arXiv subjects

C. Sudheesh

Publications and source records attributed to C. Sudheesh.

At least 19 recordsLinked to original sources

arXiv2026

Chaos Gated Tunneling Drives Molecular Reactivity in Astrophysical Environments

Accurate modeling of ion-molecule reaction networks is essential for understanding the chemical evolution of planetary ionospheres, particularly for giant planets where proton-transfer chains drive atmospheric composition. However, predicting reaction rates in these ultracold environments remains a challenge due to the non-trivial interplay between vibrational dynamics and quantum tunneling. In this work we present a chaos-diagnostic framework that integrates multireference electronic structure theory, Adiabatic Gauge Potentials (AGP), and Random Matrix Theory (RMT) to characterize the microscopic dynamics of proton transport. Using the formation of H+3 and the proton-bound cluster H+5 as representative model systems relevant to Jovian atmospheres, we demonstrate that the transition state acts as a dynamical bottleneck where quantum chaos is notably suppressed, effectively enhancing tunneling probabilities. We introduce a fragility index based on the AGP slope to quantify how specific vibrational modes reintroduce chaos and suppress reactivity. This diagnostic approach offers a generalizable, data-driven metric for identifying vibrationally gated pathways in complex astrochemical networks, providing a theoretical basis for refining kinetic models of planetary and interstellar plasmas

physics.chem-ph↗

arXiv2024

Wave packet dynamics of entangled q-deformed states

This paper explores the wave packet dynamics of a math-type q- deformed field interacting with atoms in a Kerr-type nonlinear medium. The primary focus is on the generation and dynamics of entanglement using the q- deformed field, with the quantification of entanglement accomplished through the von Neumann entropy. Two distinct initial q-deformed states, the q-deformed Fock state, and the q-deformed coherent state, are investigated. The entanglement dynamics reveal characteristics of periodic, quasi-periodic, and chaotic behavior. Non-deformed initial states display wave packet near revivals and fractional revivals in entanglement dynamics while introducing q-deformation eliminates these features. The q-deformation significantly influences wave packet revivals and fractional revivals, with even a slight introduction causing their disappearance. For large values of q, the entanglement dynamics exhibit a chaotic nature. In the case of a beam splitter-type interaction applied to the initial deformed Fock state, an optimal deformation parameter q is identified, leading to maximum entanglement exceeding the non-deformed scenario.

quant-ph↗

arXiv2023

Janus-faced tomograms and retrieval of quadrature moments for $q$-deformed states

In this work, we derive the optical tomograms of various $q$-deformed quantum states. We found that the optical tomograms of the states under consideration exhibit a fascinating `Janus faced' nature, irrespective of the deformation parameter $q$. We also derived a general method to extract the quadrature moments from the optical tomograms of any $q$-deformed states. We also note that this technique can be used in high-precision experiments to observe deviations from the standard quantum mechanical behavior.

quant-ph↗

arXiv2023

Homodyne nonclassical area as a nonclassicality indicator

We propose a legitimate and easily computable nonclassicality indicator for the states of electromagnetic fields based on the standard deviation in the measurement of the homodyne rotated quadrature operator. The proposed nonclassicality indicator is the nonclassical area projected by the optical tomogram of the quantum state of light on the optical tomographic plane. If the nonclassical area projected by the optical tomogram of a quantum state is greater than zero, the state is nonclassical, and the area is zero for the pure classical state. It is also noted that the nonclassical area of a quantum state increases with an increase in the strength of nonclassicality inducing operations on the state such as squeezing, photon addition, etc. We have tested the validity of the nonclassical area measure by calculating the same for certain well-known nonclassical states and found that essential features of the nonclassicality shown by the states are captured in the nonclassical area. We have also shown that the nonclassical area is robust against environment-induced decoherence of the states. Nonclassical area projected by the optical tomogram of a quantum state of light is experimentally tractable using the balanced homodyne detection of the quadrature operator of the field, avoiding the reconstruction of the density matrix or the quasiprobability distribution of the state.

quant-ph↗

arXiv2021

Construction of Quantum Target Space from World-Sheet States using Quantum State Tomography

In this paper, we will construct the quantum states of target space coordinates from world-sheet states, using quantum state tomography. To perform quantum state tomography of an open string, we will construct suitable quadrature operators. We do this by first defining the quadrature operators in world-sheet, and then using them to construct the quantum target space quadrature operators for an open string. We will connect the quantum target space to classical geometry using coherent string states. We will be using a novel construction based on a string displacement operator to construct these coherent states. The coherent states of the world-sheet will also be used to construct the coherent states in target space.

hep-th↗

arXiv2021

Quadrature operator eigenstates and wavefunctions of $f$-deformed oscillators

This paper is dedicated to finding the quadrature operator eigenstates and wavefunctions of the most general $f$-deformed oscillators. A definition for quadrature operator for deformed algebra is derived to obtain the quadrature operator eigenstates. A new set of polynomials are obtained using this quadrature operator and these polynomials are used to find explicitly the wavefunctions of the deformed oscillators. We have plotted wavefunctions for three different types of deformations and compared it with the wavefunctions of the non-deformed oscillator. Our result will immensely help the research groups working in the quantum state reconstruction and quantum information theory of deformed states.

quant-ph↗

arXiv2021

Positive energy density leads to no squeezing

We consider two kinds of superpositions of squeezed states of light. In the case of superpositions of first kind, the squeezing and all higher order squeezing vanishes. However, in the case of the second kind, it is possible to achieve a maximum amount of squeezing by adjusting the parameters in the superposition. The emergence and vanishing of squeezing for the superposition states are explained on the basis of expectation values of the energy density. We show that expectation values of energy density of quantum states which show no squeezing will be always positive and that of squeezed states will be negative for some values of spacetime-dependent phase.

quant-ph↗

arXiv2020

Nonlinear dynamics of superpostion of wavepackets

We study nonlinear dynamics of superposition of quantum wavepackets in various systems such as Kerr medium, Morse oscillator and bosonic Josephson junction. The prime reason behind this study is to find out how the superposition of states influence the dynamics of quantum systems. We consider the superposition states which are potential candidates for quantum computing and quantum communication and so it is most necessary that we study the dynamics for their proper understanding and usage. Methods in nonlinear time series analysis such as first return time distribution, recurrence plot and Lyapunov exponent are used for the qualification and quantification of dynamics. We found that there is a vast change in the dynamics of quantum systems when we consider the superposition of wave packets. These changes are observed in various kinds of dynamics such as periodic, quasi-periodic, ergodic, and chaotic dynamics.

quant-ph↗

arXiv2019

Dynamics of observables in a $q$-deformed harmonic oscillator

Chaos in classical systems has been studied in plenty over many years. Although the search for chaos in quantum systems has been an area of prominent research over the last few decades, the detailed analysis of many inherently chaotic quantum systems based on expectation values of dynamical variables has not been reported in the literature. In this paper, we extend the study of dynamical behaviour using expectation values of variables to a $q$-deformed harmonic oscillator. The system is found to be periodic, quasi-periodic or chaotic depending on the values of the deformation parameter $q$ and the deformed coherent amplitude $α_{q}$, thus enabling us to explicitly classify the chaotic nature of the system on the basis of these parameters. The chaotic properties of the system are clearly illustrated through recurrence plots, power spectra, first-return-time distributions and Lyapunov exponents of the time series obtained for the expectation values of the dynamic variables.

quant-ph↗

arXiv2017

$q$-deformed quadrature operator and optical tomogram

In this letter, we define the homodyne $q$-deformed quadrature operator. Analytic expression for the wavefunctions of $q$-deformed oscillator in the quadrature basis are found. Furthermore, we compute the explicit analytical expression for the tomogram of the $q$-deformed coherent states by finding the eigenstates of the $q$-deformed quadrature operator.

quant-ph↗

arXiv2015

Visualizing revivals and fractional revivals in a Kerr medium using optical tomogram

We theoretically study the optical tomography of the time evolved states generated by the evolution of different kinds of initial wave packets in a Kerr medium. Exact analytical expression for the optical tomogram of the quantum state at any instant during the evolution of a generic initial wave packet is derived in terms of Hermite polynomials. Time evolution of the optical tomogram is discussed for three kinds of initial states: a coherent state, an $m$-photon-added coherent state, and even and odd coherent states. We show the manifestation of revival and fractional revivals in the optical tomograms of the time evolved states. We find that the optical tomogram of the time evolved state at the instants of fractional revivals shows structures with sinusoidal strands. The number of sinusoidal strands in the optical tomogram of the time evolved state at $l$-sub-packet fractional revivals is $l$ times the number of sinusoidal strands present in the optical tomogram of the initial state. We have also investigated the effect of decoherence on the optical tomograms of the states at the instants of fractional revivals for the initial states considered above. We consider amplitude decay and phase damping models of decoherence, and show the direct manifestations of decoherence in the optical tomogram.

quant-ph↗

arXiv2015

Signatures of entanglement in an optical tomogram

We theoretically study the optical tomography of maximally entangled states generated at the output modes of a beam splitter. We consider even and odd coherent states in one of the input modes and vacuum state in the other input mode of the beam splitter. We have shown that the signatures of entanglement can be observed directly in the optical tomogram of the state, without reconstructing the density matrix of the system. Two distinct types of optical tomograms are observed in any one of the output modes of the beam splitter based on the quadrature measurement in the other output mode if the output modes are entangled. The different features shown by the optical tomograms are verified by investigating the photon number statistics of the corresponding state.

quant-ph↗

arXiv2015

Entanglement dynamics of quantum states in a beam splitter

We theoretically study the dynamics of entangled states created in a beam splitter with a nonlinear Kerr medium placed into one input arm. Entanglement dynamics of initial classical and nonclassical states are studied and compared. Signatures of revival and fractional revival phenomena exhibited during the time evolution of states in the Kerr medium are captured in the entangled states produced by the beam splitter. Maximum entanglement is obtained at the instants of collapses of wave packets in the medium. Our analysis shows increase in entanglement with increase in the degree of nonclassicality of the initial states considered. We show that the states generated at the output of the beam splitter using initial nonclassical states are more robust against decoherence, due to photon absorption by an environment, than those formed by an initial classical state.

quant-ph↗

arXiv2015

Fractional revivals of superposed coherent states

We study the dynamics of superposed wave packets in a specific nonlinear Hamiltonian which models the wave packet propagation in Kerr-like media and the dynamics of Bose-Einstein condensates. We show the dependence of initial wave packet superposition on fractional revival times using analysis based on the expectation values, Rényi entropy and Wigner function. We also show how the selective identification of fractional revivals using moments of appropriate observables depends on the number of wave packets present in the initial state.

quant-ph↗

arXiv2009

Recurrence properties of quantum observables in wave packet dynamics

We investigate the recurrence properties of the time series of quantum mechanical expectation values, in terms of two representative models for a single-mode radiation field interacting with a nonlinear medium. From recurrence-time distributions, return maps and recurrence plots, we conclude that the dynamics of appropriate observables pertaining to the field can vary from quasiperiodicity to hyperbolicity, depending on the extent of the nonlinearity and of the departure from coherence of the initial state of the field. We establish that, in a simple bipartite model in which the field is effectively an open quantum system, a decaying exponential recurrence-time distribution, characteristic of a hyperbolic dynamical system, is associated with chaotic temporal evolution as characterized by a positive Liapunov exponent.

quant-ph↗

arXiv2007

Complex solitons with power law behaviour in Bose-Einstein condensates near Feshbach resonance

Complex, localized stable solitons, characterized by a power law behaviour, are found for a quasi-one-dimensional Bose-Einstein condensate near Feshbach resonance. Both dark and bright solitons can be excited in the experimentally allowed parameter domain, when two and three-body interactions are respectively repulsive and attractive. These solutions are obtained for non-zero chemical potential, unlike their unstable real counterparts which exist in the limit of vanishing $μ$. The dark solitons travel with constant speed, which is quite different from the Lieb mode, where profiles with different speeds, bounded above by sound velocity can exist for specified interaction strengths.

cond-mat.other↗

arXiv2007

Non-classical effects in wave packet dynamics

Treating the ideal coherent state as a reference state, the effects due to departure from coherence of an initial wave packet propagating through a nonlinear medium, were examined, specifically in the context of non-classical effects such as revivals, fractional revivals, squeezing and higher-order squeezing during its temporal evolution. Further, these studies were extended to examine the role of quantum entanglement in bipartite systems. The dynamics of quantum expectation values were tracked carefully in various cases and the conditions under which a wave packet spreads chaotically, were investigated.

quant-ph↗

arXiv2007

Ergodicity properties of quantum expectation values in entangled states

Using a model Hamiltonian for a single-mode electromagnetic field interacting with a nonlinear medium, we show that quantum expectation values of subsystem observables can exhibit remarkably diverse ergodic properties even when the dynamics of the total system is regular. The time series of the mean photon number is studied over a range of values of the ratio of the strength $γ$ of the nonlinearity to that of the inter-mode coupling $g$. We obtain the power spectrum, estimate the embedding dimension of the reconstructed phase space and the maximal Liapunov exponent $λ_{\rm max}$, and find the recurrence-time distribution of the coarse-grained dynamics. The dynamical behavior ranges from quasiperiodicity (for $γ/g \ll 1$) to chaos as characterized by $λ_{\rm max} > 0$ (for $γ/g \gtrsim 1$), and is interpreted.

quant-ph↗