Thermodynamics of laser systems

Halina Abramczyk

Ariane Soret, Massimiliano Esposito

We study the quantum thermodynamics of a coherent macroscopic electromagnetic field (laser) coupled to a two-level system (qubit) near resonance, from weak- to strong-driving regimes. This combined system is, in turn, weakly coupled to a thermal radiation field and can be described by an autonomous quantum master equation. We show that the laser acts as an autonomous work source and that, in the macroscopic limit, the work produced is independent of the phase of the laser. Using the dressed qubit approach, we show that the variation of energy in the laser is not the work transferred to the dressed qubit, which is instead obtained from the ``dressed laser''---a coherent superposition of the laser and the qubit. Using a two-point measurement technique with counting fields, we obtain the full counting statistics for the work of the laser and dressed laser, and show that they satisfy the Crooks fluctuation theorems. We then use these theorems as criteria to investigate the thermodynamic consistency of quantum master equations, first in the autonomous setup for the combined system, then in the nonautonomous setup for the quantum system where the coherent field is eliminated and effectively described by a time-dependent external field. Treating the laser as an external field is known to yield expressions for the work which are in contradiction with quantum thermodynamics predictions in the strong-driving regime. We show that these inconsistencies stem from a confusion between the laser and dressed laser, and show how to correct them. We also derive a generalized Bloch master equation, thermodynamically consistent across all driving regimes, from which the Bloch and Floquet master equations can be obtained using additional approximations (of which we also examine the consistency).

S. V. Petrushkin, Vitali V. Samartsev

Feng Wu, Lingen Chen, Shuang Wu +1 more

The quantum dynamic action of a laser cooling system is analyzed by means of a simplified luminescence center model with ground state and excited state in this paper. The thermodynamic performance of a laser cryocooler is described by solving quantum master equation. The cooling load and the coefficient of performance of the cooler are obtained by using finite time thermodynamics. Some features of the system under the weak coupling and under the intense coupling conditions are discussed.

Stig Stenholm

Robert Alicki

Göran Lindblad was one of the pioneers of what is now called quantum thermodynamics. From this vast and rapidly developing field, we have selected a sample of results concerning quantum open systems described by Markovian master equations of the Lindblad (Gorini–Kossakowski–Sudarshan) type, which are applied to models of lasers. One can study their thermodynamics using the properties of quantum relative entropy, also introduced by Lindblad.