A new tool lets physicists map quantum geometry in light-based crystals

Physicists have developed a “sublattice polarimeter” to fully reconstruct the behavior of light within photonic lattices, a tool previously unavailable for these light-based crystals. Unlike existing methods for natural crystals, the new technique extracts the “amplitude and phase of the crystal orbitals” across the “Brillouin zone,” allowing access to the “quantum geometric tensor” and “band Chern numbers.” This advancement enables experimental probing of complex topological structures like “trigonal warping, Chern insulators and Euler curvature” in more complex systems, going beyond simple energy bands to understand the geometry of a system’s eigenstates. The work introduces and experimentally realizes a method that provides direct access to both the quantum metric and the Berry curvature, including near band degeneracies. The ability to fully map the behavior of light within artificial photonic lattices moved closer to reality with the development of a technique for…