Experimental test of the differential fluctuation theorem and realization of the Feynman’s ratchet with an optically trapped nanosphere (Conference Presentation)

Abstract

Nonequilibrium processes of small systems are ubiquitous in physics, biology, and chemistry. Optical tweezers provide an ideal tool for controlling small systems to investigate nonequilibrium thermodynamics. Recently, we performed the first experimental test of the differential fluctuation theorem, using an optically levitated nanosphere in air in both underdamped and overdamped regimes, and in both spatial and velocity spaces [Phys. Rev. Lett., 120, 080602 (2018)]. We also experimentally realized the Feynman’s ratchet, using a colloidal particle in water confined in an optical tweezer array under feedback control. Feynman's ratchet is a microscopic machine in contact with two heat reservoirs that was proposed by Richard Feynman in 1960’s to illustrate the second law of thermodynamics. Despite broad interests, an experimental realization of Feynman's ratchet has not been reported before our work.