量子相干

量子相干不仅是量子力学中的一个基本概念,同时也是重要的量子信息处理的物理资源.随着基于资源理论框架的量子相干度量方案的提出,量子相干度的量化研究成为近年来人们关注的一个热点问题.量子相干作为一种物理资源也十分脆弱,极容易受到环境噪声的影响而产生退相干,因此开放系统中的量子相干演化和保持也是人们广泛关注的课题.另外,量子相干在量子多体系统、量子热动力学、量子生物学等领域也有着潜在的应用价值.本文介绍量子相干度量的资源理论框架和基于该框架定义的相对熵相干性、l1范数相干性、基于量子纠缠的相干性、基于凸顶结构的相干性和相干鲁棒性等量子相干度量函数,概述开放系统中量子相干演化的动力学行为、典型信道的量子相干产生和破坏能力以及量子相干的冻结等现象,同时例举量子相干在Deutsch-Jozsa算法、Grover算法以及量子多体系统相变问题研究等方面的重要应用.量子相干研究仍处于快速发展之中,期望本综述能为该领域的发展带来启示.     

用玻色化顶点算子实现与Zn对称的BelavinR矩阵相关的Z-F代数

根据Asai,Jimbo,Miwa和Pugai给出的玻色化的A⁽¹⁾_n－1面模型的顶点算子,用面顶点对应关系,得到了与Z_n对称的Belavin R矩阵相关的玻色化顶点算,它们实现了与这种R矩阵对应的Zamolodchikov-Fadeev代数.     

Entanglement of Superpositions of Orthogonal Maximally Entangled States

We study the entanglement properties of the superposed state of orthogonal maximally entangled states. It is shown that the superposed state is maximally entangled and the superposed state is separable. The relation between the superposed state and the mutually unbiased state is discussed.     

Z_n格点模型的量子仿射变形代数

应用两种不同的星三角关系及其对应的Ｂｏｌｔｚｍａｎｎ面权，通过反对称聚合，构造出了在椭圆情形下的ｑ变形仿射代数．     

Non-Markovian speedup dynamics control of the damped Jaynes-Cummings model with detuning

For a two-level atom in a lossy cavity, a scheme to manipulate the non-Markovian speedup dynamics has been proposed in the controllable environment(the lossy cavity field). We mainly focus on the effects of the qubit-cavity detuning ? and the qubit-cavity coupling strength κ on the non-Markovian speedup evolution of an open system. By controlling the environment, i.e., tuning ? and κ, two dynamical crossovers from Markovian to non-Markovian and from no-speedup to speedup are achieved. Furthermore, it is clearly found that increasing the coupling strength κ or detuning ? in some cases can make the environmental non-Markovianity stronger and hence can lead to faster evolution of the open system.     

平板光子晶体微腔缺陷模的计算

采用时域有限差分方法结合群论知识,得到平板光子晶体微腔的缺陷模分布.采用对称化边界条件,首先通过宽频脉冲求解微腔所具有的缺陷频率,其次,对于确定缺陷频率,采用窄频脉冲保证只能激发所要求解的-个模式,将空间的电磁场值进行离散傅立叶变换求解其模场分布.计算结果表明,该方法能求解出微腔所有的缺陷模式.     

Strong Superadditive Deficit of Coherence and Quantum Correlations Distribution

The definitions of strong superadditive deficit for relative entropy coherence and monogamy deficit of measurement-dependent global quantum discord are proposed.The equivalence between them is proved,which provides a useful criterion for the validity of the strong superadditive inequality of relative entropy coherence.In addition,the strong superadditive deficit of rela.tive entropy coherence is proved to be greater than or equal to zero under the condition that bipartite measurement-dependent global quantum discord(GQD)does not increase under the discarding of subsystems.Using the Monte Carlo method,it is shown that both the strong superadditive inequality of relative entropy coherence and the monogamy inequality of measurement-dependent GQD are established under general circumstances.The bipartite measurement-dependent GQD does not increase under the discarding of subsystems.The multipartite situation is also discussed in detail.     

Variational quantum simulation of thermal statistical states on a superconducting quantum processer

Quantum computers promise to solve finite-temperature properties of quantum many-body systems, which is generally challenging for classical computers due to high computational complexities. Here, we report experimental preparations of Gibbs states and excited states of Heisenberg $XX$ and $XXZ$ models by using a 5-qubit programmable superconducting processor. In the experiments, we apply a hybrid quantum-classical algorithm to generate finite temperature states with classical probability models and variational quantum circuits. We reveal that the Hamiltonians can be fully diagonalized with optimized quantum circuits, which enable us to prepare excited states at arbitrary energy density. We demonstrate that the approach has a self-verifying feature and can estimate fundamental thermal observables with a small statistical error. Based on numerical results, we further show that the time complexity of our approach scales polynomially in the number of qubits, revealing its potential in solving large-scale problems.     

An－1(1)面模型反射方程的多参数解

利用面型因式化L算子,通过An－1(1)面模型反射方程的对角解,构造了一个含有n+1个任意参数的非对角解.     

Quantum simulation and quantum computation of noisy-intermediate scale

In the past years, great progresses have been made on quantum computation and quantum simulation. Increasing the number of qubits in the quantum processors is expected to be one of the main motivations in the next years, while noises in manipulation of quantum states may still be inevitable even the precision will improve. For research in this direction, it is necessary to review the available results about noisy multiqubit quantum computation and quantum simulation. The review focuses on multiqubit state generations, quantum computational advantage, and simulating physics of quantum many-body systems. Perspectives of near term noisy intermediate-quantum processors will be discussed.