QLunch: Pawel Mazurek
Speaker: Pawel Mazurek, University of Gdansk (Hosts: Paula Belzig and Matthias Christandl)
Title: Energy processing in quantum systems
Abstract:
Work extraction is a goal of both macroscopic and microscopic thermal machines. An additional subsystem called battery is implicitly or explicitly introduced in models of such machines, in order to quantify the extracted work as a function of the change of the state of the battery, resulting from the transformation. For example, we can think of the battery as a classical field, in which energy is stored. Interaction between the system and the classical field enables an arbitrary unitary operation on the system, and therefore ergotropy of the system is the measure of extractable work in this classical setting.
For explicite models of physical batteries in a quantum setting, there is no longer a guarantee that an arbitrary unitary operation can be applied. Moreover, quantum correlations between the explicit battery and the working body of the thermal machines may build up during their functioning. In this talk, I will present consequences for efficiency and work production (per cycle) of these quantum machines with a qubit working body. I will start with a discussion of the formulation of II law of thermodynamics in the resource-theoretic framework, followed by a discussion of an (unphysical) harmonic oscillator battery model with no lower bound on the energy spectrum. Structure of the set Thermal Operations will be related to that of the set of Transportation Matrices, in order to show that for dimension 4 and higher of the working body, not every extremal Thermal Operation needs to be executed in order to perform all allowed transitions. The optimal protocol for the functioning of the thermal machine will be presented, followed by a discussion of a role of information in energy processing tasks.
