Physics Department and NanoLund, Lund University, Box 118, 22100 Lund, Sweden.
Phys Rev Lett. 2019 Mar 22;122(11):110401. doi: 10.1103/PhysRevLett.122.110401.
We introduce an experimental test for ruling out classical explanations for the statistics obtained when measuring arbitrary observables at arbitrary times using individual detectors. This test requires some trust in the measurements, represented by a few natural assumptions on the detectors. In quantum theory, the considered scenarios are well captured by von Neumann measurements. These can be described naturally in terms of the Keldysh quasiprobability distribution (KQPD), and the imprecision and backaction exerted by the measurement apparatus. We find that classical descriptions can be ruled out from measured data if and only if the KQPD exhibits negative values. We provide examples based on simulated data, considering the influence of a finite amount of statistics. In addition to providing an experimental tool for certifying nonclassicality, our results bestow an operational meaning upon the nonclassical nature of negative quasiprobability distributions such as the Wigner function and the full counting statistics.
我们引入了一个实验测试，用于排除在使用单个探测器任意时间测量任意可观测量时获得的统计数据的经典解释。该测试需要对测量结果有一定的信任，这由探测器的几个自然假设来表示。在量子理论中，所考虑的情况可以通过冯·诺依曼测量很好地捕捉到。这些可以用凯尔迪什拟概率分布（KQPD）以及测量仪器的不精确性和反作用来自然地描述。我们发现，如果和仅当 KQPD 显示负值时，才能从测量数据中排除经典描述。我们基于模拟数据提供了一些示例，考虑了有限数量的统计数据的影响。除了为验证非经典特性提供一个实验工具之外，我们的结果还赋予了负拟概率分布（如维格纳函数和全计数统计）的非经典特性以操作性意义。
