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We introduce a general method for the experimental detection of entanglement by performing only few local measurements, assuming some prior knowledge of the density matrix. The idea is based on the minimal decomposition of witness operators…

Quantum Physics · Physics 2009-11-07 O. Guehne , P. Hyllus , D. Bruss , A. Ekert , M. Lewenstein , C. Macchiavello , A. Sanpera

The geometric measure of entanglement, which expresses the minimum distance to product states, has been generalized to distances to sets that remain invariant under the stochastic reducibility relation. For each such set, an associated…

Quantum Physics · Physics 2010-09-20 K. Uyanik , S. Turgut

We have developed Bayesian formalism to describe the process of continuous measurement of entangled qubits. We start with the case of two qubits and then generalize it to an arbitrary number of qubits.

Mesoscale and Nanoscale Physics · Physics 2009-11-07 Alexander N. Korotkov

Entanglement often increases quantum measurement schemes' sensitivity. However, we find that in precision measurements with zero-mean Gaussian states, such as squeezed states, entanglement between different paths degrades measurement…

Quantum Physics · Physics 2025-04-28 Benjamin Lou , Hudson A. Loughlin , Nergis Mavalvala

We propose a qubit-environment entanglement measure which is tailored for evolutions that lead to pure dephasing of the qubit, such as are abundant in solid state scenarios. The measure can be calculated directly form the density matrix…

Quantum Physics · Physics 2020-10-21 Katarzyna Roszak

Bounds analogous to entropic uncertainty relations allow one to design practical tests to detect quantum entanglement by a collective measurement performed on several copies of the state analyzed. This approach, initially worked out for…

Quantum Physics · Physics 2013-01-04 Łukasz Rudnicki , Zbigniew Puchała , Paweł Horodecki , Karol Życzkowski

Entanglement measures quantify nonclassical correlations present in a quantum system, but can be extremely difficult to calculate, even more so, when information on its state is limited. Here, we consider broad families of entanglement…

Quantum Physics · Physics 2021-07-07 Matteo Fadel , Ayaka Usui , Marcus Huber , Nicolai Friis , Giuseppe Vitagliano

The most useful measure of a bipartite entanglement is the von Neumann entropy of either of the reduced density matrices. For a particular class of continuous-variable states, the Gaussian states, the entropy of entanglement can be…

Quantum Physics · Physics 2012-09-14 Tommaso F. Demarie

Based on correlations of coherently displaced photon-numbers, we derive entanglement criteria for the purpose to verify non-Gaussian entanglement. Our construction method enables us to verify bipartite and multipartite entanglement of…

Quantum Physics · Physics 2017-09-08 B. Kühn , W. Vogel , J. Sperling

We examine entanglement between number and polarization, or between number and relative phase, for pairs of coherent states and two-mode squeezed vacuum via linear entropy and covariance criteria. We consider the embedding of the two-mode…

Quantum Physics · Physics 2018-04-11 Carlos Sanchidrián-Vaca , Alfredo Luis

Characterizing and quantifying quantum correlations in states of many-particle systems is at the core of a full understanding of phase transitions in matter. In this work, we continue our investigation of the notion of generalized…

Quantum Physics · Physics 2009-11-10 Rolando Somma , Gerardo Ortiz , Howard Barnum , Emanuel Knill , Lorenza Viola

We propose a measurement-based method to produce a maximally-entangled state from a partially-entangled pure state. Our goal can be thought of as entanglement distillation from a single copy of a partially-entangled state. The present…

Quantum Physics · Physics 2012-10-17 Yukihiro Ota , Sahel Ashhab , Franco Nori

Coherence and entanglement are fundamental properties of quantum systems, promising to power the near future quantum computers, sensors and simulators. Yet, their experimental detection is challenging, usually requiring full reconstruction…

Quantum Physics · Physics 2017-08-01 Graeme Smith , John A. Smolin , Xiao Yuan , Qi Zhao , Davide Girolami , Xiongfeng Ma

Detection of entanglement in quantum states is one of the most important problems in quantum information processing. However, it is one of the most challenging tasks to find a universal scheme which is also desired to be optimal to detect…

Quantum Physics · Physics 2026-03-13 Arijit Dutta , Sibasish Ghosh , Jaewan Kim , Ritabrata Sengupta

Measurement-based entanglement is a method for entangling quantum systems through the state projection that accompanies a parity measurement. We derive a stochastic master equation describing measurement-based entanglement of a pair of…

Quantum Physics · Physics 2024-07-17 Remy L. Delva , Jonas Mielke , Guido Burkard , Jason R. Petta

We propose a method to generate entanglement measures systematically by using the irreducible decomposition of some copies of a state under the local unitary (LU) transformations. It is applicable to general multipartite systems. We show…

Quantum Physics · Physics 2009-11-13 Ayumu Sugita

We show that all entangled Gaussian states of two infinite dimensional systems can be distilled to maximally entangled states in finite dimensions. The distillation protocol involves local squeezing operations, local homodyne measurements…

Quantum Physics · Physics 2007-05-23 Geza Giedke , Lu-Ming Duan , J. Ignacio Cirac , Peter Zoller

We present a multipartite entanglement measure for $N$-qudit pure states, using the norm of the correlation tensor which occurs in the Bloch representation of the state. We compute this measure for important class of $N$-qutrit pure states,…

Quantum Physics · Physics 2010-01-01 Ali Saif M. Hassan , Pramod S. Joag

The quantification and classification of quantum entanglement is a very important and still open question of quantum information theory. In this paper, we describe an entanglement measure for multipartite pure states (the minimum of…

Quantum Physics · Physics 2009-05-05 A. Yu. Chernyavskiy

We show that for tripartite quantum pure states of qubits, all the kinds of entanglement in terms of SLOCC classification are experimentally measurable by simple projective measurements, provided that four copies of the composite quantum…

Quantum Physics · Physics 2009-11-13 Chang-shui Yu , He-shan Song