arXiv subjects

Gennady P. Berman

Publications and source records attributed to Gennady P. Berman.

At least 19 recordsLinked to original sources

arXiv2025

Decoherence as detector of the Unruh effect, II

The Unruh effect remains a central topic in quantum field theory, although its direct experimental verification continues to be challenging. Recent efforts have therefore focused on indirect detection strategies in which the Unruh effect emerges through measurable physical processes. In this work, we extend a previously introduced detector model, originally formulated for a massless scalar field, to the electromagnetic field. We show that the decoherence decay rates differ between inertial and accelerated frames. Furthermore, we demonstrate that the characteristic exponential decay associated with the Unruh effect can be observed at lower accelerations than those considered in earlier studies.

gr-qc↗

arXiv2025

Unruh effect and quantum entanglement for the non-uniform Rindler spacetime

While the Unruh effect has traditionally been studied under the assumption of uniform acceleration, a simplification motivated by experimental considerations, it is not necessarily true for all non-inertial motions. We propose a novel approach for the indirect detection of the Unruh effect without relying on the former restriction. Previous studies have shown that probing the decoherence of an Unruh-DeWitt detector can significantly reduce the acceleration required for observing the effect by several orders of magnitude compared to earlier proposals. Building on this idea, we develop a theoretical framework describing a non-inertial observer equipped with a detector undergoing non-uniform, time-dependent acceleration. We show that, in a non-uniformly accelerated Rindler spacetime, the particle distribution perceived in the Minkowski vacuum acquires a time-dependent modification of the standard Unruh spectrum. Furthermore, we demonstrate that the inclusion of quantum entanglement leads to a deformation of the Minkowski vacuum into squeezed states.

gr-qc↗

arXiv2021

Magnetic Resonance Force Microscopy with Overlapping Frequencies of Cantilever and Spin

We have studied theoretically magnetic resonance force microscopy (MRFM) with a high frequency nanomechanical cantilever when the cantilever frequency matches the resonant frequency of a single electron spin. Our estimations show that in this scenario the relative frequency shift of the cantilever can be much greater than the record MRFM frequency shift achieved in experiments with a single spin detection. Experimental realization of our proposal could open the way for fast detection of a single electron spin and even for detection of a single nuclear spin.

cond-mat.mes-hall↗

arXiv2020

Multiscale cyclic dynamics in light harvesting complex in presence of vibrations and noise

Starting from the many-body Schrödinger equation, we derive a new type of Lindblad Master equations describing a cyclic exciton/electron dynamics in the light harvesting complex and the reaction center. These equations resemble the Master equations for the electric current in mesoscopic systems, and they go beyond the single-exciton description by accounting for the multi-exciton states accumulated in the antenna, as well as the charge-separation, fluorescence and photo-absorption. Although these effects take place on very different timescales, their inclusion is necessary for a consistent description of the exciton dynamics. Our approach reproduces both coherent and incoherent dynamics of exciton motion along the antenna in the presence of vibrational modes and noise. We applied our results to evaluate energy (exciton) and fluorescent currents as a function of sunlight intensity.

physics.chem-ph↗

arXiv2020

Two-Component Axionic Dark Matter Halos

We consider a two-component dark matter halo (DMH) of a galaxy containing ultra-light axions (ULA) of different mass. The DMH is described as a Bose-Einstein condensate (BEC) in its ground state. In the mean-field (MF) limit we have derived the integro-differential equations for the spherically symmetrical wave functions of the two DMH components. We studied numerically the radial distribution of the mass density of ULA and constructed the parameters which could be used to distinguish between the two- and one-component DMH. We also discuss an interesting connection between the BEC MF ground state of a one-component DMH and Hawking temperature and entropy of a corresponding Black Hole, and Unruh temperature.

hep-ph↗

arXiv2019

Quantum Electron Transport in Degenerate Donor-Acceptor Systems

We develop a mathematically rigorous theory for the quantum transfer processes in degenerate donor-acceptor dimers in contact with a thermal environment. We calculate explicitly the transfer rates and the acceptor population efficiency. The latter depends critically on the initial donor state. We show that quantum coherence in the initial state enhances the transfer process. If the electron is initially shared coherently by the donor levels then the efficiency can reach values close to 100%, while an incoherent initial donor state will significantly suppress the efficiency. The results are useful for a better understanding of the quantum electron transport in many chemical, solid state, and biological systems with complex degenerate and quasi-degenerate energy landscapes.

quant-ph↗

arXiv2018

Noise-Assisted Quantum Exciton and Electron Transfer in Bio-Complexes with Finite Donor and Acceptor Bandwidths

We present an analytic and numerical study of noise-assisted quantum exciton (electron) transfer (ET) in a bio-complex, consisting of an electron donor and acceptor (a dimer), modeled by interacting continuous electron bands of finite widths. The interaction with the protein-solvent environment is modeled by a stationary stochastic process (noise) acting on all the donor and acceptor energy levels. We start with discrete energy levels for both bands. Then, by using a continuous {limit} for the electron spectra, we derive integro-differential equations for ET dynamics between two bands. Finally, we derive from these equations rate-type differential equations for ET dynamics. We formulate the conditions of validity of the rate-type equations. We consider different regions of parameters characterizing the widths of the donor and acceptor bands and the strength of the dimer-noise interaction. For a simplified model with a single energy level donor and a continuous acceptor band, we derive a generalized analytic expression and provide numerical simulations for the ET rate. They are consistent with Wigner-Weisskopf, Förster-type, and Marcus-type expressions, in their corresponding regime of parameters.Our analytic results are confirmed by numerical simulations. We demonstrate how our theoretical results are modified {when both the donor and the acceptor are described by finite bands}. We also show that, for a relatively wide acceptor band, the efficiency of the ET from donor to acceptor can be close to 100% for a broad range of noise amplitudes, for both "downhill" and "uphill" ET, for sharp and flat redox potentials, and for reasonably short times. We discuss possible experimental implementations of our approach with application to bio-complexes.

physics.bio-ph↗

arXiv2017

Multi-Scale Exciton and Electron Transfer in Multi-Level Donor-Acceptor System

We study theoretically the noise-assisted quantum exciton (electron) transfer (ET) in bio-complexes consisting of a single-level electron donor and an acceptor which has a complicated internal structure, and is modeled by many electron energy levels. Interactions are included between the donor and the acceptor energy levels and with the protein-solvent noisy environment. Different regions of parameters are considered, which characterize (i) the number of the acceptor levels, (ii) the acceptor \band-width", and (iii) the amplitude of noise and its correlation time. Under some conditions, we derive analytical expressions for the ET rate and efficiency. We obtain equal occupation of all levels at large times, independently of the structure of the acceptor band and the noise parameters, but under the condition of non-degeneracy of the acceptor energy levels. We discuss the multi-scale dynamics of the acceptor population, and the accompanying effect of quantum coherent oscillations. We also demonstrate that for large number of levels in the acceptor band, the efficiency of ET can be close to 100%, for both downhill and uphill transitions and for sharp and at redox potentials.

physics.bio-ph↗

arXiv2017

Multiscale Multiexciton Cyclic Dynamics in Light Harvesting Complex

Usually the study of energy-transfer in the light harvesting complex is limited by a single-exciton motion along the antenna. Starting from the many-body Schrödinger equation, we derived Lindblad-type Master equations describing the cyclic exciton-electron dynamics of the light harvesting complex, originated from charge reduction of a donor. These equations, resembling the Master equations for the electric current in mesoscopic systems, go beyond the single-exciton description by accounting for the multi-exciton states accumulated in the antenna, as well as the charge-separation, fluorescence and initial photo-absorption. Although these effects take place on very different time-scales, we demonstrate that their inclusion is necessary for a consistent description of the exciton dynamics. We applied our results to evaluate the energy (exciton) current and for the fluorescent current depending on the light-intensity.

physics.chem-ph↗

arXiv2015

Superradiance Transition in Graphene

We study theoretically and numerically the conditions required for the appearance of a superradiance transition in graphene. The electron properties of graphene are described in the single $p_z$-orbital tight-binding approximation, in which the model is reduced to the effective two-level pseudo-spin $1/2$ system. For each level we introduce the electron transfer rate of escape into a continuum. We demonstrate that, under some conditions, the superradiance experiences the maximal quantum coherent escape to the continuum.

quant-ph↗

arXiv2015

Non-Hermitian Quantum Annealing and Superradiance

We consider the non-Hermitian quantum annealing for the one-dimentional Ising spin chain, and for a large number of qubits. We show that the annealing time is significanly reduced for the non-Hermitian algorithm in comparison with the Hermitian one. We also demonstrtate the relation of the non-Hermitian quantum annealing with the superadiance transition in this system.

quant-ph↗

arXiv2015

On Improving the Performance of Nonphotochemical Quenching in CP29 Light-Harvesting Antenna Complex

We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment interaction, and (iii) the energy transfer rates to the sinks, one can significantly improve the performance of the NPQ. Our analysis suggests strategies for improving the performance of the NPQ in response to environmental changes, and may stimulate experimental verification.

physics.bio-ph↗

arXiv2015

Superradiance Transition and Nonphotochemical Quenching in Photosynthetic Complexes

We demonstrate numerically that superradiance could play a significant role in nonphotochemical quenching (NPQ) in light-harvesting complexes. Our model consists of a network of five interconnected sites (discrete excitonic states) that are responsible for the NPQ mechanism. Damaging and charge transfer states are linked to their sinks (independent continuum electron spectra), in which the chemical reactions occur. The superradiance transition in the charge transfer (or in the damaging) channel, occurs at particular electron transfer rates from the discrete to the continuum electron spectra, and can be characterized by a segregation of the imaginary parts of the eigenvalues of the effective non-Hermitian Hamiltonian. All five excitonic sites interact with their protein environment that is modeled by a random stochastic process. We find the region of parameters in which the superradiance transition into the charge transfer channel takes place. We demonstrate that this superradiance transition has the capability of producing optimal NPQ performance.

physics.bio-ph↗

arXiv2015

The Radical Pair Mechanism and the Avian Chemical Compass: Quantum Coherence and Entanglement

We review the spin radical pair mechanism which is a promising explanation of avian navigation. This mechanism is based on the dependence of product yields on (1) the hyperfine interaction involving electron spins and neighboring nuclear spins and (2) the intensity and orientation of the geomagnetic field. One surprising result is that even at ambient conditions quantum entanglement of electron spins can play an important role in avian magnetoreception. This review describes the general scheme of chemical reactions involving radical pairs generated from singlet and triplet precursors; the spin dynamics of the radical pairs; and the magnetic field dependence of product yields caused by the radical pair mechanism. The main part of the review includes a description of the chemical compass in birds. We review: the general properties of the avian compass; the basic scheme of the radical pair mechanism; the reaction kinetics in cryptochrome; quantum coherence and entanglement in the avian compass; and the effects of noise. We believe that the "quantum avian compass" can play an important role in avian navigation and can also provide the foundation for a new generation of sensitive and selective magnetic-sensing nano-devices.

physics.bio-ph↗

arXiv2015

Decoherence and Spin Echo in Biological Systems

The spin echo approach is extended to include bio-complexes for which the interaction with dynamical noise is strong. Significant restoration of the free induction decay signal due to homogeneous (decoherence) and inhomogeneous (dephasing) broadening is demonstrated analytically and numerically, for both an individual dimer of interacting chlorophylls and for an ensemble of dimers. This approach is based on an exact and closed system of ordinary differential equations that can be easily solved for a wide range of parameters that are relevant for bio-applications.

physics.bio-ph↗

arXiv2014

Possible Role of Interference and Sink Effects in Nonphotochemical Quenching in Photosynthetic Complexes

We describe a simple and consistent quantum mathematical model that simulates the possible role of quantum interference and sink effects in the nonphotochemical quenching (NPQ) in light-harvesting complexes (LHCs). Our model consists of a network of five interconnected sites (excitonic states) responsible for the NPQ mechanism: (i) Two excited states of chlorophyll molecules, $ChlA^*$ and $ChlB^*$, forming an LHC dimer, which is initially populated; (ii) A "damaging" site which is responsible for production of singlet oxygen and other destructive outcomes; (iii) The $(ChlA-Zea)^*$ heterodimer excited state (Zea indicates zeaxanthin); and (iv) The charge transfer state of this heterodimer, $(ChlA^{-}-Zea^{+})^*$. In our model, both damaging and charge transfer states are described by discrete electron energy levels attached to their sinks, that mimic the continuum part of electron energy spectrum, as at these sites the electron participates in quasi-irreversible chemical reactions. All five excitonic sites interact with the protein environment that is modeled using a stochastic approach. As an example, we apply our model to demonstrate possible contributions of quantum interference and sink effects in the NPQ mechanism in the CP29 minor LHC. Our numerical results on the quantum dynamics of the reduced density matrix, demonstrate a possible way to significantly suppress, under some conditions, the damaging channel using quantum interference effects and sinks. The results demonstrate the possible role of interference and sink effects for modeling, engineering, and optimizing the performance of the NPQ processes in both natural and artificial light-harvesting complexes.

physics.bio-ph↗

arXiv2014

The Role of Protein Fluctuation Correlations in Electron Transfer in Photosynthetic Complexes

We consider the dependence of the electron transfer in photosynthetic complexes on correlation properties of random fluctuations of the protein environment. The electron subsystem is modeled by a finite network of connected electron (exciton) sites. The fluctuations of the protein environment are modeled by random telegraph processes, which act either collectively (correlated) or independently (uncorrelated) on the electron sites. We derived an exact closed system of first-order linear differential equations with constant coefficients, for the average density matrix elements and for their first moments. Under some conditions, we obtain analytic expressions for the electron transfer rates. We compare the correlated and uncorrelated regimes, and demonstrated numerically that the uncorrelated fluctuations of the protein environment can, under some conditions, either increase or decrease the electron transfer rates.

physics.bio-ph↗

arXiv2014

Sensitivity and Entanglement in the Avian Chemical Compass

The Radical Pair Mechanism can help to explain avian orientation and navigation. Some evidence indicates that the intensity of external magnetic fields plays an important role in avian navigation. In this paper, based on a two-stage strategy, we demonstrate that birds could reasonably detect the directions of geomagnetic fields and gradients of these fields using a yield-based chemical compass that is sensitive enough for navigation. Also, we find that the lifetime of entanglement in this proposed compass is angle-dependent and long enough to allow adequate electron transfer between molecules.

physics.bio-ph↗