A Coherent Beam Splitter for Electronic Spin States

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Science  05 Feb 2010:
Vol. 327, Issue 5966, pp. 669-672
DOI: 10.1126/science.1183628

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Rapid coherent control of electron spin states is required for implementation of a spin-based quantum processor. We demonstrated coherent control of electronic spin states in a double quantum dot by sweeping an initially prepared spin-singlet state through a singlet-triplet anticrossing in the energy-level spectrum. The anticrossing serves as a beam splitter for the incoming spin-singlet state. When performed within the spin-dephasing time, consecutive crossings through the beam splitter result in coherent quantum oscillations between the singlet state and a triplet state. The all-electrical method for quantum control relies on electron–nuclear spin coupling and drives single-electron spin rotations on nanosecond time scales.

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