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Dynamical Casimir effect in quantum-information processing

Giuliano Benenti, Antonio D'Arrigo, Stefano Siccardi, and Giuliano Strini
Phys. Rev. A 90, 052313 – Published 11 November 2014
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  • INTRODUCTION
  • PHYSICAL MODEL
  • BASIC QUANTUM PROTOCOL
  • RESULTS
  • DISCUSSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    We demonstrate, in the regime of ultrastrong matter-field coupling, the strong connection between the dynamical Casimir effect (DCE) and the performance of quantum-information protocols. Our results are illustrated by means of a realistic quantum communication channel and show that the DCE is a fundamental limit for quantum computation and communication and that novel schemes are required to implement ultrafast and reliable quantum gates. Strategies to partially counteract the DCE are also discussed.

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    • Received 28 July 2014
    • Revised 9 September 2014

    DOI:https://doi.org/10.1103/PhysRevA.90.052313

    ©2014 American Physical Society

    Authors & Affiliations

    Giuliano Benenti1,2, Antonio D'Arrigo3,4, Stefano Siccardi5, and Giuliano Strini5

    • 1CNISM and Center for Nonlinear and Complex Systems, Università degli Studi dell'Insubria, via Valleggio 11, 22100, Como, Italy
    • 2Istituto Nazionale di Fisica Nucleare, Sezione di Milano, via Celoria 16, 20133, Milano, Italy
    • 3CNR-IMM UOS Università (MATIS), Consiglio Nazionale delle Ricerche, Via Santa Sofia 64, 95123, Catania, Italy
    • 4Dipartimento di Fisica e Astronomia, Università degli Studi Catania, Via Santa Sofia 64, 95123, Catania, Italy
    • 5Department of Physics, University of Milan, via Celoria 16, 20133, Milano, Italy

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    Issue

    Vol. 90, Iss. 5 — November 2014

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    Images

    • Figure 1
      Figure 1

      Schematic drawing of the quantum protocol discussed in the text. The coupling between the qubit Qi and the cavity C is modulated by the function fi(t). By initially preparing Q1 in the state ρ, Q2 is found in the state ρ′ at the end of the protocol.

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    • Figure 2
      Figure 2

      Coherent information Ic(ρu) (full curve, left axis), single-shot quantum capacity Q1 (gray circles, left axis), and mean photon number 〈n〉 (right axis) as a function of the qubit-field coupling strength g. The mean photon number is shown for the pure DCE (dotted curve) and at the end of the quantum communication protocol (dashed curve). The time intervals of the protocol are T1=T2=π/2g and Tc=0. As we point out in the text, with a very good approximation Q1≃Ic(ρu). Here and in the following figures the coherent information in computed for the maximally mixed input state ρu.

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    • Figure 3
      Figure 3

      Coherent information Ic(ρu) (main figure) and transmission rate R (inset) as a function of the coupling strength g, for the transmission window discussed in the text, with ξ=0 (full curve), ξ=0.2 (dashed curve), and ξ=0.5 (dotted curve). As in Fig. 2, T1=T2=π/2g and Tc=0.

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    • Figure 4
      Figure 4

      Coherent information Ic(ρu) (main figure) and transmission rate R (inset) as a function of the coupling strength g, for the standard protocol (full curve) and after optimization over the times T1,T2, and Tc.

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    • Figure 5
      Figure 5

      Nonzero parameters of the Fano representation of the quantum channel E, as a function of the coupling strength g, for T1=T2=π/2g, Tc=0, and sudden switch on and off of the couplings.

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