Spin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe

TL;DR

This paper demonstrates long-distance spin qubit shuttling in silicon with preserved entanglement, showing potential for scalable quantum computing architectures using conveyor-mode electron transport.

Contribution

It reports the first investigation of spin coherence during conveyor-mode electron shuttling over extended distances in silicon, with significantly increased shuttle velocity and maintained entanglement.

Findings

Spin-qubit dephasing time increases with shuttle distance due to motional narrowing.

Spin-entanglement remains detectable after multiple shuttle loops up to 3.36 μm.

Estimated shuttle infidelity due to dephasing is 0.7% over 560 nm.

Abstract

Long-ranged coherent qubit coupling is a missing function block for scaling up spin qubit based quantum computing solutions. Spin-coherent conveyor-mode electron-shuttling could enable spin quantum-chips with scalable and sparse qubit-architecture. Its key feature is the operation by only few easily tuneable input terminals and compatibility with industrial gate-fabrication. Single electron shuttling in conveyor-mode in a 420 nm long quantum bus has been demonstrated previously. Here we investigate the spin coherence during conveyor-mode shuttling by separation and rejoining an Einstein-Podolsky-Rosen (EPR) spin-pair. Compared to previous work we boost the shuttle velocity by a factor of 10000. We observe a rising spin-qubit dephasing time with the longer shuttle distances due to motional narrowing and estimate the spin-shuttle infidelity due to dephasing to be 0.7 % for a total shuttle distance of nominal 560 nm. Shuttling several loops up to an accumulated distance of 3.36 $\mu$m, spin-entanglement of the EPR pair is still detectable, giving good perspective for our approach of a shuttle-based scalable quantum computing architecture in silicon.