Markov环境下“X”态基于CHSH不等式的量子非局域关联检验

量子非局域关联是量子理论最基础的特征之一.“X”态作为实验中常见的一种量子态,因其在演化过程中仍保持“X”形的稳定性,而被广泛应用于开放量子系统的研究中.利用Clauser-Horne-Shimony-Holt (CHSH)不等式,在Markov环境这种典型的开放量子系统下,研究了两种通过局部变换操作所关联的“X”态在振幅阻尼环境和相位阻尼环境中量子非局域检验结果随时间的演化情况.研究结果表明,在相位阻尼环境中,随着演化时间的增加,两种“X”态具有相同的CHSH不等式检验结果.在振幅阻尼环境中,利用局部变换操作得到的“X”态,可获得较长的成功进行量子非局域关联检验的演化时间.最后,详细给出了两种类型“X”态在相位阻尼环境和振幅阻尼环境中成功进行量子非局域关联检验的保真度范围.

基于CHSH不等式几何解释的“X”态量子非局域关联检验

量子非局域关联现象是量子理论区别于经典理论的重要特征之一.“X”态作为一种典型的量子混合态,基于其进行的量子非局域关联的检验研究,不论对验证量子理论的正确性,还是在量子信息论的应用领域研究,都具有重要的意义.本文在基于传统Clauser-Horne-Shimony-Holt(CHSH)不等式进行量子非局域关联检验的基础上,提出了一种基于“X”态几何解释的量子非局域关联检验策略.利用“X”态的几何解释策略,可使物理图像更为直观地研究检验时最优化测量基选取,以及可获得的最大CHSH不等式检验值等.最后给出了基于CHSH不等式几何解释策略,“X”态成功进行量子非局域关联检验的参数范围.

量子纠缠和量子操作对CHSH量子博弈优越性的影响

已有的大多数有关量子博弈的研究只关注粒子处在最大纠缠态和特定的量子操作时模型的优越性.在实际应用中,所用粒子可能偏离最大纠缠态,量子操作也可能存在一定的偏差。基于此,研究了这两方面对CHSH量子博弈模型优越性的影响。结果表明,当粒子处在特定纠缠态时,量子获胜概率P并不总是大于经典获胜概率P_c,采用不同的量子旋转门操作可以达到的最大量子获胜概率P_(max)随着量子态纠缠度的增大而增大。在P_(max)对应的量子门旋转角附近,某些旋转角范围对应的P变化较小。这些研究对量子博弈的应用提供了理论指导。

What in Fact Proves the Violation of the Bell-Type Inequalities?

A. Peres constructed an example of particles entangled in the state of spin singlet. He claimed to have obtained the CHSH inequality and concluded that the violation of this inequality shows that in a measurement in which some variables are tested, other variables, not tested, have no defined value. In the present paper is proved that the correct conclusion of the violation of the CHSH inequality is different. It is proved that the classical calculus of probabilities of test results, obeying the Kolmogorov axioms, is unfit for the quantum formalism, dominated by probability amplitudes.

双光子纠缠体系中的非定域性和稳健性

利用非线性晶体的Ⅱ型参量下转换和极化后选择方法,制备了高品质的极化双光子纠缠态。在双光子纠缠系统中实验测量了Clauser-Horne-Shimony-Holt(CHSH)和Cavalcanti-Bell(C-B)不等式对定域实在论的违背,得到CHSH、C-B不等式的值分别为2.64±0.021、2.75±0.019.利用线性光学器件模拟了量子信道中的比特翻转噪声,实验研究了CHSH型不等式在比特翻转噪声环境下的稳健性,结果表明在比特翻转噪声环境中C-B比CHSH不等式对噪声具有更强的稳健性,为进一步研究纠缠在量子信息处理中的应用提供了实验支持.

用光子纠缠源验证Bell不等式

以Bell不等式的推广形式CHSH不等式为理论指导,利用自主搭建的双光子纠缠源制备光子纠缠态,通过测量不同条件下符合对比度计算Bell不等式,验证了量子力学的完备性.

Ⅰ类量子纠缠实验教学系统

为使量子纠缠实验更好地服务于本科生基础实验教学,自建了I类纠缠源实验教学系统.采用2块光轴相互垂直的薄片BBO晶体粘合,并调整泵浦光偏振与光轴成45°入射,在粘合面附近位置产生的下转换光锥交叠部分将形成量子纠缠.由于I类源产生的光子对偏振相同,从而避免建立补偿系统,降低了纠缠点空间定位的精度要求和操作难度,简化接收装置,同时保持原实验中的核心原理和操作训练要求,本科生在1~2次实验课中达到教学设定要求.

非完美探测效率对设备无关量子随机数扩展的影响

设备无关(Device Independent,简记为DI)量子随机数扩展方案中,在不需要考虑系统内部工作状态前提下,基于纠缠粒子的非局域特性可以证明随机性的存在.但在实际条件下的可行性受到探测效率等因素的限制.本文在CHSH不等式中引入探测效率参数,从两方面探究非完美探测效率对DI随机数扩展方案的影响,数值模拟出将未探测事件作为结果保留和随机赋值时非完美探测效率下小熵与CHSH违背值的定量关系.将未探测事件作为结果保留时,可得在相同CHSH值下较低的探测效率对应的实验中量子态和测量过程蕴含更多的随机性,而在相同的的实验环境下,探测效率的降低会使实验中输出序列小熵变小.将未探测事件随机赋值时,在相同的CHSH违背值下,伴随着探测效率的降低,小熵界逐渐变小.通过SDP优化算法可得此情形下进行DI随机数扩展的探测效率下界为91.1%.通过对非完美探测效率的量化分析,可得实际条件下更为准确的DI量子随机数扩展效率分析.

二量子比特混合态隐形传输保真度研究

针对二量子比特混合态系统,利用描述态的密度矩阵研究了CHSH违反、混合度与隐形传输保真度的关系。通过共生纠缠度确定了隐形传输保真度的上、下限。结果表明,二量子比特混合态在CHSH违反最大位置或混合度最小位置获得最大隐形传输保真度,并可以通过增加共生纠缠度来提高隐形传输保真度。

光腔中两量子比特的量子关联动力学

文章研究了两个与同一个单模光腔耦合的二能级原子之间量子关联动力学问题.用幺正时间演化算符推出随时间演化的态密度算符.接着,我们数值模拟量子CHSH关联的时间演化并且与纠缠度的时间演化做了比较.据观察,初始态的角度参数对量子CHSH关联与纠缠度的时间演化影响极大.值得注意的是,量子CHSH关联与纠缠度的时间演化可以呈周期性.

Simple Mitigation Strategy for a Systematic Gate Error in IBMQ

In this paper, we report the observation and characterisation of a systematic error in the implementation of U3 gates in the IBM quantum computers. By measuring the effect of this gate for various rotation angles the error appears as an over-rotation, whose magnitude does not correlate with IBM’s cited errors calculated using Clifford randomized benchmarking. We propose a simple mitigation procedure to limit the effects of this error. We show that using a simple mitigation strategy one can obtain improved results in the observed value for the CHSH inequality, measured in a cloud-based quantum computer. This work highlights the utility of simple mitigation strategies for short-depth quantum circuits.

Quantum Violation of Bell’s Inequality: A Misunderstanding Based on a Mathematical Error of Neglect

This paper intends to show how the fabled violation of Bell’s inequality by the probabilistic specifications of quantum mechanics derives from a mathematical error, an error of neglect. I have no objection to the probabilities specified by quantum theory, nor to the inequality itself as characterized in the formulation of Clauser, Horne, Shimony, and Holt. Designed to assess consequences of Einstein’s principle of local realism, the inequality pertains to a linear combination of four polarization products on the same pair of photons arising in a gedankenexperiment. My assessment displays that in this context, the summands of the relevant CHSH quantity s(λ) inhere four symmetric functional relations which have long been neglected in analytic considerations. Its expectation E[s(λ)] is not the sum of four “marginal” expectations from a joint distribution, as quantum theory explicitly avoids such a specification. Rather, I show that E[s(λ)] has four distinct representations as the sum of three expectations of polarization products plus the expectation of a fourth which is restricted to equal a function value determined by the other three. Analysis using Bruno de Finetti’s fundamental theorem of prevision (FTP) yields only a bound for E(s) within (1.1213,2] , surely not at all as is commonly understood. I exhibit slices of the 4-dimensional polytope of joint P++ probabilities actually motivated by quantum theory at the four stipulated angle settings, as it passes through 3-dimensional space. Bell’s inequality is satisfied everywhere within the convex hull of extreme distributions cohering with quantum theoretic specifications, even while in keeping with local realism. Aspect’s proposed “estimation” of E(s) near to is based on polarization products from different photon pairs that do not have embedded within them the functional relations inhering in the relevant gedankenexperiment. When one actively embeds the restrictions into Aspect’s estimation procedure, it yields an estimate of 1.7667, although this is not and cannot be definitive. While my analysis supports the subjectivist construction of probability as clarifying issues relevant to the interpretation of quantum theory, the error resolved herein is purely mathematical. It pertains to the reconsideration of Bell violation irrespective of one’s attitude toward the meaning of probability.

基于局域操作下的两量子比特混态纠缠蒸馏实验研究

最大纠缠态在量子信息传输和处理过程中是最重要的资源之一,因此从退化的纠缠态中提炼出最大纠缠态一直是量子信息基础研究中的一个重要课题.根据VerstraeteF等人在Phys.Rev.A,2001,64:010101(R)上提出的有效的方法,文章作者在实验上证明了基于局域操作下的两种形式的两量子比特混态纠缠蒸馏最佳协议.从原则上讲,文章的实验也可以容易地应用于任意两量子比特部分混合态的纠缠蒸馏.此外,作者还对经过蒸馏的第一类混合量子态进行Clauser-Horne-Shimmony-Holt(CHSH)不等式的检测,以验证它的“隐藏非局域性”.

柴胡四黄汤对重症急性胰腺炎血清TNF-α,IL-6,IL-10水平的影响

目的:探讨柴胡四黄汤对重症急性胰腺炎(SAP)血清细胞因子水平的影响。方法:60例SAP病患者随机分为治疗组和对照组(各30例)。治疗组给予柴胡四黄汤口服,1剂/d;对照组30例,给予大柴胡汤口服,1次/d,疗程均为7 d。测定两组患者治疗前后肿瘤坏死因子α(TNF-α)、白细胞介素6(IL-6)和白细胞介素10(IL-10)水平。且设正常健康组30例。结果:2组IL-10水平均较健康组低。而TNF-α及IL-6较健康组高(P<0.01)。治疗后治疗组TNF-,αIL-6水平与对照组比明显降低(P<0.01),IL-10与对照组比明显增高(P<0.01),治疗组与治疗前对比P<0.01。结论:柴胡四黄汤能显著调节细胞因子水平,促进SAP早期恢复。