Here comes the world’s most accurate quantum clock

March 10th, 2008 - 2:04 pm ICT by admin  

New York, March 10 (IANS) An atomic clock, based on a single aluminium atom and applying computer logic to the peculiarities of the quantum world, now rivals the world’s most accurate clock, relying on a mercury atom. Both clocks are at least 10 times more accurate than the current US time standard, according to a new study, Sciencedaily reported.

The measurements were made in a yearlong comparison of the two next-generation clocks, both designed and built at the US Commerce Department’s National Institute of Standards and Technology (NIST).

The clocks were compared with record precision, allowing scientists to measure the relative frequencies of the two clocks to 17 digits - the most accurate measurement of this type ever made.

The comparison produced the most precise results yet in the worldwide quest to determine whether some of the fundamental constants that describe the universe are changing slightly over time, a hot research question that may alter basic models of the cosmos.

The aluminium and mercury clocks are both based on natural vibrations in ions (electrically charged atoms) and would neither gain nor lose one second in over a billion years, if they could run for such a long time, compared to about 80 million years for NIST-F1, the US time standard based on neutral caesium atoms.

The mercury clock was first demonstrated in 2000 and is now four times better than its last published evaluation in 2006, thanks to ongoing improvements in the clock design and operation.

The mercury clock continues its reign as the world’s most accurate for now, by a margin of 20 percent over the aluminium clock, but the designers say both experimental clocks could be improved further.

“The aluminium clock is very accurate because it is insensitive to background magnetic and electric fields, and also to temperature,” said Till Rosenband, the NIST physicist who built the clock and is co-author of the new study.

“It has the lowest known sensitivity of any atomic clock to temperature, which is one of the most difficult uncertainties to calibrate,” he added.

Highly accurate clocks are used to synchronise telecom networks and deep-space communications, and for satellite navigation and positioning.

Next-generation clocks may also lead to new types of gravity sensors, which have potential applications in exploration for underground natural resources and fundamental studies of the Earth.

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