Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Concept of Quantum Entanglement

  1. Sep 15, 2015 #1

    This is my first post and I have come here as I cannot find an answer anywhere else.

    So, my physic knowledge is limited to what I learnt in High School, supplemented with the odd bit of further reading via books and the internet. However, many of the concepts I learnt about I find fascinating.

    At a very top level, I have read on the concept (not any of the underlying math etc) of entangled particles. My question is as follows, and this is where i cannot find an answer (so please bear with me).

    On the basis that two particles are entangled, at the point of measurement does their combined probability distribution wave collapse and therefore the clockwise spin, for example, of one mirror the anti-clockwise spin of the other?
    Does the wave collapse back through time to the point they became entangled, which is why the information transfer appears to happen instantly? and does this suggest time (and space) are therefore not what we conventially perceive them to be?

    Following on, if particles become entangled with each other as we move through what we understand as time (so a single particle is entangled with many others over a period of time), hypothetically if we were able to somehow measure the properties of all particles would this somehow collapse our reality into something else. Would 'time' stop because there would then be no uncertainty and is the perception of time is only probability distribution playing out?

    Having seen a few other posts on this site, i have seen some comments get cut down quite harshly. I post this question our of pure interest and if it is total rubbish please say so, but understand i have posted here as i do not know where else to ask the question!

    Many thanks
  2. jcsd
  3. Sep 15, 2015 #2


    User Avatar

    Staff: Mentor

    Quantum mechanics says that if you have two spin-entangled particles (there are other examples of entanglement - I picked that case for definiteness) and you measure the spin of one, then you know what the result of a spin measurement along the same axis on the other will be. That measurement of the other particle may already have been done, it may be done in the future, or it may never be done - but you know what the result will be, when and if it ever happens.

    However, that's all that quantum mechanics says; it does not explain why or how this happens. It just says that measurement results will be correlated so that knowing one allows you to predict the other. It doesn't say that there's a probability wave that collapses (although that is one possible explanation), it doesn't say the wave collapses backwards through time (another possible explanation), and it will neither confirm nor deny that time and space are or are not how we conventionally perceive them.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook