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Optical pulse design method for carrying out high fidelity control on ensemble quantum bits

A high-fidelity, design method technology, applied in the field of quantum manipulation, can solve problems such as long qubit time and high non-resonance excitation, so as to reduce the possibility of decoherence effect and realize the effect of high-fidelity manipulation

Pending Publication Date: 2021-01-15
SUZHOU UNIV
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  • Abstract
  • Description
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  • Application Information

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Problems solved by technology

[0006] The technical problem solved by the present invention is: the system has poor robustness to frequency detuning during the pulse action process, the pulse has poor robustness to the uneven distribution or instantaneous change of laser intensity, and has high sensitivity to other ions near the qubit. non-resonant excitation, the qubit stays in the excited state for a long time

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  • Optical pulse design method for carrying out high fidelity control on ensemble quantum bits
  • Optical pulse design method for carrying out high fidelity control on ensemble quantum bits
  • Optical pulse design method for carrying out high fidelity control on ensemble quantum bits

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Embodiment 1

[0042] An optical pulse design method for high-fidelity manipulation of ensemble qubits, according to the initial state |1> and the target state of the system Among them, θ a and are two angles, θ a In the range of [0, π], characterize the distribution of layout numbers on the two energy levels of |0> and |1>; Take the value in the range of [0, 2π] to represent the relative phase between the qubit energy states |0> and |1>, and use the adiabatic shortcut technology based on the Lewis-Riesenfeld invariant theory to reverse solve the time-dependent three-level system The Schrödinger equation regards the laser intensity fluctuation as a perturbation, uses the perturbation theory to calculate the deviation caused by the intensity fluctuation to the quantum manipulation fidelity, and uses the second-order differential of the fidelity to the Rabi frequency fluctuation, that is, the system error sensitivity, to obtain To characterize this deviation, the closer the system error ...

Embodiment 2

[0074] An optical pulse design method for high-fidelity manipulation of ensemble qubits based on Embodiment 1, all a in formula (7) n The values ​​are all zero. at this time:

[0075]

[0076] γ(t) is shown in formula (6), and its Gaussian term parameters are shown in the above table. The Rabi frequency of the corresponding light pulse Ω p,s Evolution over time see appendix figure 2 , where the solid line is Ω p , the dotted line is Ω s , the pulse duration is 4μs, the maximum instantaneous value of the Rabi frequency does not exceed 3MHz, and the value is not 0 at the beginning and end moments.

[0077] attached image 3 It is the evolution of the layout number of each energy level of the system with time under the action of the pulse when there is no frequency detuning. All the layout numbers of the quantum system start from the ground state |1>, and finally evenly distribute on the energy levels |1> and |0>, which is consistent with the expected initial state and...

Embodiment 3

[0081] An optical pulse design method for high-fidelity manipulation of ensemble qubits based on Embodiment 1, in formula (7) a n All even and odd terms of satisfy the following two conditions respectively:

[0082] a 1 +3a 3 +5a 5 +7a 7 = 0,

[0083] a 2 +2a 4 +3a 6 +4a 8 = 0.5.

[0084] Under the constraints of this condition, in A m In the case of a constant close to 0, the value of the two-color pulse at the beginning and end moments is always equal to 0, that is, Ω p,s (t=0,t f )=0. a n The additional degrees of freedom in can be arbitrarily selected in the range of real numbers, and the optical pulse can be constructed under the constraints of the above conditions, and the quantum system can be manipulated quickly and with high fidelity to create a predetermined target state |ψ target >. Here, in the simplest case a 2 = 0.5, a 1.3.4.5.6.7.8 =0 as an example to describe the shape and control performance of the light pulse.

[0085] attached Figure 4 , ...

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Abstract

The invention discloses an optical pulse design method for carrying out high fidelity control on ensemble quantum bits, which adopts a reverse engineering method based on Lewis-Riesenfield invariantsand utilizes the perturbation theory and the concept of system error sensitivity to construct a quick and efficient double-color optical pulse with high robustness for frequency detuning and laser intensity fluctuation. The pulse can be applied to a three-level system with non-uniform broadening, and any superposition state of ensemble quantum bits is created with high fidelity. In the pulse action process, quantum control has high robustness for instantaneous change or spatial non-uniform distribution of laser intensity, the robustness can improve the signal-to-noise ratio of a detection signal, and the experiment difficulty is reduced; meanwhile, the time for the quantum bits to be in the excited state is remarkably shortened, the decoherence effect of the quantum bits can be greatly reduced to ensure high-fidelity control is achieved.

Description

technical field [0001] The invention belongs to the field of quantum manipulation, and in particular relates to an optical pulse design theory capable of creating an arbitrary superposition state of bond ensemble qubits quickly and with high fidelity. Background technique [0002] Quantum computing mainly follows the laws of quantum mechanics and quantum dynamics. Compared with classical computing, it has faster computing speed and can solve many difficult problems in classical computing. Therefore, it can be widely used in quantum neural network simulation, artificial intelligence , large prime factorization, unordered database retrieval, etc. The first step in working on quantum computing is to initialize qubits to an arbitrary qubit superposition state quickly and with high fidelity. There are many kinds of physical carriers for qubits. Therefore, according to the characteristics of the systems where different carriers are located, appropriate optical pulses should be de...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06N10/00G01J1/42G02F1/11
CPCG06N10/00G01J1/4257G02F1/11G01J2001/4238G06N10/40
Inventor 延英莫泽陈添凤万林王嘉仪
Owner SUZHOU UNIV
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