Low dephasing and robust micromagnet designs for silicon spin qubits

TL;DR

This paper presents a novel micromagnet design that significantly reduces qubit dephasing in silicon spin qubits, enabling longer coherence times and robust operation for scalable quantum computing.

Contribution

The authors introduce an optimized micromagnet design that minimizes magnetic field gradient-induced dephasing while maintaining fast control, improving coherence times by up to three orders of magnitude.

Findings

Dephasing rates reduced by up to 1000 times compared to previous designs.

The design is robust against fabrication errors.

Compatible with various silicon qubit geometries.

Abstract

Using micromagnets to enable electron spin manipulation in silicon qubits has emerged as a very popular method, enabling single-qubit gate fidelities larger than 99:9%. However, these micromagnets also apply stray magnetic field gradients onto the qubits, making the spin states susceptible to electric field noise and limiting their coherence times. We describe here a magnet design that minimizes qubit dephasing, while allowing for fast qubit control and addressability. Specifically, we design and optimize magnet dimensions and position relative to the quantum dots, minimizing dephasing from magnetic field gradients. The micromagnet-induced dephasing rates with this design are up to 3-orders of magnitude lower than state-of-the-art implementations, allowing for long coherence times. This design is robust against fabrication errors, and can be combined with a wide variety of silicon qubit device geometries, thereby allowing exploration of coherence limiting factors and novel upscaling approaches.