Search

In this paper, a controlled quantum dialogue protocol is designed based on five-qubit entangled states. One five-qubit entangled state can be used to exchange one communicant’s two private bits with the other communicant’s two private bits under the control of an honest supervisor. Security analysis turns out that it can overcome the information leakage problem and can resist the active attacks from an outside attacker. The designed protocol only needs single-particle measurements and Bell state measurements, both of which can be realized with current technologies.

Recently, Wang et al. put forward a high-capacity three-party quantum secret sharing (QSS) protocol with single photons in both the polarization and the spatial-mode degrees of freedom (Int J Theor Phys (2013) 52:1043–1051). In this paper, the communication capacity of Wang et al.’s QSS protocol is improved by providing more composite unitary operations for Alice’s encoding. Compared with Wang et al.’s QSS protocol, the improved protocol doubles the communication capacity of the photon for sharing Alice’s secret bits. The improved protocol only needs two-qubit single-photon states in both the polarization and the spatial-mode degrees of freedom and single-photon measurements. Compared with the QSS protocols based on entangled states and entangled state measurements, the improved protocol is more feasible.

In this paper, we construct a semi-quantum dialogue (SQD) protocol by using Bell entangled states as the initial quantum resource. The information leakage problem is prevented by utilizing the entanglement correlation of two particles from one Bell entangled state. The security towards active attacks from an outside Eve is guaranteed by twice security checks and one classical one-time pad encryption process. The proposed SQD protocol can be realized in experiment with present quantum technologies. Compared with the traditional quantum dialogue (QD) protocols without information leakage, the advantage of the proposed SQD protocol lies in that it doesn’t require both communicants to possess quantum capabilities.

A quantum dialogue scheme based on entanglement swapping and Hadamard operation via cavity QED is proposed, which effectively uses the evolution law of atom in cavity QED. The proposed scheme uses Bell states and GHZ states as quantum resource and only needs single-atom measurements. The proposed scheme is secure against active attacks from an eavesdropper and can transmit 4 secret bits per round communication.

Quantum private comparison (QPC) aims to determine whether two parties’ private inputs are equal or not without leaking out their genuine contents. At present, there is seldom QPC protocol which uses single photons as quantum resource. In this paper, we are devoted to converting Zhang et al.’s three-party quantum summation (QS) protocol based on single photons (Int. J. Quantum Inf. 15(2), 1750010, 2017) into the corresponding two-party QPC protocol with single photons. The correctness and the security of the proposed QPC protocol with single photons can be guaranteed. The proposed QPC protocol is naturally free from Trojan horse attacks because of its single directional particle transmission mode.

Recently, Jia et al. proposed the quantum private comparison protocol with the genuine four-particle entangled states (Jia et al., Int. J. Theor. Phys. 51(4), 1187–1194 (2012)). Jia et al. claimed that in this protocol, TP cannot obtain Alice and Bob’s secrets and only knows their comparison result. However, in this paper, we demonstrate that if TP is a genuine semi-honest third party, he can totally obtain Alice and Bob’s secrets by launching a particular intercept-resend-measure attack. After suggesting the intercept-resend-measure attack strategy from TP first, we put forward one corresponding improvement to prevent this attack.