New method for the coherent suppression of tensor frequency shifts

The PTB team has developed and implemented a scheme to coherently suppress tensor frequency shifts that may arise from the interaction between ions in Coulomb crystals. The magnitude of these shifts depends on the orientation of the ion's quantization axis  relative to the external perturbation. The method applies the continuous rotation of an external magnetic field during the free atomic state evolution in a Ramsey excitation. It retrieves the unperturbed frequency within a single interrogation cycle and is readily applicable to various atomic clock systems. 

The work is published in Physical Review Letters.

Measurement of the Th-229 Isomer Energy with a Magnetic Microcalorimeter

TU Wien together with partners from Heidelberg University, Mainz University and Helmholtz Institute Mainz present a precision measurement of the energy of the low-lying isomeric state in Th-229 based on the spectrum of gamma radiation produced in the alpha decay of U-233 using a dedicated cryogenic magnetic microcalorimeter. The evaluation determines the Th-229 isomer energy to be 8.10(17) eV, superseding in precision previous values based on gamma spectroscopy, and agreeing with a recent measurement based on internal conversion electrons. 

The work is published in Physical Review Letters.

Electronic Bridge Excitation in Highly Charged Th-229 Ions

The MPIK team together with cooperation partners from Columbia University, USA, the Univ. of New South Wales, Australia, and LMU Munich, Germany, has published a proposal and theoretical investigation of the excitation of the 8-eV Th-229 isomer through the electronic bridge mechanism in highly charged ions. By exploiting the rich level scheme of open 4f orbitals and the robustness of highly charged ions against photoionization, a pulsed high-intensity optical laser can be used to efficiently drive the nuclear transition by coupling it to the electronic shell.

The work is published in Physical Review Letters. 

Online Workshop on next-generation quantum clocks

5 - 8 October 2020

New perspectives are now on the horizon to realize the next generation of quantum clocks: collective behavior of atoms and ions, spin squeezing, entanglement, superradiance, nuclear transitions, application of quantum logic and other tricks can be exploited to further improve quantum clocks both in term of stability and accuracy. The EU funded projects Quantera Q-Clocks, USOCS and CC4C are organizing an online workshop hosted by ICFO.
With 8 tutorial lectures given by world leading scientists, the workshop will be a great opportunity to learn about these new techniques and their application in the field of time and frequency metrology.
Students already involved in this field of research are warmly invited to present a poster about their most recent results.  

Register at:

Workshop program


New Publications:

Three papers from the project consortium have been published in the AIP journal Review of Scientific Instruments:
The INRIM team is reporting its radiofrequency drive based on interdependent resonant circuits for precise control of ion traps, and a scalable hardware and software control apparatus for experiments with hybrid quantum systems,

The MPIK/LUH/PTB coooperation has published on its cryogenic radio-frequency ion trap for quantum logic spectroscopy of highly charged ions,

The MPIK group has also made available three master's theses defended at the Ruprecht-Karls-Universität in Heidelberg on the development of cryogenic RF traps and laser spectroscopy of highly charged ions (see publications)

International summer schools on metrology:

Optical clocks with trapped ions will be a topic at several summer schools, with lectures given by CC4C
coordinator E. Peik:

European Frequency and Time Seminar EFTS 2019
1-5 July 2019, Besancon, France

International School of Physics "Enrico Fermi"
4-13 July 2019, Varenna, Italy

Les Houches predoc school on Interaction of Light and Cold Atoms
30 September - 11 October 2019, Les Houches, France


Project Meeting in Vienna

The project meeting in Vienna will take place after 9 months project duration. The consortium will meet at BEV-PTP and TU Wien ATI from 2019, February 13 - 14.


Kick-Off meeting of the CC4C Consortium from 20 to 21 June

Project start

Official Start of CC4C on May 1, 2018