Nav: Home

NIST's quantum logic clock returns to top performance

July 15, 2019

The quantum logic clock--perhaps best known for showing you age faster if you stand on a stool--has climbed back to the leading performance echelons of the world's experimental atomic clocks.

Physicists at the National Institute of Standards and Technology (NIST) have been quietly upgrading their quantum logic clock design for the past eight years, mainly to reduce errors from unwanted motion of the single aluminum ion (electrically charged atom) that provides the clock "ticks."

As described in Physical Review Letters, the quantum logic clock's systematic uncertainty (how closely the clock represents the ion's natural vibrations, or frequency) is 9.5×10?19, the best of any clock worldwide. This means the logic clock would now neither gain nor lose one second in 33 billion years, which is about two-and-a-half times the estimated age of the universe.

In this metric, it now outpaces both NIST clocks using neutral atoms trapped in lattices of laser beams, the ytterbium lattice clock and the strontium lattice clock.

"The logic clock's performance is not surprising to me," project leader David Leibrandt said. "Ion clocks are naturally better isolated from the environment--which is the source of inaccuracy for atomic clocks--than lattice clocks are. It's important to distinguish between precision and stability on this point. People expect that lattice clocks should perform the best in stability, and they currently do. Our newest quantum logic clock is the world leader in precision but not stability."

The logic clock's stability (how long it takes to measure the time) is 1.2×10?15 for a 1-second measurement, which is near the best achieved by a single ion clock but about 10 times worse than both NIST lattice clocks.

The quantum logic clock got its nickname because it borrows logical decision-making techniques from experimental quantum computing. Aluminum is an exceptionally stable source of clock ticks, vibrating between two energy levels over a million billion times per second, but its properties are not easily manipulated or detected with lasers. So, logic operations with a partner magnesium ion are used to cool the aluminum and to signal its ticks.

Back in 2010, NIST's quantum logic clock had the best performance of any experimental atomic clock. The clock also attracted attention for 2010 demonstrations of "time dilation" aspects of Einstein's theories of relativity: that time passes faster at higher elevations but more slowly when you move faster.

Since then, NIST's lattice clocks have been continually leapfrogging each other in performance, giving the impression of a race to identify a single winner. In fact, all the clocks are useful for research purposes and are possible contenders for future time standards or other applications.

The international definition of the second (in the International System of Units, or SI) has been based on the cesium atom since 1967, so cesium remains the "ruler" for official timekeeping. The logic clock is one contender for a future time standard to be selected by the international scientific community. NIST scientists are working on several different types of experimental clocks, each based on different atoms and offering its own advantages. All these experimental clocks are based on optical frequencies, which are higher than the microwave frequencies used in today's timekeeping standards based on cesium.

Several technical advances enabled the improved performance of the logic clock, including a new ion trap design that reduced heat-induced ion motion, enabling operation near the desirable ground state, or lowest motional energy level. In addition, a lower frequency was used to operate the ion trap, reducing unwanted ion motion caused by the electric field used to trap the ions. Finally, improved quantum control has reduced the uncertainty of measurements of frequency shifts due to ion motion.

The clock's precision was determined by measuring and adding up the frequency shifts caused by nine different effects. Stability was measured by comparison to NIST's ytterbium lattice clock.

Additional improvements in trap design and other features are planned to further improve performance. Already, NIST's three experimental clocks can be compared to improve measurements of possible changes in some of the fundamental "constants" of nature, a line of inquiry that has important implications for cosmology and tests of the laws of physics such as Einstein's theories of special and general relativity.
-end-
This work was supported by the Defense Advanced Research Projects Agency and the Office of Naval Research.

Paper: S.M. Brewer, J.-S. Chen, A. M. Hankin, E.R. Clements, C.W. Chou, D.J. Wineland, D.B. Hume and D.R. Leibrandt. 2019. An 27Al+ quantum-logic clock with systematic uncertainty below 10?18. Physical Review Letters. Published 15 July 2019. DOI: 10.1103/PhysRevLett.123.033201

National Institute of Standards and Technology (NIST)

Related Aluminum Articles:

Scientists electrify aluminum to speed up important process
Scientists have found a way in the laboratory to shorten the time it takes to create a key chemical used to synthesize a variety of medications, fertilizers and other important substances.
Human exposure to aluminum linked to familial Alzheimer's disease
A new study published in the Journal of Alzheimer's Disease (JAD) supports a growing body of research that links human exposure to aluminum with Alzheimer's disease (AD).
In breakthrough method of creating solar material, NREL scientists prove the impossible really isn't
Scientists at the National Renewable Energy Laboratory (NREL) achieved a technological breakthrough for solar cells previously thought impossible.
The pectin is protectin': Study uncovers a plant barrier against toxic aluminum
Aluminum toxicity is a major contributor to poor crop growth, especially in regions with acidic soils.
Composite metal foam outperforms aluminum for use in aircraft wings
The leading edges of aircraft wings have to meet a very demanding set of characteristics.
Researchers can now place single ions into solids
New technique enables implantation of individual ions into crystals with an accuracy of 35 nanometers.
MIT engineers develop 'blackest black' material to date
MIT engineers have cooked up a material made of carbon nanotubes that is 10 times blacker than anything that has previously been reported.
A new manufacturing process for aluminum alloys
Using a novel Solid Phase Processing approach, a research team at Pacific Northwest National Laboratory eliminated several steps that are required during conventional extrusion processing of aluminum alloy powders, while also achieving a significant increase in product ductility.
Aluminum is the new steel: NUST MISIS scientists made it stronger than ever before
Aluminum is one of the most promising materials for aeronautics and automobile industry.
ALMA discovers aluminum around young star
Researchers using ALMA data discovered an aluminum-bearing molecule for the first time around a young star.
More Aluminum News and Aluminum Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.