Title：Flag the faults for reliable quantum computing

Speaker：Rui Chao (USC)

Date：June 11th Thu, 10:00am

Meeting Link：https://voovmeeting.com/s/tbvTjxOOLSAW; Meeting ID: 678 552 012？

Abstract：While there have been experiments of quantum error correction, testing fault-tolerance remains a major challenge. A main difficulty is the substantial overhead; many physical qubits are needed for each logical qubit. This means that on small- and medium-scale systems in the near future, it will be difficult to test fault-tolerance theory, and to explore the efficacy of different fault-tolerance schemes. We propose a qubit-efficient paradigm for fault tolerance, which we term the ''flag method.'' Specifically, we add ''flags'' to catch the faults that can lead to correlated data errors. Provided the flag gadgets are carefully designed, potential correlated errors can be diagnosed by their syndromes. For various small codes, we provide flag schemes that are promising for testing fault tolerance on near-term devices. For example, in a 19-qubit system, we can protect and compute universally on 7 encoded qubits fault tolerantly. We also construct schemes for asymptotically large codes, showing that the flag paradigm is of general theoretical interest as well as practical importance.

Rui Chao and BenW. Reichardt Phys. Rev. Lett. 121, 050502 (2018)

Rui Chao and BenW. Reichardt, npj Quantum Information, 4, 42 (2018)

Rui Chao and BenW. Reichardt, arXiv:1912.09549 (2019)