Quantum Thermodynamics is the study of the relations between two independent physical theories: thermodynamics and quantum mechanics.
Quantum Open Systems
Quantum thermodynamics is based on a series of idealizations in a similar fashion to the ideal gas model, which serves classical thermodynamics. The theory of quantum open systems is that the inspiration for several inventions. The primary goal of open quantum systems theory is to develop a confined dynamical description of the dynamics of a system coupled to an environment termed “reduced dynamics”. The variables of the concept are defined by local system observables. These Entropy 2013, 15 2103 observables constitute the quantum thermodynamic description. To account for possible system-bath entanglement, the system has to be described by a mixed state, ρˆS. Observables are obtained from hOˆ i = Tr{ρˆSOˆ }
It is customary to assume that the whole world is a largely closed system, and thus, time evolution is governed by a unitary transformation generated by a worldwide Hamiltonian.
For the combined system bath scenario, the global Hamiltonian can be decomposed into Hˆ = Hˆ S + Hˆ B + Hˆ SB
where Hˆ S is the system’s Hamiltonian, Hˆ B the bath Hamiltonian and Hˆ SB the system-bath interaction.