arXiv subjects

Surajit Sen

Publications and source records attributed to Surajit Sen.

At least 19 recordsLinked to original sources

arXiv2026

Qutrit-based Synthetic Three-Level System

We present a theoretical framework based on the $SU(3)$ group to construct synthetic three-level configurations from a two-qutrit system consisting of two three-level subsystems. Utilizing its underlying algebraic structure and a set of nine $SU(3)$ entangled states, we show that the system Hamiltonian can be mapped onto an effective synthetic three-level manifold without introducing Rydberg states. We investigate the entanglement dynamics of these synthetic configurations by introducing the $SU(3)$ I-concurrence and a generalized Wootters-type $SU(3)$ concurrence as quantitative measures of entanglement in such system.

quant-ph↗

arXiv2025

ERFC: Happy Customers with Emotion Recognition and Forecasting in Conversation in Call Centers

Emotion Recognition in Conversation has been seen to be widely applicable in call center analytics, opinion mining, finance, retail, healthcare, and other industries. In a call center scenario, the role of the call center agent is not just confined to receiving calls but to also provide good customer experience by pacifying the frustration or anger of the customers. This can be achieved by maintaining neutral and positive emotion from the agent. As in any conversation, the emotion of one speaker is usually dependent on the emotion of other speaker. Hence the positive emotion of an agent, accompanied with the right resolution will help in enhancing customer experience. This can change an unhappy customer to a happy one. Imparting the right resolution at right time becomes easier if the agent has the insight of the emotion of future utterances. To predict the emotions of the future utterances we propose a novel architecture, Emotion Recognition and Forecasting in Conversation. Our proposed ERFC architecture considers multi modalities, different attributes of emotion, context and the interdependencies of the utterances of the speakers in the conversation. Our intensive experiments on the IEMOCAP dataset have shown the feasibility of the proposed ERFC. This approach can provide a tremendous business value for the applications like call center, where the happiness of customer is utmost important.

cs.CL↗

arXiv2025

Quantum Teleportation of a Single Qutrit using Two-Qutrit Entangled States

We demonstrate quantum teleportation of a qutrit system using a complete set of two-qutrit entangled states obtained from the representation theory of the SU(3) group. All measurement gates essential for end-to-end teleportation are systematically evaluated, and these are found to be non-unitary. Our approach extends Bennett's teleportation protocol to the qutrit system with minimal modifications, preserving operational simplicity and underscoring the necessity of non-unitary measurement operators in high-dimensional systems.

quant-ph↗

arXiv2025

Unitary and non-unitary operators leverage perfect and imperfect single qutrit teleportation

Teleportation, a novel scheme, initially posited by Bennett \textit{et.al}, has been studied here in the context of sending a single qutrit from Alice to Bob using two qutrit entangled channels as resources. In this paper we have considered two special two qutrit entangled states, which belong to $SU(3)$ group, as useful resources for teleportation. For the successful teleportation, these entangled states have been chosen as quantum channels shared between Alice and Bob. Another entangled basis of two qutrit states have been used as auxiliary states, which would help Alice to manipulate with her channel so that the single qutrit she holds can be successfully teleported to Bob. Bob's choices of measurement operators influence the retrieval of Alice's single qutrit.

quant-ph↗

arXiv2024

Bloch Sphere of the Qutrit System

We present a novel method to study the Bloch space of the qutrit system by examining the Bloch trajectories in it. Since such system is inherently a three-level quantum system, therefore we use the SU(3) group as the basis group to obtain the Bloch vectors of different configurations of it. The norm of the Bloch space is evaluated from the geometric consideration and also from the dynamics of the Bloch vectors and both results are found to be identical. The analysis of the dynamical evolution of the Bloch vectors reveals an additional feature that, under resonant conditions, the Bloch sphere $\mathbb{S}^{7}$ splits into two parts, a four-sphere $\mathbb{S}^{4}$ and a two-sphere $\mathbb{S}^{2}$. The Bloch trajectories of the two sectors across different configurations exhibit a range of simple to complex curves, highlighting the non-trivial structure of the Bloch space of the qutrit system.

quant-ph↗

arXiv2024

An Inequality for Entangled Qutrits in SU(3) basis

It is well-known from the representation theory of particle physics that the tensor product of two fundamental representation of SU(2) and SU(3) group can be decomposed to obtain the desired spectrum of the physical states. In this paper, we apply this tenet in case of two {\it non-local} qubits and qutrits, which leads the complete spectrum of their entangled states in their respective basis. For qutrit system, the study of their properties reveals the existence of a new $\sqrt{2}$ inequality, in addition to usual Bell-CHSH type $2\sqrt{2}$ inequality, which is significant from the experimental point of view.

quant-ph↗

arXiv2023

Resonance fluorescence in $\Lambda$, $V$ and $\Xi$ -- type three-level configurations

We theoretically study the resonance fluorescence spectra of the lambda ($\Lambda$), vee ($V$) and cascade ($\Xi$) type three-level configurations. It is shown that each system with two detuning frequencies can be modelled using the $SU(3)$ symmetry group to derive a generalized optical Bloch equation. For each configuration, this equation is solved to calculate the two-time correlation function by invoking the quantum regression theorem. The incoherent part of the power spectra gives the characteristic multi-peak fluorescence profiles which are different for different configurations. We also discuss how the dressed-state structure of such system can explain the origin of quintuplet profile of the fluorescent spectrum.

quant-ph↗

arXiv2021

Are rare rogue fluctuations generic to strongly nonlinear and non-integrable systems?

Extensive dynamical simulations are used to explore the possible existence of sudden sufficiently large energy or rogue fluctuations (RF) at late times and across short time windows in the {\it strongly nonlinear regime} of the $\beta$-Fermi-Pasta-Ulam-Tsingou (FPUT) type systems. Our studies build on a study of RF in the non-dissipative granular chain system and suggest that {\it rare RF may be generic to non-integrable, strongly nonlinear systems at late enough times}. We comment on the role of initial conditions and the intriguing influence of harmonic forces on these strongly nonlinear systems. The RF under focus here are distinct from the well known Peregrine solitons used to describe rogue waves via the weakly nonlinear Schr\"odinger equation.

nlin.PS↗

arXiv2021

Quasi-stable Localized Excitations in the \beta-Fermi Pasta Ulam Tsingou System

The lifetimes of localized nonlinear modes in both the $\beta$-Fermi-Pasta-Ulam-Tsingou ($\beta$-FPUT) chain and a cubic $\beta$-FPUT lattice are studied as functions of perturbation amplitude, and by extension, the relative strength of the nonlinear interactions compared to the linear part. We first recover the well known result that localized nonlinear excitations (LNEs) produced by a bond squeeze can be reduced to an approximate two-frequency solution and then show that the nonlinear term in the potential can lead to the production of secondary frequencies within the phonon band. This can affect the stability and lifetime of the LNE by facilitating interactions between the LNE and a low energy acoustic background which can be regarded as "noise" in the system. In the one dimensional FPUT chain, the LNE is stabilized by low energy acoustic emissions at early times; in some cases allowing for lifetimes several orders of magnitude larger than the oscillation period. The longest lived LNEs are found to satisfy the parameter dependence $\mathcal{A}\sqrt{\beta}\approx1.1$ where $\beta$ is the relative nonlinear strength and $\mathcal{A}$ is the displacement amplitude of the center particles in the LNE. In the cubic FPUT lattice, the LNE lifetime $T$ decreases rapidly with increasing amplitude $\mathcal{A}$ and is well described by the double log relationship $\log_{10}\log_{10}(T)\approx -(0.15\pm0.01)\mathcal{A}\sqrt{\beta}+(0.62\pm0.02)$.

nlin.PS↗

arXiv2020

A Compendium on General Relativity for Undergraduate Students

We give a pedagogical introduction of the essential features of General Theory of Relativity (GTR) in the format of an undergraduate (UG) project. A set of simple MATHEMATICA code is developed which enables the UG students to calculate the tensorial objects without prior knowledge of any package operation. The orbit equations of light and material particle in Minkowski and Schwarzschild spacetime are solved numerically to illustrate the crucial tests of GTR.

gr-qc↗

arXiv2020

On the generation and propagation of solitary waves in integrable and non-integrable nonlinear lattices

We investigate the generation and propagation of solitary waves in the context of the Hertz chain and Toda lattice, with the aim to highlight the similarities, as well as differences between these systems. We begin by discussing the kinetic and potential energy of a solitary wave in these systems, and show that under certain circumstances the kinetic and potential energy profiles in these systems (i.e., their spatial distribution) look reasonably close to each other. While this and other features, such as the connection between the amplitude and the total energy of the wave bear similarities between the two models, there are also notable differences, such as the width of the wave. We then study the dynamical behavior of these systems in response to an initial velocity impulse. For the Toda lattice, we do so by employing the inverse scattering transform, and we obtain analytically the ratio between the energy of the resulting solitary wave and the energy of the impulse, as a function of the impulse velocity; we then compare the dynamics of the Toda system to that of the Hertz system, for which the corresponding quantities are obtained through numerical simulations. In the latter system, we obtain a universality in the fraction of the energy stored in the resulting solitary traveling wave irrespectively of the size of the impulse. This fraction turns out to only depend on the nonlinear exponent. Finally, we investigate the relation between the velocity of the resulting solitary wave and the velocity of the impulse. In particular, we provide an alternative proof for the numerical scaling rule of Hertz type systems.

nlin.PS↗

arXiv2019

Entangled States of Qutrit Bipartite System

We develop a systematic method to construct the Bell states of a qubit bipartite system while taking $SU(2)$ group as the basis group. An alternative formulation of fidelity, called $SU(2)$ fidelity, is proposed which gives the Bell-CHSH inequality. Taking analogy from the octet theory governed by the $SU(3)$ group, it is shown that the method can be easily generalized to derive all possible entangled states and the $SU(3)$ fidelity of the higher dimensional bipartite qutrit system. The properties of these states are studied which reveal the existence of some inequalities for the qutrit bipartite system.

quant-ph↗

arXiv2019

Nonlinear normal modes in the $\beta$-Fermi-Pasta-Ulam-Tsingou chain

Nonlinear normal mode solutions of the $\beta$-FPUT chain with fixed boundaries are presented in terms of the Jacobi sn function. Exact solutions for the two particle chain are found for arbitrary linear and nonlinear coupling strengths. Solutions for the N-body chain are found for purely nonlinear couplings. Three distinct solution types presented: a linear analogue, a chaotic amplitude mapping, and a localized nonlinear mode. The relaxation of perturbed modes are also explored using $l_{1}$-regularized least squares regression to estimate the free energy functional near the nonlinear normal mode solution. The perturbed modes are observed to decay sigmoidally towards a quasi-equilibrium state and a logarithmic relationship between the perturbation strength and mode lifetime is found.

nlin.PS↗

arXiv2018

Collapse and Revival Oscillation in Double Jaynes-Cummings Model

We develop a systematic method of solving two non-interacting Jaynes-Cummings models by using the dressed state formalism in Hilbert space $\mathcal{H}_{AB}^{(2\otimes2)}$. It is shown that such model, called Double Jaynes-Cummings model (D-JCM), can be exactly solved if we take the initial bare state as the linear superposition of two Bell states. The collapse and revival oscillation, which is the standard trait of typical Jaynes-Cummings model, can be recovered if we make measurement at each local sites. Some consequence of the entanglement-induced dressing is discussed.

quant-ph↗

arXiv2017

PULSEDYN - A dynamical simulation tool for studying strongly nonlinear chains

We introduce PULSEDYN, a particle dynamics program in $C++$, to solve many-body nonlinear systems in one dimension. PULSEDYN is designed to make computing accessible to non-specialists in the field of nonlinear dynamics of many-body systems and to ensure transparency and easy benchmarking of numerical results for an integrable model (Toda chain) and three non-integrable models (Fermi-Pasta-Ulam-Tsingou, Morse and Lennard-Jones). To achieve the latter, we have made our code open source and free to distribute. We examine (i) soliton propagation and two-soliton collision in the Toda system, (ii) the recurrence phenomenon in the Fermi-Pasta-Ulam-Tsingou system and the decay of a single localized nonlinear excitation in the same system through quasi-equilibrium to an equipartitioned state, and SW propagation in chains with (iii) Morse and (iv) Lennard-Jones potentials. We recover well known results from theory and other numerical results in the literature. We have obtained these results by setting up a parameter file interface which allows the code to be used as a black box. Therefore, we anticipate that the code would prove useful to students and non-specialists. At the same time, PULSEDYN provides scientifically accurate simulations thus making the study of rich dynamical processes broadly accessible.

physics.comp-ph↗

arXiv2017

The equilibrium phase in heterogeneous Hertzian chains

We examine the long-term behaviour of non-integrable, energy-conserved, 1D systems of macroscopic grains interacting via a contact-only generalized Hertz potential and held between stationary walls. We previously showed that in homogeneous configurations of such systems, energy is equipartitioned at sufficiently long times, thus these systems ultimately reach thermal equilibrium. Here we expand on our previous work to show that heterogeneous configurations of grains also reach thermal equilibrium at sufficiently long times, as indicated by the calculated heat capacity. We investigate the transition to equilibrium in detail and introduce correlation functions that indicate the onset of the transition.

cond-mat.stat-mech↗

arXiv2017

Long-term behaviour of Hertzian chains between fixed walls is really equilibrium

We examine the long-term behaviour of non-integrable, energy-conserved, 1D systems of macroscopic grains interacting via a contact-only generalized Hertz potential and held between stationary walls. Existing dynamical studies showed the absence of energy equipartitioning in such systems, hence their long-term dynamics was described as quasi-equilibrium. Here we show that these systems do in fact reach thermal equilibrium at sufficiently long times, as indicated by the calculated heat capacity. This phase is described by equilibrium statistical mechanics, opening up the possibility that the machinery of non-equilibrium statistical mechanics may be used to understand the behaviour of these systems away from equilibrium.

cond-mat.stat-mech↗

arXiv2016

A unified approach to $\Lambda$-, $\Xi$- and $V$-type systems with one continuum

We present a systematic approach to classify the three-level-like models with two bound states coupled to a continuum. It is shown that, when one of the discrete levels of usual three-level Lambda- ($\Lambda$), cascade ($\Xi$) or Vee ($V$)-type systems is replaced by a continuum of states, the resulting each model can be classified into three distinct categories with nine possible configurations. We show that all these models are exactly solvable. We obtain and compare the asymmetric Fano line shapes of the spectra for all the models. Our results are important for exploring new coherent effects in a variety of physical systems involving continuum-bound coupling such as photoassociation of cold atoms, plasmonics, quantum dots, photonic crystals, electromagnetic metamaterials and so on.

quant-ph↗