Abstract In the 40 years since the BB84 protocol was proposed, the practical progress of quantum communication has been relatively slow, because many key technologies have not yet made breakthroughs. This paper proposes a model that can be supported by existing technologies, that is, three-non quantum communication which has no quantum key distribution, no teleportation, and no information transmission. Its working principle is that Alice uses fiber channel or free space to send polarized entangled photon streams to Bob and has the controllable decoherence of entangled photons with the industrial-grade optoelectronic devices, and her control role is equivalent to information coding to realize communication functions. It also has other characteristics such as no requirement for code rate, single-photon detection, quantum base operations and classical channel, etc. It has a low requirement for light sources and transmission channels and is easy to implement.
Abstract In the 40 years since the BB84 protocol was proposed, the practical progress of quantum communication has been relatively slow, because many key technologies have not yet made breakthroughs. This paper proposes a model that can be supported by existing technologies, that is, three-non quantum communication which has no quantum key distribution, no teleportation, and no information transmission. Its working principle is that Alice uses fiber channel or free space to send polarized entangled photon streams to Bob and has the controllable decoherence of entangled photons with the industrial-grade optoelectronic devices, and her control role is equivalent to information coding to realize communication functions. It also has other characteristics such as no requirement for code rate, single-photon detection, quantum base operations and classical channel, etc. It has a low requirement for light sources and transmission channels and is easy to implement.
Abstract In the 40 years since the BB84 protocol was proposed, the practical progress of quantum communication has been relatively slow, because many key technologies have not yet made breakthroughs. This paper proposes a model that can be supported by existing technologies, that is, three-non quantum communication which has no quantum key distribution, no teleportation, and no information transmission. Its working principle is that Alice uses fiber channel or free space to send polarized entangled photon streams to Bob and has the controllable decoherence of entangled photons with the industrial-grade optoelectronic devices, and her control role is equivalent to information coding to realize communication functions. It also has other characteristics such as no requirement for code rate, single-photon detection, quantum base operations and classical channel, etc. It has a low requirement for light sources and transmission channels and is easy to implement.
After the preceding four introductory chapters, we are finally ready to discuss optical quantum information processing. While in principle quantum communication can be implemented with atoms or electrons, in practice the implementation of choice for long-distance quantum communication will almost certainly be optical. In this chapter, we will develop some of the key topics in quantum communication with single photons, and we will discuss continuous-variable quantum communication in Chapter 8. In some ways, quantum communication is the most technologically advanced part of quantum information processing. Most protocols in this chapter, such as teleportation and cryptography, have been convincingly demonstrated in the lab, and there are already several commercial organizations that sell cryptographic systems based on quantum mechanical principles. In particular, the promise of secure communication with quantum cryptography is one of the driving forces behind the development of single-photon sources and detectors. In this chapter, we first construct several optical representations of the qubit, including polarized photons and time-bin encoding. Since the single-photon implementation of a qubit is central to optical quantum information processing, this constitutes a large part of the chapter. In Section 5.2 we discuss quantum teleportation and entanglement swapping with single photons. We also present a method for entanglement distillation using entanglement swapping. In Section 5.3 we introduce decoherence-free subspaces, which can be used to reduce noise in the transmission of quantum information, and even establish communication channels in the absence of shared reference frames.
Entanglement distribution is a fundamental building block of quantum communication networks, enabling the secure and reliable exchange of quantum information over long distances. Unlike classical communication, quantum networks exploit the unique properties of quantum entanglement to support applications such as quantum key distribution, quantum teleportation, distributed quantum computing, and networked quantum sensing. Although significant progress has been made in recent years, the efficient generation, transmission, and preservation of entangled states remain major research challenges due to photon loss, decoherence, and limitations in current communication infrastructure.This review provides a comprehensive overview of entanglement distribution in quantum communication networks, focusing on the technologies that enable practical implementation and the latest experimental developments. It discusses key approaches for generating and distributing entangled photons through optical fibers, free-space links, and satellite-based communication, together with supporting technologies such as quantum repeaters, quantum memories, and photonic devices. The review also examines recent experimental demonstrations that have advanced long-distance quantum communication while highlighting the technical barriers that must be overcome for large-scale deployment. Finally, emerging applications and future research directions are presented, including the development of scalable quantum networks, the quantum internet, and secure global communication systems. This review aims to provide researchers and students with a clear understanding of the current state of entanglement distribution and its growing role in next-generation quantum communication technologies.
Quantum Key Distribution is a quantum communication technique in which random numbers are encoded on quantum systems, usually photons, and sent from one party, Alice, to another, Bob. Using the data sent via the quantum signals, supplemented by classical communication, it is possible for Alice and Bob to share an unconditionally secure secret key. This is not possible if only classical signals are sent. While this last statement is a long standing result from quantum information theory it turns out only to be true in a non-relativistic setting. If relativistic quantum field theory is considered we show it is possible to distribute an unconditionally secure secret key without sending a quantum signal, instead harnessing the intrinsic entanglement between different regions of space–time. The protocol is practical in free space given horizon technology and might be testable in principle in the near term using microwave technology.
Data transmission has always been vulnerable to eavesdropping.Conventional cryptography has provided security in data communication, however it has some limitations when dealing with passive eavesdropping.Recently, the quantum mechanics has made a remarkable entry in the field of data communication.Now, it is possible to construct cryptographic communication systems which detect unauthorized eavesdropping and guarantee its prevention.Several protocols have been devised to implement such systems e.g., BB84, B92 and EPR.The famous BB84 protocol describes quantum encryption in terms of polarization states of a photon.The secret information is t ransmitted via secure quantum channel followed by a public conversation for verification and reconciliation.The B92 protocol is an extension of BB84 which shows how photons with non-orthogonal states can be used to distribute a secret key.The EPR protocol utilizes an entangled photon pair for encryption-one photon from this pair is transmitted towards the destination while keeping the other at the source; the destination photon describes the state of the source photon, failing to which confirms the intrusion.This paper presents a study of these protocols and a review on the recent developments in the field of secure quantum transmission.
This chapter begins our first exciting application of the postulates of the quantum theory to quantum communication. We study the fundamental, unit quantum communication protocols. These protocols involve a single sender Alice and a single receiver Bob. The protocols are ideal and noiseless because we assume that Alice and Bob can exploit perfect classical communication, perfect quantum communication, and perfect entanglement. At the end of this chapter, we suggest how to incorporate imperfections into these protocols for later study. Alice and Bob may wish to perform one of several quantum informationprocessing tasks, such as the transmission of classical information, quantum information, or entanglement. Several fundamental protocols make use of these resources: 1. We will see that noiseless entanglement is an important resource in quantum Shannon theory because it enables Alice and Bob to perform other protocols that are not possible with classical resources only. We will present a simple, idealized protocol for generating entanglement, named entanglement distribution . 2. Alice may wish to communicate classical information to Bob. A trivial method, named elementary coding , is a simple way of doing so and we discuss it briefly. 3. A more interesting technique for transmitting classical information is superdense coding . It exploits a noiseless qubit channel and shared entanglement to transmit more classical information than would be possible with a noiseless qubit channel alone. 4. Finally, Alice may wish to transmit quantum information to Bob. A trivial method for her to do so is to exploit a noiseless qubit channel. However, it is useful to have other ways for transmitting quantum information because such a resource is difficult to engineer in practice. An alternative, surprising method for transmitting quantum information is quantum teleportation . The teleportation protocol exploits classical communication and shared entanglement to transmit quantum information. Each of these protocols is a fundamental unit protocol and provides a foundation for asking further questions in quantum Shannon theory. In fact, the discovery of these latter two protocols was the stimulus for much of the original research in quantum Shannon theory. One could take each of these protocols and ask about its performance if one or more of the resources involved is noisy rather than noiseless. Later chapters of this book explore many of these possibilities.