  The ability to create and manipulate the spatio-temporal potentials is
essential in the diverse fields of science and technology. Here, we introduce
an optical feedback trap system based on a high precision position detection
and an ultrafast feedback control of a Brownian particle in the optical
tweezers to generate spatio-temporal virtual potentials of the desired shape in
a controlled manner. As an application, we study nonequilibrium fluctuation
dynamics of the particle in a time-varying virtual harmonic potential and
validate the Crooks fluctuation theorem in highly nonequilibrium condition.
