Zeng Gui-Hua

A realizable quantum encryption algorithm for qubits

A realizable quantum encryption algorithm for qubits is presented by employing bit-wise quantum computation. System extension and bit-swapping are introduced into the encryption process, which makes the ciphertext space expanded greatly. The security of the proposed algorithm is analysed in detail and the schematic physical implementation is also provided. It is shown that the algorithm, which can prevent quantum attack strategy as well as classical attack strategy, is effective to protect qubits. Finally, we extend our algorithm to encrypt classical binary bits and quantum entanglements.

Four-Party Quantum Broadcast Scheme Based on Aharonov State

In this paper, we propose a solution based on four-qubit Aharonov state to an old problem by using the property of congruence. The proposed scheme may realize the broadcast among four participants, therefore, it makes progress to the three-party broadcast realized previously. Using pairwise quantum channels and entangled qubits, the detection between these players also can be accomplished. Finally, the feasibility of the protocol and the analysis of security are illustrated.

Multiparty Quantum Secret Sharing of Quantum States with Quantum Registers

A quantum secret sharing scheme is proposed by making use of quantum registers. In the proposed scheme, secret message state is encoded into multipartite entangled states. Several identical multi-particle entanglement states are generated and each particle of the entanglement state is filled in different quantum registers which act as shares of the secret message. Two modes, i.e. the detecting mode and the message mode, are employed so that the eavesdropping can be detected easily and the secret message may be recovered. The security analysis shows that the proposed scheme is secure against eavesdropping of eavesdropper and cheating of participants.

Distance Ranging Based on Quantum Entanglement

In the quantum metrology, applications of quantum techniques based on entanglement bring in some better performances than conventional approaches. We experimentally investigate an application of entanglement in accurate ranging based on the second-order coherence in the time domain. By a fitting algorithm in the data processing, the optimization results show a precision of ±200 μm at a distance of 1043.3m. In addition, the influence of jamming noise on the ranging scheme is studied. With some different fitting parameters, the result shows that the proposed scheme has a powerful anti-jamming capability for white noise.

Unsymmetrical Quantum Key Distribution Using Tripartite Entanglement

An unsymmetrical quantum key distribution protocol is proposed, in which Greenberger–Horne–Zeilinger (GHZ) triplet states are used to obtain the secret key. Except the lost qubits due to the unperfectness of the physical devices, the unsymmetrical characteristic makes all transmitted qubits useful. This leads to an excellent efficiency, which reaches 100% in an ideal case. The security is studied from the aspect of information theory. By using the correlation of the GHZ tripartite entanglement state, eavesdropping can be easily checked out, which indicates that the presented protocol is more secure.

Security analysis of continuous-variable quantum key distribution scheme

In this paper security of the quantum key distribution scheme using correlations of continuous variable Einstein–Podolsky–Rosen (EPR) pairs is investigated. A new approach for calculating the secret information rate ΔI is proposed by using the Shannon information theory. Employing an available parameter F which is associated with the entanglement of the EPR pairs, one can detect easily the eavesdropping. Results show that the proposed scheme is secure against individual beam splitter attack strategy with a proper squeeze parameter.

Secure deterministic communication scheme based on quantum remote state preparation

Based on the techniques of the quantum remote state preparation via a deterministic way, this paper proposes a quantum communication scheme to distribute the secret messages in two phases, i.e., the carrier state checking phase and the message state transmitting phase. In the first phase, the secret messages are encoded by the sender using a stabilizer quantum code and then transmitted to the receiver by implementing three CNOT gates. In the second phase, the communicators check the perfectness of the entanglement of the transmitted states. The messages can be distributed to the receiver even if some of the transmitted qubits are destroyed.

Novel Quantum Secret Sharing and Controlled Communication Schemes Based on Einstein–Podolsky–Rosen Correlations

Employing quantum registers, we first proposed a novel (2, 3) quantum threshold scheme based on Einstein–Podolsky–Rosen (EPR) correlations in this letter. Motivated by the present threshold scheme, we also propose a controlled communication scheme to transmit the secret message with a controller. In the communication protocol, the encoded quantum message carried by particles sequence, is transmitted by legitimate communicators.

Quantum quasi-cyclic low-density parity-check error-correcting codes

In this paper, we propose the approach of employing circulant permutation matrices to construct quantum quasicyclic (QC) low-density parity-check (LDPC) codes. Using the proposed approach one may construct some new quantum codes with various lengths and rates of no cycles-length 4 in their Tanner graphs. In addition, these constructed codes have the advantages of simple implementation and low-complexity encoding. Finally, the decoding approach for the proposed quantum QC LDPC is investigated.

Security of quantum key distribution using two-mode squeezed states against optimal beam splitter attack ⁄

For the beam splitter attack strategy against quantum key distribution using two-mode squeezed states, the analytical expression of the optimal beam splitter parameter is provided in this paper by applying the Shannon information theory. The theoretical secret information rate after error correction and privacy amplification is given in terms of the squeezed parameter and channel parameters. The results show that the two-mode squeezed state quantum key distribution is secure against an optimal beam splitter attack.