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Atomic clocks, based on minute oscillations of atoms, are the most accurate timing devices created by humans.
Every year, scientists make adjustments that improve the accuracy of these devices. Now they have reached new performance records, making two atomic clocks so accurate that they could detect gravitational waves, those weak ripples in the space-time structure.
Physicists at NIST (National Institute of Standards and Technology) obtained these results with three of the most important measurements used to evaluate atomic clock performance: systematic uncertainty, stability, and reproducibility.
"[It] can be considered the "royal flush" of the performance of these clocks, "said NIST physicist Andrew Ludlow.
The two new clocks that record records are based on ytterbium atoms. In each clock, an optical network consisting of lasers holds a thousand of these atoms motionless. These lasers excite the electrons of atoms, which then oscillate, switching with incredible regularity between two states of energy.
Like the tick of an analog clock, this energy switching can be used to keep the time – but with much greater accuracy than an analog clock or even digital clock . The last record, released last year, was so accurate that it could keep time without losing or gaining a second for 15 billion years.
And the second standard is defined by the oscillations of a cesium atom. So, you know, incredibly accurate stuff.
So, what do these new disks mean?
The systematic uncertainty is to know if the clock keeps time with the oscillations of the atoms. Both clocks were synchronized with the frequency of the ytterbium, with an error rate of 1.4 part out of 10.18.
Stability refers to the change in clock frequency over a given period. The change of ytterbium clocks was only 3.2 parts out of 1019 (or 0.00000000000000000032).
Finally, reproducibility refers to the proximity of clocks to the same frequency. Their difference was less than the level of 10-18, or one billionth of a billion. And that 's the money shot.
"The agreement of the two clocks at this unprecedented level, which we call reproducibility, is perhaps the most important result because it essentially requires and corroborates the other two results," Ludlow said.
"This is all the more true as demonstrated reproducibility shows that the total error of clocks is less than our general ability to account for the effect of gravity on time here on Earth.
"Therefore, if we envisage clocks like these being used around the world or around the world, their relative performance would be, for the first time, limited by the effects of Earth's gravitation."
This stunning precision will surely benefit many instruments and experiments using atomic clocks.
For example, global positioning systems, which receive signals from satellites equipped with atomic clocks, then measure the signal delay of each satellite and convert them into spatial coordinates.
Atomic clocks have also been used to detect and measure the dilation of time, the effect of speed or gravity on time. Relative speed slows down time. Greater gravity also slows down time; For example, at higher altitudes on Earth, time actually goes a little faster.
Because of this difference, atomic clocks can be placed at different altitudes to measure gravity itself. This means that these new clocks could – in theory – be used to measure the shape of the gravitational field of the Earth, a field known as relativistic geodesy, with an accuracy of one centimeter.
But atomic clocks that are also accurate and sensitive to gravity could also potentially detect the extremely weak signals emitted by gravitational waves.
And there is the incredibly tempting prospect of dark matter, which we have never detected directly yet. Theoretically, when atomic clocks interact with dark matter, they can accelerate or slow down, but in absolutely minute fractions of a second. Synchronized atomic clocks can make these discrepancies detectable in a way that other clocks can not.
These applications have not yet been applied with these new disk breakers – with the amount of laser power required, they are somehow related to the lab. But it's definitely an exciting leap forward.
The team's research was published in the journal Nature.
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