Double Quantum Dot as a Quantum Bit

Science  30 Sep 2005:
Vol. 309, Issue 5744, pp. 2173-2174
DOI: 10.1126/science.1118921

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Quantum dots are microscopic structures that can trap single electrons for study and manipulation. Such devices are of interest as potential logic elements in a future quantum computer in which electron spins are used as quantum bits. The problem is that the spins on the nuclei of the device material itself can interfere with the electron spins. In his Perspective, DiVincenzo discusses results reported in the same issue by Petta et al. in which a double quantum dot structure was used to avoid the effect of the background spins. By swapping the quantum spin states back and forth between the dots, the researchers were able to greatly increase the quantum coherence time of the stored states. The results show that fully electric (as opposed to magnetic) control of the spin states offers the possibility of using such double dots in a quantum computer.