Exact Results in Quantum Theory

Quantum channels are maps between spaces of (mixed) quantum states which can be realized as unitary evolutions in an extended system. That is, they arise from unitaries by tracing out degrees of freedom, just as density matrices arise from pure states. In my talk I will discuss invariant channels between density matrices acting on irreducible representations of SU(2). I will show how they can be analyzed using coherent state quantization methods, for example how one can compute the von Neumann entropy of output states.