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Measurements in quantum theory can fail to be jointly measurable. Like entanglement, this incompatibility of measurements is necessary but not sufficient for violating Bell inequalities. The (in)compatibility relations among a set of…

Quantum Physics · Physics 2024-11-21 Shiv Akshar Yadavalli , Nikola Andrejic , Ravi Kunjwal

In this article, we study bipartite quantum steering using a general class of measurement operators known as the generalized equiangular measurement (GEAM). Our approach allows for the construction of steering inequalities that are…

Quantum Physics · Physics 2025-06-10 Adam Rutkowski , Katarzyna Siudzińska

We show that the phenomenon of quantum contextuality can be used to certify lower bounds on the dimension accessed by the measurement devices. To prove this, we derive bounds for different dimensions and scenarios of the simplest…

Quantum Physics · Physics 2014-06-12 Otfried Gühne , Costantino Budroni , Adan Cabello , Matthias Kleinmann , Jan-Åke Larsson

Measurement incompatibility describes two or more quantum measurements whose expected joint outcome on a given system cannot be defined. This purely non-classical phenomenon provides a necessary ingredient in many quantum information tasks…

Quantum Physics · Physics 2020-04-01 Francesco Buscemi , Eric Chitambar , Wenbin Zhou

Characterizing entanglement is central for quantum information science. Special observables which indicate entanglement, so-called entanglement witnesses, are a widely used tool for this task. The construction of these witnesses typically…

Quantum Physics · Physics 2024-09-30 Chengjie Zhang , Sophia Denker , Ali Asadian , Otfried Gühne

We present a method for the experimental measurement of nonclassicality witnesses and demonstrate its application. Our proposal only requires the coherent displacement of the initial state, which can be achieved by overlapping the latter…

Quantum Physics · Physics 2015-06-05 T. Kiesel , W. Vogel

Quantum entanglement is commonly assumed to be a central resource for quantum computing and quantum simulation. Nonetheless, the capability to detect it in many-body systems is severely limited by the absence of sufficiently scalable and…

Quantum Physics · Physics 2022-03-17 Irénée Frérot , Flavio Baccari , Antonio Acín

Quantum coherence is a crucial resource in quantum resource theory. Previous study mainly focused on standard coherence under a complete orthogonal reference basis. The standard coherence has recently been extended to general…

Quantum Physics · Physics 2023-07-18 Yu-Cheng Chen , Jiong Cheng , Wen-Zhao Zhang , Cheng-Jie Zhang

The ability that one system immediately affects another one by using local measurements is regarded as quantum steering, which can be detected by various steering criteria. Recently, Mondal et al. [Phys. Rev. A 98, 052330 (2018)] derived…

Quantum Physics · Physics 2020-07-23 Huan Yang , Zhi-Yong Ding , Xue-Ke Song , Hao Yuan , Dong Wang , Jie Yang , Chang-Jin Zhang , Liu Ye

A major challenge in quantum information is characterizing entanglement, for which entanglement witnesses offer effective means of detecting quantum correlations. We introduce a hybrid quantum-classical framework that learns a nonlinear…

Quantum Physics · Physics 2025-09-09 Mohammad Rezaei Shokou , Hossein Davoodi Yeganeh

The Maximum Mean Discrepancy (MMD) has been the state-of-the-art nonparametric test for tackling the two-sample problem. Its statistic is given by the difference in expectations of the witness function, a real-valued function defined as a…

Machine Learning · Computer Science 2022-02-14 Jonas M. Kübler , Wittawat Jitkrittum , Bernhard Schölkopf , Krikamol Muandet

Many existing genuine multipartite entanglement (GME) witnesses for continuous-variable (CV) quantum systems typically rely on quadrature measurements, which is challenging to implement in platforms where the CV degrees of freedom can be…

Quantum Physics · Physics 2025-10-31 Lin Htoo Zaw , Jiajie Guo , Qiongyi He , Shuheng Liu , Matteo Fadel

We derive a Bell inequality based on a generalized quasiprobability function which is parameterized by one non-positive real value. Two types of known Bell inequalities formulated in terms of the Wigner and Q functions are included as…

Quantum Physics · Physics 2009-08-06 Seung-Woo Lee , Hyunseok Jeong , Dieter Jaksch

The future of quantum communication relies on quantum networks composed by observers sharing multipartite quantum states. The certification of multipartite entanglement will be crucial to the usefulness of these networks. In many real…

Quantum Physics · Physics 2016-02-16 D. Cavalcanti , P. Skrzypczyk , G. H. Aguilar , R. V. Nery , P. H. Souto Ribeiro , S. P. Walborn

We introduce a family of entanglement witnesses for continuous variable systems, which rely on the sole assumption that their dynamics is that of coupled harmonic oscillators at the time of the test. Entanglement is inferred from the…

Quantum Physics · Physics 2024-07-31 Pooja Jayachandran , Lin Htoo Zaw , Valerio Scarani

Generalized quantum measurements identifying non-orthogonal states without ambiguity often play an indispensable role in various quantum applications. For such unambiguous state discrimination scenario, we have a finite probability of…

Quantum Physics · Physics 2021-04-16 Shuro Izumi , Jonas S. Neergaard-Nielsen , Ulrik L. Andersen

The robust estimation of entanglement is key to the validation of implementations of quantum systems. On the one hand, the evaluation of standard entanglement measures, either using quantum tomography or using quantitative entanglement…

Quantum Physics · Physics 2018-12-05 Denis Rosset , Anthony Martin , Ephanielle Verbanis , Charles Ci Wen Lim , Rob Thew

Quantum steering describes the phenomenon that one system can be immediately influenced by another with local measurements. It can be detected by the violation of a powerful and useful steering criterion from general entropic uncertainty…

Quantum Physics · Physics 2020-02-26 Huan Yang , Zhi-Yong Ding , Dong Wang , Hao Yuan , Xue-Ke Song , Jie Yang , Chang-Jin Zhang , Liu Ye

Entanglement detection problem is one of the important problem in quantum information theory. Gurvit showed that this problem is NP complete and thus this may be the possible reason that only one criterion is not sufficient to detect all…

Quantum Physics · Physics 2023-01-25 Shruti Aggarwal , Satyabrata Adhikari

We exploit geometric properties of quantum states of light in optical cavities to carry out quantum non-demolition measurements. We generalize the 'mode invisibility' method to obtain information about the Wigner function of a squeezed…

Quantum Physics · Physics 2014-10-22 Marvellous Onuma-Kalu , Robert B. Mann , Eduardo Martin-Martinez