We analyze the benefit, in terms of extracting work, of having a single use of a quantum channel or measurement in quantum thermodynamics. This highlights a connection between unital and catalytic channels, and some subtleties concerning the conditional work cost of implementing a measurement given that a certain result was obtained. We also consider postselected measurements and show that any nontrivial postselection leads to an unbounded work benefit.
Bibliographical noteFunding Information:
The authors acknowledge helpful conversations with S. Popescu. T.P. acknowledges support from the EPSRC (Grant No. EP/S139151-108).
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