2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16786We derive quantum analogues of Jarzynski's relations, and discuss two applications, namely, a derivation of the law of entropy increase for general compound systems, and a preliminary analysis of heat transfer between two quantum systems at different temperatures. We believe that the derivation of the law of entropy increase is new and of importance.11 pages. A remark is added at the end of Section 2.2Statistical Mechanicstext