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Vestnik Moskovskogo Universiteta Seriya 3 Fizika Astronomiya

On one conjugate object in the symmetric tensor C*-category and the statistics of superselection sectors

Аirat Sitdikov, А. С. Никитин

Published Sep 20, 2023• 1 citation
Publisher

Abstract

In this work, a model of a symmetric tensor 𝐶*-category with conjugation is constructed for the dimension of the object 𝑑 = 3. It is proved that the constructed conjugate object of the category satisfies the conjugation equations. The classes of morphisms between objects of the modeled category are considered and studied, and the algebra of observables in the presence of such an conjugate object is introduced. As an application of the model, we consider the theory of quantum information transfer, where it is necessary to take into account the constraints associated with the superselection rules.

DOI
10.55959/msu0579-9392.78.2340101

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On One Conjugate Object in the Symmetric Tensor C∗\boldsymbol{C}^{\boldsymbol{*}}C∗-Category and the Statistics of Superselection Sectors
The paper presents a model of symmetric tensor C∗C^{*}C∗ -category with conjugation for an object of dimension d=3d=3d=3 . It is proved that the constructed conjugate object of the category satisfies the conjugation equations, and different classes of morphisms between the objects in the modelled category are considered and studied. This category allows for the generalization of the C∗C^{*}C∗ -algebraic model of observables in the presence of superselection rules generated by non-Abelian conjugate charges. As an application of the model, the area of quantum information transfer is explored, where the constraints imposed by the superselection rules need to be taken into account.
In this paper, we consider an extension of the previously proposed algebraic model and study the constraints of non-Abelian superselection rules on the transfer quantum information, taking into account conjugate endomorphism. The procedure of averaging (over the group G=SU(3)G=SU(3)G=SU(3) ) projectors to the basic states of coherent orthogonal subspaces into which the space of two three-level systems decomposes is considered. Main attention is paid to the superselection structure of the algebra of observables 0OG{}^{0}O_{G}0OG​ defined by the Cuntz algebra 0Od=3{}^{0}O_{d=3}0Od=3​ (field algebra) containing 0OG{}^{0}O_{G}0OG​ as a pointwise fixed subalgebra with respect to the action of the gauge group GGG . As an application of the model, we consider the encoding of information using a three-level system and show that information can be transmitted only by those states whose projectors belong to the algebra of observables. These projectors commute with the elements of the representation of the group GGG , and therefore, allow the recipient to restore the obtained information.
We prove a finite-dimensional covariant Stinespring theorem for compact quantum groups. Let G be a compact quantum group, and let T≔Rep(G) be the rigid C*-tensor category of finite-dimensional continuous unitary representations of G. Let Mod(T) be the rigid C*-2-category of cofinite semisimple finitely decomposable T-module categories. We show that finite-dimensional G-C*-algebras can be identified with equivalence classes of 1-morphisms out of the object T in Mod(T). For 1-morphisms X:T→M1, Y:T→M2, we show that covariant completely positive maps between the corresponding G-C*-algebras can be “dilated” to isometries τ: X → Y ⊗ E, where E:M2→M1 is some “environment” 1-morphism. Dilations are unique up to partial isometry on the environment; in particular, the dilation minimizing the quantum dimension of the environment is unique up to a unitary. When G is a compact group, this recovers previous covariant Stinespring-type theorems.
In this paper, we study the influence of nonabelian superselection rules on the transfer of quantum information with the help of qubits on the base of an algebraic model and formulate quantum protocols. We pay the main attention to the superselection structure of the algebra of observables [Formula: see text] defined by the Cuntz algebra [Formula: see text] (a field algebra) that contains [Formula: see text] as a pointwise fixed subalgebra with respect to the action of the gauge group [Formula: see text]. We prove that it is possible to code information only with the help of states such that projectors on them belong to the algebra of observables. These projectors commute with the elements of the representation of the group [Formula: see text], and therefore allow the recipient to restore the obtained information.
The article arXiv:2410.21454 constructed a braided W∗\mathrm{W^*}W∗-tensor category of superselection sectors associated to a net of von Neumann algebras on a suitably geometric poset using localized and transportable endomorphisms. In this article, we construct an equivalent tensor product and braiding using the Connes fusion tensor product without localizing, using ideas from arXiv:1812.04470 for conformal nets. As an application, we prove that the category of superselection sectors associated to the 2D braided quantum spin system constructed from a unitary braided fusion category B\mathcal{B}B in arXiv:2506.19969 is equivalent to Hilb(B)op\mathsf{Hilb}(\mathcal{B})^{\rm op}Hilb(B)op, the opposite of the unitary ind-completion of B\mathcal{B}B, as a braided W∗\mathrm{W^*}W∗-tensor category.
Abstract We study a commutant-closed collection of von Neumann algebras acting on a common Hilbert space indexed by a poset with an order-reversing involution. We give simple geometric axioms for the poset which allow us to construct a braided tensor category of superselection sectors analogous to the construction of Gabbiani and Fröhlich for conformal nets. For cones in R2\mathbb {R}^2R2 R 2 , we weaken our conditions to a bounded spread version of Haag duality and obtain similar results. We show that intertwined nets of algebras have isomorphic braided tensor categories of superselection sectors. Finally, we show that the categories constructed here are equivalent to those constructed by Naaijkens and Ogata for certain 2D quantum spin systems.