Abstract

By introducing the concept of global passivity we derive an extension of the second law of thermodynamics that can properly handle initial  quantum correlations (i.e., entanglement, and quantum discord) between the system and the environment. This extension is very important in nanoscopic setups where the environment may be small and strongly interacting with the system of interest. A second main finding of this framework is a family of additional thermodynamic relations that involve measurable quantities that were so far not constrained by thermodynamics. In particular, we use these relations to set upper and lower bounds on the buildup system-environment correlation in quantum dephasing (decoherence) scenarios. To illustrate the impact on thermodynamic theory, we show that global passivity can employed to detect subtle feedback demons that the second law cannot detect. Our findings are highly relevant for various modern experimental setups such as ion traps, atoms in an optical cavity or in optical lattices, and more.