Resonant charge-dipole interaction between Rydberg Rb atoms and KRb molecules*

Resonant interactions between quantum systems facilitate energy exchange and entanglement, which provide the basis for many applications in the field of quantum simulation, quantum information, and quantum computation. Of particular interest is the resonant electric dipolar interactions between polar molecules and Rydberg atoms. Here, we probe into the resonant interaction between ⁴⁰K⁸⁷Rb molecules and Rydberg ⁸⁷Rb atoms in an ensemble. Through state-selective ionization detection of KRb molecules, we demonstrate the resonant transfer nature of the interface by directly measuring the presence of rotation excitation. To characterize the coupling strength quantitatively, we measure the broadening of the Rb Rydberg excitation spectrum as we vary the pairwise detuning between the KRb molecules and Rydberg Rb atoms. The observed spectral broadening is too large to be explained purely by dipole-dipole interaction. We developed a calculation based on a charge-dipole Hamiltonian that accurately captures the results.  Overall, the experimental observations demonstrate resonant interactions between Rydberg atoms and polar molecules that extend beyond dipole-dipole interactions. To accurately capture these results, we developed a theory based on a charge-dipole Hamiltonian. Our findings pave the way for a controllable interface between polar bi-alkali molecules and Rydberg atoms, enabling various quantum applications.