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arXiv · 2306.01670

Cold highly charged ions in a radio-frequency trap with superconducting magnetic shielding

Elwin A. Dijck·Christian Warnecke·Malte Wehrheim·Ruben B. Henninger·Julia Eff·Kostas Georgiou·Andrea Graf·Stepan Kokh·Lakshmi P. Kozhiparambil Sajith·Christopher Mayo·Vera M. Schäfer·Claudia Volk·Piet O. Schmidt·Thomas Pfeifer·José R. Crespo López-Urrutia
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Abstract

We implement sympathetic cooling of highly charged ions (HCI) by fully enclosing a linear Paul trap within a superconducting radio-frequency resonator. A quantization magnetic field applied while cooling down into the superconducting state remains present in the trap for centuries and external electromagnetic fluctuations are greatly suppressed. A magnetic field decay rate at the 10$^{-10}$ s$^{-1}$ level is found using trapped Doppler-cooled Be$^+$ ions as hyperfine-structure (hfs) qubits. Ramsey interferometry and spin-echo measurements on magnetically-sensitive hfs transitions yield coherence times of >400 ms, showing excellent passive shielding at frequencies down to DC. For sympathetic cooling of HCI, we extract them from an electron beam ion trap (EBIT) and co-crystallize one together with Doppler-cooled Be$^+$ ions. By subsequently ejecting all but one Be$^+$ ions, we prepare single HCI for quantum logic spectroscopy towards frequency metrology and qubit operations with a great variety of HCI species.

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Elwin A. Dijck, Christian Warnecke, Malte Wehrheim, Ruben B. Henninger, Julia Eff, Kostas Georgiou, Andrea Graf, Stepan Kokh, Lakshmi P. Kozhiparambil Sajith, Christopher Mayo, Vera M. Schäfer, Claudia Volk, Piet O. Schmidt, Thomas Pfeifer, José R. Crespo López-Urrutia. 2023-06-02. Cold highly charged ions in a radio-frequency trap with superconducting magnetic shielding. https://doi.org/10.1063/5.0160537

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