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"China makes its first optical clock more accurate than atomic clocks
Technology - General
Thursday, 12 July 2012 19:21
Last week we spend a few minutes to talk about the Leap Second , set the time because I had a couple of days per year could be 24 hours and one second. This adjustment had its origin in the discrepancy between the time horizons we use now (atomic clocks) for the duration of days based on the rotation of the Earth (which undergoes changes and is not always exact thing). Atomic clocks from the 60, governing the official time in many countries (eg Spain set the official time atomic clock of the Royal Institute and Observatory of the Navy in San Fernando ) but for several years, scientists have managed advance much more accurate devices, optical clocks. To date there were few countries that had managed to develop this kind of watches (six) and, as announced today, China has just finished building their own (making it the seventh country to do so).
[View into the ultrahigh vacuum chamber in which strontium atoms are cooled and stored. In the upper third of the window, the blue fluorescent light of a cloud of cold strontium atoms (Sr) is to be seen.]
Since 1967, the International System of Units defines the latter as:
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A second is the duration of 9,192,631,770 oscillations of the radiation emitted in the transition between two hyperfine levels of the ground state isotope cesium-133 atom (133Cs) at a temperature of 0 degrees kelvin
This definition is based on atomic clocks, devices that mark since the official time of many countries and are used to govern synchronization systems for many network servers (NTP). Until then, time was measured by a calculation means (to eighty-six thousand cuatrocientosava part of the duration that had the mean solar day between 1750 and 1890), therefore, to mid-twentieth century was the measure of time without being somewhat accurate. Actually, although progress has been made in this direction and every time we measure time more accurately, to have atomic clocks error, very small but not negligible, and as time passes, the cumulative error requires adjustments to correct .
In 2001, an American team was the first to measure more precisely the time and developed the first optical clock of history and for that used a prototype clock based on optical frequency-cooled mercury ion. Soon after, the British National Physical Laboratory (parents of the first atomic clock) multiplied by three precision ion optical clock using strontium U.S.. Now, in the 2012, China has announced the manufacture of the first optical clock using a single calcium ion which is able to maintain such precision that would introduce an error of only 1 second every 10 million years.
The development has been undertaken of the Hubei Academy of Sciences and to build the device, used electromagnetic fields to capture a calcium ion and watch, for about fifteen days, the atomic motion of the ions. Observing, instead of measuring the activity level atomic microwave, optical clocks are responsible for measuring the activity in the optical spectrum (observing the photons), thereby reducing the error between 100 and 1,000 times.
And what a watch can serve as accurate? Given that the margin of error is 1 second every 10 million years this accuracy is useful in several areas ranging from the States (to set the official hours), the telecommunications industry (synchronization equipment) to pass even the manufacture of precision instruments.
Image: PTB"
