Nondestructive single-photon trigger - art. no. 032311

A triggering device sensitive to a single photon is discussed. It is based on a balanced quantum nondemolition (QND) measurement proposed by Chuang an d Yamamoto [Phys. Rev. Lett. 76, 4281 (1996)]. The balanced measurement mea sures the total photon number and obtains no which-path/mode information. H ence, the timing of the photon can be determined without destroying its wav e function or entangling the probe held. This could have extensive use in t he realization of long-distance quantum communications systems.