TU Wien

The Vienna research group is affiliated with the Vienna University of Technology and situated at a very unique location: the Atominstitut (Institute for Atomic and Subatomic Physics), which houses a TRIGA Mark II nuclear reactor. The institute features research groups from the realms of nuclear and X-ray physics, neutron physics, as well as quantum optics, making it an ideal setting for the thorium research, which is inherently located at the border line between atomic and nuclear physics. The institute also features a full-fledged radiochemistry department, where radioactive samples for the whole consortium will be processed.

The Vienna group has already a few years of experience in the growing and characterization of CaF2 crystals doped with thorium. For this purpose, an arsenal of gadgets have been assembled: a furnace for crystal growing, devices to cut and polish the crystals, a UV spectrometer for transparency measurements, as well as two chambers with VUV excitation sources (such as an Excimer laser) and detection instruments (PMTs). The crystal growing process will be continuously improved to reduce the level of radio- and photoluminescence of the crystals; the initial search for the isomer transition will then be performed at the MLS synchrotron in Berlin. Once the transition wavelength has been determined with sufficient accuracy, precision spectroscopy with lasers will be performed.

The coordination of the consortium, both on the administrative and on the science side, will be executed by the Vienna group. Currently, there are nine people working on the thorium project.


Vienna University of Technology (TU Wien)
Institute for Atomic and Subatomic Physics (Atominstitut)
Quantum metrology group

Publications of the Vienna group

Radioluminescence and photoluminescence of Th:CaF2 crystals

Simon Stellmer, Matthias Schreitl, and Thorsten Schumm
arXiv:1506.01938 and Nature Scientific Reports 5, 15580 (2015)

Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter

G. A. Kazakov, V. Schauer, J. Schwestka, S. Stellmer, J. H. Sterba, A. Fleischmann, L. Gastaldo, A. Pabinger, C. Enss, and T. Schumm
arXiv:1306.3069 and Nucl. Instr. Meth. Phys. Res. A, 735, 229 (2014)

Performance of a 229-Thorium solid-state nuclear clock

G. A. Kazakov, A. N. Litvinov, V. I. Romanenko, L. P. Yatsenko, A. V. Romanenko, M. Schreitl, G. Winkler, and T. Schumm
arXiv:1204.3268 and New J. Phys. 14, 083019 (2012)

Contact persons


Thorsten Schumm


  • since 2011: University Professor for Quantum Metrology, Atominstitut, TU Wien
  • 2006-2011: University Assistant, Atominstitut, TU Wien
  • 2006: Postdoctoral fellow, McLennan physical labs, University of Toronto
  • 2003-2006: bi-national PhD Thesis (cotutelle de thèse), Université Paris Sud & University of Heidelberg
  • 2000-2002: Diploma, University of Innsbruck & University of Heidelberg
  • 1996-2000: Studies of Physics, Free University of Berlin


  • Matter-wave interferometry in a double well on an atom chip, Nature Phys. 1, 57-62 (2005).
  • An integrated Mach-Zehnder interferometer for Bose-Einstein condensates, Nature Comm. 4, 2077 (2013).
  • Non-equilibrium coherence dynamics in one-dimensional Bose gases, Nature 499, 324-327 (2007).
  • Twin-atom beams, Nature Phys. 7, 608–611 (2011).
  • Probing quantum and thermal noise in an interacting many-body system, Nature Phys. 4, 489-495 (2008).


Simon Stellmer


  • 2002 – 2007 studies in Hamburg (Germany) and diploma thesis with Klaus Sengstock
  • 2008 – 2013 PhD and PostDoc in Innsbruck (Austria) with Florian Schreck and Rudolf Grimm
  • since 2013 VCQ fellow and project assistant at the TU Vienna (Austria)


    • Oscillations and interactions of dark and dark-bright solitons in Bose-Einstein condensates, Nature Phys. 4, 496 (2008).
    • Bose-Einstein Condensation of Strontium, Phys. Rev. Lett. 103, 200401 (2009).
    • Laser cooling to quantum degeneracy, Phys. Rev. Lett. 110, 263003 (2013).
    • Radioluminescence and photoluminescence of Th:CaF2 crystals, Nature Sci. Rep. 5, 15580 (2015).