McClean Jarrod R, Jiang Zhang, Rubin Nicholas C, Babbush Ryan, Neven Hartmut
Google Inc., 340 Main Street, Venice, CA, 90291, USA.
Nat Commun. 2020 Jan 31;11(1):636. doi: 10.1038/s41467-020-14341-w.
With rapid developments in quantum hardware comes a push towards the first practical applications. While fully fault-tolerant quantum computers are not yet realized, there may exist intermediate forms of error correction that enable practical applications. In this work, we consider the idea of post-processing error decoders using existing quantum codes, which mitigate errors on logical qubits using post-processing without explicit syndrome measurements or additional qubits beyond the encoding overhead. This greatly simplifies the experimental exploration of quantum codes on real, near-term devices, removing the need for locality of syndromes or fast feed-forward. We develop the theory of the method and demonstrate it on an example with the perfect [[5, 1, 3]] code, which exhibits a pseudo-threshold of p ≈ 0.50 under a single qubit depolarizing channel applied to all qubits. We also provide a demonstration of improved performance on an unencoded hydrogen molecule.
随着量子硬件的快速发展，人们开始推动其首次实际应用。虽然完全容错的量子计算机尚未实现，但可能存在中间形式的纠错方法，可实现实际应用。在这项工作中，我们考虑使用现有量子码对错误解码器进行后处理的想法，这种方法通过后处理减轻逻辑量子比特上的错误，而无需进行明确的综合征测量或超出编码开销的额外量子比特。这极大地简化了在真实的近期设备上对量子码的实验探索，消除了对综合征局部性或快速前馈的需求。我们发展了该方法的理论，并在完美的[[5, 1, 3]]码示例中进行了演示，在对所有量子比特应用单比特去极化信道的情况下，该码表现出约为0.50的伪阈值。我们还展示了在未编码氢分子上性能的提升。
