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## Sequential state discrimination of coherent states

Sequential state discrimination is a strategy for quantum state discrimination of a sender’s quantum

states when N receivers are separately located. In this report, we propose optical designs that can

perform sequential state discrimination of two coherent states. For this purpose, we consider not

only binary phase-shifting-key (BPSK) signals but also general coherent states, with arbitrary prior

probabilities. Since our optical designs do not include electric feedback, they can be implemented

without difficulty. Furthermore, we analyze our proposal for the case of photon loss. We also

demonstrate that sequential state discrimination of two coherent states performs better than the

probabilistic quantum cloning strategy. This proposal can facilitate multiparty QKD based on coherent

states.