Nonresonant two-level transitions: Lessons from quantum thermodynamics

TL;DR

This paper analyzes a two-level quantum system coupled to a mode under detuning, deriving effective energies for thermodynamic consistency, and explaining phenomena like frequency pulling within a quantum thermodynamics framework.

Contribution

It introduces a thermodynamically consistent approach using effective energies for two-level systems under detuning, enhancing understanding of quantum thermodynamic processes.

Findings

Derived effective energies for levels and photons under detuning

Revealed thermodynamic basis for frequency pulling and Bloch gain

Provided a coherent thermodynamic interpretation of known quantum phenomena

Abstract

Based on concepts from quantum thermodynamics the two-level system coupled to a single electromagnetic mode is analyzed. Focusing on the case of detuning, where the mode frequency does not match the transition frequency, effective energies are derived for the levels and the photon energy. It is shown that these should be used for energy exchange with fermionic and bosonic reservoirs in the steady state in order to achieve a thermodynamically consistent description. While recovering known features such as frequency pulling or Bloch gain, this sheds light on their thermodynamic background and allows for a coherent understanding.