In the two slit experiment there is an interference pattern generated whenever there are no detectors at the slits. This must mean that the wavefunction associated with the particles have not decohered. But the wavefunction must have interacted in some way with the barrier in order to produce the superposition state reflecting the presense of the two slits. But i thought that decoherence takes place whenever a wavefunction interacts with an object that is entangled with the environment, as presumably the barrier is. Why is it not happening in this case? If it isn't simply the interaction of the wavefunction with an object that is entangled with the environment that causes decoherence then what does cause it?