A cryogenic neutral-atom platform with full optical access and 2-hour trap lifetime

Neutral-atom quantum processors are scaling toward thousands of qubits, but increasing system size requires longer atom storage times to facilitate defect-free array sorting. Current experimental setups often force a trade-off between high optical access (needed for manipulation) and long vacuum-limited lifetimes (needed for stability). The authors sought to build a platform that achieves both simultaneously using a simplified cryogenic design.

The researchers constructed a bakeable, ultra-high-vacuum (UHV) chamber primarily made of grade 2 titanium, which has superior outgassing properties compared to standard stainless steel. They integrated a compact, closed-cycle cryostat that cools a single 'cold tip' to 4 K. This cold tip acts as a cryopump to remove residual hydrogen—the primary gas limiting vacuum quality—without requiring a fully enclosed cryogenic environment. This architecture keeps the imaging objectives outside the vacuum chamber, preserving full optical access for laser manipulation and fluorescence imaging.

The platform achieved a vacuum-limited single-atom lifetime of approximately two hours. The authors demonstrated that the cold tip effectively lowers the background pressure even when located 30 cm away from the tweezer array. Unlike previous cryogenic designs, this system shows no measurable degradation in cryopumping efficiency when increasing the total optical power of the tweezer array, suggesting it is well-suited for scaling to arrays of tens of thousands of atoms. The researchers also identified that the strontium oven is a significant source of outgassing, and they established a protocol to regenerate the cold tip when hydrogen adsorption eventually limits performance.

This work provides a scalable, relatively simple, and high-performance architecture for neutral-atom quantum computing. By decoupling the need for cryogenic cooling from the need for optical access, the design allows researchers to use standard commercial optics while benefiting from the long coherence and storage times provided by an ultra-high-vacuum environment. This is a critical step toward building large-scale, defect-free quantum registers.