Picosecond Coherent Optical Manipulation of a Single Electron Spin in a Quantum Dot
J. Berezovsky,*
M. H. Mikkelsen,*
N. G. Stoltz,
L. A. Coldren,
D. D. Awschalom
Most schemes for quantum information processing require fast
single-qubit operations. For spin-based qubits, this involves
performing arbitrary coherent rotations of the spin state on
time scales much faster than the spin coherence time. By applying
off-resonant, picosecond-scale optical pulses, we demonstrated
the coherent rotation of a single electron spin through arbitrary
angles up to

radians. We directly observed this spin manipulation
using time-resolved Kerr rotation spectroscopy and found that
the results are well described by a model that includes the
electronnuclear spin interaction. Measurements of the spin rotation
as a function of laser detuning and intensity confirmed that
the optical Stark effect is the operative mechanism.
Center for Spintronics and Quantum Computation, University of California, Santa Barbara, CA 93106, USA.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: awsch{at}physics.ucsb.edu