Exchange Control of Nuclear Spin Diffusion in a Double Quantum Dot

TL;DR

This paper demonstrates experimental control over nuclear spin relaxation in a GaAs double quantum dot, showing how electron exchange influences nuclear spin diffusion, which could enhance quantum information storage.

Contribution

It introduces a method to manipulate nuclear spin relaxation via gate-controlled electron exchange in a double quantum dot, advancing quantum control techniques.

Findings

Nuclear polarization relaxes on a seconds timescale.

Nuclear relaxation depends on magnetic field and electron exchange.

Electron-mediated nuclear spin diffusion is confirmed by the model.

Abstract

Coherent two-level systems, or qubits, based on electron spins in GaAs quantum dots are strongly coupled to the nuclear spins of the host lattice via the hyperfine interaction. Realizing nuclear spin control would likely improve electron spin coherence and potentially enable the nuclear environment to be harnessed for the long-term storage of quantum information. Toward this goal, we report experimental control of the relaxation of nuclear spin polarization in a gate-defined two-electron GaAs double quantum dot. A cyclic gate-pulse sequence transfers the spin of an electron pair to the host nuclear system, establishing a local nuclear polarization that relaxes on a time scale of seconds. We find nuclear relaxation depends on magnetic field and gate-controlled two-electron exchange, consistent with a model of electron mediated nuclear spin diffusion.