Observation of Brane Parity Order in Programmable Optical Lattices

The Mott-insulating phase of the two-dimensional (2D) Bose-Hubbard model is expected to be characterized by a nonlocal brane parity order. Parity order captures the presence of microscopic particle-hole fluctuations and entanglement, whose properties depend on the underlying lattice geometry. We realize 2D Bose-Hubbard models in dynamically tunable lattice geometries, using neutral atoms in a passively phase-stable tunable optical lattice in combination with programmable site-blocking potentials. We benchmark the performance of our system by single-particle quantum walks in the square, triangular, kagome, and Lieb lattices. In the strongly correlated regime, we microscopically characterize the geometry dependence of the quantum fluctuations and experimentally validate brane parity as a proxy for the nonlocal order parameter signaling the superfluid-to-Mott-insulating phase transition.