Quantum enhancement of N-photon phase sensitivity by interferometric addition of down-converted photon pairs to weak coherent light

摘要

It is shown that the addition of down-converted photon pairs to coherentlaser light enhances the N-photon phase sensitivity due to the quantuminterference between components of the same total photon number. Since most ofthe photons originate from the coherent laser light, this method of obtainingnon-classical N-photon states is much more efficient than methods basedentirely on parametrically down-converted photons. Specifically, it is possibleto achieve an optimal phase sensitivity of about delta phi^2=1/N^(3/2), equalto the geometric mean of the standard quantum limit and the Heisenberg limit,when the average number of down-converted photons contributing to the N-photonstate approaches (N/2)^(1/2).