Noiseless Linear Amplification with General Local Unitary Operations**Supported by the National Natural Science Foundation of China under Grant Nos 11304013, 11204197, 11204379 and 11074244, the National Basic Research Program of China under Grant No 2011CBA00200, the Doctor Science Research Foundation of Ministry of Education of China under Grant No 20113402110059, and Civil Aerospace 2013669.

Abstract

Noiseless linear amplification (NLA), first proposed by Ralpha et al., is a nondeterministic amplification process which gives gain to the Fock state |n〉 → gn|n〉, with g being the amplification gain. We here give a general framework for improving the NLA scheme with arbitrary general local unitary operations. We derive the improvement in the amplification gain in 0–1 photon subspace. In particular, we study if the local unitary is composed of single mode squeezing and coherent displacement operation. Finally, numerical simulations show that local unitary operation could give a further enhancement in the amplification gain as well as the success probability, making the NLA more feasible in future optic quantum communications.