Out-of-equilibrium atomic systems may be used to develop quantum thermal machines which operate continuously at steady state. At such small scales, the energy currents characterizing work and heat exchange with thermal reservoirs exhibit fluctuations large enough to play a significant role in evaluating machine performance. I introduce here a novel set of bounds on the performance of steady-state quantum thermal machines which involve the fluctuations in their input and output energy currents. Namely, the ratio of a machine's output to input fluctuations is bounded from below by the square of its efficiency, and from above by the square of the relevant Carnot bound. This leads to a tighter-than-Carnot bound on the efficiency itself. I will describe a model-independent proof of these results for systems near equilibrium. I will also discuss efforts to extend these results to the far-from-equilibrium regime, in the context of the quantum absorption refrigerator: a paradigmatic model for a thermal machine which can be realized using atomic systems.
|Presenter name||Matthew Gerry|