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[…] each of our optimal protocols contained at least one infinitely slow Step. This is unavoidable as the Process must be reversible before and after any measurements. Consequently, our method does not strictly apply to finite-time processes.
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HOROWITZ, Jordan M. and PARRONDO, Juan M. R., 2011. Designing optimal discrete-feedback thermodynamic engines. New Journal of Physics. December 2011. Vol. 13, no. 12, p. 123019. DOI 10.1088/1367-2630/13/12/123019. pdf 
Feedback can be utilized to convert information into useful work, making it an effective tool for increasing the performance of thermodynamic engines. Using Feedback Reversibility as a guiding principle, we devise a method for designing optimal feedback protocols for thermodynamic engines that extracts all the information gained during feedback as work. Our method is based on the observation that in a feedback-reversible process the measurement and the time-reversal of the ensuing protocol both prepare the system in the same probabilistic state. We illustrate the utility of our method with two examples of the multi-particle Szilard engine.