We report on the observation of the Meissner effect in bosonic flux ladders
of ultracold atoms. Using artificial gauge fields induced by laser-assisted
tunneling, we realize arrays of decoupled ladder systems that are exposed to a
uniform magnetic field. By suddenly decoupling the ladders and projecting into
isolated double wells, we are able to measure the currents on each side of the
ladder. For large coupling strengths along the rungs of the ladder, we find a
saturated maximum chiral current corresponding to a full screening of the
artificial magnetic field. For lower coupling strengths, the chiral current
decreases in good agreement with expectations of a vortex lattice phase. Our
work marks the first realization of a low-dimensional Meissner effect and,
furthermore, it opens the path to exploring interacting particles in low
dimensions exposed to a uniform magnetic field