When protons enter a micro cavity, they rattle and dance around it for a long, long time. All the while, the walls are vibrating…moving back and forth in a random fashion in the protons reference frame, As they bounce of the walls, the walls give and take energy away on each bounce. So when the protons encounter each other, they never have the same quantum mechanical properties.
It’s like spinning the roulette wheel, the result is a randomization of the proton collision process in terms of kinetic energy and other things. Out of the trillions of such proton encounters and near approaches, one collision will eventually see in the fullness of time two protons with identical properties. In the off chance that will most always occur given a very large number of encounters, the two protons will eventually stick together to form a cooper pair. See the “The cooper pair dance”. To be quantum mechanically accurate, the dancers should be bouncing off the moving walls of the room…just use your imaginations on this point. http://www.youtube.com/watch?v=7kVVacwz2ng
