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Quantum interference device for controlled two-qubit operations

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  • Niels Jakob Søe Loft
  • ,
  • Morten Kjaergaard, Massachusetts Institute of Technology
  • ,
  • Lasse Bjørn Kristensen
  • ,
  • Christian Kraglund Andersen, ETH Zürich
  • ,
  • Thorvald W. Larsen, University of Copenhagen
  • ,
  • Simon Gustavsson, Massachusetts Institute of Technology
  • ,
  • William D. Oliver, Massachusetts Institute of Technology
  • ,
  • Nikolaj T. Zinner

Universal quantum computing relies on high-fidelity entangling operations. Here, we demonstrate that four coupled qubits can operate as a quantum gate, where two qubits control the operation on two target qubits (a four-qubit gate). This configuration can implement four different controlled two-qubit gates: two different entangling swap and phase operations, a phase operation distinguishing states of different parity, and the identity operation (idle quantum gate), where the choice of gate is set by the state of the control qubits. The device exploits quantum interference to control the operation on the target qubits by coupling them to each other via the control qubits. By connecting several four-qubit devices in a two-dimensional lattice, one can achieve a highly connected quantum computer. We consider an implementation of the four-qubit gate with superconducting qubits, using capacitively coupled qubits arranged in a diamond-shaped architecture.

Original languageEnglish
Article number47
Journalnpj Quantum Information
Publication statusPublished - May 2020

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