Draft · v0.2 · Unreviewed
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Nadarasa · v0.3.3 · PQP Ch. 12

G3, split: Grover vs HSP

The legacy GAP G3 entry asked for a "per-window √p improvement." Picturing Quantum Processes Ch. 12 puts Grover (§12.2.3, √-cost from amplitude amplification) and Abelian HSP (§12.2.4, log-cost) in disjoint sections, with Ex. 12.22 explicitly noting Deutsch–Jozsa for n > 1 is NOT HSP. The original single ledger entry was mixing two different cost laws into one verdict cell. v0.3.3 splits it.

G3-grover · amplitude-amplification per-rung cost

queries ~ √(N / w)

Conjecture: After modal projection onto a window of width w, the search cost per rung scales as √(N/w) — the Grover/amplitude-amplification law.

PQP anchor: Ch. 12 §12.2.3 (Grover) — √ comes from amplitude amplification only.

Prior artifact: The legacy 'per-window √p improvement' framing was implicitly invoking this law (with w = N/p).

Measured status: At /nadarasa/g3-cost the post-selected stream lives on 2–3 distinct y-values per slope regardless of N, so the effective window does NOT grow with N. Without growing w the law has no purchase. Status: kernel can't probe the conjecture as-is.

Next step: Build a kernel whose modal window has support that genuinely scales with N (e.g. the G2-real two-coset combiner post-selected on residue 0) and re-run the cost sweep there.

G3-hsp · structural exponential speedup

queries ~ O(log |G/H|)

Conjecture: If the underlying problem is an Abelian HSP instance, the cost is O(log|G/H|) — exponential, no √-factor.

PQP anchor: Ch. 12 §12.2.4 + Ex. 12.22.

Prior artifact: The original draft's '√p improvement' language confused HSP structure with Grover structure. PQP refutes the framing: HSP and Grover live in disjoint regions of Ch. 12.

Measured status: Not yet measured by any Nadarasa kernel; G1 / G2-real demonstrate the coset-state primitive but stop short of the full HSP coset-finding loop. Requires the QFT register output to be POST-PROCESSED (continued fractions / lattice reduction), not just observed empirically.

Next step: Out-of-scope at the current dashboard tier — would require a classical post-processor wrapping the existing Selene runs. Tracked as a separate work item, not a G3 sub-claim.

What this changes in the GAP ledger

  • G3 is retired as a single entry. The page at /nadarasa/g3 and the v0.3.2 cost sweep at /nadarasa/g3-cost both fall under G3-grover going forward.
  • G3-hsp ships as a scoping placeholder. It is testable only with a classical post-processor wrapping the QFT register output, which is out of the current dashboard's scope.
  • The "kernel can't probe it" verdict from /nadarasa/g3-cost is now framed correctly: the kernel can't probe G3-grover because its modal window doesn't grow with N. It was never trying to probe G3-hsp.