title: Implementing a strand of a scalable fault-tolerant quantum computing fabric.
abstract: With favourable error thresholds and requiring only nearest-neighbour interactions on a lattice, the surface code is an error-correcting code that has garnered considerable attention. At the heart of this code is the ability to perform a low-weight parity measurement of local code qubits. Here we demonstrate high-fidelity parity detection of two code qubits via measurement of a third syndrome qubit. With high-fidelity gates, we generate entanglement distributed across three superconducting qubits in a lattice where each code qubit is coupled to two bus resonators. Via high-fidelity measurement of the syndrome qubit, we deterministically entangle the code qubits in either an even or odd parity Bell state, conditioned on the syndrome qubit state. Finally, to fully characterize this parity readout, we develop a measurement tomography protocol. The lattice presented naturally extends to larger networks of qubits, outlining a path towards fault-tolerant quantum computing.
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Jerry M
authors: JM
authors: Chow
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Jay M
authors: JM
authors: Gambetta
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Easwar
authors: E
authors: Magesan
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: David W
authors: DW
authors: Abraham
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Andrew W
authors: AW
authors: Cross
authors: Raytheon BBN Technologies, Cambridge, Massachusetts 02138, USA.
authors: B R
authors: BR
authors: Johnson
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Nicholas A
authors: NA
authors: Masluk
authors: Raytheon BBN Technologies, Cambridge, Massachusetts 02138, USA.
authors: Colm A
authors: CA
authors: Ryan
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: John A
authors: JA
authors: Smolin
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Srikanth J
authors: SJ
authors: Srinivasan
authors: IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: M
authors: M
authors: Steffen