Hamiltonian Phase Error in Resonantly Driven CNOT Gate Above the Fault-Tolerant Threshold

TL;DR

This paper presents a calibration method for high-fidelity controlled-rotation gates in silicon quantum processors, effectively reducing phase errors and achieving operation above the fault-tolerance threshold for quantum error correction.

Contribution

It introduces a simple calibration procedure to measure and correct coherent phase errors, enhancing gate fidelity in silicon quantum computing.

Findings

Gate fidelity improved after phase error correction

Randomized benchmarking confirms fidelity enhancement

Virtual controlled-phase gate achieved with high fidelity

Abstract

Because of their long coherence time and compatibility with industrial foundry processes, electron spin qubits are a promising platform for scalable quantum processors. A full-fledged quantum computer will need quantum error correction, which requires high-fidelity quantum gates. Analyzing and mitigating the gate errors are useful to improve the gate fidelity. Here, we demonstrate a simple yet reliable calibration procedure for a high-fidelity controlled-rotation gate in an exchange-always-on Silicon quantum processor allowing operation above the fault-tolerance threshold of quantum error correction. We find that the fidelity of our uncalibrated controlled-rotation gate is limited by coherent errors in the form of controlled-phases and present a method to measure and correct these phase errors. We then verify the improvement in our gate fidelities by randomized benchmark and gate-set tomography protocols. Finally, we use our phase correction protocol to implement a virtual, high-fidelity controlled-phase gate.