New method for stabilizing cat qubit improves bit-flip error protection by 160x, consolidating the company’s ambitious roadmap to useful quantum computing
Paris, France – 11th March 2025 – Alice & Bob, a frontrunner in the race for fault-tolerant quantum computing, today announced a significant advancement in cat qubit technology to reduce errors in quantum computers.
Cat qubits are a relatively recent innovation in superconducting qubit designs that Alice & Bob has been pioneering since 2020 and that recently made headlines thanks to AWS (Amazon Web Services) release of their first quantum chip Ocelot, which also uses cat qubits to run quantum error correction.
By “squeezing” cat qubits—compressing the quantum state in a way that optimizes error suppression—Alice & Bob has just extended bit-flip error lifetimes by a factor of 160x compared to previous cat qubit implementations, as demonstrated in their latest paper preprint. This significant improvement reinforces the relevance of cat qubits as a scalable solution for fault-tolerant quantum computers.
“Standard cats, those that are not squeezed, offer significant advantages, but their bit-flip improvements come at a cost on the phase-flip error channel,” said Raphael Lescanne, CTO and co-founder of Alice & Bob. “By squeezing our cats, we can enhance bit-flip protection without compromising phase-flip performance, making the correction of phase-flips more manageable in the long run.”
These bit-flip errors, along with phase-flip errors, are major obstacles standing in the way of useful quantum computing at scale. Many current solutions to quantum error correction are highly resource-intensive and require significant hardware overhead. Cat qubits, however, make bit-flips so rare that error correction is reduced from a 2D problem (scaling quadratically) to a 1D problem (scaling linearly), enabling simpler error correction with dramatically fewer resources.
How does Squeezing Works:
Making a can larger makes it robust against bit-flips. However, a higher number of photons also increases the possibility of one of them escaping the system, resulting in a phase-flip error. Because of this tradeoff between bit-flip and phase-flip errors, the number of photons injected needs to be optimized to reduce both error types as much as possible.
“The goal with squeezing is to make every photon count,” said Anil Murani senior researcher and Fellow Expert at Alice & Bob. “Our latest innovation makes our cat qubits more well-rounded and squeezes even greater protection out of them, which will ease the requirements on error correction.”
Running quantum algorithms requires all errors to be corrected for the entire run time. To rule out bit-flips by design, the number of photons of the cat qubit can be increased arbitrarily at the expense of phase-flips, which are left to be corrected by error correction codes. Thanks to squeezing, phase-flips are now minimized given the same bit-flips, so that they can be addressed by error correction more easily. This ensures both error types are corrected, a key requirement for enabling useful applications in chemistry, materials science and more.
Results:
In the experimental demonstration, an average of 4.9 photons in cat qubits without squeezing showed a bit-flip lifetime of 138 milliseconds – a figure that already exceeds the best superconducting platforms. With squeezing, already at 4.1 photons, the bit-flip lifetime jumped to 22 seconds, 160x fewer bit-flips, with no increase in phase-flips.
“By enhancing qubit performance without modifying circuit design, this simple yet effective technique positions our platform to deliver high-fidelity logical qubits at an even smaller fraction of the cost of alternative approaches,” said Lescanne.
Squeezing also resulted in a 50% reduction in Z-gate infidelity and Alice & Bob expects two qubit gates to similarly gain from these performance enhancements. As the platform scales to universal fault-tolerant quantum computing, squeezing cat qubits will reduce the costs required for useful quantum error correction to solve currently intractable problems across many industries.
