Designing a quantum network protocol

Wojciech Kozlowski, Axel Dahlberg, Stephanie Wehner
2020 Proceedings of the 16th International Conference on emerging Networking EXperiments and Technologies  
The second quantum revolution brings with it the promise of a quantum internet. As the first quantum network hardware prototypes near completion new challenges emerge. A functional network is more than just the physical hardware, yet work on scalable quantum network systems is in its infancy. In this paper we present a quantum network protocol designed to enable end-to-end quantum communication in the face of the new fundamental and technical challenges brought by quantum mechanics. We develop
more » ... quantum data plane protocol that enables end-to-end quantum communication and can serve as a building block for more complex services. One of the key challenges in near-term quantum technology is decoherence -the gradual decay of quantum information -which imposes extremely stringent limits on storage times. Our protocol is designed to be efficient in the face of short quantum memory lifetimes. We demonstrate this using a simulator for quantum networks and show that the protocol is able to deliver its service even in the face of significant losses due to decoherence. Finally, we conclude by showing that the protocol remains functional on the extremely resource limited hardware that is being developed today underlining the timeliness of this work. CCS CONCEPTS • Networks → Network protocol design; Network layer protocols; • Hardware → Quantum communication and cryptography. KEYWORDS quantum internet, quantum networks, quantum communication ACM Reference Format: Figure 1 : Quantum networks will use existing network infrastructure to exchange classical messages for the purposes of running quantum protocols as well as the control and management of the network itself. Long-distance links will be built using chains of automated quantum repeaters. Quantum networks will enhance non-quantum (classical) networks ( Fig. 1 ) and they will execute protocols that are provably impossible to do classically or that are more efficient than what is possible classically. This new paradigm enables new possibilities such as quantum secure communications [7, 32], distributed quantum computation [21], secure quantum computing in the cloud [11, 34] , clock synchronisation [50], and quantum-enhanced measurement networks [36, 38] . This technology is developing rapidly with the first inter-city network planned to go online in the next few years [4] . Quantum communication has been actively researched for many years. Its most well-known application, quantum key distribution (QKD) is a protocol used for secure communications [7, 32]. Shortdistance QKD networks are already being deployed and studied in metropolitan environments (e.g. [64, 77, 81, 91] ) and are even commercially available (e.g. [26, 33, 36, 45] ). Longer distance QKD networks are currently possible provided all intermediate nodes are trusted and physically secure [19, 74, 77, 78] . However, whilst these nodes are capable of exchanging quantum bits (qubits) with their neighbours, they are not capable of forwarding them (including by means of entanglement swapping, a method explained later in this paper). As a result such networks are unable to transmit qubits end-to-end and thus do not offer end-to-end security. The next step is to enable long-distance end-to-end communication of qubits. There are three key challenges in realising this objective: transmission losses, decoherence, and the no-cloning theorem. Decoherence is the loss of quantum information due to interactions with the environment and it limits the lifetime of quantum memories. Typical memory lifetimes in quantum networking hardware range from a few microseconds to just over a second [1] 1 This work is licensed under a Creative Commons Attribution International 4.0 License. Network layer operations (e.g. entanglement swap) Link layer operations (e.g. attempt entanglement) Memory management (alloc/free qubits)
doi:10.1145/3386367.3431293 dblp:conf/conext/KozlowskiDW20 fatcat:6c3mtly4inf43l5zw7sgevr2oq