Experimental Demonstration of a Resonator-Induced Phase Gate in a Multiqubit Circuit-QED System

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Quantum Information Science

Background:

• The resonator-induced phase (RIP) gate is a versatile microwave-activated multiqubit entangling gate.
• Its flexibility in qubit frequencies is crucial for scalable quantum computing architectures.

Purpose of the Study:

• To experimentally realize the RIP gate with four superconducting qubits.
• To demonstrate high-fidelity two-qubit gates within a large frequency detuning range.
• To generate a four-qubit Greenberger-Horne-Zeilinger state.

Main Methods:

• Implementation of the RIP gate in a three-dimensional circuit-Quantum Electrodynamics (circuit-QED) architecture.
• Utilizing four superconducting qubits with frequency detunings up to 1.8 GHz.
• Employing a dynamical multiqubit refocusing scheme to isolate two-qubit interactions.

Main Results:

• Achieved high-fidelity controlled-Z (CZ) gates between all qubit pairs in distinct 4-qubit devices.
• Demonstrated successful generation of a four-qubit Greenberger-Horne-Zeilinger state.
• Validated the RIP gate's effectiveness across a broad range of qubit frequency detunings.

Conclusions:

• The resonator-induced phase gate is a viable and high-fidelity method for multiqubit entanglement in superconducting circuits.
• This technique supports large frequency detunings, enhancing scalability for quantum processors.
• The demonstrated ability to generate complex quantum states paves the way for advanced quantum algorithms.