We propose and analyze a quantum switch for GKP-qubit-based all-photonic entanglement distribution networks. Its design is compatible with a recently studied design of a GKP-qubit-based all-photonic quantum repeater that achieves high end-to-end entanglement rates despite realistic finite squeezing in the GKP-qubit preparation and homodyne detection inef-ficiencies. Our main objective is to optimize the allocation of a finite number of multiplexed GKP-qubit-based entanglement resources among different, arbitrary distance client-pair connections enabled by the switch. We achieve this by overcoming the limitations of previous studies by optimizing the bipartite entanglement generation between clients of a switch (or repeater) node even when they are not equally spaced from the switch. We then maximize the switch's total throughput while ensuring the rates are distributed fairly among all client-pair connections. To better illustrate our result, we analyze an exemplary datacenter network where each user aims to connect to the datacenter alone. Together with the quantum repeater, the proposed quantum switch provides a way to realize entanglement distribution-based quantum networks of arbitrary topology.
We propose and analyze a quantum switch for GKP-qubit-based all-photonic entanglement distribution networks. Its design is compatible with a recently studied design of a GKP-qubit-based all-photonic quantum repeater that achieves high end-to-end entanglement rates despite realistic finite squeezing in the GKP-qubit preparation and homodyne detection inef-ficiencies. Our main objective is to optimize the allocation of a finite number of multiplexed GKP-qubit-based entanglement resources among different, arbitrary distance client-pair connections enabled by the switch. We achieve this by overcoming the limitations of previous studies by optimizing the bipartite entanglement generation between clients of a switch (or repeater) node even when they are not equally spaced from the switch. We then maximize the switch's total throughput while ensuring the rates are distributed fairly among all client-pair connections. To better illustrate our result, we analyze an exemplary datacenter network where each user aims to connect to the datacenter alone. Together with the quantum repeater, the proposed quantum switch provides a way to realize entanglement distribution-based quantum networks of arbitrary topology.
The Gottesman–Kitaev–Preskill (GKP) code, being information theoretically near optimal for quantum communication over Gaussian thermal-loss optical channels, is likely to be the encoding of choice for advanced quantum networks of the future. Quantum repeaters based on GKP-encoded light have been shown to support high end-to-end entanglement rates across large distances despite realistic finite squeezing in GKP code preparation and homodyne detection inefficiencies. Here, we introduce a quantum switch for GKP qubit-based quantum networks. Its architecture involves multiplexed GKP qubit-based entanglement link generation with clients and their all-photonic storage, enabled by GKP qubit graph state resources. The switch uses a multiclient generalization of a recently introduced entanglement-ranking-based link matching heuristic for bipartite entanglement distribution between clients via entanglement swapping. Since generating the GKP qubit graph state resource is hardware intensive, given a total resource budget and an arbitrary layout of clients, we address the question of their optimal allocation to the different client–pair connections served by the switch such that the switch's sum throughput is maximized while also being fair in terms of the individual entanglement rates. We illustrate our results for an exemplary data center network, where the data center is a client of a switch, and all of its other clients aim to connect to the data center alone—a scenario that also captures the general case of a gateway router connecting a local area network to a global network. Together with compatible quantum repeaters, our quantum switch provides a way to realize quantum networks of arbitrary topology.
The distribution of quantum entanglement between remote clients offers opportunities for secure communication, distributed quantum computation, and quantum-enhanced sensing. A key technology for allowing such a quantum network to extend over large distances is the quantum repeater, which typically employs a long-lived quantum memory with an optical interface. The past decade has seen tremendous progress in experimentally realizing the fundamental building blocks of these repeaters, but open questions remain on what architectures achieve optimal entanglement flows in multi-user quantum networks. Here, we propose a quantum router architecture comprising many quantum repeater nodes in a flexible photonic switchboard architecture to broker entanglement flows across such networks. We compute the rate and fidelity of entanglement distribution using this architecture using an event-based simulation platform. We find that the router's photonic switchboard improves the entanglement fidelity with the number of qubits per node, without a significant drop in the entanglement distribution rate. The proposed quantum router architecture uses present-day photonic switch technology such as photonic integrated circuits, opening a path to near-term deployable multi-user quantum networks.
Quantum communication between two distant parties will serve as a cornerstone of the future quantum internet. However, many existing quantum communication schemes face a critical bottleneck: the need to generate a sufficient number of entangled Bell pairs over long distances. Although photons are ideal carriers of quantum information, overcoming photon loss and the exponential attenuation of signals remains a major challenge. We propose an all-photonic quantum repeater architecture that enables quantum communication over a distance of1,000kmwith equidistant repeater spacing extended to 9 km -approximately 2 to 6 times longer than in previously proposed all-photonic schemes. This extended repeater spacing arises from the combined use of elementary entangled Bell pairs protected by both continuous-variable and discrete-variable quantum error correction codes-namely, the bosonic Gottesman-Kitaev-Preskill (GKP) code and the [[7], [1], [3]] Steane code-whose combination yields a synergistic effect that surpasses a simple additive improvement, enhancing robustness against photon loss. This architecture incorporates a new ranking criterion and a multi-reflection mirror-based optical cavity as a free-space photonic memory module, which we model in terms of its length and mirror-reflection efficiency. To more accurately capture realistic physical conditions during photonic resource preparation, we model the presence of switching-induced imperfections by introducing an optical switch into the simulation, in addition to commonly considered imperfections such as finite GKP squeezing, finite detection efficiency, and finite fiber coupling efficiency. In the presence of these imperfections, our realization requires fewer than3,800GKP qubits per repeater station per protocol run-a value significantly smaller than in prior all-photonic proposals.
With the advent of the construction and deployment of entanglement-based quantum networks, the efficient use of network resources will become a critical challenge for the scalable operation of such a system. Recently, architectures that incorporate memoryless optical switches have gained attention for forwarding entangled photons. By leveraging these architectures, costly resources such as high efficiency Bell State Analyzers (BSAs) can be shared across the network. Nevertheless, the introduction of switching substantially complicates the process of multiplexing and resource allocation compared to an individual link. In this work, we propose a switching protocol for unbuffered, multidrop quantum networks in a photonic synchronization domain that establishes a link between two end nodes using a shared BSA in the switched network. To achieve this, two end nodes cooperatively select the target BSA node with the lowest path cost and independently reserve each path within the network. Bi-path reservations are performed to allocate resources in a distributed manner. The proposed protocol is evaluated through simulation on Q-Fly network topologies under varying traffic conditions. The results demonstrate high link establishment success with stable performance even under increased network load. These capabilities which are driven by our proposed protocol are an essential way to realize large-scale, managed, and automated quantum networks.
Quantum networks create a completely new way for communication, and the most important function of a quantum network is to generate long-distance quantum entanglement to serve a number of quantum applications. As the scale of the network expands, in order to establish end-to-end entanglement between two remote nodes, entangled pairs need to be generated and distributed among multiple repeaters along the path from the source to the destination, which requires a specific protocol to negotiate resource allocations and quantum operations among the repeaters. Thus, to realize such remote entanglement distribution in a quantum network, designing a stable and reliable protocol becomes urgent and necessary. In this article, we focus on how to guarantee the generation rate of entangled pairs between any two quantum nodes to meet the requirements of various quantum applications in a large-scale quantum network. We present a connection-oriented entanglement distribution protocol inspired by the connection-oriented communication model in classical networks. Our protocol is located in the network layer of the quantum network to enable end-to-end quantum communication. Three main features are provided by the proposed protocol: 1) it is reliable and can guarantee the successful entanglement generation; 2) it can reduce the influence of quantum decoherence via reducing the latency caused by resource competition; and 3) it can guarantee the rate of generating entanglement between two quantum nodes according to the requirement of quantum applications.
Quantum communication between two distant parties will serve as a cornerstone of the future quantum internet. However, generating enough entangled Bell pairs over long distances is a critical bottleneck. Although photons are ideal carriers of quantum information, overcoming photon loss and the exponential attenuation of signals remains a major challenge. We propose an all-photonic quantum repeater architecture that enables quantum communication over 1,000 km with an equidistant repeater spacing of 9 km. This repeater spacing is enabled by elementary entangled Bell pairs protected through the concatenation of continuous-variable and discrete-variable quantum error correction codes, namely, the bosonic Gottesman-Kitaev-Preskill (GKP) code and the [[7,1,3]] Steane code, whose combination yields a synergistic improvement in robustness against photon loss. This architecture incorporates a new ranking criterion and a multi-reflection mirror-based optical cavity as a free-space photonic memory module, which we model in terms of its length and mirror-reflection efficiency. Additionally, we propose two heuristic construction methods for the elementary entangled Bell pairs. One method introduces up to two-qubit correlated errors within each logical qubit but requires a large number of GKP qubits, while the other allows up to three-qubit correlated errors within each logical qubit but requires fewer GKP qubits. To more accurately capture realistic physical conditions during photonic resource preparation, we include switching-induced imperfections in our simulations, in addition to other standard optical imperfections. In the presence of these imperfections, our realization requires only a few thousand GKP qubits per repeater station per protocol run, a resource requirement significantly smaller than the corresponding resource requirements of prior third-generation all-photonic repeater proposals.