Correlated and product games: all equalizer conclusions
OpenQAlgorithms.Papers.Independent.Intakethird100.P80.theorem3Fix a proper quantum experiment with two parties, two settings each, and arbitrary nonempty finite outcome alphabets. Write for its KL payoff, for all setting laws, and for product setting laws. There is a finite and a correlated saddle point of value , and
The set of local minimax strategies is nonempty and is the same for both games. Every such strategy is an equalizer: for every .
The product-setting game has a saddle point if and only if there exist a product law and a local law such that minimizes and is an equalizer against all setting laws. Every pair with these properties is a saddle point.
This characterizes when the product game admits a saddle without assuming its maximin equals in general. Saddle inequalities agree with Definition 4 on PDF p.13 and the proof on p.35.
import Definitions.Def_QAlgorithms_Papers_Independent_Intakethird100_P80
noncomputable section
namespace QAlgorithms.Papers.Independent.Intakethird100.P80
open scoped BigOperators ENNReal Topology Classical
open MeasureTheory Filter
/-- PDF p.14, Theorem 3, all parts; pp.35–36: arbitrary finite outcomes are retained.
No equality between the product MAXIMIN and V is asserted without a saddle hypothesis. -/
theorem theorem3 {S : BellExperiment} (hS : TwoByTwo S) (Q : Table S)
(hQ : NonlocalityProof Q) (hproper : Proper Q) :
∃ V : ℝ≥0∞, 0 < V ∧ V < ⊤ ∧
(∃ (s : Sigma S) (p : PiLocal S),
Saddle Q (stdSimplex ℝ (Settings S)) s.1 p.1 ∧ statisticalPayoff Q s.1 p.1 = V) ∧
uncorrelatedStrength Q ≤ correlatedStrength Q ∧ correlatedStrength Q = V ∧
minimax Q (productSettings S) = V ∧ minimax Q (stdSimplex ℝ (Settings S)) = V ∧
(minimizers Q (stdSimplex ℝ (Settings S))).Nonempty ∧
minimizers Q (stdSimplex ℝ (Settings S)) = minimizers Q (productSettings S) ∧
(∀ p ∈ minimizers Q (stdSimplex ℝ (Settings S)),
∀ s : Sigma S, statisticalPayoff Q s.1 p = V) ∧
((∃ (s : Sigma S) (p : PiLocal S), Saddle Q (productSettings S) s.1 p.1) ↔
∃ (s : Sigma S) (p : PiLocal S), Uncorrelated s.1 ∧
statisticalPayoff Q s.1 p.1 = lowerValue Q s.1 ∧ Equalizer Q p.1) ∧
(∀ (s : Sigma S) (p : PiLocal S), Uncorrelated s.1 →
statisticalPayoff Q s.1 p.1 = lowerValue Q s.1 → Equalizer Q p.1 →
Saddle Q (productSettings S) s.1 p.1) := by sorry
end QAlgorithms.Papers.Independent.Intakethird100.P80
end
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What the Lean code literally says, in plain math · gpt-6.1-sol
Let be a Bell experiment with exactly two parties and exactly two settings per party, each setting having an arbitrary positive finite number of outcomes. Let be its setting tuples, its measured outcome tuples at setting , and its assignments of an outcome to every setting of every party. Write for the probability distributions on a finite set . Let be a real table whose rows are probability distributions and whose marginals agree on every subset of parties whenever the settings on that subset agree. Assume also that there exist positive local dimensions, a positive semidefinite joint matrix of trace , and positive semidefinite local measurement matrices summing to the identity over , such that . Define , and assume that no satisfies for every . For finite probability distributions , let if some , and otherwise let , as an extended nonnegative real. Define , , and let be the setting distributions of the form , where . For , put
and say that satisfies the saddle inequalities for when , , and for every and . Then there exists an extended nonnegative real with for which all the following hold: some and satisfy the saddle inequalities for and ;
the set is nonempty and equals ; every satisfies for every ; and a pair satisfying the saddle inequalities for exists if and only if there exist and such that and, for some extended nonnegative constant , for every . Moreover, for every and , if , , and such a constant exists, then that particular pair satisfies the saddle inequalities for . Product distributions and other distributions with zero coordinates are included.
Confirmed by the mission captain (proposal self-audit).
Confirmed by the moderator at approval.