A new method of constructing adversarial examplesfor quantum variational circuits

A quantum variational circuit is a quantum machine learning model similar to a neural network.A crafted adversarial example can lead to incorrect results for the model.Using adversarial examples to train the model will greatly improve its robustness.The existing method is to use automatic differentials or finite difference to obtain a gradient and use it to construct adversarial examples.This paper proposes an innovative method for constructing adversarial examples of quantum variational circuits.In this method,the gradient can be obtained by measuring the expected value of a quantum bit respectively in a series quantum circuit.This method can be used to construct the adversarial examples for a quantum variational circuit classifier.The implementation results prove the effectiveness of the proposed method.Compared with the existing method,our method requires fewer resources and is more efficient.

Variational quantum semi-supervised classifier based on label propagation

Label propagation is an essential semi-supervised learning method based on graphs,which has a broad spectrum of applications in pattern recognition and data mining.This paper proposes a quantum semi-supervised classifier based on label propagation.Considering the difficulty of graph construction,we develop a variational quantum label propagation(VQLP)method.In this method,a locally parameterized quantum circuit is created to reduce the parameters required in the optimization.Furthermore,we design a quantum semi-supervised binary classifier based on hybrid Bell and Z bases measurement,which has a shallower circuit depth and is more suitable for implementation on near-term quantum devices.We demonstrate the performance of the quantum semi-supervised classifier on the Iris data set,and the simulation results show that the quantum semi-supervised classifier has higher classification accuracy than the swap test classifier.This work opens a new path to quantum machine learning based on graphs.

A backdoor attack against quantum neural networks with limited information

Backdoor attacks are emerging security threats to deep neural networks.In these attacks,adversaries manipulate the network by constructing training samples embedded with backdoor triggers.The backdoored model performs as expected on clean test samples but consistently misclassifies samples containing the backdoor trigger as a specific target label.While quantum neural networks(QNNs)have shown promise in surpassing their classical counterparts in certain machine learning tasks,they are also susceptible to backdoor attacks.However,current attacks on QNNs are constrained by the adversary's understanding of the model structure and specific encoding methods.Given the diversity of encoding methods and model structures in QNNs,the effectiveness of such backdoor attacks remains uncertain.In this paper,we propose an algorithm that leverages dataset-based optimization to initiate backdoor attacks.A malicious adversary can embed backdoor triggers into a QNN model by poisoning only a small portion of the data.The victim QNN maintains high accuracy on clean test samples without the trigger but outputs the target label set by the adversary when predicting samples with the trigger.Furthermore,our proposed attack cannot be easily resisted by existing backdoor detection methods.

基于DenseNet的经典-量子混合分类模型

现有的图像分类模型越来越复杂,计算时所需的硬件资源和计算时间不断增加。针对该问题提出一种基于DenseNet的经典-量子混合分类模型(CQDenseNet模型)。首先,使用一个可在噪声中尺度量子(NISQ)设备上运行的变分量子电路(VQC)作为分类器,替换DenseNet全连接层;其次,使用迁移学习,利用在ImageNet数据集上预先训练好的DenseNet模型作为CQDenseNet的预训练模型;最后,将CQDenseNet模型在中草药分类数据集和CIFAR-100数据集上与基准模型AlexNet、GoogLeNet、VGG19、ResNet和DenseNet-169进行对比。实验结果表明,CQDenseNet模型比所有基准模型中表现最好的基准模型:准确率分别提高了2.2、7.4个百分点,精确率分别提高了2.2、7.3个百分点,召回率分别提高了2.2、7.1个百分点,F1值分别提高了2.3、6.4个百分点,说明了经典-量子混合模型的性能优于经典模型。

Near-term quantum computing techniques: Variational quantum algorithms, error mitigation, circuit compilation, benchmarking and classical simulation

Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Although it has seen a major boost in the last decade,we are still a long way from reaching the maturity of a full-fledged quantum computer.That said,we will be in the noisy-intermediate scale quantum(NISQ)era for a long time,working on dozens or even thousands of qubits quantum computing systems.An outstanding challenge,then,is to come up with an application that can reliably carry out a nontrivial task of interest on the near-term quantum devices with non-negligible quantum noise.To address this challenge,several near-term quantum computing techniques,including variational quantum algorithms,error mitigation,quantum circuit compilation and benchmarking protocols,have been proposed to characterize and mitigate errors,and to implement algorithms with a certain resistance to noise,so as to enhance the capabilities of near-term quantum devices and explore the boundaries of their ability to realize useful applications.Besides,the development of near-term quantum devices is inseparable from the efficient classical sim-ulation,which plays a vital role in quantum algorithm design and verification,error-tolerant verification and other applications.This review will provide a thorough introduction of these near-term quantum computing techniques,report on their progress,and finally discuss the future prospect of these techniques,which we hope will motivate researchers to undertake additional studies in this field.

基于随机量子层的变分量子卷积神经网络鲁棒性研究

近年来,量子机器学习被证明与经典机器学习一样会被一个精心设计的微小扰动干扰从而造成识别准确率严重下降。目前增加模型对抗鲁棒性的方法主要有模型优化、数据优化和对抗训练。文章从模型优化角度出发,提出了一种新的方法,旨在通过将随机量子层与变分量子神经网络连接组成新的量子全连接层,与量子卷积层和量子池化层组成变分量子卷积神经网络(Variational Quantum Convolutional Neural Networks,VQCNN),来增强模型的对抗鲁棒性。文章在KDD CUP99数据集上对基于VQCNN的量子分类器进行了验证。实验结果表明,在快速梯度符号法(Fast Gradient Sign Method,FGSM)、零阶优化法(Zeroth-Order Optimization,ZOO)以及基于遗传算法的生成对抗样本的攻击下,文章提出的VQCNN模型准确率下降值分别为11.18%、15.21%和33.64%,与其它4种模型相比准确率下降值最小。证明该模型在对抗性攻击下具有更高的稳定性,其对抗鲁棒性更优秀。同时在面对基于梯度的攻击方法(FGSM和ZOO)时的准确率下降值更小,证明文章提出的VQCNN模型在面对此类攻击时更有效。

Diabetic Retinopathy Detection Using Classical-Quantum Transfer Learning Approach and Probability Model

Diabetic Retinopathy(DR)is a common complication of diabetes mellitus that causes lesions on the retina that affect vision.Late detection of DR can lead to irreversible blindness.The manual diagnosis process of DR retina fundus images by ophthalmologists is time consuming and costly.While,Classical Transfer learning models are extensively used for computer aided detection of DR;however,their maintenance costs limits detection performance rate.Therefore,Quantum Transfer learning is a better option to address this problem in an optimized manner.The significance of Hybrid quantum transfer learning approach includes that it performs heuristically.Thus,our proposed methodology aims to detect DR using a hybrid quantum transfer learning approach.To build our model we extract the APTOS 2019 Blindness Detection dataset from Kaggle and used inception-V3 pre-trained classical neural network for feature extraction and Variational Quantum classifier for stratification and trained our model on Penny Lane default device,IBM Qiskit BasicAer device and Google Cirq Simulator device.Both models are built based on PyTorch machine learning library.We bring about a contrast performance rate between classical and quantum models.Our proposed model achieves an accuracy of 93%–96%on the quantum hybrid model and 85%accuracy rate on the classical model.So,quantum computing can harness quantum machine learning to do work with power and efficiency that is not possible for classical computers.

基于变分量子虚时演化和UCC Ansatz的基态求解器

对于量子多体体系,其基态的求解十分重要。变分量子本征求解器VQE是一种基于量子计算的变分基态求解算法,由于其需要结合量子电路和经典的变分算法,使得量子电路的复杂性和变分算法的有效性显得极其重要。针对量子分子体系,提出了一种变分基态求解器。运用单电子约化密度矩阵分析得到在自然分子轨道表象下的电子轨道占据数,根据占据数大小简化了体系哈密顿量和相应的UCC ansatz线路。并运用变分量子虚时演化算法替代VQE中常用的梯度算法,因此不易受到参数空间的梯度分布的影响,使得变分过程收敛更快,更具鲁棒性。

面向图像分类的混合量子长短期记忆神经网络构建方法

长短期记忆(long-short tern memory,LSTM)神经网络通过引入记忆单元来解决长期依赖、梯度消失和梯度爆炸问题,广泛应用于时间序列分析与预测.将量子计算与LSTM神经网络结合将有助于提高其计算效率并降低模型参数个数,从而显著改善传统LSTM神经网络的性能.本文提出一种可用于图像分类的混合量子LSTM(hybrid quantum LSTM,HQLSTM)网络模型,利用变分量子电路代替经典LSTM网络中的神经细胞,以实现量子网络记忆功能,同时引入Choquet离散积分算子来增强数据之间的聚合程度.HQLSTM网络中的记忆细胞由多个可实现不同功能的变分量子电路(variation quantum circuit,VQC)构成,每个VQC由三部分组成:编码层利用角度编码降低网络模型设计的复杂度;变分层采用量子自然梯度优化算法进行设计,使得梯度下降方向不以特定参数为目标,从而优化参数更新过程,提升网络模型的泛化性和收敛速度;测量层利用泡利Z门进行测量,并将测量结果的期望值输入到下一层实现对量子电路中有用信息的提取.在MNIST,FASHION-MNIST和CIFAR数据集上的图像分类实验结果表明,与经典LSTM、量子LSTM相比,HQLSTM模型获得了较高的图片分类精度和较低的损失值.同时,HQLSTM、量子LSTM网络空间复杂度相较于经典的LSTM网络实现了明显的降低.

基于多量子滤波器的QCNN算法预测厌氧消化性能

厌氧消化是可再生能源生产中一种具有前景的技术,沼气是由有机废物通过厌氧消化产生的生物能源,预测厌氧消化产生的沼气产量并进行管控是必要的。设计了一种具有短期记忆的多量子滤波器量子卷积神经网络,利用参数化变分量子电路接受数据“时间窗”以模拟短期记忆,并在多量子滤波结构中舍弃过多的线路迭代和参数数量使其具有更高的表达性。在量子线路框架中,设计了最优的卷积、池化层线路,能够更好地提取特征因子中的隐藏状态;同时对废物管理数据进行严格的预处理,通过指数平滑去除特征中趋势和季节性。该算法的精度达到了83.30%,比CNN模型精度提升了8%,RMSE和MAE值也均优于ANN、KNN、CNN等经典模型。

基于量子门线路与机器学习协同设计的变分量子神经网络

以人工神经网络(ANN)模型为基础,通过与量子并行计算、量子门线路以及变分量子线路等量子理论与量子力学概念相结合提出了一种优化的变分量子神经网络(VQNN)模型,该模型是由可在噪声中尺度量子(NISQ)设备上运行的量子线路结合机器学习(ML)策略构成的一种量子经典混合计算模型。其中量子线路由两部分组成:量子态编码线路用于将经典数据编码为量子态数据;变分量子线路(VQC)则学习目标状态并将信息编码到一个真实的量子数据结构之中。最终通过测量VQC量子态输出获得经典概率输出分布,利用经典计算机进行变分量子线路的参数优化处理,这种结构使得VQC与经典ML很容易地融合。进一步探索了使用VQNN来建立基于实际应用的分类器,将其应用在网络攻击检测领域。实验结果表明,对于KDD CUP99数据集,VQNN具有相对较高的检测性能,且均高于其他经典对比检测模型以及量子门线路神经网络模型。此外,该VQNN可以部署在近期绝大多数的NISQ设备中。同时,所提出的VQNN是首个可以部署在NISQ中进行网络攻击检测的模型。