Entanglement in composite systems due to external influences

Autor(es)

Gitman, D. M. ^{[1, 2, 3, 4]} ; Meireles, M. S. ^[1] ; Levin, A. D. ^[1] ; Shishmarev, A. A. ^[1] ; Castro, R. A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Phys, Sao Paulo - Brazil

^[2] PN Lebedev Phys Inst, Moscow - Russia

^[3] Tomsk State Univ, Tomsk - Russia

^[4] Rua Matao 1371, BR-05508090 Butanta, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: International Journal of Modern Physics A; v. 33, n. 21 JUL 30 2018.
• Citações Web of Science: 0

Resumo

In this paper, we consider two examples of an entanglement in two-qubit systems and an example of entanglement in quantum field theory (QFT). In the beginning, we study the entanglement of two spin states by a magnetic field. A nonzero entanglement appears for interacting spins. When the coupling between the spins is constant, we study the entanglement by several types of time-dependent magnetic fields. In the case of a constant difference between z components of magnetic fields acting on each spin, we find several time-dependent coupling functions J[t) that also allow us to analyze analytically and numerically the entanglement measure. Considering two photons moving in an electron medium, we demonstrate that they can be entangled in a controlled way by applying an external magnetic field. The magnetic field affecting electrons of the medium affects photons and, thus, causes an entanglement of the photon beams. The third example is related to the effect of production of electronpositron pairs from the vacuum by a strong external electric field. Here, we have used a general nonperturbative expression for the density operator of the system under consideration. Applying a reduction procedure to this density operator, we construct mixed states of electron and positron subsystems. Calculating the von Neumann entropy of such states, we obtain the loss of information due to the reduction and, at the same time, the entanglement measure of electron and positron subsystems. This entanglement can be considered as an example of an entanglement in QFT. (AU)

• Processo FAPESP: 16/03319-6 - Métodos não perturbativos em teoria quântica e em TQC e aplicações deles aos problemas de física atuais
• Beneficiário: Dmitri Maximovitch Guitman
• Modalidade de apoio: Auxílio à Pesquisa - Temático