Observation of gauge invariance in a 71site BoseHubbard quantum simulator
Abstract
The modern description of elementary particles, as formulated in the standard model of particle physics, is built on gauge theories^{1}. Gauge theories implement fundamental laws of physics by local symmetry constraints. For example, in quantum electrodynamics Gauss's law introduces an intrinsic local relation between charged matter and electromagnetic fields, which protects many salient physical properties, including massless photons and a longranged Coulomb law. Solving gauge theories using classical computers is an extremely arduous task^{2}, which has stimulated an effort to simulate gaugetheory dynamics in microscopically engineered quantum devices^{36}. Previous achievements implemented densitydependent Peierls phases without defining a local symmetry^{7,8}, realized mappings onto effective models to integrate out either matter or electric fields^{912}, or were limited to very small systems^{1316}. However, the essential gauge symmetry has not been observed experimentally. Here we report the quantum simulation of an extended U(1) lattice gauge theory, and experimentally quantify the gauge invariance in a manybody system comprising matter and gauge fields. These fields are realized in defectfree arrays of bosonic atoms in an optical superlattice of 71 sites. We demonstrate full tunability of the model parameters and benchmark the mattergauge interactions by sweeping across a quantum phase transition. Using highfidelity manipulation techniques, we measure the degree to which Gauss's law is violated by extracting probabilities of locally gaugeinvariant states from correlated atom occupations. Our work provides a way to explore gauge symmetry in the interplay of fundamental particles using controllable largescale quantum simulators.
 Publication:

Nature
 Pub Date:
 November 2020
 DOI:
 10.1038/s4158602029108
 arXiv:
 arXiv:2003.08945
 Bibcode:
 2020Natur.587..392Y
 Keywords:

 Condensed Matter  Quantum Gases;
 High Energy Physics  Lattice;
 High Energy Physics  Phenomenology;
 Physics  Atomic Physics;
 Quantum Physics
 EPrint:
 doi:10.1038/s4158602029108