Direct observation of sub-binomial light

TL;DR

This paper demonstrates a method to directly observe nonclassical light states using multiplexed photon counters, enabling simpler and more practical characterization of quantum states without reconstructing photon distributions.

Contribution

The authors experimentally verify nonclassicality through detector click statistics alone, bypassing the need for photon number distribution inference, advancing quantum state characterization methods.

Findings

Successful direct detection of nonclassical light states

Validation of click statistics as nonclassicality witnesses

Potential for practical quantum state and detector characterization

Abstract

Nonclassical states of light are necessary resources for quantum technologies such as cryptography, computation and the definition of metrological standards. Observing signatures of nonclassicality generally requires inferring either the photon number distribution or a quasi-probability distribution indirectly from a set of measurements. Here, we report an experiment in which the nonclassical character of families of quantum states is assessed by direct inspection of the outcomes from a multiplexed photon counter. This scheme does not register the actual photon number distribution; the statistics of the detector clicks alone serve as a witness of nonclassicality, as proposed by Sperling et al. in Phys. Rev. Lett. 109, 093601 (2012). Our work paves a way for the practical characterisation of increasingly sophisticated states and detectors.