Two-dimensional quantum repeaters

Wallnöfer, Julius; Zwerger, Michael; Muschik, Christine A.; Sangouard, Nicolas; Dür, W.

doi:10.1103/physreva.94.052307

Cited by 63 publications

(70 citation statements)

References 65 publications

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“…However, our bound (1) is applicable even to any multi-party protocol1645 based on sharing a multipartite resource46—such as a multipartite private key47 or a multipartite entangled state like a Greenberger–Horne–Zeilinger state and a cluster state—among plural clients. This is because such a multipartite resource is, usually, freely transformed into a corresponding bipartite resource—secret bits or ebits—between any two of the clients by using an additional LOCC operation, to which our bound (1) is applied.…”

Section: Discussionmentioning

confidence: 99%

Fundamental rate-loss trade-off for the quantum internet

2016

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The quantum internet holds promise for achieving quantum communication—such as quantum teleportation and quantum key distribution (QKD)—freely between any clients all over the globe, as well as for the simulation of the evolution of quantum many-body systems. The most primitive function of the quantum internet is to provide quantum entanglement or a secret key to two points efficiently, by using intermediate nodes connected by optical channels with each other. Here we derive a fundamental rate-loss trade-off for a quantum internet protocol, by generalizing the Takeoka–Guha–Wilde bound to be applicable to any network topology. This trade-off has essentially no scaling gap with the quantum communication efficiencies of protocols known to be indispensable to long-distance quantum communication, such as intercity QKD and quantum repeaters. Our result—putting a practical but general limitation on the quantum internet—enables us to grasp the potential of the future quantum internet.

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Section: Discussionmentioning

confidence: 99%

Fundamental rate-loss trade-off for the quantum internet

2016

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“…This effectively limits the size of the GHZ network state connecting the routers. Regarding fragility, we remark that in fact a three qubit GHZ state can accept more local depolarizing noise per particle than a Bell-pair-only for larger particle numbers there is an increased fragility [57]. The situation for the case of m=3 is depicted in figure 10.…”

Section: Hierarchical Regionsmentioning

confidence: 96%

“…expected traffic. We remark that such a hierarchic arrangement was also implicitly assumed in [51,57]. The features of such hierarchical graphs and their properties in a network structure has recently been analyzed in detail in [98].…”

Section: Hierarchical Regionsmentioning

confidence: 96%

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A quantum network stack and protocols for reliable entanglement-based networks

2019

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We present a stack model for breaking down the complexity of entanglement-based quantum networks. More specifically, we focus on the structures and architectures of quantum networks and not on concrete physical implementations of network elements. We construct the quantum network stack in a hierarchical manner comprising several layers, similar to the classical network stack, and identify quantum networking devices operating on each of these layers. The layers responsibilities range from establishing point-to-point connectivity, over intra-network graph state generation, to inter-network routing of entanglement. In addition we propose several protocols operating on these layers. In particular, we extend the existing intra-network protocols for generating arbitrary graph states to ensure reliability inside a quantum network, where here reliability refers to the capability to compensate for devices failures. Furthermore, we propose a routing protocol for quantum routers which enables the generation of arbitrary graph states across network boundaries. This protocol, in correspondence with classical routing protocols, can compensate dynamically for failures of routers, or even complete networks, by simply re-routing the given entanglement over alternative paths. We also consider how to connect quantum routers in a hierarchical manner to reduce complexity, as well as reliability issues arising in connecting these quantum networking devices. quantum network shall not be limited to the generation of Bell-pairs only [50][51][52][53], because many interesting applications require multipartite entangled quantum states. Therefore, the ultimate goal of quantum networks should be to enable their clients to share arbitrary entangled states to perform distributed quantum computational tasks. An important subclass of multipartite entangled states are so-called graph states [54], and many protocols in quantum information theory rely on this class of states.Here we consider entanglement-based quantum networks utilizing multipartite entangled states [51-53, 55-57] which are capable of generating arbitrary graph states among clients. In general, we identify three successive phases in entanglement-based quantum networks: dynamic, static, and adaptive. In the dynamic phase, which is the first phase, the quantum network devices utilize the quantum channels to distribute entangled states among each other. Once this phase completes, the quantum network devices share certain entangled quantum states, which results in the static phase. In this phase, the quantum network devices store these entangled states for future requests locally. Finally, in the adaptive phase, the network devices manipulate and adapt the entangled states of the static phase. This might be caused either due to requests of clients in networks, but also due to failures of devices in a quantum network.We follow the approach of [51] where a certain network state is stored in the static phase, and client requests to establish certain target (graph) states in the network ar...

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“…This allows one to obtain an efficient scheme to generate long-distance entangled pairs, overcoming the exponential scaling of resources (time or channel usages) of direct transmission. Recently, a generalized repeater scheme to generate multipartite entangled GHZ states has been put forward [42]. Quantum repeaters have been extensively used and discussed also in the context of quantum networks, see e.g.…”

Section: Quantum Communication Over Noisy Channels: Quantum Repeatersmentioning

confidence: 99%

Modular architectures for quantum networks

Pirker¹,

Wallnöfer²,

Dür³

2018

New J. Phys.

130

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We consider the problem of generating multipartite entangled states in a quantum network upon request. We follow a top-down approach, where the required entanglement is initially present in the network in form of network states shared between network devices, and then manipulated in such a way that the desired target state is generated. This minimizes generation times, and allows for network structures that are in principle independent of physical links. We present a modular and flexible architecture, where a multi-layer network consists of devices of varying complexity, including quantum network routers, switches and clients, that share certain resource states. We concentrate on the generation of graph states among clients, which are resources for numerous distributed quantum tasks. We assume minimal functionality for clients, i.e. they do not participate in the complex and distributed generation process of the target state. We present architectures based on shared multipartite entangled Greenberger-Horne-Zeilinger states of different size, and fully connected decorated graph states, respectively. We compare the features of these architectures to an approach that is based on bipartite entanglement, and identify advantages of the multipartite approach in terms of memory requirements and complexity of state manipulation. The architectures can handle parallel requests, and are designed in such a way that the network state can be dynamically extended if new clients or devices join the network. For generation or dynamical extension of the network states, we propose a quantum network configuration protocol, where entanglement purification is used to establish high fidelity states. The latter also allows one to show that the entanglement generated among clients is private, i.e. the network is secure.

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Two-dimensional quantum repeaters

Cited by 63 publications

References 65 publications

Fundamental rate-loss trade-off for the quantum internet

Fundamental rate-loss trade-off for the quantum internet

A quantum network stack and protocols for reliable entanglement-based networks

Modular architectures for quantum networks

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