Precision determination of the ground-state hyperfine splitting of trapped ¹¹³Cd⁺ ions

Abstract

We measured the ground-state hyperfine splitting of trapped 113 C d + ions to be 15199862855.02799(27) Hz with a fractional uncertainty of 1.8 × 10 − 14 . The ions were trapped and laser-cooled in a linear quadrupole Paul trap. The fractional frequency stability was measured to be 4.2 × 10 − 13 / τ , obtained from Ramsey fringes of high signal-to-noise ratios and taken over a measurement time of nearly 5 h, which is close to the short-term stability limit estimated from the Dick effect. Our result is consistent with previously reported values, but the measurement precision is four times better than the best result obtained to date.

High-Performance Microwave Frequency Standard Based on Sympathetically Cooled Ions

“…The lowest temperature was 36(5) mK, corresponding to Gaussian linewidth of 17.8(1.3) MHz. The temperature is an order of magnitude smaller than that registered in our previous laser-cooled cadmium frequency standard (654 mK) [13].…”

“…After cooling the trapped ions, we obtained the Rabi and Ramsey fringes of the clock transition signal by microwave interrogation. Timing sequences for the Ramsey spectroscopy in the traditional laser-cooled 113 Cd + frequency standard [13] and in the sympathetically-cooled 113 Cd + frequency standard are presented in Figure 5. A typical Ramsey fringe is shown is Figure 6.…”

“…5. Timing sequences for Ramsey's separated oscillatory field method for (a) a traditional laser-cooled 113 Cd + frequency standard [13] and (b) a sympathetically-cooled 113 Cd + frequency standard. Dead time marked with a gray background.…”

“…Trapped-ion clocks constitute promising candidates for the next generation microwave atomic clocks due to the advantages of compactness, high transportability, and high performance. To date, ion frequency standards based on 199 Hg + [5, 6, 9, 10], 113 Cd + [11][12][13], 171 Yb + [14 -16] have brought about considerable progress.…”

“…However, prior to our work, the only sympathetically-cooled ion microwave frequency standard realized was that constructed by J. J. Bollinger and colleagues using a Penning trap with Be + sympathetically cooled by Mg + [25]. In past work, we have demonstrated the laser-cooled cadmium ion microwave frequency standard [11][12][13], and have made much progress in sympathetically-cooled large ion crystals [26][27][28].…”