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Poster Session

Poster Session II

4:00 pm – 6:00 pm, Wednesday June 18 Session H00 Oregon Convention Center, Exhibit Hall E
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Precision frequency-comb vibrational spectroscopy of a single molecular ion

Poster 9
Presenter: Zhimin Liu (National Institute of Standards and Technology Boulder)
Authors: Joaquin Berrocal Sanchez (National Institute of Standards and Technology), Yu Liu (University of Maryland College Park), Peter Chang (University of Colorado, Boulder), Sichong Ma (University of Colorado, Boulder), Tsung-Han Wu (University of Colorado, Boulder), April Reisenfeld (National Institute of Standards and Technology, Boulder), Dietrich Leibfried (National Institute of Standards and Technology Boulder), Scott Diddams (University of Colorado, Boulder), Chin-wen Chou (National Institute of Standards and Technology (NIST))

The ability to coherently control molecular degrees of freedom can open many new opportunities for applications, including investigating elementary chemical reaction mechanisms [1], testing fundamental physics [2], and transducing quantum information between qubits on different platforms [3]. Quantum-logic spectroscopy (QLS) offers a method to study and manipulate many species of molecular ions with high precision [4]. Here, we report our ongoing effort toward precision spectroscopy of vibrational transitions in a single CaH⁺ ion by using QLS. Starting with a CaH⁺ efficiently prepared in a single quantum state [5], we use infrared frequency combs to coherently drive, efficiently search for, and characterize narrow vibrational transitions in CaH+. We have characterized v = 0 -> 5 overtone transitions with single quantum-state resolution at ~1450 nm, reaching below one part in 10¹³ statistical uncertainty in their frequencies. We have also driven v = 0 -> 7 overtone transitions near 1070 nm and are currently in the process of accurately determining their unperturbed frequencies. In addition to reaching vibrational excited states via one-photon transitions, we are developing two branches of broadband frequency combs to drive numerous two-photon Raman transitions between adjacent vibrational states in CaH+. With sufficient bandwidth in each branch, many comb teeth pairs with correct frequency differences can contribute constructively to collectively drive the transitions [6]. This promises versatile control over molecular vibrations, and can serve as a proof of principle for other molecular ion species.

[1] S. Haze et al., Nat. Phys. 21.228 (2025)

[2] T. Roussy et al., Science 381, 46-50 (2023)

[3] Y. Lin et al., Nature 581, 273 (2020)

[4] C. -W. Chou et al., Nature 545, 203 (2017)

[5] Y. Liu et al., Science 385, 790-795 (2024)

[6] C. -W. Chou et al., Science 367, 6485 (2020)

Funding acknowledgement

We acknowledge support from the Army Research Office under Grant W911NF-19-1-0172 and the Air Force Office of Scientific Research under Grant FA9550-23-1-0035.

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