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Shadow tomography aims to build a classical description of a quantum state from a sequence of simple random measurements. Physical observables are then reconstructed from the resulting classical shadow. Shadow protocols which use…

Quantum Physics · Physics 2024-08-14 Sumner N. Hearth , Michael O. Flynn , Anushya Chandran , Chris R. Laumann

We introduce and investigate a data access model (approximate sample and query) that is satisfiable by the preparation and measurement of block encoded states, as well as in contexts such as classical quantum circuit simulation or Pauli…

Quantum Physics · Physics 2026-03-18 Miguel Murça , Paul K. Faehrmann , Yasser Omar

Entanglement plays a fundamental role in quantum physics and information processing. Here, we develop an unbiased estimator for mixed-state entanglement in the few-shot scenario and directly estimate it using random unitary evolution in a…

Quantum Physics · Physics 2024-07-09 Gong-Chu Li , Lei Chen , Si-Qi Zhang , Xu-Song Hong , You Zhou , Geng Chen , Chuan-Feng Li , Guang-Can Guo

Given many copies of an unknown quantum state $\rho$, we consider the task of learning a classical description of its principal eigenstate. Namely, assuming that $\rho$ has an eigenstate $|\phi\rangle$ with (unknown) eigenvalue $\lambda >…

Quantum Physics · Physics 2024-07-09 Daniel Grier , Hakop Pashayan , Luke Schaeffer

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…

Randomized algorithms are crucial subroutines in quantum computing, but the requirement to execute many types of circuits on a real quantum device has been challenging to their extensive implementation. In this study, we propose an…

Quantum Physics · Physics 2026-04-23 Shu Kanno , Ikko Hamamura , Rudy Raymond , Qi Gao , Naoki Yamamoto

Efficiently estimating properties of large and strongly coupled quantum systems is a central focus in many-body physics and quantum information theory. While quantum computers promise speedups for many such tasks, near-term devices are…

Quantum Physics · Physics 2021-09-28 Senrui Chen , Wenjun Yu , Pei Zeng , Steven T. Flammia

We study measurements of the unitary generalization of Pauli operators. First, an analytical (constructive) solution to the eigenproblem of these operators is presented. Next, in the case of two subsystems, the Schmidt form of the…

Quantum Physics · Physics 2009-11-13 Tomasz Paterek

We present here a classical optics device based on an imaging architecture as analogy of a quantum system where the violation of the Bell inequality can be evidenced. In our case, the two qbits entangled state needed to obtain non classical…

Quantum Physics · Physics 2009-04-22 M. Goldin , D. Francisco , S. Ledesma

Shadow tomography is a scalable technique to characterise the quantum state of a quantum computer or quantum simulator. The protocol is based on the transformation of the outcomes of random measurements into the so-called classical shadows,…

Quantum Physics · Physics 2023-10-27 Hai-Chau Nguyen

We show that weakly entangled states can improve communication over a qubit channel using only separate, interference-free, measurements of individual photons. We introduce a communication task corresponding to the cryptographic primitive…

A quantum key distribution and identification protocol is proposed, which is based on entanglement swapping. Through choosing particles by twos from the sequence and performing Bell measurements, two communicators can detect eavesdropping,…

Quantum Physics · Physics 2007-05-23 Fei Gao , Fenzhuo Guo , Qiaoyan Wen , Fuchen Zhu

Dense coding is the seminal example of how entanglement can boost qubit communication, from sending one bit to sending two bits. This is made possible by projecting separate particles onto a maximally entangled basis. We investigate more…

The performance of quantum classifiers is typically analyzed through global state distinguishability or the trainability of variational models. This study investigates how much class information remains accessible under locality-constrained…

Quantum Physics · Physics 2026-02-17 Ait Haddou Marwan

We propose a new quantum computing formalism named Pauli quantum computing. In this formalism, we use the Pauli basis $I$ and $X$ on the non-diagonal blocks of density matrices to encode information and treat them as the computational basis…

Quantum Physics · Physics 2024-12-05 Zhong-Xia Shang

Simulating noiseless quantum dynamics classically faces a fundamental dilemma: tensor-network methods become inefficient as entanglement saturates, while Pauli-truncation approaches typically rely on noise or randomness. To close the gap,…

Quantum Physics · Physics 2026-01-23 Jue Xu , Chu Zhao , Xiangran Zhang , Shuchen Zhu , Qi Zhao

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

We introduce a new classical simulation algorithm based on non-signaling polytopes of multipartite Bell scenarios, capable of simulating universal measurement-based quantum computation with single-qubit Pauli measurements. In our model, the…

Quantum Physics · Physics 2024-11-01 Cihan Okay , Atak Talay Yucel , Selman Ipek

In this letter, we propose a method of dark count correction in quantum state tomography of entangled photon pairs. The framework is based on a linear model of dark counts, which is imposed on the measurement formalism. The method is tested…

Quantum Physics · Physics 2022-09-21 Artur Czerwinski

The Pauli measurements (the measurements that can be performed with Clifford operators followed by measurement in the computational basis) are a fundamental object in quantum information. It is well-known that there is no assignment of…

Quantum Physics · Physics 2023-11-16 Leon Bankston
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