Naghiloo, M. and Alonso, J. J. and Romito, A. and Lutz, E. and Murch, K. W. (2018) Information gain and loss for a quantum Maxwell's demon. Physical review letters, 121 (3): 030604. ISSN 1079-7114
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Abstract
We use continuous weak measurements of a driven superconducting qubit to experimentally study the information dynamics of a quantum Maxwell's demon. We show how information gained by a demon who can track single quantum trajectories of the qubit can be converted into work using quantum coherent feedback. We verify the validity of a quantum fluctuation theorem with feedback by utilizing information obtained along single trajectories. We demonstrate, in particular, that quantum backaction can lead to a loss of information in imperfect measurements. We furthermore probe the transition between information gain and loss by varying the initial purity of the qubit.