Measurement of the space-time relation in quantum coherence propagation

Summary form only given.In the process of induced coherence without induced emission, photons spontaneously emitted from two parametric downconverters exhibit interference when the possibility of identifying the photon's path is removed. On the other hand, when it becomes possible to perform an auxiliary measurement to obtain such path information, even in the absence of any direct disturbance to the photons, the interference disappears. In this paper, we measure the space-time relation between the event making it possible to identify the photon's path and the resulting disappearance of interference.