Atomic Clocks Make a Quantum Leap in Accuracy

[pilom]

In a vacuum, you could get GPS accuracy down to 700 nanometers with clocks that accurate [1]. If only that pesky atmosphere didn't get in the way!

[1]: http://www.wolframalpha.com/input/?i=%281+second+%2F430+tril...

[deletes]

There are also other problems than atmosphere.

http://eu.mio.com/en_gb/global-positioning-system_gps-accura...

[thearn4]

Hate to be that guy when it comes to being pedantic about headlines, but wouldn't a `quantum leap` in accuracy be rather un-noteworthy?

[derefr]

Or it could mean, in this case, a leap in what is considered to the smallest discernible difference (the quantum) of the measurement. ;)

[prateekj]

Quantum leap refers to a sudden increase in something. Given that this clock is 50% more precise than the previous record holder, I think it qualifies to be called a 'quantum leap'. So even if you are pedantic about headlines, it should still make sense. Don't you think so?

[Oculus]

I can here to make that exact comment. It always irks me that a lot of people don't realize 'quantum' == 'small'.

[musicaldope]

You'll never walk alone down the road of headline-aimed pedantry, friend

[ghayes]

Not to be that guy, but Merriam-Webster is pretty clear on the definition: `a sudden large change, development, or improvement`[1]

http://www.merriam-webster.com/dictionary/quantum%20leap

[dmd]

You (and everyone else who is commented in reply to you so far) didn't read the article.

In this particular case it is a perfect use of the phrase, as the advance in accuracy is based on measurements of the atomic electron transitions, also known as quantum leaps.

[ChuckMcM]

At this level of accuracy things are pretty strange. It used to bug me when you had to tune RF circuits at a distance with non-conductive tools because your body capacitance would throw the tuning off. Having a clock that just being near it will change what time it reads, well that is a whole different ballgame of weird is it not?

On a science note, why isn't this a gravity wave detector anyway?

[Daniel_Newby]

Gravity wave detectors get phase accuracy by comparing a photon to itself using an interferometer. SNR is improved by brightening the laser and averaging over more photons. The laser frequency is less important.

It turns out there are some ultraviolet nuclear transitions. The line widths promise to be obscenely narrow. If they can get it working in a clock, they will be able to directly measure gravitational time dilation of small masses.

[qianyilong]

The coolest part it that it improves both stability and accuracy. Cesium is often touted as a good clock but it only has good accuracy. The short-term stability has more noise than something like a Rubidium clock that is very stable on the short-term but inaccurate(relative to cesium anyway) on the long term.

This is cool because it is the best in both dimensions.

[madengr]

The phase noise (really short term stability) of a rubidium oscillator is rather poor compared to on ovenized quartz oscillator. So what I really want is a strontium disciplined OCXO.

[prateekj]

True! People use Rubidium clocks only because they are inexpensive. I don't think scientists working in expensive labs rely on Rubidium clocks.

[gardarh]

One thing I'm really curious about: How can you measure the accuracy of the world's most accurate clock?

By definition there would be no more accurate timing device to benchmark it against so is the accuracy cited in the article only theoretical?

[yetanotherphd]

They built two of them, and found that they agreed to within their nominal accuracy.

[Daniel_Newby]

Build several identical clocks and watch the ensemble drift relative to each other.

The lattice clock in this story has numerous clusters of atoms. They could fill only a few clusters and measure the performance relative to a good clock, then statistically derive how much it would improve by using the full set of clusters.

[DanielBMarkham]

<random internet commentator tripe>This could be the basis of a future tricorder or Star Trek-like sensor array. Three ultra-sensitive clocks in an array should be able to infer mass and motion both for the unit and objects in the local area indirectly. Relativistic effects are minuscule, but not non-existent. Extremely-tuned clocks would have some pretty cool capabilities.</random internet commentator tripe>

[splat]

One thing I've spent some time thinking about is whether it would be possible to use atomic clocks to get a better measurement of the gravitational constant G. (G is by far the most poorly known of all the fundamental physical constants.) The idea would be to build a sphere whose mass is very precisely known and place one clock near the mass and one clock far away. By measuring the gravitational time dilation you could infer G. As I recall from my order of magnitude calculations, atomic clocks would have to improve in accuracy by four orders of magnitude or so before this would be feasible. So it would still be a long ways off.

[e3pi]

Ask: Such synchronous clocks possible?

Special and general relativity steam-roll over synched digit accuracy, at introducing any object's mass, any object's displacement.

Not gain or lose over five billion years?

How many digits this time?

Tides, quakes, rain on the roof, defeat the possibility of unbounded synched accuracy.

[Daniel_Newby]

Indeed. The best existing atomic clocks need to be recalibrated if they are raised a few centimeters, owing to gravitational time dilation.

[dchichkov]

Can I have a chip-scale one? With zero jitter? On every motherboard? Feeding TSC clock? Please? Pretty pretty pleaase?

[guelo]

There are already very accurate clocks on your motherboard. Your problem has more to do with modern multi-processor design.

[prateekj]

Definitely ... just as soon as it starts raining money ;)

[danbruc]

Does it beat the pulsar clock [1]? And will standing next to clock make it go wrong because of the change of the gravitational field?

[1] http://en.wikipedia.org/wiki/Pulsar_clock

[kabdib]

Pulsars are actually pretty noisy. Starquakes, infalling matter and braking due to drag on the magnetic field jink the rotational frequency around a lot, comparable to a good clock (you could probably compensate for the braking effects, but the quakes are another matter).

[MichaelGG]

Meanwhile on servers running Windows, keeping sync to within a few seconds is a mighty challenge, esp. with Hyper-V. (Linux guests have no issue with ms or sub-ms accuracy.)

Microsoft's Win32 time is only meant to prevent Kerberos error, so under 5 minutes is "fine".

[grecy]

If you're using win32 time for anything that needs accuracy greater than a few seconds, I think you're doing it wrong.