arXiv subjects

Nancy Ghangas

Publications and source records attributed to Nancy Ghangas.

3 recordsLinked to original sources

arXiv2025

Entanglement dynamics of Multi-Level Atoms embedded in Photonic Crystals: Leveraging Resonant Dipole-Dipole Interactions and Quantum Interference

We present a comprehensive investigation of entanglement dynamics in multi-level V-type atomic systems embedded within photonic crystals. We mainly focus on the synergistic roles of resonant dipole-dipole interactions and quantum interference through analytical modeling and numerical simulations using the Schrodinger equation. Key findings reveal that resonant interaction dominates when the interatomic distance is comparable to the localization length of photon-atom bound states lying in the bandgap region. For atoms with anti-parallel dipole orientations, both initially entangled and separable states exhibit robust entanglement preservation due to strong collective interactions. Conversely, when dipoles are oriented orthogonally, initially entangled states exhibit unique oscillatory patterns in their entanglement dynamics. This effect arises from the formation of dark states due to destructive interference within the structured photonic environment, with resonant dipole-dipole interactions sustaining non-Markovian dynamics. We further demonstrate that positioning the atomic excited states deeper within the photonic bandgap accelerates the decay of entanglement oscillations due to the exponential suppression of resonant energy exchange mediated by evanescent modes. Our analysis establishes resonant dipole-dipole interactions and quantum interference as potential tools for tailoring entanglement dynamics, paving the way for controlled quantum coherence in photonic crystal platforms.

quant-ph↗

arXiv2025

Dynamics of Light Localization via Coherent Control: The Interplay of Transmission, Absorption and Disorder in Photonic Crystals

This study investigates the interplay between structural disorder, absorption, and Lyapunov exponent dynamics to exploit localization phenomena in photonic crystals with engineered defect layers. We generate disorder by introducing random refractive index variations in one of the bilayers, while the application of a control field to $\Lambda$-type atoms within a central defect layer enables dynamic tuning of the effective refractive index of crystal. We have employed traditional transfer matrix method to demonstrate transmission, Lyapunov exponents and absorption in the crystal. Through coherent control, we dynamically tune absorption, revealing sharp contrasts in band gap and band edge regions. while Lyapunov exponents, quantifying localization lengths, exhibit a consistent scaling across both band gap and band edge frequencies, and this behavior remains robust even in the presence of disorder. Hence, distinct localization mechanisms emerge at bandgap and band-edge frequencies. Bandgap localization arises from optical mode confinement and resonant alignment of atomic transitions with the probe field while band edge localization stems from a synergy of loss-difference-induced trapping and Anderson like disorder effects. Notably, while disorder weakens confinement localization in the band gap, it actually strengthens localization at the band edges. These results deepen the understanding of light-matter coupling in disordered photonic systems and provide a framework for designing reconfigurable optical devices with tailored localization properties.

physics.optics↗

arXiv2024

Coherent control of nonreciprocal optical properties of the defect modes in 1D defective photonic crystals with atomic doping

We investigate the spectral properties of photonic crystals, lacking parity-time (PT) symmetry, using scattering matrix formalism. We show using the symmetry properties of matrices that a defective photonic crystal, doped with three-level atoms, breaks PT symmetry. For the two defect modes lying in the bandgap region, both the reflection and the absorption become nonreciprocal, while the transmission remains reciprocal. We show that the relevant energy spectra do not exhibit exceptional points, thereby invalidating its necessity to achieve nonreciprocity in reflection and absorption. We further demonstrate how this nonreciprocity can be coherently controlled using the driving field and dissipation rates of the atoms.

physics.optics↗