Southwest Quantum Information and Technology

Tunable frequency comb for identifying vibrational overtones in a trapped molecular ion

Presenting Author: April Reisenfeld, National Institute of Standards and Technology, Boulder
Contributing Author(s): Yu Liu, Peter Chang, Scott Diddams, David Leibrandt, Dietrich Leibfried, and Chin-wen Chou

Efficient transduction of quantum information stored in stationary qubits to photons at telecom wavelengths will enable low-loss transmission of quantum information (QI) in optical fibers and facilitate the realization of a long-distance quantum network. While atomic ions mostly emit photons at wavelengths below 1 m, molecular ions offer transitions in the telecom wavelength range that can be used for efficient transfer of QI between an atomic ion and a molecular ion [Lin, Y. et al. Nature 581, 273–277 (2020)]. Theoretical frequency predictions of such transitions typically have uncertainties of a few-terahertz, making experimental searches for them challenging. Here, we report our effort toward a light source to search for telecom-range transitions in trapped molecular ions or other narrow-band emitters. A highly nonlinear fiber (HNLF) broadens the spectrum of an amplified Er-doped fiber frequency comb, resulting in a frequency comb with 90 nm 3 dB bandwidth. An acousto-optic modulator can shift the center frequency of the comb by more than one free spectral range of the comb, which effectively probes transitions over the entire spectral width in parallel. We first aim to search for the v = 0 to v = 5 vibrational overtone transition in CaH+, which is predicted to lie in the range between 1440 and 1470 nm by ab inito calculations [Abe et al., CPL 521, 31–35 (2012), P. Plessow, private communication]. We achieve an average power of 1.2 µW per comb tooth centered at 1450 nm.

(Session 5 : Thursday from 5:00 pm - 7:00 pm)