Quantum fidelity of symmetric multipartite states

A. Neven, P. Mathonet, O. Gühne, T. Bastin
2016 Physical Review A  
For two symmetric quantum states one may be interested in maximizing the overlap under local operations applied to one of them. The question arises whether the maximal overlap can be obtained by applying the same local operation to each party. We show that for two symmetric multiqubit states and local unitary transformations this is the case; the maximal overlap can be reached by applying the same unitary matrix everywhere. For local invertible operations (stochastic local operations assisted
more » ... classical communication equivalence), however, we present counterexamples, demonstrating that considering the same operation everywhere is not enough.
doi:10.1103/physreva.94.052332 fatcat:ddpewmu74rbitjnhd3hogqppd4