Quantum error correction below the surface code threshold

Quantum error correction (QEC) is critical for achieving useful quantum computers, since it allows us to combine many noisy physical qubits into one high-quality logical qubit with exponentially decreasing logical error rate. In this talk, we will discuss Google’s latest error correction results [1] where we achieved below threshold surface code performance with logical qubits at distances=(3, 5, 7). In a logical qubit memory demonstration, we show that each increase in distance reduces errors by a factor of 2.14. Additionally, we report the ability to decode these QEC experiments in real-time for up to 1 million rounds. Finally, we present a 10,000x reduction in the rare correlated errors by measuring the repetition code in the very low error regime. Ultimately, our results show device performance that, if scaled, could realize the operational requirements of large scale fault-tolerant quantum algorithms.

[1] Quantum error correction below the surface code threshold, Google Quantum AI, arXiv:2408.13687 (2024)