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Work measurement as a generalized quantum measurement

Abstract

We present a new method to measure the work ww performed on a driven quantum system and to sample its probability distribution P(w)P(w). The method is based on a simple fact that remained unnoticed until now: Work on a quantum system can be measured by performing a generalized quantum measurement at a single time. Such measurement, which technically speaking is denoted as a POVM (positive operator valued measure) reduces to an ordinary projective measurement on an enlarged system. This observation not only demystifies work measurement but also suggests a new quantum algorithm to efficiently sample the distribution P(w)P(w). This can be used, in combination with fluctuation theorems, to estimate free energies of quantum states on a quantum computer.Comment: 4 page

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