Physics
Swiss scientists prove durability of quantum network — Scientists and engineers have proven the worth of quantum cryptography in telecommunication networks by demonstrating its long-term effectiveness in a real-time network…
Pitt discoveries in quantum physics could change face of technology — Researchers at the University of Pittsburgh have made advances in better understanding correlated quantum matter that could change technology as we know it, according to a study published…
Mechanism of wine swirling explained — Wine drinkers know that swirling a good vintage around in a glass aerates the wine and releases its bouquet. Just how the process - known as 'orbital shaking' - works, however, has…
Calculations with 14 quantum bits — The term entanglement was introduced by the Austrian Nobel laureate Erwin Schroedinger in 1935, and it describes a quantum mechanical phenomenon that while it can clearly be demonstrated…
SU physicists first to observe rare particles produced at the Large Hadron Collider at CERN — Shortly after experiments on the Large Hadron Collider (LHC) at the CERN laboratory near Geneva, Switzerland began yielding scientific data last fall, a group of scientists led by a…
Enhancing the magnetism — 'The nation that controls magnetism will control the universe,' famed fictional detective Dick Tracy predicted back in 1935. Probably an overstatement, but there's little doubt the…
An icy gaze into the Big Bang — Scientists of the Institute for Quantum Optics and Quantum Information (IQOQI) in Innsbruck, Austria, have reached a milestone in the exploration of quantum gas mixtures. In an international…
Is space like a chessboard? — Physicists at UCLA set out to design a better transistor and ended up discovering a new way to think about the structure of space…
Physicists move closer to efficient single-photon sources — A team of physicists in the United Kingdom has taken a giant step toward realising efficient single-photon sources, which are expected to enable much-coveted completely secure optical…
A small quantum leap — Northwestern University researchers have developed a new switching device that takes quantum communication to a new level. The device is a practical step toward creating a network that…
Where am I? > Home > News > Physics

Optical atomic clock becomes portable

Science Centric | 3 September 2009 18:00 GMT
Printable version A clip for your blog or website E-mail the story to a friend
Bookmark or share the story on your social network Vote for this article Decrease text size Increase text size
DON'T MISS —
Physicists set new record for quantum memory storage
Physicists set new record for quantum memory storage — Physicists have taken a significant step toward creation of quantum networks by establishing a new record for the length…
Avalanches - triggered from the valley
Avalanches - triggered from the valley — Everybody knows that skiers swishing down steep slopes can cause extensive slab avalanches. But there is a less well known…
More Physics

You imagine a clock to be different - yet the optical table with its many complicated set-ups really is one. Optical clocks like the strontium clock in the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig could be the atomic clocks of the future; some of them though are already ten times more precise and stable than the best primary caesium atomic clocks. Now they might also become more compact and even portable, maybe in the future even travel to space. PTB scientists have shown how some fundamental difficulties, which a more simple set-up had previously hindered, could be avoided. They have written about this in the current edition of the journal 'Physical Review Letters.' In the next step they want to build such a clock. They already have a practical application in mind: the clock could help to determine geographical heights even more exactly than before.

An optical clock is so exact because its 'pendulum' swings so quickly. The same effect that makes a quartz clock more precise than a classical grandfather clock is behind this: the periodically swinging element within, the oscillating quartz crystal, moves by far more quickly than the pendulum of the grandfather clock; thus the scale can to some extent be divided more precisely and also be more precisely checked. The 'pendulum' of a caesium atomic clock swings even more quickly: i.e. that microwave radiation which can bring about a spin change in each electron of a caesium atom. Precisely the microwave frequency at which this effect is largest defines the second. An optical atomic clock works with the still higher frequency of optical radiation - that is with an even faster pendulum.

As the movement of the atoms leads to very large frequency shifts through the Doppler effect, in the best of these clocks the atoms are slowed down to a hundredth of the speed of a pedestrian in a first preparation step with the aid of laser cooling. In a lattice clock a further step then follows in which the atoms are held in potential wells. These are created through the intensive light field of a laser. Several tens of thousands of strontium atoms are trapped in this so-called optical lattice. The movement of the atoms is thus limited to the fraction of an optical wavelength, so that shifts through the Doppler effect can be ignored.

A few hundred atoms which can disturb each other are trapped in each potential well. If the isotope strontium-87, a fermion, is used, two of these particles do not come close to each other at very low temperatures due to the Pauli principle. That is the reason why this isotope is used to construct optical clocks. But as it can only be cooled relatively complicatedly with laser light and, moreover, only has a natural abundance of 7 %, it is, in principle, not so well suited for simple, transportable clocks or even for clocks suitable for space.

The isotope strontium-88 with over 80 % natural abundance, which is also easier to cool, is, however, a boson. That means that even at the lowest temperatures many collisions between the atoms occur. They can lead to losses and to a shift and broadening of the reference line. How strongly these collisions influence the accuracy of the clock was, however, not known previously. In an experiment at PTB, these influences have now been measured in detail for the first time. The results of the investigation have shown how the optical lattice has to be dimensioned and how many atoms may be stored in it to operate a very accurate lattice clock also with strontium-88. A clock is now being built on this basis which is more compact and more transportable than the previous lattice clocks.

The gravitational red shift of the earth, amounting to a height difference of 10 - 16 per meter on its surface, is being discussed as a possible first use for the precise determination of the height over the geoid. So the clock could be used to improve, for example, gravitation maps.

Source: Physikalisch-Technische Bundesanstalt (PTB)


Leave a comment
The details you provide on this page [e-mail address] will not be used to send unsolicited e-mail, and will not be supplied to a third party! Please note that we can not promise to give everyone a response. Comments are fully moderated. Once approved they will be posted within 24 hours.
Expand the form to leave a comment

RSS FEEDS, NEWSLETTER
Find the topic you want. Science Centric offers several RSS feeds for the News section.

Or subscribe for our Newsletter, a free e-mail publication. It is published practically every day.

Deterministic entanglement swappingDeterministic entanglement swapping

— Scientists led by Rainer Blatt, Markus Hennrich and Mark Riebe of the Institute for Experimental Physics at Innsbruck University recently succeeded for the first…

Scientists tweak quantum force, reducing barrier to tiny devicesScientists tweak quantum force, reducing barrier to tiny devices

— Cymbals don't clash of their own accord - in our world, anyway. But the quantum world is bizarrely different. Two metal plates, placed almost infinitesimally close…

Scientist examines the physics of carbon nanotubesScientist examines the physics of carbon nanotubes

— Carbon nanotubes, described as the reigning celebrity of the advanced materials world, are all the rage. Recently researchers at Rice University and Rensselaer Polytechnic…

Penning trap mass spectrometry technique uncovers new iron isomerPenning trap mass spectrometry technique uncovers new iron isomer

— A ground state atomic nucleus can be something of a black box, masking subtle details about its structure behind the aggregate interplay of its protons and neutrons.…

Popular tags in Physics: electron · optical · photon · quantum