Parallel Assembly of Arbitrary Defect-Free Atom Arrays with a Multitweezer Algorithm

Defect-free atom arrays are a precursor for quantum information processing and quantum simulation with neutral atoms. Yet, large-scale defect-free atom arrays can be challenging to realize, due to the losses encountered when rearranging stochastically loaded atoms to achieve a desired target array. Here, we demonstrate a parallel rearrangement algorithm that uses multiple mobile tweezers to independently sort and compress atom arrays in a way that naturally avoids atom collisions. With a high degree of parallelism, our algorithm offers a reduced move complexity compared to both single-tweezer algorithms and existing multitweezer algorithms. We further determine the optimal degree of parallelism to be a balance between an algorithmic speedup and multitweezer inhomogeneity effects. The defect-free probability for a 225-atom array is demonstrated to be as high as 33(1)% in a room-temperature setup after multiple cycles of rearrangement. The algorithm presented here can be implemented for any target array geometry with an underlying periodic structure.

Figure 1

Loading and rearrangement of Rb atoms. (a) The optical tweezer arrays for initial loading and rearrangement are generated by sending 808-$\mathrm{nm}$ (red) and 852-$\mathrm{nm}$ (dark red) laser beams through their respective pair of AODs. Each AOD pair has a ${60}^{\circ }$ relative orientation. (Inset) The precooled cloud of Rb atoms are stochastically loaded into the static tweezers and rearranged with mobile tweezers into defect-free atom arrays. (b) Single-shot fluorescence image of a defect-free triangular array with 225 atoms.

Figure 2

Comparison of the multitweezer PSCA against the single-tweezer modified LSAP algorithm. (a) Basic steps for the assembly of a defect-free kagome array using the PSCA. The red and blue open circles denote reservoir and target sites, respectively. The black filled circles denote atoms, and the green arrows indicate the action of the mobile tweezers. The moves labeled by the same $t_i$ take place simultaneously. (b) Simulated scaling of the number of moves for different compact target array sizes using the PSCA (blue circles) and the modified LSAP algorithm (pink squares). The simulations are run with 10 000 iterations of different random initial loading configurations. (c) Simulated histogram of the number of moves to generate 15-by-15 compact target arrays with different DOPs.

Figure 3

Comparison of the PSCA against MTA1. (a) Simulated scaling of the number of moves for different target array sizes using the PSCA (blue circles) and MTA1 (pink squares). (b) Simulated scaling of the atom rearrangement time for different target array sizes using the PSCA (blue circles) and MTA1 (pink squares). 10 000 iterations of the simulation are run with different random initial loading configurations. The error bars are smaller than the marker size on the plots.

Figure 4

Measured filling fractions achieved with different degrees of parallelism for a $15\times 15$ compact array after one rearrangement cycle. An algorithm with higher DOP performs the rearrangement more quickly, which increases the survival probability of the atoms given the trap lifetime decay (gray curve, $y$ axis on the right, calculated with a precalibrated trap lifetime $\tau =33(1)$ s). However, the higher DOP also leads to more intermodulation, which causes intensity fluctuations that heat up the atoms (light blue squares, data taken with fixed rearrangement time of 200 ms). The overall measured filling fraction, taken with optimized rearrangement time windows, is highest when there is a trade-off between the two effects (dark blue circles).

Figure 5

Improvement of the defect-free probability with multiple cycles of rearrangement for a 225-atom compact target array (DOP = 7). The defect-free probability increased to 33(1)% after ten cycles. The error bars correspond to $1\sigma$ equal-tailed Jeffrey’s prior confidence intervals. (Inset) Measured probability distribution of defects after ten rearrangement cycles.

Figure 6

Gallery of single-shot images of defect-free atom arrays with arbitrary geometries: (a) kagome, (b) honeycomb, (c) link kagome, (d) Sierpinski triangle, and (e) lion head symbol, an icon of Singapore. All scale bars indicate a distance of $10\text{μ}\mathrm{m}$ in the atom plane.