PROCEEDINGS ARTICLE | February 12, 2011
Proc. SPIE. 7948, Advances in Photonics of Quantum Computing, Memory, and Communication IV
KEYWORDS: Mathematical modeling, Ultrafast phenomena, Data modeling, Polarization, Diffusion, Magnetism, Quantum dots, Picosecond phenomena, Optical pumping, Pulsed laser operation
Electron spins in quantum dots under coherent control exhibit a number of novel feedback processes. Here, we
present experimental and theoretical evidence of a feedback process between nuclear spins and a single electron
spin in a single charged InAs quantum dot, controlled by the coherently modified probability of exciting a trion
state. We present a mathematical model describing competition between optical nuclear pumping and nuclear
spin-diffusion inside the quantum dot. The model correctly postdicts the observation of a hysteretic sawtooth
pattern in the free-induction-decay of the single electron spin, hysteresis while scanning a narrow-band laser
through the quantum dot's optical resonance frequency, and non-sinusoidal fringes in the spin echo. Both the
coherent electron-spin rotations, implemented with off-resonant ultrafast laser pulses, and the resonant narrowband
optical pumping for spin initialization interspersed between ultrafast pulses, play a role in the observed
behavior. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse
timing, potentially allowing more complex coherent control operations.
