Robust Negativity in the Quantum-to-Classical Transition of Kerr Dynamics

TL;DR

This paper investigates how Kerr nonlinear dynamics transition from quantum to classical behavior under loss, identifying key time scales and showing the persistence of quantum features like Wigner-negativity in certain regimes.

Contribution

It introduces a detailed analysis of the quantum-to-classical transition in Kerr dynamics, highlighting the role of loss and system size in preserving nonclassical states.

Findings

Classical behavior dominates at short times with Gaussian dynamics.

Quantum superpositions are restricted by photon loss at long times.

Significant Wigner-negativity persists in the mean-field non-Gaussian regime.

Abstract

We quantify the quantum-to-classical transition of the single-mode Kerr nonlinear dynamics in the presence of loss. We establish three time scales that govern the dynamics, each with distinct characteristics. For times short compared to the Ehrenfest time, the evolution is classical, characterized by Gaussian dynamics. For sufficiently long times, as we increase the initial photon number, unitary Kerr evolution would generate macroscopic superpositions of coherent states (so-called kitten states), but this is severely restricted in the presence of small photon loss so that expectation values of observables coincide with their classical values. The intermediate time scale, however, shows resilient quantum behavior in the macroscopic limit. We show that in the mean-field non-Gaussian regime, the Kerr Hamiltonian (with small photon loss) generates a significant amount of Wigner-negativity, and classical flow is recovered only if the loss rate grows with system size. Our results broaden the usual understanding of quantum-to-classical transitions and demonstrate the potential for creating robust nonclassical resources for continuous-variable quantum information processing in the presence of loss.