arXiv subjects

Deepak

Publications and source records attributed to Deepak.

At least 19 recordsLinked to original sources

arXiv2026

Performance of a two-mode coherent superposed channel in continuous-variable quantum teleportation

Glauber's coherent state is denoted by $\ket{\alpha}$ and its two-mode extension is represented by $\ket{\alpha,\beta}$. In this work, we introduce a two-mode superposition operator $A=tab+ra^\dagger b^\dagger$, whose action on the two-mode coherent state produces the two-mode coherent superposed quantum state $\ket{\psi}=(tab+ra^\dagger b^\dagger)\ket{\alpha,\beta}$. We investigate the nonclassicality and quantum non-Gaussianity of this state by means of the Wigner distribution and Wigner logarithmic negativity. Once its intrinsic nonclassical and non-Gaussian structure is established, the state is employed as the entangled resource in the Braunstein-Kimble continuous-variable (CV) teleportation protocol. We compute the ideal teleportation fidelity for coherent and squeezed inputs and analyze how the strengths of nonclassicality and non-Gaussianity influence the teleportation efficiency. Our results identify specific parameter regimes where enhanced non-Gaussian features or increased nonclassicality enable fidelities beyond the classical threshold, thereby revealing the operational significance of engineered two-mode quantum states in CV quantum information processing.

quant-ph↗

arXiv2025

Machine Learning Power Side-Channel Attack on SNOW-V

This paper demonstrates a power analysis-based Side-Channel Analysis (SCA) attack on the SNOW-V encryption algorithm, which is a 5G mobile communication security standard candidate. Implemented on an STM32 microcontroller, power traces captured with a ChipWhisperer board were analyzed, with Test Vector Leakage Assessment (TVLA) confirming exploitable leakage. Profiling attacks using Linear Discriminant Analysis (LDA) and Fully Connected Neural Networks (FCN) achieved efficient key recovery, with FCN achieving > 5X lower minimum traces to disclosure (MTD) compared to the state-of-the-art Correlational Power Analysis (CPA) assisted with LDA. The results highlight the vulnerability of SNOW-V to machine learning-based SCA and the need for robust countermeasures.

cs.CR↗

arXiv2024

Unitarity Bound on Extended Higgs Sector with Higher Dimensional Operator

We study the perturbative unitarity bound given by higher dimensional bosonic operators up to dim-6 for the two-Higgs-doublet model (2HDM). They lead to new physics beyond the Standard Model. We point out that such operators can lead to a larger cross-section in the vector boson fusion channels for the scalars, compared to the tree-level 2HDM. We have obtained limits on a few bosonic operators up to dim-6 for 2HDM, by ensuring unitarity of the S-matrix.

hep-ph↗

arXiv2024

Stellar substructures in the Galactic disc and halo: Properties, origins, and evolution

Spatial, kinematic, and orbital properties, along with ages and chemical compositions of the thin disc, thick disc, and various stellar substructures in the halo, are studied based on data from the LAMOST and Gaia surveys. The star formation in the Galactic thin and thick disc, with peak metallicities of $-0.20$ and $-0.45$ dex, is found to have peaked about 5.5 and 12.5 Gyr ago, respectively. The thin disc is also found to have experienced an initial star formation burst about 12.5 Gyr ago. The pro-grade population Splash and hot-disc (HD), with peak metallicity of about $-0.60$ and $-0.43$, are found to be about 13.03 and 12.21 Gyr old, respectively, with peak eccentricity of 0.70 and 0.35, are understood to be of in situ origin. The Gaia-Enceladus/Sausage (GE/S), Thamnos, and Sequoia, with peak metallicity of about $-1.31$, $-1.36$, and $-1.56$, are found to be about 11.66, 12.89, and 12.18 Gyr old, respectively, and are understood to be remnants of dwarf galaxies merged with the Milky Way. The HD, Splash, and Thamnos are found to have experienced chemical evolution similar to the thick disc while GE/S, Sequoia, and Helmi stream are found to have experienced distinct chemical enrichment of iron and $\alpha$-process elements.

astro-ph.GA↗

arXiv2024

Analyzing performance of $f$-deformed displaced Fock state in continuous-variable quantum teleportation

Performing non-Gaussian operations, namely photon addition, photon subtraction, photon-addition-then-subtraction, photon-subtraction-then-addition can successfully enhance the fidelity of the continuous-variable quantum teleportation. However, a shortcoming of these non-Gaussian resources is that they are probabilistic in nature. In this article, we investigate the success probability of the non-Gaussian resources for optimal performance of the ideal teleportation protocol. To this end, we first derive the analytical expression for the two-mode entangled channel having $f$-deformed displaced Fock state or photon-added displaced Fock state or photon-subtracted displaced Fock state at one port and vacuum at another port of a symmetric beam-splitter. The generalized displaced Fock states are obtained by replacing the conventional bosonic functions by the nonlinear $f$-deformed operators such as $A=af(a^\dagger a)$ and $B=af(a^\dagger a)^{-1}$. The Wigner characteristic functions describing these three aforementioned non-Gaussian states are determined and utilized to attain the teleportation fidelity for input coherent and squeezed vacuum states. It is found that the nonlinear substitution leads to an enhancement in teleportation fidelity beyond the threshold limit. Moreover, the entangled photon-subtracted displaced Fock state demonstrates maximum efficiency as a quantum channel for teleporting single-mode coherent and squeezed states. We provide the squeezing regime values corresponding to the optimal performance of the non-Gaussian states considered, which will be of significant interest to the experimental fraternity. Further, we show that the entangled photon-added displaced Fock states have larger amount of entanglement but the entangled photon-subtracted displaced Fock states have stronger Einstein-Podolsky-Rosen correlation.

quant-ph↗

arXiv2024

On the Metallicity Gradients in the Galactic Disk using Open Clusters

We study the metallicity distribution and evolution in the Galactic disk based on the largest sample of open star clusters in the Galaxy. From the catalogue of 1879 open clusters in the range of Galactocentric distance (R_GC) from 4 to 20 kpc, we investigate the variation of metallicity in the Galactic disk as functions of R_GC, vertical distance (Z), and ages of the clusters. In the direction perpendicular to the Galactic plane, variation in metallicity is found to follow a stepped linear relation. We estimate a vertical metallicity gradient d[Fe/H]/dZ of -0.545+/-0.046 dex/kpc for |Z| < 0.487 kpc, and -0.075+/-0.093 dex/kpc for 0.487 < |Z| < 1.8 kpc. On average, metallicity variations above and below the Galactic plane are found to change at similar rates. The change in metallicity in the radial direction is also found to follow a two-function linear relation. We obtain a radial metallicity gradient d[Fe/H]/d[R_GC] of -0.070+/-0.002 dex/kpc for 4.0<R_GC<12.8 kpc, and -0.005+/-0.018 dex/kpc for 12.8< R_GC < 20.5 kpc which clearly shows a strong variation in the metallicity gradient when moving from the inner to the outer Galactic disk. Age-metallicity relation (AMR) is found to follow a steeper negative slope of -0.031+/-0.006 dex/Gyr for clusters older than 240 Myr, however, there is some hint of positive metallicity age gradient for younger clusters.

astro-ph.GA↗

arXiv2023

Detecting Nonclassicality and quantum non-Gaussianity of photon subtracted displaced Fock state

In this paper, a quantitative investigation of the non-classical and quantum non-Gaussian characters of the photon-subtracted displaced Fock state $|{\psi}\rangle=a^kD(\alpha)|{n}\rangle$, where $k$ is number of photons subtracted, $n$ is Fock parameter, is performed by using a collection of measures like Wigner logarithmic negativity, linear entropy potential, skew information based measure, and relative entropy of quantum non-Gaussianity. It is noticed that the number of photons subtracted ($k$) changes the nonclassicality and quantum non-Gaussianity in a significant amount in the regime of small values of the displacement parameter whereas Fock parameter ($n$) presents a notable change in the large regime of the displacement parameter. In this respect, the role of the Fock parameter is found to be stronger as compared to the photon subtraction number. Finally, the Wigner function dynamics considering the effects of photon loss channel is used to show that the Wigner negativity can only be exposed by highly efficient detectors.

quant-ph↗

arXiv2023

General expansion of natural power of linear combination of Bosonic operators in normal order

In quantum mechanics, bosonic operators are mathematical objects that are used to represent the creation ($a^\dagger$) and annihilation ($a$) of bosonic particles. The natural power of a linear combination of bosonic operators represents an operator $(a^\dagger x+ay)^n$ with $n$ as the exponent and $x,\,y$ are the variables free from bosonic operators. The normal ordering of these operators is a mathematical technique that arranges the operators so that all the creation operators are to the left of the annihilation operators, reducing the number of terms in the expression. In this paper, we present a general expansion of the natural power of a linear combination of bosonic operators in normal order. We show that the expansion can be expressed in terms of binomial coefficients and the product of the normal-ordered operators using the direct method and than prove it using the fundamental principle of mathematical induction. We also derive a formula for the coefficients of the expansion in terms of the number of bosons and the commutation relation between the creation and annihilation operators. Our results have important applications in the study of many-body systems in quantum mechanics, such as in the calculation of correlation functions and the evaluation of the partition function. The general expansion presented in this paper provides a powerful tool for analyzing and understanding the behavior of bosonic systems, and can be applied to a wide range of physical problems.

quant-ph↗

arXiv2023

Lower-vs-Higher Order Non-classicality of Photon-added Bell-type Entangled Coherent States

We compare the lower and higher order non-classicality of a class of the photon-added Bell-type entangled coherent states (PBECS) got from Bell-type entangled coherent states using creation operators. We obtained lower and higher order criteria namely Mandel's $Q_m^l$, antibunching $d_h^{l-1}$, Subpoissioning photon statistics $D_h(l-1)$ and Squeezing $S(l)$ for the states obtained. Further we observe that first three criteria does not gives non-classicality for any state and higher order criteria gives very high positive values for all values of parameters. Also the fourth or last criterion $S(l)$ gives non-classicality for lower order as well as higher order.

quant-ph↗

arXiv2023

A comparative study of higher-order nonclassicalities of photon-added-then-subtracted and photon-subtracted-then-added quantum states

In the present paper, we have studied the higher as well as the lower-order nonclassicalities of photon-added-then-subtracted and photon-subtracted-then-added thermal and even coherent states. Different criteria such as Mandel's function ($Q_M^{(l)}$), higher-order antibunching ($d_h^{(l-1)}$), sub-Poissonian photon statistics ($D_h^{(l-1)}$), higher-order squeezing ($S^{(l)}$), Husimi function ($Q$), Agarwal-Tara criteria ($A_3$) and Klyshko's condition ($B(m)$) are used to witness the nonclassical feature of these states. Many of these conditions established that the considered states are highly nonclassical. It is also realized that the non-Gaussian photon-addition-then-subtraction operation is preferred over the photon-subtraction-then-addition for developing nonclassicality.

quant-ph↗

arXiv2023

Realistic continuous-variable quantum teleportation using a displaced Fock state channel

We investigate ideal and non-ideal continuous-variable quantum teleportation protocols realized by using an entangled displaced Fock state resource. The characteristic function formulation is applied to measure the relative performance of displaced Fock state for teleporting squeezed and coherent states. It is found that for such single-mode input fields, the average fidelity remains at the classical threshold, suggesting that the displaced Fock states are not advantageous for teleportation. We also discuss the major decoherence effects, caused by the inaccuracy in Bell measurements and photon losses for the propagation of optical fields via fibre channels. The changes in the teleportation fidelity are described by adjusting the gain factor ($g$), reflectivity ($R$), mode damping ($\tau$), and the number of thermal photons ($n_\mathrm{th}$). The possibility of successful teleportation can be optimized by fixing these realistic parameters.

quant-ph↗

arXiv2023

Nonclassical properties of a deformed atom-cavity field state

We analyze here a nonclassical state produced by an atom-cavity field interaction. The two-level atom is passed through the single-mode electromagnetic cavity field. By deforming the field operators and introducing nonlinearity to the classic Jaynes-Cummings model, we explore the system in respect of a nonlinear Hamiltonian. Assuming that the atom is in an excited state and the field is in a coherent state initially, the analytic expression for the state vector of the entire system state vector is obtained. With the help of the derived state vector, we calculate the photon number distribution, Mandel's $Q_M$ parameter, Wigner function, anti-bunching, squeezing properties and $Q$ function etc.

quant-ph↗

arXiv2023

Detecting nonclassicality and non-Gaussianity of a coherent superposed quantum state

In this paper, we investigate the nonclassicality and non-Gaussianity of a coherent superposed quantum state (CSQS) which is obtained by applying a coherent superposition of field annihilation ($a$) and creation ($a^\dagger$) operators, $N(ta+ra^\dagger)$ to a classical coherent state $|\alpha\rangle$, where $t$ and $r$ are scalars with $t^2+r^2=1$. Such an operation, when applied on states having classical characters, introduces strong nonclassicality. We use different criteria to check the nonclassicality and non-Gaussianity of the considered quantum state. We first compute the Wigner function of CSQS. To study the nonclassicality of the considered state we further use (i) linear entropy (LE) (ii) Wigner logarithmic negativity (WLN) and (iii) skew information based measure. Relative entropy based measure is considered to analyze the variation in non-Gaussianity of CSQS. Finally, the dynamics of the Wigner function evolving under the photon loss channel is addressed to probe the effect of noise on nonclassicality as well as non-Gaussianity of CSQS.

quant-ph↗

arXiv2023

Lower- versus higher-order nonclassicalities for a coherent superposed quantum state

A coherent state is defined conventionally in different ways such as a displaced vacuum state, an eigenket of annihilation operator or as an infinite dimensional Poissonian superposition of Fock states. In this work, we describe a superposition $(ta+ra^\dagger)$ of field annihilation and creation operators acting on a continuous variable coherent state $|{\alpha}\rangle$ and specify it by $|\psi\rangle$. We analyze the lower- as well as the higher-order nonclassical properties of $|\psi\rangle$. The comparison is performed by using a set of nonclassicality witnesses (e.g., higher-order photon-statistics, higher-order antibunching, higher-order sub-Poissonian statistics, higher-order squeezing, Agarwal-Tara parameter, Klyshko's condition and a relatively new concept, matrix of phase-space distribution). It is found that higher-order criteria are much more efficient to detect the presence of nonclassicality as compared to lower-order conditions.

quant-ph↗

arXiv2022

A comparison between higher-order nonclassicalities of superposition engineered coherent and thermal states

We consider an experimentally obtainable SUP operator, defined by using a generalized superposition of products of field annihilation ($a$) and creation ($a^\dagger$) operators of the type, $A = saa^\dagger+t{a^\dagger}a$ with $s^2+t^2=1$. We apply this SUP operator on coherent and thermal quantum states, the states thus produced are referred as SUP-operated coherent state (SOCS) and SUP-operated thermal state (SOTS), respectively. In the present work, we report a comparative study between the higher-order nonclassical properties of SOCS and SOTS. The comparison is performed by using a set of nonclassicality witnesses (e.g., higher-order antiubunching, higher-order sub-Poissonian photon statistics, higher-order squeezing, Agarwal-Tara parameter, Klyshko's condition). The existence of higher-order nonclassicalities in SOCS and SOTS have been investigated for the first time. In view of possible experimental verification of the proposed scheme, we present exact calculations to reveal the effect of non-unit quantum efficiency of quantum detector on higher-order nonclassicalities.

quant-ph↗

arXiv2021

Lithium in red giants: the roles of the He-core flash and the luminosity bump

Lithium abundances for red giants in the GALAH DR3 survey are studied. The rare examples of Li-enriched stars with abundances A(Li) $\geq 1.5$ are confirmed to be He-core burning stars belonging to or evolved from the red clump with similar masses and metallicity: $M\simeq 1.1\pm0.2{\rm M_\odot}$ and [Fe/H] $\simeq-0.3\pm0.3$. Li enrichment over the Li abundance present in a star's predecessor at the tip of the red giant branch likely occurs in all these red clump stars. Examination of the elemental abundances (C to Eu) in the GALAH catalogue shows no anomalous abundances in red clump giants and, in particular, no dependence on the Li abundance, which ranges over at least five dex. Lithium synthesis is attributed to the He-core flash occurring in stars at the tip of the red giant branch. Models from the Modules for Experiments in Stellar Astrophysics (MESA) match the observed evolution of these stars along the red giant branch and to the red clump but only at the low effective temperature end of the observed spread of red clump giants. Run of Li abundance on the red giant branch is fairly well reproduced by MESA models. A speculation is presented that the series of He-core flashes not only leads to $^7$Li synthesis from a star's internal reservoir of $^3$He but also may lead to internal restructuring leading to the observed effective temperature spread of red clump stars at about a constant luminosity. Giants exhibiting marked Li enrichments are not found at other evolutionary phases and, in particular, not directly associated with the luminosity bump on the red giant branch for which the Li abundance increase does not exceed 0.3 dex.

astro-ph.SR↗

arXiv2021

Lithium abundances and asteroseismology of red giants: understanding the evolution of lithium in giants based on asteroseismic parameters

In this study, we explore the evolution of lithium in giant stars based on data assembled from the literature on asteroseismology and Li abundances for giants. Our final sample of 187 giants consists of 44 red giant branch (RGB), 140 core He-burning (CHeB) and three giants with an unclassified evolutionary phase. For all 187 stars, the seismic parameters $\nu\rm_{max}$ (frequency of maximum oscillation power) and $\Delta \nu$ (large frequency spacing) are available, while $\Delta \Pi\rm_{1}$ (the asymptotic gravity-mode period spacing) is available for a subset of 64. For some of the CHeB giants, mass estimates from the asteroseismic scaling relations are found to be underestimated when compared with mass estimates from isochrones based on seismic data. Whilst most of the Li-rich giants in the sample have masses less than 1.5 $M_\odot$, they are also present up to and beyond the maximum mass expected to have suffered a core He-flash, i.e. $M$ $\leq$ 2.25 $M_\odot$: this suggests contributions from other processes towards Li enrichment. To understand the evolution of giants in the $\Delta \Pi\rm_{1}$ $-$ $\Delta \nu$ plane, we use the {\it Modules for Experiments in Stellar Astrophysics} models which show the presence of mini He-flashes following the initial strong core He-flash. From the distribution of A(Li) as a function of $\Delta \nu$, which is similar to the distribution of A(Li) as a function of luminosity, we find no indication of Li enrichment near the luminosity bump. Also, A(Li) trends to $\sim$ -1.5 dex near the RGB tip. The data also suggest a decrease in A(Li) with an increase in $\Delta \Pi\rm_{1}$ for CHeB giants.

astro-ph.SR↗

arXiv2020

Abundance analyses of Li-enriched and normal giants in the GALAH survey

Compositions of lithium-enriched and normal giants among the GALAH survey are compared. Except for Li, the only detectable abundance difference between lithium-enriched and normal giants among the investigated elements from carbon to europium occurs for carbon. Among Li-rich giants with A(Li) = 1.8 to 3.1, the C deficiency is very similar to that reported for the normal giants (with A(Li) $<$ 1.8) where the slight C deficiency arises from the first dredge-up. Carbon is slightly under abundant relative to normal giants among the super Li-rich giants where the Li abundance exceeds A(Li) = 3.2. The C abundance as well as the $^{12}$C/$^{13}$C ratios from the literature suggest that addition of Li to create a Li-rich giant may occur independently of the abundance changes wrought by the first dredge-up. Creation of a super Li-rich giant, however, appears to occur with additional CN-cycle conversion of C to N. The probability of becoming a Li-rich giant is approximately independent of a star's mass, although the majority of the Li-rich giants are found to be low mass ($M \leq$ 2 M$_\odot$). The frequency of occurrence of Li-enriched giants among normal giants is about one percent and slightly dependent on metallicity ([Fe/H]). Li-enriched and normal giants are found to have similar projected rotational velocity which suggest that Li-enrichment in giants is not linked to scenarios such as mergers and tidal interaction between binary stars.

astro-ph.SR↗