Breaking the Carnot limit without violating the second law: A thermodynamic analysis of offresonant quantum light generation
Abstract
The Carnot limit, formulated in 1824, represents the maximal efficiency of a classical heat engine. In this work we present a thermodynamical analysis of a light amplifier based on a threelevel atom coupled offresonantly to a single quantized cavity mode and to two heat reservoirs with positive temperatures. Based on standard work and heat flow equilibrium, we show that for a cavity bluedetuned with respect to the atomic resonance, the system can surpass the Carnot limit. Nevertheless, the second law of thermodynamics is still obeyed, as the total entropy always increases. By analyzing a semiclassical version of the model, we derive a formula for the critical frequency for which the Carnot limit is broken and a formula for the amplifier efficiency which agrees with its quantum counterpart. In the semiclassical regime, however, the second law is not satisfied and hence it does not offer a physically acceptable description of the system. Finally, we show that breaking the Carnot limit occurs also in a bluedetuned quantum amplifier with output coupling, which represents a realistic model of a laser or maser.
 Publication:

Physical Review A
 Pub Date:
 June 2013
 DOI:
 10.1103/PhysRevA.87.063845
 Bibcode:
 2013PhRvA..87f3845B
 Keywords:

 42.50.Ct;
 05.70.Ln;
 Quantum description of interaction of light and matter;
 related experiments;
 Nonequilibrium and irreversible thermodynamics