Tiny optical frequency clock measures time accurately to 270 quintillionths of a second

May 9, 2016 by Matthew Chin, University of California, Los Angeles
The optical clock developed by UCLA Engineering researchers is the small black strip between the two black cylinders.

Researchers at the UCLA Henry Samueli School of Engineering and Applied Science have created an optical clock that's just 1 cubic centimeter—small enough to fit on a standard silicon chip—and can track time intervals with precision to 270 quintillionths of second. (One quintillionth is equivalent to 1 times 10 to the negative 18th power, or 0.000000000000000001.)

Today's most accurate clocks, atomic clocks, are used to keep time for the Internet and satellite communications, and help astronomers detect Earth-like planets beyond our solar system. Their accuracy—to "only" within a tenth of trillionths of a second, or 1 times 10 to the negative 13th power—is based on the naturally occurring frequencies of atoms that respond to radiation. The atomic frequencies can be expressed as a "frequency comb," a series of evenly spaced vertical lines of light produced by the atoms under radiation into microwave frequencies that are accessible to the electronic instruments that ultimately turn those readings into accurate measurements of time.

Previous optical clocks were much larger than the new one developed at UCLA: They used large fiber lasers that needed to be housed in equipment about the size of a desktop computer. The UCLA team was able to shrink the mechanism significantly to 1 cubic centimeter by using a process similar to how silicon chips are made. The new clock's precision approaches the world's best frequency standards.

The clock could lead to more precise measurements of space and time, an area known as attosecond physics, and could have applications in optical, wireless and space-based communications. For example, it could be used to measure the movement of atoms, or to discern the movement of distant objects far beyond our solar system.

"If incorporated with other technologies into infrared telescope observatories, this device can enable the detection of Earth-like planets and celestial objects 100 times smaller than that, which was previously impossible," said Shu-Wei Huang, a UCLA Engineering scientist and the project's lead author. The research was published in Science Advances. Chee Wei Wong, a UCLA associate professor of electrical engineering, is the project's principal investigator.

"Measuring the time it takes for a pulse of light to reflect from an object and return back to us also tells us a distance," Wong said. "This could help in precision laser distance ranging, such as in sensing for self-driven automobiles and aerial vehicles."

Wong said the laser clock could help generate ever-shorter pulses of light, which would be useful for watching the motion of electrons or detecting trace hazardous materials from faraway distances.

The new clock could also help further refine the absolute value of "fundamental constants," numbers that are thought to be same throughout the universe—for example, the strength of electromagnetic interactions between electrons and other elementary particles.

Wong said because the clock is cast on a silicon chip, it is more reliable than the previous, larger model, which required additional stabilization and control electronics to work.

The paper's other authors are Jinghui Yang of UCLA, Mingbin Yu and Dim-Lee Kwong of Singapore's Institute for Microelectronics , and Bart McGuyer and Tanya Zelevinsky of Columbia University.

Explore further: A new EU project on ultra-precise atomic clocks

More information: S.-W. Huang et al. A broadband chip-scale optical frequency synthesizer at 2.7 x 10-16 relative uncertainty, Science Advances (2016). DOI: 10.1126/sciadv.1501489

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6 comments

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antialias_physorg
4.5 / 5 (8) May 09, 2016
The clock could lead to more precise measurements of space and time, an area known as attosecond physics, and could have applications in optical, wireless and space-based communications.

...and GPS.

From what I could find GPS is accurate to within 3 meters because of time uncertainty at the receiver end to within 10 nanoseconds.
The clock in the article is 10 orders of magnitude better (though the linked article only talks about 8 orders of magnitude improvement(?)).
I'm sure that other error sources would mean that the improvement doesn't scale to the full extent, but even an improvement of 2-3 orders of magnitude in GPS positioning accuracy would be very useful.

(...unless this requires some special environmental control like cryogenics or somesuch)

Anyone know at what range the clock uncertainty no longer features as the dominant source of errors in GPS? I couldn't find a comparison of error sources by magnitude.
Drumbum
4.3 / 5 (6) May 09, 2016
The military GPS system is far more accurate than that. The civilian system is limited for safety reasons, not technological limits.
Pooua
5 / 5 (6) May 09, 2016
The military GPS system is far more accurate than that. The civilian system is limited for safety reasons, not technological limits.


Actually, some civilian GPS is accurate to centimeters, but those units used to cost $3k. The prices have dropped significantly in the last year or two. These more accurate GPS units are used in GIS applications.

Incidentally, the military stopped degrading the civilian GPS signals in the '90s.
indio007
1 / 5 (1) May 10, 2016
What about outside interference? What's the accuracy then? The real world is not laboratory. There is spectrum coming in at every frequency everywhere all the time.Emission of noise at the same frequency will......? We know the answer.
Uncle Ira
4 / 5 (4) May 10, 2016
The military GPS system is far more accurate than that. The civilian system is limited for safety reasons, not technological limits.


This is basically true when you are talking about the moving portable GPS units, like handhelds and mobile.

Stationary GPS locating and mapping (such like that is done for undersea surveys and remote mapping, and even construction) can get down into the cm or even mm accuracy. It all depends on the "time over target" and being linked to another unit(s) that is stationed on a benchmark.

The only thing keeping the typical civilian devices from performing as well the military systems, is the number of satellites available to them, and the exorbitant expense of making the device for cm accuracy and another one where 3 meters is good enough.

Non, I am not the science genius like a lot of other peoples here are not either. My bother is the surveyor business and tells me this when we were talking about navigation on the river.
TechnoCreed
5 / 5 (3) May 11, 2016
The military GPS system is far more accurate than that. The civilian system is limited for safety reasons, not technological limits.

There is no more dithering (What is known as Selective Availability 'SA') on the GPS since May 1st 2000. Go to the following link and read "What is SA?", "Why was SA necessary?", "What is the status on SA?. And "Will SA ever be turned back on?" http://www.faa.go...gps/#ad1 Here is a short article on the historic of it http://www.navigo...GPS.html

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