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1.
A quantum cryptographic protocol based on the use of a strongly correlated pair of laser beams is proposed. The properties of the corresponding states are described in detail. The protocol is based on the strong correlation of photon numbers in both beams in each measurement. The protocol stability against basic interception attempts is analyzed.  相似文献   

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刘艳红  吴量  闫智辉  贾晓军  彭堃墀 《物理学报》2019,68(3):34202-034202
量子纠缠是一种重要的量子资源,在多个空间分离的量子存储器间建立确定性的量子纠缠,然后在用户控制的时刻将所存储的量子纠缠转移到量子信道中进行信息的分发和传送,这对于实现量子信息网络是至关重要的.本文介绍了用光学参量放大器制备与铷原子D1吸收线对应的非经典光场,而且在三个空间分离的原子系综中确定性量子纠缠的产生、存储和转移.利用电磁感应透明光和原子相互作用的原理,将制备的多组分光场纠缠态模式映射到三个远距离的原子系综以建立原子自旋波之间的纠缠.然后,存储在原子系综中的纠缠态通过三个量子通道,纠缠态的量子噪声被转移到三束空间分离的正交纠缠光场.三束释放的光场间纠缠的存在验证了该系统具有保持多组分纠缠的能力.这个方案实现了三个量子节点间的纠缠,并且可以直接扩展到具有更多节点的量子网络,为未来实现大型量子网络通信奠定了基础.  相似文献   

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高能自旋极化正负电子束与偏振伽马射线在高能物理、实验室天体物理与核物理等领域有十分重要的应用.近年来随着超短超强激光脉冲技术的快速发展,利用强激光与物质相互作用的非线性康普顿散射和多光子Breit-Wheeler过程为制备高极化度、高束流密度的高能极化粒子束提供了新的可能.本文对基于强激光产生高能极化正负电子束与偏振伽马射线的研究成果进行简要回顾,并介绍了这些方法的基本物理原理和主要结果.  相似文献   

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单离子阱中基本量子逻辑单元的实现   总被引:2,自引:0,他引:2       下载免费PDF全文
蓝海江  扬庆怡  韦联福 《物理学报》2002,51(8):1730-1735
建议了一种利用单个囚禁冷却离子实现基本量子逻辑门操作(单比特门和两比特受控旋转门)的理论方法,通过数值计算给出了各种相关实验参量的合理设置要求.在这一方案中,量子逻辑门的操作既不要求离子辅助能级的参与,也不限定只在弱耦合的LambDicke区内进行,因而将更容易地为实验所实现 关键词: 量子计算机 受控量子逻辑门操作 LambDicke耦合参数  相似文献   

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马亚云  冯晋霞  万振菊  高英豪  张宽收 《物理学报》2017,66(24):244205-244205
设计研制了连续单频671 nm/1342 nm双波长激光器,并通过模式清洁器降低了激光器额外噪声.利用该低噪声连续单频激光器抽运由Ⅱ类准相位匹配晶体构成的双共振非简并光学参量放大器,实验制备出纠缠度达3 dB的光通信波段1.34μm连续变量量子纠缠态光场.该波段量子纠缠态光场在光纤中传输损耗低且相散效应小,与现有的光纤通信系统相兼容,可用于实现基于光纤的实用化连续变量量子通信.  相似文献   

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A generation system of continuous-variable (CV) quadripartite entangled state based on two cascaded second- harmonic generation (SHG) cavities below the threshold is investigated. Two reflected fundamental bearias of the first cavity, the reflected second-harmonic beam and the output fourth-harmonic beam of the second cavity are proved to be entangled, and the dependence of the entanglement degree on the normalized frequency, pump parameter, fourth-harmonic loss parameter, and second-harmonic loss parameter is also analyzed. Due to the fact that the cavity parameters and the nonlinear crystals of the two SHG cavities can be freely chosen, the practicality of the proposed protocol is relatively perfect and the system can also be extended to the preparation of multicolor entangled states for a quantum network.  相似文献   

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By applying the nonlinear interaction between internal and external degrees of a trapped ion with theassistance of two pairs or three pairs of laser beams that are perpendicular to each other, the realization of quantumlogic operation without the limitation on the Lamb-Dicke parameter can be achieved when the lasers are tuned to thecarrier.  相似文献   

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We find the solutions of the Dirac equation for two plane waves (laser beams) and we determine the modified Compton formula for the scattering of two photons on an electron. The practical meaning of the two laser beams is, that two laser beams impinging on a target which is constituted from material in the form a foam, can replace 100–200 laser beams impinging on a normal target and it means that the nuclear fusion with two laser beams is realistic in combination with the thermonuclear reactor such as ITER.  相似文献   

10.
The dynamical Schwinger effect of vacuum pair creation driven by an intense external laser pulse is studied on the basis of quantum kinetic theory. The numerical solutions of these kinetic equations exhibit a complex time dependence which makes an analysis of the physical processes difficult. In particular, the question of secondary effects, such as creation of secondary annihilation photons from the focus spot of the colliding laser beams, remains an important open problem. In the present work we, therefore, develop a perturbation theory which is able to capture the dominant time dependence of the produced electron‐positron pair density. The theory shows excellent agreement with the exact kinetic results during the laser pulse, but fails to reproduce the residual pair density remaining in the system after termination of the pulse. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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