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We study quantum algorithms for testing bipartiteness and expansion of bounded-degree graphs. We give quantum algorithms that solve these problems in time O(N^(1/3)), beating the Omega(sqrt(N)) classical lower bound. For testing expansion,…

Quantum Physics · Physics 2011-09-12 Andris Ambainis , Andrew M. Childs , Yi-Kai Liu

So-called direct measurements of entanglement are collective measurements on multiple copies of a (bipartite or multipartite) quantum system that directly provide one a value for some entanglement measure, such as the concurrence for…

Quantum Physics · Physics 2009-08-03 S. J. van Enk

We establish a general method for proving bounds on the information that can be extracted via arbitrary entangled measurements on tensor products of hidden subgroup coset states. When applied to the symmetric group, the method yields an…

Quantum Physics · Physics 2007-05-23 Cristopher Moore , Alexander Russell

Multiparticle entanglement is a valuable resource for quantum technologies, including measurement based quantum computing, quantum secret sharing, and a variety of quantum sensing applications. The direct way to detect this resource is to…

Quantum Physics · Physics 2025-10-28 Dian Wu , Fei Shi , Jia-Cheng Sun , Bo-Wen Wang , Xue-Mei Gu , Giulio Chiribella , Qi Zhao , Jian Wu

Efficient verification of multipartite quantum states is crucial to many applications in quantum information processing. By virtue of Schmidt decomposition and mutually unbiased bases, here we propose a universal protocol to verify…

Quantum Physics · Physics 2026-03-04 Yunting Li , Huangjun Zhu

We present conditions every measure of entanglement has to satisfy and construct a whole class of 'good' entanglement measures. The generalization of our class of entanglement measures to more than two particles is straightforward. We…

Quantum Physics · Physics 2009-01-23 V. Vedral , M. B. Plenio , M. A. Rippin , P. L. Knight

Experimental tests of Bell's inequality allow to distinguish quantum mechanics from local hidden variable theories. Such tests are performed by measuring correlations of two entangled particles (e.g. polarization of photons or spins of…

While the scaling of entanglement in a quantum system can be used to distinguish many-body quantum phases, it is usually hard to quantify the amount of entanglement in mixed states of open quantum systems, while measuring entanglement…

Statistical Mechanics · Physics 2019-06-04 Katarzyna Macieszczak , Emanuele Levi , Tommaso Macrì , Igor Lesanovsky , Juan P. Garrahan

Quantum state tomography is the problem of estimating a given quantum state. Usually, it is required to run the quantum experiment - state preparation, state evolution, measurement - several times to be able to estimate the output quantum…

General Physics · Physics 2025-04-30 Shibdas Roy , Filippo Caruso , Srushti Patil , Anumita Mukhopadhyay

The question whether global entanglement of a multiparticle quantum system can be inferred from local properties is of great relevance for the theory of quantum correlations as well as for experimental implementations. We present a method…

Quantum Physics · Physics 2016-03-02 Nikolai Miklin , Tobias Moroder , Otfried Gühne

We present a generalization of quantum Stein's Lemma to the situation in which the alternative hypothesis is formed by a family of states, which can moreover be non-i.i.d.. We consider sets of states which satisfy a few natural properties,…

Quantum Physics · Physics 2010-03-10 Fernando G. S. L. Brandao , Martin B. Plenio

In this work we construct tests that allow a classical user to certify high dimensional entanglement in uncharacterized and possibly noisy quantum devices. We present a family of non-local games $\{G_n\}$ that for all $n$ certify states…

Quantum Physics · Physics 2025-06-09 Rotem Arnon , Henry Yuen

Motivated by the Kronecker product approximation technique, we have developed a very simple method to assess the inseparability of bipartite quantum systems, which is based on a realigned matrix constructed from the density matrix. For any…

Quantum Physics · Physics 2007-05-23 Kai Chen , Ling-An Wu

The geometric measure of entanglement of a pure state, defined by its distance to the set of pure separable states, is extended to multipartite mixed states. We characterize the nearest disentangled mixed state to a given mixed state with…

Quantum Physics · Physics 2015-03-13 Shenglong Hu , Liqun Qi , Yisheng Song , Guofeng Zhang

Negativity is regarded as an important measure of entanglement in quantum information theory. In contrast to other measures of entanglement, it is easily computable for bipartite states in arbitrary dimensions. In this paper, based on the…

Quantum Physics · Physics 2010-04-30 Yong-Cheng Ou , Mark S. Byrd

Experimental determination of entanglement is important not only to characterize the state and use it in quantum information, but also in understanding complicated phenomena such as phase transitions. In this paper we show that in many…

Quantum Physics · Physics 2016-01-20 Gaurav Chaudhary , V. Ravishankar

Entanglement in bipartite systems has been applied for the generation of secure random numbers, which are playing an important role in cryptography or scientific numerical simulations. Here, we propose to use multipartite entanglement…

Quantum Physics · Physics 2024-02-23 Yi Li , Yu Xiang , Xiao-Dong Yu , H. Chau Nguyen , Otfried Gühne , Qiongyi He

Nonlocality without entanglement and its subsequent generalizations offer deep information-theoretic insights and subsequently find several useful applications. Concept of genuinely nonlocal set of product states emerges as a natural…

Quantum Physics · Physics 2023-03-31 Sumit Rout , Ananda G. Maity , Amit Mukherjee , Saronath Halder , Manik Banik

We introduce the problem of *shadow tomography*: given an unknown $D$-dimensional quantum mixed state $\rho$, as well as known two-outcome measurements $E_{1},\ldots,E_{M}$, estimate the probability that $E_{i}$ accepts $\rho$, to within…

Quantum Physics · Physics 2018-11-14 Scott Aaronson

We study the separability of symmetric bipartite quantum states and show that a single correlation measurement is sufficient to detect the entanglement of any bipartite symmetric state with a non-positive partial transpose. We also discuss…

Quantum Physics · Physics 2010-02-24 Geza Toth , Otfried Gühne