Certifying Nonlocal Spin Quantum Entanglement from Local Tunneling Spectra

Abstract:Quantum entanglement is intrinsically nonlocal, whereas tunneling spectroscopy measures one site at a time. We show that this apparent mismatch can be overcome: local tunneling spectra can certify spin entanglement without coherent control or absolute intensity calibration. An exact spin sum rule turns the high-bias conductance into an internal normalization, allowing the inelastic spin-flip weight to place a lower bound on the local quantum Fisher information. Total-spin conservation then fixes the otherwise inaccessible intersite fluctuation, converting two local spectra into a bound on a collective entanglement witness. We incorporate coupling to the substrate through a spectroscopic bound on spin leakage, while a hierarchy of thresholds distinguishes entanglement between the spins from entanglement with their environment. Including instrumental broadening and noise, the resulting certificate holds at a stated confidence level. These results establish a route for extracting nonlocal quantum information from equilibrium local spectroscopy.

Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); Applied Physics (physics.app-ph)

arXiv:2610.24440 [quant-ph]

(or arXiv:2610.24440v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.24440 Focus to learn more arXiv-issued DOI via DataCite

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