Direct Generation of an Array with 78400 Optical Tweezers Using a Single Metasurface

Abstract

Scalability remains a major challenge in building practical fault-tolerant quantum computers. Currently, the largest number of qubits achieved across leading quantum platforms ranges from hundreds to thousands. In atom arrays, scalability is primarily constrained by the capacity to generate large numbers of optical tweezers, and conventional techniques using acousto-optic deflectors or spatial light modulators struggle to produce arrays much beyond $\sim 10,000$ tweezers. Moreover, these methods require additional microscope objectives to focus the light into micrometer-sized spots, which further complicates system integration and scalability. Here, we demonstrate the experimental generation of an optical tweezer array containing $280\times 280$ spots using a metasurface, nearly an order of magnitude more than most existing systems. The metasurface leverages a large number of subwavelength phase-control pixels to engineer the wavefront of the incident light, enabling both large-scale tweezer generation and direct focusing into micron-scale spots without the need for a microscope. This result shifts the scalability bottleneck for atom arrays from the tweezer generation hardware to the available laser power. Furthermore, the array shows excellent intensity uniformity exceeding $90\%$, making it suitable for homogeneous single-atom loading and paving the way for trapping arrays of more than $10,000$ atoms in the near future.

Figures (4)

• Figure 1: Comparison of technologies for generating optical tweezers. (a) A pair of AODs uses radio-frequency signals to produce acoustic waves that diffract the incident light into a two-dimensional array. (b) An SLM generates arbitrary patterns by encoding a phase hologram on a pixelated liquid-crystal array. Its micron-scale pixel size, however, limits scalability. Both (a) and (b) require a microscope objective to focus the light spots into micrometer-scale optical tweezers. (c) An optical metasurface directly shapes the wavefront of light via a dense array of subwavelength nanostructures, allowing the generation of multiple tightly focused optical tweezers in a compact, lensless configuration.
• Figure 2: Plot of the relative phase shift $\phi$ (left axis) and transmittance $T$ (right axis) of a single meta-atom as a function of meta-atom size $L$, obtained via FDTD simulations.
• Figure 3: Characterization of the metasurface and intensity distributions of the generated optical tweezers. (a) Scanning electron microscope image of the fabricated metasurface. (b) Image of the complete $280 \times 280$ tweezer array with zoomed-in views of representative areas. (c) An image of the metasurface employed in this study, which has a diameter of 5 mm, fabricated on a 10 mm$\times$10 mm substrate
• Figure 4: Characterization of the optical tweezer array generated by the metasurface: (a) Normalized intensity profile across the whole array. (b) Histogram of normalized intensities across the array with a standard deviation of 9.4%. The intensity is obtained from the amplitude of the fitted Airy disk around each optical tweezer. (c) Histogram of the fitted airy disk waist.