Feedback Cooling and Thermometry of a Single Trapped Ion Using a Knife Edge

• URL: http://arxiv.org/abs/2512.16368v1
• Date: Thu, 18 Dec 2025 10:08:28 GMT
• Title: Feedback Cooling and Thermometry of a Single Trapped Ion Using a Knife Edge
• Authors: Hans Dang, Sebastian Luff, Martin Fischer, Markus Sondermann, Gerd Leuchs,
• Abstract summary: We report on the first feedback cooling of a single trapped ion below the Doppler limit of $hbar/2 k_mathrmB$.<n>The motion of a single ion is monitored in real-time and cooled up to 9-times below the Doppler cooling temperature by applying electronic feedback.
• Score: 0.10874100424278171
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We report on the first feedback cooling of a single trapped ion below the Doppler limit of $\hbarΓ/2 k_\mathrm{B}$. The motion of a single ion is monitored in real-time and cooled up to 9-times below the Doppler cooling temperature by applying electronic feedback. Real-time motion detection is implemented by imaging the fluorescence photons emitted by the ion onto a knife edge and detecting the transmitted light, a method used so far to cool trapped nanoparticles. The intensity modulation of the fluorescence resulting from the ion motion is used to generate and apply the feedback signal and also to determine the ion temperature. The method benefits from a high rate of detected scattered photons, which can be a challenge, and which we address by using a parabolic mirror for collecting the fluorescence.

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