QUITS: A modular Qldpc code circUIT Simulator

Mingyu Kang; Yingjia Lin; Hanwen Yao; Mert Gökduman; Arianna Meinking; Kenneth R. Brown

doi:10.22331/q-2025-12-05-1931

QUITS: A modular Qldpc code circUIT Simulator

Mingyu Kang^1,2, Yingjia Lin^1,2, Hanwen Yao^1,3, Mert Gökduman^1,3, Arianna Meinking^1,2, and Kenneth R. Brown^1,2,3,4

¹Duke Quantum Center, Duke University, Durham, NC 27701, USA
²Department of Physics, Duke University, Durham, NC 27708, USA
³Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708, USA
⁴Department of Chemistry, Duke University, Durham, NC 27708, USA

Published:	2025-12-05, volume 9, page 1931
Editor:	Philipp Schindler
Eprint:	arXiv:2504.02673v2
Doi:	https://doi.org/10.22331/q-2025-12-05-1931
Citation:	Quantum 9, 1931 (2025).

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Abstract

To achieve quantum fault tolerance with lower overhead, quantum low-density parity-check (QLDPC) codes have emerged as a promising alternative to topological codes such as the surface code, offering higher code rates. To support their study, an end-to-end framework for simulating QLDPC codes at the circuit level is needed. In this work, we present QUITS, a modular and flexible circuit-level simulator for QLDPC codes. Its design allows users to freely combine LDPC code constructions, syndrome extraction circuits, decoding algorithms, and noise models, enabling comprehensive and customizable studies of the performance of QLDPC codes under circuit-level noise. QUITS supports several leading QLDPC families, including hypergraph product codes, lifted product codes, and balanced product codes. As part of the framework, we introduce a syndrome extraction circuit improved from Tremblay, Delfosse, and Beverland [Phys. Rev. Lett. 129, 050504 (2022)] that applies to all three code families. In particular, for a small hypergraph product code, our circuit achieves lower depth than the conventional method, resulting in improved logical performance. Using QUITS, we evaluate the performance of state-of-the-art QLDPC codes and decoders under various settings, revealing trade-offs between the decoding runtime and the logical failure rate. The source code of QUITS is available online.

Featured image: QUITS: A modular Qldpc code circUIT Simulator

Popular summary

Quantum error correction is necessary to keep the fragile qubits error-free in a large quantum computer, but doing so efficiently remains a major challenge. A promising strategy is to use quantum low-density parity-check (QLDPC) codes, which can protect information using far fewer extra qubits than many traditional quantum codes. But understanding how these codes actually behave in realistic hardware requires accurate and flexible simulations. This work introduces QUITS, a new simulation platform built to model QLDPC codes at the level of full quantum circuits. QUITS can test several major families of these codes, incorporate improved circuits for extracting error information, and plug in various decoding strategies to evaluate their performance. We anticipate that QUITS will guide researchers in exploring practical design choices and decoding trade-offs for QLDPC codes, helping advance the quest for scalable, fault-tolerant quantum computing.
Open-source repo: https://github.com/mkangquantum/quits

► BibTeX data

@article{Kang2025quitsmodularqldpc,
  doi = {10.22331/q-2025-12-05-1931},
  url = {https://doi.org/10.22331/q-2025-12-05-1931},
  title = {{QUITS}: {A} modular {Q}ldpc code circ{UIT} {S}imulator},
  author = {Kang, Mingyu and Lin, Yingjia and Yao, Hanwen and G{\"{o}}kduman, Mert and Meinking, Arianna and Brown, Kenneth R.},
  journal = {{Quantum}},
  issn = {2521-327X},
  publisher = {{Verein zur F{\"{o}}rderung des Open Access Publizierens in den Quantenwissenschaften}},
  volume = {9},
  pages = {1931},
  month = dec,
  year = {2025}
}

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Cited by

[1] Seok-Hyung Lee, Lucas H. English, and Stephen D. Bartlett, "Efficient post-selection for general quantum LDPC Codes", npj Quantum Information 12 1, 96 (2026).

[2] Chaithanya Naik Mude and Swamit Tannu, Proceedings of the 58th IEEE/ACM International Symposium on Microarchitecture 579 (2025) ISBN:9798400715730.

[3] Chaithanya Naik Mude and Swamit Tannu, "Accurate Leakage Speculation for Quantum Error Correction", arXiv:2510.25661, (2025).

[4] Bane Vasic, Valentin Savin, Michele Pacenti, Shantom Borah, and Nithin Raveendran, "Quantum Low-Density Parity-Check Codes", arXiv:2510.14090, (2025).

[5] Victor V. Albert and Philippe Faist, "Handbook of Error-Correcting Codes", arXiv:2606.11484, (2026).

[6] Aleksandra Świerkowska, Jannik Pflieger, Emmanouil Giortamis, and Pramod Bhatotia, "ECCentric: An Empirical Analysis of Quantum Error Correction Codes", arXiv:2511.01062, (2025).

[7] Yuhao Liu, Shuohao Ping, Junyu Zhou, Ethan Decker, Justin Kalloor, Mathias Weiden, Kean Chen, Yunong Shi, Ali Javadi-Abhari, Costin Iancu, and Gushu Li, "AlphaSyndrome: Tackling the Syndrome Measurement Circuit Scheduling Problem for QEC Codes", arXiv:2601.12509, (2026).

[8] Sahil Khan, Abhinav Anand, Kenneth R. Brown, and Jonathan M. Baker, "Cyclone: Designing Efficient and Highly Parallel QCCD Architectural Codesigns for Fault Tolerant Quantum Memory", arXiv:2511.15910, (2025).

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