Dave Bacon explains heating-induced decoherence:
One problem with ion traps qubits has been the heating of the motional degrees of the trapped ions, due mostly to fluctuating potentials on the trap electrodes. The electrode potential goes yee-yaw and the ion goes wee-wah, heating up and thus ruining the motional degree of freedom of the ion.
See, this is why he gets to be Pontiff, and I'm a cardinal at best...
The highly technical use of "yee-yaw" and "wee-wah" is in order to introduce a new paper from Chris Monroe's group in Michigan, who have found that cooling the trap electrodes greatly improves the heating problem. As this heating is one of the major obstacles to quantum computing with trapped ions, this is Very Cool Indeed.
There's a good write-up of the basics here.