Reviewed by Lexie CornerMar 13 2025
Researchers from Hong Kong and the UK recently introduced a new method for using metasurfaces to create quantum holograms. By carefully planning the orientations of nanostructures within the metasurface, they created a quantum hologram where polarization and holographic information are intertwined.
Polarization and holographic information become entangled in a quantum hologram. Holographic letters demonstrate entanglement through the polarization of paired photons. By selecting different polarizer orientations for one photon, specific letters in the hologram could be selectively erased, demonstrating precise control over the entangled holographic information. Image Credit: J. Li (University of Exeter)
Quantum entanglement, a fundamental phenomenon in nature, is one of the most intriguing features of quantum mechanics. It describes a relationship between two particles where measuring the properties of one instantly reveals those of the other, no matter the distance between them. This phenomenon has practical applications in fields like quantum communication and computing.
Entanglement is often generated using a nonlinear crystal, which employs spontaneous parametric down-conversion (SPDC) to create photon pairs with entangled polarizations. For example, if one photon is measured as horizontally polarized, the other will always be vertically polarized, and vice versa.
At the same time, metasurfaces, which are ultrathin optical devices, enable the creation of high-resolution holograms and can encode large amounts of data. By combining metasurfaces with nonlinear crystals, researchers are exploring a promising approach to improve the generation and control of entangled photon states.
We have demonstrated that metasurfaces serve as a versatile platform for generating quantum holograms. The entanglement property of these quantum holograms is further revealed by projecting one photon onto various polarization states corresponding to interference effects observed elsewhere.
Jensen Li, Professor and Study Senior Author, Computational Engineering and Metamaterials, University of Exeter
The method offers a compact and flexible approach, which is difficult to achieve with traditional materials. As a demonstration, the researchers successfully created four holographic letters—“H,” “V,” “D,” and “A”—entangled with the polarization of paired photons.
The entangled holographic information could be controlled by selectively erasing specific letters in the hologram. This was done by adjusting the polarizer orientations for a single photon.
By encoding information in both the letters and polarization states, this research holds potential applications beyond its fundamental importance, particularly in fields like quantum communication.
With more complex entanglement patterns, we may be able to increase the information capacity for quantum key distribution, which is a secure way to communicate. We believe that metasurfaces can significantly reduce the size of quantum optical systems, making this technology much more practical for everyday use.
Hong Liang, Study Co-Author, University of Exeter
The researchers also suggest using metasurfaces for anti-counterfeiting applications. The complex relationship between the letters, polarization states, and the relative phase profile of different holograms creates a unique pattern. This pattern is difficult to replicate, enhancing security against forgery, in addition to the inherent difficulty of replicating the metasurface itself.
Our demonstration can also be interpreted as a quantum eraser at the holographic level. Compared to the traditional double-slit quantum eraser, our setup replaces two slits with two holograms and obtains “which-hologram information” from the polarization of entangled photons. Erasing this information now has a concrete effect, as illustrated by erasing holographic letters.
Wai Chun Wong, Study Co-Author, University of Exeter
This study demonstrates how quantum effects can be practically applied in modern nanofabrication technology. Despite their ultrathin nature, metasurfaces enable complex quantum operations that would typically require elaborate optical setups. This achievement not only broadens the understanding of quantum mechanics but also provides valuable insights into quantum information processing.
Journal Reference:
Liang, H., et al. (2025) Metasurface-enabled quantum holograms with hybrid entanglement. Advanced Photonics. doi.org/10.1117/1.AP.7.2.026006.