M.S. Theses

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Revisiting massless scalar two point functions on dS4
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2023., 2023) Ayfer, Taha.
Scalar field theories in de Sitter space, as a special case of Quantum Field Theory in Curved spacetime, are currently popular research areas in physics. Scalar field theory is worth studying for several reasons among all the tensor field theories in de Sitter. For example, a well-established scalar field theory in de Sitter might pave the way for the construction of higher rank tensor fields in de Sitter [1], or massless scalar fields might explain the homogeneity of the Cosmic Wave Background with the inflation era of the universe [1, 2]. Hence, we mainly focused on massless scalar two-point functions because they exhibit different properties than massive ones; therefore, they require alternative approaches. From the representation theory perspective, in 4D de Sitter, among spin-0 particles m = 0 belongs to Discrete Series, which requires special attention different from Principle and Complementary Series [3]. While earlier works emphasize the lack of a unique vacuum and breaking of de Sitter symmetry as the main problems of massless two-point functions [4], these may be connected to an inadequate analysis of the boundary conditions. The recent ideas suggest more promising treatments for discrete series two-point functions [3, 5]. The boundary conditions cannot completely constrain the form of the solution because of the lack of a preferred vacuum, while it is well defined for the massive case as the Bunch-Davies vacuum [3]. Here we follow a Fourier Transformation procedure of two-point functions [4] to address the boundary conditions for the massless Wightman Function and its singularities. Finally, we are left with one free parameter that denotes an overall constant contribution which can be set to zero. The form of singularities, on the other hand, coincides with the Minkowskian type singularities in the incident point limit. Additionally, we summarized two-contemporary studies [3, 5] and discussed their results.
An unsupervised learning approach to seismic waveform classification via representation learning
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2023., 2023) Efe, Onur.; Özakın, Arkadaş.
Seismology is an observation-based science and requires well- classified seismic signals to expand its boundaries. One of the most basic classification problems is to separate earthquake- based seismic activity from background noise. Machine learning algorithms are recently introduced as a solution to this problem. Although unsupervised learning-based algorithms have been used for specific cases (certain seismic events, time intervals, geographical regions, etc.), most proposed algorithms are supervised learning-based. Consequently, general-purpose unsupervised learning algorithms have not been developed yet. Supervised learning-based models may have biases due to the dataset used in training, which can lead to poor results for observational purposes. Considering that the seismic waveforms are labeled in the light of current information, it’s clear that training the models using these labels could block potential discoveries. Developing methods with complementary biases is important to fill the blind spots of supervised learning-based models. Our primary motivation in this thesis is to develop unsupervised learning-based general- purpose detection methods that distinguish earthquake-based seismic activity from background noise. Based on this motivation, deep learning-based methods that can classify waveforms using one or more stations have been developed.
Counter-propagating intracavity optical tweezers
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2023., 2023) Ay, Aysu.; Elahi, Parviz.
Optical tweezers are a powerful tool that utilizes optical forces generated by the exchange of momentum between light and matter to trap and manipulate a wide range of particles, including atoms and molecules, organelles, proteins,and cells. Since intracavity optical trapping was introduced, a new research opportunity opened for three-dimensional optical trapping of microscopic objects using a low numerical aperture lens at low laser intensity. This method has introduced the placing of the trapping optics within a fiber laser ring cavity and the forces of optical feedback radiation. There are two possible configurations for intracavity optical trapping: single-beam and counter-propagating beam configurations. The former has already been proposed and implemented, while the latter still needs to be discussed in detail: the focus of this work lies on counter-propagating beam configuration. This work demonstrates the design, implementation, and experimentation of counter- propagating optical tweezers. It presents 3D trapping of 1.98 μm-diameter polystyrene particles, which single-beam intracavity traps were incapable of performing. The total average power on the sample was measured to be 885 μW, which corresponds to an average intensity of 21.2 μWμm−2. The inversely correlated counter-propagating beams reduce the average intensity on the particle in the trap; hence, they enable the trapping of light-sensitive biological matter. This paves the way for new and exciting applications for optical tweezers.
Topological string theory and BPS counting
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2023., 2023) Domurcukgül, Tolga.; Kozçaz, Can.
This thesis covers topological string theory, Seiberg-Witten theory, and instanton counting which provide insights into the interplay between geometry, topology, and quantum field theory. The target space interpretation of topological strings is explored, including its connections to physical string theory and geometric engineering. Along with that, M-theory compactification on a circle provides a target space interpretation for topological strings, leading to the discovery of new integer invariants known as Gopakumar-Vafa invariants. Seiberg-Witten theory plays a central role in understanding the dynamics of supersymmetric gauge theories. The moduli space of vacua offers a comprehensive description of the possible vacuum states of these theories, and the effective field theory approach enables the derivation of the quantum prepotential. The Seiberg-Witten solution provides exact results for various quantities in these theories and is examined in the context of elliptic curves. Then the Nekrasov partition function is used to study instantons in N = 2 super Yang-Mills theory and the resolution of singularities and equivariant cohomology techniques are used to address non- compactness issues and subtleties arising from singularities. The role of Nekrasov factors in capturing contributions from different sectors of the instanton moduli space has been explored. The five-dimensional lift of Nekrasov partition function is introduced and studied through the connection to the Gopakumar-Vafa expansion of topological string theory.
Electrical detection of spin-orbit torque in antiferromagnets
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Göksal, Cemal İlkin.; Özatay, Özhan, 1978- .
Ferromagnetic spintronics has been a game changer for memory technologies, until it has been understood that at some point ferromagnetic properties of these devices won’t be able to compensate for the demand on volume and performance. At this point, antiferromagnetic (AFM) spintronics emerged as the most promising alternative and this accelerated the research and investment on AFM spintronics. AFM materials are known with their magnetic toughness due to zero net magnetization in bulk and promising bit per volume ratio thanks to their two spin lattices pointing in opposite directions. In this study, our aim is to achieve current induced manipulation of antiferromagnetic moments. Though there are multiple suggested ways for AFM magnetization manipulation, we study DC electrical transport experiments where by we utilize spin-orbit torque (SOT) effect on metallic AFM materials (IrMn4,IrMn3FeMn). The underlying mechanism for spin manipulation is a mixture of Spin Hall Effect (SHE) and interfacial Rashba effect (IRE). We start our investigation with bi-layers of high SOC heavy metals (Pt, Ta) and AFM metal(IrMn4,FeMn) hetero structures of [HM/AFM]. Following these experiments, we also investigate the cumulative properties of SOT effect by demonstrating DC electrical transport experiments on HM/AFM/HM trilayer hetero structures and stacks of [HM/AFM/HM] × n, (where n=2,3,4 etc.). These results will help to improve understanding of the nature of electrical manipulation of AFM spin and determine the conditions to use them as spintronic devices.
A permanent-magnet microwave discharge ion source at KAHVELab
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Açıksöz, Sevim.; Özcan, Veysi Erkcan.; Çetinkaya, Hakan.
A new Permanent Magnet Microwave Discharge Ion Source (PM-MDIS) has been designed and constructed at Boğaziçi University Kandilli Detector, Accelerator, and Instrumentation Laboratory (KAHVELab). The PM-MDIS design includes a plasma chamber surrounded by permanent magnets, a hydrogen gas supply to sustain the plasma, the waveguide system used to transfer power to the plasma chamber, a dualelectrode extraction system used to extract ions from the chamber, and a Faraday cup to measure the beam current. The aim is to extract ions from the thermal hydrogen plasma generated using a 2.45 GHz microwave source. In order to extract ions from the plasma medium, a magnetic field exceeding 875G has to be applied over the plasma chamber to ensure Electron Cyclotron Resonance (ECR) condition is satisfied. Since the plasma chamber is to be operated on the high voltage (HV) platform, higher system stability can be achieved by using the permanent magnet configuration shown in this work. Based on the designed magnetic field profile of the constructed system, the dual-electrode extraction system has also been designed using IBSIMU integrated DemirciPro software and produced to transmit proton beams from the plasma chamber to the beamline. The determination of the magnetic field profile, and the vacuum, HV, and beam tests are completed before integration with the rest of the beamline. Finally, how the transmitted proton beams behaved on the existing Low Energy Beam Transport (LEBT) line has been examined, and the LEBT line configuration has been optimized accordingly. In addition, besides the protons, the trajectories of H+ 2 and H+ 3 ions from the PM-MDIS have also been studied to optimize the LEBT beam optics. As a result of this study, the PM-MDIS has been integrated with the proton beamline, and 0.38mA mean beam current has been measured with the Faraday cup in the experiments performed at 20 kV and 0.01 sccm gas flow.
Refined geometric transition and local P2
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Çark, Bilal.; Kozçaz, Can.
In this thesis, the approaches for calculating refined topological string amplitudes on compact Calabi-Yaus for the case local P^2 are investigated. One approach is making use of large N duality and refined Chern-Simons theory (Aganagic and Shakirov) and the other is defining another vertex (Iqbal, Kozçaz). It turns out that this new vertex can be obtained from refined Chern-Simons theory using properties of Macdonald and Schur functions, in this thesis we outline the way of this derivation. Aside from a brief review of topological strings, large N duality and knot invariants that can be calculated using Chern-Simons theory, a review of topological vertex formalism and its derivation using Chern-Simons theory, both in the refined and unrefined case is included.
DAQ link and IBERT studies of CMS HGCAL back end electronics
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Tatlı, Taylan.; Akgün, Bora.; Gülmez, Erhan.
The HL-LHC experiment will face two main challenges: high radiation due to increased high integrated luminosity and large amount of data resulting from high instantaneous luminosity. To overcome these two challenges, CMS plans to make many updates to its detector, such as replacing the calorimeter with high granular ity calorimeter. The new calorimeter uses newly developed technologies for both the front-end and back-end electronics part of the data read-out electronics. The design of these parts is based on high-bandwidth data transmission via optical links and FPGA technology. A lot of studies are required to establish an efficient and long-lasting data collection performance of the detector. One of them is the optimization of link connections of the hardware on the back- end electronics and the other is integrated bit error rate tests on the FPGAs. In this thesis, first, optimization of link connection stud ies, methodology and tools used for those studies are explained and then integrated bit error rate test by introducing and explaining hardware and software used for data transmission at back end electronics of the new calorimeter.
Noise robust real-time focus detection with deep learning for ultra-fast laser micromachining
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Polat, Can.; Elahi, Parviz.
In this thesis, different types of machine learning models are provided for ultra-fast laser micromachining system to actively control the focusing of light on the processing material by detecting the reflected light. These different types of models are tested for both experimental and theoretical approaches. For the experimental approach, four different machine learning models are explored. These models were tested for mirror, silicon, steel, and copper samples. The proposed machine learning models offer real-time control with over 90\% accuracy. For the simulation, noise at the material surface and the detection system are considered. The noise simulation, including the laser micromachining system, is done using Fourier optics and signal processing. Noise levels at the material surface are determined by laser scanning microscope measurements of experimental samples, and the commercial detection camera noises are considered for the detection noise. Convolutional neural network models are used for focus control in the simulation. Depending on the noise level, the proposed model achieves above 95\% accuracy.
3+1 formulation in Newton-Cartan gravity
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Aras, Ulaş.; Bleeken, Dieter Van den.
In this thesis, we will give a review of torsion-free Newton- Cartan theory. We will start by doing a large c expansion of general relativity and we will restrict ourselves to a few leading orders. After obtaining Newton-Cartan theory in this way, we will explore its symmetries. Through a special set of combined symmetries, we will construct a split space and time structure. Lastly, we will work out the field equations and equations of motion for a particle in the 3+1 formulation we have obtained.
Total internal reflection holographic microcopy for cell extension imaging
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Gürcan, Tolga.; Ünlü, Mehmet Burçin.; Toy, Muhammed Fatih.
The study of interfacial structures is of utmost importance not only for various research fields such as cell biology and display systems but also their sub-disciplines. One of the traditional means of imaging buried structures rely on fluorescence labeling and the use of optical sectioning with superresolution microscopy. Although it exceeds diffraction limit, there are various shortcomings to utilize this methodology such as its reliance on fluorescent markers, long exposure times to high cost of the imaging sys tem. Ultimately, these limitations position the existing technologies unideal for live cell imaging, including the imaging of surface proteins of a living cell. A label free quanti tative phase imaging method is realized in this study to enable imaging of an interface between different media. This system is based on off-axis holographic microscopy and uses a high numerical aperture (NA) microscope objective to achieve total internal reflection (TIR). Existing literature on total internal reflection holographic microscopy utilizes prism to achieve TIR which limits the working distance of objective to be large hence resolution. Proposed system relies on a 100x objective with 1.49 NA to improve resolution and magnification. Complex field which is reflected from burried interface of the sample can be recovered by using digital holography principles. The resolution of the system can further be enhanced by combining several illumination angles and utilizing synthetic aperture reconstruction. Also a new iterative algorithm for maskless grayscale lithography which uses quantitative phase measurements as feedback is real ized in this study. Phase measurements are performed via an off-axis digital holography configuration. A spiral phase plate which has uses in superresolution microscopy tech niques is produced with proposed algorithm and shown to perform better compared to classical method.
The inverse scattering method of general relativity
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Eygi, Esat Erdem.; Bleeken, Dieter Van den.
In this thesis, the Inverse Scattering Method of Belinski and Zakharov is studied in the context of general relativity. The physical interpretation of solitons is estab lished, as well as the connection between solitons and Weyl Class solutions. The single-source and double-source solutions of Einstein’s equations are generated by the Belinski-Zakharov method. The event horizons of single compact objects and binary compact objects are illustrated. The surfaces are isometrically embedded into Eu clidean three-space, hyperbolic three-space by the half-space model, and hyperbolic three-space by the Poincare ball model.
Analysis of J / ψ ώπ π at BESIII
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Yüncü, Alperen.; Özcan, Veysi Erkcan.; Uman, İsmail Ruhi.
Using a sample of 1.3 billion J= events collected with the BESIII detector at the BEPCII storage ring, the decay channel J= ! ! 0 0 has been studied. Two of the lightest tetraquark candidates, f0(500) (a.k.a. ) and f0(980) have been searched for. A Dalitz Plot analysis has been performed and in additon to f0(500) ( ) and f0(980), f2(1270), b1(1325), (1450), and f2(2300) have been observed. The analysis and background study indicate that this channel is suitable for a detailed study of the resonances through a Partial Wave Analysis.
Aspects of supersymmetric mechanics
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2014., 2014.) Çapku, Zürbiye.; Bleeken, Dieter Van den.
Supersymmetry is a space time symmetry which relates bosons to fermions or vice verca. It requires that for each particle there has to be an anti- particle with the same mass. Along this thesis some supersymmetric Lagrangian models and their properties are discussed. One of them is a Quiver Lagrangian model of the classical system of D-particles connected to each other by light strings. Quiver mechanics is used in a quantum description of black holes. The Quiver quantum mechanical model is one of the key ways to understand the thermodynamic properties of large N=2 black holes in 4 dimensions from the point of view of string theory. In the thesis some quantum approximations are given to have an e ective Quiver Lagrangian similar to the Lagrangian in a background magnetic eld with a Dirac monopole term. Following it, we discuss the classical properties of the Higgs and Coulomb branches of N=4 Quiver mechanics and derive Coulomb and Higgs minima of vacua in this thesis. However, we are addressing the question whether a stable Coulomb Branch can also be obtained, classically. We use separation of scales and quasi-classical expansion methods to derive the same e ective Lagrangian in a classical way. Separation of scales is the method of determining the fast and slow elds in the Lagrangian and eliminating the e ect of fastly oscillating elds by averaging them in a long time interval. We aim to get some time independent e ective potentials for slowly changing elds by using the adiabatic invariant theorem. Quasi-classical expansion describes the bosonic classical dynamics along with fermionic degrees of freedom. It tells us that the classical solution always involves Grassmann terms with a quasi-classical solution when the coupling between bosons and fermions appears in the equations of motion. Therefore, it is a Grassmann valued function.
Ultrasound simulations using computed tomography images as priors
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Tuzer, Mert.; Ünlü, Mehmet Burçin.; Acar, Burak.
Medical ultrasound system is one of the most ubiquitous imaging modalities in the world. In addition to the noninvasive nature of it, being low-cost and portable compared to other modalities makes it wide-spread in hospitals. Such common usage of the system needs more ultrasound technicians, or sonographers, and consequently training of new ones which requires at least a patient and an expert and almost a year to be a sonographer at last. In this phase, ultrasound simulators act a key role which reduces the need of human and cost factor significantly. The need for such real-time simulators has caused various works suggested in this area. They basically either interpolates pre-recorded ultrasound images (interpolative methods) or generates ultrasound images using other modalities i.e, computed tomography, magnetic resonance imaging (generative methods). The drawbacks of these methods respectively are incapability of simulating with various probe positions (view-dependent) and lacking realism due to not solving the wave physics exactly. In this thesis, a real-time ray-based generative ultrasound simulator using the computed tomography images will be presented. The novalties in this work are emanating multi-rays from each transducer element instead of single ray transmission by each of the element and two speckle models based on a local entropy map of computer tomography images and a machine learning algorithm in which some pairs of computer tomography images and ultrasound images of the same body slice are used.
Finite size effects on the Bose-Einstein condensation
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2014., 2014.) Doğan, Ebru.; Turgut, Osman Teoman.
In this thesis, the nite size e ects for the Bose-Einstein condensation are investigated. The application of the Poisson summation method on the ideal Bose gas (both for relativistic and non-relativistic cases) is studied. The Bose gas is assumed to be enclosed in a cubical nite enclosure with periodic boundary conditions. The Bogoliubov theory for the weakly interacting Bose gas is reviewed and an expression for the ground state energy in terms of the heat kernel is obtained. We observed that a well known result of the ground state energy is obtainable via an alternative method. Then for the zero temperature case, the depletion of the condensate is treated with the heat kernel analysis combined with the Poisson summation method. The results show that for such con guration, nite size corrections turn out to be of order 1=L2. Finally, for the zero temperature case, the ground state energy is analysed by scaling the heat kernel. This yields nite size corrections of order 1=L, a result which shows the necessity of a more elaborate treatment for more accurate results.
Search for E6 iso-singlet quarks in ATLAS, through the H J Z J decay channel
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2014., 2014.) Sıral, İsmet.; Özcan, Veysi Erkcan.
This thesis searches for the heavy iso-singlet quarks forseen by F. Gursey, P. Ramond and P. Sikivie' s E6 grand uni ed theory model using the data recorded by the ATLAS detector under the pp ! DD ! HjZj ! 4j 2l decay hypothesis. (a avor changing neutral current process). The data used in the analysis corresponds to 20 fb{u100000}1 total integrated luminosity collected from proton proton collision at c.o.m. energy of 8TeV, provided by the large hadron collider The analysis uses a cut based algorithm to select the events with four jets and a Z candidate that has been reconstructed from two charged leptons. Flavor tagging is used to improve the reconstruction of the Higgs bosons. No excess events beyond what is predicted by the Standard Model has been observed and the E6 heavy iso-singlet quark with a mass lower then 490 GeV is excluded at 95% con dence level. Also no excess events beyond what is predicted by the Standard Model has been observed on the search for a heavy quark that decays only via avor changing neutral currents. For this quark, the mass lower then 730 GeV is excluded with the 95% con dence level.
Improving physical parameterization for warm bias of REGCM4.0 on arctic and sub-arctic (MID, MID-EAST and NORTHEAST Asia regions
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2014., 2014.) Öztürk, Tuğba.; Kurnaz, M. Levent.
In this thesis, the semi-empirical cloudiness parameterization adapted to the regional climate model of the Abdus Salam International Center for Theoretical Physics (ICTP), RegCM to improve the model's ability to simulate the temperature climatology of Central Asia region. The new semi-empirical cloudiness parameterization was tested by using ERA-interim and ERA40 reanalysis data and the global climate model ECHAM5 as the boundary condition for di erent periods of time. The performance of the regional climate model RegCM in simulating the climate of the region were improved. Investigation of the future temperature and precipitation climatology of Central Asia was done for periods of 2010-2040, 2040-2070 and 2070-2100 with respect to the period of 1970-2000 by using RegCM4.3.5 which was driven by two global climate models. RCP4.5 and RCP8.5 emission scenario (IPCC) output of HadGEM2 and MPI-ESM-MR global climate model were dynamically downscaled to 50 km for the domain. Results showed that strong warming in the winter and a decrease in precipitation in almost all parts of the domain will be seen for the future periods. The future mean air temperature and precipitation climatology and variability were also projected over the Mediterranean region by using A2, A1B and B1 scenario outputs of 16 global climate models. Results showed that strong warming up to 6.5 C in the summer and lowest warming in the winter season will be observed. Decrease in precipitation will be seen in all seasons excluding the Switzerland and Caucasian region during the winter season for future period of 2070-2100 with respect to reference period of 1970-2000.
Structural characterization of NiMnX (Sn, In) thin film alloys
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2014., 2014.) Güvenç, Sema.; Skarlatos, Yani.
Ferromagnetic Ni-Mn-X (Sn, In) alloys are predicted as potential candidates for energy e cient Magnetocaloric E ect (MCE) technologies. The MCE is the basis of magnetic refrigeration and it is expected to leads to a groundbreaking progress on conventional refrigeration methods. In our research, NiMnX (Sn, In) thin lm alloys were for rst time fabricated by co-sputter deposition method. The Mn losses due to the high Mn vapor pressure produce a deviation from the desired Ni50Mn37Sn13 (Sn, In) composition, which are partially compensated by increasing power of the Mn target gun. A systematic study of thin lm co-sputter fabrication was divided into three stages; (i) a NiMnX (Sn, In) target was evaporated at di erent temperatures in order to study the grain size temperature dependence, (ii) the nominal chemical composition (Ni50Mn37Sn13) was reach by controlling the power value applied to the Mn target, (iii) the dependence of the phase transformation temperature with the grain size of the thin lm alloys was studied. Grain size can be controlled by modifying the substrate temperature (Ts). The crystal structure is highly dependent on composition and 10-14M monoclinic crystal structure can be only found for when the Sn and In values range from 10 to 13 %. Austenite-martensite transformation, and therefore magnetocaloric e ect, can only be founded for this compositional range. Our results con rm that nominal composition, Ni50Mn37Sn13, can be reached in thin lms for given co-sputter parameter. As expected NiMnSn alloys in the shape of thin lms only exhibit austenite-martensite transformations in a narrow compositional range. Further studies are required to con rm the potentiality of this material as a potential candidate for magnetic cooling technology.
Fusion of W states using optical quantum gates
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2014., 2014.) Diker, Fırat.; Arık, Metin.; Özaydın, Fatih.
In this work, after talking about historical developments leading to ideas of information processing based on quantum dynamics, we will be constructing basic mathematical expressions for qubits and quantum gates, the To oli gate and the cNOT gate. To do this, we will mention the superposition of polarization states of photons and their state matrices de ning our quantum system since these matrices purely depend on the qubits. Later, we will mention one of the basic theorems in quantum information processing, the no-cloning theorem that states that no operation can be de ned cloning some quantum state to steal information. We will also point out the fact that quantum systems must be isolated from environment by showing an example. In the later section, we will talk about the reversibility property of quantum information processing by examining quantum To oli and cNOT gates. By showing famous examples, the Deutsch algorithm and the Grover search algorithm, we will adress the fact that quantum information processing can be more advantageous than classical algorithms. Lastly, we will focus on the construction of the optical networks to fuse photonic W states, that is the main subject of this work. For this purpose, we will examine the previous works that use optical setups, and then propose two methods fusing two W states. The rst proposal consists of two cascaded To oli gates and the basic fusion gate whereas the second proposal consists of a To oli and a cNOT gates together with the basic fusion gate. We will use some theoretical and experimental results to show that our setups are more realizable with current photonics technology. We will also talk about why creating large-scale W states is important by pointing out their unique superpositions.

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