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Control relaxation via dephasing: A quantum-state-diffusion study

Jun Jing, Ting Yu, Chi-Hang Lam, J. Q. You, and Lian-Ao Wu
Phys. Rev. A 97, 012104 – Published 8 January 2018
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  • INTRODUCTION
  • MODELS AND METHOD
  • RESULTS OF FIDELITY CONTROL
  • DISCUSSION
  • CONCLUSION
  • ACKNOWLEDGMENTS
    • References

    Abstract

    Dynamical decoupling as a quantum control strategy aims at suppressing quantum decoherence adopting the popular philosophy that the disorder in the unitary evolution of the open quantum system caused by environmental noises should be neutralized by a sequence of ordered or well-designed external operations acting on the system. This work studies the solution of quantum-state-diffusion equations by mixing two channels of environmental noises, i.e., relaxation (dissipation) and dephasing. It is interesting to find in two-level and three-level atomic systems that a non-Markovian relaxation or dissipation process can be suppressed by a Markovian dephasing noise. The discovery results in an anomalous control strategy by coordinating relaxation and dephasing processes. Our approach opens an avenue of noise control strategy with no artificial manipulation over the open quantum systems.

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    • Received 21 September 2017

    DOI:https://doi.org/10.1103/PhysRevA.97.012104

    ©2018 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Open quantum systems & decoherenceQuantum fluctuations & noise
    Quantum Information, Science & Technology

    Authors & Affiliations

    Jun Jing1,2, Ting Yu3,4, Chi-Hang Lam5, J. Q. You3, and Lian-Ao Wu2,*

    • 1Department of Physics, Zhejiang University, Hangzhou 310027, Zhejiang, China
    • 2Department of Theoretical Physics and History of Science, University of the Basque Country, EHU, UPV, P.O. Box 644, 48080 Bilbao, Spain and Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
    • 3Beijing Computational Science Research Center, Beijing 100193, China
    • 4Center for Controlled Quantum Systems and Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA
    • 5Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China

    • *lianao.wu@ehu.es

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    Vol. 97, Iss. 1 — January 2018

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    • Figure 1
      Figure 1

      Average fidelity F¯ of a two-level atomic system in the presence of a general relaxation noise and a Markovian dephasing noise under different parameters. Here R, D, and C represent the dynamics under pure relaxation noise, pure dephasing noise, and a mixture of noises, respectively. We choose Γβ/ω=1. (a) γβ/ω=0.1, (b) γβ/ω=0.5, and (c) γβ/ω=2.0.

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    • Figure 2
      Figure 2

      Average fidelity F¯ of a two-level atomic system in the presence of a non-Markovian relaxation noise and a non-Markovian dephasing noise under different parameters. Here R, D, and C represent the dynamics under pure relaxation noise, pure dephasing noise, and a mixture of noise, respectively. We choose Γβ/ω=1. (a) γβ/ω=0.1 and Γα/ω=2.0 and (b) γα/ω=0.1 and Γα/ω=1.0.

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    • Figure 3
      Figure 3

      Comparison of fidelities for a Λ-type three-level atomic system in the space of the evolution time-dephasing rate ωt−Γα/ω. The fidelity FΛ(t) is obtained by Eq. (10) in the presence of a non-Markovian relaxation noise and a Markovian dephasing noise. We choose the initial state as |ψ0〉=(|1〉+|2〉)/2. The parameters for relaxation noise are Γβ/ω=1 and γβ/ω=0.1. This diagram is divided into four regions according to the relations among the fidelities under composite noise C, of single relaxation noise R, and of single dephasing noise D.

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