How QUITS Builds Quantum Circuits With Six Distinct Code Families

Researchers at the Duke Quantum Center have developed QUITS, a modular simulator enabling detailed circuit-level analysis of quantum low-density parity-check (QLDPC) codes. The simulator natively supports six distinct code families, Hypergraph Product, Quasi-cyclic Lifted Product, Balanced Product Cyclic, Lift-Connected Surface, Bivariate Bicycle, and Mitten codes, and allows users to import any code with provided parity check matrices. The team states that QUITS’ flexibility stems from independent modules for code construction, decoding, noise modeling, and layout, offering researchers a comprehensive platform to explore and optimize quantum error correction strategies.

The modular design extends to circuit construction, with the zxcoloration strategy available across all supported QLDPC codes, potentially offering a universal optimization technique. For HGP, QLP, BPC, and LCS codes, researchers can utilize either the cardinal or cardinalNSmerge circuit construction strategies, while the custom strategy is reserved specifically for BB codes, demonstrating a tailored approach to building circuits based on the chosen code family. Mitten codes leverage a depth-12 interleaved mixed X/Z schedule with the custom strategy, and an alternative hook_error_free strategy provides a depth-24 group-element-layer schedule.

QUITS is designed for seamless integration with other tools; the developers recommend pairing it with Stim, a fast stabilizer circuit simulator, and LDPC, which provides BP-OSD and BP-LSD decoders for QLDPC codes. Mingyu Kang, Yingjia Lin, Hanwen Yao, Mert Gökduman, Arianna Meinking, and Kenneth R. Brown originally developed the simulator, and they acknowledge valuable feedback from Ryan Tiew, Josias Old, qodesign, and Daniel Tan since its release.