Quantum Information Processing, Vol. 3, Nos. 1–5, October 2004 (© 2004)
The Road to a Silicon Quantum Computer
J. R. Tucker
and T.-C. Shen
Received February 2, 2004; accepted March 5, 2004
We discuss prospects for building a silicon-based quantum computer with phos-
phorous donor qubits. A speciﬁc architecture is proposed for initial demonstra-
tions; and the advantages and difﬁculties of this approach are described along
with a plan for systematic development and calibration of the individual
KEY WORDS: Qubits; quantum computer; phosphorous donors; STM lithog-
PACS: 73.21.-b; 73.23.Hk; 81.16.-c; 85.35.-p; 85.40.Ry.
Phosphorous donors in silicon present a unique opportunity for solid-state
Electrons spins on isolated Si:P donors have very
long decoherence times of ∼60 ms in isotopically puriﬁed
Si at 7 K.
By contrast, electron spin dephasing times in GaAs are orders-of-magni-
tude shorter due spin–orbit interaction; and the background nuclear spins
of the III–V host lattice cannot be eliminated by isotope selection. Finally,
the Si:P donor is a self-conﬁned, perfectly uniform single-electron quan-
tum dot with a non-degenerate ground state. A strong Coulomb potential
breaks the 6-valley degeneracy of the silicon conduction band near the
donor site, yielding a substantial energy gap of ∼15 meV to the lowest
as required for quantum computation.
Department of Electrical and Computer Engineering, University of Illinois, Urbana-Cham-
paign, 1406 West Green Street, Urbana, Illinois 61801. E-mail: firstname.lastname@example.org
Department of Physics, Utah State University, Logan, Utah 84322. E-mail: tcshen@
To whom correspondence should be addressed.
1570-0755/04/1000-0105/0 © 2004 Springer Science+Business Media, Inc.