Coherent polarization driven by external electromagnetic fields

A. I. Alekseev, Ashat M. Basharov

S. Mouslih, Zakaria Dahbi, M. Jakha +3 more

Abstract Graphene, with its two-dimensional carbon structure, exhibits unique quantum properties that are crucial for quantum computing. In this paper, we investigate the influence of an external electromagnetic field on quantum coherence and entanglement between two qubits in graphene lattices. Our findings show that an electromagnetic field with high field strength (ξ 0 ∼ 50 meV2) and low frequency (ω = 0.117 eV) significantly enhances quantum entanglement and coherence, even at elevated temperatures (T ∼ 20 meV). By adjusting the frequency and the field strength, these quantum effects can be preserved long enough at high temperatures. Furthermore, circular polarization of the electromagnetic field is found to be more effective than linear and elliptical polarizations in optimizing these effects. These results highlight the critical role of electromagnetic fields in enhancing quantum properties, potentially paving the way for advancements in quantum computing and related technologies.

Eugene Y. C. Lu

H. Jafarzadeh

A four-level inverse Y-type atomic system with a microwave-driven field contained in a unidirectional ring cavity is proposed for controlling the optical bistability behavior with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field derived another atomic transition. Under the steady state condition, we can control the occurrence of the optical bistability by modulating different parameters, such as the probe detuning ( ), the electronic cooperation parameter (C), the magnitude of electromagnetic field (B), and left- or right- handed circular polarized beams. Also, it is found that the stable output field of the optical cavity can be controlled by adjusting the intensity of the input field. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by the magnitude of the external magnetic field. Also, it is shown that the optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams. In this paper, in the case of the steady-state and transient response, we investigated the effect of external magnetic field on optical bistability of a four-level atomic system in the presence of strong coherent laser beam. Here, a laser probe signal consists of two left- and right- handed circular polarized beams which are interacted by two different transitions. The optical system provides a new experimental method to test optical bistability theory.

Riccardo A. Calvani, Renato Caponi, CISTERNINO F +2 more

Abdelghani El Houri, Ayyoub El Mouatasim, Aziz Khribach +3 more

Abstract This study explores the temporal evolution of local quantum Fisher information and coherence in a graphene monolayer subjected to a polarized electromagnetic field, revealing significant effects driven by system parameters. In the absence of the field, the analysis highlights the crucial role of the initial state's purity in the dynamics of both local quantum Fisher information and coherence, influencing their amplitude and decay over time. Introducing an electromagnetic field unveils a strong dependence of these quantities on the polarization and amplitude parameters. For linear polarization, local quantum Fisher information and coherence reach their maximum values at specific field phases, while for circular polarization, the system's response becomes more complex, exhibiting pronounced variations and a gradual decrease in coherence at higher field intensities. These findings emphasize the importance of controlling electromagnetic parameters to manipulate quantum information in graphene and open up new prospects for applications in quantum electronics and information processing.