Coherent shuttle of electron-spin states

TL;DR

This paper demonstrates a coherent method to shuttle electron-spin states across a quadruple quantum dot array, revealing oscillations between singlet and triplet states influenced by local magnetic fields, with implications for quantum information transfer.

Contribution

It introduces a technique for coherent electron-spin shuttling in a quadruple quantum dot, analyzing the dynamics and conditions for maintaining spin coherence during transport.

Findings

Observation of periodic singlet-triplet oscillations during electron shuttling.

Dephasing caused by nuclear spin noise affects spin coherence.

Numerical simulations link oscillation visibility to tunnel coupling and pulse rise time.

Abstract

We demonstrate a coherent spin shuttle through a GaAs/AlGaAs quadruple-quantum-dot array. Starting with two electrons in a spin-singlet state in the first dot, we shuttle one electron over to either the second, third or fourth dot. We observe that the separated spin-singlet evolves periodically into the $m=0$ spin-triplet and back before it dephases due to nuclear spin noise. We attribute the time evolution to differences in the local Zeeman splitting between the respective dots. With the help of numerical simulations, we analyse and discuss the visibility of the singlet-triplet oscillations and connect it to the requirements for coherent spin shuttling in terms of the inter-dot tunnel coupling strength and rise time of the pulses. The distribution of entangled spin pairs through tunnel coupled structures may be of great utility for connecting distant qubit registers on a chip.