中国物理B ›› 2016, Vol. 25 ›› Issue (8): 80304-080304.doi: 10.1088/1674-1056/25/8/080304

• GENERAL • 上一篇    下一篇

Quantum speed limits of a qubit system interacting with a nonequilibrium environment

Zhi He(贺志), Chun-Mei Yao(姚春梅), Li Li(李莉), Qiong Wang(王琼)   

  1. College of Physics and Electronics, Hunan University of Arts and Science, Changde 415000, China
  • 收稿日期:2016-02-28 修回日期:2016-05-03 出版日期:2016-08-05 发布日期:2016-08-05
  • 通讯作者: Zhi He E-mail:hz9209@126.com
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grants Nos. 61505053 and 61475045), the Natural Science Foundation of Hunan Province, China(Grant No. 2015JJ3092), the School Foundation from the Hunan University of Arts and Science (Grant No. 14ZD01), the Fund from the Key Laboratory of Photoelectric Information Integration and Optical Manufacturing Technology of Hunan Province, China, and the Construction Program of the Key Discipline in Hunan University of Arts and Science (Optics).

Quantum speed limits of a qubit system interacting with a nonequilibrium environment

Zhi He(贺志), Chun-Mei Yao(姚春梅), Li Li(李莉), Qiong Wang(王琼)   

  1. College of Physics and Electronics, Hunan University of Arts and Science, Changde 415000, China
  • Received:2016-02-28 Revised:2016-05-03 Online:2016-08-05 Published:2016-08-05
  • Contact: Zhi He E-mail:hz9209@126.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grants Nos. 61505053 and 61475045), the Natural Science Foundation of Hunan Province, China(Grant No. 2015JJ3092), the School Foundation from the Hunan University of Arts and Science (Grant No. 14ZD01), the Fund from the Key Laboratory of Photoelectric Information Integration and Optical Manufacturing Technology of Hunan Province, China, and the Construction Program of the Key Discipline in Hunan University of Arts and Science (Optics).

摘要: The speed of evolution of a qubit undergoing a nonequilibrium environment with spectral density of general ohmic form is investigated. First we reveal non-Markovianity of the model, and find that the non-Markovianity quantified by information backflow of Breuer et al. [Phys. Rev. Lett. 103 210401 (2009)] displays a nonmonotonic behavior for different values of the ohmicity parameter s in fixed other parameters and the maximal non-Markovianity can be achieved at a specified value s. We also find that the non-Markovianity displays a nonmonotonic behavior with the change of a phase control parameter. Then we further discuss the relationship between quantum speed limit (QSL) time and non-Markovianity of the open-qubit system for any initial states including pure and mixed states. By investigation, we find that the QSL time of a qubit with any initial states can be expressed by a simple factorization law: the QSL time of a qubit with any qubit-initial states are equal to the product of the coherence of the initial state and the QSL time of maximally coherent states, where the QSL time of the maximally coherent states are jointly determined by the non-Markovianity, decoherence factor and a given driving time. Moreover, we also find that the speed of quantum evolution can be obviously accelerated in the wide range of the ohmicity parameter, i.e., from sub-Ohmic to Ohmic and super-Ohmic cases, which is different from the thermal equilibrium environment case.

关键词: quantum speed limits, non-Markovianity, nonequilibrium environment

Abstract: The speed of evolution of a qubit undergoing a nonequilibrium environment with spectral density of general ohmic form is investigated. First we reveal non-Markovianity of the model, and find that the non-Markovianity quantified by information backflow of Breuer et al. [Phys. Rev. Lett. 103 210401 (2009)] displays a nonmonotonic behavior for different values of the ohmicity parameter s in fixed other parameters and the maximal non-Markovianity can be achieved at a specified value s. We also find that the non-Markovianity displays a nonmonotonic behavior with the change of a phase control parameter. Then we further discuss the relationship between quantum speed limit (QSL) time and non-Markovianity of the open-qubit system for any initial states including pure and mixed states. By investigation, we find that the QSL time of a qubit with any initial states can be expressed by a simple factorization law: the QSL time of a qubit with any qubit-initial states are equal to the product of the coherence of the initial state and the QSL time of maximally coherent states, where the QSL time of the maximally coherent states are jointly determined by the non-Markovianity, decoherence factor and a given driving time. Moreover, we also find that the speed of quantum evolution can be obviously accelerated in the wide range of the ohmicity parameter, i.e., from sub-Ohmic to Ohmic and super-Ohmic cases, which is different from the thermal equilibrium environment case.

Key words: quantum speed limits, non-Markovianity, nonequilibrium environment

中图分类号:  (Decoherence; open systems; quantum statistical methods)

  • 03.65.Yz
03.67.Lx (Quantum computation architectures and implementations) 03.67.-a (Quantum information) 42.50.-p (Quantum optics)