A quantum dissipative system in an anisotropic non-linear absorbing environment

A canonical quantization scheme is represented for a quantum system interacting with a non-linear absorbing environment. The environment is taken anisotropic and the main system is coupled to its environment through some coupling tensors of various ranks. The non-linear response equation of the environment against the motion of the main system is obtained. The non-linear Langevin-Schrödinger equation is concluded as the macroscopic equation of motion of the dissipative system. The effect of non-linearity of the environment is investigated on the spontaneous emission of an initially excited two-level atom imbedded in such an environment.     

石墨炉原子吸收法在农业环境监测中的应用

农业环境监测是环境监测领域的重要组成部分,是一项较为复杂的系统工程。石墨炉原子吸收法的高灵敏度、高选择性及其优良的微量分析技术,使其在农业环境监测中具有很好的应用价值。本文较全面地论述了农业环境监测的含义、农业环境分析的目的、作用以及监测分类、分析方法及流程等,建立了石墨炉原子吸收法在农业环境监测中的应用模板,对石墨炉分析的特点、方法、质量控制等进行了系统全面的分析研究。该方法在农业环境监测的应用中有一定的实际意义。     

Environment and initial state engineered dynamics of quantum and classical correlations

Based on an open exactly solvable system coupled to an environment with nontrivial spectral density, we connect the features of quantum and classical correlations with some features of the environment, initial states of the system, and the presence of initial system–environment correlations. Some interesting features not revealed before are observed by changing the structure of environment, the initial states of system, and the presence of initial system–environment correlations. The main results are as follows. (1) Quantum correlations exhibit temporary freezing and permanent freezing even at high temperature of the environment, for which the necessary and sufficient conditions are given by three propositions. (2) Quantum correlations display a transition from temporary freezing to permanent freezing by changing the structure of environment. (3) Quantum correlations can be enhanced all the time, for which the condition is put forward. (4) The one-to-one dependency relationship between all kinds of dynamic behaviors of quantum correlations and the initial states of the system as well as environment structure is established. (5) In the presence of initial system–environment correlations, quantum correlations under local environment exhibit temporary multi-freezing phenomenon. While under global environment they oscillate, revive, and damp, an explanation for which is given.     

Energy Formulas for Three Quantum Brownian Motion Models Obtained with the IEO Method

For three quantum Brownian motion models: a material particle immersed in environment; two entangled particles coupled to an environment with position coupling; and two entangled particles coupled to an environment involving both position and momentum coupling, we employ the Invariant Eigenoperator Method (IEO) to successfully derive their energy formulas.     

Quantum Teleportation Under the Effect of Dissipative Environment and Hamiltonian XY Model

By supposing that the quantum channel is affected by the Hamiltonian XY model, quantum teleportation is studied in the absence and presence of a dissipative environment. We find that the dynamics of the average of fidelity and entanglement of the channel depend on which qubits interact with the environment and magnitude of parameters of the Hamiltonian. In the case that the qubits of quantum channel interact with environment, a critical value of entanglement is needed to keep quantum advantage at infinite time. We also find that, the most destructive case is that the qubit to be teleported is subject to an environment. It is shown that quantum advantage may be lost even in the absence of an environment.     

Non-Markovian master equation for a system of Fermions interacting with an electromagnetic field

For a system of charged Fermions interacting with an electromagnetic field, we derive a non-Markovian master equation in the second-order approximation of the weak dissipative coupling. A complex dissipative environment including Fermions, Bosons and the free electromagnetic field is taken into account. Besides the well-known Markovian term of Lindblad’s form, that describes the decay of the system by correlated transitions of the system and environment particles, this equation includes new Markovian and non-Markovian terms proceeding from the fluctuations of the self-consistent field of the environment. These terms describe fluctuations of the energy levels, transitions among these levels stimulated by the fluctuations of the self-consistent field of the environment, and the influence of the time-evolution of the environment on the system dynamics. We derive a complementary master equation describing the environment dynamics correlated with the dynamics of the system. As an application, we obtain non-Markovian Maxwell-Bloch equations and calculate the absorption spectrum of a field propagation mode transversing an array of two-level quantum dots.     

All unital qubit channels are 4-noisy operations

We show that any unital qubit channel can be implemented by letting the input system interact unitarily with a four-dimensional environment in the maximally mixed state and then tracing out the environment. We also provide an example where the dimension of such an environment has to be at least 3.

     

Effect of refractive index of environment medium on electromagnetic mode density in photonic band gaps

The purpose of this work is to analyze the effect of the environmental medium on the density of mode (DOM) in a 1-D photonic crystal. The results show that for a symmetric environment, the DOM changes non-monotonously with an increase in the refractive index of the environment medium, while for an asymmetric environment, the DOM increases monotonously with an increase of the refractive index of the substrate. It is found that low DOM at midgap and high DOM at the band edge can be achieved simultaneously only when a photonic crystal works in an environment where the input medium and the substrate have the same refractive indices. The effect of the refractive index on the surrounding material on the band edge laser is also discussed. PACS 42.70.Qs; 71.20.Tx     

Relation Between Purity of an Open Qubit Dynamics and Its Initial Correlation with an Environment

Purity as a quantifier of an impact of environment on an open quantum system is studied for a qubit dephasingly interacting with its environment. We analyze how time evolution of the purity depends on initial states of the composite system both in the case of infinite and finite environments. It is shown that for a certain class of initial preparations, the purity of an evolving qubit state initially correlated with infinite environment can be greater than in the case of uncorrelated qubit-environment initial preparations. We identify a class of initial states leading to such desired outcome.     

The hazardous space particle environment

This paper is an introductory-level tutorial covering the charged particle environment in the Earth's magnetosphere and its effects on spacecraft. It provides an overview of radiation effects on spacecraft, trapped particle morphology, and the radiation environment     

Path integral approach to quantum diffusion in metals

A general formalism for a quantum particle moving in an environment based on the path integral formulation of quantum mechanics is presented. The environment can be the valence electron gas of a metal or the phonons of the host in which the particle moves, or both. The advantage of this approach is that it gives a direct space-time picture of the motion. Integrating out the coordinates of the environment an effective action for the particle is obtained. It consist of two parts. An adiabatic term, that is local in time (and as such describable as a potential), describing the influence of the fully relaxed environment on the particle, and a term that accounts for the dynamical part of the response of the environment due to the motion of the particle. As an example I have considered a particle moving in a tight binding band with an electron gas environment. Three energy scales play a role here. They are the bare hopping amplitude, the temperature and the inverse tunneling time (i.e. the time it takes the particle to tunnel from one site to the next). Note that the Fermi energy drops out of the problem. I find, as did Kondo in his recent theory, a decreasing diffusion constant as a function of temperature.     

宏观场与环境作用过程中的纠缠突然死亡与突然产生

研究了两个初始处于纠缠相干态上的宏观场各自独立地与一个环境相互作用的系统, 环境对腔场的影响只体现在腔场光子数的泄漏上. 采用共生纠缠(concurrence)度量两个宏观场间的纠缠, 并给出宏观场纠缠的解析解, 以分析这种系统中宏观场纠缠的动力学特性. 研究表明当场的初始平均光子数较大时, 即使很小的光子泄漏率也会导致腔场间出现纠缠突然死亡现象. 同时研究结果也表明光子从腔场泄漏到环境后会导致两环境间的纠缠突然产生, 而这种纠缠产生的时机直接与腔场的初始光子数相关. 本文还进一步发现在大光子数的情况下, 在任何时刻任意一个腔场与任意一个环境间都不会产生纠缠. 关键词： 纠缠相干态 环境 纠缠突然死亡 纠缠突然产生     

Diffusion of directed polymers in a strong random environment

We consider a system of random walks or directed polymers interacting with an environment which is random in space and time. It was shown by Imbrie and Spencer that in spatial dimensions three or above the behavior is diffusive if the directed polymer interacts weakly with the environment and if the random environment follows the Bernoulli distribution. Under the same assumption on the random environment as that of Imbrie and Spencer, we establish that in spatial dimensions four or above the behavior is still diffusive even when the directed polymer interacts strongly with the environment. More generally, we can prove that, if the random environment is bounded and if the supremum of the support of the distribution has a positive mass, then there is an integerd ₀ such that in dimensions higher thand ₀ the behavior of the random polymer is always diffusive.     

运用动态腔环境实现对原子自发辐射过程的调控

本文从理论上讨论了运用动态的腔环境实现对处于激发态的两能级原子自发辐射过程的调控.研究发现,周期性地改变与原子相互作用的腔环境导致电磁模式之间相互作用,产生电磁模式密度重新分配,并使得原子与腔环境之间的能量交换的频率以及能量耗散的速度发生改变;当腔环境的变化频率和原子、环境之间交换能量的过程保持相对一致时可以实现稳定的相干性演化,衰减效应受到显著的抑制,进而可以通过环境变化操纵相干态的演化. 关键词： 自发辐射 动态环境 量子调控     

Quantum decoherence due to non-linear dynamics of environment

We discuss quantum decoherence in an open system which couples with a non-linear environment with finite degrees of freedom. Even if the degrees of freedom of the environment are finite, the strong non-linearity of the environment is expected to destroy quantum coherence of the open system like a heat bath with infinite degrees of freedom. In order to demonstrate this fact, we use two-dimensional kicked rotors as the environment and investigate a master equation for a reduced density matrix which is obtained by coarse-graining the environmental degrees of freedom. Our numerical simulation shows that when the non-linearity of the environment exceeds a critical strength, quantum coherence of the open system is irreversibly destroyed. This decoherence is due to the uncorrelated response of the environment to the open system and is related to the chaotic property of the non-linear environment.     

Universal features of polymer shapes in crowded environments

We study the universal characteristics of the shape of a polymer chain in an environment with correlated structural obstacles, applying the field-theoretical renormalization group approach. Our results qualitatively indicate an increase of the asymmetry of the polymer shape in crowded environment comparing with the pure solution case.     

Excitation energy transfer in chromophore aggregates within a dissipative medium

The Redfield theory-based model of excitation energy transfer in chromophore ensembles within dissipative environment is proposed. Application of the multipole expansion to an operator of interaction between the chromophore molecules and the environment together with some assumptions about the latter led to the closed-form expressions for the elements of the dissipation tensor. These expressions relate the rates of transition between eigenstates of a chromophore ensemble with the spectral and electronic properties of an environment and the chromophore molecules. For several model cases the exact solution of the Redfield equations was obtained.     

Scaling Limits for Gradient Systems in Random Environment

It is well known that the hydrodynamic limit of an interacting particle system satisfying a gradient condition (such as the zero-range process or the symmetric simple exclusion process) is given by a possibly non-linear parabolic equation and the equilibrium fluctuations from this limit are given by a generalized Ornstein-Uhlenbeck process.We prove that in the presence of a symmetric random environment, these scaling limits also hold for almost every choice of the random environment, with an homogenized diffusion coefficient that does not depend on the realization of the random environment.     

Quantum process discrimination with information from environment

In quantum metrology we usually extract information from the reduced probe system but ignore the information lost inevitably into the environment. However, K. Mølmer[Phys. Rev. Lett. 114, 040401 (2015)] showed that the information lost into the environment has an important effect on improving the successful probability of quantum process discrimination. Here we reconsider the model of a driven atom coupled to an environment and distinguish which of two candidate Hamiltonians governs the dynamics of the whole system. We mainly discuss two measurement methods, one of which obtains only the information from the reduced atom state and the other obtains the information from both the atom and its environment. Interestingly, for the two methods the optimal initial states of the atom, used to improve the successful probability of the process discrimination, are different. By comparing the two methods we find that the partial information from the environment is very useful for the discriminations.     

Decoherence and classical behavior with a chaotic macroscopic environment

Quantum state diffusion approach to open system dynamics is used to study decoherence and dynamics of the pointer observable of an angular momentum system in interaction with a macroscopic nonlinear and dissipative environment. It is shown that dispersion of the pointer observable in the mixed state of the open system is clearly larger if the environment is classically chaotic then in the case of the environment with regular dynamics.