A laboratory experiment reports that one metasurface can help reveal multiple topological states encoded in high-dimensional entangled light. By selecting different orbital angular momentum, or OAM, modes, heralded measurements exposed up to three distinct states from a single device. Six tested J-plate settings produced reported Skyrmion numbers of -4.99, -1.99, -0.98, 0.97, 1.99 and 4.99, which the study treats as six topological classes.
The document is an arXiv version 1 preprint in the quant-ph category dated 26 August 2026.
The optical recipe
The source was a pair of OAM-entangled photons generated by spontaneous parametric down-conversion, a process used to produce paired photons, in a Type-I nonlinear crystal. A 405-nanometre Gaussian laser pumped the crystal, producing photons at 810 nanometres.
One photon passed through a J-plate metasurface that linked polarization with OAM. The plate assigned polarization-dependent topological charges, labelled m and n, to the horizontal and vertical components. Photon-A OAM projections onto individual modes or superpositions then selected different hybrid states.
The apparatus measured those states using joint polarization projections on photon A and OAM projections on photon B. The resulting data were used to reconstruct density matrices through constrained linear inversion and least-squares fitting with physical-state constraints.
What the measurements revealed
The main topological readout was the Skyrmion number, N, a numerical marker for the topology of a reconstructed light field. In the six-setting test, N took values close to -5, -2, -1, 1, 2 and 5, with the reported results listed as -4.99, -1.99, -0.98, 0.97, 1.99 and 4.99.
A single-state projection example showed how different OAM choices could select different outcomes. For modes 1, 0 and 2, respectively, the reported values were 0.03 plus or minus 0.43 x 10^-4, 1.99 plus or minus 0.12 x 10^-5, and -1.99 plus or minus 0.13 x 10^-4. The three results included a near-zero value, a positive value near 2 and a negative value near -2.
The researchers also tested superpositions, in which several spatial modes contribute to the measured state. For the example labelled (m, n) = (0, -1), the reported full-field topological number was N = -2.87 plus or minus 0.38. A later result labelled (m, n) = (0, 2) gave N = -2.98 plus or minus 0.25.
Reading the result in context
For the (0,1) J-plate row, the reported concurrence was 0.76, fidelity was 0.87, purity was 0.78 and the Skyrmion number was 0.97. The table marked its uncertainty columns with plus or minus 10^-4.
Uncertainties in quantities derived from the reconstructed density matrices were estimated by Monte Carlo propagation of statistical Poissonian photon-count errors. The supplementary topological analysis also averaged contour estimates over 400 rotated choices of the polarization basis and used the spread across those choices as an uncertainty estimate.
The evidence is limited to the optical settings and projections that were tested. Six J-plate metasurfaces were characterized, while the superposition demonstrations used selected OAM projections and two illustrative configurations rather than a systematic survey of arbitrary spatial bases.
Photon-pair counts, repeat counts and a formal sample-size rationale were not reported, and there was no randomized or conventional control arm. The work therefore does not directly quantify an advantage over single-photon or coherent-beam approaches.
The experiment did not test information transmission, network operation, communication throughput, mode sorting, propagation robustness or information-processing performance. Source generation and the J-plate were also separate components, rather than a single integrated source-and-device system.
The supplementary analysis notes that noise and low-signal regions limit precise Skyrmion-number quantification and can make direct surface integration sensitive to threshold choices.
The practical questions remain
The authors interpret the demonstration as a possible route to compact generation of high-dimensional quantum states carrying multiple topologies. They identify practical mode sorting and integrated lithium-niobate nonlocal metasurfaces as future directions, but those steps were proposed rather than demonstrated here.
Study-supporting data were stated to be available from the authors upon reasonable request, and the authors reported no conflict of interest.
Paper data and sources
Original title: Quantum skyrmion parallelism via metasurface-tailored high-dimensional entanglement
Authors: Pedro Ornelas, Ramona Bedford, Fazilah Nothlawala et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-26
DOI: Not available
Original paper · Full text