Onset of non-Gaussian quantum physics in pulsed squeezing with mesoscopic fields

TL;DR

This paper investigates the transition from Gaussian to non-Gaussian quantum features in pulsed squeezed light with mesoscopic photon numbers, highlighting the role of nonlinearities and entanglement in complex quantum dynamics.

Contribution

It introduces a nonlinear Gaussian approximation framework with a Gaussian interaction frame to model non-Gaussian quantum dynamics in mesoscopic pulsed squeezing.

Findings

Non-Gaussian distortions are significant in mesoscopic regimes.

Signal-pump entanglement is a key factor in non-Gaussian features.

The model provides insights into the quantum-classical transition in nonlinear optics.

Abstract

We study the emergence of non-Gaussian quantum features in pulsed squeezed light generation with a mesoscopic number (i.e., dozens to hundreds) of pump photons. Due to the strong optical nonlinearities necessarily involved in this regime, squeezing occurs alongside significant pump depletion, compromising the predictions made by conventional semiclassical models for squeezing. Furthermore, nonlinear interactions among multiple frequency modes render the system dynamics exponentially intractable in na\"ive quantum models, requiring a more sophisticated modeling framework. To this end, we construct a nonlinear Gaussian approximation to the squeezing dynamics, defining a "Gaussian interaction frame" (GIF) in which non-Gaussian quantum dynamics can be isolated and concisely described using a few dominant (i.e., principal) supermodes. Numerical simulations of our model reveal non-Gaussian distortions of squeezing in the mesoscopic regime, largely associated with signal-pump entanglement. We argue that the state of the art in nonlinear nanophotonics is quickly approaching this regime, providing an all-optical platform for experimental studies of the semiclassical-to-quantum transition in a rich paradigm of coherent, multimode nonlinear dynamics. Mesoscopic pulsed squeezing thus provides an intriguing case study of the rapid rise in dynamic complexity associated with semiclassical-to-quantum crossover, which we view as a correlate of the emergence of new information-processing capacities in the quantum regime.