Entanglement distribution with separable states has recently attracted considerable attention. Recent results suggest that quantum discord, a measure for quantum correlations beyond entanglement, is responsible for this counterintuitive phenomenon. In this work we study this question from a different perspective and find minimal requirements for a separable state to be useful for entanglement distribution. Surprisingly, we find that the presence of quantum discord is not sufficient to ensure entanglement distribution: There exist states with nonzero quantum discord that nevertheless cannot be used for entanglement distribution. As a result, we show that entanglement distribution is not possible with rank-2 separable states. Our work sheds light on the task of entanglement distribution with separable states and reveals a classification of quantum states with respect to their usefulness for this task.Entanglement distribution with separable states has recently attracted considerable attention. Recent results suggest that quantum discord, a measure for quantum correlations beyond entanglement, is responsible for this counterintuitive phenomenon. In this work we study this question from a different perspective and find minimal requirements for a separable state to be useful for entanglement distribution. Surprisingly, we find that the presence of quantum discord is not sufficient to ensure entanglement distribution: There exist states with nonzero quantum discord that nevertheless cannot be used for entanglement distribution. As a result, we show that entanglement distribution is not possible with rank-2 separable states. Our work sheds light on the task of entanglement distribution with separable states and reveals a classification of quantum states with respect to their usefulness for this task.

arXiv:1309.0984Physical Review ASep 22, 201415 citations

Systematics of entanglement distribution by separable states

Vahid Karimipour, Laleh Memarzadeh, Najmeh Tabe Bordbar

We show that three distant parties, $A$ , $B$ , and $C$ , having no prior entanglement can establish a shared GHZ state by mediating two particles which remain separable from each other and from all the other parties throughout the process. The success probability is $1/7$ . We prove this in a general framework for systematic distribution of entangled states between two and more parties with separable states in $d$ dimensions. The proposed method may facilitate the construction of multinode quantum networks and many other processes which use multipartite entangled states.We show that three distant parties, $A$, $B$, and $C$, having no prior entanglement can establish a shared GHZ state by mediating two particles which remain separable from each other and from all the other parties throughout the process. The success probability is $1/7$. We prove this in a general framework for systematic distribution of entangled states between two and more parties with separable states in $d$ dimensions. The proposed method may facilitate the construction of multinode quantum networks and many other processes which use multipartite entangled states.

arXiv:1506.08396Physical Review ASep 25, 20152 citations

Equilibrium State and Entanglement

Sho Sugiura

Springer thesesJan 1, 20170 citations

A scheme for multipartite entanglement distribution via separable carriers

Alessandro Laneve, Hannah McAleese, Mauro Paternostro

Abstract The ability to reliably distribute entanglement among the nodes of a network is an essential requirement for the development of effective quantum communication protocols and the realization of useful quantum networks. It has been demonstrated, in different contexts, that two remote systems can be entangled via local interactions with a carrier system that always remains in a separable state with respect to such distant particles. We develop a strategy for entanglement distribution via separable carriers that can be applied to any number of network nodes to achieve various entanglement distribution patterns. We show that our protocol results in multipartite entanglement, while the carrier mediating the process is always in a separable state with respect to the network. We provide examples showcasing the flexibility of our approach and propose a scheme of principle for the experimental demonstration of the protocol.Abstract The ability to reliably distribute entanglement among the nodes of a network is an essential requirement for the development of effective quantum communication protocols and the realization of useful quantum networks. It has been demonstrated, in different contexts, that two remote systems can be entangled via local interactions with a carrier system that always remains in a separable state with respect to such distant particles. We develop a strategy for entanglement distribution via separable carriers that can be applied to any number of network nodes to achieve various entanglement distribution patterns. We show that our protocol results in multipartite entanglement, while the carrier mediating the process is always in a separable state with respect to the network. We provide examples showcasing the flexibility of our approach and propose a scheme of principle for the experimental demonstration of the protocol.

arXiv:2206.09701New Journal of PhysicsNov 21, 20224 citations

We show that three distant parties,

A

B

, and

C

, having no prior entanglement can establish a shared GHZ state by mediating two particles which remain separable from each other and from all the other parties throughout the process. The success probability is

1/7

. We prove this in a general framework for systematic distribution of entangled states between two and more parties with separable states in

d

dimensions. The proposed method may facilitate the construction of multinode quantum networks and many other processes which use multipartite entangled states.