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Originally published in Science Express on 10 July 2008
Science 8 August 2008:
Vol. 321. no. 5890, pp. 817 - 821
DOI: 10.1126/science.1159221
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Reports

Suppressing Spin Qubit Dephasing by Nuclear State Preparation

D. J. Reilly,1 J. M. Taylor,2 J. R. Petta,3 C. M. Marcus,1* M. P. Hanson,4 A. C. Gossard4

Coherent spin states in semiconductor quantum dots offer promise as electrically controllable quantum bits (qubits) with scalable fabrication. For few-electron quantum dots made from gallium arsenide (GaAs), fluctuating nuclear spins in the host lattice are the dominant source of spin decoherence. We report a method of preparing the nuclear spin environment that suppresses the relevant component of nuclear spin fluctuations below its equilibrium value by a factor of ~70, extending the inhomogeneous dephasing time for the two-electron spin state beyond 1 microsecond. The nuclear state can be readily prepared by electrical gate manipulation and persists for more than 10 seconds.

1 Department of Physics, Harvard University, Cambridge, MA 02138, USA.
2 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3 Department of Physics, Princeton University, Princeton, NJ 08544, USA.
4 Materials Department, University of California, Santa Barbara, CA 93106, USA.

* To whom correspondence should be addressed. E-mail: marcus{at}harvard.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)