Unital Quantum Channels – Convex Structure and Revivals of Birkhoff’s Theorem

  title={Unital Quantum Channels – Convex Structure and Revivals of Birkhoff’s Theorem},
  author={Christian B. Mendl and Michael M. Wolf},
  journal={Communications in Mathematical Physics},
  • C. Mendl, M. Wolf
  • Published 17 June 2008
  • Mathematics, Physics
  • Communications in Mathematical Physics
The set of doubly-stochastic quantum channels and its subset of mixtures of unitaries are investigated. We provide a detailed analysis of their structure together with computable criteria for the separation of the two sets. When applied to O(d)-covariant channels this leads to a complete characterization and reveals a remarkable feature: instances of channels which are not in the convex hull of unitaries can become elements of this set by either taking two copies of them or supplementing with a… Expand

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