Summary
Harvard’s neutral-atom team has unveiled a working fault-tolerant architecture on a 448-atom processor that stitches together the core ingredients long promised in theory. They show below-threshold surface-code style error correction, transversal logical gates, teleportation-based universality, mid-circuit qubit reuse, and constant-entropy deep circuits. The result is a real device behaving like the textbooks say a fault-tolerant quantum computer should.
The key milestone is operation below the error-correction threshold. In this regime, adding qubits to the code lowers the logical error rate, shifting the platform out of the NISQ era and into scalable territory where error correction compounds progress. Framed within the Path to CRQC and Predicting Q-Day methodology, below-threshold performance now sits alongside logical qubit capacity, logical operations budget, connectivity, decoding throughput, and stability as a primary capability axis.
For cyber leaders, this is not a cryptographic break today, but it is a concrete step that strengthens timelines toward cryptographically relevant quantum computing. Track sustained below-threshold behavior, growth in logical qubits, and end-to-end decoding performance. These are the indicators that will sharpen Q-Day forecasts and guide the urgency of PQC migration plans.
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See the original article at: https://postquantum.com/quantum-computing/qec-below-threshold-experiments/