“If we’re successful, these optical clocks would provide a 100x increase in precision, or decrease in timing error, over existing microwave atomic clocks, and demonstrate improved holdover of nanosecond timing precision from a few hours to a month. However, the laboratory models are very complex to operate, requiring the transition “to small and robust versions that can operate outside the lab,” program manager at the DARPA Defense Sciences Office, Tatjana Curcic said. The program aims to replicate the agency’s multi-year work in the field, which has produced laboratory models of far more accurate optical atomic clocks - with a longer period of accuracy - than current atomic clocks. The DARPA-sponsored four-year Robust Optical Clock Network program seeks to develop an optical atomic clock that uses light instead of the microwave to measure the change. Optical Atomic ClockĪ conventional atomic clock uses a microwave beam to measure the frequency of change in an atom’s energy state. The new clock will make the system less reliant on GPS, which is vulnerable to spoofing and jamming in contested environments. The agency aims to develop an alternative to the present GPS satellite-based atomic clock that provides “nanosecond (one billionth of a second) timing accuracy” for platforms such as “missiles, sensors, aircraft, ships, and artillery.” "Our research is continuing and we're very excited about our results thus far.The Defense Advanced Research Projects Agency is bidding to develop a 100 times more accurate atomic clock for a range of air, land, and sea platforms. "Our device can be integrated in a platform with smaller batteries because it uses much less power than traditional rubidium sources and it is reversible, depending on the polarity of the voltage applied, so it works as a source or a sink," Roper said. It will also keep the cold atoms cold for longer, enabling greater accuracy in atomic clocks, especially at higher operating temperatures. This will reduce measurement noise and increase accuracy when integrated into a cold-atom clock. The HRL device uses materials originally developed for batteries to remove only the warm rubidium atoms. The cooled atoms are trapped, and the more background warm atoms there are in the chamber, the weaker the signal-to-noise ratio is for the cold atoms, which reduces device accuracy. To operate at temperatures near 100 microkelvin, it is necessary to capture a subset of atoms from a warm vapor - a vapor of the alkali element rubidium in the HRL device - and cool them down. The HRL device could enable lighter weight platforms with fewer batteries or longer duration missions. Because modern communications, navigation, and electronic warfare depend on accurate timekeeping, according to DARPA the success of the CAMS program will benefit nearly every US defense system. This HRL research project, Solid Electrolyte Rubidium Vapor Orchestration (SERVO), was part of a larger Defense Advanced Research Projects Agency (DARPA) program called Enabling Component Technology for Cold-Atom Microsystems (CAMS). Our device is a big step toward solving many of those problems." The problem is that cold-atom clocks come with a whole host of added difficulties. "Scientists have managed to miniaturize room temperature atomic clocks, but cold-atom atomic clocks are much more accurate, so DARPA would like to have miniaturized versions of those too. "There are two basic types of atomic clocks, some operate at room temperature and some use atoms cooled down to just above absolute zero," said Chris Roper, HRL's project leader and senior author on the paper.
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