# Particle/Anti-Particle question

1. Sep 19, 2005

### mgiddy911

Can a particle say an electron, be entangled with its antt-particle partner, a positron?
So could this happen for any particle antiparticle pair? I know that entanglement is often talked abut pertaining to photons, so could a photon and anti-photon be entangled?

2. Sep 19, 2005

### mathman

There is no distinction between photons and antiphotons, i.e. they are they same.

3. Sep 19, 2005

### BenLillie

Yes, you certainly can entangle a particle/anti-particle pair. I don't know if this has ever been done with electrons (and, as mathman said, it's not a relevant question for photons), but take a look at the description of the BaBar and Belle experiments. Their measurements depend on entangling pairs of $$B^0/ \bar B^0$$ mesons. It's a very cool example of something that was once a novel result (EPR correlations, i.e. enganglement) becoming a tool for measureing something else (in this case, CP violation).

4. Sep 19, 2005

### kublai

How do you keep the partical/antiparticle from annihilating before entanglement? How could they be entangled after annihlation, the annihilation products could be different for each partical?

5. Sep 19, 2005

### mgiddy911

Thanks for the information, the reason for me asking in the first place was similar to the last poster's question about anihilation. If the entangled pair were to anihilate after entanglement would anything be different from a normal anihilation?
Sorry about my spelling

6. Sep 19, 2005

### BenLillie

Nothing prevents them from annihilating. In fact, the way you entangle them in the first place is by producing them in pairs from collisions or decays of other particles (sort of reverse annihilation), and they then fly apart. If you like, that's what keeping them from annihilating, the fact that they are produced with high velocities travelling in opposite directions.