Designing Filter Functions of Frequency-Modulated Pulses for High-Fidelity Two-Qubit Gates in Ion Chains

Abstract

High-fidelity two-qubit gates in quantum computers are often hampered by fluctuating experimental parameters. The effects of time-varying parameter fluctuations lead to coherent noise on the qubits, which can be suppressed by designing control signals with appropriate filter functions. Here, we develop filter functions for Mølmer-Sørensen gates of trapped-ion quantum computers that accurately predict the change in gate error due to small parameter fluctuations at any frequency. We then design the filter functions of frequency-modulated laser pulses, and compare this method with pulses that are robust to static offsets of the motional-mode frequencies. Experimentally, we measure the noise spectrum of the motional modes and use it for designing the filter functions, which improves the gate fidelity from 99.23(7)% to 99.55(7)% in a five-ion chain.

arXiv comment17 pages, 10 figures

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• Supervised learning for robust quantum control in composite-pulse systems
• Individually Addressed Entangling Gates in a Two-Dimensional Ion Crystal
• Angle-robust Two-Qubit Gates in a Linear Ion Crystal
• Efficient motional-mode characterization for high-fidelity trapped-ion quantum computing
• Demonstration of two-dimensional connectivity for a scalable error-corrected ion-trap quantum processor architecture
• Realization and Calibration of Continuously Parameterized Two-Qubit Gates on a Trapped-Ion Quantum Processor
• Pulse optimization for high-precision motional-mode characterization in trapped-ion quantum computers
• Reshaping quantum device noise via repetition code circuits
• Evolutionary reduction of the laser noise impact on quantum gates