Strasbourg ships a public software twin for a 400-qubit quantum computer still under construction

The Centre Européen de Sciences Quantiques (CESQ), a joint University of Strasbourg and CNRS laboratory, is constructing France's first publicly accessible neutral-atom quantum computer. The target is more than 400 individually controllable ytterbium qubits: atoms held in arrays of focused laser "tweezers" that act as the machine's basic information units, a different hardware track from the superconducting chips used by IBM and Google. The hardware is not yet ready, but the lab has already deployed the piece that decides who outside Strasbourg can prepare work for it: a software twin of the physical processor.

The twin, built by QPerfect, a wholly owned subsidiary of BTQ Technologies (Nasdaq: BTQ; Cboe CA: BTQ), runs on QPerfect's MIMIQ simulation platform. It mirrors the aQCess processor's native gate set, the instruction-set architecture (ISA) the hardware will accept, the dynamics of moving atoms between trap sites, and the noise profiles that have been measured on the real machine. A researcher can write a circuit on the twin, see how it performs against the same imperfections the physical array will produce, and iterate before any atoms are touched. QPerfect is also contributing its Quantum Logic Unit (QLU) compilation and error-correction stack, which the company says will move into the physical hardware control loop as the system scales toward 400+ qubits.

The platform is named aQCess, for Atomic Quantum Computing as a Service. Funding flows through France's National Strategy for Quantum, via the ANR Equipex+ equipment-of-excellence grant and the PEPR-Quantique priority research program. The structural choice matters: the twin and the hardware are funded as a single public-infrastructure stack, not as a vendor product line. QPerfect is one vendor inside that stack, not the operator of the program.

CESQ is co-coordinated by Shannon Whitlock and Guido Pupillo. Whitlock's group published early Rydberg-array and logical-qubit optimization work in PRX Quantum in 2023, the same hardware lineage aQCess extends. The choice of ytterbium over the more common rubidium follows the same logic: ytterbium's narrow optical transitions make it easier to address individual atoms inside a dense array, which is the engineering problem a 400-qubit machine actually solves.

The open question, which the primary corporate release and BTQ's 6-K filing on EDGAR do not resolve, is who outside the consortium actually qualifies to use aQCess. If access is restricted to the 18 partners and their affiliates, the digital twin still functions as a productivity tool for the network, and the public-infrastructure framing is half-true. If outside researchers and startups can apply on published criteria, the twin is the wedge that converts sovereign funding into an actual public-research surface, the way CERN's compute grid turned accelerator physics into a multi-decade outside-user program. The Quantum Insider's same-day coverage treats aQCess as a public cloud offering; that framing has not been independently confirmed by CESQ, and the QCR pickup restates the release without adding access-model detail.

The hardware target, 400+ individually controllable ytterbium qubits, is a stretch. Neutral-atom arrays have crossed the 1,000-atom mark in academic settings, but the engineering for stable, individually addressed, low-loss operation at that scale, plus the calibration required to make the digital twin's noise profiles meaningful, is the gating step. CESQ has not published a public delivery date for the 400+ array, and the partnership announcement is not a hardware milestone. What it does establish is a sequencing choice: build the software surface first, so that when the atoms arrive, the science is already queued.