Unified quantification of nonclassicality and entanglement

Vogel, W.; Sperling, Jan

doi:10.1103/physreva.89.052302

Cited by 168 publications

(179 citation statements)

References 43 publications

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“…For instance, it could be used for the creation of multi-partite entangled states [4] from bi-partite entanglement or for overcoming the transmission loss in establishing entanglement over long-distances via quantum repeaters [5][6][7][8]. Interestingly, the entanglement swapping concept also lends itself to the search for entanglement conserving quantities [9][10][11][12]. In any experimental implementation the generated entangled quantum states are not necessarily perfect and, in fact, could be further degraded by transmission through the communication channels.…”

Section: Introductionmentioning

confidence: 99%

Entanglement swapping of two arbitrarily degraded entangled states

et al. 2016

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We consider entanglement swapping, a key component of quantum network operations and entanglement distribution. Pure entangled states, which are the desired input to the swapping protocol, are typically mixed by environmental interactions causing a reduction in their degree of entanglement. Thus an understanding of entanglement swapping with partially mixed states is of importance. Here we present a general analytical solution for entanglement swapping of arbitrary two-qubit states. Our result provides a comprehensive method for analyzing entanglement swapping in quantum networks. First, we show that the concurrence of a partially mixed state is conserved when this state is swapped with a Bell state. Then, we find upper and lower bounds on the concurrence of the state resulting from entanglement swapping for various classes of input states. Finally, we determine a general relationship between the ranks of the initial states and the rank of the final state after swapping.

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Section: Introductionmentioning

confidence: 99%

Entanglement swapping of two arbitrarily degraded entangled states

et al. 2016

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“…On the other hand, however, quantum correlations in quantum optics lack such a nonlocal operational justification, i.e., there is no particular quantum information protocol which exploits phase-space nonclassicality to outperform a classical counterpart protocol. Although, it has been recently shown that such nonclassicalities provide either necessary or sufficient resources for entanglement generation [11][12][13], which then can be used in various protocols.…”

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confidence: 99%

Quantum Correlations in Nonlocal Boson Sampling

2017

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Determination of the quantum nature of correlations between two spatially separated systems plays a crucial role in quantum information science. Of particular interest is the questions of if and how these correlations enable quantum information protocols to be more powerful. Here, we report on a distributed quantum computation protocol in which the input and output quantum states are considered to be classically correlated in quantum informatics. Nevertheless, we show that the correlations between the outcomes of the measurements on the output state cannot be efficiently simulated using classical algorithms. Crucially, at the same time, local measurement outcomes can be efficiently simulated on classical computers. We show that the only known classicality criterion violated by the input and output states in our protocol is the one used in quantum optics, namely, phase-space nonclassicality. As a result, we argue that the global phase-space nonclassicality inherent within the output state of our protocol represents true quantum correlations.Introduction.-Correlations play an undeniable role in our understanding of the physical world. In our macroscopic classical description of commonplace phenomena, classical physics and classical information theory are in perfect agreement in characterization and quantification of correlated events. At a microscopic level, where quantum theory is our best candidate for explaining phenomena, however, the situation is different. Our informational inspections of a quantum world, i.e., quantum information theory, is based on our intuition from classical information theory and classical probability theory, mostly the notion of quantum entropy [1, 2]. However, a discrepancy emerges when physical constraints are taken into account to distinguish between quantum physics and classical physics, hence splitting quantum information approach to correlations from that of quantum optics.In quantum optics it is common to study nonclassical features of bosonic systems in a quantum analogue of the classical phase space [3]. While in a classical statistical theory in phase-space the state of the system is represented by a probability distribution, the quantum phase-space distributions can have negative regions, and hence, fail to be legitimate probability distributions [4]. The negativities are thus considered as nonclassicality signatures. Within multipartite quantum states, the phase-space nonclassicality is tempted to be interpreted as quantum correlations, due to the fact that in a classical description of the joint system no such effects are present [5,6].The sharpest contrast between the definition of quantum correlations in quantum information science and that of quantum optics has been demonstrated very recently by Ferraro and Paris [7]. They showed that the two definitions from quantum information and quantum optics are maximally inequivalent, meaning that every quantum state which is classically correlated with respect to the quantum information definition of quantum correlations is nece...

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“…Recall that a general form of bipartite quantum state in the usual orthonormal basis |e i is 12) where d 1 and d 2 are dimensions of first and second part respectively. The norm of concurrence vector is defined as 13) where …”

Section: Multi-qubit Casementioning

confidence: 99%

“…Entangled coherent states have many applications in quantum optics and quantum information processing [3,4,5,6,7,8,9,10,11,12]. Communication via entangled coherent quantum network is investigated in [13] where it is shown that the probability of performing successful teleportation through this network depends on its size.…”

Section: Introductionmentioning

confidence: 99%

Entanglement of Multi-qudit States Constructed by Linearly Independent Coherent States: Balanced Case

Najarbashi¹,

Mirzaei²

2015

Int J Theor Phys

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Multi-mode entangled coherent states are important resources for linear optics quantum computation and teleportation. Here we introduce the generalized balanced N-mode coherent states which recast in the multi-qudit case. The necessary and sufficient condition for bi-separability of such balanced N-mode coherent states is found. We particularly focus on pure and mixed multi-qubit and multi-qutrit like states and examine the degree of bipartite as well as tripartite entanglement using the concurrence measure. Unlike the N-qubit case, it is shown that there are qutrit states violating monogamy inequality. Using parity, displacement operator and beam splitters, we will propose a scheme for generating balanced N-mode entangled coherent states for even number of terms in

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Unified quantification of nonclassicality and entanglement

Cited by 168 publications

References 43 publications

Entanglement swapping of two arbitrarily degraded entangled states

Entanglement swapping of two arbitrarily degraded entangled states

Quantum Correlations in Nonlocal Boson Sampling

Entanglement of Multi-qudit States Constructed by Linearly Independent Coherent States: Balanced Case

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