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Controlling Ground State RbCs Molecules

Ultracold polar molecules offer an exciting new platform for experiments in quantum physics. They offer a unique system combining long-range and anisotropic dipole-dipole interactions, relatively long lifetimes, and rich internal structure. Proposed applications span the fields of ultracold chemistry, precision measurement, quantum simulation and quantum computation.


In this experiment, we are learning to control the internal and external degrees of freedom of ultracold RbCs molecules. We control the motion of the molecules by creating them at ultracold temperatures, and then confining them spatially using an optical trap. We begin experiments with the molecules in their internal ground state, but we can choose to excite the rotation of the molecule using microwave fields. This also allows access to the large molecule-frame electric dipole moment.


To perform our experiments we first produce an ultracold gas of RbCs molecules in their internal ground state. We do this by starting with a high phase-space density mixture of ultracold Rb and Cs atoms. We use magnetoassociation on a Feshbach resonance to produce weakly bound molecules from this mixture. These molecules are then coherently transferred to a single deeply bound rovibrational state of the ground electronic state with near unity efficiency, using stimulated Raman adiabatic passage (STIRAP). The final temperature mirrors that of the original atomic gas, allowing us to exploit the established techniques of atomic cooling to bring molecules into the ultracold regime. 



Funding: 

"Understanding Collisions of Ultracold Polar Molecules" EPSRC EP/P008275/1 (February 2017 - February 2020)

"QSUM: Quantum Science with Ultracold Molecules" EPSRC EP/P01058X/1 (June 2017 - May 2022)