qshelf — a tested package registry of quantum algorithm implementations for guppylang/HUGR

[kkoci]

Sharing another project, alongside Estimand, in case it's useful to others working with guppylang.

What it is: qshelf is a curated, tested library of quantum algorithm implementations for guppylang/HUGR, QFT, Grover's search, QAOA/MaxCut, and VQE for H2 so far, with a repetition-code error-correction primitive planned. Each package is verified against an independent reference, exact linear algebra, scipy.linalg.expm, or exact diagonalization, depending on the algorithm, rather than just "runs without error." Distributed as linkable HUGR Packages.

Bugs found along the way: building and verifying these against real reference implementations surfaced four real guppylang issues. #2250, iqft produces a wrong unitary when compiled standalone vs. combined with qft. #2251, multi-controlled Z (2+ controls) produces a wrong unitary with spurious imaginary components, since fixed in guppylang 1.0.3. #2253, arithmetic in a generic array-length type (array[bool, n-1], array[T, n+1], etc.) is rejected outright, closed as a known limitation tracked in #785. #2252, a raw numpy.ndarray closed over in a guppy function body being rejected unlike a plain list, reclassified as a feature request.

Repo: qshelf

Happy to hear if any of these packages are useful as-is, or if there's interest in more algorithms or the repetition-code primitive once it's built.