arXiv subjects

Debabrata Goswami

Publications and source records attributed to Debabrata Goswami.

16 recordsLinked to original sources

arXiv2026

Typed Component Algebras for Simulated Annealing and Markov-Chain Monte Carlo

Simulated annealing (SA) and fixed-temperature Markov-chain Monte Carlo (MCMC) run the same Metropolis-Hastings kernel over a tempered objective, but the variants appear as separate monolithic drivers, so improving one ingredient requires rewriting and re-verifying a whole solver. The shared kernel becomes a typed algebra of five components (objective, cooling schedule, neighborhood, move kernel, and acceptance rule) whose four local composition laws the construction checks; a single Sampler step then runs any point of the algebra. A surrogate proposal, a fitted generalized-Langevin thermostat, a quasi-Monte Carlo polish, or a noise-aware acceptance rule is implemented once and becomes available to every classical, fast, generalized, Hamiltonian, or parallel-tempered driver that shares the interface. The same typing carries the correctness artifacts: SymPy-checked reductions of Generalized SA to its Boltzmann, fast, and Metropolis limits (the reductions surfaced a sign error that had stood in the visiting-distribution literature for three decades); a TLA+ specification model-checked for four safety and two liveness properties; and a three-channel finite-precision audit showing that fixing one channel of the acceptance path does not let float16 reproduce float64 basin selection. The implementation is the open-source Rust-and-Python package anneal, with an Array-API/DLPack device boundary and a portfolio optimizer whose only argument is a budget. On the CUTEst collection under a shared work-unit budget it reaches the best observed basin on more problems than a budget-matched CMA-ES restart heuristic, while carrying the almost-sure convergence and regret guarantees that heuristic lacks. Every reported number and figure regenerates from the reproducibility package with its pinned environment.

cs.SE↗

arXiv2025

Compositional Analysis of Fragrance Accords Using Femtosecond Thermal Lens Spectroscopy

Femtosecond thermal lens spectroscopy (FTLS) is a powerful analytical tool, yet its application to complex, multi-component mixtures like fragrance accords remains limited. Here, we introduce and validate a unified metric, the Femtosecond Thermal Lens Integrated Magnitude (FTL-IM), to characterize such mixtures. The FTL-IM, derived from the integrated signal area, provides a direct, model-free measure of the total thermo-optical response, including critical convective effects. Applying the FTL-IM to complex six-component accords, we demonstrate its utility in predicting a mixture's thermal response from its composition through linear additivity with respect to component mole fractions. Our method quantifies the accords' behavior, revealing both the baseline contributions of components and the dominant, non-linear effects of highly-active species like Methyl Anthranilate. This consistency is validated across single-beam Z-scan, dual-beam Z-scan, and time-resolved FTLS measurements. The metric also demonstrates the necessity of single-beam measurements for interpreting dual-beam data. This work establishes a rapid, quantitative method for fragrance analysis, offering advantages for quality control by directly linking a mixture's bulk thermo-optical properties to its composition.

physics.chem-ph↗

arXiv2024

Comparing Femtosecond Optical Tweezers with Conventional CW Optical Tweezers

In this work, we present a comparative study between continuous-wave (CW) and pulsed optical tweezers for 250 nm, 500 nm and 1-micron radius polystyrene beads at 5 different laser powers. We have used a Ti:Sapphire (MIRA 900F) laser that can be easily switched from CW to pulsed mode of operation, so there is no change in the experimental conditions in the two cases. We have measured the difference in the trap strength in both cases by fitting the power spectrum curve with Lorentzian. As it turns out, trapping with pulsed tweezers seems to be more effective for the smaller particles and as the particle size is increased both CW and pulsed tweezers appear to be equally effective at lower average laser powers but as the power is increased pulsed tweezers do a better job at stable trapping.

physics.optics↗

arXiv2024

Two novel pure-state coherence measures in quantifying coherence

In the resource theory of coherence, the quantification of quantum-state coherence is an important task. In this regard, the key ingredients are the various coherence monotones (or measures). There are few coherence-monotone classes that solely depend on other coherence measures defined for all the pure states; in other words, they rely on the pure state coherence measures (PSCM). Here, we set forth two such novel PSCMs, and validate each of them through the fulfillment of all four necessary conditions. In addition, we delve into the most recent (as per our knowledge) coherence-monotone class based on the innovative idea of quantifying coherence in terms of pure-state coherence, further redefine it, and, through the study of convexity under mixing, justify why this coherence monotone class cannot be treated as a coherence-measure class in general.

quant-ph↗

arXiv2023

The role of molecular structure on the microscopic thermodynamics: unveiling with Femtosecond Optical Tweezers

Microscopic thermodynamic studies can elucidate specific molecular interactions. In this work, we report the microscopic thermodynamics in binary liquid mixtures, which elucidate the role of molecular structure in nonlinear solvent response using femtosecond optical tweezers (FOT). We obtain the excess thermodynamics property of mixing in various Newtonian liquid mixtures by analyzing Microrheology data from FOT. Using our noninvasive 780 nm pulse laser we have trapped micron-sized particles to show how excess viscosity and residual Gibbs free energy change due to mixing. Furthermore, we establish from this study that hydrocarbon chain length and branching can modulate microscopic thermodynamics through intermolecular interaction. This work sheds light on the relationship between thermodynamic properties and viscosity, which is of immense importance for predicting transport properties, mixing, and chemical reactions.

physics.chem-ph↗

arXiv2023

Quantifying coherence with principal diagonal elements of density matrix

Being the key resource in quantum physics, the proper quantification of coherence is of utmost importance. Amid complex-looking functionals in quantifying coherence, we set forth a simple and easy-to-evaluate approach: Principal diagonal difference of coherence (C_PDD), which we prove to be non-negative, self-normalized, and monotonic (under any incoherent operation). To validate this theory, we thought of a fictitious two-qubit system (both interacting and non-interacting) and, through the laser pulse-system interaction (semi-classical approach), compare the coherence evolution of C_PDD with the relative entropy of coherence (C_(r.e)) and l_1-norm of coherence (C_(l_1 )), in a pure-state regime. The numerical results show that the response of C_PDD is better than the other two quantifiers. To the best of our knowledge, this letter is the first to show that a set of density-matrix diagonal elements carries complete information on the coherence (or superposition) of any pure quantum state.

quant-ph↗

arXiv2020

Comparative study of the real-time optical trapping in the Rayleigh regime for continuous and pulsed lasers

Simulating real-time scenarios to predict optical trapping behavior for continuous wave (CW) as well as femtosecond pulsed lasers is a challenging problem. This is especially so, because, for a tightly focused laser, one must also include optical Kerr effect as well as thermal nonlinearity. We show here the distinct differences between CW and femtosecond pulsed laser mediated optical trapping via their effect in scattering and gradient forces in the Rayleigh regime. In our newly developed model, it will also be easier to predict the stability of the trap in real optical trapping scenario as well as provide information regarding choice of solvents, probes, and optical parameters like laser type, power range, wavelength, etc. as may the cases be.

physics.optics↗

arXiv2013

Quantum Algorithm to Solve a Maze: Converting the Maze Problem into a Search Problem

We propose a different methodology towards approaching a Maze problem. We convert the problem into a Quantum Search Problem (QSP), and its solutions are sought for using the iterative Grover's Search Algorithm. Though the category of mazes we are looking at are of the NP complete class, we have redirected such a NP complete problem into a QSP. Our solution deals with two dimensional perfect mazes with no closed loops. We encode all possible individual paths from the starting point of the maze into a quantum register. A quantum fitness operator applied on the register encodes each individual with its fitness value. We propose an oracle design which marks all the individuals above a certain fitness value and use the Grover search algorithm to find one of the marked states. Iterating over this method, we approach towards the optimum solution.

quant-ph↗

arXiv2005

Adiabatic Quantum Computing with Phase Modulated Laser Pulses

Implementation of quantum logical gates for multilevel system is demonstrated through decoherence control under the quantum adiabatic method using simple phase modulated laser pulses. We make use of selective population inversion and Hamiltonian evolution with time to achieve such goals robustly instead of the standard unitary transformation language.

quant-ph↗

arXiv2004

Towards Efficiently Solving Quantum Traveling Salesman Problem

We present a framework for efficiently solving Approximate Traveling Salesman Problem (Approximate TSP) for Quantum Computing Models. Existing representations of TSP introduce extra states which do not correspond to any permutation. We present an efficient and intuitive encoding for TSP in quantum computing paradigm. Using this representation and assuming a Gaussian distribution on tour-lengths, we give an algorithm to solve Approximate TSP (Euclidean) within BQP resource bounds. Generalizing this strategy for any distribution, we present an oracle based Quantum Algorithm to solve Approximate TSP. We present a realization of the oracle in the quantum counterpart of PP.

quant-ph↗

arXiv2004

Laser Polarization Effects in Supercontinuum Generation

We present experimental evidence of a fourth order process in electric field in supercontinuum generation. We also show laser induced polarization preference in the supercontinuum generating media. These results have become possible through the choice of isotropic and anisotropic samples interacting with ultrashort laser pulses of changing ellipticity. Laser polarization emerges as an important control parameter for the highly nonlinear phenomenon of supercontinuum generation.

quant-ph↗

arXiv2003

Ultrafast Pulse Shaping Approaches to Quantum Computing

Quantum computing exploits the quantum-mechanical nature of matter to exist in multiple possible states simultaneously. This new approach promises to revolutionize the present form of computing. As an approach to quantum computing, we discuss ultrafast laser pulse shaping, in particular, the acousto-optic modulator based Fourier-Transform pulse-shaper, which has the ability to modulate tunable high power ultrafast laser pulses. We show that optical pulse shaping is an attractive route to quantum computing since shaped pulses can be transmitted over optical hardware and the same infrastructure can be used for computation and optical information transfer. We also address the problem of extending coherence-times for optically induced processes.

quant-ph↗

arXiv2002

Laser phase modulation approaches towards ensemble quantum computing

Selective control of decoherence is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion while the even terms lead to self-induced transparency. These results also hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse-width. Such results form the basis of a robustly implementable CNOT gate.

quant-ph↗

arXiv2001

Conditions for Soliton-Like Wave Propagation in Pockels and Photorefractive Media

We study the conditions for soliton-like wave propagation in the Photorefractive (PR) and electro-optic (i.e., Pockels) material, by using Nonlinear Schrodinger (NLS) equation. The complete NLS equation is solved analytically and numerically by transforming it into the phase space. Our results clearly show the existence of both the dark and bright solitary solutions for the PR medium. Interestingly, however, we find only one bright solitary solution in the Pockels case and there is no evidence of any dark solitary solution.

physics.optics↗

arXiv2001

Coherent Control of Multiphoton Transitions with Femtosecond pulse shaping

We explore the effects of ultrafast shaped pulses for two-level systems that do not have a single photon resonance by developing a multiphoton density-matrix approach. We take advantage of the fact that the dynamics of the intermediate virtual states are absent within our laser pulse timescales. Under these conditions, the multiphoton results are similar to the single photon and that it is possible to extend the single photon coherent control ideas to develop multiphoton coherent control.

physics.optics↗

arXiv2000

Suppression of Supercontinuum Generation with Circularly Polarized Light

Controlling a nonlinear process like supercontinuum generation (SG) with the polarization-state of laser is an important demonstration of laser selectivity. We show that the threshold for SG and the total amount of supercontinuum generated depends on incident laser polarization for isotropic samples. Irrespective of the nature of the samples chosen, SG efficiency decreases as the incident laser polarization changes from linear to circular and thus, provides the first experimental demonstration of the suppression of SG with circularly polarized light. The ratio of the overall SG between the linear and circular polarization (i.e., measure of suppression) undergoes an intensity dependent decrease from large initial values to asymptotic limits, irrespective of samples.

physics.optics↗