ndom interactions with the environment that destroy fragile quantum superposition states, and wreck the operation of the computer. In the ion trap system, the main source of decoherence is heating of the ions in the trap– if you cool all the ions in a trap down to the not-moving state, and hold them for a while, after some time, they start moving. Since this motion is your “data bus,” this is a killer.
Finding the source of this heating has been a long and tedious process. As I understand it, the current thinking is that it’s due to random areas of extra charge on the electrodes making up the trap, which push the ions in different directions.
A lot of hard work has gone into nailing this problem down, and it looks like they finally have a handle on it. The last decoherence rates I remember seeing were still a little too high to do practical quantum computing, but they’ve made great strides, and the future looks promising.
Summary: As I said at the beginning of this, ion traps are the most established of the candidate technologies, and probably the farthest along by most measures. The Wineland group in particular has been working on this stuff for better than twenty years, and they’ve got a lot of the bugs worked out, or at least identified.
They’re not ready to make an ion-based quantum computer yet, and the complexity needed for a large system might mean that it never will be the basis for a practical computer. Ion traps are the best test and demonstration system we have at the moment, and they’re likely to remain so for the forseeable future.
If they were running for President, they would be: Joe Biden. They’ve been around forever, and are a central part of the quantum computing establishment. They may not be the most exciting candidate out there, but nobody doubts that they could get the job done.
(We are currently in the middle of a fundraiser for the educational charity DonorsChoose. My challenge goal works out to about $3 per daily visitor. If you feel that you have gotten $3 worth of entertainment or infor