|Tytuł||Distinguishing classically indistinguishable states and channels|
|Publication Type||Journal Article|
|Autorzy||Korzekwa K, Czachórski S, Puchała Z, Życzkowski K|
|Journal||Journal of Physics A: Mathematical and Theoretical|
We investigate an original family of quantum distinguishability problems, where the goal is to perfectly distinguish between M quantum states that become identical under a completely decohering map. Similarly, we study distinguishability of M quantum channels that cannot be distinguished when one is restricted to decohered input and output states. The studied problems arise naturally in the presence of a superselection rule, allow one to quantify the amount of information that can be encoded in phase degrees of freedom (coherences), and are related to time-energy uncertainty relation. We present a collection of results on both necessary and sufficient conditions for the existence of M perfectly distinguishable states (channels) that are classically indistinguishable.