We report the observation of a feedback process between the nuclear spins in a single charged quantum dot and its trion transition, driven by a periodic sequence of optical pulses. The pulse sequence intersperses off-resonant ultrafast pulses for coherent electron-spin rotation and resonant narrow-band optical pumping. The feedback manifests as a hysteretic triangle-like pattern in the free-induction-decay of the single spin. We present a simple, quasi-analytic numerical model to describe this observation, indicating that the feedback process results from the countering effects of optical nuclear pumping and nuclear spin-diffusion inside the quantum dot. 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.
@article{arxiv.0912.5401,
title = {Pulsed Nuclear Pumping and Spin Diffusion in a Single Charged Quantum Dot},
author = {Thaddeus D. Ladd and David Press and Kristiaan De Greve and Peter L. McMahon and Benedikt Friess and Christian Schneider and Martin Kamp and Sven Hoefling and Alfred Forchel and Yoshihisa Yamamoto},
journal= {arXiv preprint arXiv:0912.5401},
year = {2013}
}