Raman pulses for bidirectional Raman cooling

Tatiana Vovk, Semyon S. Rudyi, Andrei V. Ivanov +2 more

H. Che, Ke Deng, Zhilin Xu +3 more

Efficient cooling of trapped ions is a prerequisite for various applications of the ions in precision spectroscopy, quantum information, and coherence control. Raman sideband cooling is an effective method to cool the ions to their motional ground state. We investigate both numerically and experimentally the optimization of Raman sideband cooling strategies and propose an efficient one, which can simplify the experimental setup as well as reduce the number of cooling pulses. Several cooling schemes are tested and compared through numerical simulations. The simulation result shows that the fixed-width pulses and varied-width pulses have almost the same efficiency for both the first-order and the second-order Raman sideband cooling. The optimized strategy is verified experimentally. A single ${^{25}\mathrm{Mg}}^{+}$ ion is trapped in a linear Paul trap and Raman sideband cooled, and the achieved average vibrational quantum numbers under different cooling strategies are evaluated. A good agreement between the experimental result and the simulation result is obtained.

Galina A. Nemova

Gaurav Bahl

Nir Davidson, H. J. Lee, Mark A. Kasevich +1 more

Sequences of stimulated Raman pulses and optical pumping pulses have been previously used to cool atoms to temperatures below the single photon recoil temperature kbTrec = ℏk2/2m, (m the atomic mass, k the propagation vector of the cooling light) in one-dimension.1

Vladimir S. Ivanov, Yu. Rozhdestvensky, Kalle‐Antti Suominen

We demonstrate one-dimensional robust Raman cooling in a three-level $\ensuremath{\Lambda}$-type atom, where the velocity-selective transfer is carried out by a STIRAP pulse. In contrast to the standard Raman method, the excitation profile is insensitive to variations in the pulse duration, whereas its position and width are nevertheless under control. Two different cooling variants are examined and we show that subrecoil temperatures are attainable in both cases.