Faheel Ather Hashmi

COMSATS University Islamabad | CUI · Department of Physics

In a recent article [Chin. Phys. Lett. 34, 020301 (2017)], Ben-Israel et al. have claimed that the experiment proposed in [Chin. Phys. Lett. 32, 050303 (2015)] to determine the past of a quantum particle in a nested Mach-Zehnder interferometer does not work, and they have proposed a modification to the experiment. We show that their claim is false,...

In the preceding comment it is claimed that we are mistaken in the analysis of the theory of the 'past of a quantum particle' proposed by the author of the comment. We show that the claim is unfounded. Moreover we show that the arguments presented in the comment are not consistent with the already proposed theory.

A new Intrusion Detection System (IDS) for network security is proposed making use of a Vector-Based Genetic Algorithm (VBGA) inspired by evolutionary approaches. The novelty in the algorithm is to represent chromosomes as vectors and training data as matrices. This approach allows multiple pathways to calculate fitness function out of which one pa...

We show that two-state vector formalism (TSVF), applied to quantum systems that make use of delicate interference effects, can lead to paradoxes. We consider a few schemes of nested Mach-Zehnder interferometers that make use of destructive interference. A particular interpretation of TSVF applied to these schemes makes predictions that are contradi...

An experiment is designed to determine the path of a photon in a nested Mach-Zehnder interferometer using quantum non-demolition(QND) measurements. We find that when the photon reaches the detector, it is following only one arm of the outer interferometer and leaves no trace in the inner interferometer; while when it goes through the inner interfer...

We investigate the influence of the additional third level on the dynamic evolution of a Two-Level system interacting with a coherent field in the strong coupling regime where Rotating Wave Approximation is not valid. We find that the additional level has great influence on the evolution of the system population. Our results show that the Two-Level...

We investigate the influence of the additional third level on the dynamic evolution of a Two-Level system interacting with a coherent field in the strong coupling regime where Rotating Wave Approximation is not valid. We find that the additional level has great influence on the evolution of the system population. Our results show that the Two-Level...

The paper by Ziauddin and Qamar [Phys. Rev. A 84, 053844 (2011)] proposes gain-assisted control of Goos-Hänchen shift. The theory presented in the paper assumes angular spectrum for a plane wave. This is a serious flaw and makes their results doubtful.

The recent paper by Ziauddin and Qamar [ Phys. Rev. A 85 055804 (2012)] proposes control of the Goos-Hänchen shift of a Gaussian field incident on a cavity containing duplicated two-level atoms. This control relies on phase control of the optical response of the intracavity medium that has been demonstrated earlier [ Phys. Rev. Lett. 101 213601 (20...

A strong nonresonant, asymmetric ultrashort pulse drives an atomic transition and causes a complete population inversion because of a sudden nonadiabatic jump. This jump is probed in real time by propagating a weak ultrashort pulse in the system which is resonant on an adjacent transition. The probe at the exit of the medium presents an oscillatory...

We present a detailed theoretical study of a method for slowing light based on the oscillations of Zeeman coherences in a double two-level system [Hashmi, F.A.; Bouchene, M.A. Phys. Rev. A 2008, 77, 051803(R)]. This method does not require the presence of any trapping state. We focus on the properties and the limitations of such a method and compar...

This thesis deals with the study of propagation effects experienced by weak light pulses as they propagate in atomic media driven by strong pulses. We explore both the ultra-short and long pulse regime and investigate the phenomena that arise at these different time scales. In the short pulse regime, a strongly driven two level atomic system presen...

We theoretically study the interaction of two time delayed, phase-locked, and nonresonant pulses with a two-level system in the strong field regime. The population transfer is shown to be extremely sensitive to the phase shift ϕ between the pulses, with efficient population transfer taking place only for ϕ close to π. This effect is explained in te...

We theoretically demonstrate the coherent control of the effective susceptibility of a duplicated two-level system. The control is obtained for a linearly polarized weak field in the presence of a much stronger orthogonally polarized field. For small optical depths, the effective susceptibility chi(eff) behaves as chilin(e 2iphi) (chilin) is the li...

We present the theory of a new method to slow a linearly polarized probe pulse as it propagates through a duplicated two-level system driven by an orthogonally polarized control field. The method makes use of Zeeman coherence oscillations (CZO) that arise in the atomic system because of the spatial and temporal modulation of the total polarization....

We consider a double two-level system in which each single two-level system is driven by a strong pulse. The light shifts induced by the strong field are probed by a weak pulse that connects the two sub-system in a crossed manner – connecting the ground state of one system with the excited state of the other and vice versa. We are interested in coh...

The interaction of strong laser fields with matter causes light-shifts that play an important role in many fields as quantum optics, molecular physics and chemistry. Here the control results from the interference between two excitation quantum paths, corresponding to the absorption and to the emission by the dressed atomic system of one photon from...

An ultrashort strong nonresonant pulse induces transient phenomena in an optically thick medium consisting of an ensemble of nondegenerate two-level atoms (nonadiabatic transitions, transient light-shifts,…). A weak resonant pulse propagates in the system and we study theoretically and numerically the temporal and spectral modifications that are in...

Cette thèse concerne l'étude des effets de propagation subis par des impulsions lumineuses de faible intensité lorsqu'elles se propagent dans des systèmes atomiques soumis à des champs intenses. Nous explorons aussi bien le régime d'impulsions longues que courtes et nous analysons les phénomènes qui se produisent à ces échelles de temps différents....