Does anyone know of a quantum theory of the past. If I measure an observable, this gives me certain information of the possible states it has been in before the wave function collapse. I can exclude those states without any overlap with the observed eigenstate. But it is more complicated than this. Often we have prepared a state so we know exactly what state it was in before. Whatever a single measurement yields. We seem to be pretty sure about the past, and that it is classical. Decoherence doesn't work well backwards in time, and wave function collapse doesn't look too compatible with SRT. Is there any theory about this. Can someone point out some papers or books?