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Quantum Machine Intelligence

Time series quantum classifiers with amplitude embedding

Manuel Pegalájar Cuéllar, Carlos Cano, L. G. B. Ruiz, Lorenzo Servadei

Published Nov 27, 2023• 14 citations
Publisher

Abstract

Abstract Quantum Machine Learning was born during the past decade as the intersection of Quantum Computing and Machine Learning. Today, advances in quantum computer hardware and the design of simulation frameworks able to run quantum algorithms in classic computers make it possible to extend classic artificial intelligence models to a quantum environment. Despite these achievements, several questions regarding the whole quantum machine learning pipeline remain unanswered, for instance the problem of classical data representation on quantum hardware, or the methodologies for designing and evaluating quantum models for common learning tasks such as classification, function approximation, clustering, etc. These problems become even more difficult to solve in the case of Time Series processing, where the context of past historical data may influence the behavior of the decision-making model. In this piece of research, we address the problem of Time Series classification using quantum models, and propose an efficient and compact representation of time series in quantum data using amplitude embedding. The proposal is capable of representing a time series of length n in $$log_2(n)$$ l o g 2 ( n ) computational units, and experiments conducted on benchmark time series classification problems show that quantum models designed for classification can also outperform the accuracy of classic methods.

DOI
10.1007/s42484-023-00133-0

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This work focuses on quantum machine learning and analyzes the power of one single qubit to solve classical machine learning problems. We explore possible strategies to address traditional supervised, unsupervised, and reinforcement learning tasks. In particular, we study binary and multinomial classification, regression problems, time series forecasting, clustering, and quantum reinforcement learning. Our results suggest that the same methodology could be used to address all three types of learning with different measurement strategies and, despite the strong limitation of reduced data dimensionality of the candidate problems, a single qubit can achieve similar or even improved performance with respect to state-of-the-art classic machine learning methods in many cases. As simulating the evolution of one qubit state is computationally efficient, our study enables the possibility to use the qubit model as a candidate solution to implement simple decision-making machine learning models in hardware with extremely low memory resources such as embedded systems or edge devices. The outcomes provided could be also of interest in academia and for the construction of demonstrators using low-scale contemporary quantum hardware.
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Quantum computing has inspired new ways to represent and process data, offering perspectives that can also benefit classical machine learning. In this work, we investigate how quantum-inspired data representations can be integrated into classical machine learning classifiers such as Logistic Regression, Support Vector Machines, and Naive Bayes for binary classification tasks. The proposed approach utilizes a simple amplitude-based encoding that normalizes feature vectors and incorporates phase-like transformations, assisting classical models to capture complex interactions and patterns in the data similar to quantum information processing. We evaluate this approach on both synthetic and three other benchmark datasets, comparing standard and quantum-inspired data representations. The results highlights that the quantum-inspired data encoding often matches or improves classifier performance in terms of accuracy, F1-Score, and precision. Additionally, the normalized encoding provides a more structured representation of the data, which can help with interpretability and visualization. These results highlight the potential of quantum-inspired transformations as a practical and effective tool for improving classical machine learning pipelines without requirement of quantum hardware.
This research paper delves into the realm of quantum machine learning (QML) by conducting a comprehensive study on time-series data. The primary objective is to compare the results and time complexity of classical machine learning algorithms on traditional hardware to their quantum counterparts on quantum computers. As the amount and complexity of time-series data in numerous fields continues to expand, the investigation of advanced computational models becomes critical for efficient analysis and prediction. We employ a time-series dataset that include temperature records from different nations throughout the world spanning the previous half of the century. The study compares the performance of classical machine learning algorithms to quantum algorithms, which use the concepts of superposition and entanglement to handle subtle temporal patterns in time-series data. This study attempts to reveal the different benefits and drawbacks of quantum machine learning in the time-series domain through rigorous empirical analysis. The findings of this study not only help to comprehend the applicability of quantum algorithms in real-world contexts, but they also open the way for future advances in utilizing quantum computing for increased time-series analysis and prediction. This study's findings could have ramifications in industries ranging from finance to healthcare, where precise forecasting using time-series data is critical for informed decision-making.