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Gourab Das

Publications and source records attributed to Gourab Das.

6 recordsLinked to original sources

From Forgeries to Foundation Models: A Systematic Survey of Identity Document Attack and Detection

Identity document forgery has undergone a fundamental capability shift: generative AI tools now enable high-fidelity document synthesis and field-level manipulation with minimal technical expertise, while detection methods remain constrained by benchmarks that do not reflect this threat. The resulting attack surface spans physical presentation, digital injection, and fully generative synthesis, introducing distinct forensic failure modes that require a unified threat model and evaluation framework. This survey provides, to our knowledge, the first unified treatment of Presentation Attacks, Digital Injection Attacks, and GenAI-driven synthesis within a single identity verification threat model. We trace detection methodologies from rule-based heuristics through forensic localisation, injection-aware pipelines, foundation models, and few-shot frameworks. A systematic audit of public datasets from 2019--2025 exposes a persistent Reality Gap between benchmark conditions and operational deployment. We further analyse large multimodal models for identity document manipulation, identifying Script-Dependent Generative Instability (SDGI) as a recurring typographic failure mode in non-Latin script inpainting. Finally, zero-shot benchmarking on unseen synthesised ID cards shows that even the strongest publicly available models achieve APCER values above 25% under security-oriented operating conditions, highlighting substantial limits in cross-domain generalisation. We conclude by outlining future directions toward forensically grounded, privacy-preserving, and legally accountable identity verification systems.

cs.CR

Mpemba as an Emergent Effect of System Relaxation

The Mpemba effect (MpE), where a far-from-equilibrium state of a system relaxes faster compared to a state closer to it, is a well-known counterintuitive phenomenon in classical and quantum systems. Various system-specific theories have been proposed to explain this anomalous behavior in driven systems, though the fundamental mechanism of MpE in undriven systems, where MpE was first observed, remains unresolved. This paper provides a generic model of MpE for a quantum spin-$1/2$ system following Markovian relaxation dynamics, regardless of system structure or environment. The key lies in the overlap of initial states with the fast relaxation mode; here, the constituents create a fast decay mode via interaction through the shared environment to show MpE, indicating that MpE happens due to the collective behavior of the system. I also show that a system with anisotropic relaxation naturally exhibits MpE, even without a shared environment among the particles.

quant-ph

Discrete Time Crystals in Noninteracting Dissipative Systems

Many-body quantum systems, under suitable conditions, exhibit time-translation symmetry breaking and settle in a discrete time crystalline (DTC) phase -- an out-of-equilibrium quantum phase of matter. The defining feature of DTC is a robust subharmonic response. However, the DTC phase is fragile in the presence of environmental dissipation. Here, we propose and exemplify a DTC phase in a noninteracting system that owes its stability to environmental dissipation. The lifetime of this DTC is independent of initial conditions and the size of the system, though it depends on the frequency of the external driver. We experimentally demonstrate this realization of DTC using Nuclear Magnetic Resonance spectroscopy.

quant-ph

Robust control of Z-source inverter operated BLDC motor using Sliding Mode Control for Electric Vehicle applications

The rapid development and expansion of the EV market marked by the advent of third decade of the 21st century has improved the possibility of a sustainable automotive future. The present EV drivetrain run by BLDC motor has become increasingly complicated thus requiring efficient and accurate controls. The paper begins with discussing the problems in existing models, the research then focuses on increasing the robustness of the system towards disturbances and uncertainties by using Sliding Mode Control to control the ZSI, which has been chosen as the main power converter topology in place of VSI or CSI. The introduction of SMC has improved the performance of the drivetrain when applied with Vehicle dynamics over a Drive Cycle.

eess.SY

A study on applications of various Energy Generation in pure Electric Vehicles: progress towards sustainability

The present work is an attempt to understand and review existing methods of energy generation in electric vehicles in the modern day context. Previous works in the field have proposed various mechanisms of energy generation that are very well adaptable to commercial scale uses and can be used as alternative power sourcing for electric vehicles having nil or very low environmental impact. The paper discusses strategies such as photovoltaic cell systems, regenerative braking, fuel cell, thermoelectric generators and micro wind-turbines with adequate propositions to select them on the basis of their suitability. The document also includes important formulas that can be used for individual modeling and designing. The paper emphasises on introducing the mechanisms that can be introduced as assistive mechanisms or secondary sources so that the range and other parameters are not compromised.

eess.SY

Efficient transfer of entanglement along a qubit chain in the presence of thermal fluctuations

Quantum communications require efficient implementations of quantum state transportation with high fidelity. Here, we consider the transport of entanglement along a chain of qubits. A series of SWAP operations involving successive pairs of qubits can transport entanglement along the chain. We report that the fidelity of the abovementioned gate has a maximum value corresponding to an optimum value of the drive amplitude in the presence of drive-induced decoherence. To incorporate environmental effect, we use a previously reported fluctuation-regulated quantum master equation [A. Chakrabarti and R. Bhattacharyya, Phys. Rev. A 97, 063837 (2018)]. The existence of an optimum drive amplitude implies that these series of SWAP operations on open quantum systems would have an optimal transfer speed of the entanglement.

quant-ph