Electrical Interconnects for Silicon Spin Qubits

TL;DR

This paper proposes a resistive topgate-based interconnect for silicon spin qubits, analyzing its potential to maintain spin coherence over long distances despite various decoherence threats.

Contribution

It introduces a novel interconnect design using a resistive topgate and evaluates its effectiveness in preserving spin coherence in silicon spin qubits.

Findings

Spin-orbit coupling is the main decoherence threat.

Motional narrowing due to scattering extends coherence length to ~15 mm.

The proposed interconnect could enable scalable long-range qubit communication.

Abstract

Scalable spin qubit devices will likely require long-range qubit interconnects. We propose to create such an interconnect with a resistive topgate. The topgate is positively biased, to form a channel between the two dots; an end-to-end voltage difference across the nanowire results in an electric field that propels the electron from source dot to target dot. The electron is momentum-incoherent, but not necessarily spin-incoherent; we evaluate threats to spin coherence due to spin-orbit coupling, valley physics, and nuclear spin impurities. We find that spin-orbit coupling is the dominant threat, but momentum-space motional narrowing due to frequent scattering partially protects the electron, resulting in characteristic decoherence lengths ~15 mm for plausible parameters.