Abstract
Quantum computers (QCs) are currently limited by qubit numbers. A major challenge in scaling these systems is crosstalk, which arises from unwanted interactions among neighboring components such as qubits and resonators. An innovative placement strategy tailored for superconducting QCs can systematically address crosstalk within limited substrate areas.
Legalization is a crucial stage in placement process, refining post-global-placement configurations to satisfy design constraints and enhance layout quality. However, existing legalizers are not supported to legalize quantum placements. We aim to address this gap with qGDP, developed to meticulously legalize quantum components by adhering to quantum spatial constraints and reducing resonator crossing to alleviate various crosstalk effects.
Our results indicate that qGDP effectively legalizes and finetunes the layout, addressing the quantum-specific spatial constraints inherent in various device topologies. By evaluating diverse benchmarks. qGDP consistently outperforms state-of-the-art legalization engines, delivering substantial improvements in fidelity and reducing spatial violation, with average gains of 34.4× and 16.9×, respectively.
- Methodology
- Image
Qubit legalization, the black box represents the layout border, qubits (blue) and resonator segments (gray) are color-coded by frequency; a): GP positions; b): Post-qubit legalization (red dot box depicts minimum spacing constraint, arrows show the displacement)
Image
Resonator Integration-aware legalization, components are color-coded by frequency; a): Connectivity topology; b): Given qubit legalization positions (bin-aided cell search); c): The first wire block (red box) from the resonator (gray) is legalized with minimum displacement. Adjacent available spaces to the legalized blocks from this resonator (gray) are highlighted (light red); d): Legalizing the next wire block (red box) from the same resonator and the adjacent available spaces (light red) is updated; e): Legalization of this resonator continues (red box) and adjacent available spaces keep (light red) updating. f): All the wire blocks from this resonator (light gray) are legalized (red box), and move to the next resonator (dark gray)
Image
Detailed placement a): Identify regions with constraint violations, noted by red dots and zoomed in on the right side (areas with slashed lines are unavailable). b): Construct a focused window (outlined by a red dashed box). c): Extract and reposition resonators to resolve spatial constraint violations.
- Results
- Image
This figure presents the worst-case overall fidelity for various legalization strategies. We evaluated each topological layout by performing 50 mappings of a benchmark program, with each bar in the figure representing the average fidelity. Enhancements are more pronounced with our resonator legalizer. qGDP-LG significantly outperforms traditional methods, improving fidelity by 1.5×, 1.46×, 34.4×, and 34.4× over Q- Abacus, Q-Tetris, Abacus, and Tetris, respectively.
- Citation
@misc{zhang2024qgdpquantumlegalizationdetailed,
title={qGDP: Quantum Legalization and Detailed Placement for Superconducting Quantum Computers},
author={Junyao Zhang and Guanglei Zhou and Feng Cheng and Jonathan Ku and Qi Ding and Jiaqi Gu and Hanrui Wang and Hai "Helen" Li and Yiran Chen},
year={2024},
eprint={2411.02447},
archivePrefix={arXiv},
primaryClass={quant-ph},
url={https://arxiv.org/abs/2411.02447},
}