Gravity-wave interferometers as quantum-gravity detectors

Nearly all theoretical approaches to the unification of quantum mechanics and 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 any) of the existing models of quantum gravity is correct, But it is generally believed(5) that these quantum space-time effects are too small to be probed by technologies currently available. Here I argue that modern gravity-wave interferometers are sensitive enough to test certain space-time fuzziness models, because quantum space-time effects should provide an additional source of noise in the interferometers that can be tightly constrained experimentally, The noise levels recently achieved in one interferometer(6) are 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 should be achievable with interferometers now under construction.