I have a question about quantum entanglement experiments, such as the two-photon "delayed choice" experiment performed by Aspect et al. http://prola.aps.org/abstract/PRL/v49/i25/p1804_1 [Broken]. Can anyone estimate how much time elapses between the arrival of a single photon at the detector, and the initiation of a current or voltage that could be considered "macroscopic"? I know too little about photomultipliers and the like to have any idea. In other words, does the experimental setup rule out the possibility that detector states become entangled with detected photon states, so that the "wavefunction collapse" is actually much later than the arrival of the photon at the detector? I am wondering if the time it takes for the detector to settle is long enough that a timelike signal could pass from one detector to another. Thanks in advance if anyone can shed light on this ... er .. so to speak.