Quantum News Nexus

Google Quantum AI announced some major progress in its quantum computing efforts, unveiling Quantum Echoes, which the company described as a “breakthrough” quantum algorithm running on its Willow chip that showcases “verifiable quantum advantage,” and will lead to the important real-world scientific applications through its ability to compute the structure of molecules.

The news comes almost a year after Google Quantum AI unveiled Willow, a 105-qubit quantum processors with advanced error correction capabilities.

Explained at length in a Google Keyword blog post and a Nature paper, Quantum Echoes is an “out of order time correlator,” which sounds about as sci-fi as quantum computing gets, though the “how” of Quantum Echoes and its significance are both easier to grasp. 

As the blog post puts it, “Our new technique works like a highly advanced echo. We send a carefully crafted signal into our quantum system (qubits on Willow chip) and then precisely reverse its evolution to listen for the ‘echo’ that comes back. This quantum echo is special because it gets amplified by constructive interference — a phenomenon where quantum waves add up to become stronger. This makes our measurement incredibly sensitive.”

As for the claim of “verifiable quantum advantage,” Hartmut Neven, who founded and leads the Google Quantum AI lab, said during a media briefing, “The algorithm runs on our Willow chip 13,000 times faster than the best classical algorithm would on the top classical supercomputer. So, think hours [on Willow] versus years for the classical machine.”

Neven further explained that Quantum Echoes “produces verifiable predictions. These predictions can be verified in two ways. You either can repeat the computation on a different quantum computer, assuming it’s powerful enough, and then you should get the same result, so you can check it that way. Or you can talk to nature directly and do an experiment which, of course, involves quantum effects, and then you can compare it to other predictions you make about a real world system to show that it is really accurate.”

As for real-world application, the measurement sensitivity enabled by Quantum Echoes enables the development of a “molecular ruler” for analyzing the structure of molecules, Neven said, adding that “learning the structure of molecules opens the door to real-world applications.”

The blog post further explained that in a proof-of-principle experiment (the subject of a companion paper to be published shortly) in partnership with the University of California-Berkeley, Google Quantum AI ran the Quantum Echoes algorithm on Willow “to study two molecules, one with 15 atoms and another with 28 atoms, to verify this approach. The results on our quantum computer matched those of traditional Nuclear Magnetic Resonance [NMR, the basis for MRIs and a broader range of chemical analysis], and revealed information not usually available from NMR [data], which is a crucial validation of our approach.”

All of that suggests that something like a “quantum-scope” could be developed that would be capable of measuring previously unobservable natural phenomena. That kind of tool would have major implications for drug discovery, often mentioned as the No. 1 application in which quantum computing can make a difference that cements its commercial and practical relevance. Such a tool also could prove immensely useful in material science applications, such as the development of more powerful and efficient batteries. Quantum sensing also was identified as another field for real-world application.

We should not expect GQAI to take the lead in commercializing these applications. It’s a lab, and unlike an IonQ or D-Wave or another quantum computing company with commercial aspirations and a need to satisfy investors, it does not have any real sense of urgency to promote its own revenue-generating applications. Maybe Google as a company will go down that path in the future, but for now it is letting its Google Quantum AI research outfit continue to pursue its six-milestone technical roadmap. Next up on that roadmap is the “building of a long-lived logical qubit.” GQAI has not provided an update for how soon it will reach that milestone, but I’m sure we’ll know when it gets there.

Image source: Google Quantum AI

Quantum News Nexus is a new site from freelance writer and editor Dan O’Shea that covers quantum computing, quantum sensing, quantum networking, quantum-safe security, and more. You can find him on X @QuantumNewsGuy and doshea14@gmail.com.