News & Seminars | HKUST Department of Physics

Abstract
Optical metasurfaces, composed of nanostructured layers, possess remarkable capabilities in light modulation, especially in hybridizing various light degrees of freedom (DoFs) including wavelength, polarization, and orbital angular momentum (OAM). Metasurfaces offer unparalleled versatility in light structuring and hologram generation, enabling optical components that surpass the limits of conventional approaches. Leveraging the precise control offered by tailor-made metasurfaces, researchers have recently explored innovative applications in quantum optics, including high-dimensional entangled state generation, quantum interference control, as well as quantum state tomography, and quantum algorithm implementation. To further integrate the versatile control of metasurfaces in quantum optics, I utilize metasurfaces to explore the manipulation of two-photon interference and the generation of hybrid entangled states.
Firstly, I present the theoretical framework to analyze two-photon interference on a non-Hermitian metasurface. Within this framework, I propose a novel effect termed one-sided destructive quantum interference based on a metasurface with unidirectional zero reflection. This discovery enables quantum interference to occur and be controlled on only one side of the metasurface but not the other side. Next, we extend the port of quantum interference from physical paths to polarization DoF and introduce the polarization coincidence image on a metasurface, where anticorrelated, correlated, and intermediate coincidence patterns are observed. With the polarization response revealed by the coincidence signal, we further propose single-shot Jones matrix imaging based on quantum interference. With the correlation measurement between an unknown object and reference panels with known Jones matrices, we retrieve up to 3 DoFs in just one measurement, greatly reducing the characterization steps.

In the meantime, to investigate hybrid entanglement enabled by metasurfaces, I build a polarization-entangled photon pair source. Utilizing a metasurface with spin-orbit coupling, I achieve hybrid entanglement between the OAM of the signal photon and the polarization of the idler photon. This allows remote and continuous control of the signal photon’s vortex state, showcasing the potential of metasurfaces for high-dimensional quantum communication. Additionally, I extend to polarization-hologram hybrid entanglement with spin-dependent metasurface hologram, enabling a dual-channel heralded quantum hologram. The signal hologram display can be switched between two channels by selecting the idler photon’s polarization, with exceptional robustness to environmental noise and high information capacity. Furthermore, with a more sophisticated metasurface design to control the interference between the two holographic states, a quantum holographic eraser is proposed and demonstrated. Two holographic channels, acting as two abstract interfering paths, are marked with the idler polarization. This marking makes the which-hologram-path accessible, revealing the particle nature of the signal photon. However, using an eraser to select the idler polarization erases the which-path information, revealing the wave nature of the signal photon, manifested as selective erasure on the holographic contents. The implementation of the quantum holographic eraser represents a significant leap forward in metasurface technology’s ability to manipulate and control quantum holographic information, opening up new avenues for diverse applications in quantum communication and information processing.