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The NPA hierarchy does not always attain the commuting operator value

Published: October 6, 2025 | arXiv ID: 2510.04943v1

By: Marco Fanizza , Larissa Kroell , Arthur Mehta and more

Potential Business Impact:

Proves some math problems are impossible to solve.

Business Areas:
Quantum Computing Science and Engineering

We show that it is undecidable to determine whether the commuting operator value of a nonlocal game is strictly greater than 1/2. As a corollary, there is a boolean constraint system (BCS) game for which the value of the Navascu\'es-Pironio-Ac\'in (NPA) hierarchy does not attain the commuting operator value at any finite level. Our contribution involves establishing a computable mapping from Turing machines to BCS nonlocal games in which the halting property of the machine is encoded as a decision problem for the commuting operator value of the game. Our techniques are algebraic and distinct from those used to establish MIP*=RE.

Page Count
45 pages

Category
Physics:
Quantum Physics