Spooky Atomic Clocks

Researchers are hoping to improve high-precision clocks by entangling their atoms.

Einstein called it "spooky action at a distance." Now researchers are using an astonishing property of quantum mechanics called "entanglement" to improve atomic clocks - humanity's most precise way to measure time. Entangled clocks could be as much as 1000 times more stable than their non-entangled counterparts.

This improvement would benefit pilots, farmers, hikers - in short, anyone who uses the Global Positioning System (GPS). Each of the 24+ GPS satellites carries four atomic clocks on board. By triangulating time signals broadcast from orbit, GPS receivers on the ground can pinpoint their own location on Earth.

NASA uses atomic clocks for spacecraft navigation. Geologists use them to monitor continental drift and the slowly changing spin of our planet. Physicists use them to check theories of gravity. An entangled atomic clock might keep time precisely enough to test the value of the Fine Structure Constant, one of the fundamental constants of physics.

"The ability to measure time with very high precision is an invaluable tool for scientific research and for technology," says Alex Kuzmich, a physicist at the Georgia Institute of Technology.

Through its office of Biological and Physical Research, NASA recently awarded a grant to Kuzmich and his colleagues to support their research. Kuzmich has studied quantum entanglement for the last 10 years and has recently turned to exploring how it can be applied to atomic clocks.

Einstein never liked entanglement. It seemed to run counter to a central tenet of his theory of relativity: nothing, not even information, can travel faster than the speed of light. In quantum mechanics, all the forces of nature are mediated by the exchange of particles such as photons, and these particles must obey this cosmic speed limit. So an action "here" can cause no effect "over there" any sooner than it would take light to travel there in a vacuum.