Realization of an information ratchet under real time feedback control

We have designed an information ratchet that is capable of transporting a Brownian particle in one direction and extracting work from a single heat bath by utilizing the information about the microscopic state of the system. The feedback control system is capable of performing an error-free measurements with a precision of 2 nm or less. By taking account of the unavailable information, we have demonstrated that the system achieves an upper bound of extractable work and thereby validates the generalized second law of thermodynamics. We have also confirmed the generalized Jarzyski equality for the case of error-free measurements.