Entanglement

Tom McCurdy

Can any "particle" become entangled with another particle if it is at the same quantum state?

For example if every particle in two identical human beings were entangled what would be the result?

Also any help beyond those two questions would be great.

chroot

Particles can be entangled no matter what quantum states they were originally in.

There's no way to entangle all the atoms in a human being. All of the interactions between those atoms would destroy any such entanglements.

- Warren

humanino

I think the only way "two" particles can bee entangle, is that they are created together. I put quote between "2" particles, because one is forced to consider them as only one single object before a measurement is proceeded.

At the moment of the measurement, there is a collapse of the wavefunction : considered as a vector, it gets projected onto the direction of the proper value obtained. It is not clear what measurement means here. Mathematically clear. But the physical reality of it is not undestood. The conscience itself might be involved it that step.

In the case of two human beings, appart from the fact that they cannot be "created" together (won't even work for twins ok ), their cannot be significant coeherence between such huge amount of particles.

humanino

What kind of entanglement ar you reffering to ? Like in superfluids for example ?

Consider for example superconductivity. Electron have to form Cooper pairs. One could say the electron got entangled long after their creation. I thought the correct intepretation was that the pairs are entangled !

Tom McCurdy

I wasn't refering to superfluids or anything I actually deem possible I was wondering if somehow two human beings were entangled what would be the consiquences.

humanino

Tom, as Warren explained one cannot entangle human beings ! Macroscopic objects usually suffer from thermal agitation, preventing coherence to last significantly.

I was addressing my question to Warren. He said one can entangle any particles, not necessarilly particles created together. I studied QM a few years ago, and I am now concentrating on my current work. But I remembered my favorite teacher talking about particles :
I concluded from those kind of speech, that one cannot say "There are two electrons in a Cooper pair". This might be only a matter of interpretation. I thought one must take great care when saying there is an electron here or there. In conductors, eletrons have a mass, which is very different from the usual mass in vacuum. Therefore, they should not be called electrons. They are quanta of the field in the conductor.

I thought, when entanglement occurs, the new features of the particles entangled lead one to conclude they are not the original particles. That is, a conversion has occured, new particles have been created.

marlon

humanino, what you are saying is indeed correct but I think the interpretation you give to these things is a bit strange. I take your example of the electron in a conductor. The mass is indeed different as the restmass of an elektron, which is following your statement, the mass in the vacuum. This other mass is called the effective mass and it is defined as follows : the electron in a conductor interacts with the surrounding lattice of positive ions. But one can interpret this situation as if the elektron is actually in the vacuum but with a different mass (this is the effective mass) so that the equations of motion of this electron would still be the same as if it were still in the conductuor. The effective mass thus represents the actual interactions of the electron with the ions of the lattice. But the restmass of an electron is a fundamental property that never changes, only the effective mass can change due to different kind of interactions.

One has an analogue situation in QFT with effective quarkmass. the reason for doing all this is to simplify calculations in perturbation theory and so on.

regards
marlon