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We propose a set of linear quantum entanglement witnesses constituted by local quantum-mechanical observables with each two possible measurement outcomes. These witnesses detect all the entangled resources which give rise to a better…

Quantum Physics · Physics 2012-05-04 Ming-Jing Zhao , Shao-Ming Fei , Xianqing Li-Jost

The characterization of a quantum system can be complicated by non-ideal measurement processes. In many systems, the underlying physical measurement is only sensitive to a single fixed state, complementary outcomes are inferred by…

Quantum Physics · Physics 2014-12-24 Kaila C. S. Hall , Daniel K. L. Oi

When observations must come from incompatible devices and cannot be produced by compatible devices? This question motivates two integer valued quantifications of incompatibility, called incompatibility dimension and compatibility dimension.…

Quantum Physics · Physics 2021-12-02 Teiko Heinosaari , Takayuki Miyadera , Ryo Takakura

We introduce an experimentally accessible method to measure a unique degree of nonclassicality, based on the quantum superposition principle, for arbitrary quantum states. We formulate witnesses and test a given state for any particular…

Quantum Physics · Physics 2014-09-19 M. Mraz , J. Sperling , W. Vogel , B. Hage

Why we do not see large macroscopic objects in entangled states? There are two ways to approach this question. The first is dynamic: the coupling of a large object to its environment cause any entanglement to decrease considerably. The…

Quantum Physics · Physics 2009-11-10 Itamar Pitowsky

We derive exceedingly simple practical procedures revealing the quantum nature of states and measurements by the violation of classical upper bounds on the statistics of arbitrary measurements. Data analysis is minimum and definite…

Quantum Physics · Physics 2009-04-28 Ángel Rivas , Alfredo Luis

A recently proposed test of quantumness [R. Alicki and N. Van Ryn, J. Phys. A: Math. Theor. 41 062001 (2008)] is put into a broader mathematical and physical perspective. The notion of quantumness witness is introduced, in analogy to…

Quantum Physics · Physics 2008-11-21 Robert Alicki , Marco Piani , Nicholas Van Ryn

Quantum mechanics, devoid of any additional assumption, does not give any theoretical constraint on the projection basis to be used for the measurement process. It is shown in this paper that it does neither allow any physical means for an…

General Physics · Physics 2018-01-17 Hitoshi Inamori

We address the question of how much entanglement can be certified from the observed correlations and the knowledge of the Hilbert space dimension of the measured systems. We focus on the case in which both systems are known to be qubits.…

Quantum Physics · Physics 2016-04-27 Koon Tong Goh , Jean-Daniel Bancal , Valerio Scarani

High-dimensional quantum steering can be seen as a test for the dimensionality of entanglement, where the devices at one side are not characterized. As such, it is an important component in quantum informational protocols that make use of…

Quantum Physics · Physics 2023-10-30 Carlos de Gois , Martin Plávala , René Schwonnek , Otfried Gühne

Quantum superposition of high-dimensional states enables both computational speed-up and security in cryptographic protocols. However, the exponential complexity of tomographic processes makes certification of these properties a challenging…

Certifying high-dimensional quantum channels is essential for ensuring the reliability of quantum communication protocols. Existing certification schemes often rely on fully trusted internal devices, which is difficult to achieve in…

Quantum Physics · Physics 2026-02-10 Mengyan Li , Yanning Jia , Fenzhuo Guo , Haifeng Dong , Sujuan Qin , Fei Gao

We introduce a new entanglement measure based on optimal entanglement witness. First of all, we show that the entanglement measure satisfies some necessary properties, including zero entanglements for all separable states, convexity,…

Quantum Physics · Physics 2024-02-20 Nan Yang , Jiaji Wu , Xianyun Dong , Longyu Xiao , Jing Wang , Ming Li

We establish a lower bound on the quantum coherence of an arbitrary quantum state in arbitrary dimension, using a noncommutativity estimator of an arbitrary observable of sub-unit norm, where the estimator is the commutator of the…

Quantum Physics · Physics 2022-06-22 Tanaya Ray , Ahana Ghoshal , Arun Kumar Pati , Ujjwal Sen

This work analyzes correlations arising from quantum systems subject to sequential projective measurements to certify that the system in question has a quantum dimension greater than some $d$. We refine previous known methods and show that…

Quantum Physics · Physics 2021-06-16 Adel Sohbi , Damian Markham , Jaewan Kim , Marco Túlio Quintino

We apply the generalised concept of witness operators to arbitrary convex sets, and review the criteria for the optimisation of these general witnesses. We then define an embedding of state vectors and operators into a higher-dimensional…

Quantum Physics · Physics 2007-05-23 Florian Hulpke , Dagmar Bruss , Maciej Lewenstein , Anna Sanpera

From a quantum information perspective, verifying quantum coherence in a quantum experiment typically requires adjusting measurement settings or changing inputs. A paradigmatic example is that of a double-slit experiment, where observing…

Quantum Physics · Physics 2025-04-01 Fatemeh Bibak , Flavio Del Santo , Borivoje Dakić

We discuss the uniqueness of quantum states compatible with given results for measuring a set of observables. For a given pure state, we consider two different types of uniqueness: (1) no other pure state is compatible with the same…

By testing the classical correlation violation between two systems, the random number can be expanded and certified without applying classical statistical method. In this work, we propose a new random number expansion protocol without…

Quantum Physics · Physics 2011-12-21 Hong-Wei Li , Zhen-Qiang Yin , Yu-Chun Wu , Xu-Bo Zou , Shuang Wang , Wei Chen , Guang-Can Guo , Zheng-Fu Han

Having common reference frames or aligned coordinate systems, is one of the presumptions in witnessing entanglement in a two-party state possessed by two remote parties. This assumption may fail for many reasons. With an unlimited supply of…

Quantum Physics · Physics 2024-05-31 Vahid Jannessary , Fatemeh Rezazadeh , Sadegh Raeisi , Vahid Karimipour