Abstract
Entangled systems in experiments may be lost or off-line in distributed quantum information processing. This inspires a general problem to characterize quantum operations, which result in breaking of entanglement or not. Our goal in this paper is to solve this problem both in single entanglement and network scenarios. We firstly propose a local model for characterizing all entangled states that are breaking for losing particles. This implies a simple criterion for witnessing single entanglement such as generalized GHZ states and Dicke states. It further provides an efficient witness for entangled quantum networks depending on its connectivity such as $k$-independent quantum networks, completely connected quantum networks, and $k$-connected quantum networks. These networks are universal resources for measurement-based quantum computations. The strong nonlocality can be finally verified by using nonlinear inequalities. These results show distinctive features of both single entangled systems and entangled quantum networks.
Highlights
As one of the remarkable features in quantum mechanics, quantum entanglement has attracted great attentions [1]
We firstly propose a local model for characterizing all entangled states that are breaking for losing particles
We firstly propose a local model for featuring fragile entangled states, that is, the entanglement breaks for some particle-lose channels
Summary
As one of the remarkable features in quantum mechanics, quantum entanglement has attracted great attentions [1]. The quantum correlations generated by local measurements on entangled two-spin systems can not be reproduced from classical physics These nonlocal quantum correlations are verified by violating Bell inequalities [2,3,4]. One example is the cluster states that are universal resources for measurement-based quantum computations [21] In this case, some experimental devices may be not on-line in large-scale or remote tasks, regarded as party-lose noises in which all the local particles shared by one party are taken as one unavailable high-dimensional particle or quantum sources. We firstly propose a local model for featuring fragile entangled states, that is, the entanglement breaks for some particle-lose channels This model is stronger than the biseparable model [7] because GHZ states [5] are not entangled in the present model. The results may shed new light on network entanglement and quantum information processing such as distributed quantum computation
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