Experimental demonstration of a resonator-induced phase gate in a multi-qubit circuit QED system

TL;DR

This paper experimentally demonstrates a resonator-induced phase (RIP) gate in a multi-qubit circuit QED system, achieving high-fidelity entangling gates across a wide frequency range and generating a four-qubit GHZ state.

Contribution

The study presents the first experimental realization of the RIP gate with four superconducting qubits in a 3D architecture, including a multi-qubit refocusing scheme and GHZ state generation.

Findings

High-fidelity CZ gates between all qubit pairs

Effective multi-qubit refocusing scheme

Generation of a four-qubit GHZ state

Abstract

The resonator-induced phase (RIP) gate is a multi-qubit entangling gate that allows a high degree of flexibility in qubit frequencies, making it attractive for quantum operations in large-scale architectures. We experimentally realize the RIP gate with four superconducting qubits in a three-dimensional (3D) circuit-quantum electrodynamics architecture, demonstrating high-fidelity controlled-Z (CZ) gates between all possible pairs of qubits from two different 4-qubit devices in pair subspaces. These qubits are arranged within a wide range of frequency detunings, up to as large as 1.8 GHz. We further show a dynamical multi-qubit refocusing scheme in order to isolate out 2-qubit interactions, and combine them to generate a four-qubit Greenberger-Horne-Zeilinger state.