Quantum computing just got a stability upgrade.
French quantum computing startup Alice & Bob has achieved a major milestone in qubit stability, potentially reshaping the path toward scalable quantum machines.
The company on Thursday announced that its cat qubits can resist one of the main errors in quantum computers, the bit-flip, for more than one hour. This is a remarkable advance over the previous record of 430 seconds (about seven minutes) set in 2024 on Alice & Bob’s Boson 4 chip.
Quantum computers are extremely sensitive to errors, and bit-flips are one of the two main types that can disrupt calculations.
By extending the bit-flip lifetime to over an hour, Alice & Bob have effectively removed a significant roadblock in building practical fault-tolerant machines.
The breakthrough was achieved on Alice & Bob’s latest qubit design, the Galvanic Cat, which also powers their 12-cat qubit chip Helium 2.
Cat qubits defy decay
“Being able to push the stability of our cat qubits year after year makes us confident that we will deliver on our roadmap,” said Raphael Lescanne, CTO and Co-Founder of Alice & Bob.
“Bit-flip lifetimes are not the only metric that matters, but for cat qubits, they are foundational. The road is still long, but we are advancing fast.”
The team’s improvements spanned software optimizations, experimental techniques, and advanced engineering, enabling bit-flip times far beyond previous levels.
Interestingly, the lifetimes achieved now surpass typical timescales for cosmic ray impacts, suggesting some level of insensitivity by cat qubits to such events.
At a mean photon number of 11, the researchers measured bit-flip times ranging between 33 and 60 minutes at a 95 percent confidence interval.
They were also able to run a Z gate operation on the cat qubit with 94.2 percent fidelity in 26.5 ns, a critical step for error correction.
Hardware needs shrink dramatically
By virtually eliminating one of the two main error types, Alice & Bob’s cat qubits allow for more efficient error-correcting codes that require far fewer physical qubits.
If the bit-flip protection holds during gate operations, the hardware needed for large-scale quantum computers could be reduced by up to 200 times.
“This is a major step toward early fault-tolerant quantum computing with 100 logical qubits, which is our 2030 roadmap target,” the company said.
The target requires a 13-minute bit-flip lifetime during two-qubit gate operations, which the new results exceed by a significant margin.
Superconducting qubits from other companies typically achieve bit-flip times of just 25 milliseconds, making Alice & Bob’s record more than a million times longer.
This massive leap in stability could make quantum devices more reliable and practical for materials science, cryptography, and other applications.
The company now plans to further evaluate the performance of these cat qubits under two-qubit gates, which is a critical requirement for building functional quantum computers.