State preservation by repetitive error detection in a superconducting quantum circuit

By J. Kelly, R. Barends, Austin G. Fowler, A. Megrant, Evan Jeffrey, T. White, D. Sank, J. Mutus, B. Campbell, Yu Chen and 12 more. Nature, 2014

878 citations recorded by the source corpus.

Quantum computing becomes viable when a quantum state can be protected from environment-induced error. If quantum bits (qubits) are sufficiently reliable, errors are sparse and quantum error correction (QEC) is capable of identifying and correcting them. Adding more qubits improves the preservation of states by guaranteeing that increasingly larger clusters of errors will not cause logical failure—a key requirement for large-scale systems. Using QEC to extend the qubit lifetime remains one of the outstanding experimental challenges in quantum computing. Here we report the protection of classical states from environmental bit-flip errors and demonstrate the suppression of these errors with increasing system size. We use a linear array of nine qubits, which is a natural step towards the two-dimensional surface code QEC scheme, and track errors as they occur by repeatedly performing projective quantum non-demolition parity measurements. Relative to a single physical qubit, we reduce the failure rate in retrieving an input state by a factor of 2.7 when using five of our nine qubits and by a factor of 8.5 when using all nine qubits after eight cycles. Additionally, we tomographically verify preservation of the non-classical Greenberger–Horne–Zeilinger state. The successful suppression of environment-induced errors will motivate further research into the many challenges associated with building a large-scale superconducting quantum computer.

Subfields: Artificial Intelligence, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/2b0b0f969fdbd968e0dfa7130fbe916f6afc9afd

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Citations in the corpus

Suppressing quantum errors by scaling a surface code logical qubit (2022, neutral): “To avoid this issue, we decode an even subset of experimental trials by computing p ij on the odd subset, and vice versa, similar to [61], and then average the two.”
Frodo: Take off the Ring! Practical, Quantum-Secure Key Exchange from LWE (2016, background): “[26, 39]) have triggered widespread interest in developing practical postquantum cryptographic schemes [48].”
Entanglement certification from theory to experiment (2018, methodology): “[194] J.”
Low-Depth Quantum Simulation of Materials (2017, background): “[31] J Kelly, R Barends, A G Fowler, A Megrant, E Jeffrey, T C White, D Sank, J Y Mutus, B Campbell, Yu Chen, Z Chen, B Chiaro, A Dunsworth, I.”
Quantum error mitigation (2022, background): “…correcting errors is required for scalability (Shor, 1996), quantum error detection of artificially-added symmetries has been widely recognised as an important mile-stone towards this end goal (C´orcoles et al. , 2015; Gottes-man, 2016; Kelly et al. , 2015; Linke et al. , 2017; Nigg et al. , 2014).”