Demonstration of controllable temporal distinguishability in a three-photon state

By using two processes of parametric down-conversion, we are able to generate three photons with controllable degree of temporal distinguishability. This is confirmed by the visibility in a three-photon interference experiment, which can be generalized to provide a practical technique for characterizing the temporal distinguishability of a multi-photon state. This method of quantitative description of multi-photon indistinguishability will have practical implications in the implementation of quantum information protocols