Google Researchers Make Quantum Computing Breakthrough With Willow Chip

The research team working towards quantum computing at Google Quantum AI announced a major step forward this week in the journal Nature. Thanks to Willow, a quantum chip that features a 105-qubit array and is significantly better at suppressing errors than previous hardware, the team can run a verifiable quantum advantage.

According to the researchers, the computer running the Willow quantum chip is 13,000 times faster than a classical supercomputer. The idea behind a quantum advantage is that it marks the point at which a quantum computer is capable of solving a real-world problem that classical computers can't complete in a reasonable timeframe (or at all). In this case, the team noted that it can compute a molecule, though not necessarily a complex one.
In the team's announcement, Google Quantum AI founder and lead Hartmut Neven and director of quantum pathfinding Vadim Smelyanskiy wrote that they "…demonstrated the first-ever verifiable quantum advantage running the out-of-order time correlator (OTOC) algorithm, which we call Quantum Echoes."

"Our new technique works like a highly advanced echo," the announcement continues. "We send a carefully crafted signal into our quantum system (qubits on Willow chip), perturb one qubit, then precisely reverse the signal's evolution to listen for the 'echo' that comes back."

Google's research team used two molecules (with 15 and 28 atoms). Nuclear magnetic resonance (NMR), which the researchers call "the spectroscopic cousin of MRI," confirmed their findings.

"The results on our quantum computer matched those of traditional NMR, and revealed information not usually available from NMR, which is crucial validation of our approach," the researchers wrote.

Scoring a quantum advantage is a necessary step in a roadmap loaded with hurdles. In fact, their achievement doesn't quite push the team to Milestone 3, which is the creation of a long-lived logical qubit. The researchers achieved their first milestone with the Sycamore processor. They then hit Milestone 2 in 2023 with a logical qubit prototype.

Nature also published an article in which some researchers voiced concerns about whether the quantum advantage claim has been proven. Some wonder whether there might be a classical algorithm that could compete with the performance of the quantum hardware, or, rather, whether the proof that there isn't one hasn't been established yet.