Abstract

The second law of thermodynamics tells us which state transformations are so statistically unlikely they are effectively forbidden. It applies to systems composed of many particles and concerns average quantities. Recently, using results from quantum information theory, we are seeing that one can make sense of thermodynamics in the regime where we only have a small number of particles, or even a single quantum system. If we don’t take the thermodynamic limit, the laws of thermodynamics are different. The standard second law of thermodynamics still holds, but there is an entire family of second laws which also must hold. One can also go beyond statements about average quantities and consider deterministic processes or quantify fluctuations around the average value. There are also fully quantum second laws which have no classical analog. After reviewing such recent results in the field of quantum thermodynamics, the question of whether such new laws can be applied to black holes will be raised, and recent progress in this direction discussed.