Dr. Jeroen Koelemeij

Assistant professor

PhD and postdoc position available in quantum-engineered measurements of trapped HD⁺ - see http://quantumions.nl

PhD position available in fiber-optic time and frequency transfer (ultrastable lasers and White Rabbit) within the QuantumDeltaNL program.

Recent news (last updated Nov 16, 2022) :

• November 2022: See our article that was published in Nature: a good ten years after we conceived the concept of 'SuperGPS', our colleagues of Delft University of Technology, VSL Delft, and us demonstrated positioning with 10 centimeter uncertainty and wireless sub-nanosecond time distribution through a mobile network infrastructure. Many thanks also to the supporters of the project: SURF, KPN, OPNT, Fugro Geoservices and many others.
  See also the News & Views piece by Hui Chen and Henk Wymeersch of Chalmers University of Technology, the SuperGPS project pages, or this YouTube video explaining the project.


• October 2022: We posted a manuscript on arXiv about (the need for) a global adjustment of fundamental physical constants and new-physics parameters. It explains how possible tiny effects of physics beyond the standard model might actually be hiding in the values of fundamental constants, and how we can distill such new-physics effects from the fundamental constants.


• October 2022: This is getting interesting... the hyperfine interval that we determined in the (v,L):(0,3)-(9,3) two-photon transition in HD⁺ was initially found to be in 4sigma disagreement with theoretical predictions, but a recent QED theory update by Haidar et al. increases the discprepancy to 9sigma. What is going on? Stay tuned - we are trying to sort out the experimental side of this huge discrepancy in our lab... Or better: come join our team as a PhD student to help sort things out!


• April 2022: Check out our paper in Molecular Physics about the effect of correlated hyperfine theory errors in the determination of rotational and vibrational transition frequencies in HD⁺. For reasons unknown to me, this paper was the Most Read article in Molecular Physicsfrom August 22 through November 15 2022 (and counting)


• June 2021: We published improved bounds on Yukawa-type nucleon-nucleon interactions obtained from a collection of precision measurements in three-body systems and precise QED theory, including our 2020 measurements carried out in HD⁺. See our publication in Physical Review Research (open access).


• September 2020: After years of arduous work, we finally completed our HD⁺ two-photon spectroscopy campaign, and combined it with the latest molecular theory from our coworkers at LKB Paris and JINR Dubna - and with what a result! A new measurement of the proton-electron mass ratio, more precise than what was obtained by the best other methods so far, and a confirmation that the proton mass and radius are indeed smaller than previously thought.
  See our paper in Science (pdf), and also the nice Perspective by Masaki Hori. More media coverage here.
  
  
• September 2020: Check out this great paper in Nature by a German collaboration about a new and very precise determination of the deuteron mass, and its consequences for what has been called the 'nuclear mass puzzle'.
  See also my News & Views commentary in Nature.
  
  
• What happened between 2017 and 2020: from 2017 to 2019 I worked full-time at OPNT BV, our university spin-off company, to help the company grow to twelve employees. Lots of fun and progress in fiber-optic time and frequency transfer, and lots of recognition for the company's work (see for example this invited presentation for the US GPS Advisory Board) - but when the opportunity arose to return to academic science and my beloved fundamental research at LaserLaB VU... I could not resist!
  
  
• March 2016: SuperGPS project started! The SuperGPS project is a collaboration of our group at VU University with colleagues at the Faculty of Civil Engineering and Geosciences and the Faculty of Electrical Engineering, Mathematics and Computer Science at Delft University of Technology. The project is funded through technology foundation STW with support from stakeholders including KPN, OPNT, VSL, TNO, and Fugro Geoservices.


• February 2016: Four new papers out!
  
  "Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD⁺,"
  J. Biesheuvel, J.-Ph. Karr, L. Hilico, K.S.E. Eikema, W. Ubachs, J.C.J. Koelemeij, Nat. Commun. 7, 10385 (2016)

  see also the press release by FOM and the Volkskrant news article

  "Theoretical hyperfine structure of the molecular hydrogen ion at the 1 ppm level,"
  V.I. Korobov, J.C.J. Koelemeij, L. Hilico, J.-Ph. Karr, Phys. Rev. Lett. 116, 053003 (2016)
  
  "Physics beyond the Standard Model from hydrogen spectroscopy,"
  W. Ubachs, J.C.J. Koelemeij, K.S.E. Eikema, E.J. Salumbides, J. Mol. Spectr. 320, 1-12 (2016)

"White Rabbit Precision Time Protocol on Long Distance Fiber Links,"
E.F. Dierikx, A.E. Wallin, T. Fordell, J. Myyry, P. Koponen, M. Merimaa, T.J. Pinkert, J.C.J. Koelemeij, H. Peek, R. Smets, IEEE Trans. Ultrason. Ferroelectr. Freq. Control., E-publication ahead of print (2016)


• February 2016: Cottonwood Euro Technoloy Fund invests 500 kE in our spin-off company OPNT BV


• November 2015: Travel grant extension awarded to the molecular hydrogen spectroscopy teams at VU Amsterdam and LKB Paris by the EP Nuffic Van Gogh Programme.


• May 2015: our team participates in ME 15 EU H2020 project 'ASTERICS'



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