Researchers at Google Quantum AI announced the achievement of “verifiable quantum advantage” using the new Quantum Echoes algorithm, executed on the 105-qubit Willow processor.
This marks the first instance where a quantum device has solved a computational problem that is virtually impossible to simulate on classical supercomputers. Moreover, the result can be verified by another quantum system.
The new algorithm measures Out-of-Time-Order Correlators (OTOC), which describe how information “smears” and becomes chaotic within a quantum system.
“The Quantum Echoes algorithm represents a new class of problems as it models a physical experiment. This means it tests not only the complexity but also the accuracy of the final computations,” the researchers explained.
The technology employs “forward” and “reverse” evolution variables of the quantum system. It is then “rolled forward,” slightly perturbing one qubit, and “rolled back,” observing the emergence of an “echo.”
The interference-enhanced signal allows the study of fundamental properties of matter such as magnetic phases or spin network dynamics.
Unlike previous demonstrations where the result was a random bit sample, OTOC is a quantum observable, like electric current or magnetisation, with a constant value.
According to the Google team, this step paves the way for the first practical application of quantum computing. Potentially, the algorithm could be used to study molecular structures.
“As we move closer to creating a fully functional quantum computer with error correction, we anticipate many more such useful real-world applications. Currently, we are focused on achieving the third stage in our quantum hardware roadmap — creating a long-lived logical qubit,” the company concluded.
Earlier in September, the startup Oxford Quantum Circuits installed the first quantum computer in New York at a data centre in Manhattan.