High quality tweezer generation using automated alignment and adaptive optics

The rapid advances are being made in quantum computation with ultracold neutral atoms

trapped in an tweezer array. Two of the core hardware capabilities that has made this progress

possible are spatially fine-tuned control of lasers and diffraction-limited imaging. Advancing

these capabilities is therefore also receiving an increased attention recently. Here, we show how

to automate the delicate optical alignment necessary to produce diffraction limited tweezers [1].

We generalize the elementary technique of cross-walking to multi-variable cross-walking, which

can be implemented without human intervention. Mathematically, this is a variant of the well-

known Alternating Minimization (AM) algorithm in convex optimization and is closely related to

the Gauss-Seidel algorithm. Therefore, we refer to our multi-variable cross-walking algorithm as

the modified AM algorithm. We apply this algorithm to mechanically align high numerical

aperture (NA) objectives and show that we can produce high-quality diffraction-limited tweezers

and point spread functions (PSF). After a coarse alignment, the algorithm takes about 1 hour to

align the optics to produce high-quality tweezers. Moreover, we use the same algorithm to

optimize the shape of a deformable mirror along with the mechanical variables and show that it

can be used to correct for optical aberrations produced, for example, by glass thickness when

producing tweezers and imaging point sources. The shape of the deformable mirror is

parametrized using the first 14 non-trivial Zernike polynomials, and the corresponding

coefficients are optimized together with the mechanical alignment variables. We show PSF with

a Strehl ratio close to 1 and tweezers with a Strehl ratio > 0.8.

[1] Bharath Hebbe Madhusudhana, Katarzyna Krzyzanowska and Malcolm Boshier Optical

tweezer generation using automated alignment and adaptive optics, arXiv: 2401.00860