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Results in Physics

Spontaneously generated coherence in a four-level atomic system under induced chirality: Quantum control of the Casimir force

Rashid Ahmad, Hazrat Ali, Iftikhar Ahmad, Nadia Boutabba

Published Mar 1, 2023• 13 citations

Abstract

In this work, we investigate the coherent control of the Casimir force (CF) in a four-level atomic system under electromagnetically induced chirality. Therefore, we consider two parallel slabs of finite length in a quantum vacuum composed of ensembles of cesium vapor atoms in a four-level double Λ-type atomic configuration. By the use of the quantum interference (QI) effect which arises from the cross-coupling between the different spontaneous emission pathways, we demonstrate that it is possible to fully control the CF in the system via the spontaneously generated coherence (SGC) and the relative phase between the electromagnetic fields. In fact, we first show that the chirality in the atomic system can be induced by the SGC and the probe detuning, satisfying the passivity conditions. Next, we manipulate and control the QI in the system by changing the angle between the dipole moments, as the SGC is sensitive to their relative orientations. Besides, we explore the dependence of the Casimir interaction energy on the relative phase of the control fields. Finally, we observe that the Casimir interaction energy can be switched from negative to positive for a specific given phase value.

DOI: 10.1016/j.rinp.2023.106314

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In this work, we investigate the coherent control of the Casimir force (CF) in a four-level atomic system under electromagnetically induced chirality. Therefore, we consider two parallel slabs of finite length in a quantum vacuum composed of ensembles of cesium vapor atoms in a four-level double Λ-type atomic configuration. By the use of the quantum interference (QI) effect which arises from the cross-coupling between the different spontaneous emission pathways, we demonstrate that it is possible to fully control the CF in the system via the spontaneously generated coherence (SGC) and the relative phase between the electromagnetic fields. In fact, we first show that the chirality in the atomic system can be induced by the SGC and the probe detuning, satisfying the passivity conditions. Next, we manipulate and control the QI in the system by changing the angle between the dipole moments, as the SGC is sensitive to their relative orientations. Besides, we explore the dependence of the Casimir interaction energy on the relative phase of the control fields. Finally, we observe that the Casimir interaction energy can be switched from negative to positive for a specific given phase value.

An electromagnetically induced phase grating controlled by spontaneous generated coherence (SGC) in a four-level N-type atomic system is studied. The results indicate that the diffraction efficiency of the phase grating is dramatically enhanced due to the existence of SGC, and an efficient electromagnetically induced phase grating can be obtained. A novel result is considerable improvement of the intensity of higher-order diffractions via relative phase between applied laser fields. Furthermore, it is found that the frequency detuning of the switching and coupling fields with the corresponding atomic transition, incoherent pumping, and the interaction length can improve the efficiency of the phase grating in the present atomic model.

The control of light-matter interaction at the quantum level usually requires coherent laser fields. But already an exchange of virtual photons with the electromagnetic vacuum field alone can lead to quantum coherences, which subsequently suppress spontaneous emission. We demonstrate such spontaneously generated coherences (SGC) in a large ensemble of nuclei operating in the x-ray regime, resonantly coupled to a common cavity environment. The observed SGC originates from two fundamentally different mechanisms related to cooperative emission and magnetically controlled anisotropy of the cavity vacuum. This approach opens new perspectives for quantum control, quantum state engineering and simulation of quantum many-body physics in an essentially decoherence-free setting.

The effect of spontaneously generated coherence (SGC) on spontaneous emission and dynamical evolution of a microwave-driven four-level atomic system is studied. Interesting phenomena due to SGC, such as spectral-line narrowing, spectra-line enhancement, spectral-line suppression, and fluorescence quenching, are shown in the spontaneous emission spectra, which can be effectively modulated by amplitude and phase of the microwave field. Due to SGC, the total populations are partly, even completely, trapped in upper levels in steady state, the decay time of which is sensitive to the phase of the microwave field. In the dressed state picture, multiple SGC arise during the process of three close-lying states decaying to the same state. The corresponding experiment to observe the expected phenomena related to SGC can be more conveniently realized in atoms, since no rigorous conditions are required and the amplitude and phase of the microwave field can be conveniently controlled.

In this work, the effects of quantum interference and spontaneously generated coherence (SGC) are theoretically analyzed in a four-level system of a

^{87}\mathrm{Rb}

atom. For the effects of SGC, we find that a new kind of electromagnetically induced transparency channel can be induced due to destructive interference, and the nonlinear Kerr absorption can be coherently narrowed or eliminated under different strengths of the coupling and switching fields.

This paper investigates the microwave-synchronized fine-tuning of electromagnetically induced chirality in a four-level atomic system. The system is driven by two optical fields and one microwave field in an extended double-Λ configuration. Under low-density conditions, the system exhibits double electromagnetically induced transparency (EIT), which can be controlled by adjusting the amplitudes of coupling fields and the phase of the microwave field. We show that, under suitable conditions of the coupling field amplitudes and microwave phase, the double EIT reduces to a single EIT as a result of multi-path quantum interference. These optical processes are elucidated using dressed-state analysis. In this context, we also examine the magnetic susceptibility and chiral coefficients. Furthermore, by incorporating local-field corrections for a high-density medium, we demonstrate broadband absorption-free negative refraction of the probe field, where neither the effective permittivity nor the permeability is required to be simultaneously negative.

This paper investigates the effects of spontaneously generated coherence(SGC) on the probe absorption in the Y-type four-level atomic system driven by three fields.It finds that the probe absorption at the resonance center shows the different phenomena with the SGC effects.When SGC produces the destructive interference on the probe absorption,the absorption at the resonance center is reduced with the SGC enhancement and the gain appears there.When SGC produces the constructive interference on the probe absorption,the absorption at the resonance center is enhanced with the SGC enhancement.That is electromagnetically induced absorption(being abbreviated EIA);the intensity of double electromagnetically induced transparency(being abbreviated EIT);at both sides of the resonance is increased,and the windows get wider.At the same time,the linewidth of the absorption at the resonance center becomes narrow and the transparent windows at both sides of the resonance get wider when the spontaneous decay rate of energy levels |3〉→|2〉 and 4〉→|2〉 is decreased at the ratio of the spontaneous decay rate of energy levels |3〉→|2〉 and |4〉→|2〉 being constant.