量子信息引论

文章在阐述量子信息的发展背景之后,介绍了量子纠缠、量子计算、量子密码、量子因特网、量子克隆、量子对策论等方面的内容,既阐述了相关的基本概念,也论及最新的研究进展。     

神奇的量子计算机

简要地介绍了量子计算机的原理和优点,还介绍了量子计算机的一些基本概念,有量子叠加,量子纠缠,量子位、量子逻辑门和量子并行计算。     

Does the Quantum Player Always Win the Classical One？

We study quantum games in which the players have different strategic spaces. We find that the player who can use a quantum strategic space does not always possess more payoffs than the player who is restricted to apply only classical strategies. We find the condition of the classical player getting more payoffs than the quantum player. We also find that the game exhibits intriguing structures.     

Controlled Teleportation of Multi-Qudit Quantum Information

We present a controlled teleportation scheme for teleporting an arbitrary superposition state of an M-qudit quantum system. The scheme employs only one entangled state as quantum channel, which consists of the qudits from Alice, Bob and every agent. The quantum operations used in the teleportation process are a series of qudit Bell measurements, single-qudit projective measurements, qudit H-gates, qudit-Pauli gates and qudit phase gates. It is shown that the original state can be restored by the receiver only on the condition that all the agents collaborate. If any agent does not cooperate, the original state can not be fully recovered.     

A New Quantum Secure Direct Communication Protocol Using Decoherence-Free Subspace

A new quantum secure direct communication （QSDC） protocol is proposed by using decoherence free subspace （DFS） to avoid insecurity of the present QSDC protocols in a quantum noise channel. This protocol makes it easily for Bob and Alice to find eavesdropping in channel because the collective dephasing noise disappears in DFS. The probability of successful attack by Eve in this protocol is smaller than in BB84 protocol. Thus this protocol realizes secure QSDC and is feasible with present-day technology.     

量子信息与计算

量子信息与计算是物理学目前研究的热门领域,本文简要地介绍量子计算的一些基本概念：量子纠缠、量子位、量子寄存器、量子并行计算和量子纠错,并介绍两种典型的量子信息技术：量子密码和量子传物。     

量子信息研究进展

量子信息论是经典信息论与量子力学相结合的新兴交叉学科,本综述了最子信息领域的研究进展。即包括了为人们所熟知的量子通信与量子计算领域,也包括了刚刚兴起的但却有巨大潜力的量子对策论等领域。本以介绍量子信息论的基本理论框架为主,同时也介绍了量子信息领域的实验研究进展。     

量子计算的研究进展

量子计算由于其强大的并行计算能力和可以有效的模拟量子行为的能力而日益受到人们的关注。本文介绍了量子计算的基本原理、实现量子计算的基本要求、量子计算的根本困难、可能的解决办法，以及当前的几个有希望实现量子计算的物理系统。最后介绍了我们课题组在分布式量子计算和基于固有耦合的编码量子计算的实验与理论方面的工作。     

Coherent Tunnelling in Coupled Quantum Wells under a Uniform Magnetic Field

Coherent tunnelling is studied in the framework of the effective mass approximation for an asymmetric coupled quantum well. The Hartree potential due to the electron-electron interaction is considered in our calculation. The effects of the longitudinal and transverse magnetic field on coherent tunnelling characteristics are discussed. It has been found that the external field plays an important role in modulating the electron states.     

量子通信

量子通信是经典通信和量子力学相结合的一门新兴交叉学科。文章综述了量子通信领域的研究进展，既包括人们所熟知的量子隐形传态、密集编码和量子密码学，也包括刚刚兴起但却有巨大潜力的量子通信复杂度和远程量子通信等领域。文章介绍了量子通信的基本理论框架，同时也涉及了这个领域最新的实验研究的进展。     

Quantum Phase Transition and Ferromagnetic Spin Correlation in Parallel Double Quantum Dots

We investigate electronic transport through a parallel double quantum dot （DQD） system with strong on-site Coulomb interaction, as well as the interdot tunnelling. By applying numerical renormalization group method, the ground state of the system and the transmission probability at zero temperature are obtained. For a system of quantum dots with degenerate energy levels and small interdot tunnel coupling, the spin correlations between the DQDs is ferromagnetic, and the ground state of the system is a spin-1 triplet state. The linear conductance will reach the unitary limit （2e^2/h） due to the Kondo effect at low temperature. As the interdot tunnel coupling increases, there is a quantum phase transition from ferromagnetic to anti-ferromagnetic spin correlation in DQDs and the linear conductance is strongly suppressed.     

量子博弈论及其应用

介绍了量子博弈理论及与经典博弈理论的关系，指出了量子博弈理论的优越性，及对现实物理世界的意义。     

Quantum Logic Networks for Probabilistic and Controlled Teleportation of Unknown Quantum States

We present simplification schemes for probabilistic and controlled teleportation of the unknown quantum states of both one particle and two particles and construct efficient quantum logic networks for implementing the new schemes by means of the primitive operations consisting of single-qubit gates, two-qubit controlled-not gates, Von Neumann measurement, and classically controlled operations. In these schemes the teleportation are not always successful but with certain probability.     

量子信息掩蔽

量子信息掩蔽是量子信息处理中的一个新兴概念,它将量子信息完全转移至各个量子实体的关联之中,从而使单个量子系统不再包含掩蔽前的任何信息。量子信息掩蔽在量子比特承诺、秘密共享等方面都具有重要的应用;然而与量子态的克隆、广播、隐藏等操作类似,人们无法使用一个普适的两体幺正演化来实现量子信息的掩蔽。本文系统地介绍近期量子信息掩蔽方向的一系列研究进展：首先描述了可实现量子信息掩蔽态集合的几何特征,给出掩蔽操作的实现方法,讨论了其在信息论中的含义以及与量子纠错码等概念的联系;然后介绍量子信息掩蔽的实验实现,展现量子信息掩蔽在高维体系等复杂系统中的可行性,并展示其在量子秘密共享和噪声免疫的量子通信等方面的应用。     

固态量子计算的若干重要物理问题研究

量子计算机拥有比经典计算机更为强大的计算能力．人们普遍认为量子计算机最终将会在固态系统中实现．文章介绍了一些有关固态量子计算的研究进展，其中包括超导电荷量子比特方案、几何量子计算、量子点量子比特及量子计算若干基本问题研究．最后给出了固态量子计算的发展趋势．     

量子信息科学在中国科学技术大学的兴起和发展

文章介绍了中国科学技术大学的量子信息科学研究是如何兴起和发展的;着重介绍了在量子信息的基础理论、量子密码、量子纠缠、量子隐形传态、量子处理器和量子信息的应用等方面所取得的研究成果.     

量子测量问题的研究及应用

文章结合最近完成的量子测量实验（如用冷原子Ｂｒａｇｇ散射实现的“ｗｈｉｃｈ－ｗａｙ”实验和用Ｃ６０分子完成的小系统量子干涉实验）,比较系统地介绍了量子测量问题及其相关的基本概念和基本思想,如量子相干、量子退相干和量子纠缠,从理论和实验结合的角度,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,由此探讨了“薛定谔猫佯谬”和“宏观物体空间局域化描述”的物理解释,最后,文章简单地描述了量子计算和量     

量子信息与计算

量子信息与计算是物理学目前研究的热门领域 .本文简要地介绍量子计算的一些基本概念 :量子纠缠、量子位、量子寄存器、量子并行计算和量子纠错 .并介绍两种典型的量子信息技术 :量子密码和量子传物 .     

Entanglement and Quantity in Quantum Space —— About Quantum Measurement （II）

As a continuation and extension of “quantity in phase space“ “quantity in quantum space“ is introduced. With that, the disappearing of quantum interference discussed in a previous paper [S. Du^err, et al., Nature 395 (1998) 33] is explained in the same spirit as our recent papers [Ren De-Ming, Commun. Theor. Phys. (Beijing, China) 41(2004) 685, 833].     

Controlled Quantum Teleportation of a One-Particle Unknown State via a Three-Particle Entangled State

A kind of three-particle entangled state is applied as quantum channel of the controlled quantum teleporration of a one-particle unknown state. The one-particle unknown state is transmitted from the sender to the recipient under the control of the supervisor. After the sender makes Bell-state measurement and the supervisor performs von Neumann measurement, the recipient carries out unitary transformation on his own particle depending on classical information from the sender and the supervisor. The teleportation cannot be completed successfully by the recipient if the supervisor does not agree to cooperate. The roles of the recipient and the supervisor may be exchanged in this scheme. The scheme is flexible and feasible because the sequence of manipulation of the sender and the supervisor may be exchanged and only simple unitary transformation is included.