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Quantum error correction technology is a vital method to eliminate noise during the operation of quantum computers. To solve the problem caused by noise, in this paper, reinforcement learning is used to encode defects of Semion codes, and the experience replay technique is used to realize the design of decoder. Semion codes are quantum topological error correction codes with the same symmetry group Z2 as Kitaev toric codes, we used the topological characteristics of error correction codes to map qubits to multi-dimensional space, and error correction accuracy of the decoder is calculated to be 77.5%. Calculate the threshold of topological quantum Semion code, depending on the code distance, resulting in different thresholds, pthreshold = 0.081574 when the code distance is d = 3, 5, 7 and threshold pthreshold = 0.09542 when the code distance is d = 5, 7, 9. And we design the Q-network to optimize the cost of quantum circuit gates and compare the size of the cost reduction under different thresholds. Reinforcement learning is an important method for designing Semion code decoders and optimizing numerical values, providing more general error models and error correction codes for future machine engineering decoders.

In order to protect the privacy of query users and databases, a quantum private query protocol under noisy conditions is proposed and studied. It is a one-way quantum protocol that not only protects user privacy, but also prevents eavesdropping. And in the protocol initialization phase, the identity is verified by the quantum entanglement pair. Through key distribution, a user only knows a part of the key, and the accuracy of the original key needs to be considered. Channel noise directly affects the transmission result of quantum bits and reduces the transmission accuracy. In addition, the presence of eavesdropper Eve may also affect the transmission of qubits. The receiver corrects the error by using quantum error correction technology, thereby improving the efficiency of protocol communication.

With the rapid development of information technology (IT), E-mail has become an important communication tool between human beings. Meanwhile, E-mail safety becomes increasingly important because of its universal applications. In order to overcome shortages of classical E-mail encryption, an E-mail encryption protocol based on quantum teleportation was proposed. It makes quantum encryption of E-mails during sending and receiving processes by taking advantages of entanglement and nonclonability of quantum, thus ensuring safety and reliability of E-mail transmission.

Information security is the cornerstone and lifeblood of national security in the information society, and anonymous quantum communication is one of the important ways to protect information security. Using quantum walk randomness to effectively solve sensitive problems such as leakage of identity information. In this paper, an anonymous communication scheme based on quantum walks on the Cayley graph is proposed. First, both parties in the communication hide their identity information, and the sender Alice anonymously selects the receiver Bob through logic or operation. Secondly, the trusted third party and the communicating parties use the BB84 protocol to generate and distribute the security key. Alice encrypts the information sequence according to the security key to obtain the blind information; Bob uses the joint Bell state measurement and security key to sign and the trusted third party verifies the signature information. Third, the trusted third party calculates the position probability distribution function of Bob’s quantum walk via the Fourier transform, converts the position information corresponding to the maximum probability into a confirmation frame and sends it to Alice; Alice uses the quantum compression algorithm by decreasing dimensions to reduce the number of transmitted information bits(the length of the information bit can be reduced by up to 37.5%) and uses the security key to complete the information encryption and then transmit the information to the location indicated by the confirmation frame. Bob uses quantum walks to search the location node to obtain the transmission information and complete the anonymous quantum communication. Finally, the security analysis of the scheme is carried out, and the numerical simulation results of the Cayley graph of 200 nodes are given. At the 10-step walk, the maximal probability of the 6th node is 45.31%. According to the simulation results, the probability that Bob is eavesdropped on the specific location at his 10-step walk during the communication of this scheme is approximately 6 × 10–7%, so the receiver can avoid the identity information from the eavesdropping with a high probability, and the quantum network anonymity protocol is not broken.

A $��N$ formalism is used to study the non-Gaussianity of the primordial curvature perturbation on an uniform density hypersurfaces generated by the warm inflation for the first time. After introducing the framework of the warm inflation and the $��N$ formalism, we obtain an analytic expression for the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in slow roll approximation, and find that the $��N$ formalism gives a very good result. We analyse the magnitude of $f_{NL}$ and compare our result with those of the standard inflation. Then we discuss two concrete examples: the quartic chaotic model and the hilltop model. The quartic potential model can again be in very good agreement with the Planck results in the warm inflationary scenario, and we give out the concrete results of how the nonlinear parameter depends on the dissipation strength of the warm inflation and the amounts of expansion. We find that the range of the nonlinear parameters in these two cases are both well inside of the allowed region of Planck., 9 pages, 5 figures

Quantum communication protects information security by means of the basic laws of quantum mechanics and has aroused the wide public interest over the recent years.Quantum communication consists of quantum key distribution, quantum secure direct communication,quantum teleportation,quantum dense coding,and quantum secret sharing.The purpose of quantum key distribution,quantum secure direct communication and quantum secret sharing is to protect the security of information and thus they are called quantum cryptography.In quantum key distribution and secret sharing,data transmitted in the quantum channel are random keys rather than information,and the information is sent through another classical communication.The direct communication of information through quantum channel is realized in quantum secure direct communication.In this paper,we present a protocol for quantum communication by using quantum teleportation (QCUQT),and analyze it in detail.First,we answer the question whether QCUQT is a type of quantum secure direct communication.In QCUQT,only computational basis states are teleported,and both the Bell-basis measurement and the single particle operations can be simplified.It is found that the QCUQT is equivalent to the combined process of a quantum key distribution plus a classical communication rather than a type of quantum secure direct communication.In order to read out the information in the quantum channel,classical communication is required by QCUQT.Some misunderstandings about QCUQT are discussed and clarified in the paper.It was mistaken that the transmission of quantum state in QCUQT is irrelevant to the channel noise nor the distance between two parties,and QCUQT can even be used to realize superluminal communication.Our study shows that the QCUQT is affected by the medium and also the distance between two parties,and it does not have an advantage over quantum key distribution,and cannot realize quantum superluminal communication either.We also compare the QCUQT with quantum key distribution,quantum secure direct communication,and classical one-time-pad in several aspects such as the nature of the data in quantum channel,the way of reading out the key,the way of transmitting messages,and the amount of data carried in the process.We also point out the characteristics of each type of communication.It is concluded that single-photon quantum key distribution is easier to realize than QCUQT because single-photon detection and generation are easier to realize than the Bell-basis measurement and generation of EPR pairs.In particular,we discuss the use of these protocols in space communication and it is suggested that quantum secure direct communication be a better choice in outer-space quantum communication because of the low loss in quantum channels there.

The direct communication protocol of quantum network over noisy channel is proposed and investigated in this study. In communication process, all quantum nodes share multiparticle Greenberger-Horne-Zeilinger (GHZ)-states. The sending node takes the GHZ-state particle in the hand as the control qubit and the particle for sending secret information as the target qubit, which carries out the CNOT gate operation for the control and target qubit. Each receiving node takes the GHZ-state particle in the hand as the control qubit and the particle of the received secret information as the target qubit, in which the CNOT gate operation is repeated to obtain the secret information that contains the bit error. Each receiving node uses the extracted part of qubits as the checking qubits, and then corrects the bit-flip errors using parity check matrix together with the rest part of qubits. As a result, all receiving nodes obtain rectified secret information. In addition to the high security analysis, this study also presents the detailed analyses of the throughput efficiency and the communication performance.