arXiv subjects

Mohammed Th. Hassan

Publications and source records attributed to Mohammed Th. Hassan.

11 recordsLinked to original sources

arXiv2026

Predicting Entanglement Entropy from Particle Tunneling of Interacting Fermions Using Kolmogorov-Arnold Networks

Entanglement entropy is a fundamental measure of quantum correlations and a key resource underpinning advances in quantum information and many-body physics. We uncover a universal relationship between bipartite entanglement entropy and particle number after the barrier in a one-dimensional Fermi-Hubbard system with an external asymmetric potential. Decomposing the von Neumann entropy into number entropy $S_n$ and configurational entropy $S_c$, we show that in the barrier-dominated tunneling regime both components are individually well-defined functions of the post-barrier particle density $n_A$, even though $S_c$ encodes off-diagonal coherences that are not directly accessible from density measurements alone. Using Kolmogorov-Arnold Networks - a novel machine learning architecture - we learn the relationship for entropy and its components across a broad range of interaction strengths and barrier heights with high predictive accuracy. Furthermore, we propose a simple analytical binary-entropy-like expression that quantitatively captures the observed correlation for fixed parameters. Our findings open new avenues for characterizing quantum correlations in transport phenomena and provide a powerful framework for estimating the full von Neumann entropy - including its configurational component - from a single transport observable.

quant-ph↗

arXiv2026

Electric-field control of hydrogen bonding via interfacial charge at atomic resolution

Hydrogen-bond networks govern molecular structure and function across chemistry, biology and materials science, yet their deterministic control at the atomic scale remains a central challenge (1-9).Here, we directly visualize how an external electric field enables reversible control of a hydrogen-bond network in monolayer ice on graphite through interfacial charge redistribution. Low-temperature scanning tunnelling microscopy reveals a field-driven transition from a mobile, physisorbed, non-wetting water phase to an ordered hexagonal monolayer, enabling deterministic nucleation, growth and complete wetting on an otherwise inert surface. Systematic variation of the field induces continuous lattice strain coexisting with discrete conductance states, revealing coupled structural and electronic responses. Reversal of the field polarity drives collective dipolar inversion, enabling switching between symmetry-equivalent configurations without disrupting the lattice. Supported by first-principles theory and bias-dependent imaging, these effects arise from field-induced modification of the interfacial electronic structure rather than purely geometric or orientational effects. These results establish interfacial charge redistribution as a general mechanism for electrically programming hydrogen-bond networks, providing a route to control molecular organization, electronic properties and collective dipolar order at interfaces.

cond-mat.mtrl-sci↗

arXiv2026

Attosecond quantum optics

Modern quantum optics primarily operates in the quasistationary regime, isolated from the intrinsic timescales of ultrafast optical fields. Pushing these boundaries into the femtosecond and attosecond domains is a critical frontier. Here, we generate, shape, and interrogate the quantum state of an ultrafast squeezed light field. Our optical metrology reveals a highly dynamic, time dependent squeezing distribution across individual half cycles of the electric field. Incorporating this intracycle squeezing into strong field simulations demonstrates that the temporal redistribution of quantum uncertainty fundamentally reshapes the quantum strong field physics of high harmonic emission. Furthermore, we achieve attosecond scale control of the squeezed state, visualized through inferred effective Wigner representations. Finally, we show that ultrafast squeezed light encodes its quantum properties into a photoinduced tunneling current within a petahertz phototransistor with subfemtosecond resolution, demonstrating a direct optical electronic quantum coupling. This work lays the foundation for the emerging field of ultrafast quantum optics and unlocks new avenues for high speed quantum communication and photonics.

physics.optics↗

arXiv2025

Quantum attomicroscopy: imaging quantum chemistry in action

How quantum electron and nuclei motions affect biomolecular chemical reactions remains a central challengeable question at the interface of quantum chemistry and biology. Ultrafast charge migration in deoxyribonucleic acid (DNA) has long been hypothesized to play a critical role in photochemistry, genome stability, and long-range biomolecular signaling, however, direct real-time observation of these electronic processes has remained elusive. Here, we present a theoretical investigation and propose the concept of future experimental measurements of laser-driven charge dynamics in the canonical DNA nucleobase pairs thymine_adenine and cytosine_guanine. Attosecond-resolved simulations employing high-level ab initio methods reveal base-dependent ionization mechanisms, directional charge migration pathways, and electronic coherences that govern sub-femtosecond redistribution of electron density across hydrogen-bonded nucleobase interfaces. Accordingly, we propose the concept of a quantum attosecond scanning electron microscope, termed the quantum attomicroscope (Q-attomicroscope), a capable of imaging photoinduced quantum chemistry reactions in attosecond temporal resolution and sub-nanometer spatial precision. As a proof of principle, we propose to image the charge migrations dynamics in DNA which we studied theoretically. Together, our preceptive bridges theory, instrumentation, and control, outlining a pathway toward laser mediated manipulation of DNA structure with implications for repair processes, chemical reactivity, and future personalized medicine.

physics.chem-ph↗

arXiv2025

Imaging and controlling electron motion and chemical structural dynamics of biological system in real time and space

Ultrafast electron microscopy (UEM) has found widespread applications in physics, chemistry, and materials science, enabling real-space imaging of dynamics on ultrafast timescales. Recent advances have pushed the temporal resolution of UEM into the attosecond regime, enabling the attomicroscopy technique to directly visualize electron motion. In this work, we extend the capabilities of this powerful imaging tool to investigate ultrafast electron dynamics in a biological system by imaging and controlling light induced electronic and chemical changes in the conductive network of multicellular cable bacteria. Using electron energy loss spectroscopy (EELS), we first observed a laser induced increase in π-electron density, accompanied by spectral peak broadening and a blueshift features indicative of enhanced conductivity and structural modification. We also traced the effect of ultrafast laser pumping on bulk plasmon electron oscillations by monitoring changes in the plasmon like resonance peak. Additionally, we visualized laser induced chemical structural changes in cable bacteria in real space. The imaging results revealed carbon enrichment alongside a depletion of nitrogen and oxygen, highlighting the controllability of chemical dynamics. Moreover, time resolved EELS measurements further revealed a picosecond scale decay and recovery of both π-electron and plasmonic features, attributed to electron phonon coupling. In addition to shedding light on the mechanism of electron motion in cable bacteria, these findings demonstrate ultrafast modulation and switching of conductivity, underscoring their potential as bio-optoelectronic components operating on ultrafast timescales.

physics.chem-ph↗

arXiv2025

Ultrafast quantum light uncertainty dynamics in real time

Advancements in quantum optics and squeezed light generation have transformed various domains of quantum science and technology. However, real-time quantum dynamics remain an underexplored frontier. Here, we extend quantum optics into the ultrafast regime, providing direct experimental evidence that quantum uncertainty is not a static constraint but evolves dynamically with the system state and interactions. Using ultrafast squeezed light generated via a four-wave mixing nonlinear process, we observe the temporal dynamics of amplitude uncertainty, demonstrating that quantum uncertainty is a controllable and tunable physical quantity. This offers new insights into fundamental quantum mechanics in real-time. Additionally, we demonstrate control over the quantum state of light by switching between amplitude and phase squeezing. Our ability to generate and manipulate ultrafast squeezed light waveforms with attosecond resolution unlocks exciting possibilities for quantum technologies, including petahertz scale secure quantum communication, quantum computing, and ultrafast spectroscopy. We also introduce an ultrafast quantum encryption protocol leveraging squeezed light for secure digital communication at unprecedented speeds. This work paves the way for exploring quantum uncertainty dynamics and establishes the foundation for the emerging field of ultrafast quantum science.

physics.optics↗

arXiv2025

Comment on "Comment on Attosecond electron microscopy and diffraction"

Over the past few decades, following the first demonstration of ultrafast electron microscopy, numerous research groups have focused on achieving attosecond temporal resolution in electron microscopy with the goal of imaging electron and atomic motion. Recently, several studies have claimed to achieve attosecond temporal resolution in imaging(1-3). These claims are based on the generation of attosecond electron pulse trains. However, in typical time-resolved measurements used to capture dynamic processes in real-time, the temporal resolution is determined by the envelope of the pulse train. The reliance of using attosecond electron pulse trains fails to account for the distinct temporal resolution advantages enabled by our attosecond optical gating, which are absent in the case of using a continuous-wave or long laser pulse. These oversights highlight the limitations of this methodology (1-3) in studying ultrafast phenomena of matter. It is crucial to clarify this distinction to avoid confusion, misinterpretation, and potential miscitations within the community regarding attosecond temporal resolution in electron microscopy and the attosecond imaging of matter dynamics. In contrast, Hui et al. (4) present the first realistic demonstration of attosecond imaging resolution in electron microscopy, enabling the diffraction imaging of electron motion dynamics in graphene. In a commentary by Peter Baum and Claus Ropers, the authors conjecture that the graphene dynamics observed in our time-resolved diffraction experiment (Fig. 5, Hui et al. 2024) (4) is an optical interference artifact or light modulation of electrons effects, similar to what was reported previously (1-3), in addition to raising other technical concerns. In this reply, we are pleased to address these allegations and provide clarifications to resolve the raised technical questions.

physics.optics↗

arXiv2024

Attomicroscopy imaging and control of electron motion in graphene

Attosecond science has leveraged the highly nonlinear interactions between intense few-cycle laser pulses and matter, allowing for unprecedented observation and control of electron motion with remarkable temporal resolution. However, most existing experiments focusing on laser-controlled attosecond dynamics have dealt with quasi-bound electrons released in the ionization continua of atoms, molecules, or conduction bands in solid-state systems. Here, we employed the recently developed attomicroscopy imaging tool to investigate, visualize, and manipulate the motion of bound electrons in graphene. By adjusting the carrier-envelope phase and the field strength of the driving electric field, we were able to control both the amplitude and direction of the field-induced electron current between carbon atoms in graphene. This research opens new avenues for understanding and controlling dynamic, on-demand electron motion processes, including chemical reactions, molecular bonding, and the electronic properties of materials.

cond-mat.mes-hall↗

arXiv2023

Attosecond Electron Microscopy

The electron motion in atoms and molecules is at the heart of all phenomena in nature that occur outside the nucleus. Recently, ultrafast electron and X-ray imaging tools have been developed to image the ultrafast dynamics of matter in real time and space. The cutting-edge temporal resolution of these imaging tools is on the order of a few tens to a hundred femtoseconds, limiting imaging to atomic dynamics. Hence electron motion imaging remains beyond the reach. Here, we achieved attosecond electron imaging temporal resolution in a transmission electron microscope, orders of magnitude faster than the highest reported imaging resolution, to demonstrate, which we coin it as (attomicroscopy) to image the field-induced electron dynamics in neutral multilayer graphene. Our results show that the electron motion between the carbon atoms in graphene is due to the field-driven electron dynamics in the conduction band and depends on the field waveform, strength, and polarization direction. This attomicroscopy imaging provides more insights into the electron motion of neutral matter in real time and space and would have long-anticipated real-life attosecond science applications in quantum physics, chemistry, and biology.

physics.optics↗

arXiv2021

Attosecond light field synthesis for electron motion control

The advancement of the ultrafast pulse shaping and waveform synthesis allowed to coherently control the atomic and electronic motions in matter. The temporal resolution of the waveform synthesis is inversely proportional to the broadening of its spectrum. Here, we demonstrate the light field synthesis of high-power waveforms spanning two optical octaves, from near-infrared (NIR) to deep-ultraviolet (DUV) with attosecond resolution. Moreover, we utilized the all-optical field sampling metrology for on-demand tailoring of light field waveforms to control the electron motion in matter. The demonstrated synthesis of the light field and the electron motion control pave the way for switching the photo-induced current signal in dielectric nanocircuit and establishing ultrafast photonics operating beyond the petahertz speed.

physics.optics↗

arXiv2018

Attomicroscopy: from Femtosecond to Attosecond Electron Microscopy

In the last decade, the development of Ultrafast Electron Diffraction (UED) and Microscopy (UEM) has enabled the imaging of atomic motion in real time and space. These pivotal table-top tools opened the door for a vast range of applications in different areas of science spanning chemistry, physics, materials science, and biology. We first discuss the basic principles and recent advancements, including some of the important applications, of both UED and UEM. Then, we discuss the recent advances in the field that have enhanced the spatial and temporal resolutions, where the latter, however, is still limited to a few hundreds of femtoseconds, preventing the imaging of ultrafast dynamics of matter on the scale of several tens of femtoseconds. Then, we present our new optical gating approach for generating an isolated 30 fs electron pulse with sufficient intensity to attain a temporal resolution on the same time scale. This achievement allows, for the first time, imaging the electron dynamics of matter. Finally, we demonstrate the feasibility of the optical gating approach to generate an isolated attosecond electron pulse, utilizing our recently demonstrated optical attosecond laser pulse, which paves the way for establishing the field of Attomicroscopy, ultimately enabling us to image the electron motion in action.

physics.chem-ph↗