Tuckett David K, Bartlett Stephen D, Flammia Steven T, Brown Benjamin J
Centre for Engineered Quantum Systems, School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia.
Phys Rev Lett. 2020 Apr 3;124(13):130501. doi: 10.1103/PhysRevLett.124.130501.
Noise in quantum computing is countered with quantum error correction. Achieving optimal performance will require tailoring codes and decoding algorithms to account for features of realistic noise, such as the common situation where the noise is biased towards dephasing. Here we introduce an efficient high-threshold decoder for a noise-tailored surface code based on minimum-weight perfect matching. The decoder exploits the symmetries of its syndrome under the action of biased noise and generalizes to the fault-tolerant regime where measurements are unreliable. Using this decoder, we obtain fault-tolerant thresholds in excess of 6% for a phenomenological noise model in the limit where dephasing dominates. These gains persist even for modest noise biases: we find a threshold of ∼5% in an experimentally relevant regime where dephasing errors occur at a rate 100 times greater than bit-flip errors.
量子计算中的噪声可通过量子纠错来对抗。要实现最优性能，需要定制编码和解码算法，以考虑现实噪声的特征，比如噪声偏向退相的常见情况。在此，我们基于最小权重完美匹配，为噪声定制表面码引入一种高效的高阈值解码器。该解码器利用有偏噪声作用下其校验子的对称性，并推广到测量不可靠的容错情形。使用此解码器，对于退相占主导的极限情形下的唯象噪声模型，我们获得了超过6%的容错阈值。即使对于适度的噪声偏差，这些增益依然存在：在一个实验相关的情形中，我们发现阈值约为5%，其中退相错误的发生率比比特翻转错误大100倍。
