How the algorithm works and its applications
The Quantum Echoes algorithm sends precisely crafted signals through Willow’s quantum system, perturbing a single qubit, then reversing the signal’s evolution. “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 explained.

“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,” the statement added.