Soundness of answer reduction: the decoded strategy #
Piece AR-5e of planning/answer-reduction.md (lem:ar-ora): a strategy for the typed
oracularized game of the input verifier, on the typed strategy's state. An oracle measures the
extracted simultaneous measurement J and answers the pair decoded from the first two answer
polynomials its outcome carries on their blocks (decO); an isolated player measures the
extracted G of its own copy and answers the decoded polynomial (decV). The decoder dec is a
parameter here.
Each of the nine ordered pairs of roles fails at most (condFail_OO_le, condFail_Ov_le, ...):
- the game check of an oracle's decoded pair, which fails only if
J's outcome is not placed on its blocks or the PCP check rejects it at at least half the points (the hypothesishgc, the contrapositive of the PCP's soundness):gcA_le; - the disagreement of the decoded answers, which is at most that of the polynomials.
The failure of the decoded strategy is then at most a constant times the errors of
SoundRelations, SoundPoly and SoundGameCheck (one_sub_povmValue_decoded_le).
The decoded measurements are coarse-grainings of the extracted projective ones, so the decoded
strategy is a projective strategy in the same model (decoded), and no dilation is needed: its
value is at most ω of the typed oracularized game in every value model ω that dominates the
model (ValueModel.Dominates), and oracularization's soundness in ω bounds the input verifier
(val_ge_decoded). The matrix proof dilated a POVM strategy here (Naimark); that step is gone.
The decoding #
The answer polynomial of copy i an outcome of J carries: its i-th component read on
copy i's block.
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An oracle's decoded answer: the pair decoded from the first two answer polynomials.
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- MIPRE.AnswerReduction.decO P hk B' dec f = MIPRE.OAns.pair (dec (MIPRE.AnswerReduction.gPoly P hk 0 f)) (dec (MIPRE.AnswerReduction.gPoly P hk 1 f))
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An isolated player's decoded answer.
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- MIPRE.AnswerReduction.decV P hk B' dec g = MIPRE.OAns.single (dec (g 0).toMv)
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An outcome of J is placed on its blocks when each of its first five components is the
placement of its reading on its block.
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The component of an oracle's answer an isolated player's role checks.
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The answer of an isolated player.
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The typed oracularized game of the input verifier at index n, answers of length B'.
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- MIPRE.AnswerReduction.oGame V n B' = MIPRE.CL.Detyping.typedGame MIPRE.roleGraph MIPRE.roleGraph_nonempty (fun (x : Bool) => MIPRE.roleFamily (V.sampler.cl n)) (V.seeded n B').oaccepts
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Alice's decoded measurements.
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- MIPRE.AnswerReduction.MAo V n P hk S S' check B T hL B' dec (MIPRE.Role.oracle, y) = MIPRE.POVMIn.map (MIPRE.AnswerReduction.decO P hk B' dec) (MIPRE.AnswerReduction.JA V n P hk S S' check B T ⋯ y)
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Bob's decoded measurements.
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- MIPRE.AnswerReduction.MBo V n P hk S S' check B T hL B' dec (MIPRE.Role.oracle, y) = MIPRE.POVMIn.map (MIPRE.AnswerReduction.decO P hk B' dec) (MIPRE.AnswerReduction.JB V n P hk S S' check B T ⋯ y)
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Alice's decoded measurements are projective: coarse-grainings of the extracted projective measurements.
Bob's decoded measurements are projective.
The decoded strategy: a projective strategy in the model, on the typed strategy's state, for the typed oracularized game of the input verifier.
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The weight of Alice's J outcomes whose decoded pair fails the game check.
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The weight of Bob's J outcomes whose decoded pair fails the game check.
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The nine pairs of roles #
Two oracles: the two game checks and the disagreement of the two J.
The decoded answer an oracle's v-th component and an isolated player's answer agree
whenever the polynomials agree, as placed polynomials.
The mirror image.
An oracle and Alice: the oracle's game check and the disagreement of its first answer polynomial with Alice's.
An oracle and Bob.
Alice and an oracle.
Bob and an oracle.
Alice and Alice: the disagreement of the two extracted polynomial measurements.
Alice and Bob never fail: only the formats are checked.
Bob and Bob: the disagreement of the two extracted polynomial measurements.
Bob and Alice never fail: only the formats are checked.
The game check #
The PCP's soundness, as the decoded strategy needs it: an outcome of J placed on its
blocks, whose evaluations the check accepts at more than half the points, decodes to a pair the
input's game check accepts.
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The fraction of points at which the check rejects an outcome's evaluations.
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A placed outcome whose decoded pair fails the game check is rejected at at least half the points.
An outcome not placed on block i differs from every placed polynomial.
The oracle's game check under Alice's J: the outcomes not placed on their blocks, which
disagree with Bob's placed G, plus twice the weight of the rejected evaluations.
The oracle's game check under Bob's J, the mirror image.
The value of the decoded strategy #
The combined error of the decoded strategy's analysis.
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Alice's oracles' game checks, summed over the oracle halves.
Bob's oracles' game checks, summed over the oracle halves.
The two oracles' J disagree at most the sixth copy's extraction error, on average.
Two isolated players' G disagree at most copy i's extraction error, on average.
The failure of a strategy for a typed oracularized game is the average, over the ordered pairs of roles and the seed, of its failure at the questions they determine.
The decoded strategy's failure at a seed, over the nine ordered pairs of roles.
The decoded strategy fails the typed oracularized game with probability at most 6 times
the combined error, given the PCP's soundness in the form hgc.
The input verifier's value #
The input verifier's value is close to 1, in a value model where oracularization is
sound and which dominates the model: the decoded strategy is a projective strategy in the model,
on the typed strategy's state, for the typed oracularized game, and fails it with probability at
most 6 times the combined error. No dilation is needed, since the decoded measurements are
coarse-grainings of the extracted projective ones (MAo_proj).