Breaking the Carnot limit without violating the second law: A thermodynamic analysis of off-resonant quantum light generation

摘要

The Carnot limit, formulated in 1824, represents the maximal efficiency of a classical heat engine. In this worknwe present a thermodynamical analysis of a light amplifier based on a three-level atom coupled off-resonantlynto a single quantized cavity mode and to two heat reservoirs with positive temperatures. Based on standardnwork and heat flow equilibrium, we show that for a cavity blue-detuned with respect to the atomic resonance,nthe system can surpass the Carnot limit. Nevertheless, the second law of thermodynamics is still obeyed, asnthe total entropy always increases. By analyzing a semiclassical version of the model, we derive a formula for thencritical frequency for which the Carnot limit is broken and a formula for the amplifier efficiency which agreesnwith its quantum counterpart. In the semiclassical regime, however, the second law is not satisfied and hence itndoes not offer a physically acceptable description of the system. Finally, we show that breaking the Carnot limitnoccurs also in a blue-detuned quantum amplifier with output coupling, which represents a realistic model of anlaser or maser.