Continuous heralding control of vortex beams using quantum metasurface

Heralded detection is widely used in quantum information processing, as it allows real-time tuning the properties of a heralded photon by acting on the heralding photon. With polarization-entangled photon pairs, the authors use a geometric phase metasurface to achieve a remote and continuous control of the vortex states of the heralded photon. Metasurfaces utilize engineered nanostructures to achieve control on all possible dimensions of light, encouraging versatile applications, including beam steering, multifunctional lensing, and multiplexed holograms. Towards the quantum optical regime for metasurfaces, although significant efforts have been put into generating and analyzing specific quantum states, control schemes to further manipulate these quantum states or information are still limited. Here, based on a metasurface, we propose and experimentally demonstrate a continuous heralding scheme to remotely control a vortex beam with high robustness to noise using polarization-entangled photon pairs. Our metasurface entangles polarization and orbital angular momentum (OAM) and the polarization selection on heralding photon erases the which-OAM information on signal photon. It induces an interference of two different OAM states remotely, manifesting a continuous orbital rotation. Our results show that metasurfaces have potential applications in quantum communication and information processing in entangling information with increasing complexity in the content.

Automated summary

In this study, a geometric phase metasurface is used to remotely and continuously control the vortex states of a heralded photon. Metasurfaces, which utilize engineered nanostructures, offer control over different dimensions of light and have versatile applications. By selecting the polarization of the heralding photon, the orbital angular momentum (OAM) of the signal photon can be remotely controlled. This research has important implications for quantum communication and information processing.