Relaxation and storage of multiparticle entangled states of atoms in a collective thermostat

Multiparticle entangled states that are the generalization of the W class states and can be reduced to Dicke states are considered. The master equation describing the collective decay of atoms in a cavity is derived for the Tavis-Cummings model in the dispersive limit. The entangled states of atoms that are retained in the process of collective decay are found. The scheme for recording and storage of these states in a collective thermostat is presented.     

On relaxation of entangled states in a collective thermostat

A kinetic equation describing collective relaxation process in the dispersion limit is derived for an ensemble of two-level atoms placed in a cavity and interacting with one cavity mode. Multiatom entangled states belonging to the set of Dicke states and insensitive to collective decay are found. A scheme for recording, storing, and reading these states with participation of spatially multimode light is reported.     

Relaxation of an atom and a cavity mode in an entangled environment

The master equation is derived for an atom and a single high-Q cavity mode interacting with the bath modes produced by a two-mode broadband source based on two degenerate optical parametric oscillators. The relaxation superoperator, found in the resonant and dispersive limits, contains new terms describing correlations between the atom and the cavity mode. Collective coherent states are introduced to show that squeezed states of the atom-cavity subsystem are generated via interaction with an entangled environment. It is shown that a correlated initial state of the atom and the cavity mode manifests itself in two cavity QED phenomena: spontaneous atomic emission in the strong-coupling regime and population inversion in the Jaynes-Cummings model.     

Lorentz gas interacting with an inhomogeneous thermostat

The equilibrium distribution of a Lorentz gas (“electrons”) interacting with an inhomogenous thermostat (“atoms”) is examined with consideration of 1) the concept of volumes available and forbidden for the gas particles and 2) the solution of the kinetic equation. Analytical calculations for “electrons” and “atoms” repelling each other with the force ≈r⁻⁵ (where r is the distance between the particles) have shown that the coordinate- and velocity-dependent variables in the distribution function cannot be separated. In particular, this leads to the dependence of the average kinetic energy per “electron” on the coordinate: it is higher in the region with higher density of the “atoms”. It is assumed that the Gibbs distribution does not describe the properties of the system under consideration, because in this case the interaction between the system and thermostat cannot be considered small. Scientific-Research Physical-Technical Institute at N. I. Lobachevskii Nizhnii Novgorod State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 38–43, June, 1999.     

Coherence of an entangled exciton-photon state

We study the effect of the exciton fine-structure splitting on the polarization entanglement of photon pairs produced by the biexciton cascade in a quantum dot. Entanglement persists despite separations between the intermediate energy levels of up to 4 microeV. Measurements show that entanglement of the photon pair is robust to the dephasing of the intermediate exciton state responsible for the first-order coherence time of either single photon. We present a theoretical framework incorporating the effects of spin scattering, background light, and dephasing. We distinguish between the first-order coherence time, and a parameter which we measure for the first time and define as the cross-coherence time.     

用非最大纠缠信道对任意二粒子纠缠态的量子秘密分享

提出一个对任意二粒子纠缠态在N者之间的量子秘密分享方案,该方案利用非最大纠缠Einstein-Podolsky-Rosen(EPR)对作为量子信道,利用广义的贝尔基进行测量.接收者通过引入辅助粒子,并对其做选择性测量,就会概率性地得到最初的量子态. 关键词： 非最大纠缠的Einstein-Podolsky-Rosen(EPR)对 广义的贝尔测量     

Bose-Einstein condensation with an entangled order parameter

We propose a practically accessible non-mean-field ground state of Bose-Einstein condensation, which occurs in an interspecies two-particle entangled state, and is thus described by an entangled order parameter. A suitably defined entanglement entropy is used as the characterization of the non-mean-field nature, and is found to persist in a wide parameter regime. The interspecies entanglement leads to novel interference terms in the dynamical equations governing the single-particle orbital wave function. Experimental feasibility and several methods of probe are discussed. We urge the study of multichannel scattering between different species of atoms.     

Tripartite entangled state,tripartite entangled Wigner operator and their generalization to an n-mode case

For entangled three particles one should treat their wave function as a whole.There is no physical meaning talking about the wave function(or Wigner function) for any one of the tripartite,and therefore considering the entangled Wigner function(Wigner operator) is of necessity.In this paper,we introduce a pair of mutually conjugate tripartite entangled state representations for defining the Wigner operator of entangled tripartite.Its marginal distributions and the Wigner function of the three-mode squeezed vacuum state are presented.Deriving wave function from its corresponding tripartite entangled Wigner function is also discussed.Moreover,through establishing the n-mode entangled state representation,we introduce the n-mode entangled Wigner operator,which would be more generally useful in quantum physics.     

Quantum statistics of radiation in thermostat

The influence of thermal noise on subpoisson statistics of the one-mode field is researched. The equilibrium distribution of subpoisson states is shown to have some subpoisson properties. The subpoisson effect in the evolution of the superposition of coherent signal and thermal noise depends on the field frequency, temperafure and initial signal amplitude.The present paper is dedicated to the memory of Prof. Marian Gmitro, a well-known specialist in nuclear physics untimely passed away. Being a man of great learning, in recent years he displayed an increased interest in achievements of quantum optics, and in particular, in their possible application to nuclear physics problems.Dedicated to the memory of M. Gmitro.     

远程控制纠缠原子的偶极压缩

考虑初始处于EPR态的两个二能级原子A、B,将B原子注入处于真空态和单光子态的叠加态的腔中,演化一段时间后,对B原子进行选择性测量,通过选择合适的腔场初始叠加状态和演化时间,可控制原子A的偶极矩压缩效应.     

Equilibrium statistical distributions for subchains in an entangled polymer melt

In de Gennes-Doi-Edwards theory for entangled polymeric melts, a length scale r₀ is introduced, giving the equilibrium mesh size of the physical network of chains. Each polymer molecule is then represented as a random walk, with a step size r₀ (a “subchain”, made up of n₀ Kuhn segments) dictated by the existence of entanglements. Progressing from this simple picture, an issue that has been constantly overlooked so far, despite its potential relevance, is that of finite-size effects at the de Gennes-Doi-Edwards characteristic length scale. Actually, since a subchain in a melt is a “small”, nonmacroscopic system, fluctuations of both its length and its number of Kuhn segments are certainly nonnegligible. An ad hoc theoretical treatment from nonstandard (nano) statistical mechanics and thermodynamics seems then required, to find the anticipated equilibrium statistical distributions of the subchain population. In this contribution, we carefully discuss this topic. Some predictions from the nonstandard fluctuation-inclusive approach on the statistics of subchains are here obtained, and compared with existing simulations, even down to the atomistic level.     

一个传送原子纠缠态的新方案

本文提出一个通过原子和腔场相互作用传送未知原子纠缠态的新方案,并且成功概率为100%.在这个方案里,我们主要利用两个原子用来接受被传送的原子纠缠态以及一个双模腔作为量子通道.由于腔场的两个模具有不同的频率和正交极化,因此这两个模能够被区分,并且处于腔场的不同区域.原子和腔场通过J-C哈密顿量发生共振相互作用,当原子和其中一个模相互作用时,另外一个模不受影响.该方案既不需要贝尔态测量,也不需要任何操作重构纠缠初态.这个方案也可以推广到传送N个原子的纠缠态.     

Quantum teleportation of an Einstein-Podolsy-Rosen pair using an entangled three-particle state

Quantum teleportation of an Einstein-Podolsky-Rosen pair using maximally entangled triplets to two receivers is studied. The projection basis for combined three-particle measurements, from the results of which the unknown state can be reconstructed, is found. The basis contains states where only two of the three particles are maximally entangled.     

Quantum teleportation of an entangled pair for continuous variables

The teleportation of a two-particle entangled state, using a Greenberger-Horne-Zeilinger triplet, for continuous variables is studied. The basis for joint three-particle measurements is found, where the vectors describe the states in which only two of three particles are entangled. It represents the measurement of the momentum of one particle and the difference of coordinates and the sum of momenta of the two other particles. An optical realization of this scheme is presented, which uses squeezed states of light and reduces the measurement of momentum and coordinate to the detection of quadrature operators of the electromagnetic field.     

Hole Spin Relaxation in an Ultrathin InAs Monolayer

We investigate the spin relaxation time of holes in an ultrathin neutral InAs monolayer （1.5 ML） and compare with that of electrons, using polarization-dependent time-resolved photoluminescence （TRPL） experiments. With excitation energies above the GaAs gap, we observe a rather slow relaxation of holes （τ1h = 196± 17 ps） that is in the magnitude similar to electrons （t1e= 354 ± 32 ps） in this ultrathin sample. The results are in good agreement with earlier theoretical prediction, and the phonon scattering due to spin-orbit coupling is realized to play a dominant role in the carrier spin kinetics.     

Equilibrium dynamics in the nondiffusive regime of an entangled polymer blend

The dynamics of compositional fluctuations in a miscible, entangled homopolymer blend of poly(ethylene oxide) and poly(methyl methacrylate) were studied on length scales smaller than the polymer radii of gyration, and for times comparable to the polymers' disentanglement time. The measured relaxation rates are consistent with predictions of the reptation model, as expressed via the dynamic random-phase approximation. Moreover, the observed mode amplitudes allow for an estimate of the entanglement length in the blend.     

Probabilistic teleportation of an arbitrary three-particle state via a partial entangled four-particle state and a partial entangled pair

We present a scheme to probabilistically teleport an arbitrary and unknown three-particle state via a two-particle non-maximally entangled state and a four-particle non-maximally entangled state as the quantum channel. With the help of Bell-state measurements, an arbitrary three-particle state can be perfectly teleported if a receiver introduces a collective unitary transformation. All kinds of unitary transformations are given in greater detail. This scheme can be generalized to the teleportation of an arbitrary and unknown multiparticle state.