Wigner function negativity in a classical model of quantum light

TL;DR

This paper shows that a classical model, with post-selection, can reproduce negative Wigner functions typically associated with quantum nonclassical states, challenging the notion that negativity is exclusively quantum.

Contribution

The authors present a classical model that, combined with post-selection, can mimic quantum Wigner function negativity observed in photon-added states.

Findings

Classical model reproduces negative Wigner functions.

Post-selection enables classical mimicry of quantum features.

Demonstrates classical explanation for certain quantum phenomena.

Abstract

The presence of negative values in the Wigner quasiprobability distribution is deemed one of the hallmarks of nonclassical phenomena in quantum systems. Here we demonstrate a classical model of squeezed light that, when combined with post-selection on amplitude threshold-crossing detection events, is capable of reproducing observed behavior of single-photon added coherent states. In particular, a classical model of balanced homodyne detection and standard tomographic techniques are used to infer the density matrix in the Fock basis. The resulting Wigner functions exhibit negatively for photon-added vacuum and weak coherent states.