Ultracold RbCs Molecules: Robust Storage Qubits and Rotationally Magic Traps

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• Prof Simon L. Cornish, Department of Physics, Durham University
• Tuesday 01 November 2022, 11:00-12:30
• Rutherford Seminar Room B (Room 980).

If you have a question about this talk, please contact Moumita Das.

Ultracold polar molecules offer many exciting opportunities in the fields of quantum computation, quantum simulation and fundamental studies of quantum matter. Many of these applications utilize the rotational states of the molecule and rely on long rotational coherence times. Achieving this in experiments has so far proved challenging, however, owing to the presence of large differential light shifts between rotational levels that result from the anisotropic molecular polarizability. We explore these light shifts using RbCs molecules confined in an optical trap. We use precision microwave spectroscopy of the rotational transition to probe the AC Stark shifts in the trap and reveal a rich energy structure with many avoided crossings between hyperfine states. We show that hyperfine states in the rotational ground state may be used to engineer robust storage qubits in the molecules and using Ramsey interferometry demonstrate coherence times exceeding 5.6 s at the 95% confidence level. We then show that similar coherence times should be achievable using a magic-wavelength optical lattice, where the polarizabilities are identical for two (or more) rotational states. We report the development of such a magic trap at a wavelength of 1146 nm. This wavelength lies between the X1Sigma to b3Pi vibronic transitions, allowing the anisotropic component of the polarizability to be tuned to zero. We present spectroscopy of the X1Sigma to b3Pi transitions and show that the differential shift of the N = 0 to N = 1 rotational transition can be tuned to be zero in the magic trap for a detuning of approximately 185 GHz from the X1Sigma(v =0;N =0) to b3Pi(v’ =0;N’ =1) transition. Finally, we will briefly describe ongoing experiments to image and address single molecules in ordered arrays for applications in the field of quantum simulation, including exciting new results on the association of a single molecule in optical tweezers.

This talk is part of the AMOP list series.

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