Quantum entanglement on magnetic materials and superconducting devices

Abstract

In this thesis we present a study of quantum entanglement on magnetic materials and superconducting devices, and we can divide it into two parts. Within the framework of the study of entanglement in molecular magnets, we develop four works. In the first one, we investigate entanglement on compound Na2Cu5Si14O14 and show how the hydrostatic pressure affects entanglement on this compound. In the second and third works, we explore thermal entanglement between spin and angular momentum in a ion rare-earth. In the second one a entanglement witness based on the magnetic susceptibility, which is capable of revealing entanglement between these angular momenta of different nature, is introduced. In the third work we found higher entanglement temperatures than room temperature for promethium and samarium. In the following, in the third work, we use an entanglement witness based on the mean energy and show that the entanglement temperature is found to be thousands of kelvins above room temperature for all light rare earths. In the forth work, we report the use of a dipolar spin thermal system as a quantum channel to perform quantum teleportation. In the second part of this thesis we study the viability of using a superconducting quantum interference device (SQUID) to generate a pair of photons and to transfer entanglement from device to the modes of radiation field. We generate a pair of photons by using a radiation field of a single mode or a coherent state; in both cases we consider that the dynamics of SQUID is such that two of its levels move, i.e., the energies of these levels vary with the time. In addition, the parameters used, such that the coupling constant among the levels and its respective frequencies, are known in the literature. The second viability is the use of this device for transferring entanglement. We consider that the initial state of the system, radiation field plus SQUID, is entangled since two levels of the device are equally populated. This entanglement is transferred to the modes of radiation field corroborate by concurrence