Author Affiliations
Abstract
1 Institute of Modern Physics and Department of Physics, Hunan University of Science and Technology, Xiangtan 411201, China
2 Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Department of Physics, Hunan Normal University, Changsha 410081, China
We propose a feasible scheme of generating multipartite entanglement with the dipole induced transparency (DIT) effect in indirectly coupled dipole-microcavity systems. It is shown that the transmission spectrum is closely related with the interference of dipole-microcavity systems, and we can generate different classes of multipartite entanglement, e.g., the Greenberger–Horne–Zeilinger state, the W state, and the Dicke state, of the dipole emitters just by choosing an appropriate frequency of the incident photon. Benefiting from the DIT effect, the schemes may work in the bad or low-Q cavity regime only if the large Purcell factor of the dipole-microcavity system is fulfilled, and they are also insensitive to experimental noise, which may be feasible with present accessible technology.
270.5580 Quantum electrodynamics Chinese Optics Letters
2018, 16(8): 082702
Author Affiliations
Abstract
1 School of Physics and Electronic Science, Hunan University of Science and Technology, Xiangtan 411201, China
2 Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000, China
An optomechanical cavity embedded with a V-type three-level atom is exploited to control single-photon transport in a one-dimensional waveguide. The effects of the atom–cavity detuning, the optomechanical effect, the coupling strengths between the cavity and the atom or the waveguide, and the atomic dissipation on the single-photon transport properties are analyzed systematically. Interestingly, the single-photon transmission spectra show multiple double electromagnetically induced transparency. Moreover, the double electromagnetically induced transparency can be switched to a single one by tuning the atom–cavity detuning.
270.1670 Coherent optical effects 270.5580 Quantum electrodynamics 020.5580 Quantum electrodynamics Chinese Optics Letters
2018, 16(1): 012701
湖南科技大学 物理与电子科学学院, 湖南 湘潭 411201
考虑初始处于两类Bell态的两原子比特, 将其中一个注入真空态腔中发生共振相互作用的情况, 研究基于操作腔外原子比特控制腔内原子比特相干性时间演化.考察对腔外原子比特施Hadamard(H)门, H类门,Y门及位相门四种逻辑门操作及态选择测量前后, 腔内原子比特约化密度矩阵非对角元时间演化曲线, 讨论两类Bell态之间的关联性. 结果表明, 对腔外原子比特操作前, 腔内原子比特密度矩阵非对角元在任意时刻都为零, 总是处于混合态或经典态, 因此始终退相干.而对腔外原子比特施H门和H类门操作及基态测量后, 腔内原子比特密度矩阵非对角元呈现周期为2π的时间演化, 除(2n+1)π/2时刻外, 其相干性得到恢复；在nπ时刻, 其最大相干叠加态和一般相干叠加态被制备；两类Bell态之间存在R∧(π/2)旋转关联性.而对腔外原子比特施Y门及位相门操作后, 腔内原子比特的相干性得不到恢复.发现腔内原子比特的相干性得到恢复的必要条件是, 逻辑门操作能够调节腔内原子比特与环境的相互作用, 并使两原子比特与场分离的同时, 它们之间形成强相干性的纠缠态分布.
逻辑操作 基态测量 原子比特 密度矩阵 相干性 量子计算 纠缠态分布 Logic gate operation Ground state measurement Atom bit Density matrix Coherence Quantum computation Entanglement state distribution
本文将Tavis-Cummings(T-C)模型推广到同时考虑原子运动及与光场依赖强度耦合的情况 .运用全量子理论，研究了与光场依赖强度耦合下运动纠缠双原子量子态保真度演化.采用数值计算的方法，探讨了双原子初始纠缠因子、光场平均光子数n－以及场模结构参量p对双原子量子态保真度演化的影响，解析分析了双原子周期量子回声的形成规律，揭示了其物理实质.结果表明， 在场模结构参量p=1的情况下，无论光强和双原子初始纠缠因子如何取值，双原子均产生周期2π的量子回声；在强相干场n－=30条件下，改变p从1到小于800时，Bell态双原子产生2π/p周期量子回声.当p≥800时，无论光场是真空场、弱相干场或强相干场，双原子量子态保真度恒为1，即第一类Bell态原子持续处于保真态；而当双原子初始纠缠因子为3π/4时，无论n－、p取何值，双原子量子态保真度保持为1，双原子持续处于第二类Bell态的保真态.其结论表明, 该推广模型具有很好的双原子周期量子回声性质，为纠缠双原子信息高保真输出及噪音环境下量子信息处理的实验实现提供了理论参量和物理载体.
依赖强度耦合 运动纠缠双原子 量子态保真度 周期量子回声 Intensity-dependent coupling Moving and entangled two-atom Fidelity of quantum states Periodic quantum echo
旋波近似条件下，运用全量子理论研究了与双模相干光场依赖强度耦合多光子通道中原子比特周期量子回声的产生和控制. 采用数值计算的方法，讨论了双模相干光场平均光子数分布形式、分布范围及原子跃迁时吸收（或发射）的光子数k对原子比特态保真度演化的影响，获得了产生和控制原子比特周期量子回声的系统参量；根据纠缠理论，分析了原子比特态保真度演化与原子约化熵演化的关联. 结果表明：在k=1的双光子过程中，调控光场平均光子数呈对称或不对称分布，当它的取值在一定范围内，原子比特保持良好的相干性和保真度，产生周期量子回声; 对于k≥2的多光子过程，原子比特与双模相干光场始终处于最大纠缠，因此导致了原子比特始终处于部分失真状态，不产生周期量子回声. 本研究揭示了周期量子回声产生的物理实质是原子比特与光场周期性退纠缠.
依赖强度耦合 多光子通道 原子比特 保真度 周期量子回声 Intensity-dependent coupling Multiphoton channel Atom bit Fidelity Periodic quantum echo
