高速连续变量量子密钥分发系统同步技术研究

在高速连续变量量子密钥分发系统中,位帧同步技术是确保准确获取量子信号所携带有效信息的核心技术之一。结合平衡零差探测器测量相干态的正则分量数据,提出了一种简单高效的位帧同步理论方案。基于此理论方案,在重复频率为25MHz的高斯调制相干态连续变量量子密钥分发系统上进行了实验测试和性能分析。结果表明,所提出的位帧同步方案能有效克服量子信号在密钥分发中受到的环境因素影响,有效实现通信双方同步。     

超强激光等离子体相互作用中产生的三次谐波

在不作稀薄等离子体和弱相对论近似的情况下,详细研究了超强激光(10~(18)W/cm~2)和等离子体相互作用过程中静电势及三次谐波发射对等离子体参数和激光参数的依赖关系,从而给出了三次相干谐波产生所需的最佳激光参数和等离子体参数.     

Quantum Distributed Ballot Scheme Based on Greenberger-Horne-Zeilinger State

Motivated by the complementary relations of the Greenberger-Horne-Zeilinger （GHZ） entangled tripletparticle states, a novel way of realizing quantum distributed ballot scheme is proposed. The ballot information is encoded by local operations performed on the particles of entangled GHZ triplet states, which ensures the security of the present scheme. In order to guarantee the security of this scheme, the checking phase is designed in detail on the basis of the entangled GHZ triplet state. The analysis shows the security of the proposed scheme.     

Quantum Homodyne Detection Based on Polarization Diversity Technique

A polarization diversity receiver scheme is presented for improving efficiency of balance homodyne detection. The proposed scheme may mitigate polarization fluctuation between signal and local oscillator field. With simple linear optical component and electronic processing circuit, the noise caused by differential phase and polarization mode between signed and local oscillators may be significantly decreased. To track the polarization fluctuation, a novel algorithm based on polarization diversity receiver which can achieve better performance in terms of linear quantum optics principle is proposed.     

基于量子图态的量子秘密共享

本文基于量子图态的几何结构特征,利用生成矩阵分割法,提出了一种量子秘密共享方案.利用量子图态基本物理性质中的稳定子实现信息转移的模式、秘密信息的可扩展性以及新型的组恢复协议,为安全的秘密共享协议提供了多重保障.更重要的是,方案针对生成矩阵的循环周期问题和因某些元素不存在本原元而不能构造生成矩阵的问题提出了有效的解决方案.在该方案中,利用经典信息与量子信息的对应关系提取经典信息,分发者根据矩阵分割理论获得子秘密集,然后将子秘密通过酉操作编码到量子图态中,并分发给参与者,最后依据该文提出的组恢复协议及图态相关理论得到秘密信息.理论分析表明,该方案具有较好的安全性及信息的可扩展性,适用于量子网络通信中的秘密共享,保护秘密数据并防止泄露.     

Balancing four-state continuous-variable quantum key distribution with linear optics cloning machine

We show that the secret key generation rate can be balanced with the maximum secure distance of four-state continuous-variable quantum key distribution(CV-QKD) by using the linear optics cloning machine(LOCM). Benefiting from the LOCM operation, the LOCM-tuned noise can be employed by the reference partner of reconciliation to achieve higher secret key generation rates over a long distance. Simulation results show that the LOCM operation can flexibly regulate the secret key generation rate and the maximum secure distance and improve the performance of four-state CV-QKD protocol by dynamically tuning parameters in an appropriate range.     

Security analysis of continuous-variable quantum key distribution scheme

In this paper security of the quantum key distribution scheme using correlations of continuous variable Einstein--Podolsky--Rosen (EPR) pairs is investigated. A new approach for calculating the secret information rate Δ I is proposed by using the Shannon information theory. Employing an available parameter F which is associated with the entanglement of the EPR pairs, one can detect easily the eavesdropping. Results show that the proposed scheme is secure against individual beam splitter attack strategy with a proper squeeze parameter.     

Deterministic quantum key distribution based on Gaussian-modulated EPR correlations

This paper proposes a deterministic quantum key distribution scheme based on Gaussian-modulated continuous variable EPR correlations. This scheme can implement fast and efficient key distribution. The security is guaranteed by continuous variable EPR entanglement correlations produced by nondegenerate optical parametric amplifier. For general beam splitter eavesdropping strategy, the secret information rate $\Delta I=I(\alpha,\beta)-I(\alpha,\epsilon)$ is calculated in view of Shannon information theory. Finally the security analysis is presented.     

欠稠密等离子体中诱发的偶次相对论谐波

在自生磁场或背景磁场的作用下,等离子体被磁化.磁化后的欠稠密等离子在超强激光的辐射下诱发相对论相干谐波辐射.由于磁场的影响,诱发的相对论相干谐波辐射中产生偶次谐波辐射.从理论上研究了这一现象,导出了谐波辐射的一般性方程,并特别研究了二次谐波辐射的有关参数 关键词： 二次谐波辐射 自生磁场 强激光 欠稠密等离子体     

Continuous-variable quantum key distribution based on continuous random basis choice

Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and security, we present a scheme based on a continuous random basis choice. The results show that our scheme obviously improves the performance, such as the secure communication distance. Our scheme avoids comparing the measurement basis and discarding the key bits, and it can be easily implemented with current technology. Moreover, the imperfection of the basis choice can be well removed by the known phase compensation algorithm.