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Advanced Devices & Instrumentation

Free-Space Quantum Secure Direct Communication: Basics, Progress, and Outlook

Dong Pan, Xiaotian Song, Gui‐Lu Long

Published Jan 1, 2023• 73 citations
Publisher

Abstract

Quantum secure direct communication (QSDC) leverages quantum states to transmit information securely and reliably over a noisy, lossy, and wiretapped quantum channel. It has been proven to be information-theoretically secure. Recent experiments show that QSDC can enable long-distance communication and large-scale networking with existing technologies. In particular, free-space QSDC has the unique advantages and prospects for practical large-scale application. Here, we review the QSDC basics and the progress of free-space QSDC. The feasibility of satellite-based QSDC and the future directions of free-space QSDC are discussed. We propose a practical and feasible route that can make immediate application of QSDC in real life.

DOI
10.34133/adi.0004

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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 exploits the principles of quantum mechanics in the transmision and processing of information. It has the advantages of high security and high capacity. Quantum secure direct communication (QSDC) is a new mode of quantum coomunication by Long and Liu in which secret information can be transmitted securely and directly over quantum channels. Since it was first proposed in 2000, QSDC has been developed very fast. In this review, we will explain the basic principles of QSDC and describe some typical QSDC protocols. Toward the end of the review, we will introduce the new trends in the QSDC research and give a perspectiv of QSDC research.
Quantum communication has developed into various classes, including recent novel quantum secure direct communication (QSDC) schemes. The QSDC method transmits confidential information directly between parties over a quantum channel without requiring a shared private key. Even though QSDC offers improved security guarantees and reduces the possibility of security loopholes, practical applications such as secure information rates, long-distance quantum communication and networking, and integration with existing technologies still requires improvement. Meanwhile, advances in artificial intelligence (AI) and machine learning (ML) continue to revolutionize several fields, including quantum communication, which is challenging to control and maintain effectively for optimum performance. Various ML techniques have been applied to quantum communication systems to mitigate noise-induced errors, analyze communication protocols, and optimize secure key generation rates. While this represents a significant development and has the potential to address challenges facing QSDC applications, we are unaware of ML applications specifically improving QSDC systems. Due to this, we bring forward the discussion and unveil the critical need to integrate AI and ML models into QSDC to enhance security, improve fault tolerance, increase communication distance, and optimize resource allocation. Consequently, this work establishes a practical framework for unlocking the full potential of QSDC protocols and, more broadly, practical quantum communication.
There are substantial problems in sending quantum information safely over free-space channels because of air turbulence, diffraction, beam divergence, and noise. This study offers an extensive performance evaluation of quantum computing-based security methods utilised in free-space communication systems, specifically emphasising Quantum Secure Direct Communication (QSDC) and Quantum Key Distribution (QKD) protocols. The purpose of this work is to examine the attainable secret-key generation rates, assess the robustness of quantum security protocols in practical free-space environments, and contrast their effectiveness in preventing eavesdropping and signal degradation. This research employs quantum optics, turbulence theory, and quantum information theory to examine the performance constraints of continuous-variable (CV) coherent-state protocols amid fluctuating turbulence intensities. The suggested analytical approach simulates both fading and non-fading atmospheric channels to calculate essential rates and quantum bit error rates (QBER) for free-space quantum secure direct communication (QSDC) systems. Experimental findings and simulation outcomes indicate that free-space quantum channels can provide high-rate and long-distance secure communication when optimized using pilot-guided coherent-state protocols. The review shows how QSDC is better than regular QKD since it lets messages be sent directly without pre-shared keys. It also talks about how useful it may be for secure communication networks between satellites and between satellites and the earth. The paper closes by delineating the primary research deficiencies and suggesting avenues for improving protocol efficiency, error rectification, and turbulence mitigation in forthcoming global quantum communication systems.
Quantum secure direct communication (QSDC) based on entanglement can directly transmit confidential information. However, the inability to simultaneously distinguish the four sets of encoded entangled states limits its practical application. Here, we explore a QSDC network based on time-energy entanglement and sum-frequency generation. In total,15 users are in a fully connected QSDC network, and the fidelity of the entangled state shared by any two users is >97%. The results show that when any two users are performing QSDC over 40 km of optical fiber, the fidelity of the entangled state shared by them is still >95%, and the rate of information transmission can be maintained above 1 Kbp/s. Our result demonstrates the feasibility of a proposed QSDC network and hence lays the foundation for the realization of satellite-based long-distance and global QSDC in the future.
Abstract The practical implementation of quantum secure direct communication (QSDC) will undoubtedly be a milestone in the development of quantum cryptography. Research is in its final phase and focuses on developing secure protocols that consider realistic constraints and are feasible within the current state of technology. Three well‐known protocols ae compared, Ping‐Pong, Two‐Step and Deng‐Long, in the context of the level of security offered and the challenges related to their implementation. This work explains how the evolution of QSDC protocols from a purely quantum formulation to hybrid classical‐quantum solutions based on the Wyner wiretap channel model can solve most problems encountered. The work aims to inform scientists in other fields of quantum information processing about the latest advances in QSDC. The attached appendix introduces basic concepts for readers unfamiliar with this research area.