论文标题

部分可观测时空混沌系统的无模型预测

Study of Adaptative Derivative-Assemble Pseudo-Trotter Ansatzes in VQE through qiskit API

论文作者

Alteg, Max, Chevalier, Baptiste, Mestoudjian, Octave, Rossi, Johan-Luca

论文摘要

为了回答量子相估计算法的问题不适合NISQ设备,并且允许人们超越经典计算机,设计了变异量子算法(VQAS)。我们感兴趣的主题是所谓的变分量子本质量(VQE)算法,最初设计用于模拟电子结构并计算给定分子的基态。 VQE由两个主要组成部分组成:ANSATZ和一个经典优化器。 ANSATZ在量子设备上运行,旨在模拟波功能,ANSATZ的参数将被优化,直到期望值为最小为止。 最初使用的第一个ANSATZ称为UCCSD,它基于耦合群集理论。考虑到UCCSD的主要问题是要优化的大量参数,这使我们引入了自适应导数组装的伪驱动器Ansatz VQE(Adapt-vQe),该参数确定了具有最小数量的参数的准正常ANSATZ。 Adapt-VQE的关键点是通过添加从预定的操作员量池中选择的操作员在每次一次一次性的一次性池中添加运算符,以确保在每个步骤中恢复最大的相关能量。有不同种类的适应性VQE,具体取决于运算符的起始库作为费米子 - 适应,Qubit-Adapt甚至基于量子的激发(QEB)。 我们的目标是实施前面提到的不同类型的Adapt-VQE。在对所有这些概念下的理论背景进行了快速审查之后,我们将使用Quiskit实施每种算法。我们还将在不同标准(例如参数数,精度或H2和LIH分子上使用的CNOT门数)上比较所有这些算法。然后,我们将对获得的结果进行小讨论。

In order to answer the problem of Quantum Phase Estimation Algorithm been not suitable for NISQ devices, and allows one to outperform classical computers, Variational Quantum Algorithms (VQAs) were designed. Our subject of interest is the so-called Variational Quantum Eigensolver (VQE) algorithm and was originally designed to simulate electronic structures and to compute the ground state of a given molecule. VQE is made of two main components : an ansatz and a classical optimizer. The ansatz runs on the quantum device and aims to simulate the wavefunction, the parameters of the ansatz will be optimized until the expectation value is minimum. The very first ansatz that has originally been used is called UCCSD and it is based on Coupled Cluster Theory. The main issue considering UCCSD is the large amount of parameters to optimize and this leads us to the introduction of Adaptive Derivative-Assembled Pseudo-Trotter ansatz VQE (ADAPT-VQE) which determines a quasi-optimal ansatz with a minimal number of parameters. The key point of ADAPT-VQE is to grow the ansatz at every step, by adding operators chosen from a pre-determined pool of operators one-at-a-time, assuring that the maximal amount of correlation energy is recovered at each step. There exists different kind of ADAPT-VQE depending on the starting pool of operators as the fermionic-ADAPT, the qubit-ADAPT or even the qubit excitation based (QEB). Our goal is to implement the different types of ADAPT-VQE mentioned before. After a quick review of the theoretical background under all of these concepts, we will implement each algorithm using quiskit. We will also compare all of these algorithms on different criterions such as the number of parameters, the accuracy or the number of CNOT gate used on H2 and LiH molecules. Then we will have a small discussion about the results we obtained.

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