Quantum network extends the ability to transmit information securely from two-party communication to multi-party communication with arbitrarily long distances. The efficiency of secure communication in a quantum network depends on both the topology of the network and the strategy of communication relays. In this paper, we propose a strategy to build a quantum network integrating various types of quantum secure direct communication (QSDC) schemes. A cost optimization model is presented to measure the cost of transmitting secure messages in a quantum network. Within the model, two types of quantum network strategies, the quantum circuit switching strategy and the quantum packet switching strategy, are proposed and compared. Numerical simulations in a specific network show that the quantum packet switching strategy is more favorable in future quantum networks taking into account robustness and cost required when using different types of QSDC schemes.
Quantum network extends the ability to transmit information securely from two-party communication to multi-party communication with arbitrarily long distances. The efficiency of secure communication in a quantum network depends on both the topology of the network and the strategy of communication relays. In this paper, we propose a strategy to build a quantum network integrating various types of quantum secure direct communication (QSDC) schemes. A cost optimization model is presented to measure the cost of transmitting secure messages in a quantum network. Within the model, two types of quantum network strategies, the quantum circuit switching strategy and the quantum packet switching strategy, are proposed and compared. Numerical simulations in a specific network show that the quantum packet switching strategy is more favorable in future quantum networks taking into account robustness and cost required when using different types of QSDC schemes.
In this paper, a Quantum Secure Direct Communication (QSDC) network is proposed and investigated. The protocol allows four independent users to exchange their confidential information pairwise, with the help of a central controller that regulates authorization and separation among concurrent communication flows. Quantum channels are used only in the preliminary distribution of the entangled states; afterward, no quantum-encoded message is transmitted. All message extraction is local, through direct measurements. This drastically reduces reliance on quantum transmission, constrains photon-loss effects, minimizes quantum hardware overhead, and increases the achievable message throughput compared to previous QSDC protocols. Given that the protocol utilizes entanglement distribution instead of consecutive quantum modulation, a very promising perspective is opened for scalability in future multi-party quantum communication systems. The simulation results confirm the strong robustness against classical and quantum adversarial strategies, testified by high detection probabilities and abort conditions that prevent information leakage.
Large-scale communication networks, such as the Internet, rely on routing packets of data through multiple intermediate nodes to transmit information from a sender to a receiver. In this paper, we develop a model of a quantum communication network that routes information simultaneously along multiple paths passing through intermediate stations. We demonstrate that a quantum routing approach can in principle extend the distance over which information can be transmitted reliably. Surprisingly, the benefit of quantum routing also applies to the transmission of classical information: even if the transmitted data is purely classical, delocalising it on multiple routes can enhance the achievable transmission distance. Our findings highlight the potential of a future quantum internet not only for achieving secure quantum communication and distributed quantum computing but also for extending the range of classical data transmission.
Quantum secure direct communication (QSDC) offers a practical way to realize a quantum network which can transmit information securely and reliably. Practical quantum networks are hindered by the unavailability of quantum relays. To overcome this limitation, a proposal has been made to transmit the messages encrypted with classical cryptography, such as post-quantum algorithms, between intermediate nodes of the network, where encrypted messages in quantum states are read out in classical bits, and sent to the next node using QSDC. In this paper, we report a real-time demonstration of a computationally secure relay for a quantum secure direct communication network. We have chosen CRYSTALS-KYBER which has been standardized by the National Institute of Standards and Technology to encrypt the messages for transmission of the QSDC system. The quantum bit error rate of the relay system is typically below the security threshold. Our relay can support a QSDC communication rate of 2.5 kb/s within a 4 ms time delay. The experimental demonstration shows the feasibility of constructing a large-scale quantum network in the near future.
A quantum network, which involves multiple parties pinging each other with quantum messages, could revolutionize communication, computing and basic sciences. The future internet will be a global system of various packet switching quantum and classical networks and we call it quantum internet. To build a quantum internet, unified protocols that support the distribution of quantum messages within it are necessary. Intuitively one would extend classical internet protocols to handle quantum messages. However, classical network mechanisms, especially those related to error control and reliable connection, implicitly assume that information can be duplicated, which is not true in the quantum world due to the no-cloning theorem and monogamy of entanglement. In this paper, we investigate and propose protocols for packet quantum network intercommunication. To handle the packet loss problem in transport, we propose a quantum retransmission protocol based on the recursive use of a quantum secret sharing scheme. Other internet protocols are also discussed. In particular, the creation of the logical process-to-process connections is accomplished by a quantum version of the three-way handshake protocol.
The great scientific and technological advances that are being carried out in the field of quantum communications, accompanied by large investment programs such as EuroQCI, are driving the deployment of quantum network throughout the world. One of the final long-term objectives is to achieve the development of a quantum internet that provides greater security in its services and new functionalities that the current internet does not have. This article analyzes the possible integration strategies of already deployed networks or in the process of being deployed in order to reach a future global quantum network. Two strategies based on the SDN paradigm are proposed, based on a hierarchical controller scheme and on a distributed model. Each of these approaches shows pros and cons and could be applicable in different use cases. To define these strategies, the most relevant deployments of quantum communications networks carried out to date has been analyzed, as well as the different approaches for a quantum network architecture and topology, and the various proposed definitions of what quantum internet is and what are the components that would make it up in an ideal scenario. Finally, several detected opportunities and challenges regarding security and technological aspects are presented.
The extensive studies on the quantum communication, which provides a novel means of secure communication, have been carried out in last decades. Among the various types of quantum communication, quantum secure direct communication (QSDC) can securely transmit message directly through a quantum channel. This paper reports a practical scheme of QSDC without quantum memory, taking advantage of the wiretap channel theory and classical coding theory. The proposed approach solves one of the biggest obstacle of practical applications of QSDC, the quantum memory, which is indispensable in original QSDC protocols. The design and detailed scheme for implementation of the proposed protocol are given.