Experimental atomic clock uses ytterbium 'pancakes'

March 6, 2006
Experimental atomic clock uses ytterbium 'pancakes'
NIST's new optical atomic clock uses two magnetic coils (red rings) and an optical lattice (red laser beam), as well as intersecting violet lasers to cool ytterbium atoms, slowing their motion. Illustration credit: NIST

Scientists at the National Institute of Standards and Technology working with Russian colleagues have significantly improved the design of optical atomic clocks that hold thousands of atoms in a lattice made of intersecting laser beams.

The design, in which ytterbium atoms oscillate or "tick" at optical frequencies, has the potential to be more stable and accurate than today's best time standards, which are based on microwaves at much lower frequencies. More accurate time standards could improve communications, enhance navigation systems, and enable new tests of physical theories, among other applications.

Experimental atomic clock uses ytterbium 'pancakes'
The lattice of laser beams traps small numbers of ytterbium atoms in pancake-shaped "wells." A yellow laser excites the atoms so that they switch between lower (blue) and higher (yellow) energy levels. Illustration credit: NIST

Described in two papers in the March 3 issue of Physical Review Letters,* the heart of the clock consists of about 1,000 pancake-shaped wells made of laser light and arranged in a single line, each containing about 10 atoms of the heavy metal ytterbium. The lattice design results in fewer systematic errors than optical atomic clocks using moving balls of cold atoms, and also offers advantages in parallel processing over other approaches using single charged atoms (ions). The optical lattice, created by an intense near-visible laser beam, is loaded by first slowing down the atoms with violet laser light and then using green laser light to further cool the atoms so that they can be captured. Scientists detect the atoms' "ticks" (518 quadrillion per second) by bathing them in yellow light at slightly different frequencies until they find the exact "resonant" frequency (or color) that the atoms absorb best.

Previous lattice-based clocks have used atoms with odd-numbered atomic masses, which have a nuclear magnetic field that causes some additional complications. The new clock uses atoms with even-numbered atomic masses that have no net nuclear magnetic field but have been difficult to use in atomic clocks until now. The researchers found they could apply a small external magnetic field combined with yellow laser light to induce an otherwise "forbidden" oscillation between two energy levels in the atoms. The team reported an extremely precise resonance frequency with a strong signal that demonstrates the clock's potential for very high stability. The new approach is also applicable to other atoms with even-numbered atomic masses, such as strontium and calcium, which are under study at NIST and other research laboratories around the world.

* Z.W. Barber, C.W. Hoyt, C.W. Oates, L. Hollberg, A.V. Taichenachev and V. I. Yudin. 2006. Direct excitation of the forbidden clock transition in neutral 174Yb atoms confined to an optical lattice. Physical Review Letters. March 3.

** A.V. Taichenachev, V.I. Yudin, C.W. Oates, C.W. Hoyt, Z.W. Barber and L. Hollberg. Magnetic field-induced spectroscopy of forbidden optical transitions with application to lattice-based optical atomic clocks. Physical Review Letters. March 3.

Source: NIST

Explore further: Scientists use lasers to simulate shock effects of meteorite impact on silica

Related Stories

Innovative imaging technique reveals new cellular secrets

September 11, 2015

Cellular mitosis depends in part on small organelles that extend spindles to pull apart chromosome pairs. Before they can perform this and other essential tasks, these tiny cylindrical structures—known as centrioles in ...

Physicists show 'molecules' made of light may be possible

September 10, 2015

It's not lightsaber time, not yet. But a team including theoretical physicists from the National Institute of Standards and Technology (NIST) has taken another step toward building objects out of photons, and the findings ...

Science provides new way to peer into pores

September 9, 2015

Rice University scientists led a project to "see" and measure the space in porous materials, even if that space is too small or fragile for traditional microscopes.

Photonics to revolutionise internet speeds

September 8, 2015

While people may have never heard of photonics before, they will surely have heard about the technology that relies on its existence, namely the internet, computers and smartphones.

Recommended for you

The dark side of Nobel prizewinning research

October 4, 2015

Think of the Nobel prizes and you think of groundbreaking research bettering mankind, but the awards have also honoured some quite unhumanitarian inventions such as chemical weapons, DDT and lobotomies.

Internet giants race to faster mobile news apps

October 4, 2015

US tech giants are turning to the news in their competition for mobile users, developing new, faster ways to deliver content, but the benefits for struggling media outlets remain unclear.

Trade in invasive plants is blossoming

October 3, 2015

Every day, hundreds of different plant species—many of them listed as invasive—are traded online worldwide on auction platforms. This exacerbates the problem of uncontrollable biological invasions.

Fusion reactors 'economically viable' say experts

October 2, 2015

Fusion reactors could become an economically viable means of generating electricity within a few decades, and policy makers should start planning to build them as a replacement for conventional nuclear power stations, according ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.