Searcharxiv⌕ Search

arXiv subjects

Moorad Alexanian

Publications and source records attributed to Moorad Alexanian.

36 records · Page 2Linked to original sources
arXiv2021

Characteristic function and quasi-probability distribution of photons and of squeezed coherent photons

We consider the p-ordered characteristic function and its Fourier transform, the quasidistribution function, of squeezed coherent photons in a thermal state of photons and calculate the mean number and number variance of squeezed coherent photons. All the properties calculated from the previous characteristic function can be used to calculate said properties for photons in a thermal state of squeezed coherent photons via a parametric transformation. In particular, one can obtain the mean number and number variance via the parametric transformation.

quant-ph↗
arXiv2020

Mean Number and Number Variance of Squeezed Coherent Photons In a Thermal State of Photons

We consider the equilibrium thermal state of photons and determine the mean number and number variance of squeezed coherent photons. We use an integral representation for electro-magnetic radiation applicable both to systems in equilibrium and to systems in nonequilibrium to determine the spectral function of the radiation. The system considered is in thermal equilibrium and we find that the squeezed coherent photons are at a higher temperature than the photons themselves. Also, as expected, the mean number of squeezed coherent photons is greater than that of photons.

quant-ph↗
arXiv2020

Quantum Rabi oscillations in coherent and squeezed coherent states via one- and two-photon transitions

We determine the Rabi oscillations for coherent and squeezed coherent states via one- and two-photon atomic transitions in two- and three-level atoms, respectively. The effect of squeezing coherent states is to reduce the large number of photons of mesoscopic scale to fewer photons and so be able to use numerical solutions with the aid of the Jaynes-Cummings model. We maximize the squeezing of the coherent state by minimizing the ratio of the photon number variance to photon number, thus narrowing the region where revival occurs.

quant-ph↗
arXiv2019

The Bogoliubov inequality and the nature of Bose-Einstein condensates for interacting atoms in spatial dimensions $D \le 2$

We consider the restriction placed by the Bogoliubov inequality on the nature of the Bose-Einstein condensates (BECs) for interacting atoms in a spatial dimension D </- 2 and in the presence of an external arbitrary potential, which may be a confining "box", a periodic, or a disordered potential. The atom-atom interaction gives rise to a (gauge invariance) symmetry-breaking term that places further restrictions on BECs in the form of a consistency proviso. The necessary condition for the existence of a BEC in D </- 2 in all cases is macroscopic occupation of many single-particle momenta states with the origin a limit point (or accumulation point) of condensates. It is shown that the nature of BECs for noninteracting atoms in a disordered potential is precisely the same as that of BECs for interacting atoms in the absence of an external potential.

cond-mat.quant-gas↗
arXiv2019

Statistical Entropy of a Schwarzschild-anti-de Sitter Black Hole

We calculate the intrinsic entropy of a Schwarzschild black hole in an asymptotically antide Sitter space. The statistical calculation of the entropy is based on a model for particle structure that leads to confinement. The constituents of the particle are distinguishable quasiparticles. The entropy (temperature) is less (greater) than the entropy of a Schwarzschild black hole in an asymptotically flat space. The equilibrium thermodynamic states are described by pure states, myriotic fields, and the distinguishability of the internal microstates may provide a solution to the black hole information paradox by suggesting a Bose-Einstein condensate whereby the zero mass state is a limit point (or accumulation point) of condensates on the event horizon.

gr-qc↗
arXiv2019

Integral representation of the cosmic microwave background spectrum

We use an integral representation for nonthermal radiation, which is bounded from below and above, to describe the spectrum of the cosmic microwave background (CMB). The upper bound is given by the Rayleigh-Jeans law with a temperature $T_{RJ}$ that can be determined by the absorption signal of 21 cm photons, where $T_{RJ}$ represents the equilibrium temperature of photons in the RJ tail. If $T_{RJ}>T_{CMB}$, then the lower bound allows us to conclude that photons, additional to the remnant of the Big Bang, are needed to explain the present CMB. These constraints are additional to other cosmological or astrophysical constraints in the study of the distortions of the CMB brought about by new physics particles or fields.

astro-ph.CO↗
arXiv2018

Anti-Diffusion in Continuous Opinion Dynamics

Considerable effort using techniques developed in statistical physics has been aimed at numerical simulations of agent-based opinion models and analysis of their results. Such work has elucidated how various rules for interacting agents can give rise to steady state behaviors in the agent populations that vary between consensus and fragmentation. At the macroscopic population level, analysis has been limited due to the lack of an analytically tractable governing macro-equation for the continuous population state. We use the integro-differential equation that governs opinion dynamics for the continuous probability distribution function of agent opinions to develop a novel nonlinear partial differential equation for the evolution of opinion distributions. The highly nonlinear equation allows for the generation of a system of approximations. We consider three initial population distributions and determine their small-time behavior. Our analysis reveals how the generation of clusters results from the interplay of diffusion and anti-diffusion and how initial instabilities arise in different regions of the population distribution.

physics.soc-ph↗
arXiv2018

Quantum entropy and polarization measurements of the two-photon system

We consider the bipartite state of a two-photon polarization system and obtain the exact analytical expression for the von Neumann entropy in the particular case of a 5-parameter polarization density matrix. We investigate and graphically illustrate the dependence of the entropy on these five parameters, in particular, the existence of exotic, transition from exotic to non-exotic, and non-exotic states, where the quantum conditional entropy is negative, both positive and negative, and positive, respectively. We study the "cooling" or "heating" effect that follows from the reduced density of photon 2 when a measurement is performed on photon 1.

quant-ph↗
arXiv2017

Dynamically generated quadrature and photon-number variances for Gaussian states

We calculate exactly the quantum mechanical, temporal Wigner quasiprobability density for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz., a displaced-squeezed thermal state. The Wigner function allows us to calculate the fluctuations in photon number and the quadrature variance. We contrast the difference between the nonclassicality criteria, which is independent of the displacement parameter $α$, based on the Glauber-Sudarshan quasiprobability distribution $P(β)$ and the classical/nonclassical behavior of the Mandel $Q_{M}(τ)$ parameter, which depends strongly on $α$. We find a phase transition as a function of $α$ such that at the critical point $α_{c}$, $Q_{M}(τ)$, as a function of $τ$, goes from strictly classical, for $|α|< |α_{c}|$, to a mixed classical/nonclassical behavior, for $|α|> |α_{c}|$.

quant-ph↗
arXiv2016

Field-quadrature and photon-number variances for Gaussian states

We calculate exactly the quantum mechanical, temporal characteristic function $χ(η)$ for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz., a displaced-squeezed thermal state. Knowledge of $χ(η)$ allows only the determination of the time development of arbitrary functions of equal-time products of creation and annihilation photon operators. We calculate, in particular, the fluctuations in photon number, quadrature operators, and quadrature variance. We contrast the very important difference between the nonclassicality criteria based on the one-time characteristic function $χ(η)$ versus nonclassicality criteria based on the two-time, second-order coherence function $g^{(2)}(τ)$ and show numerically that the nonclassicality criteria based on $χ(η)$ does not determine the classical/nonclassical behavior of $g^{(2)}(τ)$.

quant-ph↗
arXiv2016

Nonclassicality criteria: Quasiprobability distributions and correlation functions

We use the exact calculation of the quantum mechanical, temporal characteristic function $χ(η)$ and the degree of second-order coherence $g^{(2)}(τ)$ for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz., a displaced-squeezed thermal state, to study the different criteria for nonclassicality. In particular, we contrast criteria that involve only one-time functions of the dynamical system, for instance, the quasiprobability distribution $P(β)$ of the Glauber-Sudarshan coherent or P-representation of the density of state and the Mandel $Q_{M}(τ)$ parameter, versus the criteria associated with the two-time correlation function $g^{(2)}(τ)$.

quant-ph↗
arXiv2015

Temporal second-order coherence function for displaced-squeezed thermal states

We calculate the quantum mechanical, temporal second-order coherence function for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz., a displaced-squeezed thermal state. The calculation involves first the dynamical generation at time $t$ of the Gaussian state from an initial thermal state and subsequent measurements of two photons a time $τ\geq 0$ apart. The generation of the Gaussian state by the parametric amplifier ensures that the temporal second-order coherence function depends only on $τ$, via $τ/t$, for given Gaussian state parameters, Gaussian state preparation time $t$, and average number $\bar{n}$ of thermal photons. It is interesting that the time evolution for displaced thermal states shows a power decay in $τ/t$ rather than an exponential one as is the case for general, displaced-squeezed thermal states.

quant-ph↗
arXiv2015

Nature, Science, Bayes' Theorem, and the Whole of Reality

A fundamental problem in science is how to make logical inferences from scientific data. Mere data does not suffice since additional information is necessary to select a domain of models or hypotheses and thus determine the likelihood of each model or hypothesis. Thomas Bayes' Theorem relates the data and prior information to posterior probabilities associated with differing models or hypotheses and thus is useful in identifying the roles played by the known data and the assumed prior information when making inferences. Scientists, philosophers, and theologians accumulate knowledge when analyzing different aspects of reality and search for particular hypotheses or models to fit their respective subject matters. Of course, a main goal is then to integrate all kinds of knowledge into an all-encompassing worldview that would describe the whole of reality.

physics.hist-ph↗
arXiv2015

The Order and Integration of Knowledge

William Oliver Martin published "The Order and Integration of Knowledge" in 1957 to address the problem of the nature and the order of various kinds of knowledge; in particular, the theoretical problem of how one kind of knowledge is related to another kind. Martin characterizes kinds of knowledge as being either autonomous or synthetic. The latter are reducible to two or more of the autonomous (or irreducible) kinds of knowledge, viz., history (H), metaphysics (Meta), theology (T), formal logic (FL), mathematics (Math), and generalizations of experimental science (G). Metaphysics and theology constitute the two domains of the ontological context while history and experimental science are the two domains of the phenomenological context. The relation of one kind of knowledge to another may be instrumental, constitutive, and/or regulative. For instance, historical propositions are constitutive of G, metaphysical propositions are regulative of G, and propositions in formal logic and mathematics are instrumental to G. Theological propositions are not related to G and so there is no conflict between science and theology. Martin's work sheds light on the possible areas of incompatibility between science and religion.

physics.hist-ph↗
arXiv2015

Exact temporal second-order coherence function for displaced-squeezed thermal states

We calculate exactly the quantum mechanical, temporal second-order coherence function for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz., a displaced-squeezed thermal state. The calculation involves first the generation of the Gaussian state and subsequent measurements of two photons a time $τ\geq 0$ apart. The generation of the Gaussian state by the parametric amplifier insures that the temporal second-order coherence function depends only on $τ$.

quant-ph↗
arXiv2012

Generation of entangled tripartite states in three identical cavities

The generation of entanglement between three identical coupled cavities, each containing a single three-level atom, is studied when the cavities exchange two coherent photons and are in the N=2, 4, and 6 manifolds, where $N$ represents the maximum number of photons possible in any one cavity. The combined states of the atom and the photon in a cavity is given by a qutrit for N=2, a five-dimensional qudit for N=4, and a seven-dimensional qudit for N=6. The conservation of the operator $\hat{N}$ for the interacting three-cavity system limits the total number of tripartite states to only 6, 18, and 38, rather than the usual $3^3=27$, $5^3=125$, and $7^3 =343$ states for N=2, 4, and 6, respectively. The deterministic generation of entanglement from general initially unentangled tripartite states is studied in the limit of large hopping strength, where all the solutions are analytic and given in terms of exponential functions. Several types of resulting tripartite entanglement are analyzed in order to obtain maximally entangled states.

quant-ph↗
arXiv2004

Cavity broadcasting via Raman scattering

The notion of broadcasting is extended to include the case where an arbitrary input density state of a two-mode radiation field gives rise to an output state with identical marginal states for the respective modes, albeit different from the input state. The initial unknown input density state is unitarily related to the output state but is not equal to the two identical output marginal states. This extended notion of broadcasting suggests a possible way of discriminating between two noncommuting quantum states.

quant-ph↗