Experimental evidence for dipole phonon quantum logic*

Molecules have a richer state space than atoms leading to opportunities for quantum sensing and quantum control, but also challenges for measurement and state preparation. Co-trapped molecular ions and laser-cooled atomic ions overcome these challenges by mapping the molecular measurement onto the atomic ions through the shared motion of the trapped ions. Quantum logic spectroscopy (QLS) performs this mapping at the limit of one molecular ion and one atomic ion. A molecular ion transition is driven by a slghtly off-resonant electromagnetic field to induce motion in the two-ion crystal that can then be readout by the atom. Dipole phonon quantum logic (DPQL) uses a resonance between the motion of the trapped ions and a dipole-allowed transition in the molecule to swap information between the motional modes and the molecular ion. DPQL allows for molecular ion state measurement without the need for molecular ion lasers. The limitation is that the dipole-allowed transition needs to be on the order of the motional frequency of the ions, which is usuall on the order of 1 MHz.  In this talk, I will discuss our experiment looking for DPQL using an Ω-doublet splitting in the rotational states of CaO⁺ and Ca⁺ for readout. I will discuss our current experimental evidence in a room temperature vacuum chamber and plans for a future experiment at cryogenic temperatures.