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Quantum key distribution (QKD) security fundamentally relies on the ability to distinguish genuine quantum correlations from classical eavesdropper simulations, yet existing certification methods lack rigorous statistical guarantees under…

Quantum Physics · Physics 2025-12-04 Davut Emre Tasar , Ceren Ocal Tasar

Quantum algorithms based on the variational principle have found applications in diverse areas with a huge flexibility. But as the circuit size increases the variational landscapes become flattened, causing the so-called Barren plateau…

Quantum Physics · Physics 2025-09-03 Fabio Tarocco , Davide Materia , Leonardo Ratini , Leonardo Guidoni

The design and optimization of realistic architectures for fault-tolerant quantum computation requires error models that are both reliable and amenable to large-scale classical simulation. Perhaps the simplest and most practical…

Quantum Physics · Physics 2015-09-17 Michael R. Geller , Zhongyuan Zhou

Advances in quantum algorithms suggest a tentative scaling advantage on certain combinatorial optimization problems. Recent work, however, has also reinforced the idea that barren plateaus render variational algorithms ineffective on large…

Quantum Physics · Physics 2025-03-14 Tim Bode , Krish Ramesh , Tobias Stollenwerk

Variational quantum algorithms (VQAs) are expected to establish valuable applications on near-term quantum computers. However, recent works have pointed out that the performance of VQAs greatly relies on the expressibility of the ansatzes…

Quantum Physics · Physics 2022-08-15 Xia Liu , Geng Liu , Jiaxin Huang , Hao-Kai Zhang , Xin Wang

Accurately determining resonance frequencies and quality factors (Q) is crucial in accelerator physics and radiofrequency engineering, as these factors have direct impacts on system design, operational stability, and research results. The…

Accelerator Physics · Physics 2025-10-08 Kerem Semiz

The barren plateau phenomenon is one of the main obstacles to implementing variational quantum algorithms in the current generation of quantum processors. Here, we introduce a method capable of avoiding the barren plateau phenomenon in the…

The barren plateau phenomenon, characterized by loss gradients that vanish exponentially with system size, poses a challenge to scaling variational quantum algorithms. Here we explore the potential of warm starts, whereby one initializes…

Quantum Physics · Physics 2025-03-04 Ricard Puig , Marc Drudis , Supanut Thanasilp , Zoë Holmes

The ``fast iterative shrinkage-thresholding algorithm'', a.k.a. FISTA, is one of the most widely used algorithms in the literature. However, despite its optimal theoretical $O(1/k^2)$ convergence rate guarantee, oftentimes in practice its…

Optimization and Control · Mathematics 2018-07-12 Jingwei Liang , Carola-Bibiane Schönlieb

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

Wald's sequential probability ratio test (SPRT) is a cornerstone of sequential analysis. Based on desired type-I, II error levels $\alpha, \beta$, it stops when the likelihood ratio crosses certain thresholds, guaranteeing optimality of the…

Methodology · Statistics 2025-07-09 Lasse Fischer , Aaditya Ramdas

This paper develops a novel algorithm, termed \emph{SPARse Truncated Amplitude flow} (SPARTA), to reconstruct a sparse signal from a small number of magnitude-only measurements. It deals with what is also known as sparse phase retrieval…

Information Theory · Computer Science 2017-10-31 Gang Wang , Liang Zhang , Georgios B. Giannakis , Mehmet Akcakaya , Jie Chen

Variational quantum algorithms are promising candidates for near-term quantum computing but can be hindered by barren plateaus, where gradients vanish exponentially and optimization becomes intractable. Noise-Induced Barren Plateaus (NIBP)…

Quantum Physics · Physics 2026-03-10 Sebastian Schmitt , Linus Ekstrøm , Alberto Bottarelli , Xavier Bonet-Monroig

Variational Quantum Algorithms are a vital part of quantum computing. It is a blend of quantum and classical methods for tackling tough problems in machine learning, chemistry, and combinatorial optimization. Yet as these algorithms scale…

Quantum Physics · Physics 2026-03-19 Francis Boabang , Samuel Asante Gyamerah

Quantum architecture search (QAS) involves optimizing both the quantum parametric circuit configuration but also its parameters for a variational quantum algorithm. Thus, the problem is known to be multi-level as the performance of a given…

Quantum Physics · Physics 2024-07-30 Vicente P. Soloviev , Vedran Dunjko , Concha Bielza , Pedro Larrañaga , Hao Wang

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

Surface codes represent a leading approach for quantum error correction (QEC), offering a path towards universal fault-tolerant quantum computing (FTQC). However, efficiently implementing algorithms, particularly using Pauli-based…

Quantum Physics · Physics 2025-05-02 Shuwen Kan , Zefan Du , Chenxu Liu , Meng Wang , Yufei Ding , Ang Li , Ying Mao , Samuel Stein

We study a first-order primal-dual subgradient method to optimize risk-constrained risk-penalized optimization problems, where risk is modeled via the popular conditional value at risk (CVaR) measure. The algorithm processes independent and…

Optimization and Control · Mathematics 2021-09-03 Avinash N. Madavan , Subhonmesh Bose

Dynamical Lie algebras (DLAs) have emerged as a valuable tool in the study of parameterized quantum circuits, helping to characterize both their expressiveness and trainability. In particular, the absence or presence of barren plateaus…

Quantum Physics · Physics 2026-05-28 Jonathan Allcock , Miklos Santha , Pei Yuan , Shengyu Zhang

Highly accurate and robust control of quantum operations is vital for the realization of error-correctible quantum computation. In this paper, we show that the robustness of high-precision controls can be remarkably enhanced through…

Quantum Physics · Physics 2021-07-28 Xiaozhen Ge , Re-Bing Wu