Quantum entanglement underpins a broad range of fundamental physical effects and serves as an essential resource in various quantum applications. In optics, the most common source of entangled photons is based on the spontaneous parametric down-conversion process in quadratically nonlinear materials. Dramatic enhancements of nonlinear light-matter interactions were achieved in nanofabricated structures with subwavelength thickness known as metasurfaces, which are also bringing advances to the field of quantum optics; yet the generation with metasurfaces of photons entangled in spatial and other degrees of freedom remained outstanding.

We report the first experimental generation of spatially entangled photon pairs from a metasurface incorporating a lithium niobate nonlinear thin film that supports high-quality-factor nonlocal resonances. We also demonstrate an original approach to generating polarisation-entangled states, thereby overcoming the fundamental limitation of unstructured lithium niobate crystals that predominantly emit photon pairs with a fixed linear polarisation. These results pave the way toward the miniaturization of various roomtemperature quantum devices with applications such as quantum imaging, quantum communication, and quantum sensing.

Dr. Jinyong Ma received his Bachelor’s and Master’s degrees from Huazhong University of Science and Technology. He completed his Ph.D. in Prof. Ping Koy Lam’s group (RSPhys) in 2020 and then joined Prof. Jack Harris’s group at Yale University as a postdoctoral associate until 2021. His research was focused on the field of quantum optomechanics and optical levitation.

Jinyong is currently a research fellow in Prof. Andrey Sukhorukov’s group (EME, RSPhys) and a research program manager at the ARC Centre of Excellence for Transformative Meta-Optical Systems. He is now working on the generation and detection of entangled photon pairs from nonlinear metasurfaces.

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