It was recently pointed out in [J. P. Santos, L. C. Celeri, G. T. Landi, and M. Parenostro, npj Quantum Information 5:23 (2019)] that quantum systems going through dissipative processes present two sources of irreversibility: one from populations and one from coherences. In this talk we show that for degenerate (or near-degenerate) systems, additional contributions to the entropy production emerge [1]. Remarkably, such additional contributions can become negative, marking the departure from usual (classical) thermodynamics through two distinct phenomena. The first one is the reversal of the natural convergence of the populations: instead of converging towards the thermal equilibrium distribution, the populations go away from it. This can also be related in some specific situations to the heat flow reversals recently introduced in [2]. The second phenomena is the generation of coherences between degenerate energy levels. It can be shown that its inherent negative contribution to the entropy production is the origin of the large reduction of entropy production recently reported in collective dissipation [3]. Furthermore, these two phenomena exhibit an insightful complementary relation: the consumption of one fuels the other, and reciprocally. Finally, we come back briey on some underlying crucial aspects such as degenerate transitions and collective coupling.
[1] C. L. Latune, I. Sinayskiy, F. Petruccione, arXiv:1910.14020.
[2] C. L. Latune, I. Sinayskiy, F. Petruccione, Phys. Rev. Research 1, 033097 (2019).
[3] C. L. Latune, I. Sinayskiy, F. Petruccione, arXiv:1908.10384 (to appear in Phys. Rev. Research).
