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Entropy

Quantum Density Peak Clustering Algorithm

Zhihao Wu, Tingting Song, Yanbing Zhang

Published Feb 3, 2022• 2 citations
Publisher

Abstract

A widely used clustering algorithm, density peak clustering (DPC), assigns different attribute values to data points through the distance between data points, and then determines the number and range of clustering by attribute values. However, DPC is inefficient when dealing with scenes with a large amount of data, and the range of parameters is not easy to determine. To fix these problems, we propose a quantum DPC (QDPC) algorithm based on a quantum DistCalc circuit and a Grover circuit. The time complexity is reduced to O(log(N2)+6N+N), whereas that of the traditional algorithm is O(N2). The space complexity is also decreased from O(N·⌈logN⌉) to O(⌈logN⌉).

DOI
10.3390/e24020237

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A widely used clustering algorithm, density peak clustering (DPC), assigns different attribute values to data points through the distance between data points, and then determines the number and range of clustering by attribute values. However, DPC is inefficient when dealing with scenes with a large amount of data, and the range of parameters is not easy to determine. To fix these problems, we propose a quantum DPC (QDPC) algorithm based on a quantum DistCalc circuit and a Grover circuit. The time complexity is reduced to O(log(N2)+6N+N), whereas that of the traditional algorithm is O(N2). The space complexity is also decreased from O(N·⌈logN⌉) to O(⌈logN⌉).
Clustering is a fundamental task in unsupervised learning. The goal is to partition unlabeled data into clusters such that similar elements are assigned to the same cluster, while elements in different clusters are dissimilar. We propose a quantum Monte Carlo approach to density estimation, a key routine in density peak clustering. Building on this approach, we develop quantum algorithms for the full clustering problem and three related tasks: decision clustering, cluster counting, and heavy cluster counting. For each one, we establish a polynomial quantum query speedup under assumptions on the scaling of dataset-dependent parameters. Numerical experiments suggest that these conditions are satisfied for several practically relevant settings.
The density peak anomaly detection algorithm based on KNN, one of the most frequently utilized classical algorithms, is widely applied in communication fields, such as network fault detection, network traffic detection, user behavior detection, and network intrusion detection. In this algorithm, the local density value and KNN distance of all data points must be calculated, which faces enormous computational cost and computational delay challenges when the data set is processed as the network scale increases. To address this trouble, we introduce quantum computing into the algorithm and propose a quantum version of the density peak anomaly detection algorithm based on KNN. The proposed quantum algorithm first utilizes the inner product estimate algorithm and the quantum minimum search algorithm to accelerate the determination of the K nearest neighbor set of each data point and the calculation of KNN distance. Then, it performs amplitude estimation to concurrently obtain the local density of all data points. Our quantum algorithm is shown to be exponentially faster than its classical counterpart in the dimensionality of the data points and polynomially faster than the classical algorithm in the number of data points.
It is getting harder to deal with the large data sets by the classical hierarchical clustering algorithm, so we propose an efficient quantum hierarchical clustering algorithm, in which the quantum bit (qubit) is used to represent the data point in the space.For quantum entanglement, the distance between two data points is calculated through adding an auxiliary particle to construct the entangled state.Then a projective measurement is performed on the auxiliary particle alone.The distance between two points is acquired by the projective measurement.We use the distance of the cluster centroids as a measure of similarity between clusters.Also, based on the principle of the minimum cluster centroids distance, the nearest two clusters are merged.We aim at improving time and space complexity and effect of the clustering of the hierarchical clustering algorithm.
Abstract Clustering algorithms are of fundamental importance when dealing with large unstructured datasets and discovering new patterns and correlations therein, with applications ranging from scientific research to medical imaging and marketing analysis. In this work, we introduce a quantum version of the density peak clustering algorithm, built upon a quantum routine for minimum finding. We prove a quantum speedup for a decision version of density peak clustering depending on the structure of the dataset. Specifically, the speedup is dependent on the heights of the trees of the induced graph of nearest-highers, i.e. the graph of connections to the nearest elements with higher density. We discuss this condition, showing that our algorithm is particularly suitable for high-dimensional datasets. Finally, we benchmark our proposal with a toy problem on a real quantum device.
Traditional clustering algorithms, such as k-means and DBSCAN, often face significant challenges when applied to big data. The computational complexity associated with distance calculations and nearest neighbor searches scales poorly with dataset size, limiting their effectiveness. This paper proposes a novel approach to clustering inspired by quantum measurement theory, specifically quantum-inspired nearest neighbor search. We leverage concepts from quantum mechanics, such as superposition and measurement, to design clustering algorithms that can efficiently identify clusters within high-dimensional datasets. The core idea is to treat the clustering problem as a measurement process, where candidate cluster centers are repeatedly measured against data points, and the most likely cluster centers are selected. The resulting algorithms aim to provide scalability improvements over conventional methods, particularly for datasets with a large number of features and data points. The effectiveness of the proposed algorithms is demonstrated through theoretical analysis and conceptual explanations, highlighting the potential benefits and future research directions.
Tensor networks, which have been traditionally used to simulate many-body physics, have recently gained significant attention in the field of machine learning due to their powerful representation capabilities. In this work, we propose a density-based clustering algorithm inspired by tensor networks. We encode classical data into tensor network states on an extended Hilbert space and train the tensor network states to capture the features of the clusters. Here, we define density and related concepts in terms of fidelity, rather than using a classical distance measure. We evaluate the performance of our algorithm on six synthetic data sets, four real world data sets, and three commonly used computer vision data sets. The results demonstrate that our method provides state-of-the-art performance on several synthetic data sets and real world data sets, even when the number of clusters is unknown. Additionally, our algorithm performs competitively with state-of-the-art algorithms on the MNIST, USPS, and Fashion-MNIST image data sets. These findings reveal the great potential of tensor networks for machine learning applications.