Quantum Information Processing, Vol. 6, No. 2, April 2007 (© 2006)
A Nuclear Spin Valve: Towards the Read-out of Single
Nuclear Spin Qubits
and D. G. Cory
Received April 18, 2006; accepted August 21, 2006; Published online December 12, 2006
We propose a scheme to read out qubits deﬁned in single nuclear spins—address-
ing one of the main obstacles on the way to a solid state NMR quantum com-
puter. It is based on a “spin valve” between bulk nuclear spin systems that is
highly sensitive to the state of the qubit spin. We suggest a concrete realization of
that detector in a Si lattice and show that it can be operated over a broad range
of experimental parameters. Transport of spin through the proposed spin valve is
analogous to that of charge through an electronic nanostructure, but exhibits dis-
tinctive new features.
KEY WORDS: solid-state nuclear spin qubit; read-out; single-spin detection;
spin transport; spin valve.
PACS: 03.67.Lx; 75.45.+j; 76.60.-k.
Nuclear magnetic resonance (NMR) experiments have been a valuable
testbed for quantum information processing (QIP)
and they still pro-
vide the largest collections of coupled qubits available at present.
NMR QIP experiments are performed on liquids and suffer from the lack
of scalability. Solid state spin systems have been proposed as a promising
route to scalability in NMR QIP.
Their experimental implementation
is, however, challenging. One major obstacle that has to be overcome is
the read out problem. It requires the measurement of the quantum state
of a single nuclear spin. Experiments that have successfully detected sin-
gle spin resonances are promising.
Recently the read out of a sin-
gle electron spin has been reported.
The measurement of the state of
Department of Physics, Massachusetts Institute of Technology, Cambridge MA 02139,
Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge
MA 02139, USA.
To whom correspondence should be addressed. E-mail: Markus.firstname.lastname@example.org.
1570-0755/07/0400-0127/0 © 2006 Springer Science+Business Media, LLC