In future quantum networks, satellite-mediated quantum communication could be used to enable distributed quantum computing (DQC). In this talk, we present the current state of our ongoing analysis on potential use cases for satellite-enabled distributed quantum computing and on their feasibility based on hardware restrictions and algorithm requirements: On the one hand, we investigate entanglement distribution via satellites, considering different orbits and entanglement distribution schemes, and evaluating restrictions regarding, e.g., entanglement distribution rates or connection times. On the other hand, we analyse and assess possible DQC applications that might require long-range communication. Furthermore, we investigate the current state of the art of quantum-computing hardware and interconnects between matter qubits and flying qubits (photons), with a particular focus on DQC. These considerations will enable us to evaluate the gap to be bridged by future developments and to identify the necessary steps to be taken for a future implementation of satellite-enabled DQC.
In future quantum networks, satellite-mediated quantum communication could be used to enable distributed quantum computing (DQC). In this talk, we present the current state of our ongoing analysis on potential use cases for satellite-enabled distributed quantum computing and on their feasibility based on hardware restrictions and algorithm requirements: On the one hand, we investigate entanglement distribution via satellites, considering different orbits and entanglement distribution schemes, and evaluating restrictions regarding, e.g., entanglement distribution rates or connection times. On the other hand, we analyse and assess possible DQC applications that might require long-range communication. Furthermore, we investigate the current state of the art of quantum-computing hardware and interconnects between matter qubits and flying qubits (photons), with a particular focus on DQC. These considerations will enable us to evaluate the gap to be bridged by future developments and to identify the necessary steps to be taken for a future implementation of satellite-enabled DQC.
The objective of Sat-DQC is to analyze and identify potential use cases for distributed quantum computing (DQC) assisted by satellite-mediated quantum communication links. In our talk, we present our approach to analyze these scenarios: On the one hand we investigate entanglement distribution via satellites, considering, e.g., different orbits and entanglement distribution schemes. On the other hand we analyze and assess DQC applications that are suitable to be executed under the restrictions of the satellite channel, e.g. regarding entanglement distribution rate or limited connection times. One possible DQC scenario to be analyzed is connecting quantum computing clusters in different geographical locations to enable quantum computations that do not fit in any of the individual clusters. Due to the constraints on entanglement distribution via satellites, the class of DQC algorithms that can be implemented will be limited to those that generate only a small, but non-negligible, amount of entanglement across QPUs. A secondary scenario to be investigated is blind quantum computing, where a client of limited quantum resources requires to perform a calculation on a remote quantum server, without revealing any information about the computation. This scenario requires quantum communication between the two parties and, since the parties may be located far apart from each other, satellite links should be preferred.
A large scale quantum network requires the distribution of high-fidelity end-to-end entanglement. To overcome the range limitations inherent to terrestrial fiber, a leading architecture has emerged: satellite-based sources transmitting entanglement to quantum repeaters on the ground. By bridging the gap between abstract analytical frameworks and computationally heavy numerical simulations, this paper provides the first quantitative answer to the question of such a network's achievable performance with current and near-term space technology, while accounting for entanglement swapping and purification. This is achieved by integrating a detailed physical model of a satellite-to-ground link into an analytical entanglement resource estimation framework for quantum repeaters, enabling an optimization of the end-to-end entanglement rate. Our analysis, performed across leading quantum hardware platforms, shows that Low Earth Orbit satellite constellations combined with quantum repeaters employing Neutral Atom or Nitrogen and Silicon Vacancy qubits, could enable a global quantum network, distributing entanglement over distances up to 20,000 km, sufficient for connecting any two points on Earth. This work highlights the major bottlenecks in space and quantum hardware technologies, which need to be addressed, thereby guiding informed investments necessary for enabling a large scale quantum network.
Recent developments have reported on the feasibility of interconnecting small quantum registers in a quantum information network of a few meter-scale for distributed quantum computing purposes. Small quantum processors in a network represent a promising solution to the scalability problem of manipulating more than thousands of noise-free qubits. Here, we propose and assess a satellite-enabled distributed quantum computing system at the French national scale based on existing infrastructures in Paris and Nice. We consider a system composed of both a ground and a Space segment, allowing for the distribution of end-to-end entanglement between Alice in Paris and Bob in Nice, each owning a few-qubit processor composed of trapped ions. In the context of quantum computing, this entanglement resource can be used for the teleportation of a qubit state or for gate teleportation. After having developed a model, we numerically assess the entanglement distribution rate and fidelity generated by this space-based quantum information network and discuss concrete use cases and service performance levels in the framework of distributed quantum computing. We obtain 90 end-to-end entangled photon pairs distributed over a satellite pass of 331 s that can perform a teleportation-based controlled-Z operation with a fidelity of at most 82%.
Driven by quantum superposition and entanglement, the swift advancement of quantum computing has highlighted the limitations of classical computation. As a solution, Quantum Networks (QNs) have emerged, offering high-quality entanglement connections and reliable quantum state transmission, enabling a range of applications that exceed the limitations of classical data networks, including quantum communication and distributed quantum computing (DQC). This article delves into key components and concepts such as quantum entanglement, quantum decoherence and entanglement distribution. It then explores quantum remote secure communication technologies, including quantum teleportation, quantum key distribution (QKD), quantum dense coding, quantum repeater technology, and quantum satellite communication. We also provide a detailed introduction to quantum remote entanglement distribution and quantum entanglement routing design, including current research progress and a discussion on the challenges and existing solutions for constructing large-scale QNs. The aim of this article is to provide readers with a fundamental understanding of QNs, an assessment of current research, and insights into the main challenges and solutions in this emerging field. Through these discussions, we hope to help readers better understand the potential and future direction of QNs.
The exploration of distributed quantum computing (DQC) represents a significant frontier in quantum information science, aiming to harness the unique properties of quantum mechanics to solve complex computational problems effectively. This paper discusses the diverse architectures and models that facilitate the distribution of quantum computing tasks across multiple quantum nodes, thereby addressing the limitations inherent in single quantum devices. DQC systems exploit the principles of superposition and entanglement to enhance computational capabilities beyond what classical computing systems can achieve. We examine various DQC architectures, including both quantum-classical hybrid systems and fully quantum distributed systems, highlighting their respective benefits and challenges. Key issues such as coherence, communication overhead, and error correction are discussed in detail, and we analyze specific use cases where DQC demonstrates superior performance relative to classical computing approaches, including optimization problems in logistics and finance, as well as quantum simulations for material science. Furthermore, we identify future research directions aimed at overcoming existing barriers to the practical implementation of DQC systems. By assessing the current landscape and future possibilities of DQC, this paper underscores the transformative potential of distributed quantum computing in various fields, paving the way for realizing more complex quantum algorithms and applications.
A key technical requirement of any future quantum network is the ability to distribute quantum-entangled resources between two spatially separated points at a high rate and high fidelity. Entanglement distribution protocols based on satellite platforms, which transmit and receive quantum resources directly via free-space optical propagation, are therefore excellent candidates for quantum networking, since the geometry and loss characteristics of satellite networks feasibly allow for up to continental-scale (∼103 km) over-the-horizon communication without the infrastructure, cost, or losses associated with equivalent fibre-optic networks. In this work, we explore two network topologies commonly associated with quantum networks - entanglement distribution between two satellites in low-Earth orbit mediated by a third satellite and entanglement distribution between two ground stations mediated by a satellite in low-Earth orbit, and two entanglement distribution schemes - one where the central satellite is used as a relay, and the other where the central satellite is used to generate and distribute the entangled resource directly. We compute a bound on the rate of distribution of distillable entanglement achieved by each protocol in each network topology as a function of the network channels for both single-rail discrete- (DV) and continuous-variable (CV) resources and use or non-use of probabilistic noiseless linear quantum amplification (NLA). In the case of atmospheric channels we take into account the turbulent and optical properties of the free-space propagation. We determine that for the triple-satellite network configuration, the optimal strategy is to perform a distributed NLA scheme in either CV or DV, and for the ground-satellite-ground network the optimal strategy is to distribute a DV resource via the central satellite.