What it is
Amazon built a logical qubit by concatenating bosonic cat qubits, which passively suppress bit-flip errors, with an outer distance-5 repetition code that corrects phase flips. The repetition code operated below threshold, and the logical error per cycle was 1.65% for the distance-5 code and 1.75% for distance-3, comparable despite the larger code's extra fault locations because the noise bias is preserved.
Why it matters
Standard error correction needs thousands of physical qubits per logical one. Pushing part of the job into the hardware, via bias-preserving cat qubits, is a credible route to fault tolerance with far less overhead.
Underlined numbers link to their source. Every metric and quoted figure is listed under Sources and data below.
Filed underquantum error correction, bosonic qubits, cat qubits, fault tolerance, superconducting