Quantum teleportation via thermal entanglement in squeezed spin states

Abstract

This article investigates thermal entanglement and quantum teleportation in a bipartite system composed of two spin-\(\frac{1}{2}\) qubits, exposed to an external magnetic field along the Z-axis, within the framework of the squeezed spin model. We employ concurrence to quantify both the thermal entanglement in our system and the entanglement of the replicated output state in a quantum teleportation protocol through this system. Thus, we adopt fidelity to evaluate the quality of teleportation. It is shown that at the system’s ground state, a pure state favors maximal entanglement, while a mixed state leads to an absence of entanglement regardless of the magnetic field. At very low temperatures, increasing the magnetic field induces transitions from the entangled state to a separable state, but this transition is modulated by the intensity of interactions in the XY-plane. The intensities of interactions along the X- and Y-axes are studied to understand their effect on the system’s entanglement. Two spin squeezing mechanisms, one-axis twisting and two-axis counter twisting, are compared, revealing that two-axis counter twisting offers better entanglement. Finally, we explore quantum teleportation through squeezed spin states, demonstrating its feasibility with high fidelity at high temperatures and without a magnetic field, provided that the intensities of interactions in the XY-plane are negligible. By increasing the intensities \(\mu \) and \(\chi \), fidelity improves. Intriguingly, our analysis suggests that quantum teleportation, with increased fidelity, is achievable only with the one-axis twisting spin squeezing mechanism, remaining out of reach for two-axis counter twisting.