The Quantum Internet is envisioned, at its final stage, to globally interconnect heterogeneous quantum networks. And this interconnection relays on entangled states shared among several quantum networks. In this paper, we take a step towards the engineering of entanglement as a inter-network resource. Specifically, we consider the interconnection of Quantum Local Area Networks (QLANs), and we show how to dynamically generate inter-QLAN artificial connectivity by means of local operations only. To this aim, we first design the multipartite entangled state to be distributed within each QLAN. Then, we show how such a state can be engineered for obtaining artificial links between different QLANs nodes. By leveraging the properties of a particular class of multipartite entangled states, namely, graph states, our results dynamically adapt the artificial connectivity to the network traffic patterns. Our proposal is preliminary towards scaling the interconnection of quantum networks.
The Quantum Internet is envisioned, at its final stage, to globally interconnect heterogeneous quantum networks. And this interconnection relays on entangled states shared among several quantum networks. In this paper, we take a step towards the engineering of entanglement as a inter-network resource. Specifically, we consider the interconnection of Quantum Local Area Networks (QLANs), and we show how to dynamically generate inter-QLAN artificial connectivity by means of local operations only. To this aim, we first design the multipartite entangled state to be distributed within each QLAN. Then, we show how such a state can be engineered for obtaining artificial links between different QLANs nodes. By leveraging the properties of a particular class of multipartite entangled states, namely, graph states, our results dynamically adapt the artificial connectivity to the network traffic patterns. Our proposal is preliminary towards scaling the interconnection of quantum networks.
Entanglement is unanimously recognized as the key communication resource of the Quantum Internet. Thus, the possibility of implementing unparalleled network functionalities by exploiting entanglement is gaining huge attention. However, the research efforts in this context are mainly focused onbipartite entanglement, often discarding the wide unexplored classes of entanglement shared among more than two parties, known asmultipartite entanglement. In this paper, we aim at exploiting multipartite entanglement asinter-network resource. Specifically, we consider the interconnection of different Quantum Local Area Networks (QLANs), and we show that multipartite entanglement allows to dynamically generate an inter-QLANartificialtopology, by means of local operations only, that overcomes the limitations of the physical QLAN topologies. To this aim, we first design the multipartite entangled state to be distributed within each QLAN. Then, we show how such a state can be engineered to: i) interconnect nodes belonging to different QLANs, and ii) dynamically adapt to different inter-QLAN traffic demands. Our contribution aims at providing the network engineering community with a hands-on guideline towards the concept of artificial topology and artificial neighborhood.
In Quantum Local Area Networks (QLANs) - the near-term building block of the Quantum Internet - the choice of the physical network topology is not so restrictive and binding as in classical LAN in terms of communication capabilities among the network nodes. And the rationale for this is the entanglement-enabled connectivity induced by multipartite entangled states. Indeed, it is possible to create on-demand links between the QLAN nodes by properly manipulating the shared multipartite entangled states. Thus, it is possible to build an overlay entangled network upon the physical one, characterized by a topology different from the physical one and referred to as artificial topology. In this paper we address the fundamental issue of engineering the artificial topology to bypass the limitations induced by the physical network topology. This possibility to overcome the constraints in the network design induced by the physical topology has no counterpart in classical networks. To this aim, we exploit the properties of a class of multipartite entangled states, referred to as graph states, which exhibit unique properties, making them very interesting and promising for engineering artificial topologies in QLANs.
In the near to mid future, Quantum Local Area Networks (QLANs) – the fundamental building block of the Quantum Internet – will unlike exhibit physical topologies characterized by densely physical connections among the nodes. On the contrary, it is pragmatic to consider QLANs based on simpler, scarcely-connected physical topologies, such as star topologies. This constraint, if not properly tackled, will significantly impact the QLAN performance in terms of communication delay and/or overhead. Thankfully, it is possible to create on-demand links between QLAN nodes, without physically deploying them, by properly manipulating a shared multipartite entangled state, namely, a graph state. Thus, it is possible to build an overlay topology, referred to asartificial topology, upon the physical one, by only performing Local Operations and Classical Communication (LOCC). In this paper, we address the fundamental issue of engineering the artificial topology of a QLAN to bypass the limitations induced by the physical topology. The designed framework relays only on local operations, without exchanging signaling among the client nodes of the QLAN, which, in turn, would introduce further delays in a scenario very sensitive to the decoherence. Finally, by exploiting the artificial topology, it is proved that the troubleshooting is simplified, by overcoming the single point of failure, typical of classical LAN star topologies.
Quantum Local Area Networks (QLANs) represent a promising building block for larger scale quantum networks with the ambitious goal -in a long time horizon- of realizing a Quantum Internet. Surprisingly, the physical topology of a QLAN can be enriched by a set of artificial links, enabled by shared multipartite entangled states among the nodes of the network. This novel concept of artificial topology revolutionizes the possibilities of connectivity within the local network, enabling an on-demand manipulation of the artificial network topology. In this paper, we discuss the implementation of the QLAN model in SeQUeNCe, a discrete-event simulator of quantum networks. Specifically, we provide an analysis of how network nodes interact, with an emphasis on the interplay between quantum operations and classical signaling within the network. Remarkably, through the modeling of a measurement protocol and a correction protocol, our QLAN model implementation enables the simulation of the manipulation process of a shared entangled quantum state, and the subsequent engineering of the entanglement-based connectivity. Our simulations demonstrate how to obtain different virtual topologies with different manipulations of the shared resources and with all the possible measurement outcomes, with an arbitrary number of nodes within the network.
The topology of classical networks is determined by physical links between nodes, and after a network request the links are used to establish the desired connections. Quantum networks offer the possibility to generate different kinds of entanglement prior to network requests, which can substitute links and allow one to fulfill multiple network requests with the same resource state. We utilize this to design entanglement-based quantum networks tailored to their desired functionality, independent of the underlying physical structure. The kind of entanglement to be stored is chosen to fulfill all desired network requests (i.e. parallel bipartite or multipartite communications between specific nodes chosen from some finite set), but in such a way that the storage requirement is minimized. This can be accomplished by using multipartite entangled states shared between network nodes that can be transformed by local operations to different target states. We introduce a clustering algorithm to identify connected clusters in the network for a given desired functionality, i.e. the required network topology of the entanglement-based network, and a merging algorithm that constructs multipartite entangled resource states with reduced memory requirement to fulfill all desired network requests. This leads to a significant reduction in required time and resources, and provides a powerful tool to design quantum networks that is unique to entanglement-based networks.
This Thesis contributes to the theory of entanglement distribution in quantum networks, analyzing the generation of long-distance entanglement in particular.We consider that neighboring stations share one partially entangled pair of qubits, which emphasizes the difficulty of creating remote entanglement in realistic settings.The task is then to design local quantum operations at the stations, such that the entanglement present in the links of the whole network gets concentrated between few parties only, regardless of their spatial arrangement.First, we study quantum networks with a two-dimensional lattice structure, where quantum connections between the stations (nodes) are described by non-maximally entangled pure states (links).We show that the generation of a perfectly entangled pair of qubits over an arbitrarily long distance is possible if the initial entanglement of the links is larger than a threshold.This critical value highly depends on the geometry of the lattice, in particular on the connectivity of the nodes, and is related to a classical percolation problem.We then develop a genuine quantum strategy based on multipartite entanglement, improving both the threshold and the success probability of the generation of long-distance entanglement.Second, we consider a mixed-state definition of the connections of the quantum networks.This formalism is well-adapted for a more realistic description of systems in which noise (random errors) inevitably occurs.New techniques are required to create remote entanglement in this setting, and we show how to locally extract and globally process some error syndromes in order to create useful long-distance quantum correlations.Finally, we turn to networks that have a complex topology, which is the case for most real-world communication networks such as the Internet for instance.Besides many other characteristics, these systems have in common the small-world feature, stating that any two nodes are separated by a few links only.Based on the theory of random graphs, we propose a model of quantum complex networks, which exhibit some totally unexpected properties compared to their classical counterparts.5.1 Propagation of a large GHZ state through the lattice . . .5.2 Bit-flip error correction . . . . . . . . . . . . .