September 2026 ✨: Two measurement bases, woven into one surface. Our new preprint explores a metasurface designed to measure light for quantum key distribution and route the outcomes to four detector channels.
The trick is in the spacing. Patterns for linear and circular polarisation are interwoven at less than half a wavelength. An ordinary propagating-wave aperture mask cannot pick out one measurement basis without also attenuating or disturbing the other.
Yan He and Adetunmise C. Dada explore how this design can build the BB84 measurement into the device itself. Read the paper: Secure Quantum Metasurfaces for Direct Quantum Key Distribution Measurements.