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Even the most accurate timepieces are almost certain to disagree by at least a few seconds. That difference isn't very helpful for a variety of applications such as telecommunications, satellites, wide area networks (WAN's), and global positioning systems that rely heavily on time synchronization. However, thanks to sophisticated computations and high-speed electronics, distant clocks with separations of thousands of miles can be synchronized within a just few nanoseconds--one billionth of a second.

Alejandra Valencia and Giuliano Scarcelli, UMBC Ph.D. physics students, under the mentorship of Dr. Yanhua Shih, conducted an experiment to show that tighter synchronization of distant clocks may be possible by utilizing quantum physics. In Scarcelli's words, “we used the quantum entanglement of photon pairs to achieve clock synchronization.” By sending two entangled photons down optical fibers, the research team was able to detect synchronized events with picosecond--one trillionth of a second--accuracy over a distance of three kilometers. Synchronizing clocks in global positioning satellites to within a picosecond might make it possible to locate objects at the earth's surface within millimeters. Furthermore, this research might have a role in a future space-based observatory.

For an entangled pair of particles, a measurement on one of them instantaneously determines the quantum state of the other. To use this event for synchronization, the two photons are dispatched to detectors at the two stations where the clocks are to be synchronized. If the clocks used to time the detection of many successive pairs are synchronized, the event timings will show the greatest number of coincidences when the records are compared. In cases of mismatch, the clocks can be altered until the detections coincide. This research was first published in Applied Physics Letters, Volume 85, September 2004, page 2655. It was also mentioned in Science News, Volume 166, September 25, 2004.

Valencia and Scarcelli enjoy accomplishing their goals under the guidance of faculty members who are considered among the top-ranking scientists in the field of physics. Since, UMBC is located in the vicinity of NASA and the National Institute of Science and Technology (NIST), not only are they able to utilize the expertise of their own faculty advisors but also network with scientists outside of UMBC. In fact, UMBC is ranked 16th nationwide for NASA funding. Working with faculty of such high credentials can be intimidating; however, both students find the faculty to be “very friendly and helpful.” According to Scarcelli, Dr. Hayden, Physics professor, even invited them over for Thanksgiving dinner.

Having traveled from Italy and Colombia, Scarcelli and Valencia have found UMBC to be a home away from home. Alejandra feels that professors at UMBC treat their students as fellow researchers and value their ideas. "Back home this kind of relationship does not exist, we are not as close to professors as we are here at UMBC," says Scarcelli.