Google Quantum AI cuts magic-state errors about 40-fold on Willow with state cultivation

Google Quantum AI/Willow and error-correction roadmap

Google Quantum AI reports that magic state cultivation works on its Willow processor, a technique that filters flawed attempts to make the special states that universal quantum computers need. The team reports a logical fidelity of 99.99% and says the work, published in Science, is still at small scale.

• Magic states are needed for universal quantum computing but are costly to make; the authors cite estimates that up to 95% of a machine's capacity could go to producing them.
• Cultivation uses coordinated error-checking measurements as a filter, reducing errors about 40-fold compared with un-cultivated states.
• The team also showed grafting: moving a state from a distance-3 color code to a distance-5 surface code on the hardware.
• The authors say cultivation must be shown at larger scale before it is realistic for practical quantum computers.