玻色约瑟夫森结中的退相干和纠缠：玻色增强的量子芝诺控制相扩散
Decoherence and entanglement in a bosonic Josephson junction: Bose-enhanced quantum-Zeno control of phase-diffusion
摘要：
本文研究了退相干对两格点玻色-哈伯德模型中动力学相扩散的影响。从奇宇称激发相干态开始，单粒子相干的初始损失从拉比制度中的小束缚振荡，通过约瑟夫森制度中的双曲线耗尽，到Fock制度中的高斯衰减。包含本地站点噪声，测量模式之间的相对数差，示出增强相位扩散。相比之下，测量两种准动量模式之间的布居不平衡的不分地点的噪音会减缓单粒子相干性的丧失。因此，退相干增强或抑制相扩散，这取决于系统浴耦合的细节和退相干指针状态与碰撞纠缠指针状态的重叠。由于与环境的耦合而导致的相扩散的减速可以被看作是多体量子芝诺效应。在投影测量的存在下，延长的有效衰变时间，进一步增强与粒子$N$的数量增加，由玻色子因子$\sqrt{N}$在福克制度和$N/\log{N}$在约瑟夫森制度。
英文摘要：
We study the effect of decoherence on dynamical phase diffusion in the two-site Bose-Hubbard model. Starting with an odd parity excited coherent state, the initial loss of single particle coherence varies from small bound oscillations in the Rabi regime, through hyperbolic depletion in the Josephson regime, to a Gaussian decay in the Fock regime. The inclusion of local-site noise, measuring the relative number difference between the modes, is shown to enhance phase-diffusion. In comparison, site-indiscriminate noise measuring the population imbalance between the two quasi-momentum modes, slows down the loss of single-particle coherence. Decoherence thus either enhances or suppresses phase-diffusion, depending on the details of system-bath coupling and the overlap of decoherence pointer states with collisional-entanglement pointer states. The deceleration of phase-diffusion due to the coupling with the environment may be viewed as a many-body quantum-Zeno effect. The extended effective decay times in the presence of projective measurement, are further enhanced with increasing number of particles $N$, by a bosonic factor of $\sqrt{N}$ in the Fock regime and $N/\log{N}$ in the Josephson regime.
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