Learning compressed, latent representations of quantum states can help us understand and simulate the natural world. To this end, one needs devices that can capture and reliably process information using quantum-mechanical effects. Whilst we currently lack a device that can achieve this goal, we are well into the era of noisy, intermediate-scale quantum (NISQ) computers—quantum machines with $$50{-}100$$ noisy qubits—which have catalysed machine learning applications. This chapter provides the main ideas underpinning learning with NISQ machines. It also provides insight into the architectures and training schemes currently in use, as well as the limitations and potential futures of the field.
Learning compressed, latent representations of quantum states can help us understand and simulate the natural world. To this end, one needs devices that can capture and reliably process information using quantum-mechanical effects. Whilst we currently lack a device that can achieve this goal, we are well into the era of noisy, intermediate-scale quantum (NISQ) computers—quantum machines with 50−100 noisy qubits—which have catalysed machine learning applications. This chapter provides the main ideas underpinning learning with NISQ machines. It also provides insight into the architectures and training schemes currently in use, as well as the limitations and potential futures of the field.
Quantum computing has emerged as a transformative paradigm capable of addressing computational challenges beyond the reach of classical systems.In the current era of Noisy Intermediate-Scale Quantum (NISQ) devices, practical quantum hardware is characterized by limited qubit counts, short coherence times, gate errors, and the absence of full error correction.Despite these constraints, significant progress has been made in developing quantum machine learning (QML) techniques tailored to operate on near-term quantum processors.This paper presents a comprehensive review of Quantum Machine Learning in the context of NISQ computing.We first outline the fundamental principles of quantum computing, including qubits, superposition, entanglement, and quantum parallelism, followed by a detailed discussion of the NISQ computing model and its hardware limitations.The review then examines hybrid quantum-classical learning frameworks, variational quantum algorithms, quantum data encoding strategies, and noise mitigation techniques that enable practical implementation on existing platforms.Emerging applications across healthcare, finance, cybersecurity, climate modeling, and materials science are also surveyed to highlight the real-world potential of QML.Furthermore, key challenges such as scalability, trainability issues, and algorithmic robustness are analyzed, along with current research efforts aimed at overcoming these barriers.The paper concludes by identifying promising future directions for advancing QML toward quantum advantage.This review aims to provide researchers and practitioners with a structured understanding of the capabilities, limitations, and opportunities of quantum machine learning in the NISQ era .
Some of the most significant achievements of the modern era of particle physics, such as the discovery of the Higgs boson, have been made possible by the tremendous effort in building and operating large-scale experiments like the Large Hadron Collider or the Tevatron. In these facilities, the ultimate theory to describe matter at the most fundamental level is constantly probed and verified. These experiments often produce large amounts of data that require storing, processing, and analysis techniques that continually push the limits of traditional information processing schemes. Thus, the High-Energy Physics (HEP) field has benefited from advancements in information processing and the development of algorithms and tools for large datasets. More recently, quantum computing applications have been investigated to understand how the community can benefit from the advantages of quantum information science. Nonetheless, to unleash the full potential of quantum computing, there is a need to understand the quantum behavior and, thus, scale up current algorithms beyond what can be simulated in classical processors. In this work, we explore potential applications of quantum machine learning to data analysis tasks in HEP and how to overcome the limitations of algorithms targeted for Noisy Intermediate-Scale Quantum (NISQ) devices.
The rapid advancement of quantum computing hardware and software has ushered in a new era for computational science, promising to tackle problems that are intractable for classical computers. Parallelly, machine learning (ML) has revolutionized data analysis and artificial intelligence. The confluence of these two fields, known as Quantum Machine Learning (QML), aims to harness the principles of quantum mechanics-such as superposition, entanglement, and interference-to enhance and redefine classical machine learning algorithms. This survey provides a comprehensive overview of the burgeoning field of QML. We begin by elucidating the fundamental quantum concepts that underpin QML approaches. We then present a detailed taxonomy and analysis of prominent QML algorithms, categorizing them into quantum-enhanced classical models and fully quantum models. Key families of algorithms discussed include Quantum Support Vector Machines (QSVM), Quantum Neural Networks (QNNs), and Quantum Generative Adversarial Networks (QGANs). For each, we explain the theoretical quantum advantage, the circuit implementation, and the current limitations. Furthermore, we delve into the critical challenges facing the practical realization of QML, including the pervasive issue of noise in Noisy Intermediate-Scale Quantum (NISQ) devices, the problem of barren plateaus in training quantum circuits, and the complexities of efficient data encoding (quantum feature maps). We also present a small-scale experimental simulation of a variational quantum classifier on a standardized dataset, demonstrating its principle and comparing its performance with a classical counterpart. Finally, the paper discusses the future trajectory of QML, highlighting the importance of error mitigation, hybrid quantum-classical architectures, and the development of quantum-specific learning inductive biases. We conclude that while fault-tolerant quantum computers remain on the horizon, QML represents a paradigm shift with the potential to deliver profound computational advantages in the coming decades.
As medium-scale quantum computers progress, the application of quantum algorithms across diverse fields like simulating physical systems, chemistry, optimization, and cryptography becomes more prevalent. However, these quantum computers, known as Noisy Intermediate Scale Quantum (NISQ), are susceptible to noise, prompting the search for applications that can capitalize on quantum advantage without extensive error correction procedures. Since, Machine Learning (ML), particularly Deep Learning (DL), faces challenges due to resource-intensive training and algorithmic opacity. Therefore, this study explores the intersection of quantum computing and ML, focusing on computer vision tasks. Specifically, it evaluates the effectiveness of hybrid quantum-classical algorithms, such as the data re-uploading scheme and the patch Generative Adversarial Networks (GAN) model, on small-scale quantum devices. Through practical implementation and testing, the study reveals comparable or superior performance of these algorithms compared to classical counterparts, highlighting the potential of leveraging quantum algorithms in ML tasks.
The field of quantum computing is rapidly growing, with near term applications immediately available for use. The application of quantum computing to machine learning (i.e., quantum machine learning) is similarly growing rapidly. The presence of noisy intermediate-scale quantum (NISQ) era computers is further enabling research in the area. Historically, the barrier to entry of quantum computing has been nearly insurmountable for computer science students, or any other students who lack a strong physics background. However, quantum computing and quantum machine learning are becoming increasingly accessible, regardless of background. The goal of this paper is to present and demonstrate that the field is accessible to computer science students and to provide a sample curriculum. This curriculum can be used in a standalone class or as part of another machine learning class, as the authors have done.
As the boundaries of quantum computing continue to expand, its intersection with artificial intelligence (AI) is opening new avenues for computational efficiency, model expressiveness, and problem-solving. One such intersection is the emergence of quantum neural networks (QNNs), which synergize the principles of quantum mechanics with classical machine learning frameworks. The practical realization of QNNs, however, is constrained by today’s noisy intermediate-scale quantum (NISQ) devices, characterized by limited qubit counts, decoherence, and noise. This chapter explores how QNNs can be implemented and trained effectively on near-term hardware. We review current quantum computing technologies, examine the architecture of QNNs, discuss hybrid quantum-classical training strategies, and present a practical case study on digit classification. We also review implementation tools such as Qiskit, PennyLane, and TensorFlow Quantum. The chapter concludes with an outlook on future directions and ongoing challenges in realizing scalable, reliable QNNs.