Harnessing the GaAs quantum dot nuclear spin bath for quantum control

TL;DR

This paper proposes a theoretical method to control two-electron spin states in GaAs quantum dots using nuclear spins and Landau-Zener-Stückelberg interferometry, achieving fast single-qubit rotations and analyzing coherence properties.

Contribution

It introduces a novel approach for quantum control of spin states via hyperfine interactions and interferometry in GaAs quantum dots, with detailed coherence analysis.

Findings

Achieves ~1 ns single spin rotations using Landau-Zener-Stückelberg interferometry.

Demonstrates that nuclear spins can be used for coherent control of electron spin states.

Finds T_2^* coherence time of approximately 16 ns, matching experimental data.

Abstract

We theoretically demonstrate that nuclear spins can be harnessed to coherently control two-electron spin states in a double quantum dot. Hyperfine interactions lead to an avoided crossing between the spin singlet state and the ms = +1 triplet state, T_+ . We show that a coherent superposition of singlet and triplet states can be achieved using finite-time Landau-Zener-St\"uckelberg interferometry. In this system the coherent rotation rate is set by the Zeeman energy, resulting in ~1 nanosecond single spin rotations. We analyze the coherence of this spin qubit by considering the coupling to the nuclear spin bath and show that T_2^* ~ 16 ns, in good agreement with experimental data. Our analysis further demonstrates that efficient single qubit and two qubit control can be achieved using Landau-Zener-St\"uckelberg interferometry.