From Atomic to Nuclear Clocks - and a Leap in Timekeeping Accuracy?

"In September 2024, U.S. scientists made key advances towards building a nuclear clock — a step beyond an atomic clock," according to ScienceAlert: In contrast to the atomic clock, the transition measured by this new device happens in the nucleus, or core, of the atom (hence the name), which gives it an even higher frequency. Thorium-229, the atom used for this study, offers a nuclear transition that can be excited by ultraviolet light. The team working on the nuclear clock overcame the technological challenge of building a frequency comb that works at the relatively high frequency range of ultraviolet light. This was a big step forward because nuclear transitions usually only become visible at much higher frequencies — like those of gamma radiation. But we are not able to accurately measure transitions in the gamma range yet.

The thorium atom transition has a frequency roughly one million times higher than the caesium atom's. This means that, although it has been measured with a lower accuracy than the current state-of-the-art strontium clock, it promises a new generation of clocks with much more precise definitions of the second. Measuring time to the nineteenth decimal place, as nuclear clocks could do, would allow scientists to study very fast processes... [G]eneral relativity is used to study high speed processes that could lead to overlaps with quantum mechanics. A nuclear clock will give us the technology necessary for proving these theories. [The clocks "will enable the study of the union of general relativity and quantum mechanics once they become sensitive to the finite wavefunction of quantum objects oscillating in curved space-time," according to the abstract of the researchers' paper.]

On a technological level, precise positioning systems such as GPS are based on complex calculations that require fine measurements of the time required by a signal to jump from one device to a satellite and onto another device. A better definition of the second will translate to much more accurate GPS. Time might be up for the caesium second, but a whole new world awaits beyond it.
As the researchers explain their paper's abstract,

Related Slashdot coverage

[davidwr]

Get Ready For Nuclear Clocks [slashdot.org] (June 29, 2024).

Re:

[olsmeister]

PBS's Nova had some decent coverage of this in Season 51 Episode 14 [rottentomatoes.com] as well.

How does this help GPS?

[Okian Warrior]

On a technological level, precise positioning systems such as GPS are based on complex calculations that require fine measurements of the time required by a signal to jump from one device to a satellite and onto another device. A better definition of the second will translate to much more accurate GPS. Time might be up for the caesium second, but a whole new world awaits beyond it.

I was under the impression that inaccuracies of GPS were caused by variations in the speed of the radio signal, variations in the speed of light in the medium of atmosphere due to variations in moisture content.

How will more resolution in the reference clock make GPS any more accurate?

Can someone familiar with GPS tech explain this?

(I am assuming that we replace the clocks in the GPS satellites with the newer technology in newer satellites.)

Re:

[Canberra1]

The tech. The move from UV to DUV to TMC micron grade etching probably defines a combs limits, and the opportunity was seen. Well a lot of expensive weapons systems use old fashioned gryros - that do wear out. Also analog Friend/Foe devices are still 'in' because digital rise cures are different. To defeat latency, extra good clocking is necessary. Pretty sure this will work and also slice the profit from RLG assemblies. If there is error, you can join several and average out errors. The application. Real h

Re:

[thegarbz]

Yes and no. Noise and drift in the clocks of the satellites themselves contributes to a couple of meters of error in the GPS signal. The ephemeris data for GPS satellites contain a correction for this, but it is only an estimate. A more accurate clock can help here.

Additionally the issues you list aren't a finite physical limitation. Galileo has worked around (or rather improved on) some of the issue which is why it has a 4x higher accuracy than GPS.

That's unfortunately the limits of my understanding on the

Re:

[gnasher719]

I think someone jumped to premature conclusions. We will have more accurate clocks, GPS needs accurate clocks, therefore we will have more accurate GPS. No, we won't.

GPS errors come from multiple sources. I think today already the clock precision is not decisive. What has bigger effects: 1. The time is sent through a 1500 MHz radio signal from which we need to extract the exact time. That's difficult. 2. The signal doesn't go through a vacuum, therefore the signal speed is variable. 3. Position and time

just wait

[usedtobestine]

It will turn out that these new clocks can be altered by quantum entanglement.

Hmmm.

[jd]

We've a wide variety of quantum gas clocks which measure time somewhere between a hundred to a thousand times better than the caesium clock.

https://en.m.wikipedia.org/wik... [wikipedia.org]
https://phys.org/news/2017-10-... [phys.org]

True, this isn't a million times more accurate, but it's still pretty good. You really do need clocks of extremely high precision to do experiments on quantum relativity or dark matter, because both of these involve incredibly small deviations.

It would presumably also improve gravitational wave detectors,

New Type of Detector....Perhaps

[Roger W Moore]

It would presumably also improve gravitational wave detectors, as they'd be able to detect absolutely trivial fluctuations.

Eventually this could result in an entirely new type of gravitational wave detector. Current detectors work by measuring tiny changes in distance by bouncing a laser back and forth along two perpendicular arms. However, if you have an accurate enough clock you could measure the change in the passage of time due to the wave. This effect is so incredibly tiny though that it is not clear that even this technology will be anywhere close to the accuracy required: the current paper is about detecting gravitation

At what altitude and latitide?

[chaoskitty]

When your measurements are that precise, the exact speed of the clock through space matters. Changing altitude will change speed, as will changing latitude.

How do they all agree how many counts per second there should be, and at what location does this number work?

Re:

[thegarbz]

The equations that govern the difference in clock ticks are well known. The clocks don't need to agree with each other, they need to agree with the equation for deriving another clock at a different altitude / speed, etc. Also measurements don't need to be this precise. A simple rubidium oscillator can already give you a demonstratable clock drift simply by getting on a plane. The original Hafele–Keating experiment from 1971 already showed this. These days clocks are precise enough that you can repeat

Lots of interesting physics potential

[joe_frisch]

A nuclear clock's timing will have a significant contribution from strong nuclear force interactions while an atomic clocks timing is almost entirely electromagnetic. A comparison would provide a very sensitive measurement of any time variations of physical constants.