Optical experiment to test negative probability in context of quantum-measurement selection

TL;DR

This paper presents an experimental approach to interpret negative quasiprobabilities as indicators of nonclassicality in quantum systems through sequential polarization measurements of photons.

Contribution

It introduces an operational method to measure and interpret negativity in quasiprobabilities, linking it to measurement selection and nonclassicality.

Findings

Negativity reflects nonclassical photon behavior.

Sequential measurements reveal operational quasiprobability negativity.

The approach offers a new way to understand quantum nonclassicality.

Abstract

Negative probability values have been widely employed as an indicator of the nonclassicality of quantum systems. Known as a quasiprobability distribution, they are regarded as a useful tool that provides significant insight into the underlying fundamentals of quantum theory when compared to the classical statistics. However, in this approach, an operational interpretation of these negative values with respect to the definition of probability---the relative frequency of occurred event---is missing. An alternative approach is therefore considered where the quasiprobability operationally reveals the negativity of measured quantities. We here present an experimental realization of the operational quasiprobability, which consists of sequential measurements in time. To this end, we implement two sets of polarization measurements of single photons. We find that the measured negativity can be interpreted in the context of selecting measurements, and it reflects the nonclassical nature of photons. Our results suggest a new operational way to unravel the nonclassicality of photons in the context of measurement selection.