28 research outputs found
Fictitious Magnetic Resonance by Quasi-Electrostatic Field
We propose a new kind of spin manipulation method using a {\it fictitious}
magnetic field generated by a quasi-electrostatic field. The method can be
applicable to every atom with electron spins and has distinct advantages of
small photon scattering rate and local addressability. By using a
laser as a quasi-electrostatic field, we have experimentally demonstrated the
proposed method by observing the Rabi-oscillation of the ground state hyperfine
spin F=1 of the cold atoms and the Bose-Einstein condensate.Comment: 5 pages, 5 figure
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 or faster timescale may be necessary. Such
speeds, which are not possible to attain with standard electron spin resonance
(ESR) techniques based on microwave sources, can be attained with broadband
optical pulses. One promising ultrafast technique utilizes single broadband
pulses detuned from resonance in a three-level Lambda system [4]. This
attractive technique is robust against optical pulse imperfections and does not
require a fixed optical reference phase. Here we demonstrate the principle of
coherent manipulation of spins theoretically and experimentally. Using this
technique, donor-bound electron spin rotations with single-pulse areas
exceeding pi/4 and two-pulses areas exceeding pi/2 are demonstrated. We believe
the maximum pulse areas attained do not reflect a fundamental limit of the
technique and larger pulse areas could be achieved in other material systems.
This technique has applications from basic solid-state ESR spectroscopy to
arbitrary single-qubit rotations [4, 5] and bang-bang control[6] for quantum
computation.Comment: 15 pages, 4 figures, submitted 12/2008. Since the submission of this
work we have become aware of related work: J. Berezovsky, M. H. Mikkelsen, N.
G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 320: 349-352 (2008
THz commensurate echoes: Periodic rephasing of molecular transitions in free-induction decay
We report the first study of coherent transients excited by ultrafast pulses of THz radiation. Using a newly developed optoelectronic source of well-collimated beams of subpicosecond pulses of THz radiation to excite N2O vapor, we have observed the subsequent emission from the vapor of coherent THz pulse trains extending to as long as 1 nsec. The origin of these subpicosecond THz pulses (echoes) is a periodic rephasing, during the free-induction decay, of the more than fifty coherently excited rotational lines with commensurate transition frequencies. From the decay and reshaping of the echoes the coherent relaxation time T2 and the anharmonicity factor for the N2O molecule are evaluated.Peer reviewedElectrical and Computer Engineerin