  We analyze the large scale structure and fluctuations of jammed packings of
size disperse spheres, produced in a granular experiment as well as
numerically. While the structure factor of the packings reveals no unusual
behavior for small wavevectors, the compressibility displays an anomalous
linear dependence at low wavectors and vanishes when q -> 0. We show that such
behavior occurs because jammed packings of size disperse spheres have no bulk
fluctuations of the volume fraction and are thus hyperuniform, a property not
observed experimentally before. Our results apply to arbitrary particle size
distributions. For continuous distributions, we derive a perturbative
expression for the compressibility that is accurate for polydispersity up to
about 30%.
