Originally Posted by luvtolean
... the key to both being magnetic fields to accelerate or decelerate the particles.
You are right that it is like the plasma problem. They use them to create a 'bottle' so they can block out thermal noise.
They also use them to polarize the potassiums so they lasers can get at them. The electron's orbital decay has selection rules (can't drop to a lower state by changing more than one unit of total angular momentum at a time, for example, I think that they are called Born's Rules after Max Born, ah well, they are named after someone).
At these temperatures, some of the inner electrons have dropped into mesostable states. That is, they can't drop any lower (stuck in 2p, maybe, to borrow the chemists nomenclature) from where they are, so they use the laser to stimulate them precisely into states that they can decay from to a net lower state. If you've heard of sonic cooling, it's the same principle. Kind of ironic that adding energy eventually results in a net energy loss.
I'll spare you a technical definition of temperature (because I am not sure that I can do it) and just say that as the temperature drops the quantum effects become more pronounced and that can be exploited to drop the temp even lower. When they talk about a billionth of a degree, they are likely down to trying to get ONE proton, neutron, or electron, in a system of 30-40 particles spinning the other way.