Microwave-activated conditional-phase gate for superconducting qubits

TL;DR

This paper presents a new microwave-activated conditional-phase gate for superconducting qubits that offers all-microwave control, reduced crosstalk, and high fidelity, advancing quantum computing capabilities.

Contribution

The authors introduce a novel microwave-activated entangling gate leveraging fixed-frequency qubits and a resonator bus, with explicit design of higher energy state interactions.

Findings

Achieved a gate fidelity of 87% via quantum process tomography.

Demonstrated all-microwave control with appreciable qubit separation.

Enabled a conditional-phase gate activated by microwave drive.

Abstract

We introduce a new entangling gate between two fixed-frequency qubits statically coupled via a microwave resonator bus which combines the following desirable qualities: all-microwave control, appreciable qubit separation for reduction of crosstalk and leakage errors, and the ability to function as a two-qubit conditional-phase gate. A fixed, always-on interaction is explicitly designed between higher energy (non-computational) states of two transmon qubits, and then a conditional-phase gate is `activated' on the otherwise unperturbed qubit subspace via a microwave drive. We implement this microwave-activated conditional-phase gate with a fidelity from quantum process tomography of 87%.