arXiv subjects

Himangshu Prabal Goswami

Publications and source records attributed to Himangshu Prabal Goswami.

At least 19 recordsLinked to original sources

arXiv2026

Cotunneling-Assisted Redistribution of Nonpassivity in a Photosynthetic Junction

We investigate how cotunneling affects passive-state ordering in a Photosystem II reaction center modelled as a nonequilibrium molecular junction. We use a full pigment excitation manifold, with excitonic and charge-transfer rates computed within a Nakajima-Zwanzig formalism using realistic spectral densities. Cotunneling is introduced through a microscopically constructed doubly reduced acceptor state obtained from relevant quinone-side two-electron configurations, while photoexcitation is allowed into the full excitonic manifold. Passive-state permutations are quantified through ergotropy and energetic capacitance. We find that thermodynamic smoothness in ergotropy and energetic capacitance can conceal microscopic state rearrangements. Cotunneling redistributes the extractable nonequilibrium energy among the quinone acceptor, the donor-pheophytin radical pair, and excitonic states with strong contributions from pigments on the inactive branch. At high Coulomb interaction, cotunneling produces no passive-state reordering. Piecewise-linear relations among ergotropy, energetic capacitance, and mean energy further reveal the population reorderings generated by cotunneling.

physics.chem-ph↗

arXiv2026

Geometric Phonon Energy Pumping in a Layer-Hybridized Moiré Exciton Manifold

Slow cyclic modulation of an open quantum system can generate a geometric contribution to its energy transfer statistics, separable from the dynamic background. In this work we construct an experimentally anchored four state open system model for a gate-tunable WSe2/WS2 moiré exciton manifold within a population level full counting statistics framework. We first drive the system uniformly through a closed gate and pump loop and separate the geometric contribution from the dynamic background by reversing the loop direction. We then examine how this response changes with environmental rates, exciton coupling, control conditions, and static spectral broadening. A shorter cycle period followed by nonuniform traversal of the driving loop substantially improves detectability while preserving the geometric response. Combined with enhanced phonon relaxation and reduced radiative loss, this gives about a fourteenfold fixed time signal to noise gain relative to the uniform loop. Our results show that the geometric phonon response remains robust against realistic variations in the system and its environment, and that we can improve its detectability more effectively by suppressing dynamical noise through frequency modulated driving.

cond-mat.mes-hall↗

arXiv2026

Coherence Estimation Beyond the Liouvillian Gap in a Finite Nonequilibrium System

We investigate the estimation of bath-induced coherence in a finite quantum system interacting with thermal reservoirs. Enhancement of coherence estimation is transient and the estimation precision totally disappears at the steady state despite the system retaining finite coherence. By analyzing the full Liouvillian eigenspectrum, we demonstrate that the optimal sensing window emerges from the competition between identifiable contributory modes' temporal relaxation and statistical importance. Neither is the linear inverse scaling of Liouvillian gap with transient optimal time a signature of unimodal contribution to optimal sensing, nor is the existence of multimodal dynamics a signature of nonlinear scaling. The inverse Liouvillian gap does not obey any general scaling with the optimal sensing time of coherence and we prove our numerical results analytically using a general Markovian framework. We further show that coupling the finite system to a quantum cavity and maintaining a thermal bias, transforms the transient metrological optimization into a sustained steady-state resource.

quant-ph↗

arXiv2026

Collective Emission in LH2 Assembly Beyond the Point-Dipole Approximation

Collective emission in light-harvesting assemblies is governed by the local transition dipole and finite geometry of emitting units, a fact that point-dipole approximation obscures. To go beyond this picture, we develop a non-Hermitian Hamiltonian using the quantum electrodynamic dyadic Green's tensor for a purple bacteria. We construct it for the isolated 24-bacteriochlorophyll conical frustum and its P42$_1$2 crystallographic assembly. The P42$_1$2 unit-cell symmetry is found to invert the bright-dark ordering of the single ring, placing subradiant states at the low-energy end and revealing the entire crystal to be the energy-harvesting entity. Tilt-driven switching is activated only in crystal geometries where the finite dipole-carrier (LH2) lies perpendicular to the growth plane. Vacancy and orientational disorder work only in cooperation to renormalize the switching threshold from higher polar angles to lower values.

physics.bio-ph↗

arXiv2026

Thermodynamics of a biophotomimetic nonreciprocal quantum battery

We propose a theoretical model of a fully functional nonreciprocal quantum battery inspired by the architecture of bacterial light-harvesting complexes. We assign functional roles to collective quantum optical subradiant and superradiant states and introduce a unimodal cavity to assist storage. The transition rates are obtained from an effective non-Hermitian Hamiltonian, tailored to the battery geometry which are fed into a master equation to unravel the time evolution. We investigate the complete thermodynamic performance including storage, leakage, ergotropy, work extraction, flux, and power. We observe optimization at different ring sizes, each peaking at its specific energetic function. Strong coupling between the ring and central system enhances the battery's ability to store energy but reduces the ability of power output. The ergotropy exceeds capacity and approaches it linearly with increasing system size, with an optimal small-size regime that disappears under strong coupling.

quant-ph↗

arXiv2025

Coherence in the Leak and Storage Kurtosis control Ergotropy in Quantum Batteries

We introduce a cavity-coupled finite quantum system which can act as a quantum battery by harnessing noise induced coherences. We apply the methodology of full counting statistics to capture higher-order fluctuations of quanta exchange in the storage station. Together with the thermodynamic parameters, the fluctuations constitute a training platform for unsupervised as well as supervised learning models in predicting ergotropy. We identify a minimal predictive feature set from the battery's operating parameters that can classify the ergotropy into different regimes with great accuracy.Our results show that the usual quantum and thermodynamic variables are inadequate for the purpose of identifying high ergotropy regimes in isolation. Rather, it is the kurtosis of quanta exchange in the storage and the noise-induced coherence in the leakage mode that become the dominant quantities in controlling the magnitude of ergotropy.

quant-ph↗

arXiv2025

Ergotropy of a Photosynthetic Reaction Center

We theoretically analyze the Photosystem II reaction center using a quantum master equation approach, where excitonic and charge-transfer rates are computed at the Redfield and Förster levels with realistic spectral densities. The focus is on ergotropy, the maximum work extractable from a quantum state without energy loss. We compute the ergotropy by constructing passive states in the thermodynamic sense. Among the electron transfer pathways, those involving charge separation between $Chl_{D1}$ and $Phe_{D1}$, as well as a route passing through three sequential charge-separated states, yield higher ergotropy, suggesting greater capacity for work extraction, akin to quantum energy capacitors. A third pathway, bypassing the $Chl_{D1},Phe_{D1}$ pair, shows significantly reduced ergotropy. These differences arise from population-induced transitions between active and passive regimes. Our findings highlight how biological systems may exploit non-equilibrium population structures to optimize energy conversion, connecting quantum thermodynamic principles to biological energy harvesting.

physics.chem-ph↗

arXiv2025

Fischer Information of a Nonequilibrium Anharmonic Donor-Acceptor Rectifier

We investigate a nonequilibrium donor-acceptor quantum rectifier system coupled to an anharmonic vibrational mode, treating the vibrational dynamics both as a two-level system and as multilevel system. The time-dependent Fischer information is then calculated by deriving a quantum master equation for the reduced system dynamics. We estimate some key rectifier parameters, the donor energy, the acceptor energy, and the vibrational frequency. We report that there is an optimal time for estimating the donor and acceptor energy. However, the anharmonic mode can be estimated better only in the steadystate. The acceptor energy is found to be most precisely estimable, especially under strong coupling and high bias. Donor energy shows limited sensitivity, while vibrational frequency estimation benefits from low temperatures. This work offers a theoretical foundation for enhancing parameter estimation in nanoscale quantum devices, guiding future sensing and metrological applications in quantronic systems.

quant-ph↗

arXiv2025

Predicting Electromagnetically Induced Transparency based Cold Atomic Engines using Deep Learning

We develop an artificial neural network model to predict quantum heat engines working within the experimentally realized framework of electromagnetically induced transparency. We specifically focus on Λ-type alkali-based cold atomic systems. This network allows us to analyze all the alkali atom-based engines' performance. High performance engines are predicted and analyzed based on three figures of merit output, radiation temperature, work and ergotropy. Contrary to traditional notion, the algorithm reveal the limitations of output radiation temperature as a stand alone metric for enhanced engine performance. In high output temperature regime, Cs based engine with a higher output temperature than Rb based engine is characterized by lower work and ergotropy. This is found to be true for different atomic engines with common predicted states in both high and low output temperature regimes. Additionally, the ergotropy is found to exhibit a saturating exponential dependency on the control Rabi frequency.

quant-ph↗

arXiv2024

Cotunneling assisted nonequilibrium thermodynamics of a photosynthetic junction

We theoretically investigate a photosystem II-based reaction center modeled as a nonequilibrium quantum junction. We specifically focus on the electron-electron interactions that enable cotunneling events to be captured through quantum mechanical rates due to the inclusion of a negatively charged manybody state. Using a master equation framework with realistic spectral profiles, we analyze the cotunneling assisted current, power, and work. Amplification of the cotunneling assisted current and power occurs over a narrower bias range, reflecting a trade-off where higher flux is compensated by a reduced work window. We further report that the cotunneling-enhanced thermodynamic variables, particularly within specific bias windows, depends on the interplay between cotunneling amplitudes, electron transition rates, and interaction energy. Both attractive and repulsive electronic interactions can enhance cotunneling, but this effect is sensitive to the energy balance between states and the tunneling strength asymmetries.

cond-mat.mes-hall↗

arXiv2024

Efficiency fluctuations of a heat engine with noise induced quantum coherences

We analyze the efficiency fluctuations of a coherent quantum heat engine coupled to a unimodal cavity using a standard full-counting statistics procedure. The engine's most likely efficiency obtained by computing the large-deviation function corresponds to the quantum efficiency obtained by defining a useful work obtainable from a steady-state fluctuation theorem. The most likely efficiency is independent of the noise induced coherences. The ratio between coherent and incoherent efficiency cumulants is found to be constant and independent of the stochastic efficiency, which we prove analytically. We also numerically demonstrate that treating the efficiency as a stochastic variable allows the enhancement of constancy only in the presence of coherences. At the engine's most likely efficiency, there is no suppression of the second efficiency cumulant leading to a robust constancy. We also report the existence of a lower bound on the second efficiency cumulant.

quant-ph↗

arXiv2024

Noise induced coherent ergotropy of a quantum heat engine

We theoretically identify the noise-induced coherent contribution to the ergotropy of a four-level quantum heat engine coupled to a unimodal quantum cavity. We utilize a protocol where the passive state's quasiprobabilities can be analytically identified from the population-coherence coupled reduced density matrix. The reduced density matrix elements are evaluated using a microscopic quantum master equation formalism. Multiple ergotropies within the same coherence interval, each characterized by a positive and pronounced coherent contribution, are observed. These ergotropies are a result of population inversion as well as quasiprobability-population inversion, controllable through the coherence measure parameters. The optimal flux and power of the engine are found to be at moderate values of ergotropy with increasing values of noise-induced coherence. The optimal power at different coherences is found to possess a constant ergotropy.

quant-ph↗

arXiv2024

Cotunneling effects in the geometric statistics of a nonequilibrium spintronic junction

In the nonequilibrium steadystate of electronic transport across a spin-resolved quantronic junction, we investigate the role of cotunneling on the emergent statistics under phase-different adiabatic modulation of the reservoirs' chemical potentials. By explicitly identifying the sequential and inelastic cotunneling rates, we numerically evaluate the geometric or Pancharatnam-Berry contributions to the spin exchange flux. We identify the relevant conditions wherein the sequential and cotunneling processes compete and selectively influence the total geometric flux upshot. The Fock space coherences are found to suppress the cotunneling effects when the system reservoir couplings are comparable. The cotunneling contribution to the total geometric flux can be made comparable to the sequential contribution by creating a rightsided asymmetry in the system-reservoir coupling strength. Using a recently proposed geometric thermodynamic uncertainty relationship, we numerically estimate the total rate of minimal entropy production. The geometric flux and the minimum entropy are found to be nonlinear as a function of the interaction energy of the junction's spin orbitals.

cond-mat.mes-hall↗

arXiv2023

Geometricities of driven transport in presence of reservoir squeezing

In a bare site coupled to two reservoirs, we explore the statistics of boson exchange in the presence of two simultaneous processes: squeezing the two reservoirs and driving the two reservoirs. The squeezing parameters compete with the geometric phaselike effect or geometricity to alter the nature of the steadystate flux and noise. The even (odd) geometric cumulants and the total minimum entropy are found to be symmetric (antisymmetric) with respect to exchanging the left and right squeezing parameters. Upon increasing the strength of the squeezing parameters, loss of geometricity is observed. Under maximum squeezing, one can recover a standard steadystate fluctuation theorem even in the presence of phase different driving protocol. A recently proposed modified geometric thermodynamic uncertainty principle is found to be robust.

quant-ph↗

arXiv2023

Learning coherences from nonequilibrium fluctuations in a quantum heat engine

We develop an efficient machine learning protocol to predict the noise-induced coherence from the nonequilibrium fluctuations of photon exchange statistics in a quantum heat engine. The engine is a four-level quantum system coupled to a unimodal quantum cavity. The nonequilibrium fluctuations correspond to the work done during the photon exchange process between the four-level system and the cavity mode. We specifically evaluate the mean, variance, skewness, and kurtosis for a range of engine parameters using a full counting statistical approach combined with a quantum master equation technique. We use these numerically evaluated cumulants as input data to successfully predict the hot bath induced coherence. A supervised machine learning technique based on K-Nearest Neighbor(KNN) is found to work better than a variety of learning models that we tested.

quant-ph↗

arXiv2023

Work flux and efficiency at maximum power of a triply squeezed engine

We explore the effects of quantum mechanical squeezing on the nonequilibrium thermodynamics of a coherent heat engine with squeezed reservoirs coupled to a squeezed cavity. We observe that the standard known phenomenon of flux-optimization beyond the classical limit with respect to quantum coherence is destroyed in presence of squeezing. Under extreme nonequilibrium conditions, the flux is rendered independent of squeezing. The efficiency at maximum power (EMP) obtained by optimizing the cavity's squeezing parameter is greater than what was predicted by Curzon and Ahlborn even in the absence of reservoir squeezing. The EMP with respect to the either of reservoirs' squeezing parameters is surprisingly equal and linear in $η_C$ with a slope unequal to the universally accepted slope, 1/2. The slope is found to be proportional to the dissipation into the cavity mode and an intercept equal to a specific numerical value of the engine's efficiency.

quant-ph↗

arXiv2022

Nonequilibrium fluctuations in boson transport through squeezed reservoirs

We explore the effects of quantum mechanical squeezing on the nonequilibrium fluctuations of bosonic transport between two squeezed harmonic reservoirs and a two level system. A standard full counting statistics technique based on a quantum master equation is employed. We derive a nonzero thermodynamic affinity under equal temperature setting of the two squeezed reservoirs. The odd cumulants are shown to be independent of squeezing under symmetric conditions, whereas the even cumulants depend nonlinearly on the squeezing parameters. The odd and even cumulants saturate at two different but unique values which are identified analytically. Further, squeezing always increases the magnitude of the even cumulants in comparison to the unsqueezed case. We also recover a steady state fluctuation theorem with squeezing dependent thermodynamic affinity and demonstrate the robustness of a steadystate thermodynamic uncertainty relationship.

quant-ph↗

arXiv2022

Controlling thermodynamics of a quantum heat engine with modulated amplitude drivings

External driving of bath temperatures with a phase difference of a nonequilibrium quantum engine leads to the emergence of geometric effects on the thermodynamics. In this work, we modulate the amplitude of the external driving protocols by introducing envelope functions and study the role of geometric effects on the flux, noise and efficiency of a four-level driven quantum heat engine coupled with two thermal baths and a unimodal cavity. We observe that having a finite width of the modulation envelope introduces an additional control knob for studying the thermodynamics in the adiabatic limit. The optimization of the flux as well as the noise with respect to thermally induced quantum coherences becomes possible in presence of geometric effects, which is hitherto not possible with sinusoidal driving without an envelope. We also report the deviation of the slope and generation of an intercept in the standard expression for efficiency at maximum power as a function of Carnot efficiency in presence of geometric effects under the amplitude modulation. Further, a recently developed universal bound on the efficiency obtained from thermodynamic uncertainty relation is shown not to hold when a small width of the modulation envelope along with a large value of cavity temperature is maintained.

quant-ph↗