Efficiency limits for linear optical processing of single photons and single-rail qubits
Dominic W. Berry, Alexander I. Lvovsky, Barry C. Sanders · Journal of the Optical Society of America B · 2007
We analyze the problem of increasing the efficiency of single-photon sources or single-rail photonic qubits via linear optical processing and destructive conditional measurements. We allow for the use of coherent states and do not limit to photon-counting measurements. We conjecture that, with the limitation that multiphoton components in the output are not permitted, it is not possible to increase the efficiency. We prove this conjecture for several important special cases, and provide extensive numerical results for the general case.