物信讲坛第七十四讲：Quantum Thermodynamics from the Nonequilibrium
主 讲 人：胡悲乐
主 办 方：物理与信息工程学院
Quantum Thermodynamics in a stricter definition is the study of the thermodynamical properties of quantum many-body systems. In fusing the two terms quantum and thermodynamics together it exposes the intrinsic dislocations or even contradictions, namely, while quantum deals with the microscopic world and quantum features manifest usually at low or zero temperatures, thermodynamics is formulated mainly in the context of classical phenomena, restricted to the macroscopic realm, and functions better at high enough temperatures where thermal properties prevail over quantum. However, quantum thermodynamics is interesting precisely because of these dislocations. They bring out foundational issues at the micro-macro (m-M) and the quantum-classical (q-C) interface. In our opinion, a basic approach which can unify both aspects and offer more is the nonequilibrium dynamics of open quantum systems. Using a Brownian motion model which is exactly solvable we come to a better understanding of several foundational issues at the m-M/q-C interface from this broader perspective such as the conditions for the applicability of the canonical ensemble and the validity of the thermodynamics laws. Our approach is fundamentally different from many ongoing work on quantum thermodynamics which has produced important results in the last two decades whose setup assumes that the combined system and its environment is in a thermal state throughout. The set-up of a closed quantum system in a thermal state explores the conditions for the establishment of equilibrium quantum statistical mechanics, it is easy to define the thermodynamic quantities but difficult to extract the system dynamics and describe its nonquilibrium thermodynamics. In an open quantum system set-up these can more easily be obtained, as our present program demonstrates.