Dynamic Nuclear Polarization with Single Electron Spins

TL;DR

This paper demonstrates a method to polarize nuclear spins in a GaAs double quantum dot by controlling electron spin states with pulsed gates, achieving significant Overhauser fields through hyperfine interactions.

Contribution

It introduces a pulse sequence technique to control and set nuclear polarization levels in quantum dots, advancing spin-based quantum information processing.

Findings

Achieved nuclear polarization with Overhauser field up to 80 mT.

Developed a self-limiting pulse sequence for steady-state polarization.

Model agrees with experimental hyperfine-driven spin dynamics.

Abstract

We polarize nuclear spins in a GaAs double quantum dot by controlling two-electron spin states near the anti-crossing of the singlet (S) and m_S=+1 triplet (T+) using pulsed gates. An initialized S state is cyclically brought into resonance with the T+ state, where hyperfine fields drive rapid rotations between S and T+, 'flipping' an electron spin and 'flopping' a nuclear spin. The resulting Overhauser field approaches 80 mT, in agreement with a simple rate-equation model. A self-limiting pulse sequence is developed that allows the steady-state nuclear polarization to be set using a gate voltage.