The renowned physicist Freeman Dyson suggested that a hypothetical detector sensitive enough to observe a single graviton would be so massive that the detector itself would collapse into a black hole. But what if we’re going about this the wrong way? What if instead of trying to find just one graviton, we search for a telltale sign that only a group of them can create? That’s what three researchers proposed in a paper from October of 2020. The physicists were inspired by Brownian motion, which describes how particles in a fluid bounce around randomly. If gravity really is carried by bosons, then maybe they move around randomly too, creating a sort of “noise” or fuzziness that existing gravitational wave detectors like LIGO can suss out. Of course, the noise has to be pronounced enough for LIGO to notice. It’s a bit beyond the scope of this episode but just know that waves like light can come in different quantum states— in fact, LIGO uses light in a “squeezed” state for enhanced sensitivity The researchers calculated that gravitational waves in different quantum states would produce different amounts of noise.
