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

Abstract

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...

Practical figures of merit and thresholds for entanglement distribution in quantum networks

“…Bell measurements are typically used to obtain long-range bipartite entanglement, while multi-qubit measurements can be made in order to generate multipartite entanglement; see, e.g., Refs. [65][66][67][68][69][70][71][72][73][74][75][76].…”

Delocalized information in quantum networks

“…Quantum networks promise to be one of the first applications of an upcoming quantum technology [1,2] (see also e.g. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]). They are the quantum counterpart of classical networks, where quantum information rather than classical information is distributed, stored and processed.…”

“…These entangled states can then be used for different applications, including the distribution of quantum information via teleportation. Alternatively a top-down approach to quantum networks is used [3,4], where entangled resource states shared among network nodes serve to guarantee the required functionality. In both cases quantum information is stored locally at a given node.…”

Entanglement accessibility measures for the quantum Internet

“…The quantum Internet is modeled as a global-scale quantum communication network composed of quantum subnetworks and networking components. The core network of the quantum Internet is assumed to be an entangled network structure [15,20,21,24,25,27,28,[39][40][41][42][43][44][45][46][47], which is a communication network in which the quantum nodes are connected by entangled connections. An entangled connection refers to a shared entangled system (i.e., a Bell state for qubit systems to connect two quantum nodes) between the quantum nodes.…”