Simulating Lattice Gauge Theories with Ultracold Atoms*

Gauge theories implement fundamental laws of physics by local symmetry constraints. For example, quantum electrodynamics and quantum chromodynamics are both based on gauge theories. However, the equations of gauge theories are usually hard to solve, forming exceptional challenges to supercomputer based numerical procedures.
We developed unique techniques of spin-dependent superlattices, microscopic absorption imaging, and number resolved detection. A new method of deep cooling in optical lattice is realized and a defect-free system is achieved for creating 1250 pairs of entangled atoms. Thanks to these advances, we implemented the Schwinger model with a Hubbard model in deep lattice regime of a 71-site quantum simulator. We observed the interaction and conversion between matter fields and gauge fields and verified Gauss's law. The quantum simulator may be also used to study non-equilibrium lattice gauge systems, false vacuum decay, dynamical transitions related to the topological ?-angle, and thermal signatures of gauge theories under extreme conditions.