Tunable Mode Entanglement: Topological Su–Schrieffer–Heeger (SSH) Chain with an Embedded Aharonov–Bohm Quantum Ring

Abstract

We investigate a variant of the SSH model consisting of an SSH chain with an embedded Aharonov-Bohm quantum ring. The embedded ring gives rise to domain wall states whose energy levels are in the band gap. The dependence of some of the states on the ring's magnetic flux provides a mechanism to control the entanglement between the two SSH edge fermion modes. The concurrence between the edge modes depends periodically on the magnetic flux. In the deep topological zone, for appropriate values of the flux, the concurrence reaches the extreme values of 0 and 1, corresponding to vanishing entanglement and to maximum entanglement. Therefore, the QR-SSH system offers a tuning mechanism that can be used either as an entanglement modulator or as an entanglement switch.

Symmetry-resolved entanglement: general considerations, calculation from correlation functions, and bounds for symmetry-protected topological phases

“…The configurational entropy, on the other hand, is a special case of the operational entanglement entropy-first introduced by Wiseman and Vacaro [3] as the entanglement extractable from a quantum many-body system of indistinguishable particles and transferable to a quantum register-for the case of a bipartition of a pure quantum state. The separation of the entanglement entropy in the presence of particle number conservation into these two components has been used to study many-body physics [4,5,[7][8][9][10][11][12][13], quantum field theories [14][15][16][17][18], topological systems [6,[19][20][21][22][23] and synthetic quantum matter [24].…”

“…On the other hand, nontrivial states generally have non-zero lower entanglement bounds, related to their topological invariant. This makes symmetry-resolved entanglement an important probe for topologically nontrivial states [6,[19][20][21][22][23].…”