# What is meant by when we say more than two (say 4) particles are entangled [closed]

I understand the entanglement of a pair of particles which known to show three kinds of correlation - (consider the property entangled is spin)

1. Anti correlation - when two particles are measured in same angle They always have opposite outcome.

2. Statistical correlation of SQUARE of sin((A-B)/2) when two particles are measured at angles A and B.

3. Statistical correlation of 50/50 when one particle is measured numerous times at any specific angle.

How is entanglement of say 4 particle, described in terms of correlations? Can an odd number of particles get entangled too, or it has to be always an even number?

I know about mathematical superposition. What I am looking for is can it be described in terms of correlations in a similar way as the pair entanglement is described above?, or it is too complex to describe it like that and must use mathematical equations to even describe what the measurement results are going to look like.

• There are entangled states with the statistics you describe. There are other entangled states (for two particles) with other statistics. If you want to know the statistics associated with a three or four particle state, you have to first specify which state you're talking about. Jul 30, 2016 at 22:33
• based on your response, I'd say the first thing you have to do is learn what a quantum state is. Jul 30, 2016 at 23:07
• @WillO: OK, I agree spin is a property, not a state. Irrespective of that, can the 4 particle entanglement be described in terms of statistics in a similar way a pair entanglement is?
– kpv
Jul 30, 2016 at 23:14
• yes more than 2 entities might be entangled. Zeilinger published about 3, Einstein about billions ( B-E condensates ). Pairs are interesting because it is easiest to highlight the entanglement, the difference with the classical statistic being maximum
– user46925
Jul 30, 2016 at 23:40
• @kpv: You ask if a 4 particle entanglement can be described in terms of statistics in a similar way to a pair entanglement: Answer: Of course the state cannot be described in terms of statistics, for either a four particle state OR a two particle state. You can derive the statistics from the state, but the state contains more information than just those statistics. Jul 31, 2016 at 3:36