Thread: Wave Function Collapse

If a wave function collapses is the particle entanglement destroyed? This is what I have heard, I spent some time hunting, but I could never find an answer to this, so I've assumed it to be the general conensus.

I was wondering: If a wave function collapses, is that not a continuation of an association between two, or a group of, particles? Shouldn't the particles still be entangled? The other part of this which confuses me, does that imply that all particles are entangled with each other? Or does particle entanglement only occur when particles come into physical contact, and then ceases once that particular wave function collapses?

Additionally, depending on the responses, let's say two particles are entangled... If a 3rd particle causes a disturbance by physically contacting one of the other particles, will that 3rd particle now be entangled to both of the other particles?

Ok, I think you are getting a little confused here, which isn't suprising since quantum mechanics is not at all intuitive to most people. Consider the following :

1. Not all particles are automatically entangled
2. In order for entanglement to happen the two particles need to first interact in some way, and then become separated
3. Wave function collapse in this context means measuring the properties of one of these particles
4. After measurement takes place, the correlating properties of the other particle are exactly determined, even if the two are spatially seperated
5. Wave function collapse does not automatically mean that entanglement is broken
6. Entanglement is delicate, and only lasts until one or both of the particles interact with other particles
7. Entanglement only happens between a pair of particles, so no, a system of three particles is not normally entangled

Does this help to clear up the issue ? You may want to also read the Wikipedia article on quantum entanglement, it is a pretty good introduction.

That certainly does explain a number of problems I have been having with entanglement, thanks. I tried reading through WFC article on wikipedia, wasn't quite what I was looking for. But the quantum entanglement one you say? I'll give it a good browse. Again, thank-you for describing what I wasn't getting.

Originally Posted by stander-j

That certainly does explain a number of problems I have been having with entanglement, thanks. I tried reading through WFC article on wikipedia, wasn't quite what I was looking for. But the quantum entanglement one you say? I'll give it a good browse. Again, thank-you for describing what I wasn't getting.

No problem, you're welcome

The Wave function collapse is best envisaged in something like the 2 slit experiment. When firing one photon / electron at a time, the location of the individual particle is 'smeared out' along a probability wave however, introducing a detector into the experiment causes this wave to 'collapse' into a finite state any you will always detect the particle regardless of which slit you decide to check