<p>This work establishes a direct operational connection between the entanglement structures of specific three-qubit states (i.e., multipartite entanglement) and their corresponding topological links. We investigate the symmetric <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mid W\overline{W} \rangle \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>∣</mo> <mi>W</mi> <mover> <mi>W</mi> <mo>¯</mo> </mover> <mrow> <mo stretchy="false">⟩</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> state and the asymmetric <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mid \text {Star} \rangle \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>∣</mo> <mtext>Star</mtext> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> state through local projective measurements on individual qubits. The post-measurement states are analyzed via their Schmidt rank to characterize residual bipartite entanglement. For the symmetric <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\mid W\overline{W} \rangle \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>∣</mo> <mi>W</mi> <mover> <mi>W</mi> <mo>¯</mo> </mover> <mrow> <mo stretchy="false">⟩</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> state, measurement of any qubit consistently results in a non-maximally entangled post-measurement state (Schmidt rank 2), analogous to the behavior of a <i>3-Hopf link</i> structure, where cutting any ring leaves the remaining two nontrivially linked. On the other hand, the <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mid \text {Star} \rangle \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>∣</mo> <mtext>Star</mtext> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> state exhibits a context-dependent fragility. Its behavior predominantly mirrors that of a <i>3-link chain</i> where severing the central qubit decouples the system, while cutting an outer qubit often preserves a residual link. Crucially, for specific measurement outcomes, the <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\mid \text {Star} \rangle \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>∣</mo> <mtext>Star</mtext> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> state also exhibits the defining property of the <i>Borromean rings</i>, where the loss of one qubit completely disentangles the remaining two. This analysis provides a concrete interpretation of topological linking structures as a resource for characterizing distributed entanglement and its resilience under local measurement operations, revealing that a single quantum state can contextually embody multiple distinct topological analogues.</p>

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Symmetric and asymmetric tripartite states under the lens of entanglement splitting and topological linking

  • Sougata Bhattacharyya,
  • Sovik Roy

摘要

This work establishes a direct operational connection between the entanglement structures of specific three-qubit states (i.e., multipartite entanglement) and their corresponding topological links. We investigate the symmetric \(\mid W\overline{W} \rangle \) W W ¯ state and the asymmetric \(\mid \text {Star} \rangle \) Star state through local projective measurements on individual qubits. The post-measurement states are analyzed via their Schmidt rank to characterize residual bipartite entanglement. For the symmetric \(\mid W\overline{W} \rangle \) W W ¯ state, measurement of any qubit consistently results in a non-maximally entangled post-measurement state (Schmidt rank 2), analogous to the behavior of a 3-Hopf link structure, where cutting any ring leaves the remaining two nontrivially linked. On the other hand, the \(\mid \text {Star} \rangle \) Star state exhibits a context-dependent fragility. Its behavior predominantly mirrors that of a 3-link chain where severing the central qubit decouples the system, while cutting an outer qubit often preserves a residual link. Crucially, for specific measurement outcomes, the \(\mid \text {Star} \rangle \) Star state also exhibits the defining property of the Borromean rings, where the loss of one qubit completely disentangles the remaining two. This analysis provides a concrete interpretation of topological linking structures as a resource for characterizing distributed entanglement and its resilience under local measurement operations, revealing that a single quantum state can contextually embody multiple distinct topological analogues.