World's most stable atomic clock with 'zero downtime'

If you were to ask which type of clock runs most accurately, making an important contribution to the development of mankind, it must be the atomic clock.

By basic definition, an atomic clock is a type of clock that adjusts time according to the oscillation state of an atom. In which, the vibration frequency of the atom is constant and can be measured, so the atomic clock is considered the most accurate clock that man has created to date.

Due to its near-perfect performance, this unique timepiece is often used to accurately measure time, determine and coordinate time zones and time systems. In addition, atomic clocks are also used in missile systems, unmanned aircraft, and especially time measurement to determine the distance on satellites in navigation systems such as GPS, GLONASS or Galileo .

Normally, most atomic clock systems operate on the cesium (cesium) atom. However, the most modern atomic clock model manufactured by the US National Institute of Standards and Technology (NIST) operates on a lattice of ytterbium atoms (ytterbium), thereby becoming the system. The most accurate and stable working atomic clock system in the world today.

When it comes to atomic clocks, stability refers to the time consistency of each tick on the clock. Ytterbium scores up to trillions of times a second. In addition, each point must be extremely precise, because if one point is too fast while the other times are too slow, the overall accuracy of the watch will suffer. Even if the differences cancel each other out on the seconds or minute scale, the slightest deviations can make the watch less efficient on the millisecond or nanosecond scale.

Ytterbium is an extremely stable atom, so ytterbium atomic clocks are accurate beyond the nanosecond scale, all the way up to the picosecond scale (1/1000th of a second) and femtosecond (1/1,000th) scale. .000,000,000,000,000 of a second). However, scientists at NIST want to go even further.

NIST's ytterbium atomic clock.

Dead time = 0

Atomic clocks count time according to the number of oscillations of the atom. In other words, the Atomic Clock works on the basis of excitation for the electrons of an atom to jump from a low energy level to a high energy level and vice versa. The electrons of an atom emit electromagnetic waves of a very certain frequency and use the period of the oscillation of that electromagnetic wave as a standard to measure time.

For example, for a cesium atomic clock with a stable isotope 133Cs, it can be understood simply that in 1 second, an atom of Cesium-133 (133Cs) will switch between 2 energy states 9,192,631,770 times.

However, one of the problems with atomic clocks is "dead time". Typically, the atomic clocks themselves alternate between tuning periods with dead periods, where the atoms in the sample are prepared for another measurement. During dead time, small oscillations of the laser can slightly affect the measurement, making the watch less accurate.

To overcome this phenomenon, scientists at NIST have developed what they call a double clock, which coordinates two separate atomic clocks. In particular, the two clocks will alternately adjust the counting and dead time so that one of the lasers is always in the most accurate state, as well as being flexibly adjusted at any time. Thereby helping to eliminate the problem of downtime.

The NIST scientists believe their design could be used to build smaller, more portable atomic clock systems in the future. Currently, NIST's combined clock system is larger than normal clocks, but these two clocks can share many components with each other, so the overall structure is not too complicated. complex.

Such stable atomic clocks could be sent around the world to accurately map the Earth's gravitational field, or could be sent on a plane or into space to test the theory of relativity. general relativity, helping scientists study the fundamental constants of the universe and make more complex scientific discoveries.