Three-dimensional solid-state qubit arrays with long-lived spin coherence

TL;DR

This paper demonstrates the creation of 3D arrays of nitrogen-vacancy center qubits in diamond using laser writing, achieving long spin coherence times suitable for scalable quantum computing, communication, and sensing.

Contribution

It introduces a laser writing method to fabricate 3D NVC qubit arrays with long coherence times, enabling high-density quantum devices in diamond.

Findings

Spin coherence times are an order of magnitude longer than previous laser-written qubits.

The array can contain up to 5 million qubits in a small diamond volume.

The platform is adaptable to other qubits in diamond and silicon carbide.

Abstract

Three-dimensional arrays of silicon transistors increase the density of bits. Solid-state qubits are much larger so could benefit even more from using the third dimension given that useful fault-tolerant quantum computing will require at least 100,000 physical qubits and perhaps one billion. Here we use laser writing to create 3D arrays of nitrogen-vacancy centre (NVC) qubits in diamond. This would allow 5 million qubits inside a commercially available 4.5x4.5x0.5 mm diamond based on five nuclear qubits per NVC and allowing $(10 \mu m)^3$ per NVC to leave room for our laser-written electrical control. The spin coherence times we measure are an order of magnitude longer than previous laser-written qubits and at least as long as non-laser-written NVC. As well as NVC quantum computing, quantum communication and nanoscale sensing could benefit from the same platform. Our approach could also be extended to other qubits in diamond and silicon carbide.