Entangled states of multiple qubits can violate Bell-type inequalities indicating nonlocal behavior of multiqubit quantum correlations. We analyze the relation between multipartite entanglement and genuine multipartite nonlocality, characterized by Svetlichny inequality violations, for two families of N − qubit states. We show that for the generalized Greenberger-Horne-Zeilinger family of states, Svetlichny inequality is not violated when the n − tangle is less than 1 / 2 for any even number of qubits. On the other hand, the maximal slice states always violate the Svetlichny inequality when n − tangle is nonzero, and the violation increases monotonically with tangle. Our work generalizes the relations between tangle and Svetlichny inequality violations previously derived for three qubits.Entangled states of multiple qubits can violate Bell-type inequalities indicating nonlocal behavior of multiqubit quantum correlations. We analyze the relation between multipartite entanglement and genuine multipartite nonlocality, characterized by Svetlichny inequality violations, for two families of N − qubit states. We show that for the generalized Greenberger-Horne-Zeilinger family of states, Svetlichny inequality is not violated when the n − tangle is less than 1 / 2 for any even number of qubits. On the other hand, the maximal slice states always violate the Svetlichny inequality when n − tangle is nonzero, and the violation increases monotonically with tangle. Our work generalizes the relations between tangle and Svetlichny inequality violations previously derived for three qubits.

arXiv:2409.10888Physical Review ResearchSep 9, 20250 citations

Detection efficiency in the loophole-free violation of Svetlichny's inequality

Yang Xiang, Huixian Wang, Fang-Yu Hong

Svetlichny's inequality (SI) is a Bell-like inequality, the violation of which can be used to confirm the existence of genuine multipartite correlations. However, poor detector efficiency can possibly cause a so-called detection loophole in actual Svetlichny experiments. We derive an alternative SI to deal with this loophole. If the experimental data can violate this SI, it must result in loophole-free violation of the original SI. We show that the minimum detection efficiency needed for a loophole-free violation of the tripartite SI is about $0.97$ . For the general case of $n$ particles, we give the analytic expression of the needed detection efficiency, and find that its value monotonically and rapidly approaches 1 as the number of particles increases.Svetlichny's inequality (SI) is a Bell-like inequality, the violation of which can be used to confirm the existence of genuine multipartite correlations. However, poor detector efficiency can possibly cause a so-called detection loophole in actual Svetlichny experiments. We derive an alternative SI to deal with this loophole. If the experimental data can violate this SI, it must result in loophole-free violation of the original SI. We show that the minimum detection efficiency needed for a loophole-free violation of the tripartite SI is about $0.97$. For the general case of $n$ particles, we give the analytic expression of the needed detection efficiency, and find that its value monotonically and rapidly approaches 1 as the number of particles increases.

Physical Review ASep 17, 20124 citations

New directions in quantum cryptography

Jozef Gruska, Jan Bouda

Jan 1, 20082 citations

Activation of the violation of the Svetlichny inequality

Paweł Caban, Andrzej Molenda, Kamila Trzcińska

The phenomenon of superactivation of quantum nonlocality, i.e., the fact that several copies of a local quantum state when processed together can generate nonlocal correlations, has recently attracted much attention. However, this problem was considered mainly in a bipartite scenario (although some research in a multipartite case was also undertaken). In this paper we give explicit examples of activation of the violation of the Svetlichny inequality. The violation of the Svetlichny inequality is a sufficient condition of genuine tripartite nonlocality. We show that a number of pure GHZ-type states can be activated. We observe also that the amount of violation of the Svetlichny inequality by two copies of the GHZ state increases with an entanglement of a single copy of the state.The phenomenon of superactivation of quantum nonlocality, i.e., the fact that several copies of a local quantum state when processed together can generate nonlocal correlations, has recently attracted much attention. However, this problem was considered mainly in a bipartite scenario (although some research in a multipartite case was also undertaken). In this paper we give explicit examples of activation of the violation of the Svetlichny inequality. The violation of the Svetlichny inequality is a sufficient condition of genuine tripartite nonlocality. We show that a number of pure GHZ-type states can be activated. We observe also that the amount of violation of the Svetlichny inequality by two copies of the GHZ state increases with an entanglement of a single copy of the state.

Physical Review ASep 17, 20159 citations

Aspects of Quantum Cryptography and Applications

Narayanankutty Karuppath

Jan 1, 20090 citations

0.97

. For the general case of

n

particles, we give the analytic expression of the needed detection efficiency, and find that its value monotonically and rapidly approaches 1 as the number of particles increases.