arXiv subjects

Anatoly A. Svidzinsky

Publications and source records attributed to Anatoly A. Svidzinsky.

At least 19 recordsLinked to original sources

arXiv2026

Quantum evolution of mixed states and performance of quantum heat engines

We introduce a technique for calculating the density operator time evolution along the lines of Heisenberg representation of quantum mechanics. Using this technique, we find the exact solution for the quantum evolution of two and three coupled harmonic oscillators initially prepared in thermal states at different temperatures. We show that such systems exhibit interesting quantum dynamics in which oscillators swap their thermal states due to correlation induced in the process of energy exchange and yield noise induced coherence. A photonic quantum heat engine (QHE) composed of two optical cavities can be modeled as coupled harmonic oscillators with time-dependent frequencies. Photons in the cavities become correlated during the engine operation. We show that the work done by such an engine is maximum if at the end of the cycle the oscillators swap numbers of excitations which can be achieved when the engine operates under the condition of parametric resonance. We also show that Carnot formula yields limiting efficiency for QHEs under general assumptions. Moreover, we show that, by making a canonical transformation, density operator of arbitrary n-mode Gaussian state can be written as a product of n thermal density operators describing independent collective excitations with different temperatures. Thus, operation of QHEs based on the correlated Gaussian states is equivalent to that based on uncorrelated thermal reservoirs. Our results deepen understanding of quantum evolution of mixed states which could be useful to design quantum machines with better performance.

quant-ph↗

arXiv2026

Dicke States for Accelerated Two Two-Level Atoms

We explore the formation of Dicke states. A system consisting of two two-level atoms located in the right Rindler wedge, has investigated to determine the conditions under which the superradiant or subradiant state can be formed. The dynamics of N two-level atoms forming symmetric state has also been analyzed and showed that the probability to excite any one atom of a collection of N atoms is related to the probability of exciting a single atom. We derive the analytical expression for the joint excitation probability which demonstrates the the interference effect. These findings provide new insights into the behavior of quantum systems in non-inertial frames and contribute to the broader understanding of relativistic quantum information theory.

quant-ph↗

arXiv2024

Minkowski vacuum entanglement and accelerated oscillator chains

Minkowski vacuum is empty from the perspective of Unruh-Minkowski photons, however, in the Rindler picture, it is filled with entangled pairs of Rindler photons. A ground-state atom uniformly accelerated through Minkowski vacuum can become excited by absorbing a Rindler photon (Unruh effect) or, in the alternative description, by emitting an Unruh-Minkowski photon (Unruh-Wald effect). We find an exact solution for the quantum evolution of a long chain of harmonic oscillators accelerated through Minkowski vacuum and for two chains accelerated in the opposite directions. We show how entanglement of Rindler photons present in Minkowski vacuum is transferred to the oscillators moving in causally disconnected regions. We also show that in the Unruh-Minkowski photon picture the process can be interpreted as if initial correlations between collective oscillator modes are transferred to the generated Unruh-Minkowski photons.

quant-ph↗

arXiv2023

Nonthermal radiation of evaporating black holes

Black hole (BH) evaporation is caused by creation of entangled particle-antiparticle pairs near the event horizon, with one carrying positive energy to infinity and the other carrying negative energy into the BH. Since under the event horizon, particles always move toward the BH center, they can only be absorbed but not emitted at the center. This breaks absorption-emission symmetry and, as a result, annihilation of the particle at the BH center is described by a non-Hermitian Hamiltonian. We show that due to entanglement between photons moving inside and outside the event horizon, nonunitary absorption of the negative energy photons near the BH center, alters the outgoing radiation. As a result, radiation of the evaporating BH is not thermal; it carries information about BH interior, and entropy is preserved during evaporation.

gr-qc↗

arXiv2022

New kind of condensation of Bose particles through stimulated processes

We show that stimulated scattering of an isolated system of N Bose particles with initially broad energy distribution can yield condensation of particles into excited collective state in which most of the bosons occupy one or several modes. During condensation, the total particle number and energy are conserved, while entropy of the system grows. Onset of condensation occurs at a critical particle occupation number when spectrum narrowing due to stimulated processes overcomes spectrum broadening due to diffusion. This differs from Bose-Einstein condensation in which particles undergo condensation into the equilibrium state due to thermalization processes.

cond-mat.quant-gas↗

arXiv2019

GW170817 event rules out general relativity in favor of vector gravity

The observation of gravitational waves by the three LIGO-Virgo interferometers allows the examination of the polarization of gravitational waves. Here we analyze the binary neutron star event GW170817, whose source location and distance are determined precisely by concurrent electromagnetic observations. Applying a signal accumulation procedure to the LIGO-Virgo strain data, we find ratios of the signals detected by the three interferometers. We conclude that the signal ratios are inconsistent with the predictions of general relativity, but consistent with the recently proposed vector theory of gravity [Phys. Scr. 92, 125001 (2017)]. Moreover, we find that vector gravity yields a distance to the source in agreement with the astronomical observations. If our analysis is correct, Einstein's general theory of relativity is ruled out in favor of vector gravity at 99% confidence level and future gravitational wave detections by three or more observatories should confirm this conclusion with higher precision.

physics.gen-ph↗

arXiv2019

Simplified equations for gravitational field in the vector theory of gravity and new insights into dark energy

Recently, a new alternative vector theory of gravity has been proposed which assumes that universe has fixed background Euclidean geometry and gravity is a vector field that alters this geometry [Phys. Scr. 92, 125001 (2017)]. It has been shown that vector gravity passes all available gravitational tests and yields, with no free parameters, the value of cosmological constant in agreement with observations. Here we obtain substantially simplified gravitational field equations of vector gravity which are more suitable for analytical and numerical analyses. We also provide a detailed explanation why in vector gravity in the reference frame of observer that takes a snapshot of the universe at time $t_0$ the ratio of the cosmological constant to the critical density is equal to 2/3 at $t=t_0$. We also show that dark energy does not affect universe evolution in the co-evolving reference frame. Thus, in reality, universe is expanding at a continually decelerating rate, with expansion asymptotically approaching zero.

physics.gen-ph↗

arXiv2017

Comment on "Probing gravitational wave polarizations with signals from compact binary coalescences"

In a recent paper "Probing gravitational wave polarizations with signals from compact binary coalescences" (arXiv:1710.03794 [gr-qc]) the authors argue that a single detection of gravitational wave by the LIGO-Virgo network is capable to distinguish between pure tensor and pure vector polarizations of gravitational waves. Here we point out a mistake in the author's analysis and show that such differentiation is possible only in the unlikely event when gravitational wave propagates in the direction of interferometer zero response for the tensor or vector polarizations. Nevertheless, the LIGO-Virgo network can distinguish between pure tensor and pure vector polarizations by collecting statistics, as we showed in Phys. Scr. 92, 125001 (2017).

gr-qc↗

arXiv2017

Vector theory of gravity: Universe without black holes and solution of dark energy problem

We propose an alternative theory of gravity which assumes that background geometry of the Universe is fixed four dimensional Euclidean space and gravity is a vector field $A_k$ in this space which breaks the Euclidean symmetry. Direction of $A_k$ gives the time coordinate, while perpendicular directions are spatial coordinates. Vector gravitational field is coupled to matter universally and minimally through the equivalent metric $f_{ik}$ which is a functional of $A_k$. We show that such assumptions yield a unique theory of gravity, it is free of black holes and, to the best of our knowledge, passes all available tests. For cosmology our theory predicts the same evolution of the Universe as general relativity with cosmological constant and zero spatial curvature. However, the present theory provides explanation of the dark energy as energy of longitudinal gravitational field induced by the Universe expansion and yields, with no free parameters, the value of $Ω_{Λ}=2/3\approx 0.67$ which agrees with the recent Planck result $Ω_{Λ}=0.686\pm 0.02$. Such striking agreement indicates that gravity has a vector, rather than tensor, origin. We demonstrate that gravitational wave signals measured by LIGO are compatible with vector gravity. They are produced by orbital inspiral of massive neutron stars which can exist in the present theory. We also quantize gravitational field and show that quantum vector gravity is equivalent to QED. Vector gravity can be tested by making more accurate measurement of the time delay of radar signal traveling near the Sun; by improving accuracy of the light deflection experiments; or by measuring propagation direction of gravitational waves relative to laser interferometer arms. Resolving the supermassive object at the center of our Galaxy with VLBA could provide another test of gravity and also shed light on the nature of dark matter.

gr-qc↗

arXiv2016

Symmetry protected single photon subradiance

We study the protection of subradiant states by the symmetry of the atomic distributions in the Dicke limit, in which collective Lamb shifts cannot be neglected. We find that anti-symmetric states are subradiant states for distributions with reflection symmetry. Continuous symmetry can also be used to achieve subradiance. This study is relevant to the problem of robust quantum memory with long storage time and fast readout.

physics.optics↗

arXiv2014

Sideband generation of transient lasing without population inversion

We suggest a method to generate coherent short pulses by generating a frequency comb using lasing without inversion in the transient regime. We use a universal method to study the propagation of a pulse in various spectral regions through an active medium that is strongly driven on a low-frequency transition on a time scale shorter than the decoherence time. The results show gain on the sidebands at different modes can be produced even if there is no initial population inversion prepared. Besides the production of ultra-short pulse this frequency comb may have applications towards making short-wavelength or Tera-hertz lasers.

physics.optics↗

arXiv2014

Parametric generation of high frequency coherent light in negative index materials and materials with strong anomalous dispersion

We demonstrate the possibility of generation of coherent radiation with tunable frequencies higher than the frequency of the driving field $ν_{d}$ in a nonlinear medium utilizing the difference combination resonance that occurs when $ν_{d}$ matches the difference of the frequencies of the two generated fields $ω_{1}$ and $ω_{2}$. We find that such a resonance can appear in materials which have opposite signs of refractive index at $ω_{1}$ and $ω_{2}$. It can also occur in positive refractive index materials with strong anomalous dispersion if at one of the generated frequencies the group and phase velocities are opposite to each other. We show that the light amplification mechanism is equivalent to a combination resonance in a system of two coupled parametric oscillators with the opposite sign of masses. Such a mechanism holds promise for a new kind of light source that emits coherent radiation of tunable wavelengths by an optical parametric amplification process with the frequency higher than $ν_{d}$.

physics.optics↗

arXiv2013

Superradiant control of gamma-ray propagation by vibrating nuclear arrays

The collective nature of light interactions with atomic and nuclear ensembles yields the fascinating phenomena of superradiance and radiation trapping. We study the interaction of gamma rays with a coherently vibrating periodic array of two-level nuclei. Such nuclear motion can be generated, e.g., in ionic crystals illuminated by a strong driving optical laser field. We find that deflection of the incident gamma beam into the Bragg angle can be switched on and off by nuclear vibrations on a superradiant time scale determined by the collective nuclear frequency, which is of the order of terahertz. Namely, if the incident gamma wave is detuned from the nuclear transition by much larger frequency it passes through the static nuclear array. However, if the nuclei vibrate with the frequency of the gamma ray detuning then parametric resonance can yield energy transfer into the Bragg deflected beam on the superradiant time scale, which can be used for fast control of gamma rays.

quant-ph↗

arXiv2012

Coherence Enhanced Transient Lasing in XUV Regime

We report the effect of a coherent drive on transient lasing in three-level $Λ$ and $Ξ$ configurations ($c\leftrightarrow a\leftrightarrow b$). We show that the presence of a resonant coherent drive on the $a\leftrightarrow c$ optical transition can yield an order of magnitude enhancement of the output laser energy on a $a\rightarrow b$ XUV or X-ray transition than with no coherent drive. We demonstrate the crucial role of coherence $\varrho_{ac}$ for the laser power enhancement. Contrary to the forward direction (with respect to the pump), where forward gain can be enhanced for some choice of the drive Rabi frequency $Ω_{c}$, coherent drive on the $ac$ transition always suppresses the backward gain.

physics.atom-ph↗

arXiv2009

Vector theory of gravity in Minkowski space-time: flat Universe without black holes

We propose a new classical theory of gravity which is based on the principle of equivalence and assumption that gravity, similarly to electrodynamics, is described by a vector field in Minkowski space-time. We show that such assumptions yield a unique theory of gravity; it passes all available tests and free of singularities such as black holes. In the present theory, gravity is described by four equations which have, e.g., exact analytical solution for arbitrary static field. For cosmology our equations give essentially the same evolution of the Universe as general relativity. Predictions of our theory can be tested within next few years making more accurate measurement of the time delay of radar signal traveling near the Sun or by resolving the supermassive object at the center of our Galaxy with VLBA. If general relativity is correct we must see a steady shadow from a black hole at the Galactic center. If the present theory is right then likely the shadow will appear and disappear periodically with a period of about 20 min as we predicted in JCAP 10 (2007) 018. Observation of such oscillations will also provide evidence for dark matter axion with mass in meV range.

gr-qc↗

arXiv2009

Evolution of collective N atom states in single photon superradiance

We present analytical solutions for the evolution of collective states of N atoms. On the one hand is a (timed) Dicke state prepared by absorption of a single photon and exhibiting superradiant decay. This is in strong contrast to evolution of a symmetric Dicke state which is trapped for large atomic clouds. We show that virtual processes yield a small effect on the evolution of the rapidly decaying timed Dicke state. However, they change the long time dynamics from exponential decay into a power-law behavior which can be observed experimentally. For trapped states virtual processes are much more important and provide new decay channels resulting in a slow decay of the otherwise trapped state.

physics.optics↗

arXiv2008

Dynamical evolution of correlated spontaneous emission of a single photon from a uniformly excited cloud of N atoms

We study the correlated spontaneous emission from a dense spherical cloud of N atoms uniformly excited by absorption of a single photon. We find that the decay of such a state depends on the relation between an effective Rabi frequency Omega, which is proportional to sqrt{N}, and the time of photon flight through the cloud R/c. If Omega*R/c < 1 the state exponentially decays with rate Omega^{2}*R/c and the state life time is greater then R/c. In the opposite limit Omega*R/c >> 1, the coupled atom-radiation system oscillates between the collective Dicke state (with no-photons) and the atomic ground state (with one photon) with frequency Omega while decaying at a rate c/R.

physics.optics↗

arXiv2007

Planck, Photon Statistics, and Bose-Einstein Condensation

The interplay between optical and statistical physics is a rich and exciting field of study. Black body radiation was the first application of photon statistics, although it was initially treated as a problem of the cavity oscillators in equilibrium with the photon field. However Planck surprisingly resisted the idea that anything physical would be quantized for a long time after he had solved the problem. We trace this development. Then, after the invention of the laser itself, it proved difficult to develop a theory of laser action that could account for photon statistics, i.e. fluctuations near threshold. This was accomplished in 1965. After Bose-Einstein condensation was successfully achieved, the same problem arose in this case. The fluctuation problem had not been treated adequately even for the ideal Bose gas. However this problem has now been solved using the same techniques as in the theory of laser action.

physics.optics↗