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Measuring global quantum properties-such as the fidelity to complex multipartite states-is both an essential and experimentally challenging task. Classical shadow estimation offers favorable sample complexity, but typically relies on…

Quantum Physics · Physics 2026-02-11 Qingyue Zhang , Dayue Qin , Zhou You , Feng Xu , Jens Eisert , You Zhou

Interfacing quantum and classical processors is an important subroutine in full-stack quantum algorithms. The so-called "classical shadow" method efficiently extracts essential classical information from quantum states, enabling the…

Quantum Physics · Physics 2025-09-11 Shuowei Ma , Junyu Liu

Quantum learning encounters fundamental challenges when estimating non-linear properties, owing to the inherent linearity of quantum mechanics. Although recent advances in single-copy randomized measurement protocols have achieved optimal…

Quantum Physics · Physics 2026-03-30 Zhenyu Du , Yifan Tang , Andreas Elben , Ingo Roth , Jens Eisert , Zhenhuan Liu

Classical shadows (CS) has recently emerged as an important framework to efficiently predict properties of an unknown quantum state. A common strategy in CS protocols is to parametrize the basis in which one measures the state by a random…

Efficient fidelity estimation of multiqubit quantum states is crucial to many applications in quantum information processing. However, to estimate the infidelity $\epsilon$ with multiplicative precision, conventional estimation protocols…

Quantum Physics · Physics 2025-12-01 Zhongyi Yang , Datong Chen , Zihao Li , Huangjun Zhu

Estimating the expectation value of an operator corresponding to an observable is a fundamental task in quantum computation. It is often impossible to obtain such estimates directly, as the computer is restricted to measuring in a fixed…

Improving the performance of quantum algorithms is a fundamental task to achieve quantum advantage. In many cases, extracting information from quantum systems poses an important challenge for practical implementations in real-world quantum…

Quantum Physics · Physics 2025-02-28 Leticia Bertuzzi , João P. Engster , Evandro C. R. da Rosa , Eduardo I. Duzzioni

The rapid advancement of quantum computing has led to an extensive demand for effective techniques to extract classical information from quantum systems, particularly in fields like quantum machine learning and quantum chemistry. However,…

Quantum Physics · Physics 2023-05-09 Yifei Chen , Zhan Yu , Chenghong Zhu , Xin Wang

Measuring the expectation value of Pauli operators on prepared quantum states is a fundamental task in a multitude of quantum algorithms. Simultaneously measuring sets of operators allows for fewer measurements and an overall speedup of the…

Quantum Physics · Physics 2019-07-19 Andrew Jena , Scott Genin , Michele Mosca

Accurately estimating the properties of quantum systems is a central challenge in quantum computing and quantum information. We propose a method to obtain unbiased estimators of multiple observables with low statistical error by…

Quantum Physics · Physics 2025-07-25 Stefano Mangini , Daniel Cavalcanti

We consider the problem of estimating quantum observables on a collection of qubits, given as a linear combination of Pauli operators, with shallow quantum circuits consisting of single-qubit rotations. We introduce estimators based on…

Quantum Physics · Physics 2022-08-08 Stefan Hillmich , Charles Hadfield , Rudy Raymond , Antonio Mezzacapo , Robert Wille

Predicting properties of complex, large-scale quantum systems is essential for developing quantum technologies. We present an efficient method for constructing an approximate classical description of a quantum state using very few…

Quantum Physics · Physics 2021-04-20 Hsin-Yuan Huang , Richard Kueng , John Preskill

Quantum shadow tomography based on the classical shadow representation provides an efficient way to estimate properties of an unknown quantum state without performing a full quantum state tomography. In scenarios where estimating the…

Quantum Physics · Physics 2026-03-13 Aniket Sengupta , Arijit Chatterjee , G. J. Sreejith , T. S. Mahesh

With quantum computing devices increasing in scale and complexity, there is a growing need for tools that obtain precise diagnostic information about quantum operations. However, current quantum devices are only capable of short…

Quantum Physics · Physics 2023-09-01 J. Helsen , M. Ioannou , J. Kitzinger , E. Onorati , A. H. Werner , J. Eisert , I. Roth

Classical shadows provide a versatile framework for estimating many properties of quantum states from repeated, randomly chosen measurements without requiring full quantum state tomography. When prior information is available, such as…

Quantum Physics · Physics 2026-05-27 Jacob Bringewatt , Henry Froland , Andreas Elben , Niklas Mueller

Grouping-based measurement strategies are widely used to reduce measurement complexity in near-term quantum algorithms. While these schemes have typically produced disjoint groups, recently this has been relaxed in what is known as…

Quantum Physics · Physics 2026-04-09 Jeremiah Rowland , Rahul Sarkar , Nicolas PD Sawaya , Norm M. Tubman , Ryan LaRose

Classical shadow tomography provides an efficient method for predicting functions of an unknown quantum state from a few measurements of the state. It relies on a unitary channel that efficiently scrambles the quantum information of the…

Quantum Physics · Physics 2022-02-01 Hong-Ye Hu , Yi-Zhuang You

Extracting classical information from quantum systems is of fundamental importance, and classical shadows allow us to extract a large amount of information using relatively few measurements. Conventional shadow estimators are unbiased and…

Quantum Physics · Physics 2025-04-03 Zhenyu Cai , Adrian Chapman , Hamza Jnane , Bálint Koczor

Randomized measurement protocols such as classical shadows represent powerful resources for quantum technologies, with applications ranging from quantum state characterization and process tomography to machine learning and error mitigation.…

Quantum Physics · Physics 2024-06-18 Laurin E. Fischer , Timothée Dao , Ivano Tavernelli , Francesco Tacchino

Quantum algorithms designed for realistic quantum many-body systems, such as chemistry and materials, usually require a large number of measurements of the Hamiltonian. Exploiting different ideas, such as {importance sampling,} observable…

Quantum Physics · Physics 2023-01-18 Bujiao Wu , Jinzhao Sun , Qi Huang , Xiao Yuan