In this paper, we present an innovative quantum dialogue protocol for multiple users to get private information from each other without leaking any information. In our protocol, a semi-honest third party (TP) is introduced to assist multiple participants for exchanging their private information. Specifically, exploiting multi-particle entangled GHZ states as the information carriers, we investigate how to implement the multi-party quantum dialogue protocol and perform the equivalence comparison. We also analyze the security of our protocol. Compared with previous quantum dialogue protocols, our protocol is more flexible and more efficient.
In this article, we consider stochastic master equations describing the evolution of a multiqubit system interacting with electromagnetic fields undergoing continuous-time measurements. By considering multiple
z-type (Pauli
zmatrix on different qubits) and
x-type (Pauli
xmatrix on all qubits) measurements and one control Hamiltonian, we provide general conditions on the feedback controller and the control Hamiltonian ensuring almost sure exponential convergence to a predetermined Greenberger–Horne-Zeilinger (GHZ) state, which is assumed to be a common eigenstate of the measurement operators. We provide explicit expressions of feedback controllers satisfying such conditions. We also consider the case of only
z-type measurements and multiple control Hamiltonians. We show that local stability in probability holds true, however due to the absence of random displacements generated by
x-type measurements, the reachability of a neighborhood of a predetermined GHZ state is not clear. In this case, we provide a heuristic discussion on some conditions which may ensure asymptotic convergence toward the target state. Finally, we demonstrate the effectiveness of our methodology for a three-qubit system through numerical simulations.