Voltage-Selective Bi-directional Polarization and Coherent Rotation of Nuclear Spins in Quantum Dots

TL;DR

This paper demonstrates voltage-controlled, bidirectional nuclear spin polarization in GaAs quantum dots, with coherent control via NMR, revealing long-lived quantum states suitable for quantum memory applications.

Contribution

It introduces a method to selectively polarize nuclear spins in quantum dots using voltage adjustments and demonstrates coherent control with NMR, advancing quantum information processing.

Findings

Nuclear spins can be polarized in two opposite directions using voltage.

Nuclear spins exhibit a coherence time of up to 1 ms.

Nuclear spins are promising for quantum memory applications.

Abstract

We proposed and demonstrated that the nuclear spins of the host lattice in GaAs double quantum dots can be strongly polarized in either of two opposite directions, parallel or antiparallel to an external magnetic field. The direction is selected simply by adjusting the dc source-drain voltage of the device. This nuclear polarization manifests itself by repeated controlled electron-nuclear spin scattering in the Pauli spin blockade state. Polarized nuclei are also controlled coherently by means of nuclear magnetic resonance (NMR). This work confirmed that the nuclear spins in quantum dots are indeed long-lived quantum states with a coherence time of up to 1 ms, and may be a promising resource for quantum information processing such as quantum memories for electron spin qubits.