arXiv subjects

Muhib Ullah

Publications and source records attributed to Muhib Ullah.

4 recordsLinked to original sources

arXiv2025

Photonic scattering in 2D waveguide QED: Quantum Goos-H\"anchen shift

Quantum emitters coupled to traveling photons in waveguides, known as waveguide quantum electrodynamics (WQED), offer a powerful platform for understanding light-matter interactions and underpinning emergent quantum technologies. While WQED has been extensively studied in one dimension, two-dimensional (2D) WQED remains largely unexplored, where novel photonic scattering phenomena unique to higher dimensions are expected. Here, we present a comprehensive scattering theory for 2D WQED based on the Green function method. We show that the mean displacement between emitted and injected photons serves as a quantum analogue of the Goos-H\"anchen shift. When a photon is injected into a single off-centered port, the quantum Goos-H\"anchen (QGH) shift can be enhanced in backward scattering under resonant conditions with subradiant states. When a photon is injected into the center port, there is no QGH shift due to the mirror symmetry of structure. However, for multiple-port injection with transverse momentum, the QGH shift is recovered and proportional to the derivative of phase with respect to transverse momentum. Unlike the classical Goos-H\"anchen shift, these effects can be flexibly tuned by the injected photon's frequency. Our work provides a general framework for exploring and manipulating photonic scattering in complex WQED networks.

quant-ph↗

arXiv2025

Dynamics of Quantum Entanglement Between Photon and Phonon Modes in a Coulomb-coupled Optomechanical Cavity Magnonic Systems

Quantum entanglement is a fundamental phenomenon in quantum information science and a crucial resource for quantum technologies such as precision sensing, secure communication, and computation. In hybrid cavity magno-optomechanical systems, entanglement among cavity photons, magnons, and phonons enables manipulation of quantum states across different modes via radiation pressure-based light-matter interaction. We propose a hybrid optomechanical cavity-magnonic setup with Yttrium iron garnet (YIG) sphere allowing magnons to couple with photons via magnetic-dipole interaction. The system also uses optomechanical and electrostatic interactions to entangle cavity photons and mechanical resonators. We focus on how the magnon nonlinear Kerr effect and varying coupling strengths influence entanglement dynamics. By analysing nonlinear effects alongside other coupling parameters, we identify optimal conditions for initiating and sustaining robust entanglement between the motional modes (phonons) of two Coulomb-coupled mechanical resonators. Our model predicts that adding Coulomb interaction and magnon coupling enhances the degree and tunability of entanglement, making it more resilient to thermal baths at 3 K. This study addresses how to optimize and sustain phonon-phonon entanglement in complex hybrid quantum systems. These findings offer insights relevant to developing quantum memories for continuous variable quantum information processing and other quantum technologies.

quant-ph↗

arXiv2023

A Call to Arms: AI Should be Critical for Social Media Analysis of Conflict Zones

The massive proliferation of social media data represents a transformative opportunity for conflict studies and for tracking the proliferation and use of weaponry, as conflicts are increasingly documented in these online spaces. At the same time, the scale and types of data available are problematic for traditional open-source intelligence. This paper focuses on identifying specific weapon systems and the insignias of the armed groups using them as documented in the Ukraine war, as these tasks are critical to operational intelligence and tracking weapon proliferation, especially given the scale of international military aid given to Ukraine. The large scale of social media makes manual assessment difficult, however, so this paper presents early work that uses computer vision models to support this task. We demonstrate that these models can both identify weapons embedded in images shared in social media and how the resulting collection of military-relevant images and their post times interact with the offline, real-world conflict. Not only can we then track changes in the prevalence of images of tanks, land mines, military trucks, etc., we find correlations among time series data associated with these images and the daily fatalities in this conflict. This work shows substantial opportunity for examining similar online documentation of conflict contexts, and we also point to future avenues where computer vision can be further improved for these open-source intelligence tasks.

cs.CY↗

arXiv2021

Bidirectional optical non-reciprocity in a multi-mode cavity optomechanical system

Optical non-reciprocity, a phenomenon that allows unidirectional flow of optical field is pivoted on the time reversal symmetry breaking. The symmetry breaking happens in the cavity optomechanical system (COS) due to non uniform radiation pressure as a result of light-matter interaction, and is crucial in building non-reciprocal optical devices. In our proposed COS, we study the non-reciprocal transport of optical signals across two ports via three optical modes optomechanically coupled to the mechanical excitations of two nano-mechanical resonators (NMRs) under the influence of strong classical drive fields and weak probe fields. By tuning different system parameters, we discover the conversion of reciprocal to non-reciprocal signal transmission. We reveal perfect nonreciprocal transmission of output fields when the effective cavity detuning parameters are near resonant to the NMRs' frequencies. The unidirectional non-reciprocal signal transport is robust to the optomechanical coupling parameters at resonance conditions. Moreover, the cavities' photon loss rates play an inevitable role in the unidirectional flow of signal across the two ports. Bidirectional transmission can be fully controlled by the phase changes associated with the incoming probe and drive fields via two ports. Our scheme may provide a foundation for the compact non-reciprocal communication and quantum information processing, thus enabling new devices that route photons in unconventional ways such as all-optical diodes, optical transistors and optical switches.

quant-ph↗