Precision Spectroscopy, Coherent Manipulation and State-to-State Chemistry of Single Molecular Ions
Recent progress in laser technology, frequency metrology and molecular optics have enabled ultra-precise measurements of molecular frequencies. We present a novel, quantum-logic based, non-destructive state-detection method [1, 2] for single molecular ions trapped in radiofrequency ion traps [3, 4]. Our technique leaves the quantum state of the molecule completely intact, enabling repeated non-invasive measurements on the same molecule and therefore affording an exquisite measurement sensitivity and precision. As an application of our state-detection protocol, we demonstrate a type of “force” spectroscopy [1] on a dipole-allowed transition in N2+. We determine transition properties such as the line center and the Einstein-A coefficient which is validated against the results of previous studies using conventional spectroscopic methods. Although we focus on N2+ as a prototypical example, our scheme is applicable to a wide range of diatomic and polyatomic molecules.
We have further developed a precise, narrow-linewidth laser which will be used to perform precision spectroscopy on dipole-forbidden ro-vibrational transitions [5, 6] using the state detection scheme. By slaving this laser to the Swiss primary frequency standard at METAS in Bern, we aim, in the first attempt, to push the precision of spectroscopic measurements on molecular ions into the range of 10-15, about four to five orders of magnitudes better than the current state of the art [7].
In addition, the possibility for efficient, non-destructive state readout and precision spectroscopy lays the foundation for studies of cold collisions and chemical reactions between molecular ions and neutrals with state control on the single-molecule level. Additionally, it enables state-selected coherent experiments with single trapped molecules for applications in quantum-information [8] and sensing experiments.
[1] M. Sinhal, Z. Meir, K. Najafian, G. Hegi and S. Willitsch, Science, 367(6483), 1213-1218.
[2] K. Najafian, Z. Meir, M. Sinhal and S. Willitsch, arXiv preprint arXiv: 2004.05306.
[3] S. Willitsch, Int. Rev. Phys. Chem. 31, 175 (2012).
[4] K. Mølhave and M. Drewsen, Phys. Rev. A 62, 011401 (2000).
[5] Z. Meir, G. Hegi, K. Najafian, M. Sinhal, and S. Willitsch, Faraday Discuss. 217, 561 (2019).
[6] M. Kajita, Phys. Rev. A 92, 043423 (2015).
[7] S. Alighanbari, M. G. Hansen, V. I. Korobov, and S. Schiller, Nat. Phys. 14, 555 (2018).
[8] S. Wehner, D. Elkouss, and R. Hanson, Science 362, eaam9288 (2018).