Dynamics, Information and Complexity in Quantum Systems
Dynamics, Information and Complexity in Quantum Systems
Entanglement of formation of rotationally symmetric states
Quantum Information & Computation
The capacity of the quantum channel with general signal states
IEEE Transactions on Information Theory
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We review some properties of the convex roof extension, a construction used, e.g., in the definition of the entanglement of formation. Especially we consider the use of symmetries of channels and states for the construction of the convex roof. As an application we study the entanglement entropy of the diagonal map for permutation symmetric real N = 3 states ω(z) and solve the case z ≤ 0 where z is the non-diagonal entry in the density matrix. We also report a surprising result about the behavior of the output entropy of the diagonal map for arbitrary dimensions N; showing a bifurcation at N = 6.