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Quantum machine learning (QML) has become a promising area for real world applications of quantum computers, but near-term methods and their scalability are still important research topics. In this context, we analyze the trainability and…

Quantum Physics · Physics 2025-05-21 Léo Monbroussou , Eliott Z. Mamon , Jonas Landman , Alex B. Grilo , Romain Kukla , Elham Kashefi

Generative modeling is a flavor of machine learning with applications ranging from computer vision to chemical design. It is expected to be one of the techniques most suited to take advantage of the additional resources provided by…

A highly anticipated use of quantum computers is the simulation of complex quantum systems including molecules and other many-body systems. One promising method involves directly applying a linear combination of unitaries (LCU) to…

Quantum Physics · Physics 2022-02-02 Richard Meister , Simon C. Benjamin , Earl T. Campbell

Parametrized Quantum Circuits (PQCs) enable a novel method for machine learning (ML). However, from a computational point of view they present a challenge to existing eXplainable AI (xAI) methods. On the one hand, measurements on quantum…

Quantum Physics · Physics 2022-11-04 Patrick Steinmüller , Tobias Schulz , Ferdinand Graf , Daniel Herr

Hybrid quantum-classical computing relies heavily on Variational Quantum Algorithms (VQAs) to tackle challenges in diverse fields like quantum chemistry and machine learning. However, VQAs face a critical limitation: the balance between…

Quantum Physics · Physics 2025-03-18 Jeihee Cho , Junyong Lee , Daniel Justice , Shiho Kim

Many experimental proposals for noisy intermediate scale quantum devices involve training a parameterized quantum circuit with a classical optimization loop. Such hybrid quantum-classical algorithms are popular for applications in quantum…

Quantum Physics · Physics 2019-02-04 Jarrod R. McClean , Sergio Boixo , Vadim N. Smelyanskiy , Ryan Babbush , Hartmut Neven

Variational Quantum Circuits (VQC) are promising models for quantum machine learning, but standard monolithic architectures face an expressivity--trainability dilemma: small circuits can be under-parameterized, while larger circuits are…

Quantum Physics · Physics 2026-05-12 Howard Su , Chen-Yu Liu , Samuel Yen-Chi Chen , Kuan-Cheng Chen , Huan-Hsin Tseng

Variational quantum algorithms (VQAs) promise efficient use of near-term quantum computers. However, training VQAs often requires an extensive amount of time and suffers from the barren plateau problem where the magnitude of the gradients…

Quantum Physics · Physics 2021-06-24 Tobias Haug , M. S. Kim

When compared to fault-tolerant quantum computational strategies, variational quantum algorithms stand as one of the candidates with the potential of achieving quantum advantage for real-world applications in the near term. However, the…

Parametrised quantum circuits are a central framework for near term quantum machine learning. However, it remains challenging to determine in advance how architectural choices, such as encoding strategies, gate placement, and entangling…

Quantum Physics · Physics 2026-04-07 Kyle James Stuart Campbell , Luigi Del Debbio , Petros Wallden

In this paper, we study the trainability of rectified linear unit (ReLU) networks. A ReLU neuron is said to be dead if it only outputs a constant for any input. Two death states of neurons are introduced; tentative and permanent death. A…

Machine Learning · Computer Science 2020-10-23 Yeonjong Shin , George Em Karniadakis

With the increased focus on quantum circuit learning for near-term applications on quantum devices, in conjunction with unique challenges presented by cost function landscapes of parametrized quantum circuits, strategies for effective…

Quantum Physics · Physics 2021-09-10 Andrea Skolik , Jarrod R. McClean , Masoud Mohseni , Patrick van der Smagt , Martin Leib

Many applications in quantum simulation, quantum chemistry, and quantum machine learning require not a single quantum state but an ensemble of states characterizing the heterogeneity of a target system. Preparing such ensembles…

Quantum Physics · Physics 2026-05-28 Quoc Hoan Tran , Koki Chinzei , Yasuhiro Endo , Hirotaka Oshima

Instantaneous quantum polynomial quantum circuit Born machines (IQP-QCBMs) have been proposed as quantum generative models with a classically tractable training objective based on the maximum mean discrepancy (MMD) and a potential quantum…

Quantum Physics · Physics 2026-02-16 Kevin Shen , Susanne Pielawa , Vedran Dunjko , Hao Wang

Parametrised quantum circuits contain phase gates whose phase is determined by a classical algorithm prior to running the circuit on a quantum device. Such circuits are used in variational algorithms like QAOA and VQE. In order for these…

Quantum Physics · Physics 2025-08-27 John van de Wetering , Richie Yeung , Tuomas Laakkonen , Aleks Kissinger

The existence of "barren plateau landscapes" for generic discrete variable quantum neural networks, which obstructs efficient gradient-based optimization of cost functions defined by global measurements, would be surprising in the case of…

Quantum Physics · Physics 2021-06-08 T. J. Volkoff

We develop three new methods to implement any Linear Combination of Unitaries (LCU), a powerful quantum algorithmic tool with diverse applications. While the standard LCU procedure requires several ancilla qubits and sophisticated…

Quantum Physics · Physics 2024-10-16 Shantanav Chakraborty

Parameterized quantum circuits have been extensively used as the basis for machine learning models in regression, classification, and generative tasks. For supervised learning, their expressivity has been thoroughly investigated and several…

Quantum Physics · Physics 2026-05-20 Alice Barthe , Michele Grossi , Sofia Vallecorsa , Jordi Tura , Vedran Dunjko

Combining classical optimization with parameterized quantum circuit evaluation, variational quantum algorithms (VQAs) are among the most promising algorithms in near-term quantum computing. Similar to neural networks (NNs), VQAs iteratively…

Quantum Physics · Physics 2025-11-18 Zhehao Yi , Yanying Liang , Haozhen Situ

The training of a parameterized model largely depends on the landscape of the underlying loss function. In particular, vanishing gradients are a central bottleneck in the scalability of variational quantum algorithms (VQAs), and are known…

Quantum Physics · Physics 2024-09-26 Alistair Letcher , Stefan Woerner , Christa Zoufal