You would think this, but the quantum erasure experiment appears to demonstrate that a photon which has been marked so as to determine its path and then subsequ

You would think this, but the quantum erasure experiment appears to demonstrate that a photon which has been marked so as to determine its path and then subsequently randomly unmarked so as to irretrievably destroy that information once again displays interference. The delayed choice quantum eraser appears to demonstrate that this decision to either record or destroy path information may be delayed until after the reference photon has arrived at the detector, with corresponding absence or presence of interference. It's not just about interaction causing collapse, or, if it is, a particle which has been interacted with and collapsed may be subsequently uninteracted with and uncollapse back into a wave. http://en.wikipedia.org/wiki/Quantum_eraser http://en.wikipedia.org/wiki/Quantum_eraser http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser