Gravity-wave interferometers as quantum-gravity detectors

Nearly all theoretical approaches to the unification of quantum mechanics a nd gravity predict(1-4) that, at very short distance scales, the classical picture of space-time breaks down, with space-time becoming somewhat 'fuzzy ' (or 'foamy'). The properties of this fuzziness and the length scale that characterizes its onset are potentially a means for determining which (if a ny) of the existing models of quantum gravity is correct, But it is general ly believed(5) that these quantum space-time effects are too small to be pr obed by technologies currently available. Here I argue that modern gravity- wave interferometers are sensitive enough to test certain space-time fuzzin ess models, because quantum space-time effects should provide an additional source of noise in the interferometers that can be tightly constrained exp erimentally, The noise levels recently achieved in one interferometer(6) ar e sufficient to rule out values of the length scale that characterizes one of the space-time fuzziness models down to the Planck length (similar to 10 (-35) m) and beyond, while the sensitivity required to test another model s hould be achievable with interferometers now under construction.