In order to study system of quantum communication, a scheme of quantum switch based on optical switch is presented, which is the node of quantum communication network. The quantum switch is mainly made up of optical crossing module, switch controller module and in-out module. It builds the photon link between sender and receiver of quantum communication network, and provides quantum channel for transferring quantum information between them. The experiment bed of this quantum switch is established, and the test result with weak optical resource indicates that this quantum switch can be used for quantum communication network and can also realize the function of quantum communication network.
In order to study system of quantum communication, a scheme of quantum switch based on optical switch is presented, which is the node of quantum communication network. The quantum switch is mainly made up of optical crossing module, switch controller module and in-out module. It builds the photon link between sender and receiver of quantum communication network, and provides quantum channel for transferring quantum information between them. The experiment bed of this quantum switch is established, and the test result with weak optical resource indicates that this quantum switch can be used for quantum communication network and can also realize the function of quantum communication network.
This paper puts forward a quantum signaling switch model. The quantum signaling switch consists of a classical information control module, an exchange control module and a quantum exchange module. Classical control module transmits the initial entangled state information to the entanglement measurement and switching unit and updates the routing information. Exchange control module will choose the path, and is ready for the distribution channel of the entanglement photons. The quantum exchange module generates quantum entanglement pairs, measures the Bell state and achieves entanglement swapping. Quantum signaling switches can realize multi-user communication and local area network communication. Through the performance analysis and simulation of the switch, the results show that the switch is simple in structure, secure and easy to expand; also the time delay is small. This will be helpful for the construction of the quantum communication network.
Quantum switch is a primitive element in quantum network communication. In contrast to previous switch schemes on one degree of freedom (DOF) of quantum systems, we consider controlled switches of photon system with two DOFs. These controlled photon switches are constructed by exploring the optical selection rules derived from the quantum-dot spins in one-sided optical microcavities. Several double controlled-NOT gate on different joint systems are greatly simplified with an auxiliary DOF of the controlling photon. The photon switches show that two DOFs of photons can be independently transmitted in quantum networks. This result reduces the quantum resources for quantum network communication.
Quantum key distribution (QKD) is a key technology widely used in quantum communication technology, which can achieve unconditionally secure information transmission. At present, the quantum-classical fusion is often used to construct QKD networks, thus enhancing the security level of the current communication network. In addition, the design of the switching node structure of the optical network is related to the planning and deployment of the entire communication network, which helps to build a flexible and scalable communication network. However, in the quantum-classical fusion network, due to the extremely weak quantum signal, it is susceptible to the crosstalk from the classical signal and the phase drift caused by the change of external environment in the transmission process. In this paper, a multi-layer optical network switching node based on the quantum-classical fusion is designed to enable QKD to be integrated into existing classical networks. The node uses conventional device to enable the isolation of quantum signals from classical and synchronization signals to reach more than 30 dB, and to increase the capacity of the switching node with flexibility and scalability.
Quantum entanglement swapping can be used to establish reliable quantum remote transmission channel so as to realize transmission of quantum states. However, the highly stable quantum network is required in the quantum channels when using quantum entanglement swapping, otherwise it will waste a lot of entanglement resources. In order to save entanglement resources, we have to put forward a kind of quantum communication network transmission protocol based on packet switching, according to the theory of quantum teleportation. Firstly, the principle of packet switching in computer network is introduced. Next we describe the implementation process of quantum network transmission protocols which are based on entanglement swapping and packet switching. We then analyze the reliability, security and utilization rate of entanglement of the protocol we have proposed. And after that the quantitative relationship about the number of entanglement quantum states, the number of routers and link error rates are calculated. Finally, we compare these two transmission protocols. Simulation results show that the number of entanglement for these two protocols is equal without consideration of the link errors. When taking them into account, the packet switching transmission protocol can save numbers of entanglement resources obviously. In addition, with the increase of number of routers and the rise in link error rates, the quantum communication network transmission protocol based on packet switching will need less entanglement resources than that based on entanglement swapping. Therefore, when the quantum transmission network is not stable, the packet switching transmission protocol has a better transmission performance, and it can be applied to the future construction of quantum network.
A scheme of long-distance quantum communication system based on entangled photon pairs is presented,which utilize entanglement as its essential resource.This entanglement enables phenomena such as quantum teleportation and perfectly secure quantum communication.The quantum repeater extends the length of the entangled photon pairs with high fidelity,the entanglement of photons between sender and receiver is built by entanglement swapping and entanglement purification.The quantum information is transferred by the principle of quantum teleportation.Performance analysis results show that the throughput quantum communication system of increases greatly with higher probabilities with which entanglement is built between sender's photons and receiver's photons.The transmitting distance of the quantum signal was determined by the series of the quantum repeater nodes.
Quantum teleportation is one of the most basic quantum protocols, which transfers an unknown quantum state from one location to another through local operation and classical communication by using shared quantum entanglement without physical transfer of the information carrier. And it has been widely used in various quantum information protocols such as entanglement swapping, quantum repeaters, quantum gate teleportation, quantum computation based on measurement, and quantum teleportation networks, which have important application value in quantum computation and quantum information. Quantum teleportation is a naturally bipartite process, in which an unknown quantum state can only be transmitted from one node to another. With the further development of quantum information research, it is necessary to transfer quantum states or quantum information among more and more nodes. Multipartite quantum protocols are expected to form fundamental components for larger-scale quantum communication and computation. A bipartite quantum teleportation should be extended to a multipartite protocol known as a quantum teleportation network. In this paper, a multifunctional quantum teleportation network is proposed theoretically. We first propose a special method of constructing four-partite quantum resources in continuous variables (CVs), and based on this, construct two different types of CV quantum teleportation networks. One type of network contains just one quantum teleportation process consisting of a sender, a receiver and two controllers. In this type of network, the unknown quantum state can be recovered at any other node according to the requirement after the measurement in the input node, which enriches the transfer direction and transfer mode of the unknown quantum state. And meanwhile, the two controllers can control the transfer of a quantum state from the sender to the receiver by restricting the sender and receiver’s access to their information, which makes the quantum teleportation network controllable. The other type of network has two quantum teleportation processes, each containing only a sender, a receiver and no controllers, which increases the number of quantum states that can be transmitted. Then we analyze the dependence of the fidelity of each quantum teleportation network on different physical parameters, and compare the characteristics, advantages and disadvantages among different types of quantum teleportation networks. The scheme for constructing a multifunctional quantum teleportation network in this paper shows some advantages, such as the greater number of quantum nodes, diversity of types, simple operation procedure. And all these advantages provide a broader application prospect for establishing larger and more complex quantum information networks in the future and quicken the pace of the application of quantum information.