Adapted-operator representations: Selective versus collective properties of quantum networks

Abstract

Based on local unitary operators acting on a n-dimensional Hilbert-space, we investigate selective and collective operator basis sets for N-particle quantum networks. Selective cluster operators are used to derive the properties of general cat-states for any n and N. Collective operators are conveniently used to account for permutation symmetry: The respective Hilbert-space dimension is then only polynomial in N and governed by strong selection rules. These selection rules can be exploited for the design of decoherence-free subspaces as well as for the implementation of efficient routes to entanglement if suspended switching between states of different symmetry classes could be realized.