限制高斯过程的柯克伍德 - 狄拉克负性
Bounding Kirkwood-Dirac negativity of Gaussian processes
AI总结：
研究高斯过程下任意量子态的柯克伍德 - 狄拉克准概率，推导出负性上界，发现单模和两次测量时正交算符本征态使上界饱和，纯高斯态达非平凡最小值，表明高斯态可实现非经典性极值。
AI中文摘要：
柯克伍德 - 狄拉克准概率提供了量子态的一种操作表示，其负性作为非经典性的一种度量。尽管其具有根本重要性，但一般情况下柯克伍德 - 狄拉克负性的极值仍未知。我们研究高斯过程下任意量子态的柯克伍德 - 狄拉克准概率。在此设定下，我们推导出任意模式数和测量数的负性上界。对于单模和两次测量，我们表明正交算符的本征态使该上界饱和，而纯高斯态达到非平凡最小值。结果表明高斯态足以实现非经典性的极值。
英文摘要：
The Kirkwood-Dirac quasiprobability provides an operational representation of a quantum state, whose negativity serves as a measure of nonclassicality. Despite its fundamental importance, the extremal values of the Kirkwood-Dirac negativity are still unknown in the general case. We investigate the Kirkwood-Dirac quasiprobability of an arbitrary quantum state under Gaussian processes. In this setting, we derive an upper bound on the negativity for any number of modes and measurements. For a single mode and two measurements, we show that the eigenstates of the quadrature operators saturate this upper bound, while a nontrivial minimum is reached by pure Gaussian states. As a consequence, our results indicate that Gaussian states are sufficient to achieve extreme values of nonclassicality.
