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Preeti Sharma

Publications and source records attributed to Preeti Sharma.

12 recordsLinked to original sources
arXiv2026

Low stray-field ion pump configuration for cold atom experiments

Ion pumps used in cold-atom experiments generate stray magnetic fields that can perturb magneto-optical trapping, shift Zeeman sensitive energy levels, and introduce systematic errors in precision spectroscopy. We numerically investigate a compact low-stray-field ion pump configuration designed to reduce magnetic flux leakage through the ultrahigh-vacuum port without increasing the overall pump size. Starting from a simplified magnetic model of a standard ion pump, we study two complementary modifications: auxiliary permanent magnets surrounding the original pump magnets with opposite magnetisation, and a soft-magnetic honeycomb field stopper integrated at the pump port. The resulting combined configuration strongly reduces the magnetic flux density outside the pump. In the geometry considered here, the field at 10 mm from the UHV port is reduced by 97.9%, while the calculated reduction in effective pumping speed due to the honeycomb stopper is 17.9%. These results indicate that engineered magnetic compensation and field-guiding structures can support more compact cold-atom vacuum systems while preserving pumping performance. Further work should validate the design with nonlinear magnetostatic modelling, molecular-flow simulations, and measurements on a complete pump geometry.

physics.atom-ph↗
arXiv2025

Tailoring indistinguishability of photons using longitudinal spatial coherence

Methods to generate photons with tailored indistinguishability are central to developing photonic quantum technologies and making fundamental tests of quantum physics. This study introduces a novel method for manipulating effective longitudinal spatial coherence (LSC) of biphotons, controlling their indistinguishability in a significant manner. The experimental results show that, instead of tailoring the frequency spectrum of the interfering photons, changing their LSC also leads to controlling the width of Hong-Ou-Mandel dip as validated by the theoretical calculations. This powerful approach not only modifies the conventional wisdom claiming only frequency width responsible for indistinguishability control of photons but also positions the LSC as a promising tool for fine-tuning the longitudinal coherence of photons, thereby expanding their potential use in quantum science and technologies.

quant-ph↗
arXiv2023

Experimental generation and characterization of partially spatially coherent qubits

Partially spatially coherent qubits are more immune to turbulent atmospheric conditions than coherent qubits, which makes them excellent candidates for free-space quantum communication. In this article, we report the generation of partially spatially coherent qubits in a spontaneous parametric down-conversion (SPDC) process using a Gaussian Schell model (GSM) pump beam. For this non-linear process, we demonstrate experimentally for the first time, the transfer of spatial coherence features of the pump (classical) to the biphotons (quantum) field. Also, the spatial profiles of partially coherent qubits generated in type-I and type-II non-collinear SPDC process are experimentally observed and multi-mode nature of partially coherent photons (qubit) is ascertained. These investigations pave the way toward the efficient generation of partially spatially coherent qubits with a tunable degree of spatial coherence, which lead to wide range of applications in frontier areas such as quantum cryptography, teleportation, imaging, and lithography.

quant-ph↗
arXiv2023

Bioconvection in a phototactic algae suspension with oblique irradiation and forward anisotropic scattering

In this study, we analyze the bioconvection in a suspension of phototactic algae that exhibits anisotropic scattering. The top layer of the suspension is illuminated by oblique collimated irradiation. During the study, the bottom boundary is considered as rigid whereas the top boundary is considered stress-free. In order to solve the eigenvalue problem, the Newton-Raphson-Kantorovich finite difference method of order four is used. Linear analysis of the basic state is performed using neutral curves. The results demonstrate a change in the most unstable mode from an overstable to a stationary state or vice versa for particular parameters in response to a variation in the incidence angle. The position of the maximum basic concentration shifts toward the top of the suspension as the incidence angle is increased. In most cases, the system becomes more unstable with an increment in the incidence angle.

math.DS↗
arXiv2018

Average Case - Worst Case Tradeoffs for Evacuating 2 Robots from the Disk in the Face-to-Face Model

The problem of evacuating two robots from the disk in the face-to-face model was first introduced in [Czyzowicz et al., DISC'14], and extensively studied (along with many variations) ever since with respect to worst case analysis. We initiate the study of the same problem with respect to average case analysis, which is also equivalent to designing randomized algorithms for the problem. First we observe that algorithm $B_{2}$ of~[Czyzowicz et al., DISC'14] with worst case cost $WRS(B_{2}):=5.73906$ has average case cost $AVG(B_{2}):=5.1172$. Then we verify that none of the algorithms that induced worst case cost improvements in subsequent publications has better average case cost, hence concluding that our problem requires the invention of new algorithms. Then, we observe that a remarkable simple algorithm, $B_{1}$, has very small average case cost $AVG(B_{1}):=1+π$, but very high worst case cost $WRS(B_{1}):=1+2π$. Motivated by the above, we introduce constrained optimization problem $_2Evac_{F2F}^w$, in which one is trying to minimize the average case cost of the evacuation algorithm given that the worst case cost does not exceed $w$. The problem is of special interest with respect to practical applications, since a common objective in search-and-rescue operations is to minimize the average completion time, given that a certain worst case threshold is not exceeded, e.g. for safety or limited energy reasons. Our main contribution is the design and analysis of families of new evacuation parameterized algorithms $A(p)$ which can solve $_2Evac_{F2F}^w$, for every $w \in [WRS(B_{1}),WRS(B_{2})]$.

cs.DM↗
arXiv2015

Approximation by Modified Jain-Baskakov Operators

In the present paper we discuss the approximation properties of Jain-Baskakov operators with parameter c. The present paper deals with the modified forms of the Baskakov basis functions. We establish some direct results, which include the asymptotic formula and error estimation in terms of the modulus of continuity and weighted approximation.

math.FA↗
arXiv2015

Statistical approximation properties of Stancu type $q$-Baskakov-Kantorovich operators

In the present paper, we consider Stancu type generalization of Baskakov-Kantorovich operators based on the q-integers and obtain statistical and weighted statistical approximation properties of these operators. Rates of statistical convergence by means of the modulus of continuity and the Lipschitz type function are also established for said operators. Finally, we construct a bivariate generalization of the operator and also obtain the statistical approximation properties.

math.CA↗
arXiv2015

On approximation properties of Baskakov-Schurer-Szasz operators

In this paper, we are dealing with a new type of Baskakov-Schurer-Szasz operators (\ref{eq1}). Approximation properties of this operators are explored: the rate of convergence in terms of the usual moduli of smoothness is given, the convergence in certain weighted spaces is investigated. We study $q$-analogues of Baskakov-Schurer-Szász operators and it's Stancu generalization. In the last section, we give better error estimations for the operators (\ref{eq2}) using King type approach and obtained weighted statistical approximation properties for operator (\ref{qb})

math.FA↗
arXiv2015

On q-analogue of modified Kantorovich-type discrete-Beta operators

The present paper deals with the Stancu type generalization of the Kantorovich discrete $q$-Beta operators. We establish some direct results, which include the asymptotic formula and error estimation in terms of the modulus of continuity and weighted approximation.

math.CA↗
arXiv2012

Performance comparison of various routing protocols in different mobility models

Mobile Ad hoc Network (MANET) is a infrastructure less network in which two or more devices have wireless communication which can communicate with each other and exchange information without need of any centralized administrator. Each node in the ad hoc network acts as a router, forwarding data packets for other nodes. The main issue is to compare the existing routing protocol and finding the best one. The scope of this study is to test routing performance of three different routing protocols (AODV, OLSR and DSDV) with respect to various mobility models using NS2 simulator. In this paper the parameters used for comparison are packet delivery fraction (PDF), average end to end delay (AEED), normalized routing load (NRL) and throughput.

cs.NI↗
arXiv2012

Detection techniques of selective forwarding attacks in wireless sensor networks: a survey

The wireless sensor network has become a hot research area due its wide range of application in military and civilian domain, but as it uses wireless media for communication these are easily prone to security attacks. There are number of attacks on wireless sensor networks like black hole attack, sink hole attack, Sybil attack, selective forwarding attacks etc. in this paper we will concentrate on selective forwarding attacks In selective forwarding attacks, malicious nodes behave like normal nodes and selectively drop packets. The selection of dropping nodes may be random. Identifying such attacks is very difficult and sometimes impossible. In this paper we have listed up some detection techniques, which have been proposed by different researcher in recent years, there we also have tabular representation of qualitative analysis of detection techniques

cs.CR↗