Robust optical clock transitions in trapped ions using dynamical decoupling

• Published in: New journal of physics 2019-08, Vol.21 (8), p.83040
• Main Authors: Aharon, Nati, Spethmann, Nicolas, Leroux, Ian D, Schmidt, Piet O, Retzker, Alex
• Format: Article
• Language: English
• Subjects: Calcium; Computer simulation; Crystals; Decoupling; dynamical decoupling; Interrogation; multi-ion optical clocks; optical clocks; Physics; Quadrupoles; Robustness (mathematics); Tensors; Variation
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/ab3871

We present a novel method for engineering an optical clock transition that is robust against external field fluctuations and is able to overcome limits resulting from field inhomogeneities. The technique is based on the application of continuous driving fields to form a pair of dressed states essentially free of all relevant shifts. Specifically, the clock transition is robust to magnetic field shifts, quadrupole and other tensor shifts, and amplitude fluctuations of the driving fields. The scheme is applicable to either a single ion or an ensemble of ions, and is relevant for several types of ions, such as 40 Ca + , 88 Sr + , 138 Ba + and 176 Lu + . Taking a spherically symmetric Coulomb crystal formed by 400 40 Ca + ions as an example, we show through numerical simulations that the inhomogeneous linewidth of tens of Hertz in such a crystal together with linear Zeeman shifts of order 10 MHz are reduced to form a linewidth of around 1 Hz. We estimate a two-order-of-magnitude reduction in averaging time compared to state-of-the art single ion frequency references, assuming a probe laser fractional instability of 10 − 15 . Furthermore, a statistical uncertainty reaching 2.9 × 10−16 in 1 s is estimated for a cascaded clock scheme in which the dynamically decoupled Coulomb crystal clock stabilizes the interrogation laser for an 27 Al + clock.