Long-range quantum emitter interactions mediated by a nonlocal metasurface: Application to qubit-qubit entanglement

Scalable quantum technologies demand long-range interactions between many distant quantum emitters (QEs). We introduce nonlocal metasurfaces supporting bound states in the continuum (BICs) as a promising platform to achieve this goal. We show that efficient QE interactions depend almost entirely on emitter-BIC coupling efficiencies ( β factors), which in our system can exceed 80% even without additional mode engineering. These values rival those of one-dimensional waveguides but are achieved here in a geometry that naturally accommodates large two-dimensional QE arrays. Using this platform, we explore entanglement generation between two remote QEs, finding that it develops faster than in free space, is significantly amplified, and persists over separations spanning several emission wavelengths. Optimal inter-QE interactions require large β factors but only moderately small Purcell factors, both within experimentally achievable ranges. Our results establish nonlocal metasurfaces as a practical and scalable platform for leading-edge quantum nanophotonics.