Quantum information science has extensive applications in various research fields, such as information, physics and computer science. It is well known that the quantum properties of a system exhibit many unique advantages in the security of information transmission and processing, computation, and the improvement of channel capacity. Quantum information includes several research fields, for example, quantum communication, quantum computing and so on. In the past 30 years, the development of quantum communication, quantum computing and quantum information processing has made great progress in both theory and experiments. As a fundamental resource for quantum information processing, entanglement is a key element for many applications, such as quantum key distribution, quantum teleportation, quantum dense coding, quantum secure direct communication and quantum metrology. Because of the weak interaction with the environment and the degrees of freedom, entangled photons are the excellent candidates as the quantum-information carrier. Several remarkable experiments have been performed with the photonic entanglement. However, it is necessary to share a pair of entangled photons between the communicating parties in advance in these quantum information processes. Furthermore, the application of hyperentanglement, the entanglement of photon pairs simultaneously existing in more than one degree of freedom, has been widely studied for the reason that it can improve the channel capacity of quantum communications and implement hyperparallel computing, such as the quantum error-correcting code, quantum repeater and deterministic entanglement purification. Moreover, the quantum logic gates play an essential role in quantum information processing which attracts much attention on the designing of the quantum logic gates. Depending on the coherent dynamics of the cavity quantum electrodynamical system, deterministic quantum gate operations between the quantum systems can be realized. Here in this review, by considering high-dimensional quantum systems, several high-dimensional quantum protocols are presented. They can greatly improve the capacity of quantum channel and noise immunity, which exhibits potential applications in quantum information processing. This review describes the development of quantum computing and quantum information processing using hyperentanglement. And the entangled photons in single degree of freedom and multi-degrees of freedom are used to illustrate the two-dimensional and high-dimensional quantum information processing schemes. Finally, the latest progress and further applications of quantum computing and quantum information processing are introduced.
Quantum information science has extensive applications in various research fields, such as information, physics and computer science. It is well known that the quantum properties of a system exhibit many unique advantages in the security of information transmission and processing, computation, and the improvement of channel capacity. Quantum information includes several research fields, for example, quantum communication, quantum computing and so on. In the past 30 years, the development of quantum communication, quantum computing and quantum information processing has made great progress in both theory and experiments. As a fundamental resource for quantum information processing, entanglement is a key element for many applications, such as quantum key distribution, quantum teleportation, quantum dense coding, quantum secure direct communication and quantum metrology. Because of the weak interaction with the environment and the degrees of freedom, entangled photons are the excellent candidates as the quantum-information carrier. Several remarkable experiments have been performed with the photonic entanglement. However, it is necessary to share a pair of entangled photons between the communicating parties in advance in these quantum information processes. Furthermore, the application of hyperentanglement, the entanglement of photon pairs simultaneously existing in more than one degree of freedom, has been widely studied for the reason that it can improve the channel capacity of quantum communications and implement hyperparallel computing, such as the quantum error-correcting code, quantum repeater and deterministic entanglement purification. Moreover, the quantum logic gates play an essential role in quantum information processing which attracts much attention on the designing of the quantum logic gates. Depending on the coherent dynamics of the cavity quantum electrodynamical system, deterministic quantum gate operations between the quantum systems can be realized. Here in this review, by considering high-dimensional quantum systems, several high-dimensional quantum protocols are presented. They can greatly improve the capacity of quantum channel and noise immunity, which exhibits potential applications in quantum information processing. This review describes the development of quantum computing and quantum information processing using hyperentanglement. And the entangled photons in single degree of freedom and multi-degrees of freedom are used to illustrate the two-dimensional and high-dimensional quantum information processing schemes. Finally, the latest progress and further applications of quantum computing and quantum information processing are introduced.
Photon system is a promising candidate for quantum information processing, and it can be used to achieve some important tasks with the interaction between a photon and an atom (or a artificial atom), such as the transmission of secret information, the storage of quantum states, and parallel quantum computing. Several degrees of freedom (DOFs) of a photon system can be used to carry information in the realization of quantum information processing, such as the polarization, spatial-mode, orbit-angular-momentum, time-bin, and frequency DOFs. A hyperparallel quantum computer can implement the quantum operations on several DOFs of a quantum system simultaneously, which reduces the operation time and the resources consumed in quantum information processing. The hyperparallel quantum operations are more robust against the photonic dissipation noise than the quantum computing in one DOF of a photon system. Hyperentanglement, defined as the entanglement in several DOFs of a quantum system, can improve the channel capacity and the security of long-distance quantum communication, and it can also be conductive to completing some important tasks in quantum communication. Hyperentangled Bell-state analysis is used to completely distinguish the 16 hyperentangled Bell states, which is very useful in high-capacity quantum communication protocols and quantum repeaters. In order to depress the effect of noises in quantum channel, hyperentanglement concentration and hyperentanglement purification are required to improve the entanglement of the quantum systems in long-distance quantum communication, which is also very useful in high-capacity quantum repeaters. Hyperentanglement concentration is used to distill several nonlocal photon systems in a maximally hyperentangled state from those in a partially hyperentangled pure state, and hyperentanglement purification is used to distill several nonlocal photon systems in a high-fidelity hyperentangled state from those in a mixed hyperentangled state with less entanglement. In this reviewing article, we review some new applications of photon systems with multiple DOFs in quantum information processing, including hyperparallel photonic quantum computation, hyperentangled-Bell-state analysis, hyperentanglement concentration, and hyperentanglement purification.
Abstract Quantum communication has made great breakthroughs in recent years. Because of its characteristics for strict information security transmission and high speed, it has received attention from related research fields around the world. This paper briefly reviews the progress in the field of quantum computing and communication. The basic functions of quantum mechanics related to the quantum communication are first introduced, including qubit, logic gates, postulates, polarization and quantum entanglement. Then the applications of quantum communication are discussed including teleportation, cryptography and quantum networks. Finally, advantages and disadvantages for the current applications are analyzed and the challenges remained in the current research are demonstrated.
"The field of quantum information science promises incredible enhancements in computing, metrology, simulation, and communication, but the challenge of creating, manipulating, and measuring the large quantum states has limited current implementations of such techniques. Such limitations affect photonic quantum information in particular, because photons lack the strong nonlinear interactions required for building up many-particle entangled states and performing multi-photon gates; nevertheless, because photons are currently the only ""flying qubit"", i.e., qubits that are mobile, they are a required resource for quantum communication protocols. One strategy to partially mitigate this limitation is to encode multiple entangled qubits on the different degrees of freedom of a single pair of photons. Such ""hyperentangled"" quantum states may be created with enough qubits to enable a whole new class of quantum information experiments. Furthermore, while nonlinear interactions are required to implement multi-qubit gates between qubits encoded on different particles, such gates can be implemented between qubits encoded on the same particle using only linear elements, enabling a much broader class of measurements. We use hyperentangled states to implement various quantum communication and quantum metrology protocols. Specifically, we demonstrate that hyperentangled photons can be used to increase the classical channel capacity of a quantum channel, transport quantum information between two remote parties efficiently and deterministically, and efficiently characterize quantum channels. We will discuss how to produce, manipulate, and measure hyperentangled states and discuss how entanglement in multiple degrees of freedom enables each technique. Finally, we discuss the limitations of each of these techniques and how they might be improved as technology advances."
Quantum entanglement is a peculiar phenomenon in quantum information science, characterized by nonclassical correlations between quantum states of subsystems in a quantum system. Since the proposal of the Einstein-Podolsky-Rosen (EPR) paradox by Einstein, Podolsky, and Rosen, quantum entanglement has sparked intense debates on local realism. Bell’s inequality experiment established the nonlocality of quantum mechanics. Currently, high-dimensional quantum entanglement of both deterministic and random states can be realized in systems such as photons and cold atoms. Technologies such as quantum teleportation, quantum teleportation, quantum computing, and others rely on quantum entanglement to achieve effects beyond classical limitations. Current research focuses on the implementation of macroscopic quantum entanglement and its significance in fundamental problems of quantum mechanics. Quantum entanglement opens up a new paradigm for information processing with broad application prospects. It is necessary to conduct in-depth research on the nature of quantum entanglement and its advantages in information processing. This paper reviews the theoretical foundations of quantum entanglement, methods of generation and detection, and research progress in its applications in the field of quantum information. It discusses the important applications of quantum entanglement in quantum communication, computing, and sensing and provides an outlook on the future development prospects of quantum entanglement technologies.
In recent years, quantum computing and quantum information science have become one of the most important and attractive research areas in a variety of disciplines, e. g., mathematics, information science, physics, chemistry, etc 1 .These new kinds of technologies are predicted to be much more advantageous compared with the classical computers and classical information science and the benefit obtained by these technologies is assumed to be beyond measure in our every-day life.For instance, quantum computers are predicted to be able to solve mathematical problems that today's fastest computers could not solve in years.In particular, entanglement or entangled state plays a key role for quantum computing and quantum information processing.For example, arbitrary quantum states of two-level system can be teleported through classical communication with the help of maximally entangled Bell state from one place to other macroscopic distant places (quantum teleportation) 2 , which has no counterpart in classical mechanics.As opposed to the quantum teleportation, classical information can be teleported by using the maximally entangled Bell state (superdense coding) 3 .Needless to say, entanglement is also an essential ingredient in quantum computing 1 .At present, theoretical investigations of the mechanism of quantum computing and quantum information science have become mature although some of the important theoretical problems, e. g., definition of entanglement degree of multipartite systems, have not yet been solved and are still controversial.Yet, one can say that we are now reaching a stage of experimental realizations of quantum computing and quantum information processing proposed and investigated theoretically and numerically.To apply quantum computing and quantum information processing to realistic quantum systems, a number of microscopic quantum systems have been proposed.Just to mention a few, cavity quantum electrodynamics (cavity QED) 4 , trapped ions 5 -7 , neutral atoms trapped in optical lattices 8 , nuclear magnetic resonance (NMR) 9, 10 , superconducting circuits 11 , silicon-based nuclear spin 12 , diamond-based quantum computer 13,14 are some of the promising candidates of quantum computing devices.However, investigation of utilization of molecular internal degrees of freedom for quantum computing and quantum information science, in particular, electronic, vibrational, and rotational degrees of freedom, is still in its infancy.Although molecules are also quantum systems, very few chemists have yet examined how to use molecular internal degrees of www.intechopen.comwww.intechopen.
Quantum technologies harness the properties of controlled quantum mechanical systems for applications in computation, communication and metrology, and enable us to further our understanding of fundamental physics. Quantum hardware is designed to manipulate complex and fragile many-particle quantum states, which requires exquisite control machinery, advanced software and near-complete isolation from the surrounding environment. With sufficient capabilities, quantum computers with large registers of quantum bits will perform classically intractable calculations such as quantum chemistry simulations. Quantum key distribution will provide completely secure communications across the world and quantum metrology will enable measurement precision beyond today's capabilities. While quantum technologies are far from surpassing classical hardware today, the vision and potential impact has sparked a world-wide research effort, both theoretical and experimental, to develop a quantum computer. The most sophisticated current quantum technologies have control over small numbers of quantum bits and are limited by environmental decoherence processes. While progress in developing quantum hardware is ongoing, designing and demonstrating new algorithms and protocols for quantum information is a thriving research field. Photonics provides an ideal platform for small-scale proof-of-concept quantum experiments, which are the focus of this thesis. In the coming decades, we will see the realisation of quantum hardware capable of applications that outperform any classical computer. In this thesis, I present several protocols and algorithms for quantum information science and technology, which are implemented in quantum photonic experiments. The applications of these works include robust quantum tomography, quantum state relocation, quantum enhanced data recovery and probing fundamental causality in quantum mechanics. The works presented here are based on two photon experiments from a prototypical spontaneous parametric down-conversion source, which provides an excellent test-bed for quantum information experiments. Photons can be used to encode quantum information in a range of different degrees of freedom. This versatility, along with compatibility with existing technology gives photonics a great advantage in the development of quantum hardware.