Optical tweezers are convenient experimental tools to trap ultra-cold molecules, but their role in perturbing molecular internal states needs to be understood and managed. To preserve, for example, a superposition of states within the ground electronic state, optical tweezers must apply the same force to each of these states, a so-called magic condition. In molecular systems, magic conditions exist when the frequency of the tweezer light is tuned close to a transition energy between hyperfine resolved rovibrational levels of the ground and an excited electronic state. This is not always convenient as it can lead to unwanted scattering. This is especially crucial for our aim to create high-fidelity quantum logic gates. The studies of the authors of the talk show that efficient trapping of a molecule in an optical potential can be achieved by a selecting laser frequency that has a small detuning (on the order of tens of GHz) relative to an electric-dipole-forbidden molecular transition. Close proximity to this transition allows us to significantly modify the trapping potentials for multiple rotational states without sacrificing coherences among these states. In this talk, Professor Kotochigova will demonstrate that magic trapping conditions for multiple rotational states in several ultracold polar molecules can be created [1]. In addition, the author will show that successful tuning of the magic conditions can be achieved with an applied static electric field and the direction of the laser polarization as well as its ellipticity [2,3,4]. Finally, the author will discuss “unwanted” Raman and Rayleigh scattering in optical tweezers. These processes correspond to the off-resonant absorption of a tweezer photon by the molecule, promoting the molecule to an electronically excited state, followed by spontaneous emission of a photon into a bath mode. For Raman scattering, the initial and final molecular states are different. For Raleigh scattering, the spontaneously emitted photon only differs in direction from the absorbed laser photon and can only lead to dephasing, where the population among states remains unchanged.
[1] Q. Guan, S. L. Cornish, and S. Kotochigova, Phys. Rev. A 103, 043311 (2021).
[2] S. Kotochigova and D. DeMille, Phys. Rev A 82, 063421 (2010).
[3] B. Neyenhuis, B. Yan, J. P. Covey, A. Chotia, A. Petrov, S. Kotochigova, J. Ye, and D. S. Jin, Phys. Rev. Lett. 109, 230403 (2012).
[3] A. Petrov, C. Makrides, and S. Kotochigova, Molec. Phys. 111, 1731-1737 (2013)
