Researchers Generate Single-Photon Skyrmions Using Nanophotonic Structures

Mapping the total angular momentum of light bound to nanophotonic structures enables the creation of single-photon states with topological textures, according to a paper published in eLight. The work by Amit Kam and colleagues demonstrates the generation of skyrmions in single-photon states mediated by nanophotonic platforms.

Photons serve as carriers of quantum information but conventional methods using polarization or spatial modes often require bulky setups and are sensitive to noise. When light is confined to nanophotonic near-field environments, the distinction between spin angular momentum and orbital angular momentum breaks down.

The two become coupled into a single quantity known as total angular momentum. The researchers employed a plasmonic platform consisting of a gold film patterned with nanoscale features. This setup couples light into surface plasmon polaritons. At subwavelength scales, the near-field interaction binds spin and orbital components into total angular momentum modes.

When a single photon interacts with the nanostructure, its state becomes confined to a specific total angular momentum channel. As the light scatters back into free space, this evolves into a high-dimensional entangled structure linking polarization and spatial modes.

Using quantum state tomography, the team verified that the resulting states exhibit a nontrivial topological texture across the wavefront. The skyrmions generated are local, with topology arising from entanglement between different internal degrees of freedom of a single photon.

This contrasts with nonlocal skyrmions that rely on entanglement between spatially separated photons. Previous realizations of single-photon skyrmions used quantum emitters such as quantum dots, nitrogen-vacancy centers and microrings.