Perspective on quantum thermodynamics

Journal of Physics A: Mathematical and Theoretical, 2016

Thermodynamics in the Quantum Regime, 2018

arXiv: Quantum Physics, 2020

The evolution of the joint system (JS) - ``quantum system (QS)+thermal bath (TB)" is considered in the framework of a complex probabilistic processes that satisfies the stochastic differential equation of the Langevin-Schrodinger type. Two linearly coupled oscillators that randomly interact with the environment and with each other are selected as QS. In the case when the interactions obey the law of a white random process, all the construction of the statistical parameters of the QS and its environment are performed analytically in the form of double integrals and solutions of second-order partial differential equations. Expressions of time-dependent von Neumann entropy and its generalization are obtained, taking into account the self-organization and entanglement processes occurring in the JS. It is mathematically proved that as a result of the relaxation of JS in the TB, a small quantized environment is formed, which can be interpreted as a continuation of QS or its halo. Bel...

Scientific Reports, 2020

2014

Proceedings of the National Academy of Sciences of the United States of America, 2015

The second law of thermodynamics places constraints on state transformations. It applies to systems composed of many particles, however, we are seeing that one can formulate laws of thermodynamics when only a small number of particles are interacting with a heat bath. Is there a second law of thermodynamics in this regime? Here, we find that for processes which are approximately cyclic, the second law for microscopic systems takes on a different form compared to the macroscopic scale, imposing not just one constraint on state transformations, but an entire family of constraints. We find a family of free energies which generalize the traditional one, and show that they can never increase. The ordinary second law relates to one of these, with the remainder imposing additional constraints on thermodynamic transitions. We find three regimes which determine which family of second laws govern state transitions, depending on how cyclic the process is. In one regime one can cause an apparen...

arXiv: Quantum Physics, 2021

Fluctuations of thermodynamic observables, such as heat and work, contain relevant information on the underlying physical process. These fluctuations are however not taken into account in the traditional laws of thermodynamics. While the second law is extended to fluctuating systems by the celebrated fluctuation theorems, the first law is generally believed to hold even in the presence of fluctuations. Here we show that in the presence of quantum fluctuations, also the first law of thermodynamics may break down. This happens because quantum mechanics imposes constraints on the knowledge of heat and work. To illustrate our results, we provide a detailed case-study of work and heat fluctuations in a quantum heat engine based on a circuit QED architecture. We find probabilistic violations of the first law and show that they are closely connected to quantum signatures related to negative quasi-probabilities. Our results imply that in the presence of quantum fluctuations, the first law o...

Aapp Physical Mathematical and Natural Sciences, 2008

Physical Review E, 2016