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We propose a framework to design and optimize generic photonic quantum circuits composed of Gaussian objects (pure and mixed Gaussian states, Gaussian unitaries, Gaussian channels, Gaussian measurements) as well as non-Gaussian effects such…

Quantum Physics · Physics 2024-09-18 Yuan Yao , Filippo Miatto , Nicolás Quesada

The techniques and analysis presented in this paper provide new methods to solve optimization problems posed on Riemannian manifolds. A new point of view is offered for the solution of constrained optimization problems. Some classical…

Optimization and Control · Mathematics 2018-04-12 Steven Thomas Smith

Grover's algorithm is a fundamental quantum algorithm that offers a quadratic speedup for the unstructured search problem by alternately applying physically implementable oracle and diffusion operators. In this paper, we reformulate the…

Quantum Physics · Physics 2025-12-15 Zhijian Lai , Dong An , Jiang Hu , Zaiwen Wen

The performance of quantum neural network models depends strongly on architectural decisions, including circuit depth, placement of parametrized operations, and data-encoding strategies. Selecting an effective architecture is challenging…

Tree tensor networks (TTNs) are widely used in low-rank approximation and quantum many-body simulation. In this work, we present a formal analysis of the differential geometry underlying TTNs. Building on this foundation, we develop…

Optimization and Control · Mathematics 2025-10-07 Marius Willner , Marco Trenti , Dirk Lebiedz

In this work, a scalable algorithm for the approximate quantum state preparation problem is proposed, facing a challenge of fundamental importance in many topic areas of quantum computing. The algorithm uses a variational quantum circuit…

Quantum Physics · Physics 2025-03-19 Giacomo Belli , Marco Mordacci , Michele Amoretti

For a large class of variational quantum circuits, we show how arbitrary-order derivatives can be analytically evaluated in terms of simple parameter-shift rules, i.e., by running the same circuit with different shifts of the parameters. As…

Quantum Physics · Physics 2021-03-03 Andrea Mari , Thomas R. Bromley , Nathan Killoran

Gradient-based optimizers have been proposed for training variational quantum circuits in settings such as quantum neural networks (QNNs). The task of gradient estimation, however, has proven to be challenging, primarily due to distinctive…

Variational quantum algorithms (VQAs) are promising methods to demonstrate quantum advantage on near-term devices as the required resources are divided between a quantum simulator and a classical optimizer. As such, designing a VQA which is…

Quantum Physics · Physics 2022-05-20 Yuhan Huang , Qingyu Li , Xiaokai Hou , Rebing Wu , Man-Hong Yung , Abolfazl Bayat , Xiaoting Wang

With rapid advancements in machine learning, first-order algorithms have emerged as the backbone of modern optimization techniques, owing to their computational efficiency and low memory requirements. Recently, the connection between…

Quantum Physics · Physics 2025-05-21 Jiaqi Leng , Bin Shi

Many optimization methods for training variational quantum algorithms are based on estimating gradients of the cost function. Due to the statistical nature of quantum measurements, this estimation requires many circuit evaluations, which is…

Quantum Physics · Physics 2022-10-14 Lennart Bittel , Jens Watty , Martin Kliesch

Quantum computing promises to provide machine learning with computational advantages. However, noisy intermediate-scale quantum (NISQ) devices pose engineering challenges to realizing quantum machine learning (QML) advantages. Recently, a…

Quantum Physics · Physics 2022-07-22 Rodrigo Araiza Bravo , Khadijeh Najafi , Xun Gao , Susanne F. Yelin

This work focuses on optimizing the gates of a quantum circuit with a given topology to approximate the unitary time evolution governed by a Hamiltonian. Recognizing that unitary matrices form a mathematical manifold, we employ Riemannian…

Quantum Physics · Physics 2025-07-01 Fabian Putterer , Max M. Zumpe , Isabel Nha Minh Le , Qunsheng Huang , Christian B. Mendl

Variational quantum circuits are one of the promising ways to exploit the advantages of quantum computing in the noisy intermediate-scale quantum technology era. The design of the quantum circuit architecture might greatly affect the…

Quantum Physics · Physics 2024-05-14 Gang Wang , Bang-Hai Wang , Shao-Ming Fei

Can near-term gate model based quantum processors offer quantum advantage for practical applications in the pre-fault tolerance noise regime? A class of algorithms which have shown some promise in this regard are the so-called…

Quantum Physics · Physics 2019-08-13 Guillaume Verdon , Michael Broughton , Jacob Biamonte

We propose Riemannian preconditioned algorithms for the tensor completion problem via tensor ring decomposition. A new Riemannian metric is developed on the product space of the mode-2 unfolding matrices of the core tensors in tensor ring…

Optimization and Control · Mathematics 2023-11-15 Bin Gao , Renfeng Peng , Ya-xiang Yuan

This paper exploits a basic connection between sequential quadratic programming and Riemannian gradient optimization to address the general question of selecting a metric in Riemannian optimization, in particular when the Riemannian…

Optimization and Control · Mathematics 2016-03-10 Bamdev Mishra , Rodolphe Sepulchre

Decoherence of quantum hardware is currently limiting its practical applications. At the same time, classical algorithms for simulating quantum circuits have progressed substantially. Here, we demonstrate a hybrid framework that integrates…

We study a type of Riemannian gradient descent (RGD) algorithm, designed through Riemannian preconditioning, for optimization on $\mathcal{M}_k^{m\times n}$ -- the set of $m\times n$ real matrices with a fixed rank $k$. Our analysis is…

Optimization and Control · Mathematics 2024-08-15 Shuyu Dong , Bin Gao , Wen Huang , Kyle A. Gallivan

Variational quantum algorithms (VQAs) are a broad class of algorithms with many applications in science and industry. Applying a VQA to a problem involves optimizing a parameterized quantum circuit by maximizing or minimizing a cost…

Quantum Physics · Physics 2025-06-04 Tianyi Hao , Zichang He , Ruslan Shaydulin , Marco Pistoia , Swamit Tannu