Research project B06 – SFB 1227 DQ-mat – Leibniz University Hannover

Introduction

We aim to apply laser-based quantum logic techniques developed in the context of ion-trap quantum computing for cooling and readout of single (anti-)protons. The quantum logic approach relies on manipulating and detecting the (anti-)proton indirectly through a co-trapped atomic “logic” ion (Be⁺ in our case). This allows for ground state cooling of (anti-)protons, with a corresponding gain of more than 3 orders of magnitude in terms of particle localisation and a much faster readout speed (by two to three orders of magnitude). Both will be highly beneficial in the identification, characterisation and suppression of systematic effects and in achieving lower statistical uncertainties. The system offers the intriguing possibility of using the “logic” ion as a flywheel for the magnetic field stabilisation in a g-factor comparison. This project contributes directly to the DQ-mat core goals of composing quantum systems, enhancing quantum sensors & metrology and testing fundamental physics.

Results

We have built and commissioned a cryogenic 5 T superconducting magnet Penning trap system, loaded single Be⁺ ions and demonstrated laser cooling and mode coupling. We have proposed a method for elementary quantum logic gates on (anti-)protons in Penning traps and, based on this, an implementation of quantum logic spectroscopy (QLS) of (anti-)protons to test CPT symmetry. We have analyzed the implications for constraining Standard Model Extension (SME) coefficients and CPT tests. A key milestone for the implementation of these methods was to demonstrate two complementary methods for stimulated-Raman optical control of ions using a UV femtosecond frequency comb and 140 GHz offset phase-locked CW UV lasers. Using the latter, we have implemented single-ion resolved-sideband spectroscopy, which has culminated in the demonstration of single-ion ground state cooling, one of only two experiments worldwide to achieve this essential prerequisite for the implementation of quantum logic spectroscopy.

We were also able to demonstrate, for the first time in Penning traps, another key prerequisite – fast adiabatic transport without a detectable energy increase, which is required to connect trap zones of different functionality for QLS. Ongoing experiments explore Coulomb coupling of Be⁺ ions in a double-well potential so that, in a second step, the required (anti-)proton– Be⁺ coupling for sympathetic cooling and QLS can be demonstrated.

We have contributed to a series of ground-breaking measurements of the BASE (Baryon-Antibaryon Symmetry Experiment) collaboration on antiproton g-factor measurements and CPT symmetry tests. The BASE measurements have placed limits on potential interactions between axion-like dark matter on the one hand and antimatter and photons on the other hand. We have collaborated with BASE-Mainz on the demonstration of a complementary resonator-based sympathetic laser cooling technique with protons.

Publications

Showing results 1 - 6 out of 6

Cornejo JM, Brombacher J, Coenders JA, Von Boehn M, Meiners T, Niemann M et al. Resolved-sideband cooling of a single Be + 9 ion in a cryogenic multi-Penning-trap for discrete symmetry tests with (anti-)protons. Physical Review Research. 2024 Sept 3;6(3):033233. doi: 10.1103/PhysRevResearch.6.033233

Cornejo JM, Brombacher J, Coenders JA, Von Boehn M, Meiners T, Niemann M et al. Optical stimulated-Raman sideband spectroscopy of a single ^9Be^+ ion in a Penning trap. Physical Review Research. 2023 Sept 28;5(3):033226. doi: 10.48550/arXiv.2308.09362, 10.1103/PhysRevResearch.5.033226

Mielke J, Pick J, Coenders JA, Meiners T, Niemann M, Cornejo JM et al. 139 GHz UV phase-locked Raman laser system for thermometry and sideband cooling of 9Be+ ions in a Penning trap. Journal of Physics B: Atomic, Molecular and Optical Physics. 2021 Nov 15;54(19):195402. doi: 10.1088/1361-6455/ac319d

Nitzschke D, Schulte M, Niemann M, Cornejo JM, Ulmer S, Lehnert R et al. Elementary laser‐less quantum logic operations with (anti‐)protons in penning traps. Advanced Quantum Technologies. 2020 Jun 16;3(11):1900133. doi: 10.1002/qute.201900133

Paschke AG, Zarantonello G, Hahn H, Lang T, Manzoni C, Marangoni M et al. Versatile Control of Be+ 9 Ions Using a Spectrally Tailored UV Frequency Comb. Physical Review Letters. 2019 Mar 29;122(12):123606. doi: 10.48550/arXiv.1903.02965, 10.1103/PhysRevLett.122.123606

Meiners T, Niemann M, Mielke J, Borchert M, Pulido N, Cornejo JM et al. Towards sympathetic cooling of single (anti-)protons. Hyperfine Interactions. 2018 Jul 9;239(1):26. doi: 10.1007/s10751-018-1502-6

All publications of the Collaborative Research Centre

Overview