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Josephson-junction qubits with controlled couplings

Nature volume 398, pages 305–307 (1999)Cite this article

Abstract

Quantum computers, if available, could perform certain tasks much more efficiently than classical computers by exploiting different physical principles1,2,3. A quantum computer would be comprised of coupled, two-state quantum systems or qubits, whose coherent time evolution must be controlled in a computation. Experimentally, trapped ions4,5, nuclear magnetic resonance6,7,8 in molecules, and quantum optical systems9 have been investigated for embodying quantum computation. But solid-state implementations10,11,12,13,14 would be more practical, particularly nanometre-scale electronic devices: these could be easily embedded in electronic circuitry and scaled up to provide the large numbers of qubits required for useful computations. Here we present a proposal for solid-state qubits that utilizes controllable, low-capacitance Josephson junctions. The design exploits coherent tunnelling of Cooper pairs in the superconducting state, while employing the control mechanisms of single-charge devices: single- and two-bit operations can be controlled by gate voltages. The advantages of using tunable Josephson couplings include the simplification of the operation and the reduction of errors associated with permanent couplings.

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Figure 1: Josephson junction qubits.
Figure 2: Spectrum of a superconducting electron box.
Figure 3: Design of a quantum computer.

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Acknowledgements

We thank T. Beth, M. Devoret, D. P. DiVincenzo, E. Knill, K. K. Likharev and J.E.Mooij for discussions.

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Authors and Affiliations

  1. Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128, Karlsruhe, Germany

    Yuriy Makhlin & Gerd Scöhn

  2. Landau Institute for Theoretical Physics , Kosygin Street 2, 117940, Moscow, Russia

    Yuriy Makhlin

  3. Department of Physics, University of Illinois at Urbana-Champaign, Urbana, 61801, Illinois, USA

    Alexander Shnirman

Authors
  1. Yuriy Makhlin
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Correspondence to Yuriy Makhlin.

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Makhlin, Y., Scöhn, G. & Shnirman, A. Josephson-junction qubits with controlled couplings. Nature 398, 305–307 (1999). https://doi.org/10.1038/18613

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