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A: Fachverband Atomphysik
A 39: Poster – Precision Measurement (joint session Q/A)
A 39.12: Poster
Donnerstag, 5. März 2026, 17:00–19:00, Philo 2. OG
Entanglement-enhanced multi 40Ca+ ion clock — •Bennet Benny1,2, Kai Dietze1,2, Lennart Pelzer1,2, Vincent Barbé1, Ludwig Krinner1,2, Fabian Dawel1,2, Derwell Drapier1, Mirza A. Ali1,2, and Piet O. Schmidt1,2 — 1QUEST, Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany — 2Leibniz Universität Hannover, 30167 Hannover, Germany
State-of-the-art optical atomic clocks based on trapped ions require long interrogation times and ion numbers to achieve low statistical uncertainty, but both methods are limited by various noise sources. Therefore, a small number of entangled ions with Quantum Projection Noise (QPN) below Standard Quantum Limit (SQL) might be beneficial. We demonstrated entanglement gain leading to faster averaging and suppression of magnetic-field noise in 40Ca+ ions in Decoherence-Free Subspace (DFS)[1]. Entanglement also provides an improvement in the measurement uncertainty through a reduction in QPN. The DFS method demonstrated near-lifetime-limited interrogation, but any further gain is suppressed by spontaneous-emission events during interrogation. To address this, we propose an experimental implementation of an entanglement-assisted readout method that employs a 4-tone Mølmer-Sørensen gate based DFS to detect and veto spontaneous-emission events from the clock feedback loop. This approach is designed to demonstrate an enhancement beyond SQL and its scaling of the achievable lock performance with ion numbers[2].
[1] K. Dietze et al., arXiv:2506.11810 (2025)
[2] T. Kielinski et al., Sci. Adv. 10, eadr1439 (2024)
Keywords: Entangled Ion Clock; Beyond standard quantum limit (SQL); Decoherence-Free Subspaces (DFS); Optical Atomic Clocks