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Direct fidelity estimation is a protocol that estimates the fidelity between an experimental quantum state and a target pure state. By measuring the expectation values of Pauli operators selected through importance sampling, the method is…

Quantum Physics · Physics 2025-07-09 Júlia Barberà-Rodríguez , Mariana Navarro , Leonardo Zambrano

Fermionic Gaussian unitaries are known to be efficiently learnable and simulatable. In this paper, we present a learning algorithm that learns an $n$-mode circuit containing $t$ parity-preserving non-Gaussian gates. While circuits with $t =…

Quantum Physics · Physics 2025-04-23 Sharoon Austin , Mauro E. S. Morales , Alexey Gorshkov

Extremely large antenna arrays (ELAAs) are widely adopted in mmWave/THz communications to compensate for the severe path loss, wherein the channel estimation remains a significant challenge since the Rayleigh distance of ELAAs stretches to…

Signal Processing · Electrical Eng. & Systems 2026-03-17 Yiming Chen , Hongwei Wang , Lingxiang Li , Zhi Chen

We present a quantum circuit that implements the random dilation superchannel, transforming parallel queries of an unknown quantum channel into the same number of parallel queries of a randomly chosen dilation isometry of the input channel.…

Quantum Physics · Physics 2026-05-19 Satoshi Yoshida , Ryotaro Niwa , Takeru Utsumi , Ryuji Takagi , Mio Murao

We study the super dense coding capacity in the presence of quantum channels with correlated noise. We investigate both the cases of unitary and non-unitary encoding. Pauli channels for arbitrary dimensions are treated explicitly. The super…

Quantum Physics · Physics 2011-10-07 Zahra Shadman , Hermann Kampermann , Chiara Macchiavello , Dagmar Bruß

Incorporating sparsity priors in learning tasks can give rise to simple, and interpretable models for complex high dimensional data. Sparse models have found widespread use in structure discovery, recovering data from corruptions, and a…

Machine Learning · Statistics 2014-03-27 Karthikeyan Natesan Ramamurthy , Aleksandr Y. Aravkin , Jayaraman J. Thiagarajan

We generalize the PAC (probably approximately correct) learning model to the quantum world by generalizing the concepts from classical functions to quantum processes, defining the problem of \emph{PAC learning quantum process}, and study…

Quantum Physics · Physics 2021-05-20 Kai-Min Chung , Han-Hsuan Lin

We propose an efficient algorithm for partitioning Pauli strings into subgroups, which can be simultaneously measured in a single quantum circuit. Our partitioning algorithm drastically reduces the total number of measurements in a…

Quantum Physics · Physics 2022-09-07 Tomochika Kurita , Mikio Morita , Hirotaka Oshima , Shintaro Sato

Efficient measures to determine similarity of quantum states, such as the fidelity metric, have been widely studied. In this paper, we address the problem of defining a similarity measure for quantum operations that can be…

Quantum Physics · Physics 2022-11-23 Yiyou Chen , Hideyuki Miyahara , Louis-S. Bouchard , Vwani Roychowdhury

We consider the problem of $\textit{subgroup testing}$ for a quantum circuit $C$: given access to $C$, determine whether it implements a unitary that is $a$-close or $b$-far from a subgroup $\mathcal{G}$ of the unitary group. It encompasses…

Quantum Physics · Physics 2022-11-23 Zvika Brakerski , Devika Sharma , Guy Weissenberg

Stochastic channels are ubiquitous in the field of quantum information because they are simple and easy to analyze. In particular, Pauli channels and depolarizing channels are widely studied because they can be efficiently simulated in many…

Quantum Physics · Physics 2022-01-19 Matthew A. Graydon , Joshua Skanes-Norman , Joel J. Wallman

In this work, we propose a robust approach to design distributed controllers for unknown-but-sparse linear and time-invariant systems. By leveraging modern techniques in distributed controller synthesis and structured linear inverse…

Optimization and Control · Mathematics 2019-10-14 Salar Fattahi , Nikolai Matni , Somayeh Sojoudi

We give a highly efficient "semi-agnostic" algorithm for learning univariate probability distributions that are well approximated by piecewise polynomial density functions. Let $p$ be an arbitrary distribution over an interval $I$ which is…

Machine Learning · Computer Science 2013-05-15 Siu-On Chan , Ilias Diakonikolas , Rocco A. Servedio , Xiaorui Sun

We study the problem of {\em properly} learning large margin halfspaces in the agnostic PAC model. In more detail, we study the complexity of properly learning $d$-dimensional halfspaces on the unit ball within misclassification error…

Machine Learning · Computer Science 2019-08-30 Ilias Diakonikolas , Daniel M. Kane , Pasin Manurangsi

Let $V$ be any vector space of multivariate degree-$d$ homogeneous polynomials with co-dimension at most $k$, and $S$ be the set of points where all polynomials in $V$ {\em nearly} vanish. We establish a qualitatively optimal upper bound on…

Machine Learning · Computer Science 2020-12-15 Ilias Diakonikolas , Daniel M. Kane

Consider a regression problem where the learner is given a large collection of $d$-dimensional data points, but can only query a small subset of the real-valued labels. How many queries are needed to obtain a $1+\epsilon$ relative error…

Machine Learning · Computer Science 2021-06-29 Xue Chen , Michał Dereziński

It is well known that $\ell_1$ minimization can be used to recover sufficiently sparse unknown signals from compressed linear measurements. In fact, exact thresholds on the sparsity, as a function of the ratio between the system dimensions,…

Information Theory · Computer Science 2010-04-06 M. Amin Khajehnejad , Weiyu Xu , Salman Avestimehr , Babak Hassibi

The unitary coupled cluster (UCC) approximation is one of the more promising wave-function ans\"atze for electronic structure calculations on quantum computers via the variational quantum eigensolver algorithm. However, for large systems…

Quantum Physics · Physics 2021-09-30 Jia Chen , Hai-Ping Cheng , James K. Freericks

Accurate characterization of quantum noise, exemplified by the Pauli channel, is a cornerstone for building fault-tolerant quantum computers. A recent protocol (PRX Quantum 6, 020323 (2025)) combining channel concatenation and quantum…

Quantum Physics · Physics 2025-09-10 Yuan-Zhuo Wang , Yi-Ran Xiao , Ming-Yang Li , Shengjun Wu , Zeng-Bing Chen

A common practice in metric learning is to train and test an embedding model for each dataset. This dataset-specific approach fails to simulate real-world scenarios that involve multiple heterogeneous distributions of data. In this regard,…

Computer Vision and Pattern Recognition · Computer Science 2025-01-22 Sungyeon Kim , Donghyun Kim , Suha Kwak