Abstract
Modern technologies could soon make it possible to investigate the operation cycles of quantum heat engines by counting the photons that are emitted and absorbed by their working systems. Using the quantum jump approach to open-system dynamics, we show that such experiments would give access to a set of observables that determine the trade-off between power and efficiency in finite-time engine cycles. By analyzing the single-jump statistics of thermodynamic fluxes such as heat and entropy production, we obtain a family of general bounds on the power of microscopic heat engines. Our new bounds unify two earlier results and admit a transparent physical interpretation in terms of single-photon measurements. In addition, these bounds confirm that driving-induced coherence leads to an increase in dissipation that suppresses the efficiency of slowly driven quantum engines in the weak-coupling regime. A nanoscale heat engine based on a superconducting qubit serves as an experimentally relevant example and a guiding paradigm for the development of our theory.
Highlights
In classical thermodynamics, a heat engine is described as a machine that uses a periodic series of thermodynamic processes to convert thermal energy into mechanical work [1]
A quantitative description of this trade-off between power and efficiency cannot be derived from the elementary laws of thermodynamics and requires a microscopic model for the dynamics of the working system, which we introduce
Quantitative bounds that make it possible to assess the trade-off between these two figures are key results of the theory of microscopic heat engines that has emerged over the last years
Summary
A heat engine is described as a machine that uses a periodic series of thermodynamic processes to convert thermal energy into mechanical work [1]. Microscopic heat engines have been realized on increasingly smaller length and energy scales with working systems such as a μm-sized silicon spring [47], colloidal particles [48,49,50,51,52], a single atom [53,54], nuclear [55], and electronic [56] spins or nitrogen-vacancy centers in diamond [57] In light of this rapid development, practical tests of trade-off relations between power and efficiency appear as a realistic challenge for near-future experiments.
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