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Entanglement in a Quantum Annealing Processor

  • T. Lanting
  • A. J. Przybysz
  • A. Yu. Smirnov
  • F. M. Spedalieri
  • M. H. Amin
  • A. J. Berkley
  • R. Harris
  • F. Altomare
  • S. Boixo
  • P. Bunyk
  • N. Dickson
  • C. Enderud
  • J. P. Hilton
  • E. Hoskinson
  • M. W. Johnson
  • E. Ladizinsky
  • N. Ladizinsky
  • R. Neufeld
  • T. Oh
  • I. Perminov
  • C. Rich
  • M. C. Thom
  • E. Tolkacheva
  • S. Uchaikin
  • A. B. Wilson
  • G. Rose
Physical Review X, vol. 4 (2014), pp. 021041


Entanglement lies at the core of quantum algorithms designed to solve problems that are intractable by classical approaches. One such algorithm, quantum annealing (QA), provides a promising path to a practical quantum processor. We have built a series of architecturally scalable QA processors consisting of networks of manufactured interacting spins (qubits). Here, we use qubit tunneling spectroscopy to measure the energy eigenspectrum of two- and eight-qubit systems within one such processor, demonstrating quantum coherence in these systems. We present experimental evidence that, during a critical portion of QA, the qubits become entangled and entanglement persists even as these systems reach equilibrium with a thermal environment. Our results provide an encouraging sign that QA is a viable technology for large-scale quantum computing.

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