The role of auxiliary photons in the problem of identifying a state secretly chosen from a given set of L-photon states is analyzed. It is shown that auxiliary photons do not increase the ability to discriminate such states by means of a global measurement using only optical linear elements, conditional transformation and auxiliary photons.
@article{arxiv.quant-ph/0106041,
title = {The role of auxiliary states in state discrimination with linear optical evices},
author = {Angelo Carollo and G. Massimo Palma},
journal= {arXiv preprint arXiv:quant-ph/0106041},
year = {2016}
}