Lingua Fabio, Richaud Andrea, Penna Vittorio
Department of Physics, Clark University, Worcester, MA 01610, USA.
Department of Applied Science and Technology and u.d.r. CNISM, Politecnico di Torino, I-10129 Torino, Italy.
Entropy (Basel). 2018 Jan 25;20(2):84. doi: 10.3390/e20020084.
Motivated by the importance of entanglement and correlation indicators in the analysis of quantum systems, we study the equilibrium and the bipartite residual entropy in a two-species Bose-Hubbard dimer when the spatial phase separation of the two species takes place. We consider both the zero and non-zero-temperature regime. We present different kinds of residual entropies (each one associated with a different way of partitioning the system), and we show that they strictly depend on the specific quantum phase characterizing the two species (supermixed, mixed or demixed) even at finite temperature. To provide a deeper physical insight into the zero-temperature scenario, we apply the fully-analytical variational approach based on su(2) coherent states and provide a considerably good approximation of the entanglement entropy. Finally, we show that the effectiveness of bipartite residual entropy as a critical indicator at non-zero temperature is unchanged when considering a restricted combination of energy eigenstates.
受量子系统分析中纠缠和关联指标重要性的驱动，我们研究了两种玻色 - 哈伯德二聚体在发生空间相分离时的平衡态和二分剩余熵。我们考虑了零温和非零温情况。我们给出了不同类型的剩余熵（每种都与系统的不同划分方式相关），并且表明即使在有限温度下，它们也严格依赖于表征这两种物质的特定量子相（超混合、混合或分离）。为了更深入地理解零温情况的物理本质，我们应用基于su(2) 相干态的全解析变分方法，并对纠缠熵给出了相当好的近似。最后，我们表明在考虑能量本征态的受限组合时，二分剩余熵作为非零温度下临界指标的有效性不变。
