An addressable quantum dot qubit with fault-tolerant control fidelity

TL;DR

This paper demonstrates a silicon-based quantum dot qubit with high control fidelity and significantly improved coherence times, combining advantages of spin qubits and lithographic quantum dots for scalable quantum computing.

Contribution

It introduces a gate-addressable silicon quantum dot qubit with 99.6% control fidelity and enhanced coherence times, suitable for fault-tolerant quantum computing.

Findings

Control fidelity of 99.6% via randomized benchmarking

Coherence times T2* = 120 μs and T2 = 28 ms

Ability to Stark shift ESR frequency by over 3000 times the linewidth

Abstract

Exciting progress towards spin-based quantum computing has recently been made with qubits realized using nitrogen-vacancy (N-V) centers in diamond and phosphorus atoms in silicon, including the demonstration of long coherence times made possible by the presence of spin-free isotopes of carbon and silicon. However, despite promising single-atom nanotechnologies, there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered, but strong coupling to noise has severely limited their dephasing times and control fidelities. Here we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford based randomized benchmarking and consistent with that required for fault-tolerant quantum computing. This qubit has orders of magnitude improved coherence times compared with other quantum dot qubits, with T_2* = 120 mus and T_2 = 28 ms. By gate-voltage tuning of the electron g*-factor, we can Stark shift the electron spin resonance (ESR) frequency by more than 3000 times the 2.4 kHz ESR linewidth, providing a direct path to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies.