![]() Several physical systems are being explored as possible platforms for such a repeater, for example color centers in diamond (e.g. ĭespite ongoing experimental efforts, a scalable quantum repeater has yet to be demonstrated. For an in-depth introduction to quantum repeaters, see for example. It can be enhanced by imposing a cut-off condition, such as a maximum time after which stored entanglement is discarded. The simplest possible quantum repeater protocol consists in having nodes constantly trying to generate entanglement and swapping as soon as they hold two entangled qubits, one to each side of the chain. entangled states shared by these nodes and (ii) gluing links together by means of bell state measurements, a process known as entanglement swapping. This is done by (i) establishing elementary links between neighboring nodes, i.e. These are devices that can, in theory, enable long-distance entanglement generation. As an alternative, two distant end nodes can be connected by intermediate nodes, known as quantum repeaters. Classically, photon loss is overcome by direct amplification, but in the quantum case this is impossible for non-orthogonal states due to the no-cloning theorem. Įntanglement generation has been demonstrated at short distances, but scaling up has proved very challenging due to the exponential growth of photon losses with the length of fiber covered. The level of network development required is application-dependent, but all of them rely on entanglement generation and distribution. Beyond QKD, several other applications have been identified, ranging from quantum clock synchronization to distributed quantum computing. We have made our code, in the form of NetSquid simulations and the smart-stopos optimization tool, freely available for use either locally or on high-performance computing centers.Ī quantum internet could be used to perform tasks that are impossible with classical communications alone, the best known example being that of quantum key distribution (QKD). This methodology constitutes an invaluable tool for the development of a blueprint for a pan-European quantum internet. ![]() By applying it to simulations of several different repeater chains, including real-world fiber topology, we demonstrate that it can be used to answer questions such as what are the minimum viable quantum repeaters satisfying given network performance benchmarks. In this work we propose a methodology based on genetic algorithms and simulations of quantum repeater chains for optimization of entanglement generation and distribution. Furthermore, it is generally not clear how an improvement in a certain repeater parameter, such as memory quality or attempt rate, impacts the overall network performance, rendering the path toward scalable quantum repeaters unclear. Quantum repeaters could in theory be used to extend the distances over which entanglement can be distributed, but in practice hardware quality is still lacking. ![]() However, scaling up to such long distances has proved challenging due to the loss of photons, which grows exponentially with the distance covered. ![]() Long-distance quantum communication via entanglement distribution is of great importance for the quantum internet.
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