Meet ‘Willow’: The quantum hardware engine behind Google’s latest breakthrough

Yesterday, Google’s Quantum AI team announced a historic achievement: the first-ever demonstration of verifiable quantum advantage. This milestone, a critical step towards practical quantum computing, wasn’t just an algorithmic breakthrough; it was made possible by decades of investment and innovation in the underlying quantum hardware. The star of that hardware story is Google’s state-of-the-art quantum chip, Willow.

Built on Nobel Prize-winning foundations

Willow is built from superconducting quantum circuits , a field of research rooted in the 1985 discovery of the macroscopic quantum effect. This foundational work earned John Clarke, Michel Devoret (now Chief Scientist at Google Quantum AI), and John Martinis the 2025 Nobel Prize in Physics. These superconducting qubits function like macroscopic “artificial atoms” and have become a leading platform for building fault-tolerant quantum computers due to their balance of performance and scalability.

Meeting the demands of ‘Quantum Echoes’

Achieving verifiable quantum advantage required running the complex Quantum Echoes algorithm. This algorithm places strong demands on the hardware, requiring a large set of quantum gates and a high volume of quantum measurements to extract the useful signal from background noise.

Google’s Willow chip, benefiting from continuous improvements, delivered best-in-class performance at the necessary scale. Key performance metrics across its 105-qubit array include:

• Single-qubit gate fidelities of 99.97%
• Entangling gate fidelities of 99.88%
• Readout fidelities of 99.5%
• All operating at unmatched speeds of tens to hundreds of nanoseconds

This high precision enabled the complex quantum interferences and entanglement needed for the Quantum Echoes algorithm, pushing the results beyond the capabilities of classical computers.

Unprecedented scale and speed

Beyond precision, the sheer speed of the Willow system was instrumental. It can perform millions of Quantum Echoes measurements in just tens of seconds. This speed allowed the team to perform a staggering one trillion measurements over the course of the project – a significant portion of all measurements ever performed on all quantum computers combined. Google describes this work as “one of the most complex experiments in the history of quantum computing”.

This demonstration of verifiable quantum advantage marks another crucial step on Google’s Quantum AI Roadmap toward building a fault-tolerant quantum computer. Having already achieved milestones like beyond-classical computation (2019) and an error correction prototype (2023), the team is now focused on reaching Milestone 3: a long-lived logical qubit. While acknowledging the significant challenges ahead, Google remains committed to pushing the boundaries of quantum hardware.