相干态统计特性的弱测量结构研究

理论分析相干态位移参数估计在弱测量方法下的放大效应.引入偏振态作为附属态(Ancilla States),分别进行初选择和后选择,中间的相互作用采用了偏振相关的弱位移操作算符.通过最后检测光子数的分布来估计位移参数;在牺牲检测光子强度的情况下可以有效提高放大效应.     

A realizable quantum encryption algorithm for qubits

A realizable quantum encryption algorithm for qubits is presented by employing bit-wise quantum computation. System extension and bit-swapping are introduced into the encryption process, which makes the ciphertext space expanded greatly. The security of the proposed algorithm is analysed in detail and the schematic physical implementation is also provided. It is shown that the algorithm, which can prevent quantum attack strategy as well as classical attack strategy, is effective to protect qubits. Finally, we extend our algorithm to encrypt classical binary bits and quantum entanglements.     

等离子体通道中的自生磁场

研究了超短脉冲强激光在等离子体通道中传播时产生的自生磁场．利用相对论动量方程和泊松方程及安培定律得出自生磁场的一个基本公式，在此基础上解析并数值研究了通道中产生的自生磁场的特性和结构，初步探讨了超短脉冲强激光在等离子体中传播时形成的排空效应对自生磁场的影响，并分析了产生自生磁场的机制 关键词：     

中空等离子体通道中强激光脉冲对电子的加速

分析了中空等离子体通道内传播的强激光脉冲电磁场中注入电子的运动,发现当激光脉冲强度超过某个阈值时,电子能获得有效的纵向加速并自动与脉冲分离.所得结果为实验提供了参考和依据.     

LDPC码在量子密钥分配多维协商算法中的应用

密钥协商是量子密钥分配(QKD)的重要环节,影响着QKD的密钥率和安全距离.作为一种低信噪比时较为高效的密钥协商方案,多维协商算法被很好地应用在高斯调制连续变量QKD中,延长了通信距离.本文研究了二进制LDPC码在多维协商算法中的应用方案,进而扩展到多进制LDPC码.仿真表明,相比二进制LDPC码,利用多进制LDPC码能够使多维协商性能获得明显增益.     

量子密钥分发中Cascade协议的一种改进方案

密钥协商是量子密钥分发(QKD)中的重要组成部分.Cascade协议是实际中使用最广泛的量子密钥协商协议.本文基于[6]的工作提出一种对Cascade协议的改进方案.计算机仿真显示我们的方案比原始Cascade和一些其它改进方案有更高的效率.     

Weak value amplification via second-order correlated technique

We propose a new framework combining weak measurement and second-order correlated technique.The theoretical analysis shows that weak value amplification(WVA) experiment can also be implemented by a second-order correlated system.We then build two-dimensional second-order correlated function patterns for achieving higher amplification factor and discuss the signal-to-noise ratio influence.Several advantages can be obtained by our proposal.For instance,detectors with high resolution are not necessary.Moreover,detectors with low saturation intensity are available in WVA setup.Finally,type-one technical noise can be effectively suppressed.     

A （2, 3） quantum threshold scheme based on Greenberger-Horne-Zeilinger state

In this paper, by using properties of quantum controlled-not manipulation and entanglement states, we have designed a novel (2, 3) quantum threshold scheme based on the Greenberger- Horne -Zeilinger (GHZ) state. The proposed scheme involves two phases, i.e. a secret sharing phase and a secret phase. Detailed proofs show that the proposed scheme is of unconditional security. Since the secret is shared among three participants, the proposed scheme may be applied to quantum key distribution and secret sharing.     

The dependence of fidelity on the squeezing parameter in teleportation of the squeezed coherent states

This paper investigates an analytical expression of teleportation fidelity in the teleportation scheme of a single mode of electromagnetic field.The fidelity between the original squeezed coherent state and the teleported one is expressed in terms of the squeezing parameter r and the quantum channel parameter(two-mode squeezed state) p.The results of analysis show that the fidelity increases with the increase of the quantum channel parameter p,while the fidelity decreases with the increase of the squeezing parameter r of the squeezed state.Thus the coherent state(r = 0) is the best quantum signal for continuous variable quantum teleportation once the quantum channel is built.