Toward quantum-logic spectroscopy of single molecular ions in a cryogenic ion trap

Quantum state control of molecules has applications including tests of fundamental physics and quantum information processing, but molecules’ additional degrees of freedom make the control required for these applications more challenging than for atoms. In our group, the application of quantum-logic spectroscopy (QLS) in an ion trap has enabled preparation and coherent manipulation of pure molecular quantum states of a single CaH⁺ ion [1]. Moving forward, we would like to expand the variety of molecular ions we can study and reduce the detrimental effects of background gas collisions and black-body radiation seen in a room-temperature environment. Here, we present progress in the construction and operation of a cryogenic ion trap apparatus for loading a broad range of molecular ions and achieving better control of their states. Molecules are injected via a molecular beam source to be ionized and co-trapped with an atomic ion for QLS. We discuss ongoing investigation into versatile methods of ionization and the forthcoming integration of a closed-cycle cryostat for cryogenic operation.

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