High-fidelity, high-scalability two-qubit gate scheme for superconducting qubits

TL;DR

This paper presents a new superconducting two-qubit gate scheme using fixed-frequency qubits and a tunable coupler, achieving high fidelity and scalability for quantum computing.

Contribution

The authors experimentally demonstrate a low-control, high-fidelity controlled-Z gate scheme that simplifies calibration and reduces crosstalk in superconducting circuits.

Findings

Achieved a 30ns controlled-Z gate with 99.5% fidelity.

Gate errors are primarily limited by coherence times.

Scheme requires fewer control lines and simplifies calibration.

Abstract

High-quality two-qubit gate operations are crucial for scalable quantum information processing. Often, the gate fidelity is compromised when the system becomes more integrated. Therefore, a low-error-rate, easy-to-scale two-qubit gate scheme is highly desirable. Here, we experimentally demonstrate a new two-qubit gate scheme that exploits fixed-frequency qubits and a tunable coupler in a superconducting quantum circuit. The scheme requires less control lines, reduces crosstalk effect, simplifies calibration procedures, yet produces a controlled-Z gate in 30ns with a high fidelity of 99.5%, derived from the interleaved randomized benchmarking method. Error analysis shows that gate errors are mostly coherence limited. Our demonstration paves the way for large-scale implementation of high-fidelity quantum operations.