Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New "pendulum" for the ytterbium clock

09.03.2012
A transition which can only be excited with difficulty in the ytterbium ion allows an extremely high accuracy

The faster a clock ticks, the more precise it can be. Due to the fact that lightwaves vibrate faster than microwaves, optical clocks can be more precise than the caesium atomic clocks which presently determine time.


The ion trap of the ytterbium clock at PTB.
(picture: PTB)

The Physikalisch-Technische Bundesanstalt (PTB) is even working on several of such optical clocks simultaneously. The model with one single ytterbium ion caught in an ion trap is now experiencing another increase in accuracy. At PTB, scientists have succeeded in exciting a quantum-mechanically strongly "forbidden" transition of this ion and - in particular - in measuring it with extreme accuracy. The optical clock based on it is exact to 17 digits after the decimal point. The results are published in the current edition of the scientific journal "Physical Review Letters".

Optical transitions are the modern counterpart of the pendulum of a mechanical clock. In atomic clocks, the "pendulum" is the radiation which excites the transition between two atomic states of different energy. In the case of caesium atomic clocks, it lies in the microwave range, in the case of optical clocks in the range of laser light so that their "pendulum" oscillates with higher velocity and optical clocks are - consequently - regarded as the atomic clocks of the future.

In the experiment performed at PTB, the scientists devoted themselves to a special forbidden transition. In quantum mechanics, "forbidden" means that the jump between the two energy states of the atoms is almost impossible due to the conservation of symmetry and angular momentum. The excited state can then be very persistent: In the case investigated here, the lifetime of the so-called F-state in the ytterbium ion Yb+ amounts to approx. 6 years. Due to this long lifetime, an extremely narrow resonance - whose linewidth only depends on the quality of the laser used - can be observed during the laser excitation of this state. A narrow resonance line is an important prerequisite for an exact optical clock. At the British National Physical Laboratory (NPL), the sister institute of PTB, the laser excitation of this Yb+-F state from the ground state was achieved for the first time in 1997. As the transition is, however, strongly forbidden, a relatively high laser intensity is required for its excitation. This disturbs the electron structure of the ion as a whole and leads to a shift of the resonance frequency so that an atomic clock based on it would exhibit a rate depending on the laser intensity.

At PTB it has now been possible to show that alternating excitation of the ion with two different laser intensities allows the unperturbed resonance frequency to be determined with high accuracy. Due to this, it has become possible to investigate other frequency shifts often occurring in atomic clocks - e.g. by electric fields or the thermal radiation of the environment. It has turned out that these are unexpectedly small in the case of the Yb+-F state, which can be attributed to the special electronic structure of the state. This is a decisive advantage for the further development of this atomic clock. In the experiments at PTB, the relative uncertainty of the Yb+ frequency was determined with 7 · 10-17. This corresponds to an uncertainty of the atomic clock of only approx. 30 seconds over the age of the universe.

Both groups at NPL and PTB have measured the frequency of the Yb+ transition with their caesium clocks and the results agree within the scope of the uncertainties (1 · 10-15 and 8 · 10-16) which are mainly determined by the caesium clocks. In a research project recently approved within the scope of the European Metrology Research Programme, the two institutes will in future cooperate with other European partners even more intensively in the development of this optical clock. In the case of the Yb+ ion, it is of particular interest that it has two transitions which are suitable for optical clocks: Less strongly forbidden, but also very precise, the excitation of the D-level can be used at a wavelength of 436 nm. This opens up the possibility of investigating the accuracy of the optical clock by frequency comparisons of the two transitions in one ion, without having to refer to a caesium clock.

Scientific publications
PTB experiment:
N. Huntemann et al.: High-accuracy optical clock based on the octupole transition in 171Yb+.
Phys. Rev. Lett. 108,090801 (2012)

NPL experiment:
S. A. King et al.: Absolute frequency measurement of the 2S1/2 - 2F7/2 electric octupole transition in a single ion of 171Yb+ with 10-15 fractional uncertainty. New J. Phys. 14, 013045 (2012)
Contact
Dr. Ekkehard Peik, PTB Department 4.4 Time and Frequency, phone: +49 (0)531) 592-4400, e-mail: ekkehard.peik@ptb.de

Dr. Ekkehard Peik | EurekAlert!
Further information:
http://www.ptb.de

Further reports about: 171Yb+ PTB Yb+ Yb+-F optical clock optical clocks pendulum ytterbium clock

More articles from Physics and Astronomy:

nachricht From China to the South Pole: Joining forces to solve the neutrino mass puzzle
25.02.2020 | Johannes Gutenberg-Universität Mainz

nachricht Beyond the brim, Sombrero Galaxy's halo suggests turbulent past
21.02.2020 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: High-pressure scientists in Bayreuth discover promising material for information technology

Researchers at the University of Bayreuth have discovered an unusual material: When cooled down to two degrees Celsius, its crystal structure and electronic properties change abruptly and significantly. In this new state, the distances between iron atoms can be tailored with the help of light beams. This opens up intriguing possibilities for application in the field of information technology. The scientists have presented their discovery in the journal "Angewandte Chemie - International Edition". The new findings are the result of close cooperation with partnering facilities in Augsburg, Dresden, Hamburg, and Moscow.

The material is an unusual form of iron oxide with the formula Fe₅O₆. The researchers produced it at a pressure of 15 gigapascals in a high-pressure laboratory...

Im Focus: From China to the South Pole: Joining forces to solve the neutrino mass puzzle

Study by Mainz physicists indicates that the next generation of neutrino experiments may well find the answer to one of the most pressing issues in neutrino physics

Among the most exciting challenges in modern physics is the identification of the neutrino mass ordering. Physicists from the Cluster of Excellence PRISMA+ at...

Im Focus: Therapies without drugs

Fraunhofer researchers are investigating the potential of microimplants to stimulate nerve cells and treat chronic conditions like asthma, diabetes, or Parkinson’s disease. Find out what makes this form of treatment so appealing and which challenges the researchers still have to master.

A study by the Robert Koch Institute has found that one in four women will suffer from weak bladders at some point in their lives. Treatments of this condition...

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

Turbomachine expander offers efficient, safe strategy for heating, cooling

25.02.2020 | Power and Electrical Engineering

The seismicity of Mars

25.02.2020 | Earth Sciences

Cancer cachexia: Extracellular ligand helps to prevent muscle loss

25.02.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>