For the first time, scientists have successfully combined two of the “spookiest” features of quantum mechanics to make a better quantum sensor: entanglement between atoms and delocalization of atoms.“By learning to harness and control all of the spookiness we already know about, maybe we can discover new spooky things about the universe that we haven’t even thought of yet!” — James K. Thompson As described in their paper that was published in the journal Nature on October 19, the Thompson group has combined the spookiness of both entanglement and delocalization to realize a matter-wave interferometer that can sense accelerations with a precision that surpasses the standard quantum limit (a limit on the accuracy of an experimental measurement at a quantum level) for the first time.By doubling down on the spookiness, future quantum sensors will be able to provide more precise navigation, explore for needed natural resources, more precisely determine fundamental constants such as the fine structure and gravitational constants, look more precisely for dark matter, or maybe even one day detect gravitational waves.As graduate student Chengyi Luo explained, “We shine laser beams on the atoms so we actually split each atom’s quantum wave packet in two, in other words, the particle actually exists in two separate spaces at the same time.” Later pulses of laser light then reverse the process bringing the quantum wave packets back together so that any changes in the environment such as accelerations or rotations can be sensed by a measurable amount of interference happening to the two parts of the atomic wave packet, much like is done with light fields in normal interferometers, but here with de’Broglie waves, or waves made of matter.Doubling the Spookiness By learning how to operate a matter-wave interferometer inside of an optical cavity, the team of graduate students led by Chengyi Luo and Graham Greve was then able to take advantage of the light-matter interactions to create entanglement between the different atoms to make a quieter and more precise measurement of the acceleration due to gravity."