Electro-optic level-crossing effect

W. E. Baylis

M R Ghafarzadeh, Mohammad Kazem Tavassoly

Abstract Recently in [Phys. Rev. Lett. 114, 080503 (2015)] an electro-opto-mechanical converter has been used to evaluate microwave-optical entanglement, applicable in the quantum illumination techniques at microwave frequencies. Choosing this frequency domain is due to the fact that, microwaves have generally a more suitable spectral region for target detection than light waves. In this paper we aim to investigate the effect of nonlinear Kerr and cross-Kerr media on the microwave-optical entanglement degree in an electro-opto-mechanical transducer. We evaluate some key measures of the system, i.e., entanglement metrics, logarithmic negativity, coherent information and quantum discord. Our analysis demonstrates that, adding Kerr and cross-Kerr terms to the Hamiltonian of the electro-opto-mechanical system increases the entanglement metric, logarithmic negativity and quantum discord by approximately 3 to 4 times and the coherent information increases slightly, whenever the system possesses strong optical-mechanical coupling, low optical dissipation or both conditions. Conversely, when the system possesses weak optical-mechanical coupling, high optical dissipation or both conditions, it leads to weakening/death of all above-considered criteria. The constructive effect of Kerr media on the above quantumness signs makes the system more beneficial for quantum illumination purposes, which is an important factor in the quantum information science and technologies.

Minwei Jiang, Hao Zhai, Chunyu Jiang +9 more

Accurate characterization of atomic vapor cells is crucial for enhancing the sensitivity of miniature atomic magnetometers. In this study, a fast and efficient approach is developed to characterize relaxation properties of the inner surface of the 87Rb micro-electro-mechanical systems (MEMS) vapor cell. Based on the zero-field level crossing effect, the transverse relaxation rate was experimentally determined, and the depolarization coefficient of 0.097 for atom-wall collisions in the 87Rb MEMS vapor cell was obtained. The experiments demonstrated that the alkali-wall collision relaxation gradually dominates the depolarization of the 87Rb ensemble as the radius of the vapor cell decreases. This research provides a quantitative method to evaluate the effectiveness of the MEMS vapor cell anti-relaxation coatings and offers the design inspiration for MEMS atomic vapor cells from the perspective of relaxation characterization. It is beneficial for the development of weak magnetic field detections such as biomagnetism detection in ambient environments.

Yasunori Tokuda, Yuji Abe

We demonstrated the optical bistable responses of the self-electro-optic effect device without applying any external bias. The function was realized by taking advantage of the significant electric-field dependence of both intensity and wavelength of an excitonic absorption peak, which is related to a resonance of electron levels in an asymmetric coupled quantum well structure. The successful result suggests that it is possible to create an all-optical bistable device with nonsegmented planar structure.