Google unveils Willow, demonstrating below-threshold quantum error correction

Google Quantum AI/Willow and error-correction roadmap

Google's 105-qubit Willow chip achieved a historic milestone in quantum error correction: error rates dropped by half as the device scaled from 3x3 to 7x7 qubit grids, demonstrating the long-sought below-threshold behaviour. The chip ran a random-circuit benchmark in under five minutes that would require a supercomputer an estimated 10 septillion years.

• Error rates halved when grid size expanded from 3x3 to 5x5 to 7x7, proving larger systems reduce rather than amplify errors.
• Qubit coherence time (T1) improved ~5x to 100 microseconds; achieved 3.47 average connections per qubit.
• Random-circuit sampling benchmark completed in under 5 minutes vs. estimated 10^24 years classically—vastly exceeds universe's age.
• Built in Google's Santa Barbara fab; emphasizes integrated system engineering with all components working cohesively.