# Paris-Saclay team builds sublattice polarimeter to reconstruct Bloch wavefunctions in photonic lattices

- Published: 2026-11-05 18:30 UTC
- Section: Science › Instruments & experiments
- Tags: sublattice polarimeter, photonic lattices, Bloch wavefunction reconstruction, quantum geometric tensor, Chern numbers, bipartite lattice, spatial light modulator, Brillouin zone, Paris-Saclay University, Euler curvature
- URL: https://realtech.media/news/rt-482374d642a2630add8edbc3_paris_saclay_team/

**The instrument extracts amplitude and phase of crystal orbitals across the Brillouin zone, giving access to the Bloch Hamiltonian, quantum geometric tensor and Chern numbers.**

![Paris-Saclay team builds sublattice polarimeter to reconstruct Bloch wavefunctions in photonic lattices](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/1e72ff0b42b3f5dc.jpg)
*Credit: NASA/JPL-Caltech/S. Stolovy (Spitzer Science Center/Caltech), Wikimedia Commons, Public domain*

Researchers at the Center for Nanoscience and Nanotechnology (Paris-Saclay University, CNRS, Palaiseau, France) have introduced a sublattice polarimeter for photonic lattices. The work, by M. Guillot, J. Bloch, S. Ravets and colleagues, was published in Nature Communications on 4 November 2026. The device enables full reconstruction of the Bloch wavefunctions in bipartite photonic lattices, according to the authors [1].

## The measurement gap

Measuring the electronic structure of crystalline materials is key to understanding their physical properties. Techniques such as angle-resolved photoemission spectroscopy have given detailed insight into the electronic orbitals of natural crystals. The authors note that an equivalent tool for characterizing photonic lattices has been lacking [1].

## How the polarimeter works

The method uses a spatial light modulator to apply controlled phase shifts and attenuations to each sublattice separately. From the resulting measurements the team extracts the amplitude and phase of the crystal orbitals across the Brillouin zone. This includes regions close to band degeneracies [1].

With the wavefunctions reconstructed, the Bloch Hamiltonian becomes experimentally accessible. From it the authors determine the quantum geometric tensor and the band Chern numbers [1].

## Beyond two sublattices

The authors state that the approach is not limited to bipartite lattices. It can be generalized to address multiple internal degrees of freedom. According to the paper, this opens routes to probing complex topological structures experimentally, including trigonal warping, Chern insulators and Euler curvature in multiband settings [1].

The paper reports the method and its demonstration on synthetic photonic lattices. It describes the extension to multiband systems as a possible direction, not a completed measurement [1].

## Sources

1. [Nature Communications](https://doi.org/10.1038/s41467-026-78322-1)

---

Source: RealTech, realtech.media — https://realtech.media/news/rt-482374d642a2630add8edbc3_paris_saclay_team/