关于正则密度矩阵与正则Bloch方程的若干性质

量子Fisher张量的生成函数与Bloch表示

Generating function and Bloch representation for quantum Fisher tensor

提出Uhlmann相对振幅作为生成函数，通过参数微分得到量子Fisher张量；推导了基于Bloch表示的通用表达式，并应用于自旋系综，揭示了磁场三维欧几里得流形上的常数Ricci标量、真空爱因斯坦方程和宇宙常数。

Effect of thermal noise on atom-field interaction: Glauber-Lachs versus Mixing

Coherent signal containing thermal noise is a mixed state of radiation. There are two distinct classes of such states, a Gaussian state obtained by Glauber-Lachs mixing and a non-Gaussian state obtained by the canonical probabilistic mixing of thermal state and coherent state. Though both these versions are noise-included signal states, the effect of noise is less pronounced in the Glauber-Lachs version. Effects of these two distinct ways of noise addition is considered in the context of atom-field interaction; in particular, temporal evolution of population inversion and atom-field entangleme…

Polymer quantization versus the Snyder noncommutative space

We study a noncanonical Hilbert space representation of the polymer quantum mechanics. It is shown that Heisenberg algebra get some modifications in the constructed setup from which a generalized uncertainty principle will naturally come out. Although the extracted physical results are the same as those obtained from the standard canonical representation, the noncanonical representation may be notable in view of its possible connection with the generalized uncertainty theories suggested by string theory. In this regard, by considering an Snyder-deformed Heisenberg algebra we show that since th…

Canonical form of master equations and characterization of non-Markovianity

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 diagonalisation 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-Ma…

Local Versus Global Thermal States: Correlations and the Existence of Local Temperatures

We consider a quantum system consisting of a regular chain of elementary subsystems with nearest neighbor interactions and assume that the total system is in a canonical state with temperature $T$. We analyze under what condition the state factors into a product of canonical density matrices with respect to groups of $n$ subsystems each, and when these groups have the same temperature $T$. While in classical mechanics the validity of this procedure only depends on the size of the groups $n$, in quantum mechanics the minimum group size $n_{min}$ also depends on the temperature $T $! As examples…

自主光学布洛赫方程的热力学

Thermodynamics of autonomous optical Bloch equations

本文提出自主框架研究原子对驱动和热浴的反作用，定义工作和热量流动，改进第二定律表达。

相互作用玻色子的淬火动力学：广义相干态与多模 Glauber 态的比较

Quench dynamics of interacting bosons: generalized coherent states versus multi-mode Glauber states

本文比较相互作用玻色子淬火动力学中的 MMGS 与 GCS，导出二者时间演化关联函数的 Fourier 型关系，表明即使在热力学极限下其动力学自由能密度仍因 U(1) 对称性缺失而不同。

Spectral properties of quantum $N$-body systems versus chaotic properties of their mean field approximations

We present numerical evidence that in a system of interacting bosons there exists a correspondence between the spectral properties of the exact quantum Hamiltonian and the dynamical chaos of the associated mean field evolution. This correspondence, analogous to the usual quantum-classical correspondence, is related to the formal parallel between the second quantization of the mean field, which generates the exact dynamics of the quantum $N$-body system, and the first quantization of classical canonical coordinates. The limit of infinite density and the thermodynamic limit are then briefly disc…

Hermitian versus non-Hermitian representations for minimal length uncertainty relations

We investigate four different types of representations of deformed canonical variables leading to generalized versions of Heisenberg's uncertainty relations resulting from noncommutative spacetime structures. We demonstrate explicitly how the representations are related to each other and study three characteristically different solvable models on these spaces, the harmonic oscillator, the manifestly non-Hermitian Swanson model and an intrinsically noncommutative model with Poeschl-Teller type potential. We provide an analytical expression for the metric in terms of quantities specific to the g…