Irreversibility and quantum correlations

Abstract

Irreversibility represents one of the most enigmatic concepts in thermodynamics. The laws of motion, such as Newtons law or Schrödingers equation, are all invariant under time reversal. However, when we deal with macroscopic objects, we find that their behavior is irreversible. The solution to this paradox comes from the interpretation of irreversibility as an emergent phenomenon, which appears due to the complex interaction between a large number of particles. Understanding this transition from micro to macro constitutes one of the most relevant problems in modern physics. In this project we propose to relate the concept of irreversibility with the correlation between quantum systems. We know from the laws of quantum mechanics that when two systems interact, they become entangled (that is, correlated). However, if one of the systems is sufficiently large, this entanglement may be irrevocably lost. From a microscopic point of view, it is this loss of entanglement which causes the appearance of an irreversible dynamics. In this project we propose to study this problem by means of the spin-boson model, which is a famous and analytically soluble model. We shall study the problem in the case where the bosonic component has a certain degree of squeezing, which will serve to allows to consider quantum fluctuations with pure states. This project deals with results which are at the frontier of knowledge but, at the same time, are accessible to an undergraduate student. It is our hope that the results we will obtain here will help us clarify important concepts in the field of quantum thermodynamics and open quantum systems. (AU)