# Collapse of the wave function and switching off measurement device before particles hit the wall detector

Would collapsing wave function by measuring/observing and then quickly turning off measurement device cause to uncollapse wave function? so it goes like this : wave--->particle---> wave(hits the wall)

Collapse is a misleading concept for a wavefunction leading to thinking that a wave function is a balloon that can collapse , then why not be filled up again?

Collapse of a wavefunction describing a particle means that an interaction happened. At the interaction time a new wavefunction describes the setup, dependent on the boundary conditions of the interaction. To get the original wavefunction back one would have to have the original boundary conditions and potential problem.

Would collapsing wave function by measuring/observing

Interaction= changed wavefunction.

and then quickly turning off measurement device cause to uncollapse wave function?

the measurement is at an instant anyway, and the particle travels with that wavefunction.

so it goes like this : wave--->particle---> wave(hits the wall)

No. The wave part describes the probability distribution of the particle. When it interacts one instance of that probability distribution is sampled. Probabilities do not hit a wall. Probabilities are sampled by interaction=hitting-the-wall. Interaction is always a particle, which interaction happens with a given probability.

• so in other words, NO? lets say I'm a god and I can at "instant" disable the photon detector before the light hits the wall, in such theoretical case the particle pattern will still appear on wall? – szufla Aug 11 '18 at 16:44
• No, the pattern will have changed because the existence of the detector changes the boundary conditions and therefore the wave function which is the solution for those conditions. In addition it is one throw of the dice, for one particle, so no pattern would appear anyway. see single electron double slit en.wikipedia.org/wiki/… – anna v Aug 11 '18 at 18:36