Multi-party quantum secret sharing based on logical GHZ-type states against collective noise

In this paper, we discussed the local preparation methods of two types of multi-qubit logical GHZ-type states using controlled quantum gates, and drew the corresponding quantum circuits. Subsequently, we investigated the measurement-related properties of logical GHZ-type state and thus proposed two multi-party quantum secret sharing schemes against collective-dephasing and collective-rotation noise, respectively. Further, we demonstrated that the schemes can effectively resist some familiar attack strategies. Finally, we analyzed the quantum efficiency of our schemes and made a comprehensive comparison with previous similar schemes.

Cryptanalysis and improvement of the robust quantum dialogue protocols based on the entanglement swapping between any two logical Bell states and the shared auxiliary logical Bell state

As we know, it does not allow that a secure quantum communication protocol has the information leakage problem. Unfortunately, we find that there is the information leakage problem in the two quantum dialogue (QD) protocols which are respectively based on entanglement swapping between two logical Bell states under the collective-dephasing noise and the collective-rotation noise. To mend this loophole, they are masterly improved. It is proven that the improved QD protocols are without information leakage problem. Incidentally, they have some other obvious advantages compared to the previous ones.

The security analysis of E91 protocol in collective-rotation noise channel

The bit error in quantum communication is mainly caused by eavesdropping and noise. However, most quantum communication protocols only take eavesdropping into consideration and ignore the result of noise, making the inaccuracy situations in detecting the eavesdropper. To analyze the security of the quantum E91 protocol presented by Ekert in collective-rotation noise channel, an excellent model of noise analysis is proposed. The increment of the qubits error rate (ber) is used to detect eavesdropping. In our analysis, eavesdropper (Eve) can maximally get about 50% of the key from the communication when the noise level approximates to 0.5. The results show that in the collective-rotation noise environment, E91 protocol is secure and the raw key is available just as we have knew and proved. We also presented a new idea in analyzing the protocol security in noise channel.

Two robust quantum key agreement protocols based on logical GHZ states

Based on logical GHZ states and logical Bell states, two robust quantum key agreement protocols are proposed, which can be immune to the collective-dephasing noise and the collective-rotation noise, respectively. The delayed measurement technique ensures that two participants can fairly negotiate a shared key and any one of them cannot successfully perform the participant attacks. The two protocols are congenitally free from the Trojan horse attacks and they can resist against other outsider attacks with the help of the decoy state technology. Moreover, they have no information leakage problem and achieve high qubit efficiency.

Fault-tolerant symmetrically-private information retrieval

We propose two symmetrically-private information retrieval protocols based on quantum key distribution, which provide a good degree of database and user privacy while being flexible, loss-resistant and easily generalized to a large database similar to the precedent works. Furthermore, one protocol is robust to a collective-dephasing noise, and the other is robust to a collective-rotation noise.