Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs

TL;DR

This study investigates how quadrupolar interactions and anisotropic g-tensors influence electron spin dephasing in GaAs quantum dots, revealing conditions that can mitigate decoherence for quantum computing applications.

Contribution

It demonstrates experimentally that quadrupolar broadening can reduce electron spin coherence and identifies field directions that eliminate this effect, advancing understanding of spin dephasing mechanisms.

Findings

Quadrupolar broadening can accelerate electron spin decoherence.

Proper field orientation can eliminate quadrupolar effects on coherence.

Anisotropic g-tensor modulates spin coherence behavior.

Abstract

Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using electron spins as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics. One might thus expect them to enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession can also reduce electron spin coherence due to faster decorrelation of transverse nuclear fields. However, this effect can be eliminated for appropriate field directions. Furthermore, we observe an additional modulation of spin coherence that can be attributed to an anisotropic electronic $g$-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in related systems such as self-assembled quantum dots and III-V nanowires.