Abstract
We expand the standard thermodynamic framework of a system coupled to a thermal reservoir by considering a stream of independently prepared units repeatedly put into contact with the system. These units can be in any nonequilibrium state and interact with the system with an arbitrary strength and duration. We show that this stream constitutes an effective resource of nonequilibrium free energy and identify the conditions under which it behaves as a heat, work or information reservoir. We also show that this setup provides a natural framework to analyze information erasure ("Landauer's principle") and feedback controlled systems ("Maxwell's demon"). In the limit of a short system-unit interaction time, we further demonstrate that this setup can be used to provide a thermodynamically sound interpretation to many effective master equations. We discuss how non-autonomously driven systems, micromasers, lasing without inversion, and the electronic Maxwell demon, can be thermodynamically analyzed within our framework. While the present framework accounts for quantum features (e.g. squeezing, entanglement, coherence), we also show that quantum resources do not offer any advantage compared to classical ones in terms of the maximum extractable work.
Highlights
Thermodynamics was traditionally designed to understand the laws that govern the behavior of macroscopic systems at equilibrium in terms of a few macroscopic variables containing very limited information about the microscopic state of the system
We extend the traditional framework of thermodynamics by considering a system which, in addition to being in contact with a thermal reservoir, interacts with a stream of external systems which we call “units.” Each independently prepared unit interacts for a certain time with the system before being replaced by another one, and no additional assumption about the state of the units nor the system-unit interaction is required
We neglect any subtleties arising from deriving a master equation (ME) for degenerate quantum systems and use a classical rate equation where those levels that interact with the reservoir are connected, as specified above
Summary
Thermodynamics was traditionally designed to understand the laws that govern the behavior of macroscopic systems at equilibrium in terms of a few macroscopic variables (e.g., temperature, pressure, chemical potential, energy, volume, particle number, etc.) containing very limited information about the microscopic state of the system. Remarkable progress has been made over the last decades to understand under which conditions the laws of thermodynamics emerge for small-scale systems where quantum and stochastic effects dominate and which are usually far away from thermal equilibrium This includes a consistent thermodynamic framework for driven systems weakly coupled to large and fast thermal reservoirs, which are described by a microscopically derived (quantum) master equation (ME) [1,2,3,4]. The benefit of our generalized thermodynamic framework is that it provides a unified perspective and encompasses many previously considered setups In modern physics, such setups have probably first been used in quantum optics, theoretically as well as experimentally, to model a maser in which a stream of atoms is injected into a cavity in order to macroscopically populate it [31,32,33]. Further analogies can be drawn with biomolecular motors or enzymes [11] which manipulate, e.g., nucleic acids (units) on a DNA strand, or with scattering theory where incoming and outgoing wave packets (units) interact for a short time with the scatterer (the system) [40,41]
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