Thermodynamics in the presence of initial coherences and correlations

Abstract

One of the main trends in modern technology is the constant miniaturization of electronic devices. In doing so, it is inevitable that quantum effects will eventually be an unavoidable feature in the planing and fabrication of new instruments; considerations about their power output and energy efficiency lie beyond the scope of classical physics. This regime demands a generalization of the laws of thermodynamics that accounts for the interconversion between classical and quantum resources. This thesis fills this gap by providing a general method to extend the second law of thermodynamics to account for genuine quantum features. These include state coherences consumed in the energy basis and quantum correlations between the system of interest and its environment. We show with our framework that the consumption of coherences is a necessary condition for improved work extraction. For it to be sufficient, we show that one must carefully consider the decoherence timescales. We proceed to investigate two general classes of systems in which quantum resources naturally occur. We begin by studying the thermal properties of generalized Gibbs ensembles, i.e., systems whose conserved quantities do not commute. Then, we explore open quantum systems where the steady state contains non-negligible correlations as consequence of strong interaction strengths with their enviroments. In both cases, we show under which conditions one can use quantum resources to improve the performance of thermal processes, paving the way to efficient design at the nanoscale.