Procedure for systematically tuning up crosstalk in the cross resonance gate

TL;DR

This paper introduces a calibration method for the cross resonance gate that improves its fidelity and reduces gate time in superconducting qubits, achieving over 99% fidelity.

Contribution

It presents a novel calibration procedure and a second microwave drive tone to cancel errors, enhancing the performance of the CR gate.

Findings

Gate fidelity exceeds 99% with shorter gate times

Calibration accurately measures the full CR Hamiltonian

Error terms are identified and mitigated

Abstract

We present improvements in both theoretical understanding and experimental implementation of the cross resonance (CR) gate that have led to shorter two-qubit gate times and interleaved randomized benchmarking fidelities exceeding 99%. The CR gate is an all-microwave two-qubit gate offers that does not require tunability and is therefore well suited to quantum computing architectures based on 2D superconducting qubits. The performance of the gate has previously been hindered by long gate times and fidelities averaging 94-96%. We have developed a calibration procedure that accurately measures the full CR Hamiltonian. The resulting measurements agree with theoretical analysis of the gate and also elucidate the error terms that have previously limited the gate fidelity. The increase in fidelity that we have achieved was accomplished by introducing a second microwave drive tone on the target qubit to cancel unwanted components of the CR Hamiltonian.