Friction, classical and quantum

Friction at the macroscopic scale continues to be a thriving research area, in accordance with its undisputed importance in our life. At the microscopic scale, experiments show that in some cases, the friction between two solid surfaces can be vanishingly small. An open problem is whether friction between macroscopic bodies can result from quantum fluctuations. Recent experiments, in which the friction between two slabs of a quantum solid was actually measured, offer a way to answer this question.