# Simultaneous measurement of entanglement

1. Aug 14, 2013

### QuestionMarks

Im not sure if there are any implications to be made, but it struck me as interesting as what would happen if measurements of the same parameter were simultaneously made on each of two entangled particles? Can any one speak to this perchance?

2. Aug 14, 2013

### StevieTNZ

Do you mean simultaneous measurement of, for example, polarisation of both photons? QM results will show, is my answer.

3. Aug 15, 2013

### QuestionMarks

4. Aug 15, 2013

### StevieTNZ

The predictions of Quantum Mechanics will be verified.

5. Aug 15, 2013

### tom.stoer

If you have an entangled state with spin total spin S = 0 and individual spins s = +1, -1

$|S=0\rangle = |+\rangle\otimes|-\rangle + |-\rangle\otimes|+\rangle$

then measurements of spin on particle 1 (the first ket) and on particle 2 (the second ket) will always result in opposite directions of spin [regardless of the axis defining the spin of the kets and regardless of the axis used in the experiment]. This result does neither depend on the locations nor the times where and when the two experiments for particle 1 and 2 are performed.

6. Aug 15, 2013

### QuestionMarks

I would expect this inititally, but I should have elaborated that I was trying to get a question of exclusivity: for instance, as such of using a filter. It would, in my mind, nigh force a contradiction.

7. Aug 15, 2013

### tom.stoer

8. Aug 15, 2013

### atyy

9. Aug 15, 2013

### StevieTNZ

Your question and responses are very unclear.

Is there anyway you can elaborate further on what exactly your question is, and what responses you'd like?

I'm more than happy to answer to the best of my knowledge if I can comprehend your question.

Filters? Do you mean polarisers? Wave plates? After a system (e.g. electron or photon) is detected by an apparatus, there isn't much filtering of the system that can be done. Only prior.

Last edited: Aug 15, 2013