Ultracold RbCs molecules in magic traps and optical tweezers

Ultracold polar molecules are an exciting platform for quantum science and technology. The combination of rich internal structure of vibration and rotation, controllable long-range dipole-dipole interactions and strong coupling to applied electric and microwave fields has inspired many applications. These include quantum simulation of strongly interacting many-body systems, the study of quantum magnetism, quantum metrology and molecular clocks, quantum computation, precision tests of fundamental physics and the exploration of ultracold chemistry. Many of these applications require full quantum control of both the internal and motional degrees of freedom of the molecule at the single particle level, combined with traps that support long coherence times for rotational state superpositions.



In Durham, we study ultracold ground-state RbCs molecules formed by associating Rb and Cs atoms using a combination of magnetoassociation and stimulated Raman adiabatic passage. This talk will report on our development of full quantum control of the molecules. Specifically, we will explain how we have mastered the ac Stark shift due to the trapping light through the development of magic-wavelength traps that allow us to tune the anisotropic polarisability of the molecule to zero. This eliminates trap-induced dephasing on rotational transitions and allows us to generate second-scale rotational coherences that give access to controllable dipole-dipole interactions.

We will also report on new experiments that produce single molecules in an array of optical tweezers starting from a single Rb and a single Cs atom. Using this platform, we prepare the molecules in the lowest hyperfine state of the rovibrational ground state and predominantly in the motional ground state of the trap. We demonstrate site-specific addressing and multi-state readout of single molecules. Using mid-sequence detection of molecule formation errors, we also demonstrate rearrangement of molecules to produce defect-free arrays. Finally, we demonstrate a new hybrid platform that combines single ultracold molecules with single Rydberg atoms, opening a myriad of possibilities.