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We propose a generative quantum learning algorithm, R\'enyi-ADAPT, using the Adaptive Derivative-Assembled Problem Tailored ansatz (ADAPT) framework in which the loss function to be minimized is the maximal quantum R\'enyi divergence of…

Quantum Physics · Physics 2025-01-30 Kyle Sherbert , Jim Furches , Karunya Shirali , Sophia E. Economou , Carlos Ortiz Marrero

We consider the learnability of the quantum neural network (QNN) built on the variational hybrid quantum-classical scheme, which remains largely unknown due to the non-convex optimization landscape, the measurement error, and the…

Quantum Physics · Physics 2020-07-27 Yuxuan Du , Min-Hsiu Hsieh , Tongliang Liu , Shan You , Dacheng Tao

Parameterized quantum circuits (PQCs) are fundamental to quantum machine learning (QML), quantum optimization, and variational quantum algorithms (VQAs). The expressibility of PQCs is a measure that determines their capability to harness…

In this article, we present a hybrid quantum-classical generative adversarial network (GAN) for near-term quantum processors. The hybrid GAN comprises a generator and a discriminator quantum neural network (QNN). The generator network is…

Quantum Physics · Physics 2023-07-19 Albha O'Dwyer Boyle , Reza Nikandish

The Quantum Alternating Operator Ansatz (QAOA) is a prominent variational quantum algorithm for solving combinatorial optimization problems. Its effectiveness depends on identifying input parameters that yield high-quality solutions.…

Quantum Physics · Physics 2024-10-10 Joel Rajakumar , John Golden , Andreas Bärtschi , Stephan Eidenbenz

Within the context of hybrid quantum-classical optimization, gradient descent based optimizers typically require the evaluation of expectation values with respect to the outcome of parameterized quantum circuits. In this work, we explore…

In the training of over-parameterized model functions via gradient descent, sometimes the parameters do not change significantly and remain close to their initial values. This phenomenon is called lazy training, and motivates consideration…

Quantum Physics · Physics 2023-05-03 Erfan Abedi , Salman Beigi , Leila Taghavi

Quantum computing (QC) promises theoretical advantages, benefiting computational problems that would not be efficiently classically simulatable. However, much of this theoretical speedup depends on the quantum circuit design solving the…

Machine learning algorithms, both in their classical and quantum versions, heavily rely on optimization algorithms based on gradients, such as gradient descent and alike. The overall performance is dependent on the appearance of local…

Quantum Physics · Physics 2024-04-26 Pablo Bermejo , Borja Aizpurua , Roman Orus

Hybrid Quantum Neural Networks (HQNNs) combine classical learning with parameterized quantum circuits, but their practical performance is often limited by (i) the noise of Noisy Intermediate-Scale Quantum (NISQ) devices and (ii) the large,…

Quantum Physics · Physics 2026-04-17 Tasnim Ahmed , Alberto Marchisio , Muhammad Kashif , Nouhaila Innan , Muhammad Shafique

Optimizing parameterized quantum circuits (PQCs) is the leading approach to make use of near-term quantum computers. However, very little is known about the cost function landscape for PQCs, which hinders progress towards quantum-aware…

Quantum Physics · Physics 2022-08-26 Andrew Arrasmith , Zoë Holmes , M. Cerezo , Patrick J. Coles

In the era of noisy intermediate-scale quantum (NISQ), variational quantum circuits (VQCs) have been widely applied in various domains, demonstrating the potential advantages of quantum circuits over classical models. Similar to classic…

Quantum Physics · Physics 2025-08-26 Jun Zhuang , Jack Cunningham , Chaowen Guan

Gradient estimation is a central challenge in training parameterized quantum circuits (PQCs) for hybrid quantum-classical optimization and learning problems. This difficulty arises from several factors, including the exponential…

Quantum Physics · Physics 2026-05-25 Mohsen Heidari , Masih Mozakka , Wojciech Szpankowski

Variational quantum algorithms that are used for quantum machine learning rely on the ability to automatically differentiate parametrized quantum circuits with respect to underlying parameters. Here, we propose the rules for differentiating…

Quantum Physics · Physics 2021-11-16 Oleksandr Kyriienko , Vincent E. Elfving

An important application for near-term quantum computing lies in optimization tasks, with applications ranging from quantum chemistry and drug discovery to machine learning. In many settings --- most prominently in so-called parametrized or…

Quantum Physics · Physics 2019-03-27 Maria Schuld , Ville Bergholm , Christian Gogolin , Josh Izaac , Nathan Killoran

Variational quantum algorithms (VQAs) combine the advantages of classical optimization and quantum computation, making them one of the most promising approaches in the Noisy Intermediate-Scale Quantum (NISQ) era. However, when optimized…

Quantum Physics · Physics 2025-11-20 Zhehao Yi , Rahul Bhadani

Quantum computers can efficiently sample from probability distributions that are believed to be classically intractable, providing a foundation for quantum generative modeling. However, practical training of such models remains challenging,…

Quantum Physics · Physics 2025-11-18 Maria Demidik , Cenk Tüysüz , Michele Grossi , Karl Jansen

The loss landscape of Variational Quantum Neural Networks (VQNNs) is characterized by local minima that grow exponentially with increasing qubits. Because of this, it is more challenging to recover information from model gradients during…

Machine Learning · Computer Science 2025-05-08 Georgios Papadopoulos , Shaltiel Eloul , Yash Satsangi , Jamie Heredge , Niraj Kumar , Chun-Fu Chen , Marco Pistoia

Variational quantum circuits are used in quantum machine learning and variational quantum simulation tasks. Designing good variational circuits or predicting how well they perform for given learning or optimization tasks is still unclear.…

Quantum Physics · Physics 2022-08-18 Junyu Liu , Francesco Tacchino , Jennifer R. Glick , Liang Jiang , Antonio Mezzacapo

Variational quantum algorithms are expected to demonstrate the advantage of quantum computing on near-term noisy quantum computers. However, training such variational quantum algorithms suffers from gradient vanishing as the size of the…

Quantum Physics · Physics 2021-11-29 Anbang Wu , Gushu Li , Yufei Ding , Yuan Xie