Quantum entanglement enables numerous quantum applications such as secure communication. Based on entanglement-based quantum networks, long-distance entanglement establishment between two distant end nodes is vital to realize practical quantum networks. However, due to the decoherence and imperfect quantum operations such as the non-determinism of entanglement swapping, the latency of remote entanglement distribution will be increased, simultaneously, ongoing quantum operations will be cut off caused by the short coherence time of quantum memory. In this article, we propose a pre-established entanglement distribution algorithm which contains a time-guaranteed memory cells selection algorithm, aiming to choose the maximum time-matching entangled particle in each node to establish end-to-end entanglement. Simulation results show that for the different scales of grid network topologies, all success probability values are increasing with increase the size of the memory cells and the size of the time slots. Considering constructing the large scale of quantum network, it's necessary to consider employing high multi-mode capability and long lifetime quantum memory.
Quantum entanglement enables numerous quantum applications such as secure communication. Based on entanglement-based quantum networks, long-distance entanglement establishment between two distant end nodes is vital to realize practical quantum networks. However, due to the decoherence and imperfect quantum operations such as the non-determinism of entanglement swapping, the latency of remote entanglement distribution will be increased, simultaneously, ongoing quantum operations will be cut off caused by the short coherence time of quantum memory. In this article, we propose a pre-established entanglement distribution algorithm which contains a time-guaranteed memory cells selection algorithm, aiming to choose the maximum time-matching entangled particle in each node to establish end-to-end entanglement. Simulation results show that for the different scales of grid network topologies, all success probability values are increasing with increase the size of the memory cells and the size of the time slots. Considering constructing the large scale of quantum network, it's necessary to consider employing high multi-mode capability and long lifetime quantum memory.
As the basic principle of quantum networks, quantum entanglement can enable important quantum applications such as teleportation and quantum-key distribution. To realize wide-area quantum communication, entanglement establishment between two remote communication parties is vital, and it requires effective entanglement distribution strategies. Entanglement distribution network models of distributed and centralized entangled pair sources are constructed, based on which two entanglement-distribution algorithms are proposed, i.e., the real-time entanglement distribution (R-TED) algorithm and the pre-established entanglement distribution (P-EED) algorithm, to achieve end-to-end multi-hop entanglement establishment. For the former, the objective is to build long-distance entanglements via hop-by-hop entanglement tentatively and entanglement swapping to finally glue them together. For the latter, which uses pre-established entanglement, entanglements can be established in advance to patch multiple link-level entanglements via entanglement swapping. Simulation results show that as the number of time slots increases, the P-EED algorithm is more efficient and has higher entanglement establishment probability than the R-TED algorithm to establish end-to-end entanglement; while there are fewer memory cells in a quantum memory, such as 10, the R-TED algorithm provides more stable entanglement distribution compared to the P-EED algorithm.
Quantum entanglement enables quantum networks to provide end-to-end sharing of entangled particles, establishing multi-hop path-to-path connections between remote parties. Implementing entanglement distribution plays a vital role in increasing the network scale, and practical entanglement algorithms are required to provide end-to-end multi-hop quantum entanglement. We consider the real-time entanglement distribution (R-TED) and pre-established entanglement distribution (P-EED) to meet this requirement. Based on these two types of entanglement distribution, we propose two algorithms, i.e., R-TED-based routing and entangled pairs allocation (REA) algorithm as well as P-EED-based REA algorithm for end-to-end entanglement establishment, where the practical physical factors (e.g., finite storage capacity and limited storage time) are considered. The R-TED-based REA algorithm can orchestrate the nodes in a route and perform entanglement swapping by adopting real-time entanglement. For the P-EED-based REA algorithm, remote entangled particle sharing can be achieved via pre-shared entanglement distribution and hop-by-hop entanglement swapping. This way, the entanglement routing selection satisfies the storage time constraint and allows two far-apart nodes to share long-distance entangled particles with limited memory cells. We evaluate the performance of the proposed algorithms under different network topologies and sizes, based on which we demonstrate that the network size can significantly affect the efficiency advantage achieved by the P-EED-based approach over the R-TED-based approach.
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 network is a promising platform for numerous quantum applications, including distributed quantum computing, secure communication, and improved sensing. Implementing entanglement distribution between remote quantum nodes plays a vital role in realizing the quantum network's capabilities, and it requires effective remote entanglement distribution protocols. To meet this requirement, we propose two strategies, namely connection-oriented and connectionless, to achieve end-to-end entanglement distribution inspired by the designs of classical communication. For the connection-oriented strategy, an exclusive quantum connection is pre-established between the source and destination nodes. For the connectionless strategy, entanglement swapping is performed hop-by-hop tentatively. In this way, the best-effort service is provided for the source node to establish long-distance entanglement with the destination node. Analogous to classical communication, the proposed strategies have their advantages and disadvantages. Our simulation results show that the connectionless strategy is more efficient and robust than the connection-oriented strategy in terms of throughput. However, the connection-oriented strategy provides reliable end-to-end entanglement distribution but at the expense of higher overhead. Moreover, the application scenarios of these two strategies are discussed. This work paves the road for designing end-to-end entanglement distribution protocols in quantum networks.
Remote entanglement distribution plays a crucial role in quantum networks, which can support many essential and exciting quantum applications. As the network scale expands, it is urgent to design a general and efficient remote entanglement distribution protocol. Nowadays, connection-oriented remote entanglement distribution protocols are available to achieve reliable entanglement distribution. However, in memory-limited quantum networks, connection-oriented entanglement distribution protocols cannot utilize entanglement resources fully and increase the delay of End-to-End (E2E) entanglement connection establishment. To overcome these shortcomings of existing entanglement distribution protocols, we design a connectionless remote entanglement distribution protocol to let Source-Destination (S-D) pairs compete for entanglement resources simultaneously. In our protocol, a fair request scheduling algorithm is proposed to reduce the waiting time without entanglement connections between S-D pairs. Furthermore, a fast scheduling trigger mechanism is proposed to perform entanglement swapping timely to reduce the delay of E2E entanglement connection establishment. The simulation results show that the designed protocol has advantages in terms of resource utilization, throughput, the service completion time of S-D pairs, and the maximum waiting time, compared with the existing remote entanglement distribution protocol.
Quantum networks are designed to transmit quantum bits (qubits) among quantum devices to enable new network resources for the applications. Entanglement distribution and entanglement swapping are fundamental procedures that are required in several network operations. However, they are probabilistic operations, which can lead to severe network performance degradation. This article investigates the engineering problem of resource allocation in quantum networks, considering factors like entanglement distribution probability, quantum memory characteristics, and fidelity. We model this as an optimization model to obtain an optimal solution. In particular, we formulate an integer linear programming (ILP) and develop a heuristic algorithm, aiming to minimize the number of required entangled qubit pairs (Bell pairs or EPR pairs) in any adjacent pair in the quantum network. Extensive simulations are performed to compare the performance of proposed ILP and heuristic. In all the cases, the heuristic produces a comparable solution to the optimal one. Simulation results ensure that the value of maximum utilized Bell pairs in a quantum network highly depends on the value of the probability of entangled pairs established, considering the time in the quantum memory besides the number of incoming requests.