Using an ultra-stable laser to manipulate strontium atoms trapped in a "lattice" made of light, scientists at JILA have demonstrated the capability to produce the most precise "ticks" ever recorded in an optical atomic clock—techniques that may be useful in time keeping, precision measurements of high frequencies, and quantum computers using neutral atoms as bits of information.
The JILA strontium lattice design, described in the December 1 issue of Science,* is a leading candidate for next-generation atomic clocks that operate at optical frequencies, which are much higher than the microwaves used in today's standard atomic clocks and thus divide time into smaller, more precise units. JILA is a joint institution of the Commerce Department's National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU-Boulder).
The JILA group, led by NIST Fellow Jun Ye, achieved the highest "resonance quality factor"—indicating strong, stable signals when a very specific frequency of laser light excites the atoms—ever recorded in coherent spectroscopy, or studies of interactions between matter and light. "We can define the center, or peak, of this resonance with a precision comparable to measuring the distance from the Earth to the Sun with an uncertainty the size of a human hair," says first author Martin Boyd, a CU-Boulder graduate student. This enabled observation of very subtle sublevels of the atoms' electronic energy states created by the magnetic "spin" of their nuclei.
The new strontium clock is among the best optical atomic clocks described to date in the published literature. It is currently less accurate overall than NIST's mercury ion (charged atom) clock (see www.nist.gov/public_affairs/releases/mercury_atomic_clock.htm). Although the strontium clock operates at a lower optical frequency, with fewer than half as many ticks per time period, the JILA clock produces much stronger signals, and its "resonant" frequency—the exact wavelength of laser light that causes the atoms to switch back and forth between energy levels—was measured with higher resolution than in the mercury clock. The result is a frequency "ruler" with finer hash marks.
Improved time and frequency standards have many applications. For instance, ultra-precise clocks can be used to improve synchronization in navigation and positioning systems, telecommunications networks, and wireless and deep-space communications. Better frequency standards can be used to improve probes of magnetic and gravitational fields for security and medical applications, and to measure whether "fundamental constants" used in scientific research might be varying over time—a question that has enormous implications for understanding the origins and ultimate fate of the universe.
One of JILA's major innovations enabling the new level of precision is a customized probe laser that is highly resistant to "noise" caused by vibration and gravity, based on a compact, inexpensive design originally developed by 2005 Nobel Laureate Jan Hall, a Fellow and senior research associate at JILA (see www.nist.gov/public_affairs/techbeat/tb2005_0726.htm#JILA).
The laser can be locked reliably on a single atomic frequency, 430 trillion cycles per second (terahertz) with a "linewidth" or uncertainty of under 2 Hertz, 100 times narrower (or more precise) than the Ye group's previously published measurements of the strontium lattice clock.
The lattice consists of a single line of 100 pancake-shaped wells — created by an intense near-infrared laser beam — each containing about 100 atoms of the heavy metal strontium. The lattice is loaded by first slowing down the atoms with blue laser light and then using red laser light to further cool the atoms so that they can be captured. Scientists detect the atoms' "ticks" (430 trillion per second) by bathing them in very stable red light at slightly different frequencies until they find the exact frequency that the atoms absorb best.
Optical lattices constrain atom motion and thereby reduce systematic errors that need to be managed in today’s standard atomic clocks, such as NIST-F1, that use moving balls of cold atoms. Lattices containing dozens of atoms also produce stronger signals than clocks relying on a single ion, such as mercury. In addition, the JILA clock ensures signal stability—a particular challenge with large numbers of atoms—by using a carefully calibrated lattice design to separate control of internal and external atom motions. Similar work is under way at a number of standards labs across the globe, including the NIST ytterbium atoms work.
The JILA work may enable quantum information to be processed and stored in the nuclear spins of neutral atoms, and enable logic operations to proceed for longer periods of time. The enhanced measurement precision also could make it easier for scientists to use optical lattices to engineer condensed matter systems for massively parallel quantum measurements.
Laura Ost | EurekAlert!
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
NASA's fermi finds possible dark matter ties in andromeda galaxy
22.02.2017 | NASA/Goddard Space Flight Center
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
22.02.2017 | Power and Electrical Engineering
22.02.2017 | Life Sciences
22.02.2017 | Physics and Astronomy