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FormalConjectures.Paper.MonochromaticQuantumGraph

Monochromatic quantum graphs (inherited vertex colorings) #

This file studies the existence of monochromatic quantum graphs: edge-coloured, edge-weighted complete graphs whose perfect matchings induce vertex colourings, with the property that

In the quantum-optics motivation, such a construction corresponds to generating high-dimensional multipartite GHZ-type states using probabilistic pair sources and linear optics (without additional resources), where interference patterns can be expressed as weighted sums over perfect matchings.

Main questions (informal) #

Formalisation sketch #

A quantum graph with N vertices and D colours can be encoded by a weight function W : EdgeN N D α → α (for a coefficient domain α).

For each assignment of vertex indices ι : V N → Fin D, we define a perfect-matching sum pmSumN N D W ι (a sum over perfect matchings, where each matching contributes the product of the corresponding edge weights determined by ι). The equation system EqSystemN N D W requires

pmSumN N D W ι = 1 iff ι is constant (all entries equal), and 0 otherwise.

The open conjectures in this file ask for non-existence/existence of such W over various coefficient domains (e.g. , , , and restricted integer weights).

References #

@[reducible, inline]

Vertices of $K_N$.

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    Edge label for $K_N$ with endpoint indices in Fin D.

    We intend to build edges only with u < v (so undirected edges are represented once), and our enumeration always pairs the first vertex in an ordered list with a later vertex.

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      def MonochromaticQuantumGraph.instDecidableEqEdgeN.decEq {N✝ D✝ : } (x✝ x✝¹ : EdgeN N✝ D✝) :
      Decidable (x✝ = x✝¹)
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        @[reducible, inline]

        Weights on edges.

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          def MonochromaticQuantumGraph.mkEdge {N D : } (u v : V N) (i j : Fin D) :
          EdgeN N D

          Helper: build an EdgeN from endpoints and endpoint indices.

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            def MonochromaticQuantumGraph.allEqualList {N D : } (ι : V NFin D) (L : List (V N)) :

            Chain-equality along a list of vertices.

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              def MonochromaticQuantumGraph.allEqual {N D : } (ι : V NFin D) :

              All indices equal on Fin N (using the canonical ordered vertex list).

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                def MonochromaticQuantumGraph.pmSumListAux {α : Type} [Semiring α] {N D : } (W : WeightsN N D α) (ι : V NFin D) :
                List (V N)α

                Auxiliary perfect-matching sum on a vertex list, using a fuel parameter n for termination.

                When called as pmSumListAux W ι L.length L, this computes the weighted sum over all perfect matchings on the vertices in L. The recursion pairs the head vertex with each later vertex and recurses on the remaining vertices.

                For lists of odd length, there are no perfect matchings and the value is 0.

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                  def MonochromaticQuantumGraph.pmSumList {α : Type} [Semiring α] {N D : } (W : WeightsN N D α) (ι : V NFin D) (L : List (V N)) :
                  α

                  Perfect-matching sum on a list: run pmSumListAux with fuel = L.length.

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                    def MonochromaticQuantumGraph.pmSumN {α : Type} [Semiring α] (N D : ) (W : WeightsN N D α) (ι : V NFin D) :
                    α

                    The perfect-matching sum for $K_N$: use the canonical ordered vertex list vertices N.

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                      def MonochromaticQuantumGraph.EqSystemN {α : Type} [Semiring α] (N D : ) (W : WeightsN N D α) :

                      The monochromatic quantum graph equation system for $K_N$.

                      For every index assignment $\iota : V_N \to \mathrm{Fin}\, D$, the perfect-matching sum equals $1$ if $\iota$ is constant (monochromatic inherited vertex colouring), and equals $0$ otherwise.

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                              Bogdanov: for $N = 4$ and all $D \geq 4$, no solution exists over $\mathbb{R}_{\geq 0}$.

                              Bogdanov: for all even $N \geq 6$ and $D \geq 3$, no solution exists over $\mathbb{R}_{\geq 0}$.

                              For $N = 4$ and $D = 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 4$ and all $D \geq 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 6$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 6$ and $D = 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 6$ and $D = 5$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 6$ and $D = 6$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 6$ and all $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 8$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 8$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 5$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 6$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 7$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 8$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 9$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 10$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 12$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 14$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 16$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              theorem MonochromaticQuantumGraph.eqSystem_no_solution_ge6_ge3 :
                              True ∀ (N D : ), N 6Even ND 3¬∃ (W : WeightsN N D ), EqSystemN N D W

                              For all even $N \geq 6$ and $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{C}$?

                              For $N = 4$ and $D = 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 4$ and all $D \geq 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 6$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 6$ and all $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 8$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 8$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 10$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 10$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              theorem MonochromaticQuantumGraph.eqSystem_no_solution_ge6_ge3_real :
                              True ∀ (N D : ), N 6Even ND 3¬∃ (W : WeightsN N D ), EqSystemN N D W

                              For all even $N \geq 6$ and $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{R}$?

                              For $N = 4$ and $D = 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 4$ and all $D \geq 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 6$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 6$ and all $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 8$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 8$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 10$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              For $N = 10$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              theorem MonochromaticQuantumGraph.eqSystem_no_solution_ge6_ge3_int :
                              True ∀ (N D : ), N 6Even ND 3¬∃ (W : WeightsN N D ), EqSystemN N D W

                              For all even $N \geq 6$ and $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$?

                              theorem MonochromaticQuantumGraph.eqSystem4_no_solution_d4_trinary_int :
                              True ¬∃ (W : WeightsN 4 4 ), (∀ (e : EdgeN 4 4), W e = -1 W e = 0 W e = 1) EqSystemN 4 4 W

                              For $N = 4$ and $D = 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem4_no_solution_ge4_trinary_int :
                              True D4, ¬∃ (W : WeightsN 4 D ), (∀ (e : EdgeN 4 D), W e = -1 W e = 0 W e = 1) EqSystemN 4 D W

                              For $N = 4$ and all $D \geq 4$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem6_no_solution_d3_trinary_int :
                              True ¬∃ (W : WeightsN 6 3 ), (∀ (e : EdgeN 6 3), W e = -1 W e = 0 W e = 1) EqSystemN 6 3 W

                              For $N = 6$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem6_no_solution_ge3_trinary_int :
                              True D3, ¬∃ (W : WeightsN 6 D ), (∀ (e : EdgeN 6 D), W e = -1 W e = 0 W e = 1) EqSystemN 6 D W

                              For $N = 6$ and all $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem8_no_solution_d3_trinary_int :
                              True ¬∃ (W : WeightsN 8 3 ), (∀ (e : EdgeN 8 3), W e = -1 W e = 0 W e = 1) EqSystemN 8 3 W

                              For $N = 8$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem8_no_solution_d10_trinary_int :
                              True ¬∃ (W : WeightsN 8 10 ), (∀ (e : EdgeN 8 10), W e = -1 W e = 0 W e = 1) EqSystemN 8 10 W

                              For $N = 8$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem10_no_solution_d3_trinary_int :
                              True ¬∃ (W : WeightsN 10 3 ), (∀ (e : EdgeN 10 3), W e = -1 W e = 0 W e = 1) EqSystemN 10 3 W

                              For $N = 10$ and $D = 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem10_no_solution_d10_trinary_int :
                              True ¬∃ (W : WeightsN 10 10 ), (∀ (e : EdgeN 10 10), W e = -1 W e = 0 W e = 1) EqSystemN 10 10 W

                              For $N = 10$ and $D = 10$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?

                              theorem MonochromaticQuantumGraph.eqSystem_no_solution_ge6_ge3_trinary_int :
                              True ∀ (N D : ), N 6Even ND 3¬∃ (W : WeightsN N D ), (∀ (e : EdgeN N D), W e = -1 W e = 0 W e = 1) EqSystemN N D W

                              For all even $N \geq 6$ and $D \geq 3$, does there exist no solution to the monochromatic quantum graph equation system over $\mathbb{Z}$ with weights in $\{-1, 0, 1\}$?