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The Fast Fourier Transform is extended to functions on finite graphs whose edges are identified with intervals of finite length. Spectral and pseudospectral methods are developed to solve a wide variety of time dependent partial…

Numerical Analysis · Mathematics 2025-07-11 Robert Carlson

Quantum Fisher Information (QFI) is a fundamental quantity in quantum parameter estimation theory, characterizing the ultimate precision bound of parameter estimation. In this work, we investigate QFI for quantum states in non-Hermitian…

Quantum Physics · Physics 2025-05-27 L. H. Wei , H. J. Xing , L. B. Fu , H. D. Liu

We propose spectral methods for long-term forecasting of temporal signals stemming from linear and nonlinear quasi-periodic dynamical systems. For linear signals, we introduce an algorithm with similarities to the Fourier transform but…

Machine Learning · Computer Science 2020-04-02 Henning Lange , Steven L. Brunton , Nathan Kutz

Quantile Factor Models (QFM) represent a new class of factor models for high-dimensional panel data. Unlike Approximate Factor Models (AFM), where only location-shifting factors can be extracted, QFM also allow to recover unobserved factors…

Econometrics · Economics 2020-09-24 Liang Chen , Juan Jose Dolado , Jesus Gonzalo

A novel approach towards the spectral analysis of stationary random bivariate signals is proposed. Using the Quaternion Fourier Transform, we introduce a quaternion-valued spectral representation of random bivariate signals seen as…

Methodology · Statistics 2017-11-22 Julien Flamant , Nicolas Le Bihan , Pierre Chainais

This paper introduces a quantum-inspired denoising framework that integrates the Quantum Fourier Transform (QFT) into classical audio enhancement pipelines. Unlike conventional Fast Fourier Transform (FFT) based methods, QFT provides a…

Sound · Computer Science 2025-09-08 Rajeshwar Tripathi , Sahil Tomar , Sandeep Kumar , Monika Aggarwal

A method for estimating the spectral gap along with higher eigenvalues of nonequilateral quantum graphs has been introduced by Amini and Cohen-Steiner recently: it is based on a new transference principle between discrete and continuous…

Functional Analysis · Mathematics 2020-12-11 Delio Mugnolo , Marvin Plümer

Quantifying predictive uncertainty is essential for safe and trustworthy real-world AI deployment. Yet, fully nonparametric estimation of conditional distributions remains challenging for multivariate targets. We propose Tomographic…

Machine Learning · Computer Science 2026-04-06 Takuya Kanazawa

A new technique for nonparametric regression of multichannel signals is presented. The technique is based on the use of the Rational-Dilation Wavelet Transform (RADWT), equipped with a tunable Q-factor able to provide sparse representations…

Methodology · Statistics 2019-07-26 Daniela De Canditiis , Italia De Feis

The nonlinear Fourier transform has the potential to overcome limits on performance and achievable data rates which arise in modern optical fiber communication systems when nonlinear interference is treated as noise. The periodic nonlinear…

Signal Processing · Electrical Eng. & Systems 2020-12-24 Jan-Willem Goossens , Hartmut Hafermann , Yves Jaouën

The Quantum Fourier transform (QFT) is a key ingredient in most quantum algorithms. We have compared various spin-based quantum computing schemes to implement the QFT from the point of view of their actual time-costs and the accuracy of the…

Quantum Physics · Physics 2014-08-07 Kavita Dorai , Dieter Suter

Quantile regression (QR) is becoming increasingly popular due to its relevance in many scientific investigations. There is a great amount of work about linear and nonlinear QR models. Specifically, nonparametric estimation of the…

Methodology · Statistics 2020-01-13 Eliana Christou

Attosecond nonlinear Fourier transform (NFT) pump probe spectroscopy is an experimental technique which allows investigation of the electronic excitation, ionization, and unimolecular dissociation processes. The NFT spectroscopy utilizes…

Chemical Physics · Physics 2021-02-11 Sergy Grebenshchikov , Sergio Carbajo

In this paper we show how to use Fourier transform methods to analyze the asymptotic behavior of kernel distribution function estimators. Exact expressions for the mean integrated squared error in terms of the characteristic function of the…

Statistics Theory · Mathematics 2013-10-17 José E. Chacón , Pablo Monfort , Carlos Tenreiro

Quantum Phase Estimation (QPE) stands as a pivotal quantum computing subroutine that necessitates an inverse Quantum Fourier Transform (QFT). However, it is imperative to recognize that enhancing the precision of the estimation inevitably…

Quantum Physics · Physics 2023-11-09 Chen-Yu Liu , Chu-Hsuan Abraham Lin , Kuan-Cheng Chen

In non-stationary signal processing, prior work has incorporated the quadratic-phase Fourier transform (QPFT) into the ambiguity function (AF) and Wigner distribution (WD) to enhance their performance. This paper introduces an advanced…

Functional Analysis · Mathematics 2025-03-21 Aamir H. Dar , Neeraj Kumar Sharma

This study introduces and evaluates the Quantile Regressor Tree (QRT), a novel methodology merging the robust characteristics of quantile regression with the versatility of decision trees. The quantile regressor tree introduces…

Applications · Statistics 2024-07-30 Jaachinma Okafor , Lateefah Isegen , Ark Ifeanyi

In this paper, an algorithm for Quantum Inverse Fast Fourier Transform (QIFFT) is developed to work for quantum data. Analogous to a classical discrete signal, a quantum signal can be represented in Dirac notation, application of QIFFT is a…

Quantum Physics · Physics 2024-09-13 Mayank Roy , Devi Maheswaran

In this paper, we propose a nonlinear interferometer with feedback loops and explore its efficiency for phase estimation. We analyse two feedback schemes, one where both modes of the interferometer are fed-back into the device and another…

Quantum Physics · Physics 2025-07-24 Shivani Singh , Craig S. Hamilton , Igor Jex

Sensing with undetected photons has enabled new, unconventional approaches to Fourier transform infrared (FTIR) spectroscopy. Leveraging properties of non-degenerated entangled photon pairs, mid-IR information can be accessed in the near-IR…