26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Metasurface polarisation-entanglement distribution with orbital angular momentum multiplexing

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral ANZOS | Photonics and Optics (ANZCOP)

Speaker

Saniya Shinde (ARC Center of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, ACT 2601, Australia; Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Straße 15, 07745 Jena, Germany)

Description

Multiparty quantum networks require distribution of entanglement amongst various users. Currently, such networks operating with photons over free space require bulky optical components with interferometric stability for entanglement multiplexing [1]. For a broader use of such technologies, there is a need to integrate the functionality into a compact integrated platform. Recently, linear metasurfaces with optimized nanopatterns on thin films were developed for entanglement distribution [2]. However, these still relied on biphotons produced from bulk nonlinear crystals as input. On the other hand, nonlinear metasurfaces emerged as compact quantum sources that can produce tuneable entangled photon states defined by the metasurface resonance [3]. However, the potential for direct generation of entanglement distribution from metasurfaces remained unexplored.

We suggest an integrated scheme for flexible free-space entanglement distribution based on a nonlinear metasurface that directly generates photons with tuneable and distinct polarisation entanglement between different pairs of orbital angular momentum (OAM) channels, which can then be directed to individual recipients. We show theoretically that this can be achieved by illuminating the metasurface with the laser pump that is shaped as a coherent superposition of multiple OAM modes, each with a particular polarisation. Then, one can generate the required OAM-polarisation photon-pair entanglement through the spontaneous parametric down-conversion process inside the ultrathin metasurface. The polarisation entanglement between OAM channels can be further controlled by tuning the pump laser wavelength relative to the metasurface resonance. We note that the pump shaping can be realized using established principles of metasurface polarisation holograms, leading to ultra-compact all-metasurface quantum sources for entanglement distribution in multi-user quantum network applications without post-processing.

[1] Hua-Ying Liu et al., Advanced Science 13, e21923 (2026).
[2] Yajun Gao et al., Phys. Rev. Lett. 136, 023601 (2026).
[3] Jinyong Ma et al., Sci. Adv. 11, eadu4133 (2025).