多方控制的量子安全直接通信协议

基于单光子序列的顺序重排，提出了一种可应用于一些特殊的场景的多方控制的量子安全直接通信协议.协议中，接收方只有在得到所有控制方的同意之后，才能恢复出发送方的秘密消息.协议的安全性由量子不可克隆定理和单光子序列的秘密传输顺序所保证.此外，除了用于窃听检测的部分光子，所有的光子都用于编码秘密消息，而且协议的实现不需要使用纠缠态，该协议具有效率高和实现简单等特点. 关键词： 量子密码 量子安全直接通信 顺序重排 单光子     

基于单光子的单向量子安全通信协议

提出了基于单光子的单向量子安全通信方案.发送方在对信息序列进行编码操作之前首先将其和随机序列进行异或操作并插入校验序列.接收方收到光子后对其进行延迟,此后发送方公布编码基从而使接收方在正确的基下进行测量.接着双方通过校验序列判断信道的安全性,如果信道安全,则发送方公布接收方有测量结果的位置所对应的随机序列,接收方由此恢复出信息序列;如果信道不安全,窃听者所获得的只是随机的发送序列,信息序列仍然是安全的.此协议与双向通信协议相比具有传输效率高、 易于实现等优点. 关键词： 量子密码 量子安全通信 单光子 单向通信     

量子BB84协议在联合旋转噪音信道上的安全性分析

多数在理想条件下设计的量子密码协议没有考虑实际通信中噪音的影响,可能造成机密信息不能被准确传输,或可能存在窃听隐藏在噪音中的风险,因此分析噪音条件下量子密码协议的安全性具有重要的意义.为了分析量子BB84协议在联合旋转噪音信道上的安全性,本文采用粒子偏转模型,对量子信道中的联合噪音进行建模,定量地区分量子信道中噪音和窃听干扰;并且采用冯·诺依曼熵理论建立窃听者能窃取的信息量与量子比特误码率、噪音水平三者之间的函数关系,定量地分析噪音条件下量子信道的安全性;最后根据联合噪音模型及窃听者能窃取的信息量与量子比特误码率、噪音水平三者之间的关系,定量地分析了量子BB84协议在联合噪音条件下的安全性并计算噪音临界点.通过分析可知,在已有噪音水平条件下,窃听者最多能够从通信双方窃取25%的密钥,但是Eve的窃听行为会被检测出来,这样Alice和Bob会放弃当前协商的密钥,重新进行密钥协商,直至确认没有Eve的窃听为止.这个结果说明量子BB84协议在联合旋转噪音信道下的通信是安全的.     

基于BB84协议利用多对量子态实现量子密钥分配

为了改善BB84协议防窃听的能力,在BB84协议的基础上提出用M(M=3,4,5…)对量子态实现量子密钥分配。为了检测其安全性,用截获-重发的方式对量子密钥分配过程进行窃听,窃听者分别采用两种检测光子状态的方法:在M组基中随机选取一种基和用Breidbart基测量,并在这两种窃听方法下分别通过计算机仿真探究M值与安全性能的关系。仿真结果表明:用多对量子态实现量子密钥分配时,发现窃听者的能力与BB84协议相同,而窃听者可以获取的正确信息要比窃听BB84协议获取的正确信息少。从而提高了量子密钥分配的安全性。     

基于Bell态粒子和单光子混合的量子安全直接通信方案

为了提高量子安全直接通信的效率,本文提出了一种基于Bell态粒子和单光子混合的量子安全直接通信方案.该方案中Alice将所有Bell态粒子划分为两个序列S_A和S_B,先将S_B发给Bob进行第一次窃听检测,检测结果表示量子信道安全后再将信息序列编码在序列S_A和单光子序列S_S混合的量子态序列上;然后将已编码序列经过顺序重排和添加单光子检测粒子后发给合法接收方Bob.该方案避免了复杂的U变换,简化了方案的实现过程.同时顺序重排和检测粒子的结合保证了方案的安全性.另外3 bits经典信息加载在一个态上的编码规则大大提高了编码容量,从而使信息传输效率也得到提高.     

可控量子秘密共享协议窃听检测虚警概率分析

对孙莹等提出的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议Alice-Bob信道和Alice-Charlie信道窃听检测的虚警概率进行分析,指出该协议窃听检测虚警概率不为0的原因在于窃听检测测量基选择的随机性.然后,提出一种改进的利用Greenberger-HorneZeilinger态实现的可控量子秘密共享协议,以确定性的方式选择窃听检测的测量基.理论分析表明,改进的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议不仅能够以原协议2倍的概率发现任何一个内部不可信方,从而具有更高的安全性,而且窃听检测虚警概率达到0.     

基于显微物镜的表面等离子体共振

对孙莹等提出的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议Alice-Bob信道和Alice-Charlie信道窃听检测的虚警概率进行分析,指出该协议窃听检测虚警概率不为0的原因在于窃听检测测量基选择的随机性.然后,提出一种改进的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议,以确定性的方式选择窃听检测的测量基.理论分析表明,改进的利用Greenberger-Horne-Zeilinger态实现的可控量子秘密共享协议不仅能够以原协议2倍的概率发现任何一个内部不可信方,从而具有更高的安全性,而且窃听检测虚警概率达到0.     

QKD扩展BB84协议的Breidbart基窃听问题

给出了六态扩展BB84协议的Breidbart基窃听方案,分析并计算了各种截取重发策略下的AliceEve平均交互信息量和施行QKD标准纠错手续后的有效平均交互信息量,结果显示Breidbart基窃听Breidbart基重发策略(BB策略)最为有效.考虑到Alice和Bob可以在公开讨论阶段利用废弃数据检验是否存在BB窃听以降低秘密性增强算法的强度,减少量子密钥的损失,提出了修改BB84协议的建议.给出了可能较QKD标准纠错手续更为安全的量子密钥二次生成纠错方法 关键词： 量子密码 BB84协议 Breidbart基窃听     

复合量子密钥分发系统双速协议及其安全性分析

基于真空光速c是极限信号速度这一基本假设,提出了复合量子密钥分发(QKD)系统和双速协议,并证明双速协议的安全性与原BB84协议的安全性相同.结果表明,双速协议在将量子密钥生成效率从50%提高到100%的同时,还降低了窃听者Eve可能得到的信息量.双速协议由于打破了公开讨论之前Bob和Eve的对等地位,使QKD在概念上有了明显的改进,使协议基的选择空间有了本质性的扩充.具体给出了三个双速协议的实例,并详细分析了它们在截取重发攻击下的安全性 关键词： 量子密码 光纤量子密钥分发 双速协议     

基于腔QED的无信息泄露量子对话(英文)

良好的安全性对量子保密通信协议而言是不可或缺的,但信息泄露已成为量子对话的一个严重安全威胁.为了解决信息泄露问题,利用腔QED中原子的演化规律提出一个基于腔QED的无信息泄露量子对话协议,利用腔QED中两个Bell态纠缠交换后的测量相关性来克服信息泄露问题.研究表明:该协议能够通过安全检测探测到外部窃听者的主动攻击,如截获-重发攻击、测量-重发攻击和纠缠-测量攻击;在每轮通信可以安全交换4比特秘密信息;对信息泄露问题和外部窃听者的主动攻击,都具备良好的安全性.     

Beyond the Limits of Shannon’s Information in Quantum Key Distribution

We present a new post-processing method for Quantum Key Distribution (QKD) that raises cubically the secret key rate in the number of double matching detection events. In Shannon’s communication model, information is prepared at Alice’s side, and it is then intended to pass it over a noisy channel. In our approach, secret bits do not rely in Alice’s transmitted quantum bits but in Bob’s basis measurement choices. Therefore, measured bits are publicly revealed, while bases selections remain secret. Our method implements sifting, reconciliation, and amplification in a unique process, and it just requires a round iteration; no redundancy bits are sent, and there is no limit in the correctable error percentage. Moreover, this method can be implemented as a post-processing software into QKD technologies already in use.     

Error Estimation at the Information Reconciliation Stage of Quantum Key Distribution

Quantum key distribution (QKD) offers a practical solution for secure communication between two distinct parties via a quantum channel and an authentic public channel. In this work, we consider different approaches to the quantum bit error rate (QBER) estimation at the information reconciliation stage of the post-processing procedure. For reconciliation schemes employing low-density parity-check (LDPC) codes, we develop a novel syndrome-based QBER estimation algorithm. The algorithm suggested is suitable for irregular LDPC codes and takes into account punctured and shortened bits. Testing our approach in a real QKD setup, we show that an approach combining the proposed algorithm with conventional QBER estimation techniques allows one to improve the accuracy of the QBER estimation.     

次条纹积分干涉计量

叙述了次条纹积分干涉干时的原理，仅用一幅光载频干涉纹图获取全部位相信息。先用分段积分法求出条纹初始位相，再由最小二乘原理，迭代出信息的位相解。并讨论了条纹位相的算法，误差修正和测量面形的应用。     

ADC border effect and suppression of quantization error in the digital dynamic measurement

The digital measurement and processing is an important direction in the measurement and control field. The quantization error widely existing in the digital processing is always the decisive factor that restricts the development and applications of the digital technology. In this paper, we find that the stability of the digital quantization system is obviously better than the quantization resolution. The application of a border effect in the digital quantization can greatly improve the accuracy of digital processing. Its effective precision has nothing to do with the number of quantization bits, which is only related to the stability of the quantization system. The high precision measurement results obtained in the low level quantization system with high sampling rate have an important application value for the progress in the digital measurement and processing field.     

Experimental Realization of Arbitrary Accuracy Iterative Phase Estimation Algorithms on Ensemble Quantum Computers

We report the first experimental demonstration of a nuclear phase estimation algorithms. Using feedback and iterations, magnetic resonance （NMR） realization of iterative we experimentally obtain the phase with 6 bits of precision on a two-qubit NMR quantum computer. Furthermore, we experimentally demonstrate the effect of gate noise on the iterative phase estimation algorithm. Our experimental results show that errors of measurements of the phase depend strongly on the precision of coupling gates. This experiment can be used as a benchmark for multi-qubit realizations of quantum information processing and precision measurements.     

Checking key integrity efficiently for high-speed quantum key distribution using combinatorial group testing

With the increasing key generation rate in practical quantum key distribution, checking key integrity efficiently becomes an important problem. Since the original method that utilizes one hash value for a key string has to discard all the key bits even if just one error bit exists, it may eventually limit the practical rate of key generation. In this paper, we propose a new scheme based on combinatorial group testing to identify the rare error bits so as to avoid dropping all the key bits. Experimental results show that the scheme can precisely locate the error bits if the number of error bits is within the maximum guaranteed number set by the scheme while the overhead is insignificant (for a 10⁶-bit key, additional bits: 0.1% of the key; hashing time: 16 ms; checking time: 22 ms) and it can still keep the majority of the correct bits (95%) even if the number of error bits is 10 times of the maximum. The results also indicate that the minimum key size for the CGT-based scheme to gain an advantage over the original method is about 2 × 10⁴ bits.     

Reinforcement Learning for Bit-Flipping Decoding of Polar Codes

A traditional successive cancellation (SC) decoding algorithm produces error propagation in the decoding process. In order to improve the SC decoding performance, it is important to solve the error propagation. In this paper, we propose a new algorithm combining reinforcement learning and SC flip (SCF) decoding of polar codes, which is called a Q-learning-assisted SCF (QLSCF) decoding algorithm. The proposed QLSCF decoding algorithm uses reinforcement learning technology to select candidate bits for the SC flipping decoding. We establish a reinforcement learning model for selecting candidate bits, and the agent selects candidate bits to decode the information sequence. In our scheme, the decoding delay caused by the metric ordering can be removed during the decoding process. Simulation results demonstrate that the decoding delay of the proposed algorithm is reduced compared with the SCF decoding algorithm, based on critical set without loss of performance.     

An Enhanced Affine Projection Algorithm Based on the Adjustment of Input-Vector Number

An enhanced affine projection algorithm (APA) is proposed to improve the filter performance in aspects of convergence rate and steady-state estimation error, since the adjustment of the input-vector number can be an effective way to increase the convergence rate and to decrease the steady-state estimation error at the same time. In this proposed algorithm, the input-vector number of APA is adjusted reasonably at every iteration by comparing the averages of the accumulated squared errors. Although the conventional APA has the constraint that the input-vector number should be integer, the proposed APA relaxes that integer-constraint through a pseudo-fractional method. Since the input-vector number can be updated at every iteration more precisely based on the pseudo-fractional method, the filter performance of the proposed APA can be improved. According to our simulation results, it is demonstrated that the proposed APA has a smaller steady-state estimation error compared to the existing APA-type filters in various scenarios.     

不同模糊尺度下运动模糊方向的鉴别

为了有效减弱高动态环境对图像采集的干扰,利用模糊图像的频谱特性,提出了一种适合不同模糊尺度的运动模糊方向估计方法。该方法对比不同模糊尺度图像频谱中心亮条纹边缘特征的差别,通过计算其曲率半径实现不同模糊尺度图像的量化鉴别,在确定图像模糊尺度的大小之后,分别利用倒频谱、二次傅氏变换对模糊图像频谱中心亮线特征进行提取,考虑图像高宽比、中心十字亮线的不利影响,在二值化处理的基础上剔除十字亮线,通过亮线特征点直线拟合完成模糊方向估计。实验结果表明,该算法能够有效鉴别不同模糊尺度的运动模糊方向,估计精度较其他同类算法更高,相对误差率均小于0.02。