Ultrafast control of donor-bound electron spins with single detuned optical pulses

The ability to control spins in semiconductors is important in a variety of fields, including spintronics and quantum information processing. Due to the potentially fast dephasing times of spins in the solid state(1-3), spin control operating on the picosecond timescale, or faster, may be necessary. Such speeds-which are not possible to reach with standard electron spin resonance techniques based on microwave sources-can be attained with broadband optical pulses. One promising ultrafast technique uses single broadband pulses detuned from resonance in a three-level Lambda system(4). This technique is robust against optical-pulse imperfections and does not require a fixed optical reference phase. Here we demonstrate, theoretically and experimentally, the principle of coherent manipulation of spins using this approach. Spin rotations with areas exceeding pi/4 for a single pulse and pi/2 for two pulses are achieved for donor-bound electrons. This technique might find applications from basic solid-state electron spin resonance spectroscopy to arbitrary single-qubit rotations(4,5) and bang-bang control(6) for quantum computation.