Boundary-field scaling for fast Coulomb-interaction transfer

Determine whether the magnetic fields required at the sender and receiver sites to induce few-mode coherent oscillations in optimized alpha=1 Coulomb-interaction spin chains grow only modestly with system size and remain experimentally tractable for substantially larger systems, despite the increasing spectral radius of the unperturbed Coulomb Hamiltonian.

Background

The paper studies high-fidelity quantum state transfer in spin-1/2 XX chains with power-law couplings, focusing in particular on the alpha=1 Coulomb-interaction regime. For these chains, exceptionally fast transfer is achieved through coherent dynamics involving only a few high-energy eigenstates, enabled by boundary engineering that includes local magnetic fields at the sender and receiver sites.

Numerical observations indicate that the boundary-field strengths needed for the alpha=1 solutions are often close to the largest eigenvalue of the corresponding unperturbed Coulomb Hamiltonian. The authors note that the largest eigenvalue grows with system size, but appears to do so modestly over the studied range. They therefore leave unresolved whether the required boundary fields maintain similarly favorable scaling and experimental feasibility for substantially larger chains.