Photon resolving detectors with near unit detection efficiency distinguish between a target state including n photons and a target state including n+1 photons by measuring a phase shift that a probe photon state receives in a quantum gate. The detection does not destroy the photons from the target state, so that photons can be used after detection. A system using a non-destructive detector in conjunction with one or more single photon storage systems can store a determined number of photons and release one or more stored photons when required to produce a photon state including a determined number of photons.