Optical Non-Reciprocity in Coupled Resonators by Detailed Balance

Inspired by the photosynthetic energy transfer process, a method to realize non-reciprocal optical transmission in an array of coupled resonators is theoretically proposed. The optical non-reciprocity of the coupled resonators arises from the frequency gradient between adjacent cavities and the interaction with the environment, which is similar to photosynthetic energy transfer. An increase in the frequency gradient or the number of the cavities can lead to better non-reciprocity. However, although a higher environment temperature will increase the total photon number in the coupled cavities, non-reciprocity will be weakened. All these findings can be well described by the detailed balance. The similarity between the noise-induced optical non-reciprocity and exciton energy transfer in natural photosynthesis is revealed by the discovery.     

基于新型超导电荷量子比特的几何量子门

超导量子系统被认为是最可能用于实现大规模量子计算、量子信息、以及量子存储等的物理系统之一.本文在一种特别设计的超导电荷比特的基础上,通过微波腔与超导比特的相互作用,探讨了在此系统中实现几何相单门以及非常规几何相两量子门的途径,并讨论了制备多量子比特最大纠缠态的方法.     

Strongly interacting ultracold quantum gases

This article reviews recent progresses in ultracold quantum gases, and it includes three subjects which are the Fermi gases across a Feshbach resonance, quantum gases in the optical lattices and the fast rotating quantum gases. In this article, we discuss many basic physics pictures and concepts in quantum gases, for examples, the resonant interaction, universality and condensation in the lowest Landau level; we introduce fundamental theoretical tools for studying these systems, such as mean-field theory for BEC-BCS crossover and for the boson Hubbard model; also, we emphasize the important unsolved problems in the forefront of this field, for instance, the temperature effect in optical lattices.      

Fast quantum state transfer and entanglement for cavity-coupled many qubits via dark pathways

Quantum state transfer (QST) and entangled state generation (ESG) are important building blocks for modern quantum information processing. To achieve these tasks, convention wisdom is to consult the quantum adiabatic evolution, which is time-consuming, and thus is of low fidelity. Here, using the shortcut to adiabaticity technique, we propose a general method to realize high-fidelity fast QST and ESG in a cavity-coupled many qubits system via its dark pathways, which can be further designed for high-fidelity quantum tasks with different optimization purpose. Specifically, with a proper dark pathway, QST and ESG between any two qubits can be achieved without decoupling the others, which simplifies experimental demonstrations. Meanwhile, ESG among all qubits can also be realized in a single step. In addition, our scheme can be implemented in many quantum systems, and we illustrate its implementation on superconducting quantum circuits. Therefore, we propose a powerful strategy for selective quantum manipulation, which is promising in cavity coupled quantum systems and could find many convenient applications in quantum information processing.     

Advances in Atomtronics

Atomtronics is a relatively new subfield of atomic physics that aims to realize the device behavior of electronic components in ultracold atom-optical systems. The fact that these systems are coherent makes them particularly interesting since, in addition to current, one can impart quantum states onto the current carriers themselves or perhaps perform quantum computational operations on them. After reviewing the fundamental ideas of this subfield, we report on the theoretical and experimental progress made towards developing externally-driven and closed loop devices. The functionality and potential applications for these atom analogs to electronic and spintronic systems is also discussed.     

量子隐形传态

量子隐形传态是目前量子信息中人们关注的热门课题之一，它是量子信息理论的重要组成部分，也是量子计算的基础。文章阐述了标准量子隐形传态和概率量子隐形传态的基本理论以及EPR效应，Bell基测量等相关的概念，同时给出一种实现隐形传态的量子电路，并介绍了当前理论与实验的研究进展。     

量子隐形传态

量子隐形传态是目前量子信息中人们关注的热门课题之一,它是量子信息理论的重要组成部分,也是量子计算的基础。文章阐述了标准量子隐形传态和概率量子隐形传态的基本理论以及EPR效应,Bell基测量等相关的概念,同时给出一种实现隐形传态的量子电路,并介绍了当前理论与实验的研究进展。     

核磁共振量子信息处理研究的新进展

过去的二十年中,量子信息相关研究取得了显著的进展,重要的理论和实验工作不断涌现.与其他量子信息处理系统相比,基于自旋动力学的核磁共振系统,不仅具有丰富而且成熟的控制技术,还拥有相干时间长、脉冲操控精确、保真度高等优点.这也是核磁共振体量子系统能够精确操控多达12比特的量子系统的原因.因此,核磁共振量子处理器在量子信息领域一直扮演着重要角色.本文介绍核磁共振量子计算的基本原理和一些新研究进展.研究的新进展主要包括量子噪声注入技术、量子机器学习在核磁共振平台上的实验演示、高能物理和拓扑序的量子模拟以及核磁共振量子云平台等.最后讨论了液态核磁共振的发展前景和发展瓶颈,并对未来发展方向提出展望.     

利用超导量子电路模拟拓扑量子材料

近年来,探索新的拓扑量子材料、研究拓扑材料的新奇物理性质成为凝聚态物理领域的一个热点.但是,由于合成、测量等手段的限制,人们难以在真实材料中实现和观测很多理论预言的材料及其物理性质,促使量子模拟日益成为研究量子多体系统的一个重要手段.作为全固态器件,超导量子电路是一个在扩展性、集成性、调控性上都具有巨大优势的人工量子系统,是实现量子模拟的重要方案.本文总结了利用超导量子电路对时间-空间反演对称性保护的拓扑半金属、Hopf-link半金属和Maxwell半金属等拓扑材料的量子模拟,显示出超导量子电路在模拟凝聚态物理系统方面具有广阔前景.     

Fast quantum search driven by environmental engineering

Studies have demonstrated that a joined complete graph is a typical mathematical model that can support a fast quantum search. In this paper, we study the implementation of joined complete graphs in atomic systems and realize a quantum search of runtime $O(\sqrt{N})$ based on this implementation with a success probability of 50%. Even though the practical systems inevitably interact with the surrounding environment, we reveal that a successful quantum search can be realized through delicately engineering the environment itself. We consider that our study will bring about a feasible way to realize quantum information processing including quantum algorithms in reality.     

Multiparty Quantum Secret Sharing Using Quantum Fourier Transform

A （n, n）-threshold scheme of multiparty quantum secret sharing of classical or quantum message is proposed based on the discrete quantum Fourier transform. In our proposed scheme, the secret message, which is encoded by using the forward quantum Fourier transform and decoded by using the reverse, is split and shared in such a way that it can be reconstructed among them only if all the participants work in concert. Fhrthermore, we also discuss how this protocol must be carefully designed for correcting errors and checking eavesdropping or a dishonest participant. Security analysis shows that our scheme is secure. Also, this scheme has an advantage that it is completely compatible with quantum computation and easier to realize in the distributed quantum secure computation.     

Quantum information transfer between topological and conventional charge qubits

We propose a scheme to realize coherent quantum information transfer between topological and conventional charge qubits. We first consider a hybrid system where a quantum dot(QD) is tunnel-coupled to a semiconductor Majorana-hosted nanowire(MNW) via using gated control as a switch, the information encoded in the superposition state of electron empty and occupied state can be transferred to each other through choosing the proper interaction time to make measurements.Then we consider another system including a double QDs and a pair of parallel MNWs, it is shown that the entanglement information transfer can be realized between the two kinds of systems. We also realize long distance quantum information transfer between two quantum dots separated by an MNW, by making use of the nonlocal fermionic level formed with the pared Majorana feimions(MFs) emerging at the two ends of the MNW. Furthermore, we analyze the teleportationlike electron transfer phenomenon predicted by Tewari et al. [Phys. Rev. Lett. 100, 027001(2008)] in our considered system.Interestingly, we find that this phenomenon exactly corresponds to the case that the information encoded in one QD just returns back to its original place during the dynamical evolution of the combined system from the perspective of quantum state transfer.     

Enhancing the security of quantum secret sharing against multiphoton attack

It is generally believed that nonorthogonal operations which can realize the state transformation between two nonorthogonal bases may ensure the security of many quantum communication protocols. However, in this paper, we present a powerful attack against quantum secret sharing protocols of these kinds. Applying entangled photons as fake signals, Eve can successfully steal the exact information without being revealed. We also give our effective modification to improve it. Under the suggested checking strategy, even to Eve's most general attack, it is robust and secure.     

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.     

量子理论若干基本问题研究的新进展

本文结合最近的典型量子物理实验 ,如用冷原子Bragg散射实现的“which way”实验 ,量子退相干过程的微腔QED检验和C60 分子的量子干涉等 ,比较系统地介绍了量子理论基本问题若干研究的新进展 ,特别强调了处于其核心的量子测量问题及其相关的基本概念和基本思想 ,如EPR佯谬和Bell不等式 ,量子退相干和量子纠缠。从理论和实验结合的角度 ,本文阐述了被测系统和测量仪器的相互作用怎样导致量子测量的一般动力学过程。由此还讨论了外部环境和内部运动怎样诱导量子退相干和量子耗散 ,对“薛定谔猫佯谬”和“宏观物体空间局域化描述”给出了可能的物理解释。最后 ,通过具体例子 ,本文简单地讨论了量子物理基本问题的研究结果对量子信息的应用     

利用光子回声技术产生光的三体纠缠态的研究

量子纠缠是实现量子通信和量子计算的重要资源,其中多体纠缠更是构建量子网络实现全局量子计算的基础。本文主要研究如何利用经典的光子回声技术实现光量子态的三体纠缠。在自由空间中向掺杂稀土离子的固态离子系综中射入经典光场,当离子体系达到相位重构条件时即可获得三束存在纠缠的量子光场。基于本方案纠缠产生的技术特点,发现其在提高量子中继器的工作效率上有着潜在的应用价值。     

低维纳米材料量子热输运与自旋热电性质 ——非平衡格林函数方法的应用

低维材料不断涌现的新奇性质吸引着科学研究者的目光. 除了电子的量子输运行为之外, 人们也陆续发现和确认了热输运中显著的量子行为, 如 热导低温量子化、声子子带、尺寸效应、瓶颈效应等. 这些小尺度体系的热输运性质可以很好地用非平衡格林函数来描述. 本文首先介绍了量子热输运的特性、声子非平衡格林函数方法及其在低维纳米材料中的研究进展; 其次回顾了近年来在 一系列低维材料中发现的热-自旋输运现象. 这些自旋热学现象展现了全新的热电转换机制, 有助于设计新型的热电转换器件, 同时也给出了用热产生自旋流的新途径; 最后介绍了线性响应理论以及在此理论框架下结合声子、电子非平衡格林函数方法进行的一些有益的探索. 量子热输运的研究对热效应基础研究以及声子学器件、能量转换器件的发展有着不可替代的重要作用.     

量子理论若干基本问题研究的新进展

本结合最后的典型量子物理实验,如用冷原子Bragg散射实现的“which-way”实验,量子退相干过程的微腔QED检验和C60分子的量子干涉等,比较系统地介绍了量子理论基本问题若干研究的新进展,特别强调了处于其核心的量子测量问题及其相关的基本概念和基本思想,如EPR佯谬和Bell不等式,量子退相干和量子纠缠,从理论和实验结合的角度本阐述了被测系统和测量仪器的相互作用怎样导致量子测量的一般动力学过程,由此还讨论了外部环境和内部运动怎样诱导量子退相干和量子耗散,对“薛定谔猫佯谬”和“宏观物体空间局域化描述”给出了可能的物理解释,最后,通过具体例子,本简单地讨论了量子物理基本问题的研究结果对量子信息的应用。