Optimization of Holographic Arrays of Optical Tweezers for Ultra-Precise Manipulation of Atoms

Optical tweezers are a major tool for the manipulation of individual cold atoms, with various applications such as quantum chemistry, metrology, or quantum simulation and computing. In most experiments, such as the one relying on Rydberg blockade, laser-cooled atoms are left in a state of thermal motion in the tweezers, where their finite temperature (typical several tens of μK) makes them explore the bottom ~10 % of the trap (depth of 0.5-1 mK). For more demanding experiments (e.g., to assemble molecules or for metrology), the atoms can be further cooled to the motional ground-state of the tweezers (for example with Raman sideband cooling). In that case, thermal fluctuations are suppressed and the atom’s positioning is only limited by quantum fluctuation, i.e., the finite size of the tweezers ground-state wavefunction.

For ultrafast Rydberg experiments [1], even these remaining quantum fluctuations affect the dynamics of Rydberg atoms directly interacting via the dipole-dipole coupling. To further suppress quantum fluctuations, we create squeezed state of motions that allows to push beyond the standard quantum limit of position uncertainty. The manipulation of these delicate quantum states of motion requires a much-improved control on the tweezers shape and on its homogeneity over an atomic array. I will introduce several techniques to precisely measure the shape of the tweezers by interrogating the atoms, and then adjust the computer-generated hologram creating the tweezers array.

This optimization of the hologram allows an improvement by more than one order of magnitude of the tweezers shape and opens the path for ultra-precise manipulation of atoms through the creation of squeezed state of motion or the application of “motion-echo” techniques.