For most people, quantum mechanics seems pretty weird. Take the principle of delocalization, which states that a quantum particle can, in some sense, exist simultaneously in multiple locations. Then there’s entanglement: the invisible connection between particles that allows the state of one particle to determine that of another, even across vast distances. But as weird as delocalization and entanglement are, they can be very useful, and physicists at JILA in Boulder, Colorado, US have now incorporated both into a single quantum sensor for the first time. The new sensor can detect accelerations below the usual limit set by noise arising from quantum fluctuations, providing a sharper tool for exploring fundamental physics as well as for applications such as navigation and Earth monitoring.
