arXiv subjects

R. Sankaranarayanan

Publications and source records attributed to R. Sankaranarayanan.

At least 19 recordsLinked to original sources

arXiv2026

Interaction-Enhanced Ergotropy in Phase-Driven Andreev Bound State Quantum Batteries

We investigate a phase-driven quantum battery composed of two interacting Andreev bound state (ABS) units, providing a minimal superconducting platform for coherent energy storage. By analyzing the ergotropy dynamics under a superconducting phase ramp, we show that the interplay between avoided-crossing excitation and interaction-induced hybridization strongly modifies the charging process. In the high-transparency regime relevant for graphene SNS junctions, the interaction enhances the stored extractable work and generates pronounced oscillatory charging dynamics associated with coherent redistribution between coupled ABS sectors. The phase-resolved evolution further reveals optimal charging windows during the Josephson cycle, indicating the possibility of phase-programmable energy extraction through partial-cycle operation. Overall, our results identify interaction-assisted avoided-crossing dynamics as a microscopic mechanism for controllable energy storage in superconducting quantum batteries.

quant-ph↗

arXiv2026

Purity and bound energy in ancilla-assisted work extraction

We investigate ancilla-assisted work extraction in quantum batteries from the perspective of bound energy and purity. We show that the bound energy of the reduced system provides a tight upper bound to the daemonic gain and that this bound is saturated for globally pure system--ancilla states. Motivated by this relation, we introduce a purity-based gain that qualitatively predicts the daemonic gain without requiring explicit optimization over measurements. We further introduce a protocol to analyze the role of dissipation and intrinsic interactions on daemonic gain. Under a collective environment, dissipation can dynamically generate and stabilize finite daemonic gain through environment-induced correlations. In interacting systems, level crossings and spectral restructuring strongly modify the attainable gain through their influence on the accessible bound energy. Our results demonstrate that daemonic gain is governed not only by correlations, but also by the spectral structure of the underlying Hamiltonian and information loss captured by bound energy and purity.

quant-ph↗

arXiv2025

Nonlocal contributions to ergotropy: A thermodynamic perspective

Nonlocality is a defining feature of quantum mechanics and has long served as a key indicator of quantum resources since the formulation of Bell's inequalities. Identifying the contribution of nonlocality to extractable work remains a central problem in quantum thermodynamics. We address this by introducing a quantifier of nonlocal contributions to extractable work in bipartite systems. It is shown that closed form expressions can be calculated for our quantity in terms of the Schmidt coefficients. Further for strictly non-interacting Hamiltonian, the direct relationship between ergotropy and correlations is established. Our results reveal that nonlocal resources invariably enhance extractable work under non-interacting Hamiltonians, while in the presence of interactions, their contribution can either increase or diminish depending on the structure of the state and the Hamiltonian.

quant-ph↗

arXiv2025

Ergotropy Dynamics in a Dissipative Graphene Quantum Battery

We investigate ergotropy dynamics in a graphene-based quantum battery modeled as a four-level spin--valley system under different dissipative environments. The battery is charged via a Gaussian pulse and subsequently evolves under amplitude damping, dephasing, and both Markovian and non-Markovian reservoirs. We find that amplitude damping, while inducing energy loss, can stabilize non-passive steady states with finite ergotropy, whereas pure dephasing suppresses coherence and eliminates work extraction. On the other hand, non-Markovian memory slows ergotropy loss and enables partial recovery through information backflow. These results identify coherence and reservoir memory as essential resources for enhancing the long-time performance of graphene quantum batteries.

quant-ph↗

arXiv2024

Dynamics of Heisenberg XYZ spin Quantum Battery

Spin systems have been extensively studied to understand the mechanisms of quantum batteries, which have shown the ability to charge faster than classical counterparts, even in closed systems. However, the internal dynamics of quantum batteries can significantly affect their performance, making it crucial to understand the influence of various parameters. In this study, we focus on the XY Z Heisenberg spin system, examining key factors such as anisotropy in spin interactions and external magnetic field to optimize work output to ensure effective charging.

quant-ph↗

arXiv2023

Weak measurement as a tool for studying coherence and quantum correlations in bipartite systems

In this article, we study quantum coherence of bipartite state from the perspective of weak measurement, which generalizes the notion of coherence relative to measurement. The is being illustrated by computing coherence for the well-known Bell diagonal and Wener states. We have also extended our investigation on quantum correlation measure and uncertainty relation in the weak measurement regime.

quant-ph↗

arXiv2023

Continued functions and critical exponents: Tools for analytical continuation of divergent expressions in phase transition studies

Resummation methods using continued functions are implemented to converge divergent series appearing in perturbation problems related to continuous phase transitions in field theories. In some cases, better convergence properties are obtained using continued functions than diagonal Pade approximants, which are extensively used in literature. We check the reliability of critical exponent estimates derived previously in universality classes of O(n)-symmetric models (classical phase transitions) and Gross-Neveu-Yukawa models (quantum phase transitions) using new methods.

cond-mat.stat-mech↗

arXiv2022

Casimir interactions from infinite range and dilation symmetry

The Casimir interaction energy for a class of discrete self-similar configuration of parallel plates is evaluated using existing methods. The similarities to characteristics of an attractive Casimir force is deduced only at infinite range of configuration. Further, the emergence of Casimir-like energy is qualitatively described for a Gaussian model of Landau-Ginzburg scalar field. Its relevance to self-similarity in the statistical field is shown at infinite range of fluctuations.

quant-ph↗

arXiv2021

Casimir-like effect from thermal field fluctuations

Landau-Ginzburg $ϕ^4$ field theory is usually applied to systems for understanding continuous phase transitions at critical points. Here we analyze the thermal field using a similar free energy description from a statistical field theory perspective, and study fluctuations in such a field with a particular focus on realizing the thermal Casimir effect. Initially, we qualitatively describe the emergence of the Casimir-like effect using mean-field approximation and further derive it using coarse-graining of perturbative renormalization procedure in the vicinity of Gaussian-fixed point. These results may lead to further the understanding of the Casimir effect from scalar fields without employing the concept of zero-point energy in a cosmological sense.

cond-mat.stat-mech↗

arXiv2021

Continued functions and Borel-Leroy transformation: Resummation of six-loop ε-expansions from different universality classes

We handle divergent ε expansions in different universality classes derived from modified Landau-Wilson Hamiltonian. Landau-Wilson Hamiltonian can cater for describing critical phenomena on a wide range of physical systems which differ in symmetry conditions and the associated universality class. Numerically critical parameters are the most interesting physical quantities which characterize the singular behaviour around the critical point. More precise estimates are obtained for these critical parameters than previous predictions from Pade based methods and Borel with conformal mapping procedure. We use simple methods based on continued functions and Borel-Leroy transformation to achieve this. These accurate results are helpful in strengthening existing conclusions in different ϕ^4 models.

cond-mat.stat-mech↗

arXiv2021

Fidelity based purity and coherence for quantum states

Purity and coherence of a quantum state are recognized as useful resources for various information processing tasks. In this article, we propose a fidelity based valid measure of purity and coherence monotone and establish a relationship between them. This formulation of coherence is extended to quantum correlation relative to measurement. We have also studied the role of weak measurement on purity.

quant-ph↗

arXiv2021

Continued functions and perturbation series: Simple tools for convergence of diverging series in $O(n)$-symmetric $ϕ^4$ field theory at weak coupling limit

We determine universal critical exponents that describe the continuous phase transitions in different dimensions of space. We use continued functions without any external unknown parameters to obtain analytic continuation for the recently derived 7- loop $ε$ expansion from $O(n)$-symmetric $ϕ^4$ field theory. Employing a new blended continued function, we obtain critical exponent $α=-0.0121(22)$ for the phase transition of superfluid helium which matches closely with the most accurate experimental value. This result addresses the long-standing discrepancy between the theoretical predictions and precise experimental result of $O(2)$ $ϕ^4$ model known as "$λ$-point specific heat experimental anomaly". Further we have also examined the applicability of such continued functions in other examples of field theories.

cond-mat.stat-mech↗

arXiv2020

Measurement Induced Nonlocality Quantified by Hellinger Distance and weak measurements

In this article, we propose measurement-induced nonlocality (MIN) quantified by Hellinger distance using von Neumann projective measurement. The proposed MIN is a bonafide measure of nonlocal correlation and is resistant to local ancilla problem. We obtain an analytical expression of the Hellinger distance MIN for general pure and $2 \otimes n$ mixed states. In addition to comparing with similar measures, we explore the role of weak measurement in capturing nonlocal correlation.

quant-ph↗

arXiv2020

Role of virial coefficients in chemical reaction

van't Hoff equation relates equilibrium constant $K$ of a chemical reaction to temperature $T$. Though the van't Hoff plot ($\ln K$ vs $1/T$) is linear, it is nonlinear for certain chemical reactions. In this work we attribute such observations to virial coefficients.

cond-mat.stat-mech↗

arXiv2020

Quantum coherence and correlation measures based on affinity

Coherence and correlation are key features of the quantum system. Quantifying these quantities are astounding task in the framework of resource theory of quantum information processing. In this article, we identify an affinity-based metric to quantify closeness between two states. Using this metric, we introduce a valid quantum coherence measure. It is shown that the affinity based coherence measure is bounded by that based on fidelity and trace distance. Further, we propose a bipartite quantum correlation measure based on the affinity metric. The connection between the quantum correlation of states and its local coherence is established. The measure of quantumness in terms of difference of bipartite coherence and corresponding product state coherence is also identified. Finally, we interpret the operational meaning of the affinity based coherence as an upper bound of interferometric power of the quantum state.

quant-ph↗

arXiv2020

Effect of environment in Heisenberg XYZ spin model

Quantum correlation of bipartite states (beyond entanglement) in presence of environment is studied for Heisenberg XYZ spin system. It is shown that if the system is allowed to exchange energy with environment, the initial state evolves and settles down to uncorrelated state in asymptotic limit. We have also demonstrated that fidelity based measurement induced non-locality is a useful quantity in characterizing correlated quantum states.

quant-ph↗

arXiv2020

Entanglement and Measurement-induced quantum correlation in Heisenberg spin models

Correlation beyond entanglement is a subject of interest in quantum information. Here we have shown the existence of quantum correlation without entanglement in Heisenberg $XYZ$ spin model with external magnetic field, using different versions of measurement-induced nonlocality. However maximally entangled states are shown to possess maximum correlation.

quant-ph↗

arXiv2019

Dissipative optical solitons in asymmetric Rosen-Morse potential

We investigate the existence and stability of dissipative soliton solution in a system described by complex Ginzburg-Landau (CGL) equation with asymmetric complex potential, which is obtained from original parity reflection - time reversal ($\mathcal{PT}$) symmetric Rosen-Morse potential. In this study, stability of solution is examined by numerical analysis to show that solitons are stable for some parameter ranges for both self-focusing and self-defocusing nonlinear modes. Dynamical properties such as evolution and transverse energy flow for both modes are also analyzed. Obtained results are useful for experimental designs and applications in related fields.

nlin.PS↗