Nonresonant two-level transitions: Lessons from quantum thermodynamics

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