Quantum entanglement is so fundamentally differ- ent from a network packet that several quantum network stacks have been proposed; one of which has even been experimentally demonstrated. Several simulators have also been developed to make up for limited hardware availability, and which facili- tate the design and evaluation of quantum network protocols. However, the lack of shared tooling and community-agreed node architectures has resulted in protocol implementations that are tightly coupled to their simulators. Besides limiting their reusabil- ity between different simulators, it also makes building upon prior results and simulations difficult. To address this problem, we have developed QuIP: a P4-based Quantum Internet Protocol prototyping framework for quantum network protocol design. QuIP is a framework for designing and implementing quantum network protocols in a platform-agnostic fashion. It achieves this by providing the means to flexibly, but rigorously, define device architectures against which quantum network protocols can be implemented in the network programming language P416. QuIP also comes with the necessary tooling to enable their execution in existing quantum network simulators. We demonstrate its use by showcasing V1Quantum, a completely new device architecture, implementing a link- and network-layer protocol, and simulating it in the existing simulator NetSquid.@en

We introduce NetQASM, a low-level instruction set architecture for quantum internet applications. NetQASM is a universal, platform-independent and extendable instruction set with support for local quantum gates, powerful classical logic and quantum networking operations for remote entanglement generation. Furthermore, NetQASM allows for close integration of classical
logic and communication at the application layer with quantum operations at the physical layer. This enables quantum network applications to be programmed in high-level platform-independent software, which is not possible using any other QASM variants. We implement NetQASM in a series of tools to write, parse, encode and run NetQASM code, which are available online. Our tools include a higher-level software development kit (SDK) in Python, which allows an easy way of programming applications for a quantum internet. Our SDK can be
used at home by making use of our existing quantum simulators, NetSquid and SimulaQron, and will also provide a public interface to hardware released on a future iteration of Quantum Network Explorer.@en

The Second Quantum Revolution facilitates the engineering of new classes of sensors, communication technologies, and computers with unprecedented capabilities. Supply chains for quantum technologies are emerging, some focused on commercially available components for enabling technologies and/or quantum-technologies research infrastructures, others with already higher technology-readiness levels, near to the market. In 2018, the European Commission has launched its large-scale and long-term Quantum Flagship research initiative to support and foster the creation and development of a competitive European quantum technologies industry, as well as the consolidation and expansion of leadership and excellence in European quantum technology research. One of the measures to achieve an accelerated development and uptake has been identified by the Quantum Flagship in its Strategic Research Agenda: The promotion of coordinated, dedicated standardisation and certification efforts. Standardisation is indeed of paramount importance to facilitate the growth of new technologies, and the development of efficient and effective supply chains. The harmonisation of technologies, methodologies, and interfaces enables interoperable products, innovation, and competition, all leading to structuring and hence growth of markets. As quantum technologies mature, the time has come to start thinking about further standardisation needs. This article presents insights on standardisation for quantum technologies from the perspective of the CEN-CENELEC Focus Group on Quantum Technologies (FGQT), which was established in June 2020 to coordinate and support the development of standards relevant for European industry and research.

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Scaling current quantum communication demonstrations to a large-scale quantum network will require not only advancements in quantum hardware capabilities, but also robust control of such devices to bridge the gap in user demand. Moreover, the abstraction of tasks and services offered by the quantum network should enable platform-independent applications to be executed without the knowledge of the underlying physical implementation. Here we experimentally demonstrate, using remote solid-state quantum network nodes, a link layer, and a physical layer protocol for entanglement-based quantum networks. The link layer abstracts the physical-layer entanglement attempts into a robust, platform-independent entanglement delivery service. The system is used to run full state tomography of the delivered entangled states, as well as preparation of a remote qubit state on a server by its client. Our results mark a clear transition from physics experiments to quantum communication systems, which will enable the development and testing of components of future quantum networks.

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The testing of quantum applications can be approached from three perspectives. The first one concerns the certification of the accuracy of the quantum device where the application is run. The second one has to do with the classical verification of the result output by the application. Yet a third one addresses the problem from the software engineering perspective. As new quantum applications that run in Noisy Intermediate-Scale Quantum devices are developed, there is an increasing need for tools that can help to find bugs and verify that these applications work as expected. In this thesis we design and develop such a tool. We introduce QuTAF, a test automation framework for quantum applications that is based in the robot framework. To the best of our knowledge, this is the first test automation framework software developed and used for testing quantum applications in a real quantum node. We prove that our QuTAF is capable of detecting minor deficiencies in current state-of-the-art quantum hardware, by running tests for small quantum applications
executed in a networked quantum node. We also simulate and test two different
failure scenarios to validate the capabilities of our QuTAF. We simulate quantum
devices affected by depolarizing and dephasing noise, and find that our QuTAF is able to detect errors introduced by an increase in the depolarization probability, but is otherwise insensitive to the errors produced by the dephasing of quantum states. We also simulate bugs present in the quantum programs, and prove that our QuTAF is able to correctly identify these as failing test cases.

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 a 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.@en

The quantum technology revolution brings with it the promise of a quantum internet. A new --- quantum --- network stack will be needed to account for the fundamentally new properties of quantum entanglement. The first realisations of quantum networks are imminent and research interest in quantum network protocols has started growing. In the non-quantum world, programmable data planes have broken the pattern of ossification of the protocol stack and enabled a new --- software-defined --- network software architecture. Similarly, a programmable quantum data plane could pave the way for a software-defined quantum network architecture. In this paper, we demonstrate how we use P4-16 to explore abstractions and device architectures for quantum networks.@en

The vision of a quantum internet is to fundamentally enhance Internet technology by enabling quantum communication between any two points on Earth. While the first realisations of small scale quantum networks are expected in the near future, scaling such networks presents immense challenges to physics, computer science and engineering. Here, we provide a gentle introduction to quantum networking targeted at computer scientists, and survey the state of the art. We proceed to discuss key challenges for computer science in order to make such networks a reality.

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