Patent ID: 7049574

Claim:
A photon number state generating apparatus comprising: a photon pair source for generating a pair of photons consisting of a signal photon and an idler photon which are corrected in time of generation each other; a photon number detector for detecting a number of the idler photons; a gate device for controlling an emission of the signal photons; a controller for controlling the gate device in response to a photon number information from the photon number detector, a pulse height discriminator equipped in the controller for discriminating a photon number information having photon number within a specified range, wherein the controller controls the gate device in response to the photon number information from the photon number detector; wherein said controller comprises: a clock generator; and a gate operation frequency judging section for controlling the gate device to be opened or closed for less than a specified number of times within a predetermined time defined by a clock signal of the clock generator.