The Signal
Alice & Bob Tests Three Cat-Qubit Demonstrators for PROQCIMA
Alice & Bob reports operating three cat-qubit demonstrators for Phase 1 of France’s PROQCIMA programme. The tests covered error-correction operations, but the measured logical error rate has not yet fallen below threshold.
Quantum.world Team · Written with AI · fact-checked ·
Alice & Bob says its three PROQCIMA demonstrators can run key operations in its cat-qubit error-correction architecture. But the company’s own Phase 1 account also draws a limit: its measured logical error rate is not yet below threshold, the point it says the system must reach for error correction to work as intended.
The company published its results on October 20, reporting that it assembled and operated two six-qubit chips and one 12-qubit chip. The tests put several parts of its architecture on real hardware, while leaving the central threshold result outstanding.
Three chips test the correction building blocks
Alice & Bob reports noise-biased CNOT gates between cat qubits, designed to preserve their built-in protection against bit flips. The team also tested measure-and-reset sequences on auxiliary qubits: those operations read the error syndrome and prepare each qubit for another correction cycle. Their performance, the company says, was broadly in line with programme targets.
The demonstrators ran multiple cycles of a distance-3 repetition code using three data qubits. Alice & Bob describes it as the smallest code able to correct a quantum error. The team also measured the logical error rate across the full register and demonstrated a non-Clifford gate on a cat qubit, an operation the company calls a first step toward producing the “magic states” needed for universal fault-tolerant computing.
The logical error rate remains above threshold
Those operations are evidence of hardware tests, not a report that the demonstrators have achieved fault-tolerant operation. Alice & Bob says the logical error rate has not yet dropped below threshold. Its announcement does not give numerical logical-error, gate-fidelity or coherence results, so readers cannot assess the size of the gap from the figures provided.
The company built a digital twin of the processor using measured performance data. Simulations on that model identify improvements needed to operate below the error-correction threshold, starting with extending qubit coherence consistently across the chip. The digital twin therefore points to a next engineering task; it does not change the reported result from the hardware tests.
MnR monitors more than 50 indicators per qubit
Alice & Bob says its proprietary monitoring and recalibration software, MnR, supervised the demonstrators around the clock while the quantum processing unit was idle. The software tracked more than 50 performance indicators per qubit and detected when drift called for recalibration. The company says detecting and correcting drift could previously cost up to a day of operating time, and that MnR keeps processor performance consistent.
The release does not quantify how much operating time the software saved on these demonstrators. Its account instead presents MnR as part of the system used to maintain performance while the team tested the correction operations.
Five companies began the PROQCIMA competition
France’s programme, led by the French Defense Innovation Agency and the Direction générale de l’Armement, aims to develop two universal quantum-computer prototypes, each supporting 1,000 logical qubits and ready for industrialisation by 2032. Alice & Bob, Pasqal, Quandela, Quobly and C12 were selected to take part. The programme plans to narrow the field to three candidates after its first four years, then select two to continue beyond year eight.
Théau Peronnin, CEO of Alice & Bob, said:
“The race for fault-tolerant quantum computing is a question of who will master one of the defining technologies of this century, and France starts from a position of real strength. Our PROQCIMA Phase 1 results show that the cat-qubit approach, combined with Alice & Bob’s expertise, can lead that race and push the frontiers of science.”
Théau Peronnin, CEO, Alice & Bob
For now, the company’s report establishes that three chips ran the listed operations. Its own logical-error measurement remains above threshold.