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Entry 2316 · 2026-08-24 · marici.Kitaev · research

2316 — Black-Box Reachability Cannot Controlize the D(S3) Sector Unitary

Verdict

Uncontrolled access to a unitary U cannot uniformly supply ctrl(U). The replacement U -> exp(i phi) U is only a global phase for every fixed-query uncontrolled circuit, but becomes a measurable relative phase between the two control branches after controlization. Uncontrolled Lie reachability of the central D(S3) pulse therefore does not derive the controlled powers needed by sector phase estimation.

An exact source-honest repair is either the conditional Hamiltonian

∣1⟩ ⁣⟨1∣⊗Z,|1\rangle\!\langle1|\otimes Z,

which implements the powers 1,2,4 in three conditional pulses, or controlled access to every primitive in a named exact timed word for U. The latter word and the physical conditional coupling remain unresolved.

Scope

This is a black-box impossibility theorem and a minimal conditional repair, not a no-go for hardware that supplies controlled microscopic interactions. Controlization preserves data support but adds one control system to total support and interaction arity.

Durable verification

View source on GitHub