Can three particles be entangled?

[caspeerrr]

Homework Statement

I'm trying to understand the information paradox at a black hole. Can three particles be entangled? I read on a site that it's impossible to entangle multiple particles. When searching on google I found out that it is possible for multiple particles to entangle. So what

Homework Equations

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The Attempt at a Solution

I read on a site that it's impossible to entangle multiple particles. When searching on google I found out that it is possible for multiple particles to entangle. So is it or is it not possible for multiple particles to entangle and what are the concequences?
Thanks!

 

[mfb]

It is possible to entangle multiple particles, without limitation on their number. I don't know what you read where, it could have been related to the no-cloning theorem.

 

[Strilanc]

I read on a site that it's impossible to entangle multiple particles.

You probably just misunderstood someone talking about monogamy of entanglement. If A is maximally entangled with B (i.e. they form an EPR pair) then neither can also be maximally entangled with C.

There are of course entangled states involving arbitrarily many particles, such as the GHZ state $\frac{1}{\sqrt 2}|000...0\rangle + \frac{1}{\sqrt 2}|111...1\rangle$ or the W state $\frac{1}{\sqrt n}|100..0\rangle+ \frac{1}{\sqrt n}|010..0\rangle + \frac{1}{\sqrt n}|001..0\rangle + ... + \frac{1}{\sqrt n}|000..1\rangle$, it's just that such states don't contain particles that are maximally entangled with each other.