• Chinese Physics B
  • Vol. 29, Issue 10, (2020)
Jie Sun1,2,3,† and Songfeng Lu1,3
Author Affiliations
  • 1Hubei Engineering Research Center on Big Data Security, School of Cyber Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
  • 2School of Internet, Anhui University, Hefei 30039, China
  • 3Shenzhen Huazhong University of Science and Technology Research Institute, Shenzhen 51806, China
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    DOI: 10.1088/1674-1056/aba2db Cite this Article
    Jie Sun, Songfeng Lu. On the time-independent Hamiltonian in real-time and imaginary-time quantum annealing[J]. Chinese Physics B, 2020, 29(10): Copy Citation Text show less

    Abstract

    We present the analog analogue of Grover’s problem as an example of the time-independent Hamiltonian for applying the speed limit of the imaginary-time Schr?dinger equation derived by Okuyama and Ohzeki and the new class of energy-time uncertainty relation proposed by Kieu. It is found that the computational time of the imaginary-time quantum annealing of this Grover search can be exponentially small, while the counterpart of the quantum evolution driven by the real-time Schr?dinger equation could only provide square root speedup, compared with classic search. The present results are consistent with the cases of the time-dependent quantum evolution of the natural Grover problem in previous works. We once again emphasize that the logarithm and square root algorithmic performances are generic in imaginary-time quantum annealing and quantum evolution driven by real-time Schr?dinger equation, respectively. Also, we provide evidences to search deep reasons why the imaginary-time quantum annealing can lead to exponential speedup and the real-time quantum annealing can make square root speedup.
    iddt|ψ(t)=H|ψ(t),|ψ(t)=|ϕ0,(1)

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    iddt|ϕ(t)=β1|ϕ(t),|ϕ(t)=|ϕ0,(2)

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    2Δt×ΔE0,(3)

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    ΔE0=ϕ0|H2|ϕ0ϕ0|H|ϕ02(4)

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    H=E|ss|+E|ww|,(5)

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    ϕ0|H2|ϕ0ϕ0|H|ϕ02=E1N1N2(6)

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    Δt2E1/N1/N2.(7)

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    Δt2E×NO(N).(8)

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    H=(sreiθreiθu),(9)

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    ω2=(su)2+4r2.(10)

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    |ϕ0=(10)(11)

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    |ϕ1=(ab),(|a|2+|b|2=1)(12)

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    Δt=2ωarcsin|b|.(13)

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    H=E(1+x2x1x2x1x21x2),(14)

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    2Δt×ΔE02+E02,(E0=ϕ0|H|ϕ0),(15)

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    Δt=max{2ΔE02+E02,2ΔE0},(16)

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    ddt|ψ(t)=H|ψ(t),ddt|ϕ(t)=β1|ϕ(t),|ψ(0)=|ϕ(0)=|ψ0,(17)

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    |||ψ(τ)exp(τψ0|H|ψ0)|ψ(0)||ψ0|H2|ψ0ψ0|H|ψ021exp(τψ0|H|ψ0)ψ0|H|ψ0.(18)

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    |||||ψ(τ)|||weτψ0|H|ψ0|ψ(0)||=[|||ψ(τ)||2+e2τψ0|H|ψ02N|||ψ(τ)||eτψ0|H|ψ0]1/2=[(|||ψ(τ)||1Neτψ0|H|ψ0)2+(11N)e2τψ0|H|ψ0]1/211Neτψ0|H|ψ0.(19)

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    1eτE(1+1/N)eτE(1+1/N)N(1+1/N).(20)

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    τ12lnNEO(lnN).(21)

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    Δxc2ΔE+αGc4ΔE,(22)

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    Jie Sun, Songfeng Lu. On the time-independent Hamiltonian in real-time and imaginary-time quantum annealing[J]. Chinese Physics B, 2020, 29(10):
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