A hybrid of atomic clocks and ultra-precise scales 18.01.2013

Physicists have created a new kind of atomic clock based on the cesium atom, which can be used not only as a chronometer and time standard, but also as ultra-precise scales, which will allow in the near future to link mass and time standards, according to an article published in the journal Science.

"The accuracy of our clocks exceeds seven parts per billion. This error corresponds to a shift of one second in eight years, which is approximately equal to the accuracy of the first cesium-based atomic clocks created 60 years ago. (On the other hand), these clocks, in combination with the best Avogadro's spheres will help us redefine the kilogram. The tick frequency in our clock is equivalent to the mass of a single atom, and knowing it, we can calculate the mass of the entire sample," said team leader Holger Mueller of the University of California at Berkeley. (USA).

As physicists explain, atoms and electrons are not only microparticles, but also waves. Because of this, they have the same properties as electromagnetic waves, including frequency and amplitude. The natural frequency of oscillations of atoms is called Compton, in honor of the American physicist Arthur Compton, one of the pioneers of quantum mechanics.

According to the authors of the article, the difficulties in measuring and observing such oscillations made their practical use as a "metronome" or clock impossible. Muller's group was able to overcome these difficulties by using the well-known "twin paradox". According to this paradox, time will flow more slowly for objects traveling at a sufficiently high speed. Thanks to this, a person who has traveled to a distant star and returned back will be younger than his twin brother on Earth.

The authors of the article adapted this phenomenon to measure the frequency of vibrations of cesium atoms. In their experimental clock there are two "twin" atoms. One of them is at rest, and the second one moves through the tank at high speed. Due to this, the number of vibrations that both atoms will make per unit time will differ markedly. Their behavior is monitored by a special device - an atomic interferometer, the readings of which are processed using a special computer algorithm. This program compares the images that appear after collisions of a laser beam and cesium atoms on the interferometer sensors and calculates the Compton frequency of one of them.

Since this frequency is constant and depends only on the mass of the particle, it can be used as the basis for ultra-precise clocks. The first prototype of atomic clocks by Muller and his colleagues is not a champion in accuracy - it is about 100 million times inferior to the best analogues based on other technologies. On the other hand, such watches can be used for completely different purposes, the most attractive and promising of which is the creation of a new mass standard. As Muller explains, by measuring the exact value of the Compton frequency, you can measure the mass of a particle, which will allow you to accurately determine the value of the kilogram and associate it with the second.