Radio frequency sideband cooling and sympathetic cooling of trapped ions in a static magnetic field gradient

Abstract

We report a detailed investigation on near-ground state cooling of one and two trapped atomic ions. We introduce a simple sideband cooling method for confined atoms and ions, using RF radiation applied to bare ionic states in a static magnetic field gradient, and demonstrate its application to ions confined at secular trap frequencies, ${\mathit{\omega }}_z\approx 2\mathit{\pi }\times 117$ kHz. For a single ${}^{171}$Yb${}^{+}$ ion, the sideband cooling cycle reduces the average phonon number, $〈n〉$ from the Doppler limit to $〈n〉=$ 0.30(12). This is in agreement with the theoretically estimated lowest achievable phonon number in this experiment. We extend this method of RF sideband cooling to a system of two ${}^{171}$Yb${}^{+}$ ions, resulting in a phonon number of $〈n〉=$ 1.1(7) in the centre-of-mass mode. Furthermore, we demonstrate the first realization of sympathetic RF sideband cooling of an ion crystal consisting of two individually addressable identical isotopes of the same species.

Keywords:

• Ion trapping
• Doppler cooling
• sideband cooling
• RF radiation
• sympathetic cooling
• individually addressable qubit

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft and from Bundesministerium für Bildung und Forschung [grant number 16KIS0128]. G. S. G. was also supported from the European Commission’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Action [grant number 657261].