The spin of an electron is in many ways the archetypical quantum system. If you measure the spin, it will take one of two values: spin up or spin down. It's a perfect binary, which makes it good for quantum computing systems, as well as in the nascent field of spintronics. However, implementing things based on spin has proven to be far more complicated: single electron spins in atoms interact with the environment so that they forget their original state. Measurement of the spin state brings its own difficulties.
Researchers have now made some progress by manipulating the electronic spin state in a phosphorous atom embedded in silicon. Jarryd J. Pla and colleagues exploited the properties of both atom types to isolate the spin of a single electron in the phosphorous atom. At 0.3 Kelvin (0.3°C above absolute zero) the spin state stayed stable for relatively long amounts of time. While single electron spins are insufficient to build quantum devices, this experiment is a reasonable proof-of-principle, and shows how multi-spin systems could be developed.
The spin of an atom is mostly determined by the electrons that orbit furthest from the nucleus, since they have a higher response to external stimuli (spin states of atomic nuclei are more stable but more difficult to work with, though another experiment made some progress along those lines). As a result, if the atom has the proper electronic configuration, the spin state of an atom is often the same as the spin state of a single electron.
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Article by Matthew Francis (c) Ars Technica - Read full story here.