Spooky Timing: Quantum-linked photons coordinate clock ticks

1:00pm, September 22, 2004

Check out the closest half-dozen timepieces, and they're almost certain to disagree by at least a few seconds. That variation doesn't cut it for global data networks or fleets of satellites, where even microsecond differences among clocks can wreak havoc. Thanks to sophisticated computations, high-speed electronics, and in some cases relativity theory, the far-flung clocks of those systems can tick within just a few nanoseconds of each other, despite separations of thousands of kilometers.

A new experiment indicates that much tighter synchronization of distant clocks may be possible by exploiting another powerful realm of physics—quantum mechanics. Yanhua Shih and his colleagues of the University of Maryland at Baltimore have tapped a phenomenon known as entanglement (SN: 7/17/04, p. 46: Available to subscribers at Quantum snare entraps key fifth photon), which is one of the weirdest features of that branch of physics.

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