论文标题
从量子断层图获得的纠缠指标中避免的能量水平穿越的签名
Signatures of avoided energy-level crossings in entanglement indicators obtained from quantum tomograms
论文作者
论文摘要
对避免避免的能量水平穿越的多部分系统的广泛理论和实验研究揭示了有趣的特征，例如纠缠的极端。从传统上讲，直接从实验观察结果中对纠缠的估计涉及两种方法之一：基于不确定性连接的估计，可捕获相关可观察结果之间的线性相关性，或对从同伴测量值获得的断层图上的严格但容易产生错误的量子态重建。我们研究了可以直接从数值生成的断层图中计算出的纠缠指标的行为，该行为接近避免过境。我们研究的系统是两个通用的二分连续变量系统：捕获双孔电势的玻色网冷凝物，以及与辐射场相互作用的多级原子。我们还考虑了与微波光子相互作用的超导量子位的多部分混合量子系统。我们对指标进行了定量比较，该指标具有标准的纠缠量测量，即子系统von Neumann熵（SVNE）。结果表明，捕获相关子系统可观察到的非线性相关性的指标与SVNE非常吻合。
Extensive theoretical and experimental investigations on multipartite systems close to an avoided energy-level crossing reveal interesting features such as the extremisation of entanglement. Conventionally, the estimation of entanglement directly from experimental observation involves either one of two approaches: Uncertainty-relation-based estimation that captures the linear correlation between relevant observables, or rigorous but error-prone quantum state reconstruction on tomograms obtained from homodyne measurements. We investigate the behaviour, close to avoided crossings, of entanglement indicators that can be calculated directly from a numerically-generated tomogram. The systems we study are two generic bipartite continuous-variable systems: a Bose-Einstein condensate trapped in a double-well potential, and a multi-level atom interacting with a radiation field. We also consider a multipartite hybrid quantum system of superconducting qubits interacting with microwave photons. We carry out a quantitative comparison of the indicators with a standard measure of entanglement, the subsystem von Neumann entropy (SVNE). It is shown that the indicators that capture the nonlinear correlation between relevant subsystem observables are in excellent agreement with the SVNE.
