Submitted on April 16, 2008
Accepted on July 2, 2008
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. Gossard 4
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.
C. M. Marcus , E-mail: marcus{at}harvard.edu
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 µs. The nuclear state can be readily prepared by electrical gate manipulation and persists for >10 s.
