6 research outputs found
Ultrafast optical rotations of electron spins in quantum dots
Coherent manipulation of quantum bits (qubits) on time scales much shorter
than the coherence time is a key prerequisite for quantum information
processing. Electron spins in quantum dots (QDs) are particularly attractive
for implementations of qubits. Efficient optical methods for initialization and
readout of spins have been developed in recent years. Spin coherence times in
the microsecond range have been demonstrated, so that spin control by
picosecond optical pulses would be highly desirable. Then a large number of
spin rotations could be performed while coherence is maintained. A major
remaining challenge is demonstration of such rotations with high fidelity. Here
we use an ensemble of QD electron spins focused into a small number of
precession modes about a magnetic field by periodic optical pumping. We
demonstrate ultrafast optical rotations of spins about arbitrary axes on a
picosecond time scale using laser pulses as control fields.Comment: 10 pages, 4 figure