Real-time flux correction boosts superconducting quantum gate accuracy
Precision and resource scaling of real-time flux distortion compensation for superconducting quantum control
Hardware Architecture
Summary
Quantum computers use special electrical signals to control qubits, but leftover distortions can cause errors. The authors developed a fast method using a smart filter running on hardware to fix these distortions in real-time without needing a lot of resources. Their approach keeps the quantum gates accurate over longer times with only a small increase in computer resources. This helps make quantum circuits more reliable and efficient.
What this means in practice
- •For quantum hardware engineers: Implement efficient real-time compensation for signal distortions to maintain high gate fidelity in superconducting quantum processors.
- •For fpga developers: Develop scalable FPGA-based filters to support real-time high-speed signal correction in quantum control systems with low resource overhead.
Authors
Qi Zhou, Zi-Hao Mei, Peng Duan, Peng Wang, Liang-Liang Guo, Hao-Ran Tao, Wei-Cheng Kong, Hui Yang, Guo-Ping Guo, Zhao-Yun Chen
Abstract
Real-time waveform generation supports dynamic quantum circuits without pre-storing complete waveforms for every execution path. However, long-lived distortions in flux-control lines degrade gate fidelity, requiring compensation to account for the actual pulse history. A frequency-domain inversion and time-domain fitting method is proposed for resource-efficient real-time flux distortion compensation. The method fits the reconstructed compensation impulse response with a compact hybrid infinite impulse response (IIR) and finite impulse response (FIR) filter. Look-ahead parallelization enables this filter to process synthesized waveforms at 1.2GSa/s on a field-programmable gate array (FPGA). Two-qubit cross-entropy benchmarking shows that real-time IIR filtering achieves a median controlled-Z Pauli fidelity close to the software-reference value of 99.57%. Numerical analysis and FPGA synthesis indicate approximately logarithmic growth in hardware resource use with compensation timescale. Extending compensation from microsecond to hundred-microsecond timescales increases look-up table (LUT) and digital signal processing (DSP) resource use by only about 14% and 4%, respectively, while maintaining a relative arithmetic error below $10^{-4}$. This work provides a scalable hardware foundation for high-fidelity flux control in dynamic superconducting quantum circuits.