Quantum communication between nodes in quantum networks plays an important role in quantum information processing. Here, we proposed the use of the expected number of quantum channels as a measure of the efficiency of quantum communication for quantum networks. This measure quantified the amount of quantum information that can be teleported between nodes in a quantum network, which differs from classical case in that the quantum channels will be consumed if teleportation is performed. We further demonstrated that the expected number of quantum channels represents local correlations depicted by effective circles. Significantly, capacity of quantum communication of quantum networks quantified by ENQC is independent of distance for the communicating nodes, if the effective circles of communication nodes are not overlapped. The expected number of quantum channels can be enhanced through transformations of the lattice configurations of quantum networks via entanglement swapping. Our results can shed lights on the study of quantum communication in quantum networks.
Quantum communication between nodes in quantum networks plays an important role in quantum information processing. Here, we proposed the use of the expected number of quantum channels as a measure of the efficiency of quantum communication for quantum networks. This measure quantified the amount of quantum information that can be teleported between nodes in a quantum network, which differs from classical case in that the quantum channels will be consumed if teleportation is performed. We further demonstrated that the expected number of quantum channels represents local correlations depicted by effective circles. Significantly, capacity of quantum communication of quantum networks quantified by ENQC is independent of distance for the communicating nodes, if the effective circles of communication nodes are not overlapped. The expected number of quantum channels can be enhanced through transformations of the lattice configurations of quantum networks via entanglement swapping. Our results can shed lights on the study of quantum communication in quantum networks.
Quantum state can be teleported to a remote site by only local measurement and classical communication if the prior Einstein-Podolsky-Rosen quantum channel is available between the sender and the receiver. Those quantum channels shared by multiple nodes can constitute a quantum network. Yet, studies on the efficiency of quantum communication between nodes of quantum networks remain limited, which differs from classical case in that the quantum channel will be consumed if teleportation is performed. Here, we introduce the exclusive quantum channels (EQC) as the measure of efficiency of quantum information transmission. It quantifies the amount of quantum information which can be teleported between nodes in a quantum network. We show that different types of EQC are local quantities with effective circles. Significantly, capacity of quantum communication of quantum networks quantified by EQC is independent of distance for the communicating nodes. Thus, the quantum network can be dealt as the isotropic medium where quantum communication is no-decaying. EQC are studied by both analytical and numerical methods. The EQC can be enhanced by transformations of lattices of quantum network via entanglement swapping. Our result opens the avenue in studying the quantum communication of the quantum networks.
Quantum network is the key to enable distributed quantum information processing. As the single-link communication rate decays exponentially with the distance, to enable reliable end-to-end quantum communication, the number of nodes needs to grow with the network scale. For highly connected networks, we identify a threshold transition in the capacity as the density of network nodes increases: below a critical density the rate is almost zero, while above the threshold the rate increases linearly with the density. Surprisingly, above the threshold the typical communication capacity between two nodes is independent of the distance between them, due to multipath routing enabled by the quantum network. In contrast, for less connected networks such as scale-free networks, the end-to-end capacity saturates to constants as the number of nodes increases, and always decays with the distance. Our results are based on capacity evaluations, therefore the minimum density requirement for an appreciable capacity applies to any general protocols of quantum networks.
Quantum information science has altered the concept of the method of processing and transporting information through the laws of quantum mechanics. Quantum entanglement is one of its basic properties, which is instrumental to non-classical correlations between spatially separate particles. New quantum communication networks and quantum computing systems distributed are based on these interrelations. In this paper, quantum information flow dynamics of multi-particle entangled networks with particular emphasis to the processes governing information transmission, redistribution and maintenance of coupled quantum nodes are discussed. The paper discloses the way in which the entangled structures comprising multiple entities can help in facilitating the sharing of information beyond the capabilities of the classical communication systems. Complex entangled structures are analyzed in terms of the channels through which the flow of quantum information is analyzed in respect to the theoretical models of multi-qubit systems and networked quantum channels. The way the communication between the particles influences the coherence, strength of correlation, as well as the stability of the whole network in general, is given particular attention. The effect of environmental noise and decoherence which can cause a break of entanglement and the loss of efficiency in quantum information exchange is also considered in the analysis. Moreover, the article discusses the application of network topology in order to establish the behaviour of entangled systems. The impact of the structural changes on information transfer reliability and speed is determined by the evaluation of the various forms of quantum nodes and connections. These findings suggest that entangled networks structured appropriately will be able to enhance stability of quantum communication and assist in distributing quantum resources more efficiently. Overall, the present research can be deemed as part of the bigger initiative of scaling up quantum communication infrastructures. The research builds knowledge in the sense that it provides an insight into the behavior of information in multi-particle entangled networks with important considerations being made as to the advancement of robust quantum networks which can be used in future to support the realization of future applications in the area of secure communication, distributed computing and the future developments in information processing technologies.
Quantum entanglement plays a central role in many quantum communication protocols. It allows distant particles to share correlations beyond the limits of classical interactions. Entanglement is essential for superdense coding, quantum teleportation, and secure cryptographic key distribution in quantum communication. It is also a pillar for developing quantum networks, where the management and distribution of entanglement are crucial for connecting distant nodes. Although perfect entanglement is a sought-after ideal, experimental imperatives, including entanglement distribution over long distances, often limit the quality of entangled states. An important question is whether weaker entanglement still offers advantages. First, we study more general tasks than dense coding to show that simpler measurements, combined with entanglement, allow advantageous and sometimes even optimal qubit communication protocols to be obtained. We also demonstrate that simple measurements can generate quantum correlations that cannot be modelled by two classical communication bits and can constitute an optimal protocol with quantum resources. We implement a novel Bell-type inequality tailored for certifying full network non-locality (FNN) to develop certification methods guaranteeing security on an entanglement-based network. Our experiment uses two pairs of polarised entangled photons in a network configuration with three nodes, briefly referred to as a bilocal network scenario. Finally, we show that weakly entangled states can improve communication over a qubit channel using only separate (local) measurements on isotropic non-steerable two-qubit states, without interference, of individual photons, across two communication tasks: secret sharing and its stochastic variant.
The quantum Internet’s significance in information technology is increasingly recognized for its potential to enable secure and private communication. The quantum Internet facilitates the transmission of quantum information over extensive distances, thus unlocking novel possibilities in various applications. In this study we explore the quantum communication capacity within general quantum entangled networks. Leveraging von Neumann entropy, we show the capability of state transfer and information concentration across four-party networks, thereby characterizing the bipartite quantum communication capacity with the support of local operations and classical communications from other parties. We introduce unidirectional and bidirectional models, employing chain or star transferring network configurations, and extend these frameworks to encompass general quantum networks. Furthermore, we provide illustrative examples to underscore the implications of our findings. This research yields the initial nontrivial outcome concerning quantum communication capacity across general quantum networks, shedding light on the potential of quantum networks for advanced communication protocols.
We show that the most general protocol of quantum communication between two end-points of a quantum network with arbitrary topology can be reduced to an ensemble of Choi matrices subject to local operations and classical communication. This is found by using a teleportation-based technique which applies to a wide range of quantum channels both in discrete- and continuous-variable settings, including lossy channels, quantum-limited amplifiers, dephasing and erasure channels. Thanks to this reduction, we compute the optimal rates (capacities) at which two end-points of a quantum network can transmit quantum information, distil entanglement, or distribute secret keys. These capacities are all bounded or equal to a single quantity, that we call the entanglement flux of the quantum network. As a particular case, we derive these optimal rates for the basic paradigm of a linear chain of quantum repeaters. Thus our results establish the ultimate rates for repeater-based and network-assisted quantum communications under the most relevant models of noise and decoherence.