从相互作用猝灭恢复光晶格中的量子关联
Recovering quantum correlations in optical lattices from interaction quenches
摘要：
利用超冷原子在光晶格中的量子模拟为理解强相互作用量子系统开辟了一条令人兴奋的道路。原子气体显微镜对此至关重要，因为它们提供了单点密度分辨率，这在其他量子多体系统中是无与伦比的。然而，目前还无法直接测量局部相干电流。在这项工作中，我们展示了如何通过测量响应于非相互作用动力学的猝灭而改变的密度来实现这一点，例如，在倾斜光晶格之后。为此，我们建立了一个数据分析方法，解决了一组封闭的方程有关的隧道电流和原子数动力学，允许可靠地恢复完整的协方差矩阵，包括非对角项表示相干电流。信号处理建立在半定优化的基础上，提供与观测数据最佳匹配的真正的协方差矩阵。我们展示了如何获得的信息，非对易观测允许下界纠缠在有限的温度下，打开了可能性，研究量子关联的量子模拟超越经典的能力。
英文摘要：
Quantum simulations with ultra-cold atoms in optical lattices open up an exciting path towards understanding strongly interacting quantum systems. Atom gas microscopes are crucial for this as they offer single-site density resolution, unparalleled in other quantum many-body systems. However, currently a direct measurement of local coherent currents is out of reach. In this work, we show how to achieve that by measuring densities that are altered in response to quenches to non-interacting dynamics, e.g., after tilting the optical lattice. For this, we establish a data analysis method solving the closed set of equations relating tunnelling currents and atom number dynamics, allowing to reliably recover the full covariance matrix, including off-diagonal terms representing coherent currents. The signal processing builds upon semi-definite optimization, providing bona fide covariance matrices optimally matching the observed data. We demonstrate how the obtained information about non-commuting observables allows to lower bound entanglement at finite temperature which opens up the possibility to study quantum correlations in quantum simulations going beyond classical capabilities.
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