Abstract Quantum secure direct communication is a quantum communication technology that uses quantum states as carriers to transmit information securely and directly, first proposed by a team at Tsinghua University in 2000. Quantum communication broadly refers to information transfer processing tasks accomplished through the transmission of quantum states, which can be categorized into three types based on the content transmitted: quantum key distribution for transmitting random numbers, quantum secure direct communication for transmitting classical information, and quantum teleportation for transmitting quantum information. After more than two decades of development, quantum secure direct communication has matured and entered practical application: a theoretical framework tailored for scenarios with high loss, high noise, and stringent security requirements has been established; experimental demonstrations of quantum direct communication in optical fibers and free space have been completed; three milestone systems for quantum secure direct communication at the metropolitan, intercity, and network levels have been built; and successful trials have been conducted in various scenarios such as 5G private networks and banking applications. Quantum secure direct communication offers multiple applications: it prevents information leakage by detecting eavesdropping, ensuring information security; identifies exposed locations by monitoring surveillance activities, providing technical support for preventing targeted eliminations and safeguarding commanders' personal safety; and detects intrusion and tampering behaviors, offering novel protection for cybersecurity. Currently, quantum direct communication has been incorporated into relevant planning documents in China, the European Union, and the United States, and is undergoing rapid development. This article briefly outlines the historical development, fundamental principles, research advancements, and future prospects of quantum direct communication.
Abstract Quantum secure direct communication is a quantum communication technology that uses quantum states as carriers to transmit information securely and directly, first proposed by a team at Tsinghua University in 2000. Quantum communication broadly refers to information transfer processing tasks accomplished through the transmission of quantum states, which can be categorized into three types based on the content transmitted: quantum key distribution for transmitting random numbers, quantum secure direct communication for transmitting classical information, and quantum teleportation for transmitting quantum information. After more than two decades of development, quantum secure direct communication has matured and entered practical application: a theoretical framework tailored for scenarios with high loss, high noise, and stringent security requirements has been established; experimental demonstrations of quantum direct communication in optical fibers and free space have been completed; three milestone systems for quantum secure direct communication at the metropolitan, intercity, and network levels have been built; and successful trials have been conducted in various scenarios such as 5G private networks and banking applications. Quantum secure direct communication offers multiple applications: it prevents information leakage by detecting eavesdropping, ensuring information security; identifies exposed locations by monitoring surveillance activities, providing technical support for preventing targeted eliminations and safeguarding commanders' personal safety; and detects intrusion and tampering behaviors, offering novel protection for cybersecurity. Currently, quantum direct communication has been incorporated into relevant planning documents in China, the European Union, and the United States, and is undergoing rapid development. This article briefly outlines the historical development, fundamental principles, research advancements, and future prospects of quantum direct communication.
Quantum Communication technology, which achieved many unprecedented breakthroughs in the past several years,is arousing the attentions from related authoritative bodies and the field of communication research with its particular characteristic of perfect security in information transmission. Firstly, in this paper, the course of development and milestones of quantum communication theory and technologies are reviewed. And the state-of-the-art of domestic and foreign quantum communication technologies are summarized, with the conclusion that the technology tends to be mature, and China stands in the front row of the world both in quantum communication theory and experiments. Then, the definition and model of the ideal quantum communication system are discussed and engineering scenarios of quantum communication system based on optical fiber channel and free space optical channel are provided. The security and communication ability now achieved by these scenarios are analyzed, drawing such conclusion that quantum communication technologies has both high practical value and broad development space. Finally, realistic application scenarios and future application prospect of quantum communication technology are presented, in consideration of the requirements and current technology levels.
Quantum secure direct communication (QSDC) is one of the most important branches of quantum communication. In contrast to the quantum key distribution (QKD) which distributes a secure key between distant parties, QSDC directly transmits secret message instead of sharing key in advance. To establish a secure QSDC protocol, on the one hand, the security of the quantum channel should be confirmed before the exchange of the secret message. On the other hand, the quantum state should be transmitted in a quantum data block since the security of QSDC is based on the error rate analysis in the theories on statistics. Compared with the deterministic quantum key distribution (DQKD) which can also be used to transmit deterministic information, QSDC schemes do not need extra classical bits to read the secret message except for public discussion. In this article, we introduce the basic principles of QSDC and review the development in this field by introducing typical QSDC protocols chronologically. The first QSDC protocol was proposed by Long and Liu, which can be used to establish a common key between distant parties. In their scheme, the method for transmitting quantum states in a block by block way and in multiple steps was proposed and the information leakage before eavesdropping detection was solved. Subsequently, Deng et al. presented two pioneering QSDC schemes, an entangled-state-based two-step QSDC scheme and a single-photon-state-based quantum one-time pad scheme, in which the basic principle and criteria for QSDC were pointed out. From then on, many interesting QSDC schemes have been proposed, including the high-dimension QSDC scheme based on quantum superdense coding, multi-step QSDC scheme based on Greenberger-Horne-Zeilinger states, QSDC scheme based on quantum encryption with practical non-maximally entangled quantum channel, and so on. We also introduce the anti-noise QSDC schemes which were designed for coping with the collective-dephasing noise and the collective-rotation noise, respectively. In 2011, Wang et al. presented the first QSDC which exploited the hyperentangled state as the information carrier and several QSDC schemes based on the spatial degree of freedom (DOF) of photon, single-photon multi-DOF state and hyperentanglement were proposed subsequently. In addition to the point-to-point QSDC schemes, we also review the QSDC networks. Finally, a perspective of QSDC research is given in the last section.
The development of modern computer technologies endangers the confidentiality of information, which is usually ensured by traditional cryptographic means. This circumstance forces us to look for new methods of protection. In view of modern trends, quantum cryptography methods can become such alternatives, which allow solving a number of important cryptographic problems, for which the impossibility of solving using only classical (that is, non-quantum) communication has been proven. Quantum cryptography is a branch of quantum informatics that studies methods of protecting information by using quantum carriers. The possibility of such protection is ensured by the fundamental laws of quantum mechanics. One of the promising directions of quantum cryptography is Quantum Secure Direct Communication (QSDC) that offers secure communication without any shared key. A characteristic feature of this method is the absence of cryptographic transformations, accordingly, there is no key distribution problem. The purpose of this work is a general overview of quantum cryptography protocols, finding their weak points for further development and improvement, as well as identifying vulnerabilities to different attacks. The article analyzes new methods and protocols, as well as presents their advantages and disadvantages. Based on partial generalizations of theoretical provisions and practical achievements in the field of quantum cryptography, a generalized classification was developed. By comparing various factors of the protocols, and their resistance to certain cyberattacks, we have the opportunity to identify several problems in this field and expand the possibilities for choosing appropriate methods for building modern quantum information protection systems. In accordance with this, conclusions were presented regarding the use of protocols and increasing the level of their effectiveness.
Quantum communication provides an absolute security advantage, and it has been widely developed over the past 30 years. As an important branch of quantum communication, quantum secure direct communication (QSDC) promotes high security and instantaneousness in communication through directly transmitting messages over a quantum channel. The full implementation of a quantum protocol always requires the ability to control the transfer of a message effectively in the time domain; thus, it is essential to combine QSDC with quantum memory to accomplish the communication task. In this Letter, we report the experimental demonstration of QSDC with state-of-the-art atomic quantum memory for the first time in principle. We use the polarization degrees of freedom of photons as the information carrier, and the fidelity of entanglement decoding is verified as approximately 90%. Our work completes a fundamental step toward practical QSDC and demonstrates a potential application for long-distance quantum communication in a quantum network.
Quantum secure direct communication (QSDC) transmits information securely through a quantum channel, distinct among various quantum communications. Proposed by me and Liu 20 years ago, QSDC has now been developed to a stage that is ready for practical application. QSDC advances classical communication of reliable communication over a noisy channel, which is guaranteed by Shannon's theory, to a higher plane of both secure and reliable communication over a noisy channel even in the presence of eavesdropping. Here we briefly introduce the basic principles, the techniques for practical applications.
Quantum communication is a rapidly evolving field that leverages quantum physics to enable secure and efficient information exchange. A cornerstone of quantum cryptography is Quantum Key Distribution (QKD), a secure key exchange mechanism that ensures the confidentiality of transmitted data by employing the no-cloning theorem and the uncertainty principle of quantum mechanics. This study explores key aspects of quantum networks and communication, including quantum states, QKD, and quantum cryptographic protocols, with a focus on photon polarization states and entangled qubits as fundamental building blocks of quantum information. Additionally, two well-established quantum cryptographic protocols, BB84 and E91, are analyzed for their principles and advantages in secure communication. However, challenges such as quantum state loss in communication channels hinder the long-distance transmission of quantum information. To address these issues, error detection, measurement, and correction techniques are investigated, with quantum error correction methods playing a crucial role in mitigating noise and imperfections, ensuring accurate quantum information transmission, and enhancing the overall efficiency of quantum communication systems. Beyond conventional networks, quantum communication holds vast potential for cybersecurity applications, paving the way for next-generation secure communication frameworks.