Efficient entanglement routing in Quantum Data Networks (QDNs) is essential in order to concurrently establish as many Entanglement Connections (ECs) as possible, which in turn maximizes the network throughput. In this work, we consider a new class of QDNs with wavelength division multiplexed (WDM) quantum links where each quantum repeater will perform entanglement swapping by measuring two photonic qubits coming from some entangled photon sources directly on the same wavelength. To address unique challenges in achieving a high network throughput in such QDNs, we propose QuRWA to jointly optimize the entanglement routing and wavelength assignment. To this end, we introduce a key concept named Co-Path to improve fault-tolerance: all ELs in a Co-Path set will be assigned the same wavelength and this may serve as backup for some other ELs in the same Co-Path when establishing ECs. We design efficient algorithms to optimize the Co-Path selection and wavelength assignment to maximize resource utilization and fault tolerance. Extensive simulations demonstrate that compared with the methods without introducing Co-Path, QuRWA improves the network throughput by up to 122%.
Efficient entanglement routing in Quantum Data Networks (QDNs) is essential in order to concurrently establish as many Entanglement Connections (ECs) as possible, which in turn maximizes the network throughput. In this work, we consider a new class of QDNs with wavelength division multiplexed (WDM) quantum links where each quantum repeater will perform entanglement swapping by measuring two photonic qubits coming from some entangled photon sources directly on the same wavelength. To address unique challenges in achieving a high network throughput in such QDNs, we propose QuRWA to jointly optimize the entanglement routing and wavelength assignment. To this end, we introduce a key concept named Co-Path to improve fault-tolerance: all ELs in a Co-Path set will be assigned the same wavelength and this may serve as backup for some other ELs in the same Co-Path when establishing ECs. We design efficient algorithms to optimize the Co-Path selection and wavelength assignment to maximize resource utilization and fault tolerance. Extensive simulations demonstrate that compared with the methods without introducing Co-Path, QuRWA improves the network throughput by up to 122%.
Quantum Data Networks (QDNs) typically leverage teleportation to reliably send data quantum bits (called qubits) to their destinations. To teleport a data qubit from Alice to Bob, one entanglement connection between Alice and Bob needs to be established. Accordingly, we have to establish as many entanglement connections as possible with limited quantum resources in order to maximize the network throughput. Conventional methods assume a known traffic matrix and calculate the paths to establish entanglement connections in one batch using a centralized algorithm. However, these methods are not scalable in large scale QDNs since it is time consuming to optimize the entanglement paths for a batch of requests, which may result in a long time slot duration and significantly reduce the network throughput. To address this issue, we propose an Online Entanglement Routing (OER) scheme which determines the entanglement paths for each request when it arrives. In addition, OER pursues work conservation and fairness among all requests in the QDNs. Through extensive simulations, we demonstrate that OER not only outperforms two representative heuristics by up to 61.27% and 52.79%, respectively, in terms of average request completion time, but also achieves a better fairness performance than these two counterparts.
Entanglement routing plays a vital role in distributed quantum computing and quantum networks. Previous works on entanglement routing have addressed several design challenges due to limited quantum resources, failures to establish entanglement, and decoherence of established entanglement, but considered neither the limitations imposed by having a limited number of entangled photon sources (EPSes), nor the benefits of using all-optical (or quantum) switching to distribute entangled photons. In this paper, we first explore the problem of jointly optimizing entanglement routing and EPS assignment, assuming no all-optical switching capability. In other words, a pair of entangled photons generated by one EPS can be distributed to two neighboring quantum nodes. We then relax the above assumption so as to allow a pair of entangled photons generated by one EPS to be distributed to non-adjacent nodes using all-optical switching. We propose two corresponding solutions, namely, entanglement routing and EPS assignment (or ERSA), and ERSA with all-optical switching-based distribution (or ERSA+D) that aim to maximize the number of entanglement connections between the given set of source-destination (SD) pairs while avoiding starvation and achieving fairness among the SD pairs. In order to obtain efficient solutions in a large discrete solution space in a timely manner, we first formulate each optimization problem as an Integer Linear Programming (ILP), and then propose efficient algorithms to derive near-optimal solutions based on relaxation, Lagrangian decomposition, duality iteration, and rounding techniques. Extensive simulations show that ERSA+D can increase network throughput by up to 1652% and 113%, respectively, thanks to EPS assignment optimization, and all-optical switching based entanglement distribution.
Entanglement routing plays a vital role in quantum networks. Previous works on entanglement routing did not note that all-optical switching capacity can be used to improve the network throughput or ignored that the placement of Entangled Photon Sources (EPS), another type of precious (and costly) quantum source, which also limits the network throughput. In this paper, we propose OptEPS to jointly optimize all-optical switching and EPS placement in entanglement routing to maximize the quantum network throughput. The main challenge of OptEPS lies in two folds: i). an entanglement may fail to be created; ii). the joint optimization problem suffers from a large time complexity. To overcome these challenges, we first formulate the joint optimization problem as a link-path based model and prune out some candidate paths in order to reduce the time complexity. Then, efficient algorithms are proposed to derive a near-optimal solution in a timely manner. Extensive simulations show that compared with the solutions ignoring EPS placement or without introducing all-optical switching, OptEPS will increase the network throughput by 1557% and 109%, respectively.
The quantum network is designed to connect numerous quantum nodes and support various ground-breaking quantum applications. Most of these applications require communicating parties to share entangled pairs. Therefore, entanglement routing, a technology distributing entangled pairs between distant quantum nodes, plays a vital role in realizing quantum networks’ capability. However, due to the limitation of quantum memory size and quantum decoherence, the entangled pairs shared by adjacent quantum nodes can hardly satisfy concurrent entanglement routing requests, thus leading to severe network congestion. In this paper, we propose a novel congestion mitigation (CM) scheme to tackle such bottleneck problems. The basic idea of CM is to “recycle” idle link-level entanglement resources from well-resourced links to bottleneck links utilizing a unique enabling technology of quantum networks, called entanglement swapping. CM can increase the capacity of each bottleneck link, thus overcoming resource limitations to improve resource utilization and network throughput. To complete our work, we also propose a swapping-based entanglement routing design, including path selection and resource allocation algorithms. Extensive simulations show that our design can significantly alleviate network congestion and improve the request service rate of quantum networks compared to the traditional entanglement routing designs.
There are two conventional methods to establish an entanglement connection in a Quantum Data Network (QDN). One is to create single-hop entanglement links first and then connect them with quantum swapping, and the other is for-warding one of the entangled photons from one end to the other via all-optical switching at intermediate nodes to directly establish an entanglement connection. Since a photon is easy to be lost during a long distance transmission, all existing works are adopting the former method. However, in a room size network, the success probability of delivering a photon across multiple links via all-optical switching is not that low. In addition, with an all-optical switching technique, we can save quantum memory at the intermediate nodes. Accordingly, we are expecting to establish significantly more entanglement connections with limited quantum resources by first creating entanglement segments, each spanning multiple quantum links, using all-optical switching, and then connecting them with quantum swapping.In this paper, we design SEE, a Segmented Entanglement Establishment approach that seamlessly integrates quantum swapping and all-optical switching to maximize quantum network throughput. SEE first creates entanglement segments over one or multiple quantum links with all-optical switching, and then connect them with quantum swapping. It is clear that an entanglement link is only a special entanglement segment. Accordingly, SEE can theoretically outperform conventional entanglement link based approaches. Large scale simulations show that SEE can achieve up to 100.00% larger throughput compared with the state-of-the-art entanglement link based approach, i.e., REPS.
There are two conventional methods to establish an entanglement connection in a Quantum Data Networks (QDN). One is to create single-hop entanglement links first and then connect them with quantum swapping, and the other is forwarding one of the entangled photons from one end to the other via all-optical switching at intermediate nodes to directly establish an entanglement connection. The two methods both have pros and cons. Respectively, the former method has a higher success probability of constructing entanglement link, but it would consume more quantum resources. The latter method, however, has a lower success probability to deliver a photon across multiple quantum links with fewer quantum resources. Accordingly, we are expecting to establish significantly more entanglement connections with limited quantum resources by first creating entanglement segments, each spanning multiple quantum link, using all-optical switching, and then connecting them with quantum swapping. In this paper, we design SEE, a Segmented Entanglement Establishment approach that seamlessly integrates quantum swapping and all-optical switching to maximize quantum network throughput. SEE first creates entanglement segments over one or multiple quantum links with all-optical switching, and then connect them with quantum swapping. Accordingly, SEE can theoretically outperform conventional entanglement link-based approaches. Large scale simulations show that SEE can achieve up to 100.00% larger throughput compared with the state-of-the-art entanglement link-based approaches, e.g., Redundant Entanglement Provisioning and Selection (REPS).