Maximally entangled states are not complete for pseudo-telepathy

Olivier Lalonde

Lalonde gives a bipartite inner-product game with four and three inputs and six outputs. It has a perfect strategy using a nonmaximally entangled state, but no perfect finite-dimensional strategy using a maximally entangled state.

Sources for this record

What was already known

Previously known pseudo-telepathic games admitted perfect maximally entangled strategies. Earlier work showed some games could also use nonmaximally entangled states, but did not show maximally entangled states were insufficient for every perfect strategy.

AI involvement AI-centered

Lalonde devised inner-product games and the search method. Codex found the retained game matrix, pruned the game and extracted and implemented its exact rational exclusion certificate.

The human author supplied the conceptual framework, but Codex found the retained game matrix and certificate essential to the counterexample.

Importance Notable

Gives a concrete finite-dimensional counterexample to completeness of maximally entangled strategies.

Limitations

The Lean certificate checks the finite-dimensional maximally entangled exclusion. The analytic existence argument has no separately documented completed check, and no infinite-dimensional exclusion is claimed.

Technical verification Partial

The repository reports an exact Lean certificate excluding all finite-dimensional maximally entangled perfect strategies for the concrete game. The existence of a perfect nonmaximally entangled strategy is argued in the paper, without a documented completed check of that analytic side; the repository also does not claim infinite-dimensional tracial exclusion.

Formal checking

The repository reports an exact Lean certificate excluding all finite-dimensional maximally entangled perfect strategies for the concrete game. The existence of a perfect nonmaximally entangled strategy is argued in the paper, without a documented completed check of that analytic side; the repository also does not claim infinite-dimensional tracial exclusion.

Checker
Lean 4 checker in Lalonde's repository, as reported by the author
Scope
No perfect finite-dimensional maximally entangled strategy with arbitrary six-outcome POVMs exists for the specified 4-by-3 game
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

Lalonde describes his own conceptual game class, heuristic, hierarchy modification and the proof plan for the concrete counterexample.

Correction and publication history

2026-10-18 · publication

Codex found the retained game matrix and exact exclusion certificate within Lalonde’s design.

Read this published revision