The path selection is a key problem in noisy quantum Ad Hoc network. In this paper, we propose a relay strategy to find the optimal relay path in Ad Hoc network with a noise model of amplitude damping channel. Based on the analysis of the noise influence on quantum entanglement relay path, we give the calculation method of the entanglement fidelity of a relay path and use this fidelity as the main criterion to choose an optimal relay path. To avoid the congestion of the good relay nodes, we use the number of free entanglement connections to control the choice of a relay path. The details of the relay protocol are given, including the information tables in the quantum nodes, the structure of the protocol messages, the quantum path finding procedures and the path maintenance process. The performance simulation shows our strategy has the ability to find the optimal quantum relay path with better quantum transmission quality.
The path selection is a key problem in noisy quantum Ad Hoc network. In this paper, we propose a relay strategy to find the optimal relay path in Ad Hoc network with a noise model of amplitude damping channel. Based on the analysis of the noise influence on quantum entanglement relay path, we give the calculation method of the entanglement fidelity of a relay path and use this fidelity as the main criterion to choose an optimal relay path. To avoid the congestion of the good relay nodes, we use the number of free entanglement connections to control the choice of a relay path. The details of the relay protocol are given, including the information tables in the quantum nodes, the structure of the protocol messages, the quantum path finding procedures and the path maintenance process. The performance simulation shows our strategy has the ability to find the optimal quantum relay path with better quantum transmission quality.
The optimal relay path calculation and selection are important factors to affect the performance of quantum communication network. Current researches seldom consider the quantum path selection in real noisy environments. One of the difficult problems is how to analyze the influence of the noise on the quantum communication in multi-hop channels. This paper aims to solve the path selection problem of the quantum teleportation network in noisy environments. The process of entanglement swapping in the phase damping channel is first studied with an example of two-hop quantum channel, whose damping factors are p1 and p2. The entanglement states |φ> 12+ and |φ> 34+ are distributed separately in each hop. After the entanglement swapping, the density matrix of the entanglement state of photon 1 and photon 4 is obtained by performing a partial trace over the environment. Then, the Bures fidelity of this entanglement is calculated. After that, we define the path equivalent damping factor to describe the characteristic of the two-hop noisy quantum relay path. With an equivalent calculation method, the results above can be generalized to multi-hop channel. The path equivalent damping factor of the multi-hop amplitude damping channel is also obtained. According to these results, we propose an optimal relay protocol for the quantum teleportation network with the criterion of path equivalent damping factor, which means that a relay path with the minimum path equivalent damping factor can obtain the highest teleportation fidelity. The types and parameters of the messages used in the protocol are given. The processes of the relay protocol are described specifically, including neighbor finding, quantum link noise measurement, and quantum link status transmission. An improved Dijkstra algorithm is used in the optimal path calculation. Furthermore, because the entanglement resources maintained in the quantum nodes are limited and may be exhausted in superior quantum links, we propose a resource reservation method to avoid the failure of the relay path setup. Theoretical analysis and simulation show that our method can obtain a lower average equivalent damping factor and higher teleportation fidelity. It can also be seen that increasing the number of the entanglement resources will raise the performance of the quantum network, however, it brings higher cost and complexity. Therefore, the entanglement resources maintained in the quantum nodes must be configured reasonably according to the network scale, the cost, the time delay and the need of the users.
A concept of wireless ad hoc quantum communication network is proposed and a routing protocol is designed for wireless quantum communicaiton network with complex structure. The routing protocol is on-demand and the routing metric is based on the number of entangled particle pairs. The node that wants to send information carried by quantum state can initiate a route request and establishment procedure. The destination node chooses path by the routing metric and sends route reply message along the selected path. During the information transmission, if the quantum channel or the wirless channel between any neighbors in the selected path is broken, a route discovery process is reinitiated to set up a new route. Nodes in the selected path use a both-end approximation algorithm to establish a quantum channel. After the quantum channel is established, the quantum state is transferred by quantum teleportation and the information transfer between any two nodes in wireless ad hoc quantum communication network is finished.
Quantum key distribution (QKD) technology, a secure communication method based on the fundamental principles of quantum mechanics, enables secure key sharing between two communication nodes. In theory, the unconditional security of the QKD protocol depends on ideal quantum devices, classical devices, and perfect random number generation. However, there are significant differences between the devices in the actual system and the ideal conditions, and QKD systems are inevitably affected by various noises that seriously affect the anti-interference performance and key generation efficiency of the system. In this article, the authors analyze the anti-interference performance of the QKD protocol in noisy environments and propose a QKD network routing algorithm based on trust relay. This algorithm effectively reduces the bit error rate during network transmission and improves the efficiency of key distribution by optimizing the selection strategy of relay nodes and key forwarding paths.
Abstract This paper addresses the optimization of on-demand routing protocols for quantum wireless Ad Hoc network. This paper proposes an optimal quantum route metric algorithm that integrates quantum route metric and classic route metric to select a better route path for quantum communication. The paper also improves the route discovery protocol by proposing a "reverse synchronization method" which means after the route request is completed, the quantum entanglement channel is established synchronously when the reverse path is established. This method, better than general methods which builds quantum channels after the forward path establishment, reduces the time and the numbers of messages for quantum channel establishment, thus improving the efficiency. Accordingly, this paper elaborates the specific methods, procedures and related upgrading message formats involved in quantum route discovery, quantum channel establishment and quantum information transmission of on-demand routing protocols for quantum wireless Ad Hoc network. The advantage of the "reverse synchronization method" in reducing the time and the numbers of messages for quantum channel establishment is verified through analysis on protocol performance.
Since the good application of quantum mechanism in the field of communication, quantum secure communication has become a research hotspot. The existing quantum secure communication protocols usually assume that the quantum channel is noise-free. But the inevitable quantum noise in quantum channel will greatly interferes the transmission of quantum bits or quantum states, seriously damaging the security and reliability of the quantum system. This paper analyzes and discusses the performance of a χ state based steganography protocol under four main quantum noises, i.e., Amplitude Damping (AD), Phase damping (Phs), Bit Flip (BF) and Depolarizing (D). The results show that the protocol is least affected by amplitude damping noise when only the sender's first transmission in quantum channel is affected by quantum noise. Then, we analyze the performance of the protocol when both the sender's two transmissions are affected by quantum noise, and find that the specific combination of different noises will increase the performance of the protocol in quantum noisy channel. This means that an extra quantum noise can be intentionally added to quantum channel according to the noise intensity, so that the protocol can improve performance under the influence of quantum noises. Finally, the detailed mathematical analysis proves the conclusions.
We consider two qubit teleportation via quantum channel affected by amplitude damping noise. Addressing the same problem, X. Hu, Y. Gu, Q. Gong and G. Guo [Phys. Rev. A 81, 054302, (2010)] recently showed that in presence of noise, subjecting more qubits in quantum channel to amplitude damping can increase the fidelity of teleportation protocol. However, in this paper, by making some adjustments on quantum channel, we obtain teleportation fidelity which is even higher than one in the case of X. Hu et al. Moreover, our strategy is simpler than quantum distillation and compared to using weak measurement, it is deterministic. Furthermore, explicit analysis of fidelity is provided, we show that in general, choosing appropriate quantum channel enhances the ability of teleportation better and negates the fact that more amplitude damping noise more quality.