Haivian quantum research audit reproduces Gaussian rotation results with comparison caveats
A targeted reproducibility audit supports a central Gaussian-controlled-rotation result in Non-Abelian Quantum Signal Processing while identifying important differences between performance measures.
Haivian Technology has completed a targeted analytical and numerical audit of Gaussian-controlled rotation, a central building block in Non-Abelian Quantum Signal Processing. The audit reproduced four selected public numerical curves and supported the error-cancellation mechanism for the specified ideal Gaussian input. It also identified material caveats in how performance measures and benchmark comparisons should be interpreted.
The conclusion is deliberately specific: the checked core result is reproducible, with comparison caveats. It is not a validation of the entire paper or a demonstration of better performance on quantum hardware.
What the quantum research audit checked
The work by Shraddha Singh, Baptiste Royer and Steven M. Girvin explores control methods involving an oscillator and a qubit. Haivian focused on a two-pulse Gaussian-controlled-rotation primitive and its comparison with the four-pulse BB1 sequence. The checked model starts with a prescribed qubit state and a Gaussian oscillator state of known center and width.
Haivian derived the targeted cancellation mechanism and wrote a separate numerical calculation rather than executing the authors' notebook. Across 640 saved comparison values, the largest absolute difference was approximately 1.25 × 10⁻¹⁴. This is close floating-point agreement with the selected public data, not a mathematically certified bound on numerical error.
The analysis also compared a continuum calculation with a representation using a finite number of oscillator levels. That cross-check showed why numerical truncation matters: an insufficient cutoff can produce misleading results even when a simulation returns normalized final states.
Why the comparison caveats matter
Different measures of quantum performance answer different questions. Qubit-readout failure measures the chance of the wrong qubit outcome. Joint-state fidelity asks whether both the oscillator and qubit match their target state. A sequence can improve one measure without improving the other.
In the checked examples, Gaussian-controlled rotation reduced qubit failures and used fewer conditional gates. But it did not uniformly improve joint fidelity over BB1. At two independently checked displacement values, BB1 had lower joint infidelity. A claim of uniform superiority would therefore go beyond the audit's evidence.
The audit also found that a printed comparative coefficient corresponds to a different metric from the one its surrounding failure-probability comparison suggests. Some tabulated benchmark values are compatible with a leading-order approximation rather than the exact finite-parameter results. These distinctions call for clearer metric and approximation labels; they do not show that the saved comparison curves or the four-pulse implementation are wrong.
Additional scrutiny of published research
Non-Abelian Quantum Signal Processing was published in Physical Review X on 15 October 2026. Haivian's additional audit does not replace the journal's peer review or suggest the work was previously unreviewed.
The detailed mathematical and presentation findings concern the frozen arXiv version 6 manuscript, checked against selected artifacts from the authors' frozen public repository. The audit did not compare every equation with the final journal edition, so it does not assert that the localized presentation issues persist there.
Later claims involving state preparation, noisy quantum error correction, multimode gates and phase estimation remain outside this audit. The result also depends on the specified input state; it does not establish the same cancellation for arbitrary quantum states.
Reproducibility without an all or nothing verdict
For researchers, the useful outcome of a third-party research audit need not be an unqualified pass or fail. An audit can support a mechanism, reproduce selected calculations and still identify limits that affect how the result should be communicated or used.
This case illustrates that distinction. The central checked Gaussian result survived additional derivation and numerical comparison. The benchmark qualifications remain part of the published conclusion rather than being omitted from the announcement.
Researchers can read the full scoped audit for the calculations, comparison details and evidence identities, or explore Haivian's computational reproducibility audit service for a defined claim, model or research workflow. The appropriate audit scope depends on the question and the available materials.
Review and disclosure
Haivian Technology authored this report and news article, commissioned by Richard Janutka of Qonduit Limited, New Zealand. Distinct-agent scientific review used the same AI provider and was not external human peer review; the reviewer had seen proposed formulas before its own checks. The audit service and publishing operation share organizational control.
The checks used retained Python, NumPy and numerical libraries. They were not a formal proof-assistant verification, a clean-room toolchain rebuild or a quantum-hardware experiment. The authors and their institutions have not endorsed this audit or Haivian's services.