Characterization of nonclassicality of Gaussian states initially generated in optical spontaneous parametric processes by means of induced stimulated emission

TL;DR

This paper compares the effectiveness of nonclassicality witnesses in identifying Gaussian states generated via spontaneous and stimulated parametric processes, highlighting the practical advantages of stimulated emission in experiments.

Contribution

It demonstrates that stimulated emission enhances the detection of nonclassicality in Gaussian states, offering a practical method for experimental identification using simple linear detectors.

Findings

Stimulated emission allows complete identification of nonclassicality.

Nonclassicality witnesses are more effective with stimulated processes.

The method is experimentally feasible with linear detectors.

Abstract

In a recent paper [I.I. Arkhipov, Phys. Rev. A 98, 021803 (2018)], it was shown that one can completely identify the nonclassicality of single- and two-mode Gaussian states by means of certain nonclassicality witnesses which are based on intensity moments up to the third order of optical fields, provided that an appropriate coherent displacement is applied to a given Gaussian state. Here, we utilize a mathematical equivalence between the description of the coherent displaced Gaussian states generated in the spontaneous parametric processes and the Gaussian states generated in the corresponding stimulated parametric processes. Resorting to that equivalence, we study and compare the power of those nonclassicality witnesses in the detection of the nonclassicality of the two-mode Gaussian states generated in both the spontaneous and stimulated second subharmonic and down-conversion processes and which are subsequently subject to a beam splitter. We demonstrate that by means of an appropriate induced stimulated emission one can completely identify the nonclassicality of the considered Gaussian states in comparison to the case of the spontaneous emission. This is important from the experimental point of view, as the stimulated emission can be easily implemented in running optical experiments, and such method can exploit just simple linear detectors.