Observable nonclassicality witnesses for multiplexed detection systems

TL;DR

This paper develops new measurable criteria for detecting nonclassical light in multiplexed photon-counting systems, significantly expanding the set of available nonclassicality witnesses and enabling detailed analysis of complex quantum states.

Contribution

It introduces a novel class of nonclassicality witnesses based on half-integer powers of click moments, increasing the number of criteria exponentially and applicable to multimode optical systems.

Findings

New criteria based on counting statistics and matrices of counting moments.

Exponential increase in the number of nonclassicality witnesses.

Applicable to spatial, time-bin multiplexing, and multimode scenarios.

Abstract

We address the problem of constructing witnesses for nonclassical light that are applicable in state-of-the-art photon-counting devices. The key ingredient for the criteria we derive are generalized and directly measurable counting statistics and matrices of counting moments. Beyond common criteria, we find classes of witnesses that are based on half-integer powers of click moments and counts. Remarkably, this leads to an exponential increase of the number of nonclassicality criteria one can construct and apply. With this finding, special attention is payed to probing even and odd parity states, requiring such distinct witnesses. Our method is applicable to spatial and time-bin multiplexing in optical systems, where each spatial and temporal mode can be measured with both on-off detectors and detectors with partial internal quasi-photon-number resolution. Generalizations to multimode scenarios are provided, allowing for the direct measurement of nonclassical correlations and coincidence counts between an arbitrary number of modes.