F. Marino

On a lab bench sits a laser trap — an invisible hand that holds a glass bead the size of a bacterium in midair. Next to it is a mirrored cavity where light bounces between two reflective walls. Scientists made the bead and the light exchange quantum entanglement: their states are now linked so that measuring one instantly reveals the other.

Two tiny weights, each about the mass of a grain of sand, hang in the dark at a temperature colder than deep space. They don't touch, but an invisible thread connects them — gravity. The experiment physicists are now building aims to catch the moment when that thread tugs one weight due to the motion of the other.