The first law of general quantum resource theories

Abstract

We introduce a general framework of quantum resource theories with multiple resources. We derive conditions for the interconversion of these resources, which serve as a generalisation of the first law of thermodynamics. We study reversibility conditions for multi-resource theories, and find that the relative entropy distances from the invariant sets of the theory play a fundamental role in the quantification of the resources. The first law for general multi-resource theories is a single relation which links the change in the properties of the system during a state transformation and the weighted sum of the resources exchanged. In fact, this law can be seen as relating the change in the relative entropy from different sets of states. We apply these results to thermodynamics, and to the theory of local control under energetic restrictions. In contrast to typical single resource theories, the notion of free states and invariant sets of states become distinct in light of multiple resources. Additionally, generalisations of the Helmholtz free energy, and of adiabatic and isothermal transformations, emerge. We thus have a set of laws for general quantum resource theories, which look similar to those found in thermodynamics and which can be applied elsewhere.