Conditional control of measurement-driven machines

Abstract

The cycle model of a finite-time measurement-driven machine is proposed by repeatedly performing the quantum measurement, interaction of an atom with the single-mode field, and thermalization with heat reservoirs. The trajectories of the evolution of the atom reach a stationary probability distribution after sufficiently many iterations of the cycle, from which the average changes of the internal energy and the entropy of the atom are calculated. By taking the total work input as the sum of the average works during the measurement, unitary evolution, and information erasure processes, the energy conversion efficiencies of the machine as a refrigerator and a heat engine are determined. Results show that the cooperation of the quantum measurement and the unitary operation always turns the state of the atom into a desired state in every trajectory, yielding a high energy conversion efficiency. The investigation on the proposed model has potentially significant applications where the thermal manipulation at the quantum level is required.