Alice and Bob extend qubit stability from 10ms to 10s
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French quantum qubit developer Alice and Bob has dramatically extended the stability of qubits for quantum computers.
The Cat qubit design extends resilience to one quantum error to tens of seconds in research by Alice & Bob and Quantic.
The study, Quantum control of a cat-qubit with bit-flip times exceeding ten seconds, with the Quantic team in Paris demonstrates an important improvement in the stability of superconducting qubits for useful fault-tolerant quantum computing.
The researchers have dramatically extended the bit-flip times from milliseconds to tens of seconds—thousands of times better than any other superconducting qubit type.
Alice & Bob tape out 16 qubit quantum processor
Quantum computers face two types of errors: bit-flips and phase-flips. Cat qubits exponentially reduce bit-flips, which are analogous to classical bit flips in digital computing. As a result, the remaining phase-flips can be addressed more efficiently with simpler error correcting codes.
“This successful collaboration made the most of our cat qubit design to achieve very long bit-flip times while preserving quantum control,” said Raphaël Lescanne, CTO of Alice & Bob. “Although the journey is still unfolding, we remain dedicated to efficiently tackling the challenges of quantum error correction.”
The researchers used Alice & Bob’s ‘Boson 3’ chipset for this record-breaking result, which features a cat qubit design named TomCat. TomCat employs an efficient quantum tomography (measurement) protocol that allows for the control of quantum states without the use of a transmon, a common circuit used by many quantum companies, but one of the major sources of bit-flips for cat qubits. This design also minimizes the footprint of the qubit on the chip, removing drivelines, cables, instruments, making this stable qubit scalable.
The Boson 4 chipset reaches over 7 minutes of bit-flip lifetime and the results can be reproduced by users on Boson 4 over Google Cloud.
Although Alice & Bob’s latest Boson chips are getting closer to the company bit-flip protection targets, Alice & Bob plans to further advance their technology. The next iterations will focus on boosting the cat qubit phase-flip time and readout fidelity to reach the requirements of their latest architecture to deliver a 100 logical qubit quantum computer.
The team demonstrated control of the phase of coherent superpositions while achieving macroscopic bit-flip times, a necessary step to scale these dynamical qubits into fully protected hardware-efficient architectures.
With a system that inherently stabilizes against bit-flips, only phase-flips remain as the significant source of error, which can be corrected more efficiently. Instead of using a two-dimensional code to correct for both error types, a more efficient one-dimensional code addresses the phase flips.
“Alice & Bob is committed to further extending the stability of cat qubits and improving quantum error correction methods,” said Théau Peronnin, CEO of Alice & Bob. “This research highlights the feasibility of prolonged bit-flip times unmatched by other superconducting qubits.”
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