Implementation of Conditional Phase Gates Based on Tunable ZZ Interactions

Area of Science:

• Quantum computing
• Superconducting circuits
• Quantum information processing

Background:

• High-fidelity two-qubit gates are critical for gate-based quantum computing.
• Existing methods often rely on specific resonant interactions or frequency tunability.

Purpose of the Study:

• To present an alternative approach for high-fidelity two-qubit gates using a tunable ZZ interaction.
• To demonstrate a rapid, low-leakage conditional phase (CZ) gate with high fidelity.

Main Methods:

• Utilized a flux-tunable coupler to realize a tunable cross-Kerr-type ZZ interaction between two superconducting qubits.
• Controlled the ZZ-coupling rate over three orders of magnitude.
• Performed interleaved randomized benchmarking to measure gate fidelity and leakage.

Main Results:

• Achieved a rapid (38 ns) conditional phase (CZ) gate with high contrast and low leakage (0.14±0.24%).
• Demonstrated a high gate fidelity of 97.9±0.7% without relying on resonant interactions.
• Showcased the ability to access the entire conditional phase gate family by adjusting a single control parameter.

Conclusions:

• The tunable ZZ interaction provides an effective method for implementing high-fidelity two-qubit gates in superconducting circuits.
• This approach offers advantages in speed, fidelity, and control flexibility for quantum information processing.
• The demonstrated technique simplifies the control of conditional phase gates, paving the way for more complex quantum operations.