High-precision pulse calibration of tunable couplers for high-fidelity two-qubit gates in superconducting quantum processors

Abstract

For superconducting quantum processors, stable high-fidelity two-qubit operations depend on precise flux control of the tunable coupler. However, the pulse distortion poses a significant challenge to the control precision. Current calibration methods, which often rely on microwave crosstalk or additional readout resonators for coupler excitation and readout, tend to be cumbersome and inefficient, especially when couplers only have flux control. Here, we introduce and experimentally validate a novel pulse calibration scheme that exploits the strong coupling between qubits and couplers, eliminating the need for extra coupler readout and excitation. Our method directly measures the short-time and long-time step responses of the coupler flux pulse transient, enabling us to apply predistortion to subsequent signals using fast Fourier transformation and deconvolution. This approach not only simplifies the calibration process but also significantly improves the precision and stability of the flux control. We demonstrate the efficacy of our method through the implementation of diabatic CZ and iSWAP gates with fidelities of $99.61\pm 0.04\%$ and $99.82\pm 0.02\%$, respectively, as well as a series of diabatic CPhase gates with high fidelities characterized by cross-entropy benchmarking. The consistency and robustness of our technique are further validated by the reduction in pulse distortion and phase error observed across multilayer CZ gates. These results underscore the potential of our calibration and predistortion method to enhance the performance of two-qubit gates in superconducting quantum processors.

16 pages, 11 figures, 7 tables

References in corpus (21)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Suppressing quantum errors by scaling a surface code logical qubit
• Process verification of two-qubit quantum gates by randomized benchmarking
• High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler
• Digital simulation of non-Abelian anyons with 68 programmable superconducting qubits
• High fidelity two-qubit gates on fluxoniums using a tunable coupler
• Experimental quantum adversarial learning with programmable superconducting qubits
• Parametric-resonance entangling gates with a tunable coupler
• Quantum simulation of Hawking radiation and curved spacetime with a superconducting on-chip black hole
• Non-Abelian braiding of Fibonacci anyons with a superconducting processor
• Observation of many-body Fock space dynamics in two dimensions
• Realization of High-Fidelity CZ Gate based on a Double-Transmon Coupler
• Creating and controlling global Greenberger-Horne-Zeilinger entanglement on quantum processors
• Realization of high-fidelity CZ gates in extensible superconducting qubits design with a tunable coupler
• Coupler microwave-activated controlled phase gate on fluxonium qubits
• Tunable Coupling Architectures with Capacitively Connecting Pads for Large-Scale Superconducting Multi-Qubit Processors
• ScQ cloud quantum computation for generating Greenberger-Horne-Zeilinger states of up to 10 qubits
• Realization of fast all-microwave CZ gates with a tunable coupler
• One-step implementation of nonadiabatic geometric fSim gate in superconducting circuits
• Purity-Assisted Zero-Noise Extrapolation for Quantum Error Mitigation
• Recovery of damaged information via scrambling in indefinite casual order

Cited by in corpus (7)

• Direct Implementation of High-Fidelity Three-Qubit Gates for Superconducting Processor with Tunable Couplers
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• Scalable quantum simulator with an extended gate set in giant atoms
• Flexible Readout and Unconditional Reset for Superconducting Multi-Qubit Processors with Tunable Purcell Filters
• Microwave-activated high-fidelity three-qubit gate scheme for fixed-frequency superconducting qubits
• Application of Optimal Control to Time-Resolution Protocol for Quantum Sensing
• Control the qubit-qubit coupling with double superconducting resonators