Linear optics with projective measurements for fun and profit
Pieter Kok, Hwang Lee, Colin P. Williams, Jonathan P. Dowling · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2003
The technique of projective measurements in linear optics can provide apparent, efficient nonlinear interaction between photons, which is technically problematic otherwise. We present an application of such a technique to prepare large photon-number path entanglement. Large photon-number path entanglement is an important resource for Heisenberg-limited optical interferometry, where the sensitivity of phase measurements can be improved beyond the usual shot-noise limit. A similar technique can also be applied to signal the presence of a single photon without destroying it. We further show how to build a quantum repeater for long-distance quantum communication.