Dephasing and error dynamics affecting a singlet-triplet qubit during coherent spin shuttling

TL;DR

This paper investigates how dephasing and error mechanisms affect the fidelity of a singlet-triplet qubit during repeated coherent spin shuttling in silicon quantum dots, providing insights for scalable quantum information transfer.

Contribution

It characterizes the decay dynamics and error rates of spin shuttling over many operations, highlighting dominant error sources and estimating low shuttle error rates.

Findings

Dephasing dominates for fewer than 1000 shuttles.

Incoherent errors become significant beyond 1000 shuttles.

Shuttle error rates are below 10^-4 up to 1000 shuttles.

Abstract

Quantum information transport over micron to millimeter scale distances is critical for the operation of practical quantum processors based on spin qubits. One method of achieving a long-range interaction is by coherent electron spin shuttling through an array of silicon quantum dots. In order to execute many shuttling operations with high fidelity, it is essential to understand the dynamics of qubit dephasing and relaxation during the shuttling process in order to mitigate them. However, errors arising after many repeated shuttles are not yet well documented. Here, we probe decay dynamics contributing to dephasing and relaxation of a singlet-triplet qubit during coherent spin shuttling over many $N$ repeated shuttle operations. We find that losses are dominated by magnetic dephasing for small $N<10^3$ and by incoherent shuttle errors for large $N>10^3$. Additionally, we estimate shuttle error rates below $1\times10^{-4}$ out to at least $N=10^3$, representing an encouraging figure for future implementations of spin shuttling to entangle distant qubits.