Embeddings of bipartite models #
A local isometry (BipartiteModel.LocalIsometry) that carries the state to the state and keeps
both players' units is an embedding of bipartite models (BipartiteModel.Embedding): the model
form of "adjoin ancilla registers in fixed vectors", and of the reduced isometry of the soundness
analysis of the Pauli basis test. New in Phase 5 of planning/mipco-track.md, where that analysis
is stated in a bipartite model; there the matrix statements that a quantity is unchanged when
registers in fixed vectors are adjoined, regrouped or read across the cut become transfers along
an embedding.
- An embedding carries every quantity computed from the state and the players' operators: Born
probabilities (
Embedding.bornProb), the players' state norms (Embedding.stateSqNorm,Embedding.swap_stateSqNorm), cross norms (Embedding.xSqNorm), and, being unital, the value and the inconsistency of families of measurements pushed forward (Embedding.povmValue_pushforward,Embedding.inconsistency_pushforward). A sum of products of the two players' operators keeps its state norm and quadratic form along any local isometry carrying the state to the state (LocalIsometry.snorm_sum_mul_of_W_ψ,LocalIsometry.qform_sum_mul_of_W_ψ). - Embeddings compose (
Embedding.comp), exchange with the players (Embedding.swap), and every isomorphism is one (Iso.toEmbedding). The local isometries between extensions ofMIPRE/Foundations/AncillaIsometry.leanare embeddings once their state conditions hold (inertEmb,assocEmb,relabelEmb,swapExpandEmb), and so is the change of cut ofMIPRE/Foundations/ModelReading.lean(recutEmb). - Two local isometries with no state condition: the same maps into the target with its state
replaced (
LocalIsometry.toWithState), and the conjugation of a model by a unitary of each player (LocalIsometry.ofUnitary), a local isometry because the two players' operators commute. - Relabelling the outcomes of both families along one bijection keeps their inconsistency
(
BipartiteModel.inconsistency_map_equiv), and pushing a POVM forward along a composite is pushing it forward twice (POVMIn.pushforward_comp).
Pushing a POVM forward along a composite #
Pushing a POVM forward along a composite is pushing it forward twice.
Relabelling the outcomes of two families along one bijection #
Relabelling the outcomes of both families along one bijection keeps their inconsistency.
The product of a unitary of each player is represented by an isometry: (U V)* (U V) = 1
needs only U* U = 1 and V* V = 1.
Three facts about local isometries #
A local isometry into a model with its state replaced: the same isometry and homomorphisms, the target's state playing no part in a local isometry.
Instances For
The isometry intertwines a sum of products of the two players' operators with the sum of the products of their images.
A sum of products of the two players' operators keeps its state norm along a local isometry carrying the state to the state.
A sum of products of the two players' operators keeps its quadratic form along a local isometry carrying the state to the state.
Conjugation by a unitary of each player #
Conjugation by a unitary of each player: the isometry is the product πA U πB V of the
two unitaries, and each player's operators are conjugated by the player's unitary,
X ↦ U X U* and Y ↦ V Y V*. It is an isometry by U* U = 1 and V* V = 1, and it intertwines
because the two players' operators commute; U U* = 1 and V V* = 1 make the two
homomorphisms unital (ofUnitary_ΦA_one, ofUnitary_ΦB_one). The state is carried to the state
only when πA U πB V fixes it, which is not asked.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The conjugation of the first player's operators is unital.
The conjugation of the second player's operators is unital.
Embeddings #
An embedding of bipartite models: a local isometry carrying the state to the state and preserving both players' units. It is the model form of an extension by ancilla registers in fixed vectors, and of the reduced isometry of the soundness analysis of the Pauli basis test; everything a model computes from its state and its players' operators is carried along it unchanged.
The isometry carries the state to the state.
The first player's unit goes to the unit.
The second player's unit goes to the unit.
Instances For
The identity embedding.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Embeddings compose, the second argument applied first (as LocalIsometry.comp).
Equations
Instances For
The embedding with the players exchanged.
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What an embedding carries over #
Born probabilities are carried over.
The first player's state norms are carried over.
The second player's state norms are carried over.
The cross norms are carried over.
The state has the norm of the state.
Two families of measurements pushed forward along an embedding have their inconsistency.
A family of measurements pushed forward along an embedding has its value.
Every isomorphism of models is an embedding.
Equations
- Φ.toEmbedding = { toLocalIsometry := Φ.toLocalIsometry, W_ψ := ⋯, ΦA_one := ⋯, ΦB_one := ⋯ }
Instances For
The embeddings between extensions #
An inert ancilla in a unit vector, as an embedding (BipartiteModel.inert).
Instances For
Associativity of extensions, as an embedding (BipartiteModel.assoc), in a vector e''
that is the product of the two.
Equations
Instances For
A relabelling of the registers, as an embedding (BipartiteModel.relabel), to the
relabelled vector.
Equations
- M.relabelEmb e e' f g he = { toLocalIsometry := M.relabel e e' f g, W_ψ := ⋯, ΦA_one := ⋯, ΦB_one := ⋯ }
Instances For
The exchange of the players in an extension, as an embedding
(BipartiteModel.swapExpand), to the exchanged vector.
Equations
- M.swapExpandEmb e e' he = { toLocalIsometry := M.swapExpand e e', W_ψ := ⋯, ΦA_one := ⋯, ΦB_one := ⋯ }
Instances For
The change of cut, as an embedding (BipartiteModel.recutIsom): the extension along the
regrouped registers into the reading of the original extension.