Entropy production and correlation spreading in the interaction between particle detector and thermal baths

Abstract

Entropy production is the key quantity behind the second law of thermodynamics, and it is well defined by considering a joint unitary evolution of a system S and a thermal environment E. However, due to the diversity of initial state and Hamiltonian of S and E, it is hard to evaluate the characterization of the entropy production. In this Letter we propose that the evolution of S and E can be solved non-perturbatively in the framework of Gaussian quantum mechanics (GQM) for Gaussian states and quadratic Hamiltonian. We study the entropy production and correlation spreading in two models of E: one-dimensional free massless scalar quantum field theory in a cavity and an oscillator chain with adjacent interactions. The result is not what one might naively expect, S being thermalized and keeps stable, but is all the physical quantities, such as entropy production, mutual information, and the effective temperature of S, are fluctuating. In general the interaction between S and E creates correlation, and this correlation could spread in E and cause the physical quantities to fluctuate. The detailed information depends on the coupling strength, number of modes, boundary condition and other parameters. This analysis can be extended to any other models in the framework of QGM.

Decoherence and Landauer’s principle in qubit-cavity quantum-field-theory interaction

“…We believe that the analysis of qubit-QFT interaction and decoherence can be applied to more contexts, both theoretical and experimental, to deepen our understanding of quantum phenomena. If we use harmonic oscillators instead of qubit to be the system, the interaction can also be solved non-perturbatively in the framework of Gaussian quantum mechanics [18][19][20].…”