In quantum information theory, maximally entangled states, specifically
locally maximally entangled (LME) states, are essential for quantum protocols.
While many focus on bipartite entanglement, applications such as quantum error
correction and multiparty secret sharing rely on multipartite entanglement.
These LME states naturally appear in the invariant subspaces of tensor products
of irreducible representations of the symmetric group $S_n$, called Kronecker
subspaces, whose dimensions are the Kronecker coefficients. A Kronecker
subspace is a space of multipartite LME states that entangle high-dimensional
Hilbert spaces. Although these states can be derived from Clebsch-Gordan
coefficients of $S_n$, known methods are inefficient even for small $n$. A
quantum-information-based alternative comes from entanglement concentration
protocols, where Kronecker subspaces arise in the isotypic decomposition of
multiple copies of entangled states. Closed forms have been found for the
multiqubit $W$-class states, but not in general. This thesis extends that
approach to any multiqubit system. We first propose a graphical construction
called W-state Stitching, where multiqubit entangled states are represented as
tensor networks built from $W$ states. By analyzing the isotypic decomposition
of copies of these graph states, corresponding graph Kronecker states can be
constructed. In particular, graph states of generic multiqubit systems can
generate any Kronecker subspace. We explicitly construct bases for three- and
four-qubit systems and show that the W-stitching technique also serves as a
valuable tool for multiqubit entanglement classification. These results may
open new directions in multipartite entanglement resource theories, with
bipartite and tripartite $W$ states as foundational elements, and asymptotic
analysis based on Kronecker states.

Este artículo explora los viajes en el tiempo y sus implicaciones.

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