Experimental determination of a nonclassical Glauber-Sudarshan P function

TL;DR

This paper experimentally reconstructs a well-behaved Glauber-Sudarshan P function for a single-photon-added thermal state, directly visualizing nonclassicality through negativities, which is useful when other signatures fail.

Contribution

It introduces a method to experimentally determine a nonclassical P function that is well-behaved and visualizes nonclassicality directly, overcoming reconstruction challenges.

Findings

Reconstructed a nonclassical P function with negativities.

Demonstrated visualization of nonclassicality directly.

Method remains effective when other signatures do not persist.

Abstract

A quantum state is nonclassical if its Glauber-Sudarshan P function fails to be interpreted as a probability density. This quantity is often highly singular, so that its reconstruction is a demanding task. Here we present the experimental determination of a well-behaved P function showing negativities for a single-photon-added thermal state. This is a direct visualization of the original definition of nonclassicality. The method can be useful under conditions for which many other signatures of nonclassicality would not persist.