Thermodynamic indistinguishability and field state fingerprint of quantum optical amplifiers

TL;DR

This paper investigates a quantum optical amplifier's thermodynamic and quantum features, revealing that unique quantum phase space characteristics persist over time, distinguishing it from classical linear amplifiers.

Contribution

It demonstrates the thermodynamic equivalence of nonlinear and linear amplifiers while preserving quantum phase space features unique to the nonlinear case.

Findings

Quantum features in phase space are maintained over extended times.

The nonlinear amplifier is thermodynamically equivalent to the linear one.

Quantum fingerprints of initial states are preserved despite dissipation.

Abstract

Dissipation tends to wash out dynamical features observed at early evolution times. In this paper we analyze a resonant single--atom two--photon quantum optical amplifier both dynamically and thermodynamically. A detailed thermodynamic balance shows that the non--linear amplifier is thermodynamically equivalent to the linear amplifier discussed in (Phys. Rev. A, 74 (2006), 063822). However, by calculating the Wigner quasi--probability distribution for various initial field states, we show that unique quantum features in optical phase space, absent from the linear amplifier, are maintained for extended times. These features are related to the discrete nature of the two--photon matter--field interaction, and fingerprint the initial field state at thermodynamic times.