Exploring boundaries of quantum convex structures: special role of unitary processes
| Authors | |
|---|---|
| Year of publication | 2015 |
| Type | Article in Periodical |
| Magazine / Source | Phys. Rev. A |
| MU Faculty or unit | |
| Citation | |
| Web | http://dx.doi.org/10.1103/PhysRevA.92.012304 |
| Doi | http://dx.doi.org/10.1103/PhysRevA.92.012304 |
| Field | Theoretical physics |
| Keywords | quantum structure - quantum measurement - quantum information |
| Description | We address the question of finding the most unbalanced convex decompositions into boundary elements (so-called boundariness) for sets of quantum states, observables, and channels. We show that in general convex sets the boundariness essentially coincides with the question of the most distinguishable element, thus providing an operational meaning for this concept. Unexpectedly, we discovered that for any interior point of the set of channels the most unbalanced decomposition necessarily contains a unitary channel. In other words, for any given channel the most distinguishable one is some unitary channel. Further, we prove that boundariness is submultiplicative under the composition of systems and explicitly evaluate its maximal value that is attained only for the most mixed elements of the considered sets. |
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