Conclusive bidirectional quantum teleportation of arbitrary unknown single-particle states in amplitude-damping channel

In this paper, two conclusive bidirectional quantum teleportation (BQT) schemes in an amplitude damping channel are put forward. These schemes, respectively, exchange two arbitrary single-qubit states and two arbitrary single-qutrit states between two users, where both users act as senders and receivers. To achieve this, the detailed procedures for using entanglement compensation in an amplitude damped channel to share pure entangled quantum states between two users are first proposed. Then, using the pure entangled four-qubit (or four-qutrit) state shared between the users as a quantum channel, the secret quantum information of each user, i.e. the single-qubit state (or single-qutrit state), is teleported to the other user. This teleportation is designed in such a way that the information can be probabilistically reconstructed by introducing an auxiliary qubit (or qutrit) and executing proper unitary transformations by the receiver. The research results indicate that, whether in single-qubit or single-qutrit state BQT schemes, the success probability of the receiver restoring secret quantum information is determined only by the smaller absolute value of the coefficients characterizing the quantum channel. Additionally, regardless of the noise intensity in the amplitude damping channel, the fidelity of each quantum state transmitted in our BQT schemes can reach 1, which is unattainable in existing BQT schemes based on noisy environments.