For the first time, scientists have shown that a quantum computer can execute a verifiable algorithm faster than any classical supercomputer. The breakthrough achieved by Google's Willow quantum processor represents a major step towards practical, real-world applications of quantum computing in fields ranging from drug discovery to materials science.
The team's innovation focus is on a new algorithm called Quantum Echoescapable of examining the hidden structure of nature with unprecedented precision. Much like a sonar sends a signal into the ocean and listens to the echoes to discover what lies beneath, Quantum Echoes sends a quantum signal into a system of particles, distorts it, and then reverses time to capture the “echo” that reveals complex quantum behavior.
This echo is not a mere reflection. Through a phenomenon called constructive interference, quantum waves amplify each other, producing ultrasensitive measurements that reveal the structure of molecules and even shed light on fundamental systems such as magnets and black holes.
Running on the Willow chip, the Quantum Echoes algorithm performed calculations 13,000 times faster than would be possible on Frontier, the most powerful classical supercomputer in the world. In one test, the system simulated the geometry of molecules containing up to 28 atoms, matching or even exceeding the results of traditional nuclear magnetic resonance (NMR) methods used in chemistry.
This marks the first verifiable quantum advantage: a repeatable, beyond-classical result that can be confirmed using another quantum computer of similar quality – a key step towards scalable and reliable quantum computing.
Behind the breakthrough lies deep theoretical work on out-of-time order correlators (OTOCs) – exotic mathematical tools that reveal how information propagates in complex quantum systems. When researchers used repeated time-reversal protocols (essentially rewinding and replaying quantum dynamics), they found that second-order OTOCs (OTOC²) remained sensitive to underlying physics much longer than expected.
These higher-order quantum echoes have not only revealed new insights into quantum interference, but have also reached a level of complexity that classical computers can no longer effectively simulate. For example, it would take a supercomputer over three years to simulate one of the 65-qubit experiments, compared to just a few hours for a quantum processor.
Beyond theory, the study demonstrated a real-world application called Hamiltonian learning, a method for discovering the physical laws that govern a system by comparing quantum-measured data with quantum-simulated models. In one proof-of-principle experiment, the team managed to identify an unknown parameter in a simulated molecular system, paving the way for future applications in materials design and chemical analysis.
This achievement meets two of the three conditions that scientists call practical quantum benefits:
- The result can be accurately measured (with a high signal-to-noise ratio).
- This cannot be simulated classically using usable resources.
The third, extracting practically useful insights, is already on the horizon and has potential applications in solid-state physics, biochemistry and energy research.
As quantum hardware improves, the consequences are enormous. The Quantum Echoes algorithm shows that we are moving beyond laboratory curiosities towards quantum computers, which could address significant scientific challenges by revealing the invisible patterns that shape our universe.
