Experimental direct estimation of nonlinear functionals of photonic quantum states via interferometry with a controlled-swap operation.
We propose a multi-photon interferometer with a generalized C-SWAP operation that can estimate Tr[ρ(1)ρ(2)···ρ(n)], a nonlinear functional of n photonic density matrices. The scheme is demonstrated for three single-photon states whose overlap is experimentally measured as the interference visibility of a control qubit encoded into photonic paths. The validity of this method is verified by comparing the visibility with the results of Hong-Ou-Mandel experiments.
Korea Research Institute of Standards and Science, Daejeon 305-340, South Korea.
Sang Min
SM
Lee
Sang-Kyung
SK
Choi
Hee Su
HS
Park
D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007368:Interferometry / Q000295:instrumentation* / Q000379:methods*; D008027:Light; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D017785:Photons; D011789:Quantum Theory; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation