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A Classical Verifier Reaches Beyond the Polynomial Hierarchy

Relative to a classical oracle, a public-coin protocol verifies an exactly quantum-decidable language outside the polynomial hierarchy with perfect completeness.

Published Updated Story ID: mp-2026-10-29-013
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Summary

Relative to a classical oracle, a public-coin protocol verifies an exactly quantum-decidable language outside the polynomial hierarchy with perfect completeness.

Whether a classical polynomial-time verifier can efficiently check arbitrary quantum computation without computational assumptions remains open. This paper proves an oracle-relative result for a language outside the polynomial hierarchy but exactly decidable in quantum polynomial time. Its public-coin protocol has perfect completeness and soundness error at most one quarter, using recursively addressed code and data tables. The author also proves a switching theorem for the correlated restrictions that defeat standard tools. Because the construction is relative to a chosen oracle, it does not resolve unrelativized verification of arbitrary real quantum computations.

Why it matters

Relative to a classical oracle, a public-coin protocol verifies an exactly quantum-decidable language outside the polynomial hierarchy with perfect completeness.

Limits and context

  • Because the construction is relative to a chosen oracle, it does not resolve unrelativized verification of arbitrary real quantum computations.

Key claims

  1. Relative to a classical oracle, a public-coin protocol verifies an exactly quantum-decidable language outside the polynomial hierarchy with perfect completeness.

    Qualification: Because the construction is relative to a chosen oracle, it does not resolve unrelativized verification of arbitrary real quantum computations.

    Evidence: source-2026-10-29-013

Sources

  1. arXiv preprint 2610.37635, original v1arXiv · primary research

Corrections

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