Quantum postselective measurements: Sufficient condition for overcoming the Holevo bound and the role of max-relative entropy
N. R. Kenbaev, Dmitry Anatolevich Kronberg · Physical Review A · 2022
The operation of unambiguous state discrimination (USD) plays an important role in quantum information theory. Here, we study the generalization for this operation which can be applied where USD is not available, including the case of completely coinciding supports. We demonstrate the effect of overcoming the Holevo bound after postselective measurements, which works for a class of ensembles, including two arbitrary noncommuting quantum states. We also discuss the role of max-relative entropy in postselective measurements and give an alternative operational interpretation for this function.