Quantum skyrmion parallelism via metasurface-tailored high-dimensional entanglement

Traditional methods for generating optical skyrmions—topologically non-trivial field configurations—are typically limited to producing a single, deterministic topological state at a time. This paper investigates whether the parallelism inherent in high-dimensional biphoton entanglement can be leveraged to generate multiple, co-existing topological states using a single metasurface device.

The researchers utilize a high-dimensional orbital angular momentum (OAM) entangled photon pair generated via spontaneous parametric down-conversion (SPDC). One photon is passed through a J-plate metasurface, which acts as a spin-orbit coupling device. By introducing a non-local interaction between the entangled OAM states and the metasurface, the topological transformation becomes non-deterministic. The resulting multi-dimensional state hosts several co-existing topologies that are only revealed upon performing OAM projections on the entangled photons.

The study successfully demonstrates the generation of multiple distinct quantum skyrmion states from a single metasurface. By controlling the OAM projection on one of the entangled photons, the researchers can switch between different topological classes in parallel. They experimentally validated this by measuring up to three distinct topological numbers from a single state. Furthermore, by projecting onto superpositions of OAM modes, they accessed an even richer topological landscape, including complex nested skyrmionic structures that were previously inaccessible with single-photon or coherent beam approaches.

This work establishes a new pathway for the compact generation of complex quantum states, significantly enhancing the topological information capacity of photonic systems. By shifting the complexity of state generation from the optics to the post-selection measurement, this approach supports the integration of multi-channel topological networks into miniaturized platforms, which is critical for robust, high-dimensional quantum communication and information processing.