Optical Clocks in Networks

Establish fiber-based optical clock networks, improve optical clocks and frequency transfer techniques, exploit chronometric levelling for geodesy.

Contributions to QuantumFrontiers

  • The optical fibre link between PTB and LUH is the backbone infrastructure for enabling new and accurate measurement capabilities for researchers in geodesy, atomic physics and quantum communication
  • Coordination of measurement campaigns between clocks for the investigation of e.g., frequency ratios in highly charged ions, dark matter, chronometric levelling in geodesy and quantum communication protocols
  • Advancement and development of the clock and related technologies to be broadly applicable
  • Development and validation of the measurement equipment that is used to test our physical understanding by precision spectroscopy

Collaborative Innovation

  • Developing  hardware that is common in all clocks, e.g. FPGA-based locks, autonomous laser operation (Ch. Lisdat (PTB), P.O. Schmidt (PTB/LUH), T. Mehlstäubler (PTB/LUH), J. Keller (PTB), E. Brenkler (PTB), U. Sterr (PTB), G. Grosche (PTB), A. Kuhl (PTB))
  • Advancing data analysis strategies e.g., the development of data structures that are interchangeable with international partners and the interpretation of data to validate individual clocks (J. Kronjäger (PTB), E. Benkler (PTB), S. Koke (PTB), J. Keller (PTB))
  • Developing strategies to best exploit the available and future fiber links and clock infrastructure for e.g. chronometric levelling (J. Kronjäger (PTB), Ch. Lisdat (PTB), T. Liebisch (PTB), T. Mehlstäubler (PTB), S. Koke (PTB), G. Grosche (PTB), A. Kuhl (PTB), J. Müller (LUH), S. Schön (LUH))
  • Achieving an inaccuracy and an instability of stationary optical clocks to be reliably below the level of 1 part in 1018 (Ch. Lisdat (PTB), P.O. Schmidt (PTB/LUH), T. Mehlstäubler (PTB/LUH), J. Keller (PTB), D. Nicolodi (PTB), C. Vishwakarma (PTB), S. Sauer (TUBS))
  • Advancing today’s optical clocks from prototype status to more reliable, rugged, transportable and miniaturized devices (Ch. Lisdat (PTB), P.O. Schmidt (PTB/LUH), T. Mehlstäubler (PTB/LUH), J. Keller (PTB), C. Vishwakarma (PTB), U. Sterr (PTB))
  • Confirming inaccuracy and instability of interferometric fibre links in the 10-19 to 10-20 regime (J. Kronjäger (PTB), S. Koke (PTB), J. Ji (PTB), E. Benkler (PTB), G. Grosche (PTB), A. Kuhl (PTB))
  • Investigating the coherent, low-noise frequency conversion in optical frequency combs (E. Benkler (PTB), U. Sterr (PTB))
  • Investigating link non-reciprocality and relativistic effects (E. Hackmann (ZARM), C. Lämmerzahl (ZARM), D. Philipp (ZARM), J. Kronjäger (PTB), G. Grosche (PTB))
  • Investigating coherent free-space frequency transfer (S. Koke (PTB), J. Ji (PTB), J. Kronjäger (PTB))
  • Develop methods and instrumentation for simultaneous quantum communication and time & frequency dissemination via optical fibres (J. Kronjäger (PTB), G. Grosche (PTB), A. Kuhl (PTB), S. Kück (PTB), F. Ding LUH))

Scientific Output

  • Publications
    Bondza SA, Leopold T, Schwarz R, Lisdat C. Achromatic, planar Fresnel-reflector for a single-beam magneto-optical trap. Review of scientific instruments. 2024 Jan 25;95(1):013202. doi: 10.1063/5.0174674
    Grotti J, Nosske I, Koller SB, Herbers S, Denker H, Timmen L et al. Long-distance chronometric leveling with a portable optical clock. Physical review applied. 2024 Jun 3;21(6):L061001. doi: 10.1103/PhysRevApplied.21.L061001
    Dörscher S, Klose J, Maratha palli S, Lisdat C. Experimental determination of the E2−M1 polarizability of the strontium clock transition. Physical Review Research. 2023 Feb 7;5(1):L012013. doi: 10.1103/PhysRevResearch.5.L012013
    Filzinger M, Dörscher S, Lange R, Klose J, Steinel M, Benkler E et al. Improved limits on the coupling of ultralight bosonic dark matter to photons from optical atomic clock comparisons. Physical Review Letters. 2023 Jun 22;130(25):253001. 253001. doi: 10.48550/arXiv.2301.03433, 10.1103/PhysRevLett.130.253001
    Bondza S, Lisdat C, Kroker S, Leopold T. Two-Color Grating Magneto-Optical Trap for Narrow-Line Laser Cooling. Physical review applied. 2022 Apr 1;17(4):044002. doi: 10.1103/physrevapplied.17.044002
    Herbers S, Häfner S, Dörscher S, Lücke T, Sterr U, Lisdat C. Transportable clock laser system with an instability of 1.6 × 10-16. Optics letters. 2022 Oct 15;47(20):5441-5444. doi: 10.1364/OL.470984
    Schioppo M, Kronjäger J, Silva A, Ilieva R, Paterson JW, Baynham CFA et al. Comparing ultrastable lasers at 7 × 10−17 fractional frequency instability through a 2220 km optical fibre network. Nature Communications. 2022 Jan 11;13(1):212. doi: 10.1038/s41467-021-27884-3
    Dörscher S, Huntemann N, Schwarz R, Lange R, Benkler E, Lipphardt B et al. Optical frequency ratio of a 171Yb+ single-ion clock and a 87Sr lattice clock. METROLOGIA. 2021 Feb;58(1):015005. doi: 10.1088/1681-7575/abc86f
    Pelzer L, Dietze K, Kramer J, Dawel F, Krinner L, Spethmann N et al. Tailored optical clock transition in 40Ca+. Measurement: Sensors. 2021 Dec;18:100326. Epub 2021 Sept 30. doi: 10.1016/j.measen.2021.100326
    Micke P, Leopold T, King SA, Benkler E, Spieß LJ, Schmöger L et al. Coherent laser spectroscopy of highly charged ions using quantum logic. NATURE. 2020 Feb 6;578:60-65. Epub 2020 Jan 29. doi: 10.48550/arXiv.2010.15984, 10.1038/s41586-020-1959-8
    Porsev SG, Safronova UI, Safronova MS, Schmidt PO, Bondarev AI, Kozlov MG et al. Optical clocks based on the Cf15+ and Cf17+ ions. Physical Review A. 2020 Jul 6;102(1):012802. doi: 10.48550/arXiv.2004.05978, 10.1103/PhysRevA.102.012802
    Schulte M, Lisdat C, Schmidt PO, Sterr U, Hammerer K. Prospects and challenges for squeezing-enhanced optical atomic clocks. Nature Communications. 2020 Nov 24;11(1):5955. doi: 10.1038/s41467-020-19403-7
    Wu H, Müller J, Lämmerzahl C. Clock networks for height system unification: A simulation study. Geophysical journal international. 2018 Nov 28;216(3):1594-1607. doi: 10.1093/gji/ggy508

TG Members

  • Involved Members and their Relevant Expertise
    Members Institution Relevant Expertise
    Christian Lisdat, LeaderPTBSr Optical Lattice Clock
    Gesine GroschePTBFree-Space Frequency Transfer; Frequency Transfer Techniques
    Alexander KuhlPTBFree-Space Frequency Transfer
    Chetan VishwakarmaPTBSr Optical Lattice Clock
    Jürgen MüllerLUHRelativistic Geodesy; LLR Relativity Test; Application of Quantum Gravimetry
    Piet O. SchmidtPTB / LUHQuantum Logic Spectroscopy of Highly Charged Ions; Stationary and transportable Al+ Clocks
    Claus LämmerzahlZARMQuantum Sensors in Free Fall; Relativistic Geodesy; Quantum Objects in Gravity
    Steffen SauerTUBSUltra-stable cavities for optical clocks
    Tara LiebischPTBClock Network Schemes
    Ernst M. RaselLUHQuantum Gravimeters; Atom-Chip Based Gravimeters and Inertial Sensors
    Stefanie KrokerPTB / TUBSComplex Coupled High Index Waveguide Arrays; Photonic Nanomaterials in the Strong Optomechanical Coupling Regime
    Dennis PhilippZARMGeneral Relativity, relativistic geodesy
    Eva HackmannZARMGeneral Relativity, relativistic geodesy
    Steffen SchönLUHGNSS Frequency Transfer
    Sebastian KokePTBFrequency Transfer Techniques
    Jingxian JiPTBFree-Space Frequency Transfer
    Akbar ShabanlouiLUHGravity field modelling, clock networks, height systems, precise satellite orbit determination
    Jochen KronjägerPTBFree-Space Frequency Transfer; Frequency Transfer Techniques
    Tanja MehlstäublerPTB / LUHSingle and multi-ion clocks
    Jonas KellerPTBSingle and multi-ion clocks
    Erik BenklerPTBOptical frequency combs
    Uwe SterrPTBUltra-stable lasers and optical frequency combs
    Daniele Nicolodi PTBUltra-stable lasers
    Stefan KückPTBSingle photons and quantum communication
    Fei DingLUHQuantum communication
    Nils HuntemannPTB
    Ekkehard PeikPTB
    Shuying ChenPTB
    Carsten KlemptLUH
    Johannes KramerPTB
    Lennart PelzerPTB