Enhancing molecular control using Rydberg atoms

Molecules cooled to within a millionth of a degree of absolute zero offer a wealth of fascinating possibilities for the exploration of fundamental science, as well as new opportunities to test our understanding of quantum theory and the behaviour of matter at the smallest of scales. Accordingly, many groups around the world are now investigating ultracold molecules and the field is advancing rapidly. Unlike ground-state atoms, molecules can possess an electric dipole moment, leading to tunable long-range interactions and strong coupling to microwave fields. Molecules also offer a rich structure of long-lived internal states associated with rotational and vibrational degrees of freedom. These properties have stimulated applications ranging from sensitive tests of physics beyond the Standard Model and ultracold chemistry to investigations of many-body physics and quantum magnetism. The richness of molecules presents many experimental challenges, however, particularly as we seek to achieve full quantum control over both their internal and motional degrees of freedom. Many of these challenges stem from the lack of a true cycling transition in molecules, which makes their cooling and detection more difficult. We have pioneered an approach that circumvents this problem by associating pre-cooled atoms to form molecules, which are detected by dissociation back into the constituent atoms. We have recently extended this approach to the assembly of individual RbCs molecules from single Rb and Cs atoms using optical tweezers. This technology offers a powerful way to manipulate individual particles and to organise them into perfectly ordered arrays. It has been widely employed for atoms, but only a handful of experiments have applied the technology to ground-state molecules and several challenges still exist. These include: (1) the non-destructive detection of individual molecules, necessary for their rearrangement into perfectly ordered arrays and (2) engineering quantum entanglement between neighbouring molecules for applications ranging from quantum-enhanced sensing to quantum information processing. In this project, we will address these key challenges using an innovative hybrid platform that combines ultracold molecules and Rydberg atoms in optical tweezers. In a Rydberg atom, one electron is excited to a state where it is very far from the nucleus, leading to greatly exaggerated properties. We propose to leverage these properties to engineer strong controlled interactions between a single Rydberg atom and a single polar molecule. We will then harness these interactions to overcome the challenges above. Specifically, our objectives are to: (a) Create 2D tweezer arrays of polar molecules and atoms which will be excited to Rydberg states. (b) Study the strong resonant dipolar interactions between a Rydberg atom and a polar molecule and explore the creation of Giant Polyatomic Rydberg Molecules. (c) Exploit the enhanced interactions between Rydberg atoms and polar molecules to detect the presence of a molecule and use this capability to rearrange molecules into perfectly ordered arrays. (d) To use the strong interactions of a Rydberg atom to engineer entanglement between polar molecules. Through these objectives we will advance our fundamental understanding of ultracold molecules and their interactions with Rydberg atoms. Our techniques will be applicable to other systems and exploitable for quantum-enhanced sensing protocols. Our outcomes will contribute to the development of molecular quantum simulators, impacting a wide range of beneficiaries in the scientific community. More broadly, our research will provide underpinning quantum science and technical advances relevant to the quantum technology community.