Recently, the press has been reporting on how NIST researchers used the NMR (a.k.a. MRI) technique of Spin Echo to decrease the decoherence rate of an array of hundreds of ultracold beryllium ions.
If you are interested in the physics of quantum computer hardware, and are a beginner in this area, I recommend that you familiarize yourself with the rudiments of NMR – stuff like and time constants. These are nicely explained, for example, in Wikipedia, the fountain of all Knowledge, under Relaxation_(NMR). Check out also this link, which leads to Chapter 2 of a book entitled “All you really need to know About MRI Physics”. The full book is sold at the delightful website of “Simply Physics – the home of MRI Physics put simply”.