Demonstration of a quantum error detection code using a square lattice of four superconducting qubits

• Published in: Nature communications Vol. 6; no. 1; p. 6979
• Main Authors: Córcoles, A.D., Magesan, Easwar, Srinivasan, Srikanth J., Cross, Andrew W., Steffen, M., Gambetta, Jay M., Chow, Jerry M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.04.2015; Nature Publishing Group; Nature Pub. Group
• Subjects: 639/766/119/1003; 639/766/25; 639/766/483/2802; Coding; Demolition; Dimensional tolerances; Error correcting codes; Error correction; Error correction & detection; Error detection codes; Fault tolerance; Humanities and Social Sciences; Lattices; multidisciplinary; Quantum computing; Quantum theory; Qubits (quantum computing); Science; Science (multidisciplinary); Superconductivity
• DOI: 10.1038/ncomms7979
• ISSN: 2041-1723

The ability to detect and deal with errors when manipulating quantum systems is a fundamental requirement for fault-tolerant quantum computing. Unlike classical bits that are subject to only digital bit-flip errors, quantum bits are susceptible to a much larger spectrum of errors, for which any complete quantum error-correcting code must account. Whilst classical bit-flip detection can be realized via a linear array of qubits, a general fault-tolerant quantum error-correcting code requires extending into a higher-dimensional lattice. Here we present a quantum error detection protocol on a two-by-two planar lattice of superconducting qubits. The protocol detects an arbitrary quantum error on an encoded two-qubit entangled state via quantum non-demolition parity measurements on another pair of error syndrome qubits. This result represents a building block towards larger lattices amenable to fault-tolerant quantum error correction architectures such as the surface code. The physical realization of a quantum computer requires built-in error-correcting codes that compensate the disruption of quantum information arising from noise. Here, the authors demonstrate a quantum error detection scheme for arbitrary single-qubit errors on a four superconducting qubit lattice.