Quantum computing: Google runs ‘magic state cultivation’ on Willow and reduces errors by a factor of 40

Google Quantum AI has demonstrated on its Willow chip that a filtering protocol produces quantum states with 99.99 per cent logical fidelity, overcoming one of the major hurdles to universal quantum computing.

Google Quantum AI teams announce that they have validated a technique called "magic state cultivation" on their Willow processor in real conditions. The so-called magic states are essential for a quantum computer that corrects errors to run any algorithm, but their manufacture is so expensive that some estimates spent up to 95% of the resources of a future machine.

Filter instead of distilled

The principle is to inject still noisy states into an area of the chip, then to sequence coordinated measurements that rule out defective attempts to preserve only pure states. Google reports a reduction in errors of a factor 40 compared to non-cultivated states and a logical fidelity of 99.99% for T states. The researchers also managed to transfer these states from one corrector code (color code) to another (surface code). The results are published in Science.

The idea was formulated some 20 years ago without practical demonstration. Google recognizes that it remains to be proven that the method is more widespread, but it could significantly reduce the size of the machines needed for useful applications.