基于纠缠相干态的量子照明雷达

量子照明雷达旨在利用量子光场探测热噪声环境下低反射率目标是否存在.发射光源的纠缠特性使其较经典雷达具有独到的探测优势.纠缠相干态(entangled coherent state,ECS)作为一类在噪声环境下纠缠鲁棒性较强的量子态,近年来在量子科学的多个领域得到广泛的应用.本文研究了基于三类不同ECS态的量子照明雷达的...     

基于量子照明的导航测距方案

针对以往脉冲纠缠测距方案对光子损耗十分敏感的特点及量子干涉法测距中利用光路延迟测距时难以实现远距离传输的问题,利用量子压缩效应来提升时延估计精度,同时还提出一种基于量子照明原理的非经典纠缠导航测距方案,对目标存在的回波信号进行统计判断,从而确定距离参数。在相干探测的基础上,分别研究了相干态、热态和压缩态等3种高斯量子态的统计特性,并对量子照明测距方案中经典相干态与双模压缩真空态的信号检测性能进行了理论分析和数值模拟实验。结果表明,相较于传统测距方法,利用量子信号压缩和纠缠特性的方法能有效提高导航测距的距离分辨率,性能上优于经典方案,且在噪声光子数较多时具有更强的抗环境干扰能力。     

单光子纠缠态的纠缠转移和量子隐形传态

使用光学分束器和单光子源,利用单光子态和真空态制备出了纠缠单光子态.利用光学分束器作用和单光子探测,实现了三个通讯伙伴之间的纠缠转移.提出了一个关于纠缠单光子态的量子隐形传态方案.在这个方案中,被传送的是一个未知的单光子纠缠态.通讯双方使用的量子信道是两个单光子纠缠态.通过使用分束器作用和对输出态进行光子测量以及在经典信息的帮助下,纠缠转移和量子隐形传态的过程被完成.     

连续变量量子纠缠态的非对称量子克隆

该文讨论了连续变量量子纠缠态非对称克隆过程,从理论上讨论了在Local e-cloner方案中,入射和出射分束器的反射率可变情况下的纠缠态克隆,并利用纠缠不可分判据分析了所获得的非对称克隆纠缠态的纠缠特性.结果指出,克隆得到的两组纠缠态的纠缠特性不相同.     

纠缠态量子探测系统的恒虚警检测方法研究

纠缠态量子探测是将量子力学与信息科学相结合,应用在目标探测领域的一种新技术,其在灵敏度、抗干扰能力等方面具有突破传统探测技术的潜力.在雷达探测领域,恒虚警检测是一项具有重要的意义和应用价值的技术.然而,对于纠缠态量子探测系统中恒虚警检测方法的研究还没有展开,本文针对这一问题,提出了一种纠缠态量子探测系统的恒虚警检测方法.该方法通过系统对噪声的实时估计,自适应调整检测门限,使得纠缠态量子探测系统在检测过程中始终保持恒定的虚警概率.仿真结果表明,所提恒虚警检测方法是正确和有效的,能够实现纠缠态量子探测系统的恒虚警检测功能.该方法提升了纠缠态量子探测系统的灵活性和适应性,为量子探测技术进一步走向实用及应用奠定了理论基础.     

纠缠相干态的量子隐形传态

提出利用双模纠缠相干态作为量子信道，实现纠缠相干态量子隐形传态的方案. 分别在非正交的相干态表象和另一个由相干态构成的正交态表象对双模纠缠相干态的隐形传态进行具体分析. 发现在相干态表象，虽然只要线性光学元件就可以完成隐形传态，但成功的概率小于1/2，而在正交态表象，只要能分辨4个由相干态构成的Bell态，成功的概率就是1. 关键词： 隐形传态 纠缠相干态 纠缠相干态量子信道     

基于双模压缩信道的双模高斯态量子隐形传态

研究了双模高斯态的两个模经由两个双模压缩量子信道的隐形传态.结果表明，当输入态有纠缠时，若要输出态的纠缠不为零，量子信道的纠缠必须大于一确定值，其大小在输入态为纯态时依赖于输入态的纠缠度；在输入态为混合态时不仅与输入态的纠缠有关，还依赖于输入态的整体纯度. 关键词： 量子隐形传态 量子纠缠 双模高斯态     

量子信息中纠缠态所处的角色

简要给出了量子纠缠态的概念,评述了纠缠态在量子信息论中所处的角色,尤其说明了怎样用它来实现安全的通信。     

利用Bell态实现量子隐形传态

量子隐形传态利用了量子的纠缠特性,在物理层实现了不可破译的量子密码通信.文章从信息论的角度描述了量子纠缠态的特性,给出了实现量子纠缠态的物理门线路;利用该量子纠缠态的量子线路,分析隐形传态的通信模型,给出了利用Bell态实现隐形传态的简单结构的量子线路,证明该量子线路是可行的,为进一步研究量子密码通信提供参考.     

量子纯态的纠缠度

纠缠态在量子计算和量子通讯中起着重要作用.考虑了量子纯态在时间反演变换下的行为以及相应的密度矩阵在Hilbert-Schmidt空间中的表示,并由此对纠缠度给出较为直观的几何解释. 关键词：     

Cluster State Entanglement of Semiconductor Quantum Dots Based on Faraday Rotation

We propose a scheme for a large-scale cluster state preparation of single-charged semiconductor quantum dots utilizing Faraday rotation. Without interaction between quantum dots, the exciton induced Faraday rotation could distribute the spatially separate quantum dots into a quantum network assisted by cavity QED. We obtain the corresponding parameters from the numerical simulation based on the input-output process for the required Faraday rotation and some discussion is made in view of experimental feasibility.     

Quantum Superdense Coding Based on Coherent States in Cavity QED

A physical scheme for the implementation of quantum superdense coding has been proposed in Cavity QED. The detuned interaction between Λ-type three-level atoms and coherent fields constitute the main superdense coding process. The quantum superdense coding can be realized in an easier way, and the atoms are not excited during the whole process, so the effect of atomic decay is eliminated naturally.     

Unknowability of Quantum State forbids perfectly quantum operations

We analyze the connection between quantum operations and accessible information. And we find that the accessible information decreases under quantum operations. We show that it is impossible to perfectly manipulate an unknown state in an open quantum system. That the accessible information decreases under quantum operations gives a fundamental limitation in the microscopic world.     

基于(2m+1)粒子纠缠态的任意m粒子态量子可控离物传态(英文)

提出了一个基于高维2m+1粒子纠缠态的任意m粒子态量子可控离物传态方案,发送方Alice对需传送的未知态量子系统和手中的纠缠粒子执行m个广义Bell基测量,控制方执行广义X基测量,依据预先共享量子纠缠态非定域相关性,接收方对手中的粒子执行相应的幺正操作就可以重建原来未知量子态.与其他方案相比,方案减少了任意高维多粒子态可控离物传送所需传送粒子数.我们进一步讨论了基于纯纠缠信道的概率量子可控离物传态方案,通过与发送方和控制方合作,接收方只需对手中的纠缠粒子和引入的附加粒子执行联合幺正演化和投影测量,就可以在他的粒子上概率的重建原来的未知量子态,最后,方案计算讨论了基于纯纠缠态量子可控离物传态成功概率与信道纠缠度之间的关系.     

基于W态的跨中心量子网络身份认证方案

利用量子隐形传态原理和量子纠缠交换技术,提出了基于W态的跨中心量子网络身份认证方案,实现了分布式量子通信网络中对客户的身份认证.该方案分为注册阶段和身份认证阶段,认证系统包括主服务器和客户端服务器.客户所有的操作都在客户端服务器上进行,不直接与主服务器进行通信.身份认证全部由服务器根据量子力学原理进行,保证了认证方案的安全性.最后,对该方案进行了安全性分析.     

Quantum information capsule in multiple-qudit systems and continuous-variable systems

Quantum correlations in an entangled many-body system are capable of storing information. Even when the information is injected by a local unitary operation to the system, the entanglement delocalizes it. In a recent study on multiple-qubit systems, it is shown that a virtual qubit defined in the correlation space plays a role of perfect storage of delocalized information, which is called a quantum information capsule (QIC). To enhance the capacity of quantum information storage, it is crucial to formulate the cases for multiple-qudit systems and continuous-variable (CV) systems. We analytically prove that it is possible to construct a QIC for general write operations of the systems. It turns out that the extension to quantum field theory is achievable. For Gaussian states, we explicitly construct a QIC for shift write operations. We analyze the time-evolution of QIC in a CV system to demonstrate the diffusion of information in entangled pure states.     

Entanglement Preserving in Quantum Copying of Three-Qubit Entangled State

We study the degree to which quantum entanglement survives when a three-qubit entangled state iscopied by using local and non-local processes, respectively, and investigate iterating quantum copyingfor the three-qubitsystem. There may exist inter-three-qubit entanglement and inter-two-qubit entanglement for the three-qubit system.We show that both local and non-local copying processes degrade quantum entanglement in the three-particle systemdue to a residual correlation between the copied output and the copying machine. We also show that the inter-two-qubitentanglement is preserved better than the inter-three-qubit entanglement in the local cloning process. We find thatnon-local cloning is much more efficient than the local copying for broadcasting entanglement, and output state vianon-local cloning exhibits the fidelity better than local cloning.     

Quantum information capsule and information delocalization by entanglement in multiple-qubit systems

Where do entangled multiple-qubit systems store information? For information injected into a qubit, this question is nontrivial and interesting since the entanglement delocalizes the information. So far, a common picture is that of a qubit and its purification partner sharing the information quantum mechanically. Here, we introduce a new picture of a single qubit in the correlation space, referred to as quantum information capsule (QIC), confining the information perfectly. This picture is applicable for the entangled multiple-qubit system in an arbitrary state. Unlike the partner picture, in the QIC picture, by swapping the single-body state, leaving other subsystems untouched, the whole information can be retrieved out of the system. After the swapping process, no information remains in the system.     

自动对靶喷雾靶标红外探测研究

农林作物一般非连续种植,喷在农林作物靶标之间的药液造成巨大浪费和严重环境污染,因此探讨利用红外线探测技术实现靶标的自动探测, 对靶精准喷施意义重大。红外线可有效防止可见光的干扰,响应速度快,可实现无接触探测,由此建立的红外光电探测系统可靠性好、成本低。红外发光管发射出红外光照射到被探测物体上,反射的红外线被光电探测器接收,触发控制信号,实现自动对靶施药。系统中不同探测器组采用不同编码的调制脉冲红外信号,可消除组间光路干扰及其他光信号的干扰。实验结果表明所建立的红外靶标自动探测装置可对农林作物靶标进行自动探测,光波波长为850 nm,探测距离为0.1～6 m可调,靶标最小识别间距小于0.3 m。