RESCUED: Robust Quantum Error Correction with Surface Code in Noisy Channels Using Ensemble Decoder

The necessity for quantum error correction arises from the need to safeguard quantum information from errors induced by decoherence and other noise forms. However, the optimal decoding of quantum error-correcting codes is a computationally challenging task. In our research, we introduce an ensemble decoder that amalgamates the advantages of various decoders to attain lower logical error rates and the capability to decode multiple errors. We employed statistical methodologies to allocate a specific error syndrome to the decoder with the highest likelihood of accurate decoding. We applied diverse variants of the Noise model to simulate the impact of noise on transmitted quantum states accurately. The efficacy of the ensemble decoder was assessed in both Symmetric and Asymmetric Noise Models. In the Symmetric Noise Model, bit-flip and phase-flip errors are presumed to have equal probabilities, while in the Asymmetric Noise Model, these probabilities can vary. The comparison aimed to evaluate the ensemble decoder's proficiency in rectifying these error types compared to traditional decoding techniques. Our results indicate that the ensemble decoder surpasses conventional decoders in the Symmetric Noise model, particularly for higher code distances. It is also apparent that augmenting the lattice size diminishes the logical error rate and that threshold and pseudo-threshold values escalate with incremental changes in noise asymmetry. The study's findings underscore the substantial potential of the ensemble decoder in quantum error correction and communication realms.