KentuckyFC writes "While preparing for the job of US Secretary of Energy in the incoming Obama administration (and being director of the Lawrence Berkeley National Laboratory and a Nobel Prize winner to boot), Steven Chu has somehow found time to make a major breakthrough in the world of atom interferometry. One measure of an interferometer's sensitivity is the area that its arms enclose. Chu and colleagues have found a way to increase this area by a factor of 2,500 by canceling out the noise introduced by lasers, which work as beam splitters sending atoms down different arms (abstract). One thing this makes possible is the use of different types of atoms in the same interferometer, allowing a new generation of tests of the equivalence principle. (This is the assumption that the m in F=ma and the m's in F= Gm1.m2/r^2 are the same thing). Let's hope he's got equally impressive breakthroughs planned for his encore as US Secretary of Energy."