Demonstration of qubit operations below a rigorous fault tolerance threshold with gate set tomography

• Published in: Nature communications Vol. 8; no. 1; pp. 1 - 13
• Main Authors: Blume-Kohout, Robin, Gamble, John King, Nielsen, Erik, Rudinger, Kenneth, Mizrahi, Jonathan, Fortier, Kevin, Maunz, Peter
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.02.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/36/1121; 639/766/483/2802; 639/766/483/481; Algorithms; atomic and molecular interactions with photons; Error correction & detection; Fault tolerance; Humanities and Social Sciences; Laboratories; MATHEMATICS AND COMPUTING; multidisciplinary; Protocol; quantum information; qubits; Science; Tomography; New Mexico; United States > US
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14485

Quantum information processors promise fast algorithms for problems inaccessible to classical computers. But since qubits are noisy and error-prone, they will depend on fault-tolerant quantum error correction (FTQEC) to compute reliably. Quantum error correction can protect against general noise if—and only if—the error in each physical qubit operation is smaller than a certain threshold. The threshold for general errors is quantified by their diamond norm. Until now, qubits have been assessed primarily by randomized benchmarking, which reports a different error rate that is not sensitive to all errors, and cannot be compared directly to diamond norm thresholds. Here we use gate set tomography to completely characterize operations on a trapped-Yb + -ion qubit and demonstrate with greater than 95% confidence that they satisfy a rigorous threshold for FTQEC (diamond norm ≤6.7 × 10 −4 ). Quantum computation will depend on fault-tolerant error correction, which requires the chance for errors to occur to be below a certain threshold. Here the authors use gate set tomography as a means to rigorously characterize error rates of single-qubit operations of a qubit encoded in a trapped ion.