Section 3 — Strategy core #
Base state-invariance and strategy structures for the low individual degree test.
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The SWAP reindexing on ι × ι: permutes the two tensor factors.
swapDensity M (i₁,i₂) (j₁,j₂) = M (i₂,i₁) (j₂,j₁).
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swapDensity is equal to reindexing by the product-commutation equivalence.
swapDensity preserves matrix multiplication.
Permutation-invariance for a bipartite state on ι × ι.
The primary datum is that the density operator is fixed by the SWAP reindexing,
swapDensity ψ.density = ψ.density. We also cache the frequently used
one-sided expectation consequence
ev ψ (leftTensor M) = ev ψ (rightTensor M).
This matches the symmetric-strategy construction used in the paper
(Section 3) and exposes enough symmetry to swap fully bipartite
consistency expressions.
The density operator is fixed by the SWAP reindexing.
Swapping tensor factors preserves one-sided expectation values.
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Direct outcome-level covariance for axis-parallel-line measurements.
Rebasing a line question by t and reparametrizing an outcome polynomial by
the same translation leaves the corresponding projector unchanged.
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Direct outcome-level covariance for diagonal-line measurements.
Rebasing a line question by t and reparametrizing an outcome polynomial by
the same translation leaves the corresponding projector unchanged.
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Reparametrization invariance for diagonal-line measurements: evaluating a
rebased line at zeroCoord agrees outcome-wise with evaluating the original
line at the rebasing parameter.
At the answer level, the geometric identity is
DiagonalLinePolynomial.reparamAt_apply_zero. This predicate is stronger: it
asserts that the measurement family itself is covariant under rebasing the
question index.
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Reparametrization invariance for axis-parallel-line measurements: evaluating a
rebased line at zeroCoord agrees outcome-wise with evaluating the original
line at the rebasing parameter.
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Transport an axis-parallel-line measurement along rebasing of the line question by translating its polynomial outcomes.
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Evaluating a transported axis-line measurement at zeroCoord agrees with
reading the original measurement at the rebasing parameter.
Transport a diagonal-line measurement along rebasing of the line question by translating its polynomial outcomes.
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Evaluating a transported diagonal-line measurement at zeroCoord agrees with
reading the original measurement at the rebasing parameter.
Stronger rebasing compatibility for axis-parallel-line measurements: the measurement indexed by the rebased line is equal to the transport of the original measurement along the answer reparametrization equivalence.
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Stronger rebasing compatibility for diagonal-line measurements: the measurement indexed by the rebased line is equal to the transport of the original measurement along the answer reparametrization equivalence.
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Transport-level axis-parallel covariance implies direct outcome covariance.
Transport-level diagonal covariance implies direct outcome covariance.
Direct axis-parallel outcome covariance implies transport-level covariance.
Direct diagonal outcome covariance implies transport-level covariance.
Direct outcome covariance and transport-level covariance are equivalent for axis-parallel-line projective measurements.
Direct outcome covariance and transport-level covariance are equivalent for diagonal-line projective measurements.
The stronger transport-level axis-parallel compatibility implies the older outcome-level reparametrization invariant predicate.
The stronger transport-level diagonal compatibility implies the older outcome-level reparametrization invariant predicate.
Axis-parallel line measurements bundled with the stronger transport-level rebasing covariance.
- toIdxProjMeas : IdxProjMeas (AxisParallelLine params) (AxisLinePolynomial params) ι
- transportInvariant : AxisParallelMeasurementTransportInvariant params self.toIdxProjMeas
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A covariant wrapper automatically satisfies the older evaluation-level rebasing invariant.
Diagonal line measurements bundled with the stronger transport-level rebasing covariance.
- toIdxProjMeas : IdxProjMeas (DiagonalLine params) (DiagonalLinePolynomial params) ι
- transportInvariant : DiagonalMeasurementTransportInvariant params self.toIdxProjMeas
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A covariant wrapper automatically satisfies the older evaluation-level rebasing invariant.
Transport covariance for diagonal-line measurements whose answers are the paper-level line functions.
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Diagonal-line measurements with paper-level function answers, bundled with transport-level rebasing covariance.
This parallel API is intended for the paper-faithful restriction redesign: unlike
DiagonalLinePolynomial, the function-answer alphabet admits a total slice
append/restrict equivalence.
- toIdxProjMeas : IdxProjMeas (DiagonalLine params) (DiagonalLineAnswer params) ι
- transportInvariant : DiagonalAnswerMeasurementTransportInvariant params self.toIdxProjMeas
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Paper-level symmetric strategy data whose diagonal-line answers are functions.
This parallel structure is the target shape for the restriction redesign in
Section 6: restricting an ambient diagonal line to a slice is total for function
answers, unlike the current degree-bounded DiagonalLinePolynomial alphabet.
- state : QuantumState (ι × ι)
- permInvState : PermInvState self.state
- isNormalized : self.state.IsNormalized
- pointMeasurement : IdxProjMeas (Point params) (Fq params) ι
- axisParallelMeasurement : AxisParallelCovariantMeasurement params ι
- diagonalMeasurement : DiagonalAnswerCovariantMeasurement params ι
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Paper-local symmetric strategy data.
The line-measurement fields are bundled as transport-covariant wrappers:
rebasing the question index is required to agree with transporting the
projective measurement along the corresponding answer reparametrization
equivalence. This is stronger than the older evaluation-level formulas
at zeroCoord, but those formulas remain available as derived lemmas via
AxisParallelCovariantMeasurement.reparamInvariant and
DiagonalCovariantMeasurement.reparamInvariant.
The isNormalized field records that the bipartite state's density
operator has normalized trace 1. For pure states, this coincides
with the usual unit-vector condition (⟨ψ|ψ⟩ = 1) used in the paper.
Bundling normalization with the strategy avoids threading a
state.IsNormalized hypothesis through every downstream consumer
(pasting cascade, triangleSub users, self-improvement helpers).
- state : QuantumState (ι × ι)
- permInvState : PermInvState self.state
- isNormalized : self.state.IsNormalized
- pointMeasurement : IdxProjMeas (Point params) (Fq params) ι
- axisParallelMeasurement : AxisParallelCovariantMeasurement params ι
- diagonalMeasurement : DiagonalCovariantMeasurement params ι
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Encoded samples (u, i) for the axis-parallel lines test.
The paper samples a random point u ∈ F_q^m and a coordinate
i ∈ {1, …, m}. In Lean, Fin params.m represents the 0-indexed
coordinates {0, …, m - 1}, corresponding to the paper's 1-indexed
choice. The sample forms the axis-parallel line through u in that
coordinate direction.
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- MIPStarRE.LDT.AxisParallelTestSample params = (MIPStarRE.LDT.Point params × Fin params.m)
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Extend restricted direction coordinates to a full direction vector.
For restriction index j (0-indexed), the first j + 1 coordinates
are the given free coordinates and the remaining are zero.
This matches the paper's convention that v has its last m − i
coordinates zero, where i = j + 1.
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- MIPStarRE.LDT.extendRestrictedDirection j freeCoords k = if h : ↑k ≤ ↑j then freeCoords ⟨↑k, ⋯⟩ else MIPStarRE.LDT.zeroCoord
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Encoded samples (u, freeCoords) for the j-restricted diagonal
lines test. The base point u ∈ F_q^m and the free coordinates of
the restricted direction (first j + 1 coordinates; rest are zero).
The full diagonal test averages over j ∈ {0, …, m − 1}.
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- MIPStarRE.LDT.RestrictedDiagonalSample params j = (MIPStarRE.LDT.Point params × (Fin (↑j + 1) → MIPStarRE.LDT.Fq params))
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The restricted diagonal sample space is nonempty.
Sampled point answers in the axis-parallel lines test, obtained from a point measurement.
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- MIPStarRE.LDT.axisParallelPointAnswerFamilyOf pointMeasurement s = (pointMeasurement s.1).toSubMeas
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Sampled line answers in the axis-parallel lines test, obtained from an axis-parallel measurement and evaluated at the base point.
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Sampled point answers in the restricted diagonal test, obtained from a point measurement.
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- MIPStarRE.LDT.diagonalPointAnswerFamilyOf pointMeasurement j s = (pointMeasurement s.1).toSubMeas
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Sampled diagonal-line answers in the restricted diagonal test, obtained from a diagonal-line measurement and evaluated at the base point.
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Sampled point answers in the axis-parallel lines test.
The point player receives u (the base point) and answers with
their measurement at u.
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Sampled line answers in the axis-parallel lines test,
evaluated at the base point u.
The line player receives ℓ and returns a polynomial f.
The verifier checks f(u) = a; since u = ℓ.pointAt zeroCoord,
we evaluate f at zeroCoord.
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The axis-parallel line in F_q^(m+1) through (u, 0) in the last
coordinate direction. This is the geometric line denoted B^u in the paper's
last-direction notation.
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- MIPStarRE.LDT.lastDirectionLine params u = { base := MIPStarRE.LDT.appendPoint params u MIPStarRE.LDT.zeroCoord, direction := MIPStarRE.LDT.lastCoord params }
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The axis-parallel line measurement family restricted to the paper's
last-direction notation u ↦ B^u.
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- MIPStarRE.LDT.lastDirectionMeasurementFamily strategy u = strategy.axisParallelMeasurement.toIdxProjMeas (MIPStarRE.LDT.lastDirectionLine params u)
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Sampled point answers in the j-restricted diagonal test.
The point player receives u and answers at u.
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- MIPStarRE.LDT.diagonalPointAnswerFamily strategy j = MIPStarRE.LDT.diagonalPointAnswerFamilyOf strategy.pointMeasurement j
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Sampled diagonal-line answers in the j-restricted diagonal
test, evaluated at the base point u.
Since u = ℓ.pointAt zeroCoord, we evaluate f at
zeroCoord.
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Sampled point answers in the axis-parallel lines test for an answer-valued symmetric strategy.
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Sampled line answers in the axis-parallel lines test for an answer-valued symmetric strategy, evaluated at the base point.
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Sampled point answers in the restricted diagonal test for an answer-valued symmetric strategy.
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- strategy.diagonalPointAnswerFamily j = MIPStarRE.LDT.diagonalPointAnswerFamilyOf strategy.pointMeasurement j
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Sampled diagonal-line answers in the restricted diagonal test for an answer-valued symmetric strategy, evaluated at the base point.
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Axis-parallel failure surrogate for an answer-valued symmetric strategy.
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Self-consistency failure surrogate for an answer-valued symmetric strategy.
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Diagonal-line failure surrogate for an answer-valued symmetric strategy.
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Goodness data for an answer-valued symmetric strategy.
The axis-parallel test fails with probability at most
eps.The self-consistency test fails with probability at most
delta.The diagonal-line test fails with probability at most
gamma.
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Paper-faithful two-space projective strategy data.
This matches the paper's def:general-projective-strategy
(test_definition.tex, lines 98--115): Alice's and Bob's measurements act on
separate local carriers ιA and ιB, and the bipartite state lives on
ιA × ιB without a built-in swap symmetry.
The isNormalized field records that the bipartite state's density operator
has normalized trace 1.
The four covariance conditions express that the line-indexed projectors descend from chosen affine parametrizations to geometric lines; transport and zero-coordinate evaluation are equivalent consequences.
- state : QuantumState (ιA × ιB)
Bipartite state on the tensor product of Alice's and Bob's local carriers.
- isNormalized : self.state.IsNormalized
The bipartite state's density operator is trace-normalized.
- pointMeasurementA : IdxProjMeas (Point params) (Fq params) ιA
Alice's point-measurement family, acting on
ιA. - axisParallelMeasurementA : IdxProjMeas (AxisParallelLine params) (AxisLinePolynomial params) ιA
Alice's axis-parallel-line measurement family, acting on
ιA. - axisParallelReparamInvariantA : AxisParallelMeasurementReparamInvariant params self.axisParallelMeasurementA
Alice's axis-parallel measurement is covariant under line rebasing.
- diagonalMeasurementA : IdxProjMeas (DiagonalLine params) (DiagonalLinePolynomial params) ιA
Alice's diagonal-line measurement family, acting on
ιA. - diagonalReparamInvariantA : DiagonalMeasurementReparamInvariant params self.diagonalMeasurementA
Alice's diagonal measurement is covariant under line rebasing.
- pointMeasurementB : IdxProjMeas (Point params) (Fq params) ιB
Bob's point-measurement family, acting on
ιB. - axisParallelMeasurementB : IdxProjMeas (AxisParallelLine params) (AxisLinePolynomial params) ιB
Bob's axis-parallel-line measurement family, acting on
ιB. - axisParallelReparamInvariantB : AxisParallelMeasurementReparamInvariant params self.axisParallelMeasurementB
Bob's axis-parallel measurement is covariant under line rebasing.
- diagonalMeasurementB : IdxProjMeas (DiagonalLine params) (DiagonalLinePolynomial params) ιB
Bob's diagonal-line measurement family, acting on
ιB. - diagonalReparamInvariantB : DiagonalMeasurementReparamInvariant params self.diagonalMeasurementB
Bob's diagonal measurement is covariant under line rebasing.