I attended a recent talk by Peter Zoller, who, along with Ignacio Cirac, is a master of quantum control. I especially enjoyed his description of a geometric phase gate which is resistant to temperature fluctuations. These ideas are contained in the article at quant-ph/0411103, written by Zoller and collaborators.
Unfortunately, I don't have time to digest the article right now, but I can say a few words. The thing I found most interesting is the fact that geometric phases can be non-adiabatic. Many people, including myself, are familiar with the concept of Berry's phase which is a geometric phase that arises when the system evolves adiabatically through a closed path in parameter space. For the geometric phase gate that Zoller described, you can design a laser pulse sequence so that you can perform a two-ion gate operation which results in the ions having a fixed relative phase afterwards. The phase is the same no matter what the initial state of the ions. Even better, if the operation is perfect, the temperature of the system doesn't matter eitiher.
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