Abstract:

The spin of an electron confined in a semiconductor quantum dot is very well isolated from the environment. That is why it is a perspective candidate for the realization of a quantum bit. The dominant source of environmental noise for such a qubit is its interaction with the nuclear spins of surrounding atoms. It will be shown how the spin-spin interaction results in: 1. the relaxation (of the electron spin), that is the loss of memory about the initial electron energy, and 2. the decoherence, that is the loss of memory about the initial phase. Recent experiments will be discussed, which demonstrate that some part (99.9%) of the "decoherence" is revertible (and this part is called dephasing). The reason for this is a very long phase coherence of the environment itself.
 
 
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