables us to relate the spectral function for gravitational waves and the distribution function for quantum gravitational fluctuations and to indeed introduce a new spectral function for the zero-point fluctuations of spacetime. The formulation is applied to two-level identical bosonic atoms in an off-resonant high-Q cavity that effectively inhibits undesirable electromagnetic delays, leading to a gravitational transition mechanism through certain quadrupole moment operators. The overall relaxation rate before reaching equilibrium is found to generally scale collectively with the number N of atoms. However, we are also able to identify certain states of which the decay and excitation rates with stochastic gravitational waves and vacuum spacetime fluctuations amplify more significantly with a factor of N2. Using such favorable states as a means of measuring both conventional stochastic gravitational waves and novel zero-point spacetime fluctuations, we determine the theoretical lower bounds for the respective spectral functions. Finally, we discuss the implications of our findings on future observations of gravitational waves of a wider spectral window than currently accessible. Especially, the possible sensing of the zero-point fluctuations of spacetime could provide an opportunity to generate initial evidence and further guidance of quantum gravity.

A Maxwell-Schrödinger solver for quantum optical few-level systems

NASA Astrophysics Data System (ADS)

Fleischhaker, Robert; Evers, Jörg

2011-03-01

The msprop program presented in this work is capable of solving the Maxwell-Schrödinger equations for one or several laser fields propagating through a medium of quantum optical few-level systems in one spatial dimension and in time. In particular, it allows to numerically treat systems in which a laser field interacts with the medium with both its electric and magnetic component at the same time. The internal dynamics of the few-level system is modeled by a quantum optical master equation which includes coherent processes due to optical transitions driven by the laser fields as well as incoherent processes due to decay and dephasing. The propagation dynamics of the laser fields is treated in slowly varying envelope approximation resulting in a first order wave equation for each laser field envelope function. The program employs an Adams predictor formula second order in time to integrate the quantum optical master equation and a Lax-Wendroff scheme second order in space and time to evolve the wave equations for the fields. The source function in the Lax-Wendroff scheme is specifically adapted to allow taking into account the simultaneous coupling of a laser field to the polarization and the magnetization of the medium. To reduce execution time, a customized data structure is implemented and explained. In three examples the features of the program are demonstrated and the treatment of a system with a phase-dependent cross coupling of the electric and magnetic field component of a laser field is shown. Program summaryProgram title: msprop Catalogue identifier: AEHR_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHR_v1_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.: 507 625 No. of bytes in distributed program, including test data, etc.: 10 698 552 Distribution format: tar.gz Programming language: C (C99 standard), Mathematica, bash script, gnuplot script Computer: Tested on x86 architecture Operating system: Unix/Linux environment RAM: Less than 30 MB Classification: 2.5 External routines: Standard C math library, accompanying bash script uses gnuplot, bc (basic calculator), and convert (ImageMagick) Nature of problem: We consider a system of quantum optical few-level atoms exposed to several near-resonant continuous-wave or pulsed laser fields. The complexity of the problem arises from the combination of the coherent and incoherent time evolution of the atoms and its dependence on the spatially varying fields. In systems with a coupling to the electric and magnetic field component the simultaneous treatment of both field components poses an additional challenge. Studying the system dynamics requires solving the quantum optical master equation coupled to the wave equations governing the spatio-temporal dynamics of the fields [1,2]. Solution method: We numerically integrate the equations of motion using a second order Adams predictor method for the time evolution of the atomic density matrix and a second order Lax-Wendroff scheme for iterating the fields in space [3]. For the Lax-Wendroff scheme, the source function is adapted such that a simultaneous coupling to the polarization and the magnetization of the medium can be taken into account. Restrictions: The evolution of the fields is treated in slowly varying envelope approximation [2] such that variations of the fields in space and time must be on a scale larger than the wavelength and the optical cycle. Propagation is restricted to the forward direction and to one dimension. Concerning the description of the atomic system, only a finite number of basis states can be treated and the laser-driven transitions have to be near-resonant such that the rotating-wave approximation can be applied [2]. Unusual features: The program allows the dipole interaction of both the electric and the magnetic component of a laser field to be taken into account at the same time. Thus, a system with a phase-dependent cross coupling of electric and magnetic field component can be treated (see Section 4.2 and [4]). Concerning the implementation of the data structure, it has been optimized for faster memory access. Compared to using standard memory allocation methods, shorter run times are achieved (see Section 3.2). Additional comments: Three examples are given. They each include a readme file, a Mathematica notebook to generate the C-code form of the quantum optical master equation, a parameter file, a bash script which runs the program and converts the numerical data into a movie, two gnuplot scripts, and all files that are produced by running the bash script. Running time: For the first two examples the running time is less than a minute, the third example takes about 12 minutes. On a Pentium 4 (3 GHz) system, a rough estimate can be made with a value of 1 second per million grid points and per field variable.

The English Revision of The Blegdamsvej Faust

NASA Astrophysics Data System (ADS)

Keck, Karen

2007-03-01

At the 1932 meeting of quantum physicists at Niels Bohr's Copenhagen Institute, participants staged an updated version of Goethe's Faust with Pauli tempting Ehrenfest to accept a chargeless, massless particle, then called the neutron. The most widely read translation of the anonymous Faust: Eine Historie appears in George Gamow's Thirty Years that Shook Physics; his second wife, Barbara, translated the text. Her work masterfully communicates the parallels between Goethe's original and the anonymous parody, but it also rearranges and adds to the parody to strengthen those similarities and to reflect George Gamow's views. The changes emphasize the international and cooperative aspects of physics.

Towards self-correcting quantum memories

NASA Astrophysics Data System (ADS)

Michnicki, Kamil

This thesis presents a model of self-correcting quantum memories where quantum states are encoded using topological stabilizer codes and error correction is done using local measurements and local dynamics. Quantum noise poses a practical barrier to developing quantum memories. This thesis explores two types of models for suppressing noise. One model suppresses thermalizing noise energetically by engineering a Hamiltonian with a high energy barrier between code states. Thermalizing dynamics are modeled phenomenologically as a Markovian quantum master equation with only local generators. The second model suppresses stochastic noise with a cellular automaton that performs error correction using syndrome measurements and a local update rule. Several ways of visualizing and thinking about stabilizer codes are presented in order to design ones that have a high energy barrier: the non-local Ising model, the quasi-particle graph and the theory of welded stabilizer codes. I develop the theory of welded stabilizer codes and use it to construct a code with the highest known energy barrier in 3-d for spin Hamiltonians: the welded solid code. Although the welded solid code is not fully self correcting, it has some self correcting properties. It has an increased memory lifetime for an increased system size up to a temperature dependent maximum. One strategy for increasing the energy barrier is by mediating an interaction with an external system. I prove a no-go theorem for a class of Hamiltonians where the interaction terms are local, of bounded strength and commute with the stabilizer group. Under these conditions the energy barrier can only be increased by a multiplicative constant. I develop cellular automaton to do error correction on a state encoded using the toric code. The numerical evidence indicates that while there is no threshold, the model can extend the memory lifetime significantly. While of less theoretical importance, this could be practical for real implementations of quantum memories. Numerical evidence also suggests that the cellular automaton could function as a decoder with a soft threshold.

The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems

NASA Astrophysics Data System (ADS)

Benatov, Latchezar Latchezarov

This thesis comprises two separate but related studies, dealing with two strongly interacting nanoscale systems on the border between the quantum and classical domains. In Part 1, we use a Born-Markov approximated master equation approach to study the symmetrized-in-frequency current noise spectrum and the oscillator steady state of a nanoelectromechanical system where a nanoscale resonator is coupled linearly via its momentum to a quantum point contact (QPC). Our current noise spectra exhibit clear signatures of the quantum correlations between the QPC current and the back-action force on the oscillator at a value of the relative tunneling phase where such correlations are expected to be maximized. We also show that the steady state of the oscillator obeys a classical Fokker-Planck equation, but can experience thermomechanical noise squeezing in the presence of a momentum-coupled detector bath and a position-coupled environmental bath. Besides, the full master equation clearly shows that half of the detector back-action is correlated with electron tunneling, indicating a departure from the model of the detector as an effective bath and suggesting that a future calculation valid at lower bias voltage, stronger tunneling and/or stronger coupling might reveal interesting quantum effects in the oscillator dynamics. In the second part of the thesis, we study the subsystem dynamics and thermalization of an oscillator-spin star model, where a nanomechanical resonator is coupled to a few two-level systems (TLS's). We use a fourth-order Runge-Kutta numerical algorithm to integrate the Schrodinger equation for the system and obtain our results. We find that the oscillator reaches a Boltzmann steady state when the TLS bath is initially in a thermal state at a temperature higher than the oscillator phonon energy. This occurs in both chaotic and integrable systems, and despite the small number of spins (only six) and the lack of couplings between them. At the same time, pure initial states do not thermalize well in our system, indicating that mixed state thermalization stems from the thermal nature of the initial bath state. Under the influence of a thermal TLS bath, oscillator Fock states decay in an approximately exponential manner, but there is also a concave-down trend at very early times, possibly indicative of Gaussian decay. In the case of initial Fock state superpositions, the diagonal density matrix element behaves very similarly to single initial Fock states, while the off-diagonal matrix element decays sinusoidally with an exponentially decreasing amplitude. The off-diagonal decay time is much smaller then the diagonal one, indicating that superposition states decohere much faster than they decay. Both decay times decrease with increasing Fock state number, but more slowly than the 1/n dependence seen in the presence of an external ohmic bath.

Multi-rate DPSK optical transceivers for free-space applications

NASA Astrophysics Data System (ADS)

Caplan, D. O.; Carney, J. J.; Fitzgerald, J. J.; Gaschits, I.; Kaminsky, R.; Lund, G.; Hamilton, S. A.; Magliocco, R. J.; Murphy, R. J.; Rao, H. G.; Spellmeyer, N. W.; Wang, J. P.

2014-03-01

We describe a flexible high-sensitivity laser communication transceiver design that can significantly benefit performance and cost of NASA's satellite-based Laser Communications Relay Demonstration. Optical communications using differential phase shift keying, widely deployed for use in long-haul fiber-optic networks, is well known for its superior sensitivity and link performance over on-off keying, while maintaining a relatively straightforward design. However, unlike fiber-optic links, free-space applications often require operation over a wide dynamic range of power due to variations in link distance and channel conditions, which can include rapid kHz-class fading when operating through the turbulent atmosphere. Here we discuss the implementation of a robust, near-quantum-limited multi-rate DPSK transceiver, co-located transmitter and receiver subsystems that can operate efficiently over the highly-variable free-space channel. Key performance features will be presented on the master oscillator power amplifier (MOPA) based TX, including a wavelength-stabilized master laser, high-extinction-ratio burst-mode modulator, and 0.5 W single polarization power amplifier, as well as low-noise optically preamplified DSPK receiver and built-in test capabilities.

Non-Markovian electron dynamics in nanostructures coupled to dissipative contacts

NASA Astrophysics Data System (ADS)

Novakovic, B.; Knezevic, I.

2013-02-01

In quasiballistic semiconductor nanostructures, carrier exchange between the active region and dissipative contacts is the mechanism that governs relaxation. In this paper, we present a theoretical treatment of transient quantum transport in quasiballistic semiconductor nanostructures, which is based on the open system theory and valid on timescales much longer than the characteristic relaxation time in the contacts. The approach relies on a model interaction between the current-limiting active region and the contacts, given in the scattering-state basis. We derive a non-Markovian master equation for the irreversible evolution of the active region's many-body statistical operator by coarse-graining the exact dynamical map over the contact relaxation time. In order to obtain the response quantities of a nanostructure under bias, such as the potential and the charge and current densities, the non-Markovian master equation must be solved numerically together with the Schr\\"{o}dinger, Poisson, and continuity equations. We discuss how to numerically solve this coupled system of equations and illustrate the approach on the example of a silicon nin diode.

Stochastic-master-equation analysis of optimized three-qubit nondemolition parity measurements

NASA Astrophysics Data System (ADS)

Tornberg, L.; Barzanjeh, Sh.; DiVincenzo, David P.

2014-03-01

We analyzea direct parity measurement of the state of three superconducting qubits in circuit quantum electrodynamics. The parity is inferred from a homodyne measurement of the reflected and transmitted microwave radiation, and the measurement is direct in the sense that the parity is measured without the need for any quantum circuit operations or for ancilla qubits. Qubits are coupled to two resonant-cavity modes, allowing the steady state of the emitted radiation to satisfy the necessary conditions to act as a pointer state for the parity. However, the transient dynamics violates these conditions, and we analyze this detrimental effect and show that it can be overcome in the limit of a weak measurement signal. Our analysis shows that, with a moderate degree of postselection, it is possible to achieve postmeasurement states with fidelity of order 95%. We believe that this type of measurement could serve as a benchmark for future error correction protocols in a scalable architecture.

Entanglement dynamics in random media

NASA Astrophysics Data System (ADS)

Menezes, G.; Svaiter, N. F.; Zarro, C. A. D.

2017-12-01

We study how the entanglement dynamics between two-level atoms is impacted by random fluctuations of the light cone. In our model the two-atom system is envisaged as an open system coupled with an electromagnetic field in the vacuum state. We employ the quantum master equation in the Born-Markov approximation in order to describe the completely positive time evolution of the atomic system. We restrict our investigations to the situation in which the atoms are coupled individually to two spatially separated cavities, one of which displays the emergence of light-cone fluctuations. In such a disordered cavity, we assume that the coefficients of the Klein-Gordon equation are random functions of the spatial coordinates. The disordered medium is modeled by a centered, stationary, and Gaussian process. We demonstrate that disorder has the effect of slowing down the entanglement decay. We conjecture that in a strong-disorder environment the mean life of entangled states can be enhanced in such a way as to almost completely suppress quantum nonlocal decoherence.

Parameter estimation by decoherence in the double-slit experiment

NASA Astrophysics Data System (ADS)

Matsumura, Akira; Ikeda, Taishi; Kukita, Shingo

2018-06-01

We discuss a parameter estimation problem using quantum decoherence in the double-slit interferometer. We consider a particle coupled to a massive scalar field after the particle passing through the double slit and solve the dynamics non-perturbatively for the coupling by the WKB approximation. This allows us to analyze the estimation problem which cannot be treated by master equation used in the research of quantum probe. In this model, the scalar field reduces the interference fringes of the particle and the fringe pattern depends on the field mass and coupling. To evaluate the contrast and the estimation precision obtained from the pattern, we introduce the interferometric visibility and the Fisher information matrix of the field mass and coupling. For the fringe pattern observed on the distant screen, we derive a simple relation between the visibility and the Fisher matrix. Also, focusing on the estimation precision of the mass, we find that the Fisher information characterizes the wave-particle duality in the double-slit interferometer.

Dissipative preparation of squeezed states with ultracold atomic gases

NASA Astrophysics Data System (ADS)

Watanabe, Gentaro; Caballar, Roland Cristopher F.; Diehl, Sebastian; Mäkelä, Harri; Oberthaler, Markus

2014-05-01

We present a dissipative quantum state preparation scheme for the creation of phase- and number-squeezed states. It utilizes ultracold atoms in a double-well configuration immersed in a background BEC acting as a dissipative quantum reservoir. We derive a master equation starting from microscopic physics, and show that squeezing develops on a time scale proportional to 1 / N , where N is the number of particles in the double well. This scaling, caused by bosonic enhancement, allows us to make the time scale for the creation of squeezed states very short. Effects of the dephasing which limits the lifetime of the squeezed states can be avoided by stroboscopically switching the driving off and on. We show that this approach leads to robust stationary squeezed states. We also provide the necessary ingredients for a potential experimental implementation. NRF (No. 2012R1A1A2008028), MPS, Korea MEST, FWF (No. F4006-N16), Alfred Kordelin Foundation, Magnus Ehrnrooth Foundation, Emil Aaltonen Foundation, Academy of Finland (No. 251748).

Molecular origin of differences in hole and electron mobility in amorphous Alq3--a multiscale simulation study.

PubMed

Fuchs, Andreas; Steinbrecher, Thomas; Mommer, Mario S; Nagata, Yuki; Elstner, Marcus; Lennartz, Christian

2012-03-28

In order to determine the molecular origin of the difference in electron and hole mobilities of amorphous thin films of Alq(3) (meridional Alq(3) (tris(8-hydroxyquinoline) aluminium)) we performed multiscale simulations covering quantum mechanics, molecular mechanics and lattice models. The study includes realistic disordered morphologies, polarized site energies to describe diagonal disorder, quantum chemically calculated transfer integrals for the off-diagonal disorder, inner sphere reorganization energies and an approximative scheme for outer sphere reorganization energies. Intermolecular transfer rates were calculated via Marcus-theory and mobilities were simulated via kinetic Monte Carlo simulations and by a Master Equation approach. The difference in electron and hole mobility originates from the different localization of charge density in the radical anion (more delocalized) compared to the radical cation (more confined). This results in higher diagonal disorder for holes and less favourable overlap properties for the hole transfer integrals leading to an overall higher electron mobility.

Dissipative preparation of steady Greenberger-Horne-Zeilinger states for Rydberg atoms with quantum Zeno dynamics

NASA Astrophysics Data System (ADS)

Shao, X. Q.; Wu, J. H.; Yi, X. X.; Long, Gui-Lu

2017-12-01

Inspired by a recent work [F. Reiter, D. Reeb, and A. S. Sørensen, Phys. Rev. Lett. 117, 040501 (2016), 10.1103/PhysRevLett.117.040501], we present a simplified proposal for dissipatively preparing a Greenberger-Horne-Zeilinger (GHZ) state of three Rydberg atoms in a cavity. The Z pumping is implemented under the action of the spontaneous emission of Λ -type atoms and the quantum Zeno dynamics induced by strong continuous coupling. In the meantime, a dissipative Rydberg pumping breaks up the stability of the state | GHZ+〉 in the process of Z pumping, making | GHZ-〉 the unique steady state of the system. Compared with the former scheme, the number of driving fields acting on atoms is greatly reduced and only a single-mode cavity is required. The numerical simulation of the full master equation reveals that a high fidelity ˜98 % can be obtained with the currently achievable parameters in the Rydberg-atom-cavity system.

Dissipation and decoherence in nanodevices: a generalized Fermi's golden rule

NASA Astrophysics Data System (ADS)

Taj, D.; Iotti, R. C.; Rossi, F.

2009-06-01

We shall revisit the conventional adiabatic or Markov approximation, which—in contrast to the semiclassical case—does not preserve the positive-definite character of the corresponding density matrix, thus leading to highly non-physical results. To overcome this serious limitation, originally pointed out and partially solved by Davies and co-workers almost three decades ago, we shall propose an alternative more general adiabatic procedure, which (i) is physically justified under the same validity restrictions of the conventional Markov approach, (ii) in the semiclassical limit reduces to the standard Fermi's golden rule and (iii) describes a genuine Lindblad evolution, thus providing a reliable/robust treatment of energy-dissipation and dephasing processes in electronic quantum devices. Unlike standard master-equation formulations, the dependence of our approximation on the specific choice of the subsystem (that includes the common partial trace reduction) does not threaten positivity, and quantum scattering rates are well defined even in the case the subsystem is infinitely extended/has a continuous spectrum.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akdoğan, Ender, E-mail: ender.akdogan@tpe.gov.tr; Çiftçi, Muharrem, E-mail: muharrem-ciftci@windowslive.com

This article is based on the master thesis [4] related to our invention which was published in World Intellectual Property Organization (WO/2011/048506) as a microwave water heater. In the project, a prototype was produced to use microwave in industrial heating. In order to produce the prototype, the most appropriate material kind for microwave-water experiments was determined by a new energy loss rate calculation technique. This new energy loss calculation is a determinative factor for material permeability at microwave frequency band (1-100 GHz). This experimental series aim to investigate the rationality of using microwave in heating industry. Theoretically, heating water by microwavemore » (with steady frequency 2.45 GHz) is analyzed from sub-molecular to Classical Mechanic results of heating. In the study, we examined Quantum Mechanical base of heating water by microwave experiments. As a result, we derived a Semi-Quantum Mechanical equation for microwave-water interactions and thus, Wien displacement law can be derived to verify experimental observations by this equation.« less

Photon-induced tunability of the thermospin current in a Rashba ring

NASA Astrophysics Data System (ADS)

Abdullah, Nzar Rauf; Arnold, Thorsten; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

2018-04-01

The goal of this work is to show how the thermospin polarization current in a quantum ring changes in the presence of Rashba spin-orbit coupling and a quantized single photon mode of a cavity the ring is placed in. Employing the reduced density operator and a general master equation formalism, we find that both the Rashba interaction and the photon field can significantly modulate the spin polarization and the thermospin polarization current. Tuning the Rashba coupling constant, degenerate energy levels are formed corresponding to the Aharonov-Casher destructive phase interference in the quantum ring system. Our analysis indicates that the maximum spin polarization can be observed at the points of degenerate energy levels due to spin accumulation in the system without the photon field. The thermospin current is thus suppressed. In the presence of the cavity, the photon field leads to an additional kinetic momentum of the electron. As a result the spin polarization can be enhanced by the photon field.

Emission lineshapes of the B850 band of light-harvesting 2 (LH2) complex in purple bacteria: a second order time-nonlocal quantum master equation approach.

PubMed

Kumar, Praveen; Jang, Seogjoo

2013-04-07

The emission lineshape of the B850 band in the light harvesting complex 2 of purple bacteria is calculated by extending the approach of 2nd order time-nonlocal quantum master equation [S. Jang and R. J. Silbey, J. Chem. Phys. 118, 9312 (2003)]. The initial condition for the emission process corresponds to the stationary excited state density where exciton states are entangled with the bath modes in equilibrium. This exciton-bath coupling, which is not diagonal in either site excitation or exciton basis, results in a new inhomogeneous term that is absent in the expression for the absorption lineshape. Careful treatment of all the 2nd order terms are made, and explicit expressions are derived for both full 2nd order lineshape expression and the one based on secular approximation that neglects off-diagonal components in the exciton basis. Numerical results are presented for a few representative cases of disorder and temperature. Comparison of emission line shape with the absorption line shape is also made. It is shown that the inhomogeneous term coming from the entanglement of the system and bath degrees of freedom makes significant contributions to the lineshape. It is also found that the perturbative nature of the theory can result in negative portion of lineshape in some situations, which can be removed significantly by inclusion of the inhomogeneous term and completely by using the secular approximation. Comparison of the emission and absorption lineshapes at different temperatures demonstrates the role of thermal population of different exciton states and exciton-phonon couplings.

Feedback-induced bistability of an optically levitated nanoparticle: A Fokker-Planck treatment

NASA Astrophysics Data System (ADS)

Ge, Wenchao; Rodenburg, Brandon; Bhattacharya, M.

2016-08-01

Optically levitated nanoparticles have recently emerged as versatile platforms for investigating macroscopic quantum mechanics and enabling ultrasensitive metrology. In this paper we theoretically consider two damping regimes of an optically levitated nanoparticle cooled by cavityless parametric feedback. Our treatment is based on a generalized Fokker-Planck equation derived from the quantum master equation presented recently and shown to agree very well with experiment [B. Rodenburg, L. P. Neukirch, A. N. Vamivakas, and M. Bhattacharya, Quantum model of cooling and force sensing with an optically trapped nanoparticle, Optica 3, 318 (2016), 10.1364/OPTICA.3.000318]. For low damping, we find that the resulting Wigner function yields the single-peaked oscillator position distribution and recovers the appropriate energy distribution derived earlier using a classical theory and verified experimentally [J. Gieseler, R. Quidant, C. Dellago, and L. Novotny, Dynamic relaxation of a levitated nanoparticle from a non-equilibrium steady state, Nat. Nano. 9, 358 (2014), 10.1038/nnano.2014.40]. For high damping, in contrast, we predict a double-peaked position distribution, which we trace to an underlying bistability induced by feedback. Unlike in cavity-based optomechanics, stochastic processes play a major role in determining the bistable behavior. To support our conclusions, we present analytical expressions as well as numerical simulations using the truncated Wigner function approach. Our work opens up the prospect of developing bistability-based devices, characterization of phase-space dynamics, and investigation of the quantum-classical transition using levitated nanoparticles.

Fock space, symbolic algebra, and analytical solutions for small stochastic systems.

PubMed

Santos, Fernando A N; Gadêlha, Hermes; Gaffney, Eamonn A

2015-12-01

Randomness is ubiquitous in nature. From single-molecule biochemical reactions to macroscale biological systems, stochasticity permeates individual interactions and often regulates emergent properties of the system. While such systems are regularly studied from a modeling viewpoint using stochastic simulation algorithms, numerous potential analytical tools can be inherited from statistical and quantum physics, replacing randomness due to quantum fluctuations with low-copy-number stochasticity. Nevertheless, classical studies remained limited to the abstract level, demonstrating a more general applicability and equivalence between systems in physics and biology rather than exploiting the physics tools to study biological systems. Here the Fock space representation, used in quantum mechanics, is combined with the symbolic algebra of creation and annihilation operators to consider explicit solutions for the chemical master equations describing small, well-mixed, biochemical, or biological systems. This is illustrated with an exact solution for a Michaelis-Menten single enzyme interacting with limited substrate, including a consideration of very short time scales, which emphasizes when stiffness is present even for small copy numbers. Furthermore, we present a general matrix representation for Michaelis-Menten kinetics with an arbitrary number of enzymes and substrates that, following diagonalization, leads to the solution of this ubiquitous, nonlinear enzyme kinetics problem. For this, a flexible symbolic maple code is provided, demonstrating the prospective advantages of this framework compared to stochastic simulation algorithms. This further highlights the possibilities for analytically based studies of stochastic systems in biology and chemistry using tools from theoretical quantum physics.

Transverse correlation in entangled photons and light-matter interaction

NASA Astrophysics Data System (ADS)

Wen, Jianming

In recent years, quantum entanglement has attracted much attention, because its unique properties provide potential applications, which could not be achieved using conventional techniques, such as quantum computing, quantum imaging and lithography. To realize these advancements, one has to obtain an entanglement-generation source, thoroughly master its physical properties, and fully understand the light-matter interaction. This dissertation is an attempt to address such issues as stated above. Conventionally, paired photons are created from spontaneous parametric down-conversion (SPDC). It is known that the transverse correlation in biphotons may improve the visibility and resolution in quantum imaging and lithography. In this thesis, we described an alternative biphoton source---Raman-EIT (electromagnetically induced transparency) generator, and emphasize on its geometrical and optical properties. We found that to utilize the transverse effects in paired Stokes-anti-Stokes, it is necessary to make the product of the EIT window times the group delay much greater than unity. To gain further insight into quantum imaging and lithography, we studied the transverse correlation in triphoton entanglement theoretically. We found that in the two-image process, the quality of images is determined by the optical path-lengths, even though the Gaussian thin lens equations are satisfied. The ghost interference-diffraction patterns of double slits show one more fold interference, which is essentially different from the biphoton case. Klyshko's advanced-wave model is still applicable, with some modifications. We also generalized the transverse correlation to the case of multi-photon entangled states. To implement quantum computing, one key element is quantum memory. In this thesis, we have theoretically explored the feasibility of such a memory by using nonclassical SPDC light in an EIT system at the single-photon level. We found that both the quantum coherence of SPDC and atomic coherence of EIT can survive after interacting within a vapor cell. Due to the inherent mismatch of magnitude between the spectral bandwidth of SPDC and the very narrow transmission width of EIT, the coincidence counts of the two-photon interference is reduced to one pair per second, which is barely doable in the current experimental situation.

Instability of political preferences and the role of mass media: a dynamical representation in a quantum framework.

PubMed

Khrennikova, Polina; Haven, Emmanuel

2016-01-13

We search to devise a new paradigm borrowed from concepts and mathematical tools of quantum physics, to model the decision-making process of the US electorate. The statistical data of the election outcomes in the period between 2008 and 2014 is analysed, in order to explore in more depth the emergence of the so-called divided government. There is an increasing urge in the political literature which indicates that preference reversal (strictly speaking the violation of the transitivity axiom) is a consequence of the so-called non-separability phenomenon (i.e. a strong interrelation of choices). In the political science literature, non-separable behaviour is characterized by a conditioning of decisions on the outcomes of some issues of interest. An additional source of preference reversal is ascribed to the time dynamics of the voters' cognitive states, in the context of new upcoming political information. As we discuss in this paper, the primary source of political information can be attributed to the mass media. In order to shed more light on the phenomenon of preference reversal among the US electorate, we accommodate the obtained statistical data in a classical probabilistic (Kolmogorovian) scheme. Based on the obtained results, we attribute the strong ties between the voters non-separable decisions that cannot be explained by conditioning with the Bayes scheme, to the quantum phenomenon of entanglement. Second, we compute the degree of interference of voters' belief states with the aid of the quantum analogue of the formula of total probability. Lastly, a model, based on the quantum master equation, to incorporate the impact of the mass media bath is proposed. © 2015 The Author(s).

Bounds on quantum collapse models from matter-wave interferometry: calculational details

NASA Astrophysics Data System (ADS)

Toroš, Marko; Bassi, Angelo

2018-03-01

We present a simple derivation of the interference pattern in matter-wave interferometry predicted by a class of quantum master equations. We apply the obtained formulae to the following collapse models: the Ghirardi-Rimini-Weber (GRW) model, the continuous spontaneous localization (CSL) model together with its dissipative (dCSL) and non-Markovian generalizations (cCSL), the quantum mechanics with universal position localization (QMUPL), and the Diósi-Penrose (DP) model. We discuss the separability of the dynamics of the collapse models along the three spatial directions, the validity of the paraxial approximation, and the amplification mechanism. We obtain analytical expressions both in the far field and near field limits. These results agree with those already derived in the Wigner function formalism. We compare the theoretical predictions with the experimental data from two recent matter-wave experiments: the 2012 far-field experiment of Juffmann T et al (2012 Nat. Nanotechnol. 7 297-300) and the 2013 Kapitza-Dirac-Talbot-Lau (KDTL) near-field experiment of Eibenberger et al (2013 Phys. Chem. Chem. Phys. 15 14696-700). We show the region of the parameter space for each collapse model that is excluded by these experiments. We show that matter-wave experiments provide model-insensitive bounds that are valid for a wide family of dissipative and non-Markovian generalizations.

Approach to equilibrium of a quantum system and generalization of the Montroll-Shuler equation for vibrational relaxation of a molecular oscillator

NASA Astrophysics Data System (ADS)

Kenkre, V. M.; Chase, M.

2017-08-01

The approach to equilibrium of a quantum mechanical system in interaction with a bath is studied from a practical as well as a conceptual point of view. Explicit memory functions are derived for given models of bath couplings. If the system is a harmonic oscillator representing a molecule in interaction with a reservoir, the generalized master equation derived becomes an extension into the coherent domain of the well-known Montroll-Shuler equation for vibrational relaxation and unimolecular dissociation. A generalization of the Bethe-Teller result regarding energy relaxation is found for short times. The theory has obvious applications to relaxation dynamics at ultra-short times as in observations on the femtosecond time scale and to the investigation of quantum coherence at those short times. While vibrational relaxation in chemical physics is a primary target of the study, another system of interest in condensed matter physics, an electron or hole in a lattice subjected to a strong DC electric field that gives rise to well-known Wannier-Stark ladders, is naturally addressed with the theory. Specific system-bath interactions are explored to obtain explicit details of the dynamics. General phenomenological descriptions of the reservoir are considered rather than specific microscopic realizations.

Exciton size and quantum transport in nanoplatelets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelzer, Kenley M., E-mail: kpelzer@anl.gov; Gray, Stephen K.; Darling, Seth B.

2015-12-14

Two-dimensional nanoplatelets (NPLs) are an exciting class of materials with promising optical and energy transport properties. The possibility of efficient energy transport between nanoplatelets raises questions regarding the nature of energy transfer in these thin, laterally extended systems. A challenge in understanding exciton transport is the uncertainty regarding the size of the exciton. Depending on the material and defects in the nanoplatelet, an exciton could plausibly extend over an entire plate or localize to a small region. The variation in possible exciton sizes raises the question how exciton size impacts the efficiency of transport between nanoplatelet structures. Here, we exploremore » this issue using a quantum master equation approach. This method goes beyond the assumptions of Förster theory to allow for quantum mechanical effects that could increase energy transfer efficiency. The model is extremely flexible in describing different systems, allowing us to test the effect of varying the spatial extent of the exciton. We first discuss qualitative aspects of the relationship between exciton size and transport and then conduct simulations of exciton transport between NPLs for a range of exciton sizes and environmental conditions. Our results reveal that exciton size has a strong effect on energy transfer efficiency and suggest that manipulation of exciton size may be useful in designing NPLs for energy transport.« less

Exciton size and quantum transport in nanoplatelets.

PubMed

Pelzer, Kenley M; Darling, Seth B; Gray, Stephen K; Schaller, Richard D

2015-12-14

Two-dimensional nanoplatelets (NPLs) are an exciting class of materials with promising optical and energy transport properties. The possibility of efficient energy transport between nanoplatelets raises questions regarding the nature of energy transfer in these thin, laterally extended systems. A challenge in understanding exciton transport is the uncertainty regarding the size of the exciton. Depending on the material and defects in the nanoplatelet, an exciton could plausibly extend over an entire plate or localize to a small region. The variation in possible exciton sizes raises the question how exciton size impacts the efficiency of transport between nanoplatelet structures. Here, we explore this issue using a quantum master equation approach. This method goes beyond the assumptions of Förster theory to allow for quantum mechanical effects that could increase energy transfer efficiency. The model is extremely flexible in describing different systems, allowing us to test the effect of varying the spatial extent of the exciton. We first discuss qualitative aspects of the relationship between exciton size and transport and then conduct simulations of exciton transport between NPLs for a range of exciton sizes and environmental conditions. Our results reveal that exciton size has a strong effect on energy transfer efficiency and suggest that manipulation of exciton size may be useful in designing NPLs for energy transport.

Using the Chebychev expansion in quantum transport calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popescu, Bogdan; Rahman, Hasan; Kleinekathöfer, Ulrich, E-mail: u.kleinekathoefer@jacobs-university.de

2015-04-21

Irradiation by laser pulses and a fluctuating surrounding liquid environment can, for example, lead to time-dependent effects in the transport through molecular junctions. From the theoretical point of view, time-dependent theories of quantum transport are still challenging. In one of these existing transport theories, the energy-dependent coupling between molecule and leads is decomposed into Lorentzian functions. This trick has successfully been combined with quantum master approaches, hierarchical formalisms, and non-equilibrium Green’s functions. The drawback of this approach is, however, its serious limitation to certain forms of the molecule-lead coupling and to higher temperatures. Tian and Chen [J. Chem. Phys. 137,more » 204114 (2012)] recently employed a Chebychev expansion to circumvent some of these latter problems. Here, we report on a similar approach also based on the Chebychev expansion but leading to a different set of coupled differential equations using the fact that a derivative of a zeroth-order Bessel function can again be given in terms of Bessel functions. Test calculations show the excellent numerical accuracy and stability of the presented formalism. The time span for which this Chebychev expansion scheme is valid without any restrictions on the form of the spectral density or temperature can be determined a priori.« less

Coherent or hopping like energy transfer in the chlorosome ?

NASA Astrophysics Data System (ADS)

Nalbach, Peter

2014-08-01

Chlorosomes, as part of the light-harvesting system of green bacteria, are the largest and most efficient antennae systems in nature. We have studied energy transfer dynamics in the chlorosome in a simplified toy model employing a master equation. Dephasing and relaxation due to environmental fluctuations are included by Lindblad dephasing and Redfield thermalization rates. We find at room temperature three separate time scales, i.e. 25 fs, 250 fs and 2.5 ps and determine the according energy pathways through the hierarchical structure in the chlorosome. Quantum coherence lives up to 150 fs at which time the energy is spread over roughly 12 pigments in our model.

Research summer camp in photonics

NASA Astrophysics Data System (ADS)

Buyanovskaya, Elizaveta; Melnik, Maksim; Egorov, Vladimir; Gleim, Artur; Lukishova, Svetlana; Kozlov, Sergei; Zhang, Xi-Cheng

2017-08-01

ITMO University and the University of Rochester became close partners several years ago. One of the first outcomes of this mutually beneficial partnership was the creation of International Institute of Photonics and Optical Information Technologies led by Prof. Sergei Kozlov and Prof. Xi-Cheng Zhang. Universities have created a double Masters-degree program in optics in 2014, and several ITMO students have been awarded degrees from Rochester. At the same time ITMO University organizes Summer Research camp in Photonics for University of Rochester students. Students spent two weeks in the Northern Capital of Russia learning about the emerging practical applications of femtosecond optics, terahertz biomedicine and quantum information technologies.

Correlated sequential tunneling through a double barrier for interacting one-dimensional electrons

NASA Astrophysics Data System (ADS)

Thorwart, M.; Egger, R.; Grifoni, M.

2005-07-01

The problem of resonant tunneling through a quantum dot weakly coupled to spinless Tomonaga-Luttinger liquids has been studied. We compute the linear conductance due to sequential tunneling processes upon employing a master equation approach. Besides the previously used lowest-order golden rule rates describing uncorrelated sequential tunneling processes, we systematically include higher-order correlated sequential tunneling (CST) diagrams within the standard Weisskopf-Wigner approximation. We provide estimates for the parameter regions where CST effects can be important. Focusing mainly on the temperature dependence of the peak conductance, we discuss the relation of these findings to previous theoretical and experimental results.

Purely wavelength- and amplitude-modulated quartz-enhanced photoacoustic spectroscopy.

PubMed

Patimisco, Pietro; Sampaolo, Angelo; Bidaux, Yves; Bismuto, Alfredo; Scott, Marshall; Jiang, James; Muller, Antoine; Faist, Jerome; Tittel, Frank K; Spagnolo, Vincenzo

2016-11-14

We report here on a quartz-enhanced photoacoustic (QEPAS) sensor employing a quantum cascade laser (QCL) structure capable of operating in a pure amplitude or wavelength modulation configuration. The QCL structure is composed of three electrically independent sections: Gain, Phase (PS) and Master Oscillator (MO). Selective current pumping of these three sections allows obtaining laser wavelength tuning without changes in the optical power, and power modulation without emission wavelength shifts. A pure QEPAS amplitude modulation condition is obtained by modulating the PS current, while pure wavelength modulation is achieved by modulating simultaneously the MO and PS QCL sections and slowly scanning the DC current level injected in the PS section.

Direct link of a mid-infrared QCL to a frequency comb by optical injection.

PubMed

Borri, S; Galli, I; Cappelli, F; Bismuto, A; Bartalini, S; Cancio, P; Giusfredi, G; Mazzotti, D; Faist, J; De Natale, P

2012-03-15

A narrow-linewidth comb-linked nonlinear source is used as master radiation to injection lock a room-temperature mid-infrared quantum cascade laser (QCL). This process leads to a direct lock of the QCL to the optical frequency comb, providing the unique features of narrow linewidth, absolute frequency, higher output power, and wide mode-hop-free tunability. The QCL reproduces the injected radiation within more than 94%, with a reduction of the frequency-noise spectral density by 3 to 4 orders of magnitude up to about 100 kHz, and a linewidth narrowing from a few MHz to 20 kHz.

Generalized master equation via aging continuous-time random walks.

PubMed

Allegrini, Paolo; Aquino, Gerardo; Grigolini, Paolo; Palatella, Luigi; Rosa, Angelo

2003-11-01

We discuss the problem of the equivalence between continuous-time random walk (CTRW) and generalized master equation (GME). The walker, making instantaneous jumps from one site of the lattice to another, resides in each site for extended times. The sojourn times have a distribution density psi(t) that is assumed to be an inverse power law with the power index micro. We assume that the Onsager principle is fulfilled, and we use this assumption to establish a complete equivalence between GME and the Montroll-Weiss CTRW. We prove that this equivalence is confined to the case where psi(t) is an exponential. We argue that is so because the Montroll-Weiss CTRW, as recently proved by Barkai [E. Barkai, Phys. Rev. Lett. 90, 104101 (2003)], is nonstationary, thereby implying aging, while the Onsager principle is valid only in the case of fully aged systems. The case of a Poisson distribution of sojourn times is the only one with no aging associated to it, and consequently with no need to establish special initial conditions to fulfill the Onsager principle. We consider the case of a dichotomous fluctuation, and we prove that the Onsager principle is fulfilled for any form of regression to equilibrium provided that the stationary condition holds true. We set the stationary condition on both the CTRW and the GME, thereby creating a condition of total equivalence, regardless of the nature of the waiting-time distribution. As a consequence of this procedure we create a GME that is a bona fide master equation, in spite of being non-Markov. We note that the memory kernel of the GME affords information on the interaction between system of interest and its bath. The Poisson case yields a bath with infinitely fast fluctuations. We argue that departing from the Poisson form has the effect of creating a condition of infinite memory and that these results might be useful to shed light on the problem of how to unravel non-Markov quantum master equations.

Evolution of epidemiologic methods and concepts in selected textbooks of the 20th century.

PubMed

Zhang, Fang F; Michaels, Desireé C; Mathema, Barun; Kauchali, Shuaib; Chatterjee, Anjan; Ferris, David C; James, Tamarra M; Knight, Jennifer; Dounel, Matthew; Tawfik, Hebatullah O; Frohlich, Janet A; Kuang, Li; Hoskin, Elena K; Veldman, Frederick J; Baldi, Giulia; Mlisana, Koleka P; Mametja, Lerole D; Diaz, Angela; Khan, Nealia L; Sternfels, Pamela; Sevigny, Jeffery J; Shamam, Asher; Morabia, Alfredo

2004-01-01

Textbooks are an expression of the state of development of a discipline at a given moment in time. By reviewing eight epidemiology textbooks published over the course of a century, we have attempted to trace the evolution of five epidemiologic concepts and methods: study design (cohort studies and case-control studies), confounding, bias, interaction and causal inference. Overall, these eight textbooks can be grouped into three generations. Greenwood (1935) and Hill (first edition 1937; version reviewed 1961)'s textbooks belong to the first generation, "early epidemiology", which comprise early definitions of bias and confounding. The second generation, "classic epidemiology", represented by the textbooks of Morris (first edition 1957; version reviewed 1964), MacMahon & Pugh (first edition 1960; version reviewed 1970), Susser (1973), and Lilienfeld & Lilienfeld (first edition 1976; version reviewed 1980), clarifies the properties of cohort and case-control study designs and the theory of disease causation. Miettinen (1985) and Rothman (1986)'s textbooks belong to a third generation, "modern epidemiology", presenting an integrated perspective on study designs and their measures of outcome, as well as distinguishing and formalizing the concepts of confounding and interaction. Our review demonstrates that epidemiology, as a scientific discipline, is in constant evolution and transformation. It is likely that new methodological tools, able to assess the complexity of the causes of human health, will be proposed in future generations of textbooks.

Decoherence in quantum lossy systems: superoperator and matrix techniques

NASA Astrophysics Data System (ADS)

Yazdanpanah, Navid; Tavassoly, Mohammad Kazem; Moya-Cessa, Hector Manuel

2017-06-01

Due to the unavoidably dissipative interaction between quantum systems with their environments, the decoherence flows inevitably into the systems. Therefore, to achieve a better understanding on how decoherence affects on the damped systems, a fundamental investigation of master equation seems to be required. In this regard, finding out the missed information which has been lost due to irreversibly of the dissipative systems, is also of practical importance in quantum information science. Motivating by these facts, in this work we want to use superoperator and matrix techniques, by which we are able to illustrate two methods to obtain the explicit form of density operators corresponding to damped systems at arbitrary temperature T ≥ 0. To establish the potential abilities of the suggested methods, we apply them to deduce the density operator of some practical well-known quantum systems. Using the superoperator techniques, at first we obtain the density operator of a damped system which includes a qubit interacting with a single-mode quantized field within an optical cavity. As the second system, we study the decoherence of a quantized field within an optical damped cavity. We also use our proposed matrix method to study the decoherence of a system which includes two qubits in the interaction with each other via dipole-dipole interaction and at the same time with a quantized field in a lossy cavity. The influences of dissipation on the decoherence of dynamical properties of these systems are also numerically investigated. At last, the advantages of the proposed superoperator techniques in comparison with matrix method are explained.

Continuous joint measurement and entanglement of qubits in remote cavities

NASA Astrophysics Data System (ADS)

Motzoi, Felix; Whaley, K. Birgitta; Sarovar, Mohan

2015-09-01

We present a first-principles theoretical analysis of the entanglement of two superconducting qubits in spatially separated microwave cavities by a sequential (cascaded) probe of the two cavities with a coherent mode, that provides a full characterization of both the continuous measurement induced dynamics and the entanglement generation. We use the SLH formalism to derive the full quantum master equation for the coupled qubits and cavities system, within the rotating wave and dispersive approximations, and conditioned equations for the cavity fields. We then develop effective stochastic master equations for the dynamics of the qubit system in both a polaronic reference frame and a reduced representation within the laboratory frame. We compare simulations with and analyze tradeoffs between these two representations, including the onset of a non-Markovian regime for simulations in the reduced representation. We provide conditions for ensuring persistence of entanglement and show that using shaped pulses enables these conditions to be met at all times under general experimental conditions. The resulting entanglement is shown to be robust with respect to measurement imperfections and loss channels. We also study the effects of qubit driving and relaxation dynamics during a weak measurement, as a prelude to modeling measurement-based feedback control in this cascaded system.

Liouville master equation for multi-electron dynamics during ion-surface interactions

NASA Astrophysics Data System (ADS)

Wirtz, L.; Reinhold, C. O.; Lemell, C.; Burgdorfer, J.

2003-05-01

We present a simulation of the neutralization of highly charged ions in front of a LiF(100) surface including the close-collision regime above the surface. Our approach employs a Monte-Carlo solution of the Liouville master equation for the joint probability density of the ionic motion and the electronic population of the projectile and the target surface. It includes single as well as double particle-hole (de)excitation processes and incorporates electron correlation effects through the conditional dynamics of population strings. The input in terms of elementary one- and two-electron transfer rates is determined from CTMC calculations as well as quantum mechanical Auger calculations. For slow projectiles and normal incidence, the ionic motion depends sensitively on the interplay between image acceleration towards the surface and repulsion by an ensemble of positive hole charges in the surface (``trampoline effect"). For Ne10+ ions we find that image acceleration dominates and no collective backscattering high above the surface takes place. For grazing incidence, our simulation delineates the pathways to complete neutralization. In accordance with recent experimental observations, most ions are reflected as neutrals or even as singly charged negative particles, irrespective of the charge state of the incoming ion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Meng-Zheng; School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000; Ye, Liu, E-mail: yeliu@ahu.edu.cn

An efficient scheme is proposed to implement phase-covariant quantum cloning by using a superconducting transmon qubit coupled to a microwave cavity resonator in the strong dispersive limit of circuit quantum electrodynamics (QED). By solving the master equation numerically, we plot the Wigner function and Poisson distribution of the cavity mode after each operation in the cloning transformation sequence according to two logic circuits proposed. The visualizations of the quasi-probability distribution in phase-space for the cavity mode and the occupation probability distribution in the Fock basis enable us to penetrate the evolution process of cavity mode during the phase-covariant cloning (PCC)more » transformation. With the help of numerical simulation method, we find out that the present cloning machine is not the isotropic model because its output fidelity depends on the polar angle and the azimuthal angle of the initial input state on the Bloch sphere. The fidelity for the actual output clone of the present scheme is slightly smaller than one in the theoretical case. The simulation results are consistent with the theoretical ones. This further corroborates our scheme based on circuit QED can implement efficiently PCC transformation.« less

State-of-the-art thermochemical and kinetic computations for astrochemical complex organic molecules: formamide formation in cold interstellar clouds as a case study

PubMed Central

Vazart, Fanny; Calderini, Danilo; Puzzarini, Cristina; Skouteris, Dimitrios

2017-01-01

We propose an integrated computational strategy aimed at providing reliable thermochemical and kinetic information on the formation processes of astrochemical complex organic molecules. The approach involves state-of-the-art quantum-mechanical computations, second-order vibrational perturbation theory, and kinetic models based on capture and transition state theory together with the master equation approach. Notably, tunneling, quantum reflection, and leading anharmonic contributions are accounted for in our model. Formamide has been selected as a case study in view of its interest as a precursor in the abiotic amino acid synthesis. After validation of the level of theory chosen for describing the potential energy surface, we have investigated several pathways of the OH+CH2NH and NH2+HCHO reaction channels. Our results indicate that both reaction channels are essentially barrier-less (in the sense that all relevant transition states lie below or only marginally above the reactants) and can, therefore, occur under the low temperature conditions of interstellar objects provided that tunneling is taken into the proper account. PMID:27689448

Coupling rotational and translational motion via a continuous measurement in an optomechanical sphere

NASA Astrophysics Data System (ADS)

Ralph, Jason F.; Jacobs, Kurt; Coleman, Jonathon

2016-09-01

We consider a measurement of the position of a spot painted on the surface of a trapped nano-optomechanical sphere. The measurement extracts information about the position of the spot and in doing so measures a combination of the orientation and position of the sphere. The quantum backaction of the measurement entangles and correlates these two degrees of freedom. Such a measurement is not available for atoms or ions and provides a mechanism to probe the quantum mechanical properties of trapped optomechanical spheres. In performing simulations of this measurement process we also test a numerical method introduced recently by Rouchon and collaborators [H. Amini, M. Mirrahimi, and P. Rouchon, in Proceedings of the 50th IEEE Conference on Decision and Control (CDC, 2011), pp. 6242-6247; P. Rouchon and J. F. Ralph, Phys. Rev. A 91, 012118 (2015), 10.1103/PhysRevA.91.012118] for solving stochastic master equations. This method guarantees the positivity of the density matrix when the Lindblad operators for all simultaneous continuous measurements are mutually commuting. We show that it is both simpler and far more efficient than previous methods.

Oxide double quantum dot - an answer to the qubit problem?

NASA Astrophysics Data System (ADS)

Yarlagadda, Sudhakar; Dey, Amit

We propose that oxide-based double quantum dots with only one electron (tunnelling between the dots) can be regarded as a qubit with little decoherence; these dots can possibly meet future challenges of miniaturization. The tunnelling of the eg electron between the dots and the attraction between the electron and the hole on adjacent dots can be modelled as an anisotropic Heisenberg interaction between two spins with the total z-component of the spins being zero. We study two anisotropically interacting spins coupled to optical phonons; we restrict our analysis to the regime of strong coupling to the environment, to the antiadiabatic region, and to the subspace with zero value for SzT (the z-component of the total spin). In the case where each spin is coupled to a different phonon bath, we assume that the system and the environment are initially uncorrelated (and form a simply separable state) in the polaronic frame of reference. By analyzing the polaron dynamics through a non-Markovian quantum master equation, we find that the system manifests a small amount of decoherence that decreases both with increasing nonadiabaticity and with enhancing strength of coupling g. Recently I got an invitation to visit Argonne National Lab from Jan./2106 to end of March/2016. I thought I would give a talk at APS March meeting. Please accept the submission.

Decoherence in models for hard-core bosons coupled to optical phonons

NASA Astrophysics Data System (ADS)

Dey, A.; Lone, M. Q.; Yarlagadda, S.

2015-09-01

Understanding coherent dynamics of excitons, spins, or hard-core bosons (HCBs) has tremendous scientific and technological implications for quantum computation. Here, we study decay of excited-state population and decoherence in two models for HCBs, namely, a two-site HCB model with site-dependent strong potentials and subject to non-Markovian dynamics and an infinite-range HCB model governed by Markovian dynamics. Both models are investigated in the regimes of antiadiabaticity and strong HCB-phonon coupling with each site providing a different local optical phonon environment; furthermore, the HCB systems in both models are taken to be initially uncorrelated with the environment in the polaronic frame of reference. In the case of the two-site HCB model, we show clearly that the degree of decoherence and decay of excited state are enhanced by the proximity of the site-energy difference to the eigenenergy of phonons and are most pronounced when the site-energy difference is at resonance with twice the polaronic energy; additionally, the decoherence and the decay effects are reduced when the strength of HCB-phonon coupling is increased. For the infinite-range model, when the site energies are the same, we derive an effective many-body Hamiltonian that commutes with the long-range system Hamiltonian and thus has the same set of eigenstates; consequently, a quantum-master-equation approach shows that the quantum states of the system do not decohere.

Quantum fluctuation theorems and power measurements

NASA Astrophysics Data System (ADS)

Prasanna Venkatesh, B.; Watanabe, Gentaro; Talkner, Peter

2015-07-01

Work in the paradigm of the quantum fluctuation theorems of Crooks and Jarzynski is determined by projective measurements of energy at the beginning and end of the force protocol. In analogy to classical systems, we consider an alternative definition of work given by the integral of the supplied power determined by integrating up the results of repeated measurements of the instantaneous power during the force protocol. We observe that such a definition of work, in spite of taking account of the process dependence, has different possible values and statistics from the work determined by the conventional two energy measurement approach (TEMA). In the limit of many projective measurements of power, the system’s dynamics is frozen in the power measurement basis due to the quantum Zeno effect leading to statistics only trivially dependent on the force protocol. In general the Jarzynski relation is not satisfied except for the case when the instantaneous power operator commutes with the total Hamiltonian at all times. We also consider properties of the joint statistics of power-based definition of work and TEMA work in protocols where both values are determined. This allows us to quantify their correlations. Relaxing the projective measurement condition, weak continuous measurements of power are considered within the stochastic master equation formalism. Even in this scenario the power-based work statistics is in general not able to reproduce qualitative features of the TEMA work statistics.

Non-Markovian dynamics of fermionic and bosonic systems coupled to several heat baths

NASA Astrophysics Data System (ADS)

Hovhannisyan, A. A.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Lacroix, D.

2018-03-01

Employing the fermionic and bosonic Hamiltonians for the collective oscillator linearly FC-coupled with several heat baths, the analytical expressions for the collective occupation number are derived within the non-Markovian quantum Langevin approach. The master equations for the occupation number of collective subsystem are derived and discussed. In the case of Ohmic dissipation with Lorenzian cutoffs, the possibility of reduction of the system with several heat baths to the system with one heat bath is analytically demonstrated. For the fermionic and bosonic systems, a comparative analysis is performed between the collective subsystem coupled to two heat baths and the reference case of the subsystem coupled to one bath.

Decoherence dynamics of interacting qubits coupled to a bath of local optical phonons

NASA Astrophysics Data System (ADS)

Lone, Muzaffar Qadir; Yarlagadda, S.

2016-04-01

We study decoherence in an interacting qubit system described by infinite range Heisenberg model (IRHM) in a situation where the system is coupled to a bath of local optical phonons. Using perturbation theory in polaron frame of reference, we derive an effective Hamiltonian that is valid in the regime of strong spin-phonon coupling under nonadiabatic conditions. It is shown that the effective Hamiltonian commutes with the IRHM upto leading orders of perturbation and thus has the same eigenstates as the IRHM. Using a quantum master equation with Markovian approximation of dynamical evolution, we show that the off-diagonal elements of the density matrix do not decay in the energy eigen basis of IRHM.

Quantum Cascade Laser Master-Oscillator Power-Amplifier with 1.5-W Output Power at 300 K

DTIC Science & Technology

2011-05-25

327·333 (2008). 7", L. Diehl, C. Pfliigl, M. F. Witinski, P. Wang, T. J. Tague Jr., and F. Capasso, "Fouriertraosfonn ’pcc_ uti1izing mid- infrared ...8217 W. W. Bewley. J. R. Lindle, C. L. Canedy. J. A. Nolde, D. C. Lunobcc.I. "urgallman, and J. R. Meyer, "Broad-stripe, single-mode. mid-IR interband ...AB8PA DATE: cR5 YrU-t 1/ CASE # h k ftGW-& 611’-O!J6tJ IS. M. Troccoli, C. Gmachl, F. Capasso,D. L. Sivco, and A. Y. Cha, "Mid- infrared 0 .. -7.4 pm

Controllable magnetic thermal rectification in a SMM dimmer with the Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Xu, Ai-Hua; Liu, Juan; Luo, Bo

2016-10-01

Using the quantum master equation, we studied the thermally driven magnonic spin current in a single-molecule magnet (SMM) dimer with the Dzyaloshinskii-Moriya interaction (DMI). Due to the asymmetric DMI, one can observe the thermal rectifying effect in the case of the spatial symmetry coupling with the thermal reservoirs. The properties of the thermal rectification can be controlled by tuning the angle and intensity of the magnetic field. Specially, when the DM vector and magnetic field point at the specific angles, the thermal rectifying effect disappears. And this phenomenon does not depend on the intensities of DMI and magnetic field, the temperature bias and the magnetic anisotropies of the SMM.

Book Review:

NASA Astrophysics Data System (ADS)

Beenakker, C. W. J.

2005-08-01

Quantum Noise is advertised as a handbook, and this is indeed how it functions for me these days: it is a book that I keep within hand's reach, ready to be consulted on the proper use of quantum stochastic methods in the course of my research on quantum dots. I should point out that quantum optics, the target field for this book, is not my field by training. So I have much to learn, and find this handbook to be a reliable and helpful guide. Crispin Gardiner previously wrote the Handbook of Stochastic Methods (also published by Springer), which provides an overview of methods in classical statistical physics. Quantum Noise, written jointly with Peter Zoller, is the counterpart for quantum statistical physics, and indeed the two books rely on each other by frequent cross referencing. The fundamental problem addressed by Quantum Noise is how the quantum dynamics of an open system can be described statistically by treating the environment as a source of noise. This is a general problem in condensed matter physics (in particular in the context of Josephson junctions) and in quantum optics. The emphasis in this book in on the optical applications (for condensed matter applications one could consult Quantum Dissipative Systems by Ulrich Weiss, published by World Scientific). The optical applications centre around the interaction of light with atoms, where the atoms represent the open system and the light is the noisy environment. A complete description of the production and detection of non-classical states of radiation (such as squeezed states) can be obtained using one of the equivalent quantum stochastic formulations: the quantum Langevin equation for the field operators (in either the Ito or the Stratonovich form), the Master equation for the density matrix, or the stochastic Schrödinger equation for the wave functions. Each formulation is fully developed here (as one would expect from a handbook), with detailed instructions on how to go from one to the other. The development of the topic is precise and well-organized. The derivations are written out in sufficient detail, without frustrating comments like `it can be shown that'. The book is not quite self-contained, because it relies on the Handbook of Stochastic Methods for some background material (notably the issue of Ito versus Stratonovich). Still, one could very well use this book as a text for a course, supplying the background material to the students in some other form. Quantum Noise is now in its third edition. The second edition was a major expansion, including applications to laser cooling and quantum information processing. The third edition is a relatively minor upgrade, consisting mainly of pointers to recent literature. If you own the second edition, you might well skip this upgrade. If you do not yet own the book, or are still at edition 1, then I would enthusiastically recommend acquiring this handbook, regardless of whether you work in quantum optics or in another field of quantum physics. As I did, you might well find a new tool to attack your favourite problem.

Delving Into Dissipative Quantum Dynamics: From Approximate to Numerically Exact Approaches

NASA Astrophysics Data System (ADS)

Chen, Hsing-Ta

In this thesis, I explore dissipative quantum dynamics of several prototypical model systems via various approaches, ranging from approximate to numerically exact schemes. In particular, in the realm of the approximate I explore the accuracy of Pade-resummed master equations and the fewest switches surface hopping (FSSH) algorithm for the spin-boson model, and non-crossing approximations (NCA) for the Anderson-Holstein model. Next, I develop new and exact Monte Carlo approaches and test them on the spin-boson model. I propose well-defined criteria for assessing the accuracy of Pade-resummed quantum master equations, which correctly demarcate the regions of parameter space where the Pade approximation is reliable. I continue the investigation of spin-boson dynamics by benchmark comparisons of the semiclassical FSSH algorithm to exact dynamics over a wide range of parameters. Despite small deviations from golden-rule scaling in the Marcus regime, standard surface hopping algorithm is found to be accurate over a large portion of parameter space. The inclusion of decoherence corrections via the augmented FSSH algorithm improves the accuracy of dynamical behavior compared to exact simulations, but the effects are generally not dramatic for the cases I consider. Next, I introduce new methods for numerically exact real-time simulation based on real-time diagrammatic Quantum Monte Carlo (dQMC) and the inchworm algorithm. These methods optimally recycle Monte Carlo information from earlier times to greatly suppress the dynamical sign problem. In the context of the spin-boson model, I formulate the inchworm expansion in two distinct ways: the first with respect to an expansion in the system-bath coupling and the second as an expansion in the diabatic coupling. In addition, a cumulant version of the inchworm Monte Carlo method is motivated by the latter expansion, which allows for further suppression of the growth of the sign error. I provide a comprehensive comparison of the performance of the inchworm Monte Carlo algorithms to other exact methodologies as well as a discussion of the relative advantages and disadvantages of each. Finally, I investigate the dynamical interplay between the electron-electron interaction and the electron-phonon coupling within the Anderson-Holstein model via two complementary NCAs: the first is constructed around the weak-coupling limit and the second around the polaron limit. The influence of phonons on spectral and transport properties is explored in equilibrium, for non-equilibrium steady state and for transient dynamics after a quench. I find the two NCAs disagree in nontrivial ways, indicating that more reliable approaches to the problem are needed. The complementary frameworks used here pave the way for numerically exact methods based on inchworm dQMC algorithms capable of treating open systems simultaneously coupled to multiple fermionic and bosonic baths.

Stochastic description of quantum Brownian dynamics

NASA Astrophysics Data System (ADS)

Yan, Yun-An; Shao, Jiushu

2016-08-01

Classical Brownian motion has well been investigated since the pioneering work of Einstein, which inspired mathematicians to lay the theoretical foundation of stochastic processes. A stochastic formulation for quantum dynamics of dissipative systems described by the system-plus-bath model has been developed and found many applications in chemical dynamics, spectroscopy, quantum transport, and other fields. This article provides a tutorial review of the stochastic formulation for quantum dissipative dynamics. The key idea is to decouple the interaction between the system and the bath by virtue of the Hubbard-Stratonovich transformation or Itô calculus so that the system and the bath are not directly entangled during evolution, rather they are correlated due to the complex white noises introduced. The influence of the bath on the system is thereby defined by an induced stochastic field, which leads to the stochastic Liouville equation for the system. The exact reduced density matrix can be calculated as the stochastic average in the presence of bath-induced fields. In general, the plain implementation of the stochastic formulation is only useful for short-time dynamics, but not efficient for long-time dynamics as the statistical errors go very fast. For linear and other specific systems, the stochastic Liouville equation is a good starting point to derive the master equation. For general systems with decomposable bath-induced processes, the hierarchical approach in the form of a set of deterministic equations of motion is derived based on the stochastic formulation and provides an effective means for simulating the dissipative dynamics. A combination of the stochastic simulation and the hierarchical approach is suggested to solve the zero-temperature dynamics of the spin-boson model. This scheme correctly describes the coherent-incoherent transition (Toulouse limit) at moderate dissipation and predicts a rate dynamics in the overdamped regime. Challenging problems such as the dynamical description of quantum phase transition (local- ization) and the numerical stability of the trace-conserving, nonlinear stochastic Liouville equation are outlined.

Theory and modelling of light-matter interactions in photonic crystal cavity systems coupled to quantum dot ensembles

NASA Astrophysics Data System (ADS)

Cartar, William K.

Photonic crystal microcavity quantum dot lasers show promise as high quality-factor, low threshold lasers, that can be integrated on-chip, with tunable room temperature opera- tions. However, such semiconductor microcavity lasers are notoriously difficult to model in a self-consistent way and are primarily modelled by simplified rate equation approxima- tions, typically fit to experimental data, which limits investigations of their optimization and fundamental light-matter interaction processes. Moreover, simple cavity mode optical theory and rate equations have recently been shown to fail in explaining lasing threshold trends in triangular lattice photonic crystal cavities as a function of cavity size, and the potential impact of fabrication disorder is not well understood. In this thesis, we develop a simple but powerful numerical scheme for modelling the quantum dot active layer used for lasing in these photonic crystal cavity structures, as an ensemble of randomly posi- tioned artificial two-level atoms. Each two-level atom is defined by optical Bloch equations solved by a quantum master equation that includes phenomenological pure dephasing and an incoherent pump rate that effectively models a multi-level gain system. Light-matter in- teractions of both passive and lasing structures are analyzed using simulation defined tools and post-simulation Green function techniques. We implement an active layer ensemble of up to 24,000 statistically unique quantum dots in photonic crystal cavity simulations, using a self-consistent finite-difference time-domain method. This method has the distinct advantage of capturing effects such as dipole-dipole coupling and radiative decay, without the need for any phenomenological terms, since the time-domain solution self-consistently captures these effects. Our analysis demonstrates a powerful ability to connect with recent experimental trends, while remaining completely general in its set-up; for example, we do not invoke common approximations such as the rotating-wave or slowly-varying envelope approximations, and solve dynamics with zero a priori knowledge.

Production of a sterile species via active-sterile mixing: An exactly solvable model

NASA Astrophysics Data System (ADS)

Boyanovsky, D.

2007-11-01

The production of a sterile species via active-sterile mixing in a thermal medium is studied in an exactly solvable model. The exact time evolution of the sterile distribution function is determined by the dispersion relations and damping rates Γ1,2 for the quasiparticle modes. These depend on γ˜=Γaa/2ΔE, with Γaa the interaction rate of the active species in absence of mixing and ΔE the oscillation frequency in the medium without damping. γ˜≪1, γ˜≫1 describe the weak and strong damping limits, respectively. For γ˜≪1, Γ1=Γaacos⁡2θm; Γ2=Γaasin⁡2θm where θm is the mixing angle in the medium and the sterile distribution function does not obey a simple rate equation. For γ˜≫1, Γ1=Γaa and Γ2=Γaasin⁡22θm/4γ˜2, is the sterile production rate. In this regime sterile production is suppressed and the oscillation frequency vanishes at an Mikheyev-Smirnov-Wolfenstein (MSW) resonance, with a breakdown of adiabaticity. These are consequences of quantum Zeno suppression. For active neutrinos with standard model interactions the strong damping limit is only available near an MSW resonance if sin⁡2θ≪αw with θ the vacuum mixing angle. The full set of quantum kinetic equations for sterile production for arbitrary γ˜ are obtained from the quantum master equation. Cosmological resonant sterile neutrino production is quantum Zeno suppressed relieving potential uncertainties associated with the QCD phase transition.

BOOK REVIEW: Modern Canonical Quantum General Relativity

NASA Astrophysics Data System (ADS)

Kiefer, Claus

2008-06-01

The open problem of constructing a consistent and experimentally tested quantum theory of the gravitational field has its place at the heart of fundamental physics. The main approaches can be roughly divided into two classes: either one seeks a unified quantum framework of all interactions or one starts with a direct quantization of general relativity. In the first class, string theory (M-theory) is the only known example. In the second class, one can make an additional methodological distinction: while covariant approaches such as path-integral quantization use the four-dimensional metric as an essential ingredient of their formalism, canonical approaches start with a foliation of spacetime into spacelike hypersurfaces in order to arrive at a Hamiltonian formulation. The present book is devoted to one of the canonical approaches—loop quantum gravity. It is named modern canonical quantum general relativity by the author because it uses connections and holonomies as central variables, which are analogous to the variables used in Yang Mills theories. In fact, the canonically conjugate variables are a holonomy of a connection and the flux of a non-Abelian electric field. This has to be contrasted with the older geometrodynamical approach in which the metric of three-dimensional space and the second fundamental form are the fundamental entities, an approach which is still actively being pursued. It is the author's ambition to present loop quantum gravity in a way in which every step is formulated in a mathematically rigorous form. In his own words: 'loop quantum gravity is an attempt to construct a mathematically rigorous, background-independent, non-perturbative quantum field theory of Lorentzian general relativity and all known matter in four spacetime dimensions, not more and not less'. The formal Leitmotiv of loop quantum gravity is background independence. Non-gravitational theories are usually quantized on a given non-dynamical background. In contrast, due to the geometrical nature of gravity, no such background exists in quantum gravity. Instead, the notion of a background is supposed to emerge a posteriori as an approximate notion from quantum states of geometry. As a consequence, the standard ultraviolet divergences of quantum field theory do not show up because there is no limit of Δx → 0 to be taken in a given spacetime. On the other hand, it is open whether the theory is free of any type of divergences and anomalies. A central feature of any canonical approach, independent of the choice of variables, is the existence of constraints. In geometrodynamics, these are the Hamiltonian and diffeomorphism constraints. They also hold in loop quantum gravity, but are supplemented there by the Gauss constraint, which emerges due to the use of triads in the formalism. These constraints capture all the physics of the quantum theory because no spacetime is present anymore (analogous to the absence of trajectories in quantum mechanics), so no additional equations of motion are needed. This book presents a careful and comprehensive discussion of these constraints. In particular, the constraint algebra is calculated in a transparent and explicit way. The author makes the important assumption that a Hilbert-space structure is still needed on the fundamental level of quantum gravity. In ordinary quantum theory, such a structure is needed for the probability interpretation, in particular for the conservation of probability with respect to external time. It is thus interesting to see how far this concept can be extrapolated into the timeless realm of quantum gravity. On the kinematical level, that is, before the constraints are imposed, an essentially unique Hilbert space can be constructed in terms of spin-network states. Potentially problematic features are the implementation of the diffeomorphism and Hamiltonian constraints. The Hilbert space Hdiff defined on the diffeomorphism subspace can throw states out of the kinematical Hilbert space and is thus not contained in it. Moreover, the Hamiltonian constraint does not seem to preserve Hdiff, so its implementation remains open. To avoid some of these problems, the author proposes his 'master constraint programme' in which the infinitely many local Hamiltonian constraints are combined into one master constraint. This is a subject of his current research. With regard to this situation, it is not surprising that the main results in loop quantum gravity are found on the kinematical level. An especially important feature are the discrete spectra of geometric operators such as the area operator. This quantifies the earlier heuristic ideas about a discreteness at the Planck scale. The hope is that these results survive the consistent implementation of all constraints. The status of loop quantum gravity is concisely and competently summarized in this volume, whose author is himself one of the pioneers of this approach. What is the relation of this book to the other monograph on loop quantum gravity, written by Carlo Rovelli and published in 2004 under the title Quantum Gravity with the same company? In the words of the present author: 'the two books are complementary in the sense that they can be regarded almost as volume I ('introduction and conceptual framework') and volume II ('mathematical framework and applications') of a general presentation of quantum general relativity in general and loop quantum gravity in particular'. In fact, the present volume gives a complete and self-contained presentation of the required mathematics, especially on the approximately 200 pages of chapters 18 33. As for the physical applications, the main topic is the microscopic derivation of the black-hole entropy. This is presented in a clear and detailed form. Employing the concept of an isolated horizon (a local generalization of an event horizon), the counting of surface states gives an entropy proportional to the horizon area. It also contains the Barbero Immirzi parameter β, which is a free parameter of the theory. Demanding, on the other hand, that the entropy be equal to the Bekenstein Hawking entropy would fix this parameter. Other applications such as loop quantum cosmology are only briefly touched upon. Since loop quantum gravity is a very active field of research, the author warns that the present book can at best be seen as a snapshot. Part of the overall picture may thus in the future be subject to modifications. For example, recent work by the author using a concept of dust time is not yet covered here. Nevertheless, I expect that this volume will continue to serve as a valuable introduction and reference book. It is essential reading for everyone working on loop quantum gravity.

Growth and Characterization of III-V Semiconductors for Device Applications

NASA Technical Reports Server (NTRS)

Williams, Michael D.

2000-01-01

The research goal was to achieve a fundamental understanding of the physical processes occurring at the surfaces and interfaces of epitaxially grown InGaAs/GaAs (100) heterostructures. This will facilitate the development of quantum well devices for infrared optical applications and provide quantitative descriptions of key phenomena which impact their performance. Devices impacted include high-speed laser diodes and modulators for fiber optic communications at 1.55 micron wavelengths and intersub-band lasers for longer infrared wavelengths. The phenomenon of interest studied was the migration of indium in InGaAs structures. This work centered on the molecular beam epitaxy reactor and characterization apparatus donated to CAU by AT&T Bell Laboratories. The material characterization tool employed was secondary ion mass spectrometry. The training of graduate and undergraduate students was an integral part of this program. The graduate students received a thorough exposure to state-of-the-art techniques and equipment for semiconductor materials analysis as part of the Master''s degree requirement in physics. The undergraduates were exposed to a minority scientist who has an excellent track record in this area. They also had the opportunity to explore surface physics as a career option. The results of the scientific work was published in a refereed journal and several talks were presented professional conferences and academic seminars.

Liouville master equation for multielectron dynamics: Neutralization of highly charged ions near a LiF surface

NASA Astrophysics Data System (ADS)

Wirtz, Ludger; Reinhold, Carlos O.; Lemell, Christoph; Burgdörfer, Joachim

2003-01-01

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte Carlo solution of the Liouville master equation for the joint probability density of the ionic motion and the electronic population of the projectile and the target surface. It includes single as well as double particle-hole (de)excitation processes and incorporates electron correlation effects through the conditional dynamics of population strings. The input in terms of elementary one- and two-electron transfer rates is determined from classical trajectory Monte Carlo calculations as well as quantum-mechanical Auger calculations. For slow projectiles and normal incidence, the ionic motion depends sensitively on the interplay between image acceleration towards the surface and repulsion by an ensemble of positive hole charges in the surface (“trampoline effect”). For Ne10+ we find that image acceleration is dominant and no collective backscattering high above the surface takes place. For grazing incidence, our simulation delineates the pathways to complete neutralization. In accordance with recent experimental observations, most ions are reflected as neutral or even as singly charged negative particles, irrespective of the charge state of the incoming ions.

Cavity-induced mirror-mirror entanglement in a single-atom Raman laser

NASA Astrophysics Data System (ADS)

Teklu, Berihu; Byrnes, Tim; Khan, Faisal Shah

2018-02-01

We address an experimental scheme to analyze the optical bistability and the entanglement of two movable mirrors coupled to a two-mode laser inside a doubly resonant cavity. With this aim we investigate the master equations of the atom-cavity subsystem in conjunction with the quantum Langevin equations that describe the interaction of the mirror cavity. The parametric amplification-type coupling induced by the two-photon coherence on the optical bistability of the intracavity mean photon numbers is found and investigated. Under this condition, the optical intensities exhibit bistability for all large values of cavity laser detuning. We also provide numerical evidence for the generation of strong entanglement between the movable mirrors and show that it is robust against environmental thermalization.

Non-Markovian dynamics of a qubit due to single-photon scattering in a waveguide

NASA Astrophysics Data System (ADS)

Fang, Yao-Lung L.; Ciccarello, Francesco; Baranger, Harold U.

2018-04-01

We investigate the open dynamics of a qubit due to scattering of a single photon in an infinite or semi-infinite waveguide. Through an exact solution of the time-dependent multi-photon scattering problem, we find the qubit's dynamical map. Tools of open quantum systems theory allow us then to show the general features of this map, find the corresponding non-Linbladian master equation, and assess in a rigorous way its non-Markovian nature. The qubit dynamics has distinctive features that, in particular, do not occur in emission processes. Two fundamental sources of non-Markovianity are present: the finite width of the photon wavepacket and the time delay for propagation between the qubit and the end of the semi-infinite waveguide.

On the reduced dynamics of a subset of interacting bosonic particles

NASA Astrophysics Data System (ADS)

Gessner, Manuel; Buchleitner, Andreas

2018-03-01

The quantum dynamics of a subset of interacting bosons in a subspace of fixed particle number is described in terms of symmetrized many-particle states. A suitable partial trace operation over the von Neumann equation of an N-particle system produces a hierarchical expansion for the subdynamics of M ≤ N particles. Truncating this hierarchy with a pure product state ansatz yields the general, nonlinear coherent mean-field equation of motion. In the special case of a contact interaction potential, this reproduces the Gross-Pitaevskii equation. To account for incoherent effects on top of the mean-field evolution, we discuss possible extensions towards a second-order perturbation theory that accounts for interaction-induced decoherence in form of a nonlinear Lindblad-type master equation.

Simultaneous dense coding affected by fluctuating massless scalar field

NASA Astrophysics Data System (ADS)

Huang, Zhiming; Ye, Yiyong; Luo, Darong

2018-04-01

In this paper, we investigate the simultaneous dense coding (SDC) protocol affected by fluctuating massless scalar field. The noisy model of SDC protocol is constructed and the master equation that governs the SDC evolution is deduced. The success probabilities of SDC protocol are discussed for different locking operators under the influence of vacuum fluctuations. We find that the joint success probability is independent of the locking operators, but other success probabilities are not. For quantum Fourier transform and double controlled-NOT operators, the success probabilities drop with increasing two-atom distance, but SWAP operator is not. Unlike the SWAP operator, the success probabilities of Bob and Charlie are different. For different noisy interval values, different locking operators have different robustness to noise.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berkelbach, Timothy C., E-mail: tcb2112@columbia.edu; Reichman, David R., E-mail: drr2103@columbia.edu; Hybertsen, Mark S., E-mail: mhyberts@bnl.gov

We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singletmore » fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems.« less

Vibrational and vibronic coherences in the dynamics of the FMO complex

NASA Astrophysics Data System (ADS)

Liu, Xiaomeng; Kühn, Oliver

2016-12-01

The coupled exciton-vibrational dynamics of a seven site Frenkel exciton model of the Fenna-Matthews-Olson (FMO) complex is investigated using a Quantum Master Equation approach. Thereby, one vibrational mode per monomer is treated explicitly as being part of the relevant system. Emphasis is put on the comparison of this model with that of a purely excitonic relevant system. Further, the effects of two different approximations to the exciton-vibrational basis are investigated, namely the one- and two-particle description. Analysis of the vibronic and vibrational density matrix in the site basis points to the importance of on- and inter-site coherences for the exciton transfer. Here, one- and two-particle approximations give rise to qualitatively different results.

Exciton transport in the PE545 complex: insight from atomistic QM/MM-based quantum master equations and elastic network models

NASA Astrophysics Data System (ADS)

Pouyandeh, Sima; Iubini, Stefano; Jurinovich, Sandro; Omar, Yasser; Mennucci, Benedetta; Piazza, Francesco

2017-12-01

In this paper, we work out a parameterization of environmental noise within the Haken-Strobl-Reinenker (HSR) model for the PE545 light-harvesting complex, based on atomic-level quantum mechanics/molecular mechanics (QM/MM) simulations. We use this approach to investigate the role of various auto- and cross-correlations in the HSR noise tensor, confirming that site-energy autocorrelations (pure dephasing) terms dominate the noise-induced exciton mobility enhancement, followed by site energy-coupling cross-correlations for specific triplets of pigments. Interestingly, several cross-correlations of the latter kind, together with coupling-coupling cross-correlations, display clear low-frequency signatures in their spectral densities in the 30-70 cm-1 region. These slow components lie at the limits of validity of the HSR approach, which requires that environmental fluctuations be faster than typical exciton transfer time scales. We show that a simple coarse-grained elastic-network-model (ENM) analysis of the PE545 protein naturally spotlights collective normal modes in this frequency range that represent specific concerted motions of the subnetwork of cysteines covalenty linked to the pigments. This analysis strongly suggests that protein scaffolds in light-harvesting complexes are able to express specific collective, low-frequency normal modes providing a fold-rooted blueprint of exciton transport pathways. We speculate that ENM-based mixed quantum classical methods, such as Ehrenfest dynamics, might be promising tools to disentangle the fundamental designing principles of these dynamical processes in natural and artificial light-harvesting structures.

Quantum Coherent Dynamics Enhanced by Synchronization with Nonequilibrium Environments

NASA Astrophysics Data System (ADS)

Ishikawa, Akira; Okada, Ryo; Uchiyama, Kazuharu; Hori, Hirokazu; Kobayashi, Kiyoshi

2018-05-01

We report the discovery of the anomalous enhancement of quantum coherent dynamics (CD) due to a non-Markovian mechanism originating from not thermal-equilibrium phonon baths but nonequilibrium coherent phonons. CD is an elementary process for quantum phenomena in nanosystems, such as excitation transfer (ET) in semiconductor nanostructures and light-harvesting systems. CD occurs in homogeneous nanosystems because system inhomogeneity typically destroys coherence. In real systems, however, nanosystems behave as open systems surrounded by environments such as phonon systems. Typically, CD in inhomogeneous nanosystems is enhanced by the absorption and emission of thermal-equilibrium phonons, and the enhancement is described by the conventional master equation. On the other hand, CD is also enhanced by synchronization between population dynamics in nanosystems and coherent phonons; namely, coherent phonons, which are self-consistently induced by phase matching with Rabi oscillation, are fed back to enhance CD. This anomalous enhancement of CD essentially originates from the nonequilibrium and dynamical non-Markovian nature of coherent phonon environments, and the enhancement is firstly predicted by applying time-dependent projection operators to nonequilibrium and dynamical environments. Moreover, CD is discussed by considering ET from a donor to an acceptor. It is found that the enhancement of ET by synchronization with coherent phonons depends on the competition between the output time from a system to an acceptor and the formation time of coherent phonons. These findings in this study will stimulate the design and manipulation of CD via structured environments from the viewpoint of application to nano-photoelectronic devices.

Excitation of collective modes in a quantum flute

NASA Astrophysics Data System (ADS)

Torfason, Kristinn; Manolescu, Andrei; Molodoveanu, Valeriu; Gudmundsson, Vidar

2012-06-01

We use a generalized master equation (GME) formalism to describe the nonequilibrium time-dependent transport of Coulomb interacting electrons through a short quantum wire connected to semi-infinite biased leads. The contact strength between the leads and the wire is modulated by out-of-phase time-dependent potentials that simulate a turnstile device. We explore this setup by keeping the contact with one lead at a fixed location at one end of the wire, whereas the contact with the other lead is placed on various sites along the length of the wire. We study the propagation of sinusoidal and rectangular pulses. We find that the current profiles in both leads depend not only on the shape of the pulses, but also on the position of the second contact. The current reflects standing waves created by the contact potentials, like in a wind musical instrument (for example, a flute), but occurring on the background of the equilibrium charge distribution. The number of electrons in our quantum “flute” device varies between two and three. We find that for rectangular pulses the currents in the leads may flow against the bias for short time intervals, due to the higher harmonics of the charge response. The GME is solved numerically in small time steps without resorting to the traditional Markov and rotating wave approximations. The Coulomb interaction between the electrons in the sample is included via the exact diagonalization method. The system (leads plus sample wire) is described by a lattice model.

Thermoelectrics in Coulomb-coupled quantum dots: Cotunneling and energy-dependent lead couplings

NASA Astrophysics Data System (ADS)

Walldorf, Nicklas; Jauho, Antti-Pekka; Kaasbjerg, Kristen

2017-09-01

We study thermoelectric effects in Coulomb-coupled quantum-dot (CCQD) systems beyond lowest-order tunneling processes and the often applied wide-band approximation. To this end, we present a master-equation (ME) approach based on a perturbative T -matrix calculation of the charge and heat tunneling rates and transport currents. Applying the method to transport through a noninteracting single-level QD, we demonstrate excellent agreement with the Landauer-Büttiker theory when higher-order (cotunneling) processes are included in the ME. Next, we study the effect of cotunneling and energy-dependent lead couplings on the heat currents in a system of two CCQDs. We find that cotunneling processes (i) can dominate the off-resonant heat currents at low temperature and bias compared to the interdot interaction, and (ii) give rise to a pronounced reduction of the cooling power achievable with the recently demonstrated Maxwell's demon cooling mechanism. Furthermore, we demonstrate that the cooling power can be boosted significantly by carefully engineering the energy dependence of the lead couplings to filter out undesired transport processes. Our findings emphasize the importance of higher-order cotunneling processes as well as engineered energy-dependent lead couplings in the optimization of the thermoelectric performance of CCQD systems.

Quantum Fisher information of the GHZ state due to classical phase noise lasers under non-Markovian environment

NASA Astrophysics Data System (ADS)

Chen, Yu; Zou, Jian; Yang, Zi-Yi; Li, Longwu; Li, Hai; Shao, Bin

2016-08-01

The dynamics of N-qubit GHZ state quantum Fisher information (QFI) under phase noise lasers (PNLs) driving is investigated in terms of non-Markovian master equation. We first investigate the non-Markovian dynamics of the QFI of N-qubit GHZ state and show that when the ratio of the PNL rate and the system-environment coupling strength is very small, the oscillations of the QFIs decay slower which corresponds to the non-Markovian region; yet when it becomes large, the QFIs monotonously decay which corresponds to the Markovian region. When the atom number N increases, QFIs in both regions decay faster. We further find that the QFI flow disappears suddenly followed by a sudden birth depending on the ratio of the PNL rate and the system-environment coupling strength and the atom number N, which unveil a fundamental connection between the non-Markovian behaviors and the parameters of system-environment couplings. We discuss two optimal positive operator-valued measures (POVMs) for two different strategies of our model and find the condition of the optimal measurement. At last, we consider the QFI of two atoms with qubit-qubit interaction under random telegraph noises (RTNs).

Formation and evolution of multimodal size distributions of InAs/GaAs quantum dots

NASA Astrophysics Data System (ADS)

Pohl, U. W.; Pötschke, K.; Schliwa, A.; Lifshits, M. B.; Shchukin, V. A.; Jesson, D. E.; Bimberg, D.

2006-05-01

Self-organized formation and evolution of quantum dot (QD) ensembles with a multimodal size distribution is reported. Such ensembles form after fast deposition near the critical thickness during a growth interruption (GRI) prior to cap layer growth and consist of pure InAs truncated pyramids with heights varying in steps of complete InAs monolayers, thereby creating well-distinguishable sub-ensembles. Ripening during GRI manifests itself by an increase of sub-ensembles of larger QDs at the expense of sub-ensembles of smaller ones, leaving the wetting layer unchanged. The dynamics of the multimodal QD size distribution is theoretically described using a kinetic approach. Starting from a broad distribution of flat QDs, a predominantly vertical growth is found due to strain-induced barriers for nucleation of a next atomic layer on different facets. QDs having initially a shorter base length attain a smaller height, accounting for the experimentally observed sub-ensemble structure. The evolution of the distribution is described by a master equation, which accounts for growth or dissolution of the QDs by mass exchange between the QDs and the adatom sea. The numerical solution is in good agreement with the measured dynamics.

Fermionic reaction coordinates and their application to an autonomous Maxwell demon in the strong-coupling regime

NASA Astrophysics Data System (ADS)

Strasberg, Philipp; Schaller, Gernot; Schmidt, Thomas L.; Esposito, Massimiliano

2018-05-01

We establish a theoretical method which goes beyond the weak-coupling and Markovian approximations while remaining intuitive, using a quantum master equation in a larger Hilbert space. The method is applicable to all impurity Hamiltonians tunnel coupled to one (or multiple) baths of free fermions. The accuracy of the method is in principle not limited by the system-bath coupling strength, but rather by the shape of the spectral density and it is especially suited to study situations far away from the wide-band limit. In analogy to the bosonic case, we call it the fermionic reaction coordinate mapping. As an application, we consider a thermoelectric device made of two Coulomb-coupled quantum dots. We pay particular attention to the regime where this device operates as an autonomous Maxwell demon shoveling electrons against the voltage bias thanks to information. Contrary to previous studies, we do not rely on a Markovian weak-coupling description. Our numerical findings reveal that in the regime of strong coupling and non-Markovianity, the Maxwell demon is often doomed to disappear except in a narrow parameter regime of small power output.

Surface hopping with a manifold of electronic states. II. Application to the many-body Anderson-Holstein model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dou, Wenjie; Subotnik, Joseph E.; Nitzan, Abraham

We investigate a simple surface hopping (SH) approach for modeling a single impurity level coupled to a single phonon and an electronic (metal) bath (i.e., the Anderson-Holstein model). The phonon degree of freedom is treated classically with motion along–and hops between–diabatic potential energy surfaces. The hopping rate is determined by the dynamics of the electronic bath (which are treated implicitly). For the case of one electronic bath, in the limit of small coupling to the bath, SH recovers phonon relaxation to thermal equilibrium and yields the correct impurity electron population (as compared with numerical renormalization group). For the case ofmore » out of equilibrium dynamics, SH current-voltage (I-V) curve is compared with the quantum master equation (QME) over a range of parameters, spanning the quantum region to the classical region. In the limit of large temperature, SH and QME agree. Furthermore, we can show that, in the limit of low temperature, the QME agrees with real-time path integral calculations. As such, the simple procedure described here should be useful in many other contexts.« less

Cardiac cell: a biological laser?

PubMed

Chorvat, D; Chorvatova, A

2008-04-01

We present a new concept of cardiac cells based on an analogy with lasers, practical implementations of quantum resonators. In this concept, each cardiac cell comprises a network of independent nodes, characterised by a set of discrete energy levels and certain transition probabilities between them. Interaction between the nodes is given by threshold-limited energy transfer, leading to quantum-like behaviour of the whole network. We propose that in cardiomyocytes, during each excitation-contraction coupling cycle, stochastic calcium release and the unitary properties of ionic channels constitute an analogue to laser active medium prone to "population inversion" and "spontaneous emission" phenomena. This medium, when powered by an incoming threshold-reaching voltage discharge in the form of an action potential, responds to the calcium influx through L-type calcium channels by stimulated emission of Ca2+ ions in a coherent, synchronised and amplified release process known as calcium-induced calcium release. In parallel, phosphorylation-stimulated molecular amplification in protein cascades adds tuneable features to the cells. In this framework, the heart can be viewed as a coherent network of synchronously firing cardiomyocytes behaving as pulsed laser-like amplifiers, coupled to pulse-generating pacemaker master-oscillators. The concept brings a new viewpoint on cardiac diseases as possible alterations of "cell lasing" properties.

Probing different regimes of strong field light-matter interaction with semiconductor quantum dots and few cavity photons

NASA Astrophysics Data System (ADS)

Hargart, F.; Roy-Choudhury, K.; John, T.; Portalupi, S. L.; Schneider, C.; Höfling, S.; Kamp, M.; Hughes, S.; Michler, P.

2016-12-01

In this work we present an extensive experimental and theoretical investigation of different regimes of strong field light-matter interaction for cavity-driven quantum dot (QD) cavity systems. The electric field enhancement inside a high-Q micropillar cavity facilitates exceptionally strong interaction with few cavity photons, enabling the simultaneous investigation for a wide range of QD-laser detuning. In case of a resonant drive, the formation of dressed states and a Mollow triplet sideband splitting of up to 45 μeV is measured for a mean cavity photon number < {n}c> ≤slant 1. In the asymptotic limit of the linear AC Stark effect we systematically investigate the power and detuning dependence of more than 400 QDs. Some QD-cavity systems exhibit an unexpected anomalous Stark shift, which can be explained by an extended dressed 4-level QD model. We provide a detailed analysis of the QD-cavity systems properties enabling this novel effect. The experimental results are successfully reproduced using a polaron master equation approach for the QD-cavity system, which includes the driving laser field, exciton-cavity and exciton-phonon interactions.

Tunable plasmons in atomically thin gold nanodisks

NASA Astrophysics Data System (ADS)

Manjavacas, Alejandro; Garcia de Abajo, Javier

2015-03-01

The ability to modulate light at high speeds is of paramount importance for telecommunications, information processing, and medical imaging technologies. This has stimulated intense efforts to master optoelectronic switching at visible and near-infrared (vis-NIR) frequencies, although coping with current computer speeds in integrated architectures still remains a major challenge. Here we show that atomically thin noble metal nanoislands can extend optical modulation to the vis-NIR spectral range. We find plasmons in thin metal nanodisks to produce similar absorption cross-sections as spherical particles of the same diameter. Using realistic levels of electrical doping, plasmons are shifted by about half their width, thus leading to a factor-of-two change in light absorption. These results are supported by a microscopic quantum-mechanical calculations based on the random-phase approximation (RPA), which we compare with classical simulations obtained solving Maxwell's equations using tabulated dielectric functions. Both approaches result in an excellent agreement for nanodisks with diameters above 13 nm, although quantum confinement and nonlocal effects play an important role for smaller sizes. A.M. acknowledges financial support from the Welch foundation through the J. Evans Attwell-Welch Postdoctoral Fellowship Program of the Smalley Institute of Rice University (Grant L-C-004).

Quantum dynamics in strong fluctuating fields

NASA Astrophysics Data System (ADS)

Goychuk, Igor; Hänggi, Peter

A large number of multifaceted quantum transport processes in molecular systems and physical nanosystems, such as e.g. nonadiabatic electron transfer in proteins, can be treated in terms of quantum relaxation processes which couple to one or several fluctuating environments. A thermal equilibrium environment can conveniently be modelled by a thermal bath of harmonic oscillators. An archetype situation provides a two-state dissipative quantum dynamics, commonly known under the label of a spin-boson dynamics. An interesting and nontrivial physical situation emerges, however, when the quantum dynamics evolves far away from thermal equilibrium. This occurs, for example, when a charge transferring medium possesses nonequilibrium degrees of freedom, or when a strong time-dependent control field is applied externally. Accordingly, certain parameters of underlying quantum subsystem acquire stochastic character. This may occur, for example, for the tunnelling coupling between the donor and acceptor states of the transferring electron, or for the corresponding energy difference between electronic states which assume via the coupling to the fluctuating environment an explicit stochastic or deterministic time-dependence. Here, we review the general theoretical framework which is based on the method of projector operators, yielding the quantum master equations for systems that are exposed to strong external fields. This allows one to investigate on a common basis, the influence of nonequilibrium fluctuations and periodic electrical fields on those already mentioned dynamics and related quantum transport processes. Most importantly, such strong fluctuating fields induce a whole variety of nonlinear and nonequilibrium phenomena. A characteristic feature of such dynamics is the absence of thermal (quantum) detailed balance.ContentsPAGE1. Introduction5262. Quantum dynamics in stochastic fields531 2.1. Stochastic Liouville equation531 2.2. Non-Markovian vs. Markovian discrete state fluctuations531 2.3. Averaging the quantum propagator533  2.3.1. Kubo oscillator535  2.3.2. Averaged dynamics of two-level quantum systems exposed to two-state stochastic fields537 2.4. Projection operator method: a primer5403. Two-state quantum dynamics in periodic fields542 3.1. Coherent destruction of tunnelling542 3.2. Driving-induced tunnelling oscillations (DITO)5434. Dissipative quantum dynamics in strong time-dependent fields544 4.1. General formalism544  4.1.1. Weak-coupling approximation545  4.1.2. Markovian approximation: Generalised Redfield Equations5475. Application I: Quantum relaxation in driven, dissipative two-level systems548 5.1. Decoupling approximation for fast fluctuating energy levels550  5.1.1. Control of quantum rates551  5.1.2. Stochastic cooling and inversion of level populations552  5.1.3. Emergence of an effective energy bias553 5.2. Quantum relaxation in strong periodic fields554 5.3. Approximation of time-dependent rates554 5.4. Exact averaging for dichotomous Markovian fluctuations5556. Application II: Driven electron transfer within a spin-boson description557 6.1. Curve-crossing problems with dissipation558 6.2. Weak system-bath coupling559 6.3. Beyond weak-coupling theory: Strong system-bath coupling563  6.3.1. Fast fluctuating energy levels565  6.3.2. Exact averaging over dichotomous fluctuations of the energy levels566  6.3.3. Electron transfer in fast oscillating periodic fields567  6.3.4. Dichotomously fluctuating tunnelling barrier5687. Quantum transport in dissipative tight-binding models subjected tostrong external fields569 7.1. Noise-induced absolute negative mobility571 7.2. Dissipative quantum rectifiers573 7.3. Limit of vanishing dissipation575 7.4. Case of harmonic mixing drive5758. Summary576Acknowledgements578References579

Simultaneous continuous measurement of non-commuting observables and correlation in qubit trajectories

NASA Astrophysics Data System (ADS)

Chantasri, Areeya; Jordan, Andrew

We consider the continuous quantum measurement of two or more non-commuting observables of a single qubit. Examples are presented for the measurement of two observables which can be mapped to two measurement axes on the Bloch sphere; a special case being the measurement along the X and Z bases. The qubit dynamics is described by the stochastic master equations which include the effect of decoherence and measurement inefficiencies. We investigate the qubit trajectories, their most likely paths, and their correlation functions using the stochastic path integral formalism. The correlation functions in qubit trajectories can be derived exactly for a special case and perturbatively for general cases. The theoretical predictions are compared with numerical simulations, as well as with trajectory data from the transmon superconducting qubit experiments.

Relaxation dynamics of C60

NASA Astrophysics Data System (ADS)

Walsh, Tiffany R.; Wales, David J.

1998-10-01

The relaxation dynamics of C60 from high-energy isomers to Buckminsterfullerene is examined using a master equation approach. An exhaustive catalog of the C60 fullerene isomers containing only five- and six-membered rings is combined with knowledge of the Stone-Wales rearrangements that connect all such isomers. Full geometry optimizations have been performed for all the minima and the transition states which connect them up to six Stone-Wales steps away from the global minimum. A density-functional tight-binding potential was employed to provide a quantum mechanical description of the bonding. The resulting picture of the potential energy landscape reveals a "weeping willow" structure which offers a clear explanation for the relatively long relaxation times observed experimentally. We also predict the most important transient local minima on the annealing pathway.

Nucleation versus instability race in strained films

NASA Astrophysics Data System (ADS)

Liu, Kailang; Berbezier, Isabelle; David, Thomas; Favre, Luc; Ronda, Antoine; Abbarchi, Marco; Voorhees, Peter; Aqua, Jean-Noël

2017-10-01

Under the generic term "Stranski-Krastanov" are grouped two different growth mechanisms of SiGe quantum dots. They result from the self-organized Asaro-Tiller-Grinfel'd (ATG) instability at low strain, while at high strain, from a stochastic nucleation. While these regimes are well known, we elucidate here the origin of the transition between these two pathways thanks to a joint theoretical and experimental work. Nucleation is described within the master equation framework. By comparing the time scales for ATG instability development and three-dimensional (3D) nucleation onset, we demonstrate that the transition between these two regimes is simply explained by the crossover between their divergent evolutions. Nucleation exhibits a strong exponential deviation at low strain while ATG behaves only algebraically. The associated time scale varies with exp(1 /x4) for nucleation, while it only behaves as 1 /x8 for the ATG instability. Consequently, at high (low) strain, nucleation (instability) occurs faster and inhibits the alternate evolution. It is then this different kinetic evolution which explains the transition from one regime to the other. Such a kinetic view of the transition between these two 3D growth regimes was not provided before. The crossover between nucleation and ATG instability is found to occur both experimentally and theoretically at a Ge composition around 50% in the experimental conditions used here. Varying the experimental conditions and/or the system parameters does not allow us to suppress the transition. This means that the SiGe quantum dots always grow via ATG instability at low strain and nucleation at high strain. This result is important for the self-organization of quantum dots.

PREFACE: Quantum Information, Communication, Computation and Cryptography

NASA Astrophysics Data System (ADS)

Benatti, F.; Fannes, M.; Floreanini, R.; Petritis, D.

2007-07-01

The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12-23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy-Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable systems, the second by T Prosen, discussing chaos and complexity in quantum systems. Both topics have theoretical as well as experimental relevance and are likely to witness a fast growing development in the near future. The remaining contributions present more specific and very recent results. They involve the study of the structure of quantum states and their estimation (B Baumgartner et al, C King et al, S Olivares et al, D Petz et al and W van Dam et al), of entanglement generation and its quantification (G Brida et al, F Ciccarello et al, G Costantini et al, O Romero-Isart et al, D Rossini et al, A Serafini et al and D Vitali et al), of randomness related effects on entanglement behaviour (I Akhalwaya et al, O Dahlsten et al and L Viola et al), and of abstract and applied aspects of quantum computation and communication (K Audenart, G M D'Ariano et al, N Datta et al, L C Kwek et al and M Nathanson et al). We would like to express our gratitude to the European Commission, the Abdus Salam ICTP, SISSA and Eurotech SpA (Amaro, Udine, Italy) for financial and/or logistic support. Special thanks also go to the workshop secretary Marina De Comelli, and the secretaries of the Department of Theoretical Physics, University of Trieste, Sabrina Gaspardis and Rosita Glavina for their precious help and assistance.

CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

NASA Astrophysics Data System (ADS)

Nowak, K. M.; Ohta, T.; Suganuma, T.; Fujimoto, J.; Mizoguchi, H.; Sumitani, A.; Endo, A.

2013-12-01

It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.

Decoherence of odd compass states in the phase-sensitive amplifying/dissipating environment

NASA Astrophysics Data System (ADS)

Dodonov, V. V.; Valverde, C.; Souza, L. S.; Baseia, B.

2016-08-01

We study the evolution of odd compass states (specific superpositions of four coherent states), governed by the standard master equation with phase-sensitive amplifying/attenuating terms, in the presence of a Hamiltonian describing a parametric degenerate linear amplifier. Explicit expressions for the time-dependent Wigner function are obtained. The time of disappearance of the so called ;sub-Planck structures; is calculated using the negative value of the Wigner function at the origin of phase space. It is shown that this value rapidly decreases during a short ;conventional interference degradation time; (CIDT), which is inversely proportional to the size of quantum superposition, provided the anti-Hermitian terms in the master equation are of the same order (or stronger) as the Hermitian ones (governing the parametric amplification). The CIDT is compared with the final positivization time (FPT), when the Wigner function becomes positive. It appears that the FPT does not depend on the size of superpositions, moreover, it can be much bigger in the amplifying media than in the attenuating ones. Paradoxically, strengthening the Hamiltonian part results in decreasing the CIDT, so that the CIDT almost does not depend on the size of superpositions in the asymptotical case of very weak reservoir coupling. We also analyze the evolution of the Mandel factor, showing that for some sets of parameters this factor remains significantly negative, even when the Wigner function becomes positive.

Core molecule dependence of energy migration in phenylacetylene nanostar dendrimers: Ab initio molecular orbital-configuration interaction based quantum master equation study

NASA Astrophysics Data System (ADS)

Kishi, Ryohei; Minami, Takuya; Fukui, Hitoshi; Takahashi, Hideaki; Nakano, Masayoshi

2008-06-01

The core molecule dependence of energy (exciton) migration in phenylacetylene nanostar dendrimers is investigated using the ab initio molecular orbital (MO)-configuration interaction based quantum master equation approach. We examine three kinds of core molecular species, i.e., benzene, anthracene, and pentacene, with different highest occupied MO-lowest unoccupied MO (HOMO-LUMO) gaps, which lead to different orbital interactions between the dendron parts and the core molecule. The nanostars bearing anthracene and pentacene cores are characterized by multistep exciton states with spatially well-segmented distributions: The exciton distributions of high-lying exciton states are spatially localized well in the periphery region, whereas those of low-lying exciton states are done in the core region. On the other hand, for the nanostar bearing benzene core, which also has multistep exciton states, the spatial exciton distributions of low-lying exciton states are delocalized over the dendron and the core regions. It is found that the former nanostars exhibit nearly complete exciton migration from the periphery to the core molecule in contrast to the latter one, in which significant exciton distribution remains in the dendron parts attached to the core after the exciton relaxation, although all these dendrimers exhibit fast exciton relaxation from the initially populated states. It is predicted from the analysis based on the MO correlation diagrams and the relative relaxation factor that the complete exciton migration to the core occurs not only when the HOMO-LUMO gap of the core molecule is nearly equal to that of the dendron parts attached to the core (anthracene case) but also when fairly smaller than that (pentacene case), whereas the complete migration is not achieved when the HOMO-LUMO gap of the core is larger than that of the dendron parts (benzene case). These results suggest that the fast and complete exciton migration of real dendrimers could be realized by adjusting the HOMO-LUMO gap of the core molecule to be smaller than that of dendron parts, although there exist more complicated relaxation processes as compared to simple dendritic aggregate models studied so far.

Using concept building in optics to improve student research skills

NASA Astrophysics Data System (ADS)

Masters, Mark F.; Grove, Timothy T.

2014-07-01

Optics is a core component of an undergraduate physics degree. Not only is optics a fascinating topic on its own, but a good understanding of optics helps students gain valuable insight into more complex topics. A working knowledge of optics is vital for the experimental investigation of astronomy, quantum mechanics, and a host of other research endeavors involving optical measurements. Research is also a critical part of a student's education. Participation in research brings tremendous benefits to a student. So what do the students gain by participation in research? They learn independence. They learn how to plan a project. They learn the process of discovery. They learn that all answers are not always found on the internet, from professors, in books and publications (in that order). Research makes the "book" learning real. But what skills do the students need to be able to do research? Most of our experimental research opportunities involve optics. We have students working on investigations that range from atomic spectroscopy of rubidium to Rayleigh scattering to optical tweezers to quantum optics. When a student starts research, we want them to be ready to go. We don't want them to have to relearn material (or for us to reteach material) that they should already have mastered in earlier classes.

Applicability of transfer tensor method for open quantum system dynamics.

PubMed

Gelzinis, Andrius; Rybakovas, Edvardas; Valkunas, Leonas

2017-12-21

Accurate simulations of open quantum system dynamics is a long standing issue in the field of chemical physics. Exact methods exist, but are costly, while perturbative methods are limited in their applicability. Recently a new black-box type method, called transfer tensor method (TTM), was proposed [J. Cerrillo and J. Cao, Phys. Rev. Lett. 112, 110401 (2014)]. It allows one to accurately simulate long time dynamics with a numerical cost of solving a time-convolution master equation, provided many initial system evolution trajectories are obtained from some exact method beforehand. The possible time-savings thus strongly depend on the ratio of total versus initial evolution lengths. In this work, we investigate the parameter regimes where an application of TTM would be most beneficial in terms of computational time. We identify several promising parameter regimes. Although some of them correspond to cases when perturbative theories could be expected to perform well, we find that the accuracy of such approaches depends on system parameters in a more complex way than it is commonly thought. We propose that the TTM should be applied whenever system evolution is expected to be long and accuracy of perturbative methods cannot be ensured or in cases when the system under consideration does not correspond to any single perturbative regime.

Coupled superconducting qudit-resonator system: Energy spectrum, state population, and state transition under microwave drive

NASA Astrophysics Data System (ADS)

Liu, W. Y.; Xu, H. K.; Su, F. F.; Li, Z. Y.; Tian, Ye; Han, Siyuan; Zhao, S. P.

2018-03-01

Superconducting quantum multilevel systems coupled to resonators have recently been considered in some applications such as microwave lasing and high-fidelity quantum logical gates. In this work, using an rf-SQUID type phase qudit coupled to a microwave coplanar waveguide resonator, we study both theoretically and experimentally the energy spectrum of the system when the qudit level spacings are varied around the resonator frequency by changing the magnetic flux applied to the qudit loop. We show that the experimental result can be well described by a theoretical model that extends from the usual two-level Jaynes-Cummings system to the present four-level system. It is also shown that due to the small anharmonicity of the phase device a simplified model capturing the leading state interactions fits the experimental spectra very well. Furthermore we use the Lindblad master equation containing various relaxation and dephasing processes to calculate the level populations in the simpler qutrit-resonator system, which allows a clear understanding of the dynamics of the system under the microwave drive. Our results help to better understand and perform the experiments of coupled multilevel and resonator systems and can be applied in the case of transmon or Xmon qudits having similar anharmonicity to the present phase device.

Energy-efficient quantum frequency estimation

NASA Astrophysics Data System (ADS)

Liuzzo-Scorpo, Pietro; Correa, Luis A.; Pollock, Felix A.; Górecka, Agnieszka; Modi, Kavan; Adesso, Gerardo

2018-06-01

The problem of estimating the frequency of a two-level atom in a noisy environment is studied. Our interest is to minimise both the energetic cost of the protocol and the statistical uncertainty of the estimate. In particular, we prepare a probe in a ‘GHZ-diagonal’ state by means of a sequence of qubit gates applied on an ensemble of n atoms in thermal equilibrium. Noise is introduced via a phenomenological time-non-local quantum master equation, which gives rise to a phase-covariant dissipative dynamics. After an interval of free evolution, the n-atom probe is globally measured at an interrogation time chosen to minimise the error bars of the final estimate. We model explicitly a measurement scheme which becomes optimal in a suitable parameter range, and are thus able to calculate the total energetic expenditure of the protocol. Interestingly, we observe that scaling up our multipartite entangled probes offers no precision enhancement when the total available energy {\\boldsymbol{ \\mathcal E }} is limited. This is at stark contrast with standard frequency estimation, where larger probes—more sensitive but also more ‘expensive’ to prepare—are always preferred. Replacing {\\boldsymbol{ \\mathcal E }} by the resource that places the most stringent limitation on each specific experimental setup, would thus help to formulate more realistic metrological prescriptions.

Computed rate coefficients and product yields for c-C5H5 + CH3 --> products.

PubMed

Sharma, Sandeep; Green, William H

2009-08-06

Using quantum chemical methods, we have explored the region of the C6H8 potential energy surface that is relevant in predicting the rate coefficients of various wells and major product channels following the reaction between cyclopentadienyl radical and methyl radical, c-C5H5 + CH3. Variational transition state theory is used to calculate the high-pressure-limit rate coefficient for all of the barrierless reactions. RRKM theory and the master equation are used to calculate the pressure dependent rate coefficients for 12 reactions. The calculated results are compared with the limited experimental data available in the literature and the agreement between the two is quite good. All of the rate coefficients calculated in this work are tabulated and can be used in building detailed chemical kinetic models.

Ab initio thermal rate calculations of HO + HO = O(3P) + H2O reaction and isotopologues.

PubMed

Nguyen, Thanh Lam; Stanton, John F

2013-04-04

The forward and reverse reactions, HO + HO ⇌ O((3)P) + H2O, which play roles in both combustion and laboratory studies, were theoretically characterized with a master equation approach to compute thermal reaction rate constants at both the low and high pressure limits. Our ab initio k(T) results for the title reaction and two isotopic variants agree very well with experiments (within 15%) over a wide temperature range. The calculated reaction rate shows a distinctly non-Arrhenius behavior and a strong curvature consistent with the experiment. This characteristic behavior is due to effects of positive barrier height and quantum mechanical tunneling. Tunneling is very important and contributes more than 70% of total reaction rate at room temperature. A prereactive complex is also important in the overall reaction scheme.

Relational symplectic groupoid quantization for constant poisson structures

NASA Astrophysics Data System (ADS)

Cattaneo, Alberto S.; Moshayedi, Nima; Wernli, Konstantin

2017-09-01

As a detailed application of the BV-BFV formalism for the quantization of field theories on manifolds with boundary, this note describes a quantization of the relational symplectic groupoid for a constant Poisson structure. The presence of mixed boundary conditions and the globalization of results are also addressed. In particular, the paper includes an extension to space-times with boundary of some formal geometry considerations in the BV-BFV formalism, and specifically introduces into the BV-BFV framework a "differential" version of the classical and quantum master equations. The quantization constructed in this paper induces Kontsevich's deformation quantization on the underlying Poisson manifold, i.e., the Moyal product, which is known in full details. This allows focussing on the BV-BFV technology and testing it. For the inexperienced reader, this is also a practical and reasonably simple way to learn it.

Dynamics of entropic uncertainty for atoms immersed in thermal fluctuating massless scalar field

NASA Astrophysics Data System (ADS)

Huang, Zhiming

2018-04-01

In this article, the dynamics of quantum memory-assisted entropic uncertainty relation for two atoms immersed in a thermal bath of fluctuating massless scalar field is investigated. The master equation that governs the system evolution process is derived. It is found that the mixedness is closely associated with entropic uncertainty. For equilibrium state, the tightness of uncertainty vanishes. For the initial maximum entangled state, the tightness of uncertainty undergoes a slight increase and then declines to zero with evolution time. It is found that temperature can increase the uncertainty, but two-atom separation does not always increase the uncertainty. The uncertainty evolves to different relatively stable values for different temperatures and converges to a fixed value for different two-atom distances with evolution time. Furthermore, weak measurement reversal is employed to control the entropic uncertainty.

Basic mechanisms in the laser control of non-Markovian dynamics

NASA Astrophysics Data System (ADS)

Puthumpally-Joseph, R.; Mangaud, E.; Chevet, V.; Desouter-Lecomte, M.; Sugny, D.; Atabek, O.

2018-03-01

Referring to a Fano-type model qualitative analogy we develop a comprehensive basic mechanism for the laser control of the non-Markovian bath response and fully implement it in a realistic control scheme, in strongly coupled open quantum systems. Converged hierarchical equations of motion are worked out to numerically solve the master equation of a spin-boson Hamiltonian to reach the reduced electronic density matrix of a heterojunction in the presence of strong terahertz laser pulses. Robust and efficient control is achieved increasing by a factor of 2 the non-Markovianity measured by the time evolution of the volume of accessible states. The consequences of such fields on the central system populations and coherence are examined, putting the emphasis on the relation between the increase of non-Markovianity and the slowing down of decoherence processes.

Multiphoton amplitude in a constant background field

NASA Astrophysics Data System (ADS)

Ahmad, Aftab; Ahmadiniaz, Naser; Corradini, Olindo; Kim, Sang Pyo; Schubert, Christian

2018-01-01

In this contribution, we present our recent compact master formulas for the multiphoton amplitudes of a scalar propagator in a constant background field using the worldline fomulation of quantum field theory. The constant field has been included nonperturbatively, which is crucial for strong external fields. A possible application is the scattering of photons by electrons in a strong magnetic field, a process that has been a subject of great interest since the discovery of astrophysical objects like radio pulsars, which provide evidence that magnetic fields of the order of 1012G are present in nature. The presence of a strong external field leads to a strong deviation from the classical scattering amplitudes. We explicitly work out the Compton scattering amplitude in a magnetic field, which is a process of potential relevance for astrophysics. Our final result is compact and suitable for numerical integration.

EDITORIAL: Focus on Quantum Information and Many-Body Theory

NASA Astrophysics Data System (ADS)

Eisert, Jens; Plenio, Martin B.

2010-02-01

Quantum many-body models describing natural systems or materials and physical systems assembled piece by piece in the laboratory for the purpose of realizing quantum information processing share an important feature: intricate correlations that originate from the coherent interaction between a large number of constituents. In recent years it has become manifest that the cross-fertilization between research devoted to quantum information science and to quantum many-body physics leads to new ideas, methods, tools, and insights in both fields. Issues of criticality, quantum phase transitions, quantum order and magnetism that play a role in one field find relations to the classical simulation of quantum systems, to error correction and fault tolerance thresholds, to channel capacities and to topological quantum computation, to name but a few. The structural similarities of typical problems in both fields and the potential for pooling of ideas then become manifest. Notably, methods and ideas from quantum information have provided fresh approaches to long-standing problems in strongly correlated systems in the condensed matter context, including both numerical methods and conceptual insights. Focus on quantum information and many-body theory Contents TENSOR NETWORKS Homogeneous multiscale entanglement renormalization ansatz tensor networks for quantum critical systems M Rizzi, S Montangero, P Silvi, V Giovannetti and Rosario Fazio Concatenated tensor network states R Hübener, V Nebendahl and W Dür Entanglement renormalization in free bosonic systems: real-space versus momentum-space renormalization group transforms G Evenbly and G Vidal Finite-size geometric entanglement from tensor network algorithms Qian-Qian Shi, Román Orús, John Ove Fjærestad and Huan-Qiang Zhou Characterizing symmetries in a projected entangled pair state D Pérez-García, M Sanz, C E González-Guillén, M M Wolf and J I Cirac Matrix product operator representations B Pirvu, V Murg, J I Cirac and F Verstraete SIMULATION AND DYNAMICS A quantum differentiation of k-SAT instances B Tamir and G Ortiz Classical Ising model test for quantum circuits Joseph Geraci and Daniel A Lidar Exact matrix product solutions in the Heisenberg picture of an open quantum spin chain S R Clark, J Prior, M J Hartmann, D Jaksch and M B Plenio Exact solution of Markovian master equations for quadratic Fermi systems: thermal baths, open XY spin chains and non-equilibrium phase transition Tomaž Prosen and Bojan Žunkovič Quantum kinetic Ising models R Augusiak, F M Cucchietti, F Haake and M Lewenstein ENTANGLEMENT AND SPECTRAL PROPERTIES Ground states of unfrustrated spin Hamiltonians satisfy an area law Niel de Beaudrap, Tobias J Osborne and Jens Eisert Correlation density matrices for one-dimensional quantum chains based on the density matrix renormalization group W Münder, A Weichselbaum, A Holzner, Jan von Delft and C L Henley The invariant-comb approach and its relation to the balancedness of multipartite entangled states Andreas Osterloh and Jens Siewert Entanglement scaling of fractional quantum Hall states through geometric deformations Andreas M Läuchli, Emil J Bergholtz and Masudul Haque Entanglement versus gap for one-dimensional spin systems Daniel Gottesman and M B Hastings Entanglement spectra of critical and near-critical systems in one dimension F Pollmann and J E Moore Macroscopic bound entanglement in thermal graph states D Cavalcanti, L Aolita, A Ferraro, A García-Saez and A Acín Entanglement at the quantum phase transition in a harmonic lattice Elisabeth Rieper, Janet Anders and Vlatko Vedral Multipartite entanglement and frustration P Facchi, G Florio, U Marzolino, G Parisi and S Pascazio Entropic uncertainty relations—a survey Stephanie Wehner and Andreas Winter Entanglement in a spin system with inverse square statistical interaction D Giuliano, A Sindona, G Falcone, F Plastina and L Amico APPLICATIONS Time-dependent currents of one-dimensional bosons in an optical lattice J Schachenmayer, G Pupillo and A J Daley Implementing quantum gates using the ferromagnetic spin-J XXZ chain with kink boundary conditions Tom Michoel, Jaideep Mulherkar and Bruno Nachtergaele Long-distance entanglement in many-body atomic and optical systems Salvatore M Giampaolo and Fabrizio Illuminati QUANTUM MEMORIES AND TOPOLOGICAL ORDER Thermodynamic stability criteria for a quantum memory based on stabilizer and subsystem codes Stefano Chesi, Daniel Loss, Sergey Bravyi and Barbara M Terhal Topological color codes and two-body quantum lattice Hamiltonians M Kargarian, H Bombin and M A Martin-Delgado RENORMALIZATION Local renormalization method for random systems O Gittsovich, R Hübener, E Rico and H J Briegel

EDITORIAL: CAMOP: Quantum Non-Stationary Systems CAMOP: Quantum Non-Stationary Systems

NASA Astrophysics Data System (ADS)

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 QED. Another rapidly growing research field (although its origin can be traced to the beginning of the 1980s) is the quantum control of evolution at the microscopic level. These examples show that quantum non-stationary systems continue to be a living and very interesting part of quantum physics, uniting researchers from many different areas. Thus it is no mere chance that several special scientific meetings devoted to these topics have been organized recently. One was the international seminar 'Time-Dependent Phenomena in Quantum Mechanics' organized by Manfred Kleber and Tobias Kramer in 2007 at Blaubeuren, Germany. The proceedings of that event were published in 2008 as volume 99 of Journal of Physics: Conference Series. Another recent meeting was the International Workshop on Quantum Non-Stationary Systems, held on 19-23 October 2009 at the International Center for Condensed Matter Physics (ICCMP) in Brasilia, Brazil. It was organized and directed by Victor Dodonov (Institute of Physics, University of Brasilia, Brazil), Vladimir Man'ko (P N Lebedev Physical Institute, Moscow, Russia) and Salomon Mizrahi (Physics Department, Federal University of Sao Carlos, Brazil). This event was accompanied by a satellite workshop 'Quantum Dynamics in Optics and Matter', organized by Salomon Mizrahi and Victor Dodonov on 25-26 October 2009 at the Physics Department of the Federal University of Sao Carlos, Brazil. These two workshops, supported by the Brazilian federal agencies CAPES and CNPq and the local agencies FAP-DF and FAPESP, were attended by more than 120 participants from 16 countries. Almost 50 invited talks and 20 poster presentations covered a wide area of research in quantum mechanics, quantum optics and quantum information. This special issue of CAMOP/Physica Scripta contains contributions presented by some invited speakers and participants of the workshop in Brasilia. Although they do not cover all of the wide spectrum of problems related to quantum non-stationary systems, they nonetheless show some general trends. However, readers should remember that these comments represent the personal points of view of their authors. About a third of the comments are devoted to the evolution of quantum systems in the presence of dissipation or other sources of decoherence. This area, started by Landau in 1927, still contains many extremely interesting and unsolved problems. Here they are discussed in view of such different applications as the dynamics of quantum entanglement, cavity QED, optomechanics and the dynamical Casimir effect. Another group of comments deals with different (e.g. geometrical, tomographic, PT-symmetric) approaches to the dynamics of quantum systems, which have been developed in the past two decades. In particular, the problem of transition from quantum to classical description is considered and the inequalities generalizing the standard uncertainty relations are discussed in this connection. Three comments are devoted to the applications of nonclassical states, analytic representations and the algebraic techniques for resolving problems in quantum information and quantum statistical physics. The other contributions are related to different aspects of the dynamics of concrete physical systems, such as the wave-packet approach to the description of transport phenomena in mesoscopic systems, tunneling phenomena in low-dimensional semiconductor structures and resonance states of two-electron quantum dots. We thank all the authors and referees for their efforts in preparing this special issue. We hope that the comments in this collection will be useful for interested readers.

Entanglement dynamics in a Kerr spacetime

NASA Astrophysics Data System (ADS)

Menezes, G.

2018-04-01

We consider the entanglement dynamics between two-level atoms in a rotating black hole background. In our model the two-atom system is envisaged as an open system coupled with a massless scalar field prepared in one of the physical vacuum states of interest. We employ the quantum master equation in the Born-Markov approximation in order to describe the time evolution of the atomic subsystem. We investigate two different states of motion for the atoms, namely static atoms and also stationary atoms with zero angular momentum. The purpose of this work is to expound the impact on the creation of entanglement coming from the combined action of the different physical processes underlying the Hawking effect and the Unruh-Starobinskii effect. We demonstrate that, in the scenario of rotating black holes, the degree of quantum entanglement is significantly modified due to the phenomenon of superradiance in comparison with the analogous cases in a Schwarzschild spacetime. In the perspective of a zero angular momentum observer (ZAMO), one is allowed to probe entanglement dynamics inside the ergosphere, since static observers cannot exist within such a region. On the other hand, the presence of superradiant modes could be a source for violation of complete positivity. This is verified when the quantum field is prepared in the Frolov-Thorne vacuum state. In this exceptional situation, we raise the possibility that the loss of complete positivity is due to the breakdown of the Markovian approximation, which means that any arbitrary physically admissible initial state of the two atoms would not be capable to hold, with time evolution, its interpretation as a physical state inasmuch as negative probabilities are generated by the dynamical map.

Fabrication et caracterisation de cristaux photoniques pour exaltation de fluorescence

NASA Astrophysics Data System (ADS)

Gascon, Annabelle

2011-12-01

In today's world, there is a pressing need for point-of-care molecular analysis that is fast, inexpensive and transportable. Lab-on-a- chips are designed to fulfill that need. They are micro-electromechanical systems (MEMS), fabricated with microelectronic techniques, that use the analytes physical properties to detect their presence in liquid samples. This detection can be performed by attaching the analyte to quantum dots. These quantum dots are semiconducting nanoparticles with narrow fluorescence band. In our project, we use a tuneable system with a two-slab photonic crystal that serves as a tuneable optical filter, detecting the presence and wavelength of these quantum dots. Photonic crystals are dielectrics with a variable refractive index, with a period near the visible light wavelength. They are called photonic crystals because they have a photonic band gap just as atomic crystals, periodic structure of atoms, have an electronic band gap. They are photonic because photons instead of electrons propagate through them. They can also enhance fluorescence from quantum dots at the photonic crystals guided resonance wavelength. My project objectives are to: (1) Fabricate two-slab photonic crystal, (2) Characterize photonic crystals, (3) Place quantum dots on photonic crystals, (4) Measure fluorescence enhancement. The device made during this project consists of a silicon wafer on which were deposited a 200 nm silicon nitride layer, then a 200 nm silicon dioxide layer and finally another 200 nm silicon nitride layer. An electron-beam lithography defines the photonic crystals and the MEMS. The photonic crystals are square lattices of holes 180 nm in diameter, at a period of 460 nm, etched through the two silicon nitride slabs. The two slabs are etched in a single step of Reactive Ion Etching (RIE). Then, the silicon under the photonic crystal is etched from the backside up to the nitride by deep-RIE. Finally, the oxide layer is removed in order to completely suspend the two-slab photonic crystal. The M EMS can change the gap between the two slabs in order to tune the guided resonance wavelength. An optical set-up is used to trace the photonic crystals transmission and reflection spectrum, in order to know the guided resonance position. A supercontinuum source illuminates the device at a normal incidence angle for wavelength between 400 nm and 800 nm. High-resolution spectra are obtained with a CCD camera spectrometer. Different types of one-slab photonic crystals are analyzed with this approach: we observe guided resonance peaks near 550 nm, 615 nm and 700 nm. Finally, a quantum dots microdrop is placed on the photonic crystal. The quantum dots emission wavelength matches with the photonic crystal guided resonance. A hyperspectral fluorescence microscope excites quantum dots between 436 nm and 483 nm, detects emission greater than 500 nm and plots a fluorescence wavelength spectrum. This set-up measures and compares the fluorescence of the quantum dots placed on and next to the photonic crystals. Our results show that the fluorescence is 30 times higher on the photonic crystals, but the fluorescence wavelength corresponds neither to the quantum dots emission nor to the photonic crystal guided resonance. In conclusion, this master thesis project demonstrates that it is possible to fabricate two-slab photonic crystals in silicon nitride and to plot their transmission and reflection spectra in order to find their guided resonance position. A fluorescence enhancement is visible, but at a different wavelength than of the quantum dots.

Decoherence of odd compass states in the phase-sensitive amplifying/dissipating environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dodonov, V.V., E-mail: vdodonov@fis.unb.br; Valverde, C.; Universidade Paulista, BR 153, km 7, 74845-090 Goiânia, GO

2016-08-15

We study the evolution of odd compass states (specific superpositions of four coherent states), governed by the standard master equation with phase-sensitive amplifying/attenuating terms, in the presence of a Hamiltonian describing a parametric degenerate linear amplifier. Explicit expressions for the time-dependent Wigner function are obtained. The time of disappearance of the so called “sub-Planck structures” is calculated using the negative value of the Wigner function at the origin of phase space. It is shown that this value rapidly decreases during a short “conventional interference degradation time” (CIDT), which is inversely proportional to the size of quantum superposition, provided the anti-Hermitianmore » terms in the master equation are of the same order (or stronger) as the Hermitian ones (governing the parametric amplification). The CIDT is compared with the final positivization time (FPT), when the Wigner function becomes positive. It appears that the FPT does not depend on the size of superpositions, moreover, it can be much bigger in the amplifying media than in the attenuating ones. Paradoxically, strengthening the Hamiltonian part results in decreasing the CIDT, so that the CIDT almost does not depend on the size of superpositions in the asymptotical case of very weak reservoir coupling. We also analyze the evolution of the Mandel factor, showing that for some sets of parameters this factor remains significantly negative, even when the Wigner function becomes positive.« less

An entrepreneurial physics method and its experimental test

NASA Astrophysics Data System (ADS)

Brown, Robert

2012-02-01

As faculty in a master's program for entrepreneurial physics and in an applied physics PhD program, I have advised upwards of 40 master and doctoral theses in industrial physics. I have been closely involved with four robust start-up manufacturing companies focused on physics high-technology and I have spent 30 years collaborating with industrial physicists on research and development. Thus I am in a position to reflect on many articles and advice columns centered on entrepreneurship. What about the goals, strategies, resources, skills, and the 10,000 hours needed to be an entrepreneur? What about business plans, partners, financing, patents, networking, salesmanship and regulatory affairs? What about learning new technology, how to solve problems and, in fact, learning innovation itself? At this point, I have my own method to propose to physicists in academia for incorporating entrepreneurship into their research lives. With this method, we do not start with a major invention or discovery, or even with a search for one. The method is based on the training we have, and the teaching we do (even quantum electrodynamics!), as physicists. It is based on the networking we build by 1) providing courses of continuing education for people working in industry and 2) through our undergraduate as well as graduate students who have gone on to work in industry. In fact, if we were to be limited to two words to describe the method, they are ``former students.'' Data from local and international medical imaging manufacturing industry are presented.

1-kW monolithic narrow linewidth linear-polarized fiber laser at 1030 nm

NASA Astrophysics Data System (ADS)

Xu, Yang; Fang, Qiang; Cui, Xuelong; Hou, Bowen; Fu, Shijie; Xie, Zhaoxin; Shi, Wei

2018-02-01

We demonstrate an all-fiberized, linear-polarized, narrow spectral linewidth laser system with kilowatts-level output power at 1030 nm in master oscillator-power amplifier (MOPA) configuration. The laser system consists of a linear-polarized, narrow linewidth ( 28 GHz) fiber laser oscillator and two stages of linear-polarized fiber amplifiers. A 925 W linear-polarized fiber laser with a polarization extinction ratio (PER) of 15.2 dB and a spectral width of 60 GHz at the central wavelength of 1030.1 nm is achieved. Owing to the setting of the appropriate parameters for the laser, no indication of Stimulate Brillouin Scattering (SBS) is observed in the system. Moreover, thanks to the excellent quantum efficiency of the laser and the thightly coiling of the active fiber in the main amplifier, the mode instability (MI) is successfully avoided. As a result, the near diffraction-limited beam quality (M2<1.3) is achieved.

Progress toward bridging from atomistic to continuum modeling to predict nuclear waste glass dissolution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zapol, Peter; Bourg, Ian; Criscenti, Louise Jacqueline

2011-10-01

This report summarizes research performed for the Nuclear Energy Advanced Modeling and Simulation (NEAMS) Subcontinuum and Upscaling Task. The work conducted focused on developing a roadmap to include molecular scale, mechanistic information in continuum-scale models of nuclear waste glass dissolution. This information is derived from molecular-scale modeling efforts that are validated through comparison with experimental data. In addition to developing a master plan to incorporate a subcontinuum mechanistic understanding of glass dissolution into continuum models, methods were developed to generate constitutive dissolution rate expressions from quantum calculations, force field models were selected to generate multicomponent glass structures and gel layers,more » classical molecular modeling was used to study diffusion through nanopores analogous to those in the interfacial gel layer, and a micro-continuum model (K{mu}C) was developed to study coupled diffusion and reaction at the glass-gel-solution interface.« less

Delay-bandwidth product of electromagnetically induced transparency media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tidstroem, Jonas; Jaenes, Peter; Andersson, L. Mauritz

2007-05-15

The limitations on the delay-bandwidth product (DBP) in an electromagnetically induced transparency medium are investigated analytically by studying the susceptibility of the system, derived through Lindblad's master equation, including dephasing. The effect of inhomogeneous broadening is treated. It is shown that the DBP for a given material is fundamentally limited by the frequency-dependent absorption, while the residual absorption limits the penetration length of a pulse. Simple expression for the optimal choice of parameters to maximize the DBP are derived. Also, the length of a device is presented as a function of DBP and control-field Rabi frequency. Supporting these results, numericalmore » calculations are carried out through the Maxwell-Bloch equations in the slowly varying envelope approximation. The results are scalable, hence they apply to the case of atoms or molecules in a gas as well as quantum dots and wells.« less

Rate processes in gas phase

NASA Technical Reports Server (NTRS)

Hansen, C. F.

1983-01-01

Reaction-rate theory and experiment are given a critical review from the engineers' point of view. Rates of heavy-particle, collision-induced reaction in gas phase are formulated in terms of the cross sections and activation energies for reaction. The effect of cross section function shape and of excited state contributions to reaction both cause the slope of Arrhenius plots to differ from the true activation energy, except at low temperature. The master equations for chemically reacting gases are introduced, and dissociation and ionization reactions are shown to proceed primarily from excited states about kT from the dissociation or ionization limit. Collision-induced vibration, vibration-rotation, and pure rotation transitions are treated, including three-dimensional effects and conservation of energy, which have usually been ignored. The quantum theory of transitions at potential surface crossing is derived, and results are found to be in fair agreement with experiment in spite of some questionable approximations involved.

Microwave Imaging Using a Tunable Reflectarray Antenna and Superradiance in Open Quantum Systems

NASA Astrophysics Data System (ADS)

Tayebi, Amin

Theory, experiment, and computation are the three paradigms for scientific discoveries. This dissertation includes work in all three areas. The first part is dedicated to the practical design and development of a microwave imaging system, a problem mostly experimental and computational in nature. The second part discusses theoretical foundations of possible future advances in quantum signal transmission. In part one, a new active microwave imaging system is proposed. At the heart of this novel system lies an electronically reconfigurable beam-scanning reflectarray antenna. The high tuning capability of the reflectarray provides a broad steering range of +/- 60 degrees in two distinct frequency bands: S and F bands. The array, combined with an external source, dynamically steers the incoming beam across this range in order to generate multi-angle projection data for target detection. The collected data is then used for image reconstruction by means of time reversal signal processing technique. Our design significantly reduces cost and operational complexities compared to traditional imaging systems. In conventional systems, the region of interest is enclosed by a costly array of transceiver antennas which additionally requires a complicated switching circuitry. The inclusion of the beam scanning array and the utilization of a single source, eliminates the need for multiple antennas and the involved circuitry. In addition, unlike conventional setups, this system is not constrained by the dimensions of the object under test. Therefore the inspection of large objects, such as extended laminate structures, composite airplane wings and wind turbine blades becomes possible. Experimental results of detection of various dielectric targets as well as detecting anomalies within them, such as defects and metallic impurities, using the imaging prototype are presented. The second part includes the theoretical consideration of three different problems: quantum transport through two different nanostructures, a solid state device suitable for quantum computing and spherical plasmonic nanoantennas and waveguides. These three physically different systems are all investigated within a single quantum theory; the effective non-Hermitian Hamiltonian framework. The non-Hermitian Hamiltonian approach is a convenient mathematical formalism for the description of open quantum systems. This method based on the Feshbach projection formalism provides an alternative to popular methods such as the Feynman diagrammatic techniques and the master equation approach that are commonly used for studying open quantum systems. It is formally exact but very flexible and can be adjusted to many specific situations. One bright phenomenon emerging in the situation with a sufficiently strong continuum coupling in the case when the number of open channels is relatively small compared to the number of involved intrinsic states is the so-called superradiance. Being an analog of superradiance in quantum optics, this term stands for the formation in the system of a collective superposition of the intrinsic states coherently coupled to the same decay channel. The footprint of superradiance in each system is investigated in detail. In the quantum transport problem, signal transmission is greatly enhanced at the transition to superradiance. In the proposed solid state based charge qubit, the superradiant states effectively protect the remaining internal states from decaying into the continuum and hence increase the lifetime of the device. Finally, the superradiance phenomenon provides us a tool to manipulate light at the nanoscale. It is responsible for the existence of modes with distinct radiation properties in a system of coupled plasmonic nanoantennas: superradiant states with enhanced and dark modes with extremely damped radiation. Furthermore, similar to the quantum case, energy transport through a plasmonic waveguide is greatly enhanced.

The RNA gene information: retroelement-microRNA entangling as the RNA quantum code.

PubMed

Fujii, Yoichi Robertus

2013-01-01

MicroRNA (miRNA) and retroelements may be a master of regulator in our life, which are evolutionally involved in the origin of species. To support the Darwinism from the aspect of molecular evolution process, it has tremendously been interested in the molecular information of naive RNA. The RNA wave model 2000 consists of four concepts that have altered from original idea of the miRNA genes for crosstalk among embryonic stem cells, their niche cells, and retroelements as a carrier vesicle of the RNA genes. (1) the miRNA gene as a mobile genetic element induces transcriptional and posttranscriptional silencing via networking-processes (no hierarchical architecture); (2) the RNA information supplied by the miRNA genes expands to intracellular, intercellular, intraorgan, interorgan, intraspecies, and interspecies under the cycle of life into the global environment; (3) the mobile miRNAs can self-proliferate; and (4) cells contain two types information as resident and genomic miRNAs. Based on RNA wave, we have developed an interest in investigation of the transformation from RNA information to quantum bits as physicochemical characters of RNA with the measurement of RNA electron spin. When it would have been given that the fundamental bases for the acquired characters in genetics can be controlled by RNA gene information, it may be available to apply for challenging against RNA gene diseases, such as stress-induced diseases.

Transport mirages in single-molecule devices

NASA Astrophysics Data System (ADS)

Gaudenzi, R.; Misiorny, M.; Burzurí, E.; Wegewijs, M. R.; van der Zant, H. S. J.

2017-03-01

Molecular systems can exhibit a complex, chemically tailorable inner structure which allows for targeting of specific mechanical, electronic, and optical properties. At the single-molecule level, two major complementary ways to explore these properties are molecular quantum-dot structures and scanning probes. This article outlines comprehensive principles of electron-transport spectroscopy relevant to both these approaches and presents a new, high-resolution experiment on a high-spin single-molecule junction exemplifying these principles. Such spectroscopy plays a key role in further advancing our understanding of molecular and atomic systems, in particular, the relaxation of their spin. In this joint experimental and theoretical analysis, particular focus is put on the crossover between the resonant regime [single-electron tunneling] and the off-resonant regime [inelastic electron (co)tunneling spectroscopy (IETS)]. We show that the interplay of these two processes leads to unexpected mirages of resonances not captured by either of the two pictures alone. Although this turns out to be important in a large fraction of the possible regimes of level positions and bias voltages, it has been given little attention in molecular transport studies. Combined with nonequilibrium IETS—four-electron pump-probe excitations—these mirages provide crucial information on the relaxation of spin excitations. Our encompassing physical picture is supported by a master-equation approach that goes beyond weak coupling. The present work encourages the development of a broader connection between the fields of molecular quantum-dot and scanning probe spectroscopy.

Influence of Coherent Tunneling and Incoherent Hopping on the Charge Transfer Mechanism in Linear Donor-Bridge-Acceptor Systems.

PubMed

Li, Guangqi; Govind, Niranjan; Ratner, Mark A; Cramer, Christopher J; Gagliardi, Laura

2015-12-17

The mechanism of charge transfer has been observed to change from tunneling to hopping with increasing numbers of DNA base pairs in polynucleotides and with the length of molecular wires. The aim of this paper is to investigate this transition by examining the population dynamics using a tight-binding Hamiltonian with model parameters to describe a linear donor-bridge-acceptor (D-B-A) system. The model includes a primary vibration and an electron-vibration coupling at each site. A further coupling of the primary vibration with a secondary phonon bath allows the system to dissipate energy to the environment and reach a steady state. We apply the quantum master equation (QME) approach, based on second-order perturbation theory in a quantum dissipative system, to examine the dynamical processes involved in charge-transfer and follow the population transfer rate at the acceptor, ka, to shed light on the transition from tunneling to hopping. With a small tunneling parameter, V, the on-site population tends to localize and form polarons, and the hopping mechanism dominates the transfer process. With increasing V, the population tends to be delocalized and the tunneling mechanism dominates. The competition between incoherent hopping and coherent tunneling governs the mechanism of charge transfer. By varying V and the total number of sites, we also examine the onset of the transition from tunneling to hopping with increasing length.

48 CFR 217.7103-6 - Modification of master agreements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Modification of master... Master Agreement for Repair and Alteration of Vessels 217.7103-6 Modification of master agreements. (a) Review each master agreement at least annually before the anniversary of its effective date and revise it...

46 CFR 189.35-13 - Master's responsibility.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Master's responsibility. 189.35-13 Section 189.35-13... AND CERTIFICATION Weight Handling Gear § 189.35-13 Master's responsibility. (a) The master of the... permitted to operate the weight handling gear. The master shall designate the operators. (5) A minimum...

46 CFR Sec. 3 - Master's requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 8 2010-10-01 2010-10-01 false Master's requirements. Sec. 3 Section 3 Shipping... Master's requirements. The Master shall: (a) Receive and receipt for the quantities of slop chest items... therefor, at the unit price, specified by the Slop Chest Statement furnished the Master by the General...

48 CFR 217.7103-6 - Modification of master agreements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Modification of master... Master Agreement for Repair and Alteration of Vessels 217.7103-6 Modification of master agreements. (a) Review each master agreement at least annually before the anniversary of its effective date and revise it...

46 CFR 189.35-13 - Master's responsibility.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Master's responsibility. 189.35-13 Section 189.35-13... AND CERTIFICATION Weight Handling Gear § 189.35-13 Master's responsibility. (a) The master of the... permitted to operate the weight handling gear. The master shall designate the operators. (5) A minimum...

48 CFR 217.7103-1 - Content and format of master agreements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... master agreements. 217.7103-1 Section 217.7103-1 Federal Acquisition Regulations System DEFENSE... CONTRACTING METHODS Master Agreement for Repair and Alteration of Vessels 217.7103-1 Content and format of master agreements. Follow the procedures at PGI 217.7103-1 for preparation of master agreements. [71 FR...

48 CFR 217.7103-6 - Modification of master agreements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Modification of master... Master Agreement for Repair and Alteration of Vessels 217.7103-6 Modification of master agreements. (a) Review each master agreement at least annually before the anniversary of its effective date and revise it...

48 CFR 217.7103-1 - Content and format of master agreements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... master agreements. 217.7103-1 Section 217.7103-1 Federal Acquisition Regulations System DEFENSE... CONTRACTING METHODS Master Agreement for Repair and Alteration of Vessels 217.7103-1 Content and format of master agreements. Follow the procedures at PGI 217.7103-1 for preparation of master agreements. [71 FR...

48 CFR 217.7103-1 - Content and format of master agreements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... master agreements. 217.7103-1 Section 217.7103-1 Federal Acquisition Regulations System DEFENSE... CONTRACTING METHODS Master Agreement for Repair and Alteration of Vessels 217.7103-1 Content and format of master agreements. Follow the procedures at PGI 217.7103-1 for preparation of master agreements. [71 FR...

46 CFR Sec. 3 - Master's requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 8 2011-10-01 2011-10-01 false Master's requirements. Sec. 3 Section 3 Shipping... Master's requirements. The Master shall: (a) Receive and receipt for the quantities of slop chest items... therefor, at the unit price, specified by the Slop Chest Statement furnished the Master by the General...

46 CFR Sec. 3 - Master's requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 8 2012-10-01 2012-10-01 false Master's requirements. Sec. 3 Section 3 Shipping... Master's requirements. The Master shall: (a) Receive and receipt for the quantities of slop chest items... therefor, at the unit price, specified by the Slop Chest Statement furnished the Master by the General...

46 CFR Sec. 3 - Master's requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 8 2014-10-01 2014-10-01 false Master's requirements. Sec. 3 Section 3 Shipping... Master's requirements. The Master shall: (a) Receive and receipt for the quantities of slop chest items... therefor, at the unit price, specified by the Slop Chest Statement furnished the Master by the General...

46 CFR Sec. 3 - Master's requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 8 2013-10-01 2013-10-01 false Master's requirements. Sec. 3 Section 3 Shipping... Master's requirements. The Master shall: (a) Receive and receipt for the quantities of slop chest items... therefor, at the unit price, specified by the Slop Chest Statement furnished the Master by the General...

46 CFR 189.35-13 - Master's responsibility.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Master's responsibility. 189.35-13 Section 189.35-13... AND CERTIFICATION Weight Handling Gear § 189.35-13 Master's responsibility. (a) The master of the... permitted to operate the weight handling gear. The master shall designate the operators. (5) A minimum...

46 CFR 189.35-13 - Master's responsibility.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Master's responsibility. 189.35-13 Section 189.35-13... AND CERTIFICATION Weight Handling Gear § 189.35-13 Master's responsibility. (a) The master of the... permitted to operate the weight handling gear. The master shall designate the operators. (5) A minimum...

48 CFR 217.7103-1 - Content and format of master agreements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... master agreements. 217.7103-1 Section 217.7103-1 Federal Acquisition Regulations System DEFENSE... CONTRACTING METHODS Master Agreement for Repair and Alteration of Vessels 217.7103-1 Content and format of master agreements. Follow the procedures at PGI 217.7103-1 for preparation of master agreements. [71 FR...

48 CFR 217.7103-1 - Content and format of master agreements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... master agreements. 217.7103-1 Section 217.7103-1 Federal Acquisition Regulations System DEFENSE... CONTRACTING METHODS Master Agreement for Repair and Alteration of Vessels 217.7103-1 Content and format of master agreements. Follow the procedures at PGI 217.7103-1 for preparation of master agreements. [71 FR...

48 CFR 217.7103-6 - Modification of master agreements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Modification of master... Master Agreement for Repair and Alteration of Vessels 217.7103-6 Modification of master agreements. (a) Review each master agreement at least annually before the anniversary of its effective date and revise it...

48 CFR 217.7103-6 - Modification of master agreements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Modification of master... Master Agreement for Repair and Alteration of Vessels 217.7103-6 Modification of master agreements. (a) Review each master agreement at least annually before the anniversary of its effective date and revise it...

78 FR 43251 - Grosvenor Alternative Funds Master Trust, et al.; Notice of Application

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-19

... Alternative Funds Master Trust, et al.; Notice of Application July 15, 2013. AGENCY: Securities and Exchange... Alternative Funds Master Trust (``Master Trust''), Grosvenor Alternative Funds (``GAF Trust''), and Grosvenor... calling (202) 551-8090. Applicants' Representations 1. The Master Trust \\1\\ and the GAF Trust...

Cloning SU8 silicon masters using epoxy resins to increase feature replicability and production for cell culture devices.

PubMed

Kamande, J W; Wang, Y; Taylor, A M

2015-05-01

In recent years, there has been a dramatic increase in the use of poly(dimethylsiloxane) (PDMS) devices for cell-based studies. Commonly, the negative tone photoresist, SU8, is used to pattern features onto silicon wafers to create masters (SU8-Si) for PDMS replica molding. However, the complexity in the fabrication process, low feature reproducibility (master-to-master variability), silane toxicity, and short life span of these masters have been deterrents for using SU8-Si masters for the production of cell culture based PDMS microfluidic devices. While other techniques have demonstrated the ability to generate multiple devices from a single master, they often do not match the high feature resolution (∼0.1 μm) and low surface roughness that soft lithography masters offer. In this work, we developed a method to fabricate epoxy-based masters that allows for the replication of features with high fidelity directly from SU8-Si masters via their PDMS replicas. By this method, we show that we could obtain many epoxy based masters with equivalent features to a single SU8-Si master with a low feature variance of 1.54%. Favorable feature transfer resolutions were also obtained by using an appropriate Tg epoxy based system to ensure minimal shrinkage of features ranging in size from ∼100 μm to <10 μm in height. We further show that surface coating epoxy masters with Cr/Au lead to effective demolding and yield PDMS chambers that are suitable for long-term culturing of sensitive primary hippocampal neurons. Finally, we incorporated pillars within the Au-epoxy masters to eliminate the process of punching media reservoirs and thereby reducing substantial artefacts and wastage.

Cloning SU8 silicon masters using epoxy resins to increase feature replicability and production for cell culture devices

PubMed Central

Kamande, J. W.; Wang, Y.; Taylor, A. M.

2015-01-01

In recent years, there has been a dramatic increase in the use of poly(dimethylsiloxane) (PDMS) devices for cell-based studies. Commonly, the negative tone photoresist, SU8, is used to pattern features onto silicon wafers to create masters (SU8-Si) for PDMS replica molding. However, the complexity in the fabrication process, low feature reproducibility (master-to-master variability), silane toxicity, and short life span of these masters have been deterrents for using SU8-Si masters for the production of cell culture based PDMS microfluidic devices. While other techniques have demonstrated the ability to generate multiple devices from a single master, they often do not match the high feature resolution (∼0.1 μm) and low surface roughness that soft lithography masters offer. In this work, we developed a method to fabricate epoxy-based masters that allows for the replication of features with high fidelity directly from SU8-Si masters via their PDMS replicas. By this method, we show that we could obtain many epoxy based masters with equivalent features to a single SU8-Si master with a low feature variance of 1.54%. Favorable feature transfer resolutions were also obtained by using an appropriate Tg epoxy based system to ensure minimal shrinkage of features ranging in size from ∼100 μm to <10 μm in height. We further show that surface coating epoxy masters with Cr/Au lead to effective demolding and yield PDMS chambers that are suitable for long-term culturing of sensitive primary hippocampal neurons. Finally, we incorporated pillars within the Au-epoxy masters to eliminate the process of punching media reservoirs and thereby reducing substantial artefacts and wastage. PMID:26180572

The master degree: A critical transition in STEM doctoral education

NASA Astrophysics Data System (ADS)

Lange, Sheila Edwards

The need to broaden participation in the nation's science, technology, engineering, and mathematics (STEM) undergraduate and graduate programs is currently a matter of national urgency. The small number of women and underrepresented minorities (URM) earning doctoral degrees in STEM is particularly troubling given significant increases in the number of students earning master's degrees since 1990. In the decade between 1990 and 2000, the total number of master's recipients increased by 42%. During this same time period, the number of women earning master's degrees increased by 56%, African Americans increased by 132%, American Indians by 101%, Hispanics by 146%, and Asian Americans by 117% (Syverson, 2003). Growth in underrepresented group education at the master's level raises questions about the relationship between master's and doctoral education. Secondary data analysis of the Survey of Earned Doctorates (SED) was used to examine institutional pathways to the doctorate in STEM disciplines and transitions from master's to doctoral programs by race and gender. While the study revealed no significant gender differences in pathways, compared to White and Asian American students, URM students take significantly different pathways to the doctorate. URM students are significantly more likely to earn the bachelor's, master's, and doctoral degrees at three different institutions. Their path is significantly more likely to include earning a master's degree en route to the doctorate. Further, URM students are more likely to experience transition between the master's and doctoral degrees, and the transitions are not limited to those who earn master's degrees at master's-only institutions. These findings suggest that earning a master's degree is more often a stepping stone to the doctorate for URM students. Master's degree programs, therefore, have the potential to be a valuable resource for policymakers and graduate programs seeking to increase the diversity of URM students earning doctorates in STEM.

Dual arm master controller for a bilateral servo-manipulator

DOEpatents

Kuban, Daniel P.; Perkins, Gerald S.

1989-01-01

A master controller for a mechanically dissimilar bilateral slave servo-manipulator is disclosed. The master controller includes a plurality of drive trains comprising a plurality of sheave arrangements and cables for controlling upper and lower degrees of master movement. The cables and sheaves of the master controller are arranged to effect kinematic duplication of the slave servo-manipulator, despite mechanical differences therebetween. A method for kinematically matching a master controller to a slave servo-manipulator is also disclosed.

A polymeric master replication technology for mass fabrication of poly(dimethylsiloxane) microfluidic devices.

PubMed

Li, Hai-Fang; Lin, Jin-Ming; Su, Rong-Guo; Cai, Zong Wei; Uchiyama, Katsumi

2005-05-01

A protocol of producing multiple polymeric masters from an original glass master mold has been developed, which enables the production of multiple poly(dimethylsiloxane) (PDMS)-based microfluidic devices in a low-cost and efficient manner. Standard wet-etching techniques were used to fabricate an original glass master with negative features, from which more than 50 polymethylmethacrylate (PMMA) positive replica masters were rapidly created using the thermal printing technique. The time to replicate each PMMA master was as short as 20 min. The PMMA replica masters have excellent structural features and could be used to cast PDMS devices for many times. An integration geometry designed for laser-induced fluorescence (LIF) detection, which contains normal deep microfluidic channels and a much deeper optical fiber channel, was successfully transferred into PDMS devices. The positive relief on seven PMMA replica masters is replicated with regard to the negative original glass master, with a depth average variation of 0.89% for 26-microm deep microfluidic channels and 1.16% for the 90 mum deep fiber channel. The imprinted positive relief in PMMA from master-to-master is reproducible with relative standard deviations (RSDs) of 1.06% for the maximum width and 0.46% for depth in terms of the separation channel. The PDMS devices fabricated from the PMMA replica masters were characterized and applied to the separation of a fluorescein isothiocyanate (FITC)-labeled epinephrine sample.

The Master Artisan: A Framework for Master Tradespeople in Australia. Occasional Paper

ERIC Educational Resources Information Center

O'Reilly-Briggs, Karen

2011-01-01

The author explores the prospect of improving pathways and opportunities for tradespeople in Australia through the introduction of a masters-level qualification. The study investigates the views and opinions of senior industry representatives and professional educators to determine whether the introduction of a master trade or master artisan…

19 CFR 10.90 - Master records and metal matrices.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 1 2011-04-01 2011-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing...

19 CFR 10.90 - Master records and metal matrices.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 1 2013-04-01 2013-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing...

20 CFR 632.22 - Modification of a Comprehensive Annual Plan (CAP) and/or Master Plan.

Code of Federal Regulations, 2012 CFR

2012-04-01

... (CAP) and/or Master Plan. 632.22 Section 632.22 Employees' Benefits EMPLOYMENT AND TRAINING... Master Plan. (a) The requirements for modifying a Master Plan and/or CAP will be included in administrative instructions issued by the Grant Officer upon final implementation of the Master Plan/CAP system...

21 CFR 111.210 - What must the master manufacturing record include?

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 2 2011-04-01 2011-04-01 false What must the master manufacturing record include...: Requirements for the Master Manufacturing Record § 111.210 What must the master manufacturing record include? The master manufacturing record must include: (a) The name of the dietary supplement to be...

21 CFR 111.210 - What must the master manufacturing record include?

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 2 2012-04-01 2012-04-01 false What must the master manufacturing record include...: Requirements for the Master Manufacturing Record § 111.210 What must the master manufacturing record include? The master manufacturing record must include: (a) The name of the dietary supplement to be...

21 CFR 111.210 - What must the master manufacturing record include?

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 2 2014-04-01 2014-04-01 false What must the master manufacturing record include...: Requirements for the Master Manufacturing Record § 111.210 What must the master manufacturing record include? The master manufacturing record must include: (a) The name of the dietary supplement to be...

19 CFR 10.90 - Master records and metal matrices.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 1 2014-04-01 2014-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing...

16 CFR 1011.4 - Forms of advance public notice of meetings; Public Calendar/Master Calendar and Federal Register.

Code of Federal Regulations, 2012 CFR

2012-01-01

...; Public Calendar/Master Calendar and Federal Register. 1011.4 Section 1011.4 Commercial Practices CONSUMER... meetings; Public Calendar/Master Calendar and Federal Register. Advance notice of Agency activities is... Calendar/Master Calendar. (1) The printed Public Calendar and the Master Calendar maintained in the Office...

19 CFR 10.90 - Master records and metal matrices.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 1 2012-04-01 2012-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing...

16 CFR 1011.4 - Forms of advance public notice of meetings; Public Calendar/Master Calendar and Federal Register.

Code of Federal Regulations, 2014 CFR

2014-01-01

...; Public Calendar/Master Calendar and Federal Register. 1011.4 Section 1011.4 Commercial Practices CONSUMER... meetings; Public Calendar/Master Calendar and Federal Register. Advance notice of Agency activities is... Calendar/Master Calendar. (1) The printed Public Calendar and the Master Calendar maintained in the Office...

21 CFR 111.210 - What must the master manufacturing record include?

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 2 2013-04-01 2013-04-01 false What must the master manufacturing record include...: Requirements for the Master Manufacturing Record § 111.210 What must the master manufacturing record include? The master manufacturing record must include: (a) The name of the dietary supplement to be...

Advising Master's Students Pursuing Doctoral Study: A Survey of Counselor Educators and Supervisors

ERIC Educational Resources Information Center

Sackett, Corrine R.; Hartig, Nadine; Bodenhorn, Nancy; Farmer, Laura B.; Ghoston, Michelle R.; Graham, Jasmine; Lile, Jesse

2015-01-01

This study explored what faculty members are recommending to counselor education master's students regarding post-master's experience when considering doctoral studies and what the current faculty hiring preferences are in reference to the amount of post-master's experience needed. Advisors in counselor education master's programs encounter these…

20 CFR 632.22 - Modification of a Comprehensive Annual Plan (CAP) and/or Master Plan.

Code of Federal Regulations, 2011 CFR

2011-04-01

... (CAP) and/or Master Plan. 632.22 Section 632.22 Employees' Benefits EMPLOYMENT AND TRAINING... Master Plan. (a) The requirements for modifying a Master Plan and/or CAP will be included in administrative instructions issued by the Grant Officer upon final implementation of the Master Plan/CAP system...

Science Professionals: Master's Education for a Competitive World

ERIC Educational Resources Information Center

National Academies Press, 2008

2008-01-01

What are employer needs for staff trained in the natural sciences at the master's degree level? How do master's level professionals in the natural sciences contribute in the workplace? How do master's programs meet or support educational and career goals? "Science Professionals: Master's Education for a Competitive World" examines the answers to…

Experiential Learning: Lessons Learned from the UND Business and Government Symposium

ERIC Educational Resources Information Center

Harsell, Dana Michael; O'Neill, Patrick B.

2010-01-01

The authors describe lessons learned from a limited-duration experiential learning component of a Master's level course. The course is open to Master's in Business and Master's in Public Administration students and explores the relationships between government and business. A complete discussion of the Master's in Business and Master's in Public…

19 CFR 10.90 - Master records and metal matrices.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 1 2010-04-01 2010-04-01 false Master records and metal matrices. 10.90 Section... Master Records, and Metal Matrices § 10.90 Master records and metal matrices. (a) Consumption entries... made, of each master record or metal matrix covered thereby. (c) A bond on Customs Form 301, containing...

Pacific Fleet Regional Inventory Stocking Model (PRISM)

DTIC Science & Technology

2003-06-01

Fleet Inventory Management Form ..........................................................................99 19. Master Parts List Input Form...100 20. Master Parts List Update Form...107 26. Master Parts List by APL Report..............................................................................109 27. Master

46 CFR 42.15-1 - Information to be supplied to the master.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Information to be supplied to the master. 42.15-1... master. (a) The master of every new vessel shall be supplied with sufficient information in a form... authority. (b) The master of every new vessel, which is not already provided with stability information...

43 CFR 30.122 - Is the judge required to accept the master's recommended decision?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Is the judge required to accept the master... accept the master's recommended decision? No, the judge is not required to accept the master's... the record of the proceedings heard by the master, including any objections and responses filed, and...

46 CFR 11.463 - General requirements for endorsements as master, mate (pilot), and apprentice mate (steersman) of...

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false General requirements for endorsements as master, mate... Professional Requirements for Deck Officers § 11.463 General requirements for endorsements as master, mate... endorsements: (1) Master of towing vessels. (2) Master of towing vessels, limited. (3) Mate (pilot) of towing...

21 CFR 111.205 - What is the requirement to establish a master manufacturing record?

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 2 2010-04-01 2010-04-01 false What is the requirement to establish a master... System: Requirements for the Master Manufacturing Record § 111.205 What is the requirement to establish a master manufacturing record? (a) You must prepare and follow a written master manufacturing record for...

46 CFR 11.463 - General requirements for endorsements as master, mate (pilot), and apprentice mate (steersman) of...

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false General requirements for endorsements as master, mate... Professional Requirements for Deck Officers § 11.463 General requirements for endorsements as master, mate... endorsements: (1) Master of towing vessels. (2) Master of towing vessels, limited. (3) Mate (pilot) of towing...

21 CFR 111.205 - What is the requirement to establish a master manufacturing record?

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 2 2014-04-01 2014-04-01 false What is the requirement to establish a master... System: Requirements for the Master Manufacturing Record § 111.205 What is the requirement to establish a master manufacturing record? (a) You must prepare and follow a written master manufacturing record for...

46 CFR 11.463 - General requirements for endorsements as master, mate (pilot), and apprentice mate (steersman) of...

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false General requirements for endorsements as master, mate... Professional Requirements for Deck Officers § 11.463 General requirements for endorsements as master, mate... endorsements: (1) Master of towing vessels. (2) Master of towing vessels, limited. (3) Mate (pilot) of towing...

43 CFR 30.122 - Is the judge required to accept the master's recommended decision?

Code of Federal Regulations, 2010 CFR

2010-10-01

... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Is the judge required to accept the master... accept the master's recommended decision? No, the judge is not required to accept the master's... the record of the proceedings heard by the master, including any objections and responses filed, and...

43 CFR 2804.18 - What provisions do Master Agreements contain and what are their limitations?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false What provisions do Master Agreements....18 What provisions do Master Agreements contain and what are their limitations? (a) A Master...) BLM will not enter into any Agreement that is not in the public interest. (c) If you sign a Master...

46 CFR 42.15-1 - Information to be supplied to the master.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Information to be supplied to the master. 42.15-1... master. (a) The master of every new vessel shall be supplied with sufficient information in a form... authority. (b) The master of every new vessel, which is not already provided with stability information...

43 CFR 2804.18 - What provisions do Master Agreements contain and what are their limitations?

Code of Federal Regulations, 2012 CFR

2012-10-01

... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false What provisions do Master Agreements....18 What provisions do Master Agreements contain and what are their limitations? (a) A Master...) BLM will not enter into any Agreement that is not in the public interest. (c) If you sign a Master...

46 CFR 42.15-1 - Information to be supplied to the master.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Information to be supplied to the master. 42.15-1... master. (a) The master of every new vessel shall be supplied with sufficient information in a form... authority. (b) The master of every new vessel, which is not already provided with stability information...

46 CFR 42.15-1 - Information to be supplied to the master.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Information to be supplied to the master. 42.15-1... master. (a) The master of every new vessel shall be supplied with sufficient information in a form... authority. (b) The master of every new vessel, which is not already provided with stability information...

21 CFR 314.420 - Drug master files.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 5 2014-04-01 2014-04-01 false Drug master files. 314.420 Section 314.420 Food... master files. (a) A drug master file is a submission of information to the Food and Drug Administration by a person (the drug master file holder) who intends it to be used for one of the following purposes...

46 CFR 42.15-1 - Information to be supplied to the master.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Information to be supplied to the master. 42.15-1... master. (a) The master of every new vessel shall be supplied with sufficient information in a form... authority. (b) The master of every new vessel, which is not already provided with stability information...

43 CFR 2804.18 - What provisions do Master Agreements contain and what are their limitations?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false What provisions do Master Agreements....18 What provisions do Master Agreements contain and what are their limitations? (a) A Master...) BLM will not enter into any Agreement that is not in the public interest. (c) If you sign a Master...

16 CFR § 1011.4 - Forms of advance public notice of meetings; Public Calendar/Master Calendar and Federal Register.

Code of Federal Regulations, 2013 CFR

2013-01-01

...; Public Calendar/Master Calendar and Federal Register. § 1011.4 Section § 1011.4 Commercial Practices... notice of meetings; Public Calendar/Master Calendar and Federal Register. Advance notice of Agency...) Public Calendar/Master Calendar. (1) The printed Public Calendar and the Master Calendar maintained in...

43 CFR 2804.18 - What provisions do Master Agreements contain and what are their limitations?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false What provisions do Master Agreements....18 What provisions do Master Agreements contain and what are their limitations? (a) A Master...) BLM will not enter into any Agreement that is not in the public interest. (c) If you sign a Master...

46 CFR 11.463 - General requirements for endorsements as master, mate (pilot), and apprentice mate (steersman) of...

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false General requirements for endorsements as master, mate... Professional Requirements for Deck Officers § 11.463 General requirements for endorsements as master, mate... endorsements: (1) Master of towing vessels. (2) Master of towing vessels, limited. (3) Mate (pilot) of towing...

43 CFR 30.122 - Is the judge required to accept the master's recommended decision?

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Is the judge required to accept the master... accept the master's recommended decision? No, the judge is not required to accept the master's... the record of the proceedings heard by the master, including any objections and responses filed, and...

43 CFR 30.122 - Is the judge required to accept the master's recommended decision?

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Is the judge required to accept the master... accept the master's recommended decision? No, the judge is not required to accept the master's... the record of the proceedings heard by the master, including any objections and responses filed, and...

21 CFR 111.205 - What is the requirement to establish a master manufacturing record?

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 2 2013-04-01 2013-04-01 false What is the requirement to establish a master... System: Requirements for the Master Manufacturing Record § 111.205 What is the requirement to establish a master manufacturing record? (a) You must prepare and follow a written master manufacturing record for...

43 CFR 30.122 - Is the judge required to accept the master's recommended decision?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Is the judge required to accept the master... accept the master's recommended decision? No, the judge is not required to accept the master's... the record of the proceedings heard by the master, including any objections and responses filed, and...

Defense.gov Special Report: A Nation's Gratitude

Science.gov Websites

Deployments, 2003-2006 Baghdad, Ramadi Air Force Master Sgt. Jessica R. Coombs Air Force Master Sgt. Jessica R . Coombs 40th Expeditionary Support Squadron June 2011 - December 2011 Ali Air Base Indiana Army Master Sgt Multiple Deployments, 2004-2007 Fallujah, Ramadi Air Force Master Sgt. Jeremy G. Coombs Air Force Master

USNO Master Clock - Naval Oceanography Portal

Science.gov Websites

section Advanced Search... Sections Home Time Earth Orientation Astronomy Meteorology Oceanography Ice You are here: Home › USNO › Precise Time › Master Clock USNO Logo USNO Navigation Master Clock GPS Display Clocks TWSTT Telephone Time NTP Info USNO Master Clock clock vault The USNO Master Clock is the

Master Volunteer Life Cycle: A Wide Angle Lens on the Volunteer Experience

ERIC Educational Resources Information Center

Strauss, Andrea Lorek; Rager, Amy

2017-01-01

Extension master volunteer programs, such as master naturalist and master gardener, often focus heavily on volunteer education. The model presented here describes the full life cycle of a master volunteer's experience in the program, putting education in the context of other essential program components. By zooming out to a wide-angle view of the…

Dismantling a Master Narrative: Using Culturally Responsive Pedagogy to Teach the History of Art Education

ERIC Educational Resources Information Center

Acuff, Joni Boyd; Hirak, Brent; Nangah, Mary

2012-01-01

The consequence of narratives becoming stagnant or controlled is that they become a Master Narrative. The Master Narrative is an "ideological script that is being imposed by the people in authority on everybody else: The Master Fiction... history" (Moyers, 1990, para. 4). Master Narratives use myths and ideologies to sustain a sanitized version of…

46 CFR 11.459 - Service requirements for master or mate of rivers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false Service requirements for master or mate of rivers. 11... requirements for master or mate of rivers. (a) An applicant for an endorsement as master of river steam or motor vessels of any gross tons must meet the same service requirements as master of inland steam or...

46 CFR 11.459 - Service requirements for master or mate of rivers.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Service requirements for master or mate of rivers. 11... requirements for master or mate of rivers. (a) An applicant for an endorsement as master of river steam or motor vessels of any gross tons must meet the same service requirements as master of inland steam or...

46 CFR 11.459 - Service requirements for master or mate of rivers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false Service requirements for master or mate of rivers. 11... requirements for master or mate of rivers. (a) An applicant for an endorsement as master of river steam or motor vessels of any gross tons must meet the same service requirements as master of inland steam or...

46 CFR 11.459 - Service requirements for master or mate of rivers.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Service requirements for master or mate of rivers. 11... requirements for master or mate of rivers. (a) An applicant for an endorsement as master of river steam or motor vessels of any gross tons must meet the same service requirements as master of inland steam or...

Performance Comparison of Al-Ti Master Alloys with Different Microstructures in Grain Refinement of Commercial Purity Aluminum.

PubMed

Ding, Wanwu; Xia, Tiandong; Zhao, Wenjun

2014-05-07

Three types of Al-5Ti master alloys were synthesized by a method of thermal explosion reaction in pure molten aluminum. Performance comparison of Al-5Ti master alloy in grain refinement of commercial purity Al with different additions (0.6%, 1.0%, 1.6%, 2.0%, and 3.0%) and holding time (10, 30, 60 and 120 min) were investigated. The results show that Al-5Ti master alloy with blocky TiAl₃ particles clearly has better refining efficiency than the master alloy with mixed TiAl₃ particles and the master alloy with needle-like TiAl₃ particles. The structures of master alloys, differing by sizes, morphologies and quantities of TiAl₃ crystals, were found to affect the pattern of the grain refining properties with the holding time. The grain refinement effect was revealed to reduce markedly for master alloys with needle-like TiAl₃ crystals and to show the further significant improvement at a longer holding time for the master alloy containing both larger needle-like and blocky TiAl₃ particles. For the master alloy with finer blocky particles, the grain refining effect did not obviously decrease during the whole studied range of the holding time.

NASA Tech Briefs, May 2007

NASA Technical Reports Server (NTRS)

2007-01-01

Topics include: Noise-Canceling Helmet Audio System; Program Analyzes Spacecraft/Ground Radio Links; Two-Way Communication Using RFID Equipment and Techniques; Six-Message Electromechanical Display System; Scanning Terahertz Heterodyne Imaging Systems; Master Clock and Time-Signal-Distribution System; Synchronous Phase-Resolving Flash Range Imaging; Integrated Radial Probe Transition From MMIC to Waveguide; Bar-Code System for a Microbiological Laboratory; MMIC Amplifier Produces Gain of 10 dB at 235 GHz; Mapping Nearby Terrain in 3D by Use of a Grid of Laser Spots; Digital Beam Deflectors Based Partly on Liquid Crystals; Narrow-Band WGM Optical Filters With Tunable FSRs; Better Finite-Element Analysis of Composite Shell Structures; Computing Spacecraft-Pointing Vectors for Limb Tracking; Enhanced Master Controller Unit Tester; Rover Graphical Simulator; Increasing Durability of Flame-Sprayed Strain Gauges; Multifunctional, High-Temperature Nanocomposites; Multilayer Impregnated Fibrous Thermal Insulation Tiles; Radiation-Shielding Polymer/Soil Composites; Film/Adhesive Processing Module for Fiber-Placement Processing of Composites; Fabrication of Submillimeter Axisymmetric Optical Components; Electrochemical Disposal of Hydrazines in Water; Statistical Model of Evaporating Multicomponent Fuel Drops; Resistively Heated SiC Nozzle for Generating Molecular Beams; Compact Packaging of Photonic Millimeter-Wave Receiver; Diffractive Combiner of Single-Mode Pump Laser-Diode Beams; Wide-Band, High-Quantum-Efficiency Photodetector; A Robustly Stabilizing Model Predictive Control Algorithm; Modeling Evaporation of Drops of Different Kerosenes; Development of Vapor-Phase Catalytic Ammonia Removal System; Several Developments in Space Tethers; Design Concept for a Nuclear Reactor-Powered Mars Rover; Formation-Initialization Algorithm for N Spacecraft; and DNSs of Multicomponent Gaseous and Drop-Laden Mixing Layers Achieving Transition to Turbulence.

Eager protocol on a cache pipeline dataflow

DOEpatents

Ohmacht, Martin; Sugavanam, Krishnan

2012-11-13

A master device sends a request to communicate with a slave device to a switch. The master device waits for a period of cycles the switch takes to decide whether the master device can communicate with the slave device, and the master device sends data associated with the request to communicate at least after the period of cycles has passed since the master device sent the request to communicate to the switch without waiting to receive an acknowledgment from the switch that the master device can communicate with the slave device.

A novel statistical approach for identification of the master regulator transcription factor.

PubMed

Sikdar, Sinjini; Datta, Susmita

2017-02-02

Transcription factors are known to play key roles in carcinogenesis and therefore, are gaining popularity as potential therapeutic targets in drug development. A 'master regulator' transcription factor often appears to control most of the regulatory activities of the other transcription factors and the associated genes. This 'master regulator' transcription factor is at the top of the hierarchy of the transcriptomic regulation. Therefore, it is important to identify and target the master regulator transcription factor for proper understanding of the associated disease process and identifying the best therapeutic option. We present a novel two-step computational approach for identification of master regulator transcription factor in a genome. At the first step of our method we test whether there exists any master regulator transcription factor in the system. We evaluate the concordance of two ranked lists of transcription factors using a statistical measure. In case the concordance measure is statistically significant, we conclude that there is a master regulator. At the second step, our method identifies the master regulator transcription factor, if there exists one. In the simulation scenario, our method performs reasonably well in validating the existence of a master regulator when the number of subjects in each treatment group is reasonably large. In application to two real datasets, our method ensures the existence of master regulators and identifies biologically meaningful master regulators. An R code for implementing our method in a sample test data can be found in http://www.somnathdatta.org/software . We have developed a screening method of identifying the 'master regulator' transcription factor just using only the gene expression data. Understanding the regulatory structure and finding the master regulator help narrowing the search space for identifying biomarkers for complex diseases such as cancer. In addition to identifying the master regulator our method provides an overview of the regulatory structure of the transcription factors which control the global gene expression profiles and consequently the cell functioning.

Publishing scientific papers based on Master's and Ph.D. theses from a small scientific community: case study of Croatian medical schools.

PubMed

Frković, Vedran; Skender, Tomislav; Dojćinović, Bojan; Bilić-Zulle, Lidija

2003-02-01

To evaluate publishing activity of medical doctors after they have obtained Master's or Ph.D. degree at the Rijeka and Zagreb University Schools of Medicine in Croatia, and establish the number of journal articles based on these theses. Data on Master's and Ph.D. theses defended at the Rijeka and Zagreb University Schools of Medicine in the 1990-1999 period were collected by hand-search of the archive. MEDLINE and Current Contents databases were searched for journal articles resulting from the theses. During the 10-year period, 1,535 Master's and 634 Ph.D. theses were defended at the Rijeka and Zagreb University Schools of Medicine (253 Master's and 138 Ph.D. theses from Rijeka and 1,282 Master's and 496 Ph.D. theses from Zagreb). There were 201 (14%) Master's and 218 (34%) Ph.D. theses that resulted in articles published in journals indexed in MEDLINE (13% of Master's and 11% of Ph.D. theses from Rijeka, and 14% of Master's and 41% of Ph.D. theses from Zagreb). Also, 97 (6%) Master's and 129 (20%) Ph.D. theses that resulted in articles published in Current Contents journals (8% of Master's and 6% of Ph.D. theses from Rijeka, and 6% of Master's and 24% of Ph.D. theses from Zagreb). There was no significant difference between the two Universities with respect to published articles based on Master's theses, but there were significantly more articles from Ph.D. theses in Zagreb (p<0.001). Most of the theses resulted in a single publication (95%), 19 (5%) in 2, and 2 in 3 publications. Out of all 453 journal articles, 31% were published in Croatian and 69% in international journals. Most Croatian Master's and Ph.D. theses are not made available to the scientific community. There should be more institutional effort directed at the stimulation of postgraduate students to publish their scientific work.

Master Principals' Perceptions of the Impact of the Arkansas Leadership Academy's Master Principal Program on Leadership Practices, School Cultures and Student Achievement

ERIC Educational Resources Information Center

Peer, Diana

2012-01-01

A qualitative dissertation study was conducted to examine the impact of the Arkansas Leadership Academy's Master Principal Program through the perspective of those who have completed the entire program and attained designation as a Master Principal. A logic model for the Master Principal Program offered a context for the study. A review of…

Nonperturbative Dynamical Casimir Effect in Optomechanical Systems: Vacuum Casimir-Rabi Splittings

NASA Astrophysics Data System (ADS)

Macrı, Vincenzo; Ridolfo, Alessandro; Di Stefano, Omar; Kockum, Anton Frisk; Nori, Franco; Savasta, Salvatore

2018-01-01

We study the dynamical Casimir effect using a fully quantum-mechanical description of both the cavity field and the oscillating mirror. We do not linearize the dynamics, nor do we adopt any parametric or perturbative approximation. By numerically diagonalizing the full optomechanical Hamiltonian, we show that the resonant generation of photons from the vacuum is determined by a ladder of mirror-field vacuum Rabi splittings. We find that vacuum emission can originate from the free evolution of an initial pure mechanical excited state, in analogy with the spontaneous emission from excited atoms. By considering a coherent drive of the mirror, using a master-equation approach to take losses into account, we are able to study the dynamical Casimir effect for optomechanical coupling strengths ranging from weak to ultrastrong. We find that a resonant production of photons out of the vacuum can be observed even for mechanical frequencies lower than the cavity-mode frequency. Since high mechanical frequencies, which are hard to achieve experimentally, were thought to be imperative for realizing the dynamical Casimir effect, this result removes one of the major obstacles for the observation of this long-sought effect. We also find that the dynamical Casimir effect can create entanglement between the oscillating mirror and the radiation produced by its motion in the vacuum field, and that vacuum Casimir-Rabi oscillations can occur. Finally, we also show that all these findings apply not only to optomechanical systems, but also to parametric amplifiers operating in the fully quantum regime.

Time-dependent quantum transport: An efficient method based on Liouville-von-Neumann equation for single-electron density matrix

NASA Astrophysics Data System (ADS)

Xie, Hang; Jiang, Feng; Tian, Heng; Zheng, Xiao; Kwok, Yanho; Chen, Shuguang; Yam, ChiYung; Yan, YiJing; Chen, Guanhua

2012-07-01

Basing on our hierarchical equations of motion for time-dependent quantum transport [X. Zheng, G. H. Chen, Y. Mo, S. K. Koo, H. Tian, C. Y. Yam, and Y. J. Yan, J. Chem. Phys. 133, 114101 (2010), 10.1063/1.3475566], we develop an efficient and accurate numerical algorithm to solve the Liouville-von-Neumann equation. We solve the real-time evolution of the reduced single-electron density matrix at the tight-binding level. Calculations are carried out to simulate the transient current through a linear chain of atoms, with each represented by a single orbital. The self-energy matrix is expanded in terms of multiple Lorentzian functions, and the Fermi distribution function is evaluated via the Padè spectrum decomposition. This Lorentzian-Padè decomposition scheme is employed to simulate the transient current. With sufficient Lorentzian functions used to fit the self-energy matrices, we show that the lead spectral function and the dynamics response can be treated accurately. Compared to the conventional master equation approaches, our method is much more efficient as the computational time scales cubically with the system size and linearly with the simulation time. As a result, the simulations of the transient currents through systems containing up to one hundred of atoms have been carried out. As density functional theory is also an effective one-particle theory, the Lorentzian-Padè decomposition scheme developed here can be generalized for first-principles simulation of realistic systems.

Improved electromechanical master-slave manipulator

NASA Technical Reports Server (NTRS)

Forster, G.; Goertz, R.; Grimson, J.; Mingesz, D.; Potts, C.

1968-01-01

Electric master-slave manipulator uses force multiplication and allows the operator to remotely control the slave arm. Both the master and slave arms execute seven distinct motions by a specially designed force-reflecting servo having a one to one correspondence between the motion at the master and slave.

46 CFR 169.507 - Responsibility of master.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Responsibility of master. 169.507 Section 169.507... Lifesaving and Firefighting Equipment Lifesaving Equipment-General § 169.507 Responsibility of master. The master or operator shall ensure that the lifeboats, liferafts, davits, falls, personal flotation devices...

46 CFR 78.70-1 - Master's responsibility.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 3 2012-10-01 2012-10-01 false Master's responsibility. 78.70-1 Section 78.70-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS OPERATIONS De... Master's responsibility. (a) Before loading bulk grain, or similar combustible bulk cargo, the master...

46 CFR 169.507 - Responsibility of master.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Responsibility of master. 169.507 Section 169.507... Lifesaving and Firefighting Equipment Lifesaving Equipment-General § 169.507 Responsibility of master. The master or operator shall ensure that the lifeboats, liferafts, davits, falls, personal flotation devices...

46 CFR 169.507 - Responsibility of master.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Responsibility of master. 169.507 Section 169.507... Lifesaving and Firefighting Equipment Lifesaving Equipment-General § 169.507 Responsibility of master. The master or operator shall ensure that the lifeboats, liferafts, davits, falls, personal flotation devices...

46 CFR 169.507 - Responsibility of master.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Responsibility of master. 169.507 Section 169.507... Lifesaving and Firefighting Equipment Lifesaving Equipment-General § 169.507 Responsibility of master. The master or operator shall ensure that the lifeboats, liferafts, davits, falls, personal flotation devices...

46 CFR 78.70-1 - Master's responsibility.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 3 2014-10-01 2014-10-01 false Master's responsibility. 78.70-1 Section 78.70-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS OPERATIONS De... Master's responsibility. (a) Before loading bulk grain, or similar combustible bulk cargo, the master...

46 CFR 78.70-1 - Master's responsibility.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 3 2013-10-01 2013-10-01 false Master's responsibility. 78.70-1 Section 78.70-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS OPERATIONS De... Master's responsibility. (a) Before loading bulk grain, or similar combustible bulk cargo, the master...

46 CFR 169.507 - Responsibility of master.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Responsibility of master. 169.507 Section 169.507... Lifesaving and Firefighting Equipment Lifesaving Equipment-General § 169.507 Responsibility of master. The master or operator shall ensure that the lifeboats, liferafts, davits, falls, personal flotation devices...

Experimental and theoretical investigation of the elastic moduli of silicate glasses and crystals

NASA Astrophysics Data System (ADS)

Philipps, Katharina; Stoffel, Ralf Peter; Dronskowski, Richard; Conradt, Reinhard

2017-02-01

A combined quantum-mechanical and thermodynamic approach to the mechanical properties of multicomponent silicate glasses is presented. Quantum chemical calculations based on density-functional theory (DFT) on various silicate systems were performed to explore the crystalline polymorphs existing for a given chemical composition. These calculations reproduced the properties of known polymorphs even in systems with extensive polymorphism, like MgSiO3. Properties resting on the atomic and electronic structure, i.e., molar volumes (densities) and bulk moduli were predicted correctly. The theoretical data (molar equilibrium volumes, bulk moduli) were then used to complement the available experimental data. In a phenomenological evaluation, experimental data of bulk moduli, a macroscopic property resting on phononic structure, were found to linearly scale with the ratios of atomic space demand to actual molar volume in a universal way. Silicates ranging from high-pressure polymorphs to glasses were represented by a single master line. This suggests that above the Debye limit (in practice: above room temperature), the elastic waves probe the short range order coordination polyhedra and their next-neighbor linkage only, while the presence or absence of an extended translational symmetry is irrelevant. As a result, glasses can be treated - with respect to the properties investigated - as commensurable members of polymorphic series. Binary glasses fit the very same line as their one-component end-members, again both in the crystalline and glassy state. Finally, it is shown that the macroscopic properties of multicomponent glasses also are linear superpositions of the properties of their constitutional phases (as determined from phase diagrams or by thermochemical calculations) taken in their respective glassy states. This is verified experimentally for heat capacities and Young’s moduli of industrial glass compositions. It can be concluded, that the combined quantum mechanical and thermochemical approach is a truly quantitative approach for the design of glasses with desired mechanical properties, e.g., for the development of high-modulus glasses.

Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning.

NASA Astrophysics Data System (ADS)

Uemura, Yasutomo

RENiO3 (RE = rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or hydrostatic pressure (V2O3) , they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. We demonstrate through muon spin relaxation/rotation (μSR) experiments that the QPT in RENiO3 and V2O3 is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These two cases correspond to the band-width tuning of Mott transitions, and also associated with structural phase transitions, Volume evolutions of antiferromagnetic transition from μSR will be compared to those of structure by x-ray and metallicity by nano optics, in first-order thermal Mott transition in a V2O3 film at ambient pressure. These results will be compared to the process of destruction of magnetic order in another Mott transition system Ba(Co,Ni)S2 in ``filling control'' without structural transition, and in parent compounds of high-Tc cuprates and Fe-based superconductors. We will also discuss roles of first-order quantum transition in generating soft modes relevant to magnetic resonance mode in unconventional superconductors. Work performed in collaboration with the groups of: J.A. Alonso (Madrid), H. Kageyama (Kyoto). E. Morenzoni (PSI), G.M. Luke (McMaster), C.Q. Jin (IOP Beijing), F.L. Ning (Zhejian), S.J.L. Billinge (Columbia), S. Shamoto, W. Higemoto (JAEA), A. Fujimori (Tokyo), A. Gauzzi (Paris), R. de Renzi (Parma), G. Kotliar (Rutgers), M. Imada (Tokyo), D. Basov (UCSD), I, Schuller (UCSD). supported by NSF DMR-1610633 and DMR-1436095 (DMREF).

Replication of surface features from a master model to an amorphous metallic article

DOEpatents

Johnson, William L.; Bakke, Eric; Peker, Atakan

1999-01-01

The surface features of an article are replicated by preparing a master model having a preselected surface feature thereon which is to be replicated, and replicating the preselected surface feature of the master model. The replication is accomplished by providing a piece of a bulk-solidifying amorphous metallic alloy, contacting the piece of the bulk-solidifying amorphous metallic alloy to the surface of the master model at an elevated replication temperature to transfer a negative copy of the preselected surface feature of the master model to the piece, and separating the piece having the negative copy of the preselected surface feature from the master model.

Component Control System for a Vehicle

NASA Technical Reports Server (NTRS)

Lee, Chunhao J. (Inventor); Fraser-Chanpong, Nathan (Inventor); Vitale, Robert L. (Inventor); Akinyode, Akinjide Akinniyi (Inventor); Dawson, Andrew D. (Inventor); Guo, Raymond (Inventor); Waligora, Thomas M. (Inventor); Spain, Ivan (Inventor); Bluethmann, William J. (Inventor); Reed, Ryan M. (Inventor)

2016-01-01

A vehicle includes a chassis, a modular component, and a central operating system. The modular component is supported by the chassis. The central operating system includes a component control system, a primary master controller, and a secondary master controller. The component control system is configured for controlling the modular component. The primary and secondary master controllers are in operative communication with the component control system. The primary and secondary master controllers are configured to simultaneously transmit commands to the component control system. The component control system is configured to accept commands from the secondary master controller only when a fault occurs in the primary master controller.

48 CFR 14.203-3 - Master solicitation.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Master solicitation. 14... CONTRACTING METHODS AND CONTRACT TYPES SEALED BIDDING Solicitation of Bids 14.203-3 Master solicitation. The master solicitation is provided to potential sources who are requested to retain it for continued and...

33 CFR 385.30 - Master Implementation Sequencing Plan.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Master Implementation Sequencing... Incorporating New Information Into the Plan § 385.30 Master Implementation Sequencing Plan. (a) Not later than... of Environmental Protection, and other Federal, State, and local agencies, develop a Master...

48 CFR 14.203-3 - Master solicitation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Master solicitation. 14... CONTRACTING METHODS AND CONTRACT TYPES SEALED BIDDING Solicitation of Bids 14.203-3 Master solicitation. The master solicitation is provided to potential sources who are requested to retain it for continued and...

33 CFR 385.30 - Master Implementation Sequencing Plan.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Master Implementation Sequencing... Incorporating New Information Into the Plan § 385.30 Master Implementation Sequencing Plan. (a) Not later than... of Environmental Protection, and other Federal, State, and local agencies, develop a Master...

33 CFR 385.30 - Master Implementation Sequencing Plan.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Master Implementation Sequencing... Incorporating New Information Into the Plan § 385.30 Master Implementation Sequencing Plan. (a) Not later than... of Environmental Protection, and other Federal, State, and local agencies, develop a Master...

48 CFR 14.203-3 - Master solicitation.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Master solicitation. 14... CONTRACTING METHODS AND CONTRACT TYPES SEALED BIDDING Solicitation of Bids 14.203-3 Master solicitation. The master solicitation is provided to potential sources who are requested to retain it for continued and...

48 CFR 14.203-3 - Master solicitation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 1 2014-10-01 2014-10-01 false Master solicitation. 14... CONTRACTING METHODS AND CONTRACT TYPES SEALED BIDDING Solicitation of Bids 14.203-3 Master solicitation. The master solicitation is provided to potential sources who are requested to retain it for continued and...

48 CFR 14.203-3 - Master solicitation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 1 2013-10-01 2013-10-01 false Master solicitation. 14... CONTRACTING METHODS AND CONTRACT TYPES SEALED BIDDING Solicitation of Bids 14.203-3 Master solicitation. The master solicitation is provided to potential sources who are requested to retain it for continued and...

Master Skills Check List and Diagnostics.

ERIC Educational Resources Information Center

Cherokee Nation of Oklahoma, Tahlequah.

This publication contains master skills checklists originating from a project to develop instructional materials which are geared to individualized, self-paced learning strategies for Cherokee adults. These checklists break down learning into discrete components that can be sequentially mastered by the student. The master skills checklists are a…

What about Master's Students? The Master's Student Persistence Model

ERIC Educational Resources Information Center

Cohen, Kristin E.

2012-01-01

This study was designed to investigate the factors that affect master's student persistence in the United States. More specifically, this study explored whether the following factors: students' background, institution's, academic, environmental and psychological influences, had a significant effect on whether a master's student persisted and/or…

The development of method for continuous improvement of master file of the nursing practice terminology.

PubMed

Tsuru, Satoko; Okamine, Eiko; Takada, Aya; Watanabe, Chitose; Uchiyama, Makiko; Dannoue, Hideo; Aoyagi, Hisae; Endo, Akira

2009-01-01

Nursing Action Master and Nursing Observation Master were released from 2002 to 2008. Two kinds of format, an Excel format and a CSV format file are prepared for maintaining them. Followings were decided as a basic rule of the maintenance: newly addition, revision, deletion, the numbering of the management and a rule of the coding. The master was developed based on it. We do quality assurance for the masters using these rules.

MASTER follow up observation of MAXIJ1727-203

NASA Astrophysics Data System (ADS)

Lipunov, V.; Buckley, D.; Rebolo, R.; Serra-Ricart, M.; Kornilov, V.; Gorbovskoy, E.; Tiurina, N.; Balanutsa, P.; Gorbunov, I.; Kuznetsov, A.; Vladimirov, V.; Gress, O.; Pogrosheva, T.; Vlasenko, D.

2018-06-01

MASTER Global Robotic Net observed MAXI X-ray transient source ( T. Yoneyama et al. ATEL #11683) RA,Dec(2000)=17 27 53, -20 23 20 +-0.33d. We confirm GROND OT ( Arne Rau et al. ATEL #11690) MASTER-IAC auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) detected MASTER OT J172829.90-202255.91 (1sigma 0.7arcsec) on 2018-06-05 21:52:53.344 (10exp.

Legitimizing and Reclaiming Master's Training and Education in Counseling Psychology: An Urgent Concern

ERIC Educational Resources Information Center

Palmer, Laura K.

2013-01-01

Jackson and Scheel aptly elucidate the relevance of master's level counselor training programs for counseling psychology doctoral training programs, highlighting key antecedents of the current critical period in our relationship. Counseling psychology has an essential role in the professional lineage of counseling master's programs. Master's…

Developing "Masterity": The "Habitus" of Lifelong Learning

ERIC Educational Resources Information Center

Chang, Wonsup; Koo, Yoojeong

2017-01-01

This paper considers "masters" as the ideal archetype of workers. Here, the term "master" includes not only those who are in traditional handcrafting or manufacturing industry, but also who work in various fields such as information technology, medicine, arts, and so on. To explore the lifelong learning of masters, we conducted…

14 CFR 65.119 - Master parachute rigger certificate: Experience, knowledge, and skill requirements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false Master parachute rigger certificate... CREWMEMBERS Parachute Riggers § 65.119 Master parachute rigger certificate: Experience, knowledge, and skill requirements. An applicant for a master parachute rigger certificate must meet the following requirements: (a...

21 CFR 111.123 - What quality control operations are required for the master manufacturing record, the batch...

Code of Federal Regulations, 2012 CFR

2012-04-01

... the master manufacturing record, the batch production record, and manufacturing operations? 111.123... for Quality Control § 111.123 What quality control operations are required for the master... for the master manufacturing record, the batch production record, and manufacturing operations must...

28 CFR 52.01 - Civil proceedings: Special master, pretrial, trial, appeal.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Civil proceedings: Special master...) PROCEEDINGS BEFORE U.S. MAGISTRATE JUDGES § 52.01 Civil proceedings: Special master, pretrial, trial, appeal... as special master, if the attorney, with the concurrence of his or her supervisor, determines that...

46 CFR 78.30-20 - Master's and officer's responsibility.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 3 2011-10-01 2011-10-01 false Master's and officer's responsibility. 78.30-20 Section... OPERATIONS Lookouts, Pilothouse Watch, Patrolmen, and Watchmen § 78.30-20 Master's and officer's responsibility. (a) Nothing in this part shall exonerate any master or officer in command from the consequences...

14 CFR 27.1361 - Master switch.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Master switch. 27.1361 Section 27.1361... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1361 Master switch. (a) There must be a master switch arrangement to allow ready disconnection of each electric power source...

46 CFR 196.80-1 - Master's responsibility.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Master's responsibility. 196.80-1 Section 196.80-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OCEANOGRAPHIC RESEARCH VESSELS OPERATIONS Explosive Handling Plan § 196.80-1 Master's responsibility. (a) It shall be the responsibility of the master...

33 CFR 157.47 - Information for master.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Information for master. 157.47 Section 157.47 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... Vessel Operation § 157.47 Information for master. A master or person in charge of a new vessel shall...

33 CFR 104.205 - Master.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Master. 104.205 Section 104.205... SECURITY: VESSELS Vessel Security Requirements § 104.205 Master. (a) Nothing in this part is intended to permit the Master to be constrained by the Company, the vessel owner or operator, or any other person...

28 CFR 52.01 - Civil proceedings: Special master, pretrial, trial, appeal.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Civil proceedings: Special master...) PROCEEDINGS BEFORE U.S. MAGISTRATE JUDGES § 52.01 Civil proceedings: Special master, pretrial, trial, appeal... as special master, if the attorney, with the concurrence of his or her supervisor, determines that...

45 CFR 2400.62 - Evidence of master's degree.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 45 Public Welfare 4 2014-10-01 2014-10-01 false Evidence of master's degree. 2400.62 Section 2400... FELLOWSHIP FOUNDATION FELLOWSHIP PROGRAM REQUIREMENTS Special Conditions § 2400.62 Evidence of master's... indicates that he or she has secured an approved master's degree as set forth in the Fellow's original Plan...

28 CFR 52.01 - Civil proceedings: Special master, pretrial, trial, appeal.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Civil proceedings: Special master...) PROCEEDINGS BEFORE U.S. MAGISTRATE JUDGES § 52.01 Civil proceedings: Special master, pretrial, trial, appeal... as special master, if the attorney, with the concurrence of his or her supervisor, determines that...

46 CFR 196.80-1 - Master's responsibility.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Master's responsibility. 196.80-1 Section 196.80-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OCEANOGRAPHIC RESEARCH VESSELS OPERATIONS Explosive Handling Plan § 196.80-1 Master's responsibility. (a) It shall be the responsibility of the master...

33 CFR 104.205 - Master.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Master. 104.205 Section 104.205... SECURITY: VESSELS Vessel Security Requirements § 104.205 Master. (a) Nothing in this part is intended to permit the Master to be constrained by the Company, the vessel owner or operator, or any other person...

46 CFR 78.30-20 - Master's and officer's responsibility.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 3 2010-10-01 2010-10-01 false Master's and officer's responsibility. 78.30-20 Section... OPERATIONS Lookouts, Pilothouse Watch, Patrolmen, and Watchmen § 78.30-20 Master's and officer's responsibility. (a) Nothing in this part shall exonerate any master or officer in command from the consequences...

14 CFR 27.1361 - Master switch.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Master switch. 27.1361 Section 27.1361... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1361 Master switch. (a) There must be a master switch arrangement to allow ready disconnection of each electric power source...

33 CFR 104.205 - Master.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Master. 104.205 Section 104.205... SECURITY: VESSELS Vessel Security Requirements § 104.205 Master. (a) Nothing in this part is intended to permit the Master to be constrained by the Company, the vessel owner or operator, or any other person...

33 CFR 157.47 - Information for master.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Information for master. 157.47 Section 157.47 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... Vessel Operation § 157.47 Information for master. A master or person in charge of a new vessel shall...

21 CFR 111.123 - What quality control operations are required for the master manufacturing record, the batch...

Code of Federal Regulations, 2013 CFR

2013-04-01

... the master manufacturing record, the batch production record, and manufacturing operations? 111.123... for Quality Control § 111.123 What quality control operations are required for the master... for the master manufacturing record, the batch production record, and manufacturing operations must...

33 CFR 157.47 - Information for master.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Information for master. 157.47 Section 157.47 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... Vessel Operation § 157.47 Information for master. A master or person in charge of a new vessel shall...

46 CFR 78.30-20 - Master's and officer's responsibility.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 3 2013-10-01 2013-10-01 false Master's and officer's responsibility. 78.30-20 Section... OPERATIONS Lookouts, Pilothouse Watch, Patrolmen, and Watchmen § 78.30-20 Master's and officer's responsibility. (a) Nothing in this part shall exonerate any master or officer in command from the consequences...

21 CFR 111.123 - What quality control operations are required for the master manufacturing record, the batch...

Code of Federal Regulations, 2011 CFR

2011-04-01

... the master manufacturing record, the batch production record, and manufacturing operations? 111.123... for Quality Control § 111.123 What quality control operations are required for the master... for the master manufacturing record, the batch production record, and manufacturing operations must...

21 CFR 820.181 - Device master record.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Device master record. 820.181 Section 820.181 Food... DEVICES QUALITY SYSTEM REGULATION Records § 820.181 Device master record. Each manufacturer shall maintain device master records (DMR's). Each manufacturer shall ensure that each DMR is prepared and approved in...

14 CFR 27.1361 - Master switch.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Master switch. 27.1361 Section 27.1361... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1361 Master switch. (a) There must be a master switch arrangement to allow ready disconnection of each electric power source...

46 CFR 78.30-20 - Master's and officer's responsibility.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 3 2014-10-01 2014-10-01 false Master's and officer's responsibility. 78.30-20 Section... OPERATIONS Lookouts, Pilothouse Watch, Patrolmen, and Watchmen § 78.30-20 Master's and officer's responsibility. (a) Nothing in this part shall exonerate any master or officer in command from the consequences...

46 CFR 196.80-1 - Master's responsibility.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Master's responsibility. 196.80-1 Section 196.80-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OCEANOGRAPHIC RESEARCH VESSELS OPERATIONS Explosive Handling Plan § 196.80-1 Master's responsibility. (a) It shall be the responsibility of the master...

21 CFR 820.181 - Device master record.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Device master record. 820.181 Section 820.181 Food... DEVICES QUALITY SYSTEM REGULATION Records § 820.181 Device master record. Each manufacturer shall maintain device master records (DMR's). Each manufacturer shall ensure that each DMR is prepared and approved in...

14 CFR 65.119 - Master parachute rigger certificate: Experience, knowledge, and skill requirements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 2 2014-01-01 2014-01-01 false Master parachute rigger certificate... CREWMEMBERS Parachute Riggers § 65.119 Master parachute rigger certificate: Experience, knowledge, and skill requirements. An applicant for a master parachute rigger certificate must meet the following requirements: (a...

46 CFR 196.80-1 - Master's responsibility.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Master's responsibility. 196.80-1 Section 196.80-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OCEANOGRAPHIC RESEARCH VESSELS OPERATIONS Explosive Handling Plan § 196.80-1 Master's responsibility. (a) It shall be the responsibility of the master...

45 CFR 2400.62 - Evidence of master's degree.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 45 Public Welfare 4 2013-10-01 2013-10-01 false Evidence of master's degree. 2400.62 Section 2400... FELLOWSHIP FOUNDATION FELLOWSHIP PROGRAM REQUIREMENTS Special Conditions § 2400.62 Evidence of master's... indicates that he or she has secured an approved master's degree as set forth in the Fellow's original Plan...

45 CFR 2400.62 - Evidence of master's degree.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 45 Public Welfare 4 2012-10-01 2012-10-01 false Evidence of master's degree. 2400.62 Section 2400... FELLOWSHIP FOUNDATION FELLOWSHIP PROGRAM REQUIREMENTS Special Conditions § 2400.62 Evidence of master's... indicates that he or she has secured an approved master's degree as set forth in the Fellow's original Plan...

33 CFR 104.205 - Master.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Master. 104.205 Section 104.205... SECURITY: VESSELS Vessel Security Requirements § 104.205 Master. (a) Nothing in this part is intended to permit the Master to be constrained by the Company, the vessel owner or operator, or any other person...

33 CFR 157.47 - Information for master.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Information for master. 157.47 Section 157.47 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... Vessel Operation § 157.47 Information for master. A master or person in charge of a new vessel shall...

46 CFR 196.80-1 - Master's responsibility.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Master's responsibility. 196.80-1 Section 196.80-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OCEANOGRAPHIC RESEARCH VESSELS OPERATIONS Explosive Handling Plan § 196.80-1 Master's responsibility. (a) It shall be the responsibility of the master...

28 CFR 52.01 - Civil proceedings: Special master, pretrial, trial, appeal.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Civil proceedings: Special master...) PROCEEDINGS BEFORE U.S. MAGISTRATE JUDGES § 52.01 Civil proceedings: Special master, pretrial, trial, appeal... as special master, if the attorney, with the concurrence of his or her supervisor, determines that...