This design reduces the distortions in the lattice ordinarily caused by the scattering of light and atoms, homogenizes the sample, and extends the atoms' matter waves, whose shapes indicate the probability of finding the atoms in certain locations. In this new case the lattice, which can be visualized as a stack of pancakes created by laser beams, has unusually large, flat, thin cakes, and they are formed by less intense light than normally used. The JILA researchers have now measured frequency shifts between the top and bottom of a single sample of about 100,000 ultracold strontium atoms loaded into an optical lattice, a lab setup similar to the group's earlier atomic clocks. This effect has been demonstrated repeatedly for example, NIST physicists measured it in 2010 by comparing two independent atomic clocks, one positioned 33 centimeters (about 1 foot) above the other. That is, a clock ticks more slowly at lower elevations. The frequency of the atoms' radiation is reduced - shifted toward the red end of the electromagnetic spectrum - when observed in stronger gravity, closer to Earth. NIST scientists have used atomic clocks as sensors to measure relativity more and more precisely, which may help finally explain how its effects interact with quantum mechanics, the rulebook for the subatomic world.Īccording to general relativity, atomic clocks at different elevations in a gravitational field tick at different rates. Although the theory is more than a century old, physicists remain fascinated by it. "For timekeeping, it also shows that there is no roadblock to making clocks 50 times more precise than today - which is fantastic news."Įinstein's 1915 theory of general relativity explains large-scale effects such as the gravitational effect on time and has important practical applications such as correcting GPS satellite measurements. "The most important and exciting result is that we can potentially connect quantum physics with gravity, for example, probing complex physics when particles are distributed at different locations in the curved space-time," NIST/JILA Fellow Jun Ye said. ![]() JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder. 17 issue of Nature, suggest how to make atomic clocks 50 times more precise than today's best designs and offer a route to perhaps revealing how relativity and gravity interact with quantum mechanics, a major quandary in physics. ![]() These efforts are described in our publications.The experiments, described in the Feb. To date, our work has been focused on two of the most significant experimental challenges for constructing a solid-state optical clock based on the 229Th nuclear transition: finding and constructing a suitable host crystal and determining the clock transition frequency. This paradigm shift in optical frequency standards is possible because, as indicated by recent data, the 229Th transition has the lowest energy of any known nuclear excitation, making it amenable to study by laser spectroscopy! Furthermore, because nuclear energy levels are relatively insensitive to their environment, the complicated vacuum apparatus of current optical frequency standards can be replaced by a single crystal doped with 229Th atoms. 104, 200802 (2010)) a novel optical frequency standard based on a high-Q transition in the 229Th nucleus, this “nuclear” clock architecture promises several orders of magnitude improvement in precision over next-generation optical atomic clocks, while simultaneously reducing experimental complexity. Indeed, several optical atomic clock experiments have already reported better stability than the primary Cesium standard, which keeps time for the nation. It appears universally recognized that the most promising route to improved clocks uses reference oscillators based on optical transitions. ![]() Because of these motivations, there is presently enormous, world-wide effort to build the next-generation of atomic clocks. ![]() Furthermore, high-precision clocks have also provided a means to probe fundamental issues in physics, such as the most stringent tests of General Relativity. Improved clocks, based on optical frequency standards, are likely to enable several new technologies such as secure data routing, jamming resistant communication, high-resolution coherent radar, and improved global positioning. Currently, atomic clocks are used to enable global positioning systems, cellular telephones, and the synchronization of modern-day electrical power grids. Though atomic clocks sound like the stuff of science fiction, their technological impact on everyday life is profound.
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