Experimental test of relativistic quantum state collapse with moving reference frames

An experimental test of relativistic wave-packet collapse is presented. The tested model assumes that the collapse takes place in the reference frame determined by the massive measuring detectors. Entangled photons are measur ed at 10 km distance within a time interval of less than 5 ps. The two appa ratuses are in relative motion so that both detectors, each in its own iner tial reference frame, are first to perform the measurement. The data always reproduces the quantum correlations and thus rule out a class of collapse models. The results also set a lower bound on the 'speed of quantum informa tion' to 2/3 10(7) and 3/2 10(4) times the speed of light in the Geneva and the background radiation, reference frames, respectively. The very difficu lt and deep question of where the collapse takes place-if it takes place at all-is considered in a concrete experimental context.