Quantum error mitigation for fault-tolerant quantum computing

8 Oct 2020  ·  Yasunari Suzuki, Suguru Endo, Keisuke Fujii, Yuuki Tokunaga ·

Fault-tolerant quantum computing (FTQC) is a form of universal quantum computing that suppresses physical errors via quantum error correction (QEC). On the other hand, it is expected that the available code distance and the $T$-gate count will be restricted in the early years of FTQC... Meanwhile, quantum error mitigation (QEM) was recently introduced for suppressing errors in noisy intermediate-scale quantum (NISQ) devices; it improves the computation accuracy of near-term quantum algorithms with its overhead being a greater number of samples. In this work, we integrate QEC and QEM into an efficient FTQC architecture that effectively increases the code distance and $T$-gate count. Our scheme will dramatically alleviate the required qubit count by tens of percent at the cost of a constant multiplicative sampling overhead within $10^2$ in a wide range of regimes from the post-NISQ era to early FTQC regime, which necessitates the order of from $10^4$ to $10^{10}$ logical operations. While it has been widely believed that there do not exist useful applications in post-NISQ regimes due to a chasm between the NISQ and FTQC regimes such as overheads for encoding and $T$-gate distillations, our scheme can continuously bridge the two distinct regimes. read more

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Quantum Physics