Pasqal, French Quantum Computer Company, has successfully loaded over 1,000 atoms in a single shot within their quantum computing setup, a significant leap towards scalable quantum processors. This milestone demonstrates the feasibility of large-scale neutral atom quantum computing and enhances the potential to solve complex optimization problems and quantum simulations.
Key highlights include:
Successful trapping of 1,110 atoms within 2,088 traps
Demonstrated atom-by-atom rearrangement of an 828-atom target array using optical tweezers
Enhanced scalability, paving the way for quantum processors with over 1,000 qubits, with future targets of 10,000 qubits by 2026-2027.
Above - Diagram of the whole setup including a 2D MOT as the atomic source and the cryostat. The interior of the science chamber is detailed in the magnified view (b). (c) Photograph of the objectives mounted on a 300 K support that surrounds the gold-plated copper shield at 35 K. (d) Transverse cross section showing how the objectives are arranged with the two shields at 35 K and 6 K. (e) Photograph illustrating the lower, elongated superconducting (SC) coil for the MOT gradient; it is fixed onto the 6 K shield. (f) Close-up shot of one of the custom, UHV-compatible objectives. (g) Temperature behavior of the first (brown) and second stage (blue) during cool-down.
Above - FIG. 1. (a) Three possible ways to combine the use of microscope objectives and a cryogenic setup with (i) the objectives inside the cryogenic environment; with (ii) the objectives outside the vacuum chamber, or with (iii) the objectives under vacuum but at room temperature. The latter is the solution explored in this work. (b) Averaged fluorescence image of single atoms trapped in a 2088-trap array. (c) Single-shot fluorescence image in the same array, showing 1103 trapped atoms. (d) Rearrangement with a target array of 828 atoms selected from a 1824-trap array; the final array shows a ∼ 95% occupancy
Pasqal's progress marks a significant advancement in the quantum computing industry, aligning with our roadmap towards achieving quantum advantage and collaborating with Fortune 500 companies on high-impact business use cases.
They trapped single rubidium atoms in large arrays of optical tweezers comprising up to 2088 sites in a cryogenic environment at 6 K. The approach relies on the use of microscope objectives that are in-vacuum but at room temperature, in combination with windowless thermal shields into which the objectives are protruding to ensure a cryogenic environment for the trapped atoms. To achieve enough optical power for efficient trapping, we combine two lasers at slightly different wavelengths. They discussed the performance and limitations of their design. Finally, they demonstrate atom-by-atom rearrangement of an 828-atom target array using moving optical tweezers controlled by a field-programmable gate array.
Previously, the record for atom loading has been achieved on arrays of up to a few hundreds of atoms. Extending these results at the scale of thousands of atoms is currently the subject of a major research effort, with a recent breakthrough at the scale of more
than 6,000 atoms. In addition, using a cryogenic environment for the atoms would come with the advantage of a better vacuum and a longer Rydberg state lifetime, especially for the case of circular states. These two advantages directly result in improved register preparation and better fidelity for quantum operations.
However, combining large tweezers arrays with a cryogenic environment remains technically challenging. Firstly, the high laser power required to generate a large-scale tweezers array can result in too strong a thermal load for the cryostat. Secondly, combining high-numerical-aperture, large-field-of-view optics (typically, a refractive microscope objective) together with a cryogenic setup is nontrivial. In this work, Pasqal investigate a possible approach to address those challenges.
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The setup described in this work successfully combines large field-of view microscope objectives and a cryostat, making it possible to realize, in an environment at 6 K, tweezers arrays at the scale of 2000 traps, and to rearrange atomic registers at the 1000-atom scale. However, the quality of the vacuum remains unsatisfactory so far, as collisions with background gas limit the trapping lifetime at the
scale of a few 10 s, which strongly limits the occupancy of the rearranged arrays. In future work, several directions can be explored to tackle this issue, such as the use of activated charcoal to enhance cryopumping, and the inclusion of thin glass windows to occlude the 6-K shield openings. Combined with improvements in the rearrangement procedure, in particular using multiple tweezers in parallel as in, obtaining almost defect-free atom arrays at the 1000-atom scale in a cryogenic environment is within reach in the near future. Finally, the current setup, with the presence of electrodes, ITO coating, and appropriate anti-reflection coatings on viewports, is fully compatible with the requirements for controlled Rydberg excitation, opening exciting prospects for quantum science and technology with very large Rydberg arrays.