Project B03: Multi-ion spectroscopy for optical clocks

The central goal of project B03 is to develop and implement multi-ensemble, multi-ion spectroscopy to combine the small systematic uncertainty achieved in single ion clocks with short averaging times achievable when probing multiple atoms. Dynamical decoupling and entangling ions will reduce systematic effects and further enhance the signal-to-noise ratio in multi-ion clocks. As a long-term goal we will employ these systems to regularly operate ion clocks at the 10−18 level, enabling spectroscopic tests for physics beyond the Standard Model

Introduction

As the systematic error budgets of ion-based frequency standards continue to improve, ever-longer measurement times are required to average over the statistical noise and obtain a measurement uncertainty that reflects the achievable accuracy. Shorter averaging times can be achieved either by reducing laser phase noise, which currently limits the spectroscopic probe time and hence the observed linewidth of many investigated atomic resonances, or by increasing the number of ions to overcome the fundamental limit on the signal-to-noise ratio of measurements on a single quantum system.

Within this project we pursue three different approaches in three different setups: linear ion chains in a precision trap will enable high-accuracy In+ and Yb+ multi-ion clocks, multiple ensembles of Yb+ ions in spatially separate trap zones will enable dead-time free clock readout, while we will achieve long probe times for a Al+/Ca+ quantum logic clock through pre-stabilisation of the clock laser light using an ensemble of Ca+ ions, realising a multi-ensemble clock. The investigated systems are therefore complementary in their goals, but synergetic in the employed quantum engineering techniques. The project contributes to all of DQ-mat’s core objectives, namely scaling quantum systems, manipulating and characterising quantum systems, composing quantum systems, enhancing quantum sensors and metrology, testing fundamental physics and exploring many-body physics.

Results

During the first two funding periods, we have investigated optimal probe times for a given number of atoms and laser noise, developed novel efficient cooling schemes for dual species clocks based on electromagnetically-induced transparency to reduce time-dilation shifts and evaluated systematic shifts of the Al+ system to 1 ×10−18. We operated an optical reference using dynamical decoupling to mitigate systematic shifts of up to five ions in a crystals, and operated an optical clock based on two Ca+ ions entangled in a decoherence-free sub space

Time dilation shifts due to thermal motion and micromotion are among the major challenges in controlling the dynamics of large ensembles of ions for precision spectroscopy. We therefore investigated micromotion across an ion chain, heating of the motional modes in extended 1D to 3D ion crystals and demonstrated the experimental capability of sorting mixed-species chains for reliable sympathetic cooling conditions. With this the potential of multi-ion clock operation with fractional systematic uncertainties as low as 10-19 was successfully demonstrated. In succeeding three-cornered-hat clock comparisons a first In+/ Yb+ Coulomb crystal clock with a total systematic uncertainty of 2.5*10−18 for a single clock ion and first observations of reduced statistical uncertainties in measurements with up to four clock ions were demonstrated.

We have also started frequency comparisons of the Al+/Ca+ clock, the multi-ion Ca+ and entangled Ca+ reference, as well as the In+ multi-ion clock with the Yb+ single ion clocks and the Sr lattice clock in project B02 (optical clocks).


Publications

Showing results 1 - 20 out of 23

Dawel F, Wilzewski A, Herbers S, Pelzer L, Kramer J, Hild MB et al. Coherent photo-thermal noise cancellation in a dual-wavelength optical cavity for narrow-linewidth laser frequency stabilisation. Optics express. 2024 Feb 14;32(5):7276-7288. doi: 10.48550/arXiv.2311.11610, 10.1364/OE.516433
Krinner L, Dietze K, Pelzer L, Spethmann N, Schmidt PO. Low phase noise cavity transmission self-injection locked diode laser system for atomic physics experiments. Optics express. 2024 Apr 16;32(9):15912-15922. doi: 10.1364/OE.514247
Martínez-Lahuerta VJ, Pelzer L, Dietze K, Krinner L, Schmidt PO, Hammerer K. Quadrupole transitions and quantum gates protected by continuous dynamic decoupling. Quantum Science and Technology. 2024 Jan;9(1):015013. Epub 2023 Nov 10. doi: 10.48550/arXiv.2301.07974, 10.1088/2058-9565/ad085b
Nordmann T, Wickenhagen S, Doležal M, Mehlstäubler TE. Bichromatic UV detection system for atomically-resolved imaging of ions. Review of scientific instruments. 2023 Jun;94(6):063305. Epub 2023 Jun 29. doi: 10.48550/arXiv.2302.02489, 10.1063/5.0145409
Yeh CH, Grensemann KC, Dreissen LS, Fürst HA, Mehlstäubler TE. Robust and scalable rf spectroscopy in first-order magnetic sensitive states at second-long coherence time. New journal of physics. 2023 Oct 3;25(9):093054. doi: 10.48550/arXiv.2306.01486, 10.1088/1367-2630/acfc14
Dreissen LS, Yeh CH, Fuerst HA, Grensemann KC, Mehlstäubler T. Improved bounds on Lorentz violation from composite pulse Ramsey spectroscopy in a trapped ion. Nature Communications. 2022 Nov 27;13(1):7314. doi: 10.1038/s41467-022-34818-0
Martinez-Lahuerta VJ, Eilers S, Mehlstaeubler TE, Schmidt PO, Hammerer K. Ab initio quantum theory of mass defect and time dilation in trapped-ion optical clocks. Physical Review A. 2022 Sept 3;106(3):032803. doi: 10.1103/PhysRevA.106.032803
Kalincev D, Dreissen LS, Kulosa AP, Yeh CH, Fürst HA, Mehlstäubler TE. Motional heating of spatially extended ion crystals. Quantum Science and Technology. 2021 May 7;6(3):034003. doi: 10.1088/2058-9565/abee99
Fürst HA, Yeh CH, Kalincev D, Kulosa AP, Dreissen LS, Lange R et al. Coherent Excitation of the Highly Forbidden Electric Octupole Transition in 172Yb+. Physical review letters. 2020 Oct 16;125(16):163001. doi: 10.1103/PhysRevLett.125.163001
Nordmann T, Didier A, Doležal M, Balling P, Burgermeister T, Mehlstäubler TE. Sub-kelvin temperature management in ion traps for optical clocks. Review of scientific instruments. 2020 Nov 24;91(11):111301. doi: 10.48550/arXiv.2008.04231, 10.1063/5.0024693, 10.1063/5.0160415
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
Aharon N, Spethmann N, Leroux ID, Schmidt PO, Retzker A. Robust optical clock transitions in trapped ions using dynamical decoupling. New Journal of Physics. 2019 Aug;21(8):083040. Epub 2019 Aug 28. doi: 10.1088/1367-2630/ab3871, 10.15488/10415
Didier A, Ignatovich S, Benkler E, Okhapkin M, Mehlstäubler TE. 946-nm Nd:YAG digital-locked laser at 1.1 × 10 −16 in 1 s and transfer-locked to a cryogenic silicon cavity. Optics letters. 2019 Apr 1;44(7):1781-1784. doi: 10.1364/OL.44.001781
Hannig S, Pelzer L, Scharnhorst N, Kramer J, Stepanova M, Xu Z et al. Towards a transportable aluminium ion quantum logic optical clock. Review of Scientific Instruments. 2019 May;90(5):053204. Epub 2019 May 31. doi: 10.48550/arXiv.1901.02250, 10.1063/1.5090583, 10.15488/12800
Keller J, Burgermeister T, Kalincev D, Didier A, Kulosa AP, Nordmann T et al. Controlling systematic frequency uncertainties at the 10-19 level in linear Coulomb crystals. Physical Review A. 2019 Jan 7;99(1):013405. doi: 10.1103/PhysRevA.99.013405
Keller J, Kalincev D, Burgermeister T, Kulosa AP, Didier A, Nordmann T et al. Probing Time Dilation in Coulomb Crystals in a High-Precision Ion Trap. Physical review applied. 2019 Jan 7;11(1):011002. doi: 10.1103/PhysRevApplied.11.011002
Hannig S, Mielke J, Fenske JA, Misera M, Beev N, Ospelkaus C et al. A highly stable monolithic enhancement cavity for second harmonic generation in the ultraviolet. Review of scientific instruments. 2018 Jan;89(1):013106. Epub 2018 Jan 19. doi: 10.48550/arXiv.1709.07188, 10.1063/1.5005515, 10.15488/3075
Kozlov MG, Safronova MS, Crespo López-Urrutia JR, Schmidt PO. Highly charged ions: Optical clocks and applications in fundamental physics. Reviews of Modern Physics. 2018 Dec 4;90(4):045005. doi: 10.1103/RevModPhys.90.045005
Mehlstäubler TE, Grosche G, Lisdat C, Schmidt PO, Denker H. Atomic clocks for geodesy. Reports on Progress in Physics. 2018 Jun;81(6):064401. Epub 2018 Apr 18. doi: 10.48550/arXiv.1803.01585, 10.1088/1361-6633/aab409
Scharnhorst N, Cerrillo J, Kramer J, Leroux ID, Wübbena JB, Retzker A et al. Experimental and theoretical investigation of a multimode cooling scheme using multiple electromagnetically-induced-transparency resonances. Physical Review A. 2018 Aug;98(2):023424. Epub 2018 Aug 27. doi: 10.48550/arXiv.1711.00732, 10.1103/PhysRevA.98.023424
All publications of the Collaborative Research Centre

Project leader

Prof. Dr. Tanja Mehlstäubler
Address
Callinstraße 36
30167 Hannover
Room
323
Prof. Dr. Tanja Mehlstäubler
Address
Callinstraße 36
30167 Hannover
Room
323
Prof. Dr. Piet Oliver Schmidt
Address
Welfengarten 1
30167 Hannover
Building
Room
Address
Welfengarten 1
30167 Hannover
Building
Room

Staff

Dr. Jonas Keller
Address
Bundesallee 100
38116 Braunschweig
Dr. Jonas Keller
Address
Bundesallee 100
38116 Braunschweig
Dr. Johannes Kramer
Dr. Johannes Kramer
Dr. Lennart Pelzer
Dr. Lennart Pelzer
Nimrod Hausser
Nimrod Hausser
Chih-Han Yeh
Chih-Han Yeh