https://repository.maseno.ac.ke/handle/123456789/113 Fri, 15 May 2026 12:08:29 GMT 2026-05-15T12:08:29Z https://repository.maseno.ac.ke/handle/123456789/6235 Exploring Rabi Oscillations, Maximally Entangled States and Perfect Teleportation in the Anti-Jaynes-Cummings Interaction: Insights into Quantum Dynamics and Entanglement Applications Mayero, Christopher; Omolo, Joseph Akeyo This study presents a method for producing maximally entangled qubit states, also known as entangled anti-polariton qubit states, in the anti-Jaynes-Cummings interaction mechanism. We show that, in an initial vacuum-field, the time evolution of entanglement in the anti-Jaynes-Cummings interaction process takes the same form as in the Jaynes-Cummings interaction process, and that Rabi oscillations in a cavity mode in the anti-Jaynes-Cummings interaction process occur in the reverse sense relative to the Jaynes-Cummings interaction process. We demonstrate quantum teleportation of an atomic quantum state using the created anti-polariton qubit state as one of the initial qubits. We accomplish a perfect maximal teleportation fidelity of unity by employing an entanglement swapping procedure. URI: http://archive.article4submit.com/id/eprint/3041 Mon, 11 Nov 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6235 2024-11-11T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6217 Tuning the structural and mechanical properties of SiC-Li and SiC-Na alloys for aerospace application: an ab initio study Otieno, Ochieng Victor; Ongwen, Nicholas; Otieno, Calford Aluminum (Al) and its alloys are popular in the aerospace industry due to their high strength-to-weight ratio, corrosion resistance, and ductility. However, these properties (extreme ductility and malleability) can compromise corrosion resistance, making them susceptible to dents and scratches. Silicon Carbide (SiC) is a promising alternative to Al and it alloys due to its higher Youngs modulus and excellent wear resistance, although it has the drawbacks of brittleness and higher density. This study investigated the structural and mechanical properties of SiC alloyed with lithium (SiC-Li) or sodium (SiC-Na) using ab initio calculations with the aim of tuning the structural and mechanical properties of SiC. Modeling was done using Burai software, which offers a friendly graphical user interface for Quantum ESPRESSO, thus facilitating the creation of input files, visualization of crystal structures and analysis of results. The results from this study showed that the addition of Li and Na lowered the density as well as the mechanical properties of SiC but still being favorably better than those of Al and its alloys, suggesting that the modeled alloys could potentially replace the traditional Al and its alloys in the aerospace industry. Further experimental studies are needed to validate these findings and to explore the possibility of simultaneous alloying of SiC with both Li and Na for enhanced performance. Mon, 04 Nov 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6217 2024-11-04T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6216 First principles investigation of elastic, electronic and thermoelectric properties of lead-free Cs–X–I (X= Pb, Gd, Nd, Y) perovskites Alruqi, Adel Bandar; Ongwen, Nicholas Ogada Perovskites have become the center of recent research for their possible application in perovskite solar cells, owing to their desirable optical and electronic properties, flexibility, tunability, and low–cost fabrication. Most of the perovskites are however made of lead, which is a highly poisonous element. It is therefore necessary to seek alternative perovskites for this application that are less toxic. This study investigated the elastic, electronic, and thermoelectric properties of Cs–X–I (X = Pb, Gd, Nd, and Y) as possible replacements to the leaded CsPbI3 due to their less toxic nature. The density functional theory was utilized in the computations, with quantum espresso and BoltzTrap packages. The results showed that all the materials were structurally stable. The computed mechanical properties also showed that all the other materials had better elastic constants compared to those of CsPbI3. CsPbI3 was observed to exhibit the lowest band gap, unlike the others. Moreover, the other materials possessed higher elastic constants, electrical conductivities, and lowest thermal conductivities, which are highly needed in the perovskite solar cells. However, an experimental treatment needs to be done on the studied structures in order to confirm the properties obtained in this work. Thu, 31 Oct 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6216 2024-10-31T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6215 Synthesis and Characterization of Cadmium Tin Oxide for MEMS Substrates and Its Comparative Computational Study with Silicon and Silicon Carbide Ongwen, Nicholas The rising demand for semiconductor substrates for printing electronic circuits has been sparked by recent breakthroughs in electronics. The most popular substrate for printing these devices is silicon (Si), which is chosen over other substrates like silicon nitride because it is more widely accessible, and has better electrical and electronic properties. Despite the benefits above, Si has a number of disadvantages, including being brittle and only occasionally existing as a pure element. This study synthesized and characterized cadmium tin oxide (CTO) as potential substrates for MEMS manufacturing. A comparative computational study of the structural and mechanical properties with Si and silicon carbide (SiC) was also made. The experiments involved structural characterization of the synthesized samples at varied concentrations of cadmium, while the computations involved use of density functional theory within the generalized gradient approximation to investigate the structural and mechanical properties of the three materials. SiC was found to have better mechanical properties than both Si and CTO, but its brittleness prevents it from being used in the production of flexible MEMS. The manufacturing of flexible MEMS, including microbolometers and biomedical MEMS, can be made possible due to the soft and ductile character of CTO, especially the CTO 3, which was the most ductile. Article can be accessed via:https://link.springer.com/article/10.1007/s13538-024-01624-6 Tue, 22 Oct 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6215 2024-10-22T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6141 Gravitation in Flat Euclidean Spacetime Frame: Unified Electrogravity and Magnetogravity Forces Kibande, Wellingtone; Omolo, Joseph Akeyo; Simiyu, Dismas Wamalwa An effective description of physics requires an appropriate geometrical frame. Three-dimensional Euclidean space provides the geometrical frame for non-relativistic physics. A derivation of an imaginary temporal axis− icˆq the speed, ˆq the unit wave-vector of light, extends the standard Euclidean space into a well-defined four-dimensional Euclidean spacetime frame, which provides the natural mathematical framework for relativistic physics. The basic elements of the Euclidean spacetime frame are fully specified four-component complex vectors satisfying standard vector operations and vector identities. In developing a theory of gravitation in the Euclidean spacetime frame, we have used the Lense-Thirring spacetime metric of linearized general relativity to derive an appropriate complex four-component gravitational field potential vector. Taking the curl of the field potential vector provides a unified complex gravitational field strength composed of electric-type and magnetic-type components. Taking the cross-product of the complex four-component velocity and the field strength provides a unified complex gravitational force intensity composed of gravitoelectric and gravitomagnetic components. Application to the motion of a gyroscope in the gravitational field of the earth provides the standard results of frame-dragging and geodetic effects as determined in linearized general relativity theory. Mon, 15 Jul 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6141 2024-07-15T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6123 Optical properties of silver-doped zinc oxide thin films: an optimization study Omina, Betty N; Juma, Albert O; Muiva, Cosmas M; Oduor, Andrew O Silver (Ag), not only alters the electrical and optical properties of ZnO thin films but also has the ability to enhance its ultraviolet (UV) emission. However, the mechanism for the UV emission enhancement has not been clearly understood. The study focused on optimization of the optical properties of pristine and Ag-doped ZnO films through variation of preparation and post deposition parameters. The prepared pristine and Ag-doped ZnO films were found to be polycrystalline in nature with diffraction peaks corresponding to ZnO and Ag phases. Increase in Ag and annealing temperature led to increase in the transmittance of Ag-doped ZnO films. The refractive index was found to increase with a decrease in substrate-source distance, an increase in Ag concentration, film thickness, and annealing temperature. The extinction coefficient for the analysed films was found to decrease with increase in substrate-source distance and annealing temperature, but increased with increase in film thickness. An inherent dissipation of electromagnetic energy in pristine and Ag-doped ZnO films was observed due to strong interaction between low and wide optical band gap energies of Ag and ZnO, respectively. The optical band gap energy increased with an increase in substrate-source distance, decreased with an increase in film thickness and annealing temperature at a wavelength, . The observed trends have been explained based on polarizability, reduced structural defects, thermal expansion, and lattice vibrations in pristine and Ag-doped ZnO films. The obtained optimized properties show that Ag-doped ZnO films are good candidates for optoelectronic applications. Access this article via:https://link.springer.com/article/10.1007/s11082-024-07287-6 Sat, 27 Jul 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6123 2024-07-27T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6066 Convergence of the Laplace and the alternative multipole expansion approximation series for the Coulomb potential Jobunga, EO; Wandera, CO; Okeyo, OS Multipole expansion is a powerful technique used in many-body physics to solve dynamical problems involving correlated interactions between constituent particles. The Laplace multipole expansion series of the Coulomb potential is well established in literature. We compare its convergence with our recently developed perturbative and analytical alternative multipole expansion series of the Coulomb potential. In our working, we confirm that the Laplace and the analytical alternative multipole expansion series are equivalent as expected. In terms of performance, the perturbative alternative multipole expansion series underapproximate the expected results to some extent while the Laplace and the analytical alternative multipole expansion series yield results which are relatively accurate but oscillatory in nature even with a higher number of angular momentum terms employed. As a practical example, we have evaluated the Slater double integrals for two-electron systems using the multipole expansion techniques and a mean field approximation. The estimated results show that only spherical interactions are dominant while the higher-order interactions are negligible. To highlight the discrepancy in the application of each of the formulations of the multipole expansion series for the electron-electron interaction potential, an estimation of the non-relativistic groundstate energies of some helium-like systems, evaluated using the spherical approximation of the multipole potential, is provided. Our findings are likely to be useful in the treatment of the Coulomb potential in electronic structure calculations as well as in celestial mechanics. https://www.nature.com/articles/s41598-023-42724-8 Mon, 25 Sep 2023 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6066 2023-09-25T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6057 Characterization of atomic state evolution in the JC and anti-JC models: spin-displaced field modes in the quantum Rabi model Omolo, Joseph Akeyo In this article, characterization of the atomic state evolution in the Jaynes-Cummings (JC) and anti-Jaynes-Cummings (aJC) models means using the reduced atomic state degree of purity, concurrence and spin excitation number to determine the ranges and critical values of the mean photon number and frequency detuning parameters at which the atom is in a disentangled pure, mixed or entangled state. By unifying the mean photon number amplitude and detuning parameters in a simple relation, leaving the mean photon number as the only variable parameter, we have discovered a beautiful natural evolution property where the atom is in a uniformly mixed state describing symmetrical stable evolution of collapses and revivals of the degree of purity and concurrence, one above and the other below, a uniformly mixed state axis through points of equal degree of purity and concurrence at 1√ Mon, 20 Mar 2023 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6057 2023-03-20T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6053 A Comparative Thermodynamic Study of AlF3, ScF3, Al0.5Sc0.5F3, and In0.5Sc0.5F3 for Optical Coatings: A Computational Study Alruqi, Adel Bandar; Ongwen, O. Nicholas Optical coatings are thin layers of materials applied to optical components in order to modify the transmission, reflection, or polarization properties of light. The common materials used for optical coatings include magnesium fluoride (MgF2 ), scandium trifluoride (ScF3 ), and aluminum trifluoride (AlF3 ), owing to their desirable optical properties, spectral range, and compatibility with substrates. However, each of these materials has its own drawbacks. For instance, AlF3 has been found to exhibit limited resistance to attack by chemicals, as well as poor thermal stability, while MgF2 has low durability, as well as being hygroscopic. In this study, we undertook ab initio calculations in order to compare the thermal properties of AlF3 , ScF3 , Al0.5Sc0.5F3 , and In0.5Sc0.5F3 in order to obtain the best material for optical coatings. MgF2 was also included in the study as a reference. The calculations used PBE pseudopotentials and the extended generalized gradient approximation within the quantum espresso algorithm. The study demonstrated that the computed results agree with the information found in the literature. ScF3 exhibited a negative coefficient of thermal expansion, unlike the other four. Moreover, AlF3 was found to be the best candidate for optical coatings that are used in high-power laser systems with high thermal dissipation, due to its superior thermal expansion coefficient as well as its better response to thermal stress. The large variation between the cp and cv of ScF3 is not desirable. Moreover, due to its negative thermal expansion coefficient, ScF3 is not thermally stable. The highest thermal stability was exhibited by In0.5Sc0.5F3 . Since Al0.5Sc0.5F3 and In0.5Sc0.5F3 have been modeled in this study for the first time, experimental determination of their crystal structures needs to be investigated. Mon, 27 Nov 2023 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6053 2023-11-27T00:00:00Z https://repository.maseno.ac.ke/handle/123456789/6052 Structural and Mechanical Properties of NbN Alloyed with Hf, In, and Zr for Orthopedic Applications: A First-Principles Study Alruqi, Adel Bandar; Ongwen, O. Nicholas The search for biocompatible, non-toxic, and wear-resistant materials for orthopedic implant applications is on the rise. Different materials have been investigated for this purpose, some of which have proved successful. However, one challenge that has proven difficult to overcome is the balance between ductility and hardness of these materials. This study employed ab initio calculations to investigate the structural and mechanical properties of niobium nitride (NbN) alloyed with hafnium, indium, and zirconium, with the aim of improving its hardness. The calculations made use of density function theory within the quantum espresso package’s generalized gradient approximation, with Perdew–Burke–Ernzerhof ultrasoft pseudopotentials in all the calculations. It was found that addition of the three metals led to an improvement in both the shear and Young’s moduli of the alloys compared to those of the NbN. However, both the bulk moduli and the Poisson’s ratios reduced with the introduction of the metals. The Young’s moduli of all the samples were found to be higher than that of bone. The Vickers hardness of the alloys were found to be significantly higher than that of NbN, with that of indium being the highest. The alloys are therefore good for wear-resistant artificial bone implants in ceramic acetabulum, and also in prosthetic heads. Wed, 17 Jan 2024 00:00:00 GMT https://repository.maseno.ac.ke/handle/123456789/6052 2024-01-17T00:00:00Z