Quantum and Information Thermodynamics: A Unifying Framework Based on Repeated Interactions

We expand the standard thermodynamic framework of a system coupled to a thermal reservoir by
<br />considering a stream of independently prepared units repeatedly put into contact with the system. These
<br />units can be in any nonequilibrium state and interact with the system with an arbitrary strength and
<br />duration. We show that this stream constitutes an effective resource of nonequilibrium free energy, and we
<br />identify the conditions under which it behaves as a heat, work, or information reservoir. We also show that
<br />this setup provides a natural framework to analyze information erasure (“Landauer’s principle”) and
<br />feedback-controlled systems (“Maxwell’s demon”). In the limit of a short system-unit interaction time, we
<br />further demonstrate that this setup can be used to provide a thermodynamically sound interpretation to
<br />many effective master equations. We discuss how nonautonomously driven systems, micromasers, lasing
<br />without inversion and the electronic Maxwell demon can be thermodynamically analyzed within our
<br />framework. While the present framework accounts for quantum features (e.g., squeezing, entanglement,
<br />coherence), we also show that quantum resources do not offer any advantage compared to classical ones in
<br />terms of the maximum extractable work.