Letter | Published:

Preparation and coherent manipulation of pure quantum states of a single molecular ion

Nature volume 545, pages 203207 (11 May 2017) | Download Citation

Abstract

Laser cooling and trapping of atoms and atomic ions has led to advances including the observation of exotic phases of matter1,2, the development of precision sensors3 and state-of-the-art atomic clocks4. The same level of control in molecules could also lead to important developments such as controlled chemical reactions and sensitive probes of fundamental theories5, but the vibrational and rotational degrees of freedom in molecules pose a challenge for controlling their quantum mechanical states. Here we use quantum-logic spectroscopy6, which maps quantum information between two ion species, to prepare and non-destructively detect quantum mechanical states in molecular ions7. We develop a general technique for optical pumping and preparation of the molecule into a pure initial state. This enables us to observe high-resolution spectra in a single ion (CaH+) and coherent phenomena such as Rabi flopping and Ramsey fringes. The protocol requires a single, far-off-resonant laser that is not specific to the molecule, so many other molecular ions, including polyatomic species, could be treated using the same methods in the same apparatus by changing the molecular source. Combined with the long interrogation times afforded by ion traps, a broad range of molecular ions could be studied with unprecedented control and precision. Our technique thus represents a critical step towards applications such as precision molecular spectroscopy, stringent tests of fundamental physics, quantum computing and precision control of molecular dynamics8.

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Acknowledgements

We thank K. C. Cossel, Y. Wan and D. J. Wineland for comments on the manuscript. This work was supported by the US Army Research Office and the NIST quantum information programme. C.K. acknowledges support from the Alexander von Humboldt foundation. P.N.P. acknowledges support by the state of Baden-Württemberg through bwHPC. This is a contribution of the National Institute of Standards and Technology, not subject to US copyright.

Author information

Affiliations

  1. Time and Frequency Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA

    • Chin-wen Chou
    • , Christoph Kurz
    • , David B. Hume
    • , David R. Leibrandt
    •  & Dietrich Leibfried
  2. Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany

    • Philipp N. Plessow
  3. University of Colorado, Boulder, Colorado, USA

    • David R. Leibrandt

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Contributions

C.-w.C. and D.L. conceived and designed the experiments. C.-w.C. and C.K. developed components of the experimental apparatus, and collected and analysed data. C.-w.C. and D.L. wrote the manuscript. D.B.H. and D.R.L. contributed to the development of experimental methods and pulse sequences. P.N.P. computed the molecular constants and level structure. All authors provided suggestions for the experiments, discussed the results and contributed to editing the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Chin-wen Chou.

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https://doi.org/10.1038/nature22338

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