Abstract

We consider unambiguous identification of coherent states of electromagnetic field. In particular, we study possible generalizations of an optical setup proposed in M. Sedl´ak et al., Phys. Rev. A 76, 022326 (2007). We show how the unambiguous identification of coherent states can be performed in a general case when multiple copies of unknown and the reference states are available. We also investigate whether reference states after the measurement can be “recovered” and further used for subsequent unambiguous identification tasks. We show that in spite of the fact that the recovered reference states are disturbed by measurements they can be repeatedly used for unambiguous iden- tifications. We analyze the role of various imperfections in preparation of the unknown and the reference coherent states on the performance of our unambiguous identification setup.