Quantum-logic precision spectroscopy and control of trapped molecules

(See attached pdf file)

Trapped ions are among the best-controlled quantum systems. However, for molecules, a similar degree of control currently lacks due to their complex energy-level structure. Quantum-logic protocols in which atomic ions serve as probes for molecular ions are promising for achieving this level of control. Here, I will describe our experimental results in achieving >99% fidelity in the quantum-nondemolition state detection of the nitrogen ion's electronic, vibration, and rotation ground state [1], thus making a crucial step towards the coherent manipulation of molecular quantum states. We further exploited our quantumlogic protocol for hyperfine and Zeeman resolved state identification and preparation in a complex region of the molecular spectrum, mimicking the situation encountered with polyatomic molecules [2].
The quantum control of rotation and vibration of molecules will significantly enhance the precision of molecular spectroscopy. It will open up opportunities for creating new time standards in the THz domain [3], searching new physics such as possible time variation in the proton-to-electron mass ratio, and encoding quantum information in molecular qubits at
telecom frequencies for quantum-communication applications.

[1] Sinhal, ZM, Najafian, Hegi, Willitsch, Science 367, 1213 (2020).
[2] Najafian, ZM, Sinhal, Willitsch, Nat. Commun. 11, 4470 (2020).
[3] Najafian, ZM, Willitsch, Phys. Chem. 22, 23083 (2020).
[4] ZM, Hegi, Najafian, Sinhal, Willitsch, Faraday Discuss. 217, 561 (2019).