arXiv subjects

Malek Bagheri Harouni

Publications and source records attributed to Malek Bagheri Harouni.

10 recordsLinked to original sources

arXiv2025

Phase Diffusion of Light Immersed In Quantum Tides: Open Quantum System Approach

The interaction between quantum gravitational waves (GWs) and electromagnetic (EM) fields is investigated within the open quantum system formalism, where GWs are considered as a heat bath reservoir occupying a generic state $\hatρ_{\text{gws}}$. Following the quantum Langevin equations, it turns out that the correlations of the Langevin noise operator associated with the GW background directly determine the statistical properties of the EM phasor $ϕ(t)$. We apply this formalism to the background of inflationary-generated primordial gravitational waves (PGW). Since this background has an astronomically large correlation time, of the order of the Hubble time $H_0^{-1}$, we show that it leads to a non-Markovian dynamics of the EM field, which causes memory effects. As a result of the Gaussianity of PGW, it turns out that the EM phasor goes through a stochastic process, which is a manifestation of the fluctuation-dissipation in EM-GW system. The variance of the EM phase smears out as $Δ^2φ(t)= Δ^2φ_0+ 4(t/τ_c)^4$, where the characteristic time scale $τ_c$ is associated with the diffusion rate caused by PGWs. The specific quartic growth of the phase noise is thus attributed to the two-mode squeezed nature of PGWs, which is inherently different from the phase diffusion induced by vacuum fluctuations of spacetime or a thermal heat bath of gravitons.

gr-qc↗

arXiv2025

Revisiting van Citter-Zernike correlations in the presence of primordial gravitational waves

In this paper, we develop a quantum field theory framework to describe the interaction between a gravitational wave (GW) background and an electromagnetic (EM) field emitted from a distant celestial source, such as a star. We demonstrate that a background of primordial gravitational waves (PGWs), as predicted by the inflationary scenario, induces a loss of spatial coherence in the EM field as it propagates over cosmological distances. This effect leads to the degradation of van Cittert-Zernike correlations, ultimately rendering them unobservable - a phenomenon referred to as blurring. Since spatial coherence is observed in very long baseline interferometry (VLBI) measurements of distant quasars, this places constraints on the amplitude of the PGW background. We quantitatively evaluate the blurring effect caused by PGWs in a two-mode squeezed state, which represents the standard quantum state predicted by the simplest inflationary models. However, due to the weak coupling between GWs and the EM field, we find that the induced incoherence is too small to be detected in current VLBI observations.

gr-qc↗

arXiv2022

Influence of spherical anisotropy on optical mass sensing in a molecular-plasmonic optomechanical system

We use an all-optical pump-probe method to develop a mass sensing mechanism in a molecular plasmonic system at room temperature. The system consists of a double-clamped graphene nanoribbon that parametrically interacts with two types of isotropic and anisotropic spherical plasmonic cavities in the presence of a strong pump field and a weak probe pulse. Based on the mode-selective quantization scheme and analogy with the canonical model of the cavity optomechanics, we formulate the Hamiltonian of the system in terms of the electromagnetic Greens tensor. In this manner, we derive an explicit form of size-dependent optomechanical coupling function and plasmonic damping rate, which include the modal, geometrical, and material features of the plasmonic structure. Engineering material features of the plasmonic nanostructure, we find that the intensity of the probe field transmission spectrum for radially anisotropic spherical nanocavity enhances significantly compared to the silver sphere nanocavity due to the mode volume reduction. This scheme can provide to achieve the minimum measurable mass at room temperature.

quant-ph↗

arXiv2021

Generation of entanglement between quantum dot molecule with the presence of phonon effects in a voltage-controlled junction

We investigate the generation of entanglement through a quantum dot molecule under the influence of vibrational phonon modes in a bias voltage junction. The molecular quantum dot system is realized by coupled quantum dots inside a suspended carbon nanotube. We consider the dynamical entanglement as a function of bias voltage and temperature by taking into account the electron-phonon interaction. In order to generate the robust entanglement between quantum dots and preserve it to reach the maximal achievable amount steadily, we introduce an asymmetric coupling protocol and apply the easy tunable bias voltage-driven field. For an oscillating bias voltage, the time-varying entanglement can periodically reach the maximum revival. In thermal entanglement dynamics, the phenomena of thermal entanglement degradation and thermal entanglement revival are observed which are intensively affected by the strength of phonon decoherence. The revival of entanglement shows a larger value for a higher phonon coupling.

cond-mat.mes-hall↗

arXiv2021

Single-quadrature quantum magnetometry in cavity electromagnonics

A scheme of an ultra-sensitive magnetometer in the cavity quantum electromagnonics where the intracavity microwave mode coupled to a magnonic mode via magnetic dipole interaction is proposed. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only the added noise can be suppressed, but also the output cavity response to the input signal can be substantially amplified in order to achieve a precise magnetic-field measurement. The estimated theoretical sensitivity of the proposed magnetic amplifier-sensor is approximately in the order of $10^{-18}T/\sqrt{Hz}$ which is competitive compared to the current state-of-the-art magnetometers like superconducting quantum interference devices (SQUIDs) and atomic magnetometers. The advantage of the proposed sensor in comparison with the other magnetometers is its high sensitivity at room temperature and sensing in a wide range of frequency up to MHz as well as its capability to signal-response amplification.

quant-ph↗

arXiv2020

Polaronic Entanglement of Quantum dot Molecule in a voltage-controlled junction

We investigate the influence of vibrational phonon modes on the entanglement through a quantum dot molecule under the bias voltage-driven field. The molecular quantum dot system can be realized by coupled quantum dots in the middle of the suspended carbon nanotube. This system would be described by the Anderson-Holstein model and also can be analyzed by the polaron master equation in Markovian regime. In the presence of electron-phonon interaction, we study the entanglement as a function of bias voltage and temperature. Despite entanglement degradation because of phonon decoherence, we employ an asymmetric coupling protocol to preserve the entanglement in a significant level and also we apply the easy tunable bias voltage driven to engineer its behavior. In dynamics of entanglement, we demonstrate the phenomenon of thermal entanglement degradation and rebirth through the increase of temperature. In this process, thermal entanglement revival is intensively affected by the strength of phonon decoherence. Such that, stronger revival is occurred for higher phonon coupling amount. With an applied time-dependent bias voltage, the entanglement evolution shows periodic revival by time and in response to bias voltage rising, it illustrates decreasing and grows steadily to reach the flat form with considerable magnitude.

quant-ph↗

arXiv2019

Robust entanglement of an asymmetric quantum dot molecular system in a Josephson junction

We demonstrate how robust entanglement of quantum dot molecular system in a voltage controlled junction can be generated. To improve the quantum information characteristics of this system, we propose an applicable protocol which contains the implementation of asymmetric quantum dots as well as engineering reservoirs. Quantum dots with tunable energy barriers can provide asymmetric coupling coefficients which can be tuned by gap voltages. Also by engineering reservoirs, superconductors can be used as leads in a biased-voltage junction. The high-controllability characteristics of system supplies the arbitrary entanglement by tuning the controlling parameters. Significantly in concurrence-voltage characteristics, perfect entanglement can be achieved in an asymmetric structure and it can be kept with near-unit magnitude in response to bias voltage increasing.

quant-ph↗

arXiv2018

Entanglement between distant atoms mediated by a hybrid quantum system consisting of superconducting flux qubit and resonators

A hybrid quantum system consisting of spatially separated two-level atoms is studied. Two atoms do not interact directly, but they are coupled via an intermediate system which is consisting of a superconducting flux qubit interacting with a mechanical and an electrical resonator which are coupled to one of the atoms. Moreover, the superconducting flux qubit is driven by a classical microwave field. Applying the adiabatic elimination an effective Hamiltonian for the atomic subsystem is obtained. Our results demonstrate that the entanglement degradation decay as well as the fidelity decay in the dispersive regime are faster. Moreover, the driven field amplitude possesses an important role in the entanglement and fidelity evolution.

quant-ph↗

arXiv2018

Photon antibunching control in a quantum dot and metallic nanoparticle hybrid system with non-Markovian dynamics

Photon-number statistics of the emitted photons from a quantum dot placed in the vicinity of a metallic nanoparticle (with either shell or solid-sphere geometry) in the non-Markovian regime is investigated theoretically. In the model scheme, the quantum dot is considered as a InAs three- level system in Lambda-type configuration with two transition channels. One of channels is driven by a polarized classical field while the two channels are coupled to the plasmon modes. Plasmon resonance modes of a nanoshell, in contrast of a nanosphere, are tunable at demand frequency by controlling the thickness and the materials of the core and the embedding media. The results reveal that the emitted photons from the hybrid system under consideration are antibunched. Moreover, the anti- bunching behavior of the emitted photons can be controlled by the geometrical parameters of the system, namely, the quantum dot-metal nano particle separation distance, as well as the system's physical parameters including the detuning frequency of the quantum dot transitions with respect to the surface plasmon modes, and the Rabi frequency of the polarized driving field. Additionally, the studied system has the potential to be a highly controllable single-photon source.

physics.optics↗

arXiv2017

Highly entangled-photon pairs generated from the biexciton cascade transition in a quantum dot-metal nanoparticle hybrid system

The entanglement between photon pairs generated from the biexciton cascade transition in a semi- conductor quantum dot located in the vicinity of a metal nanoparticle is theoretically investigated. In the model scheme, the biexciton-exciton and exciton-ground state transitions are assumed to be coupled to two principal plasmon modes of orthogonal polarizations. For a broad spectral window, because the horizontal and vertical spectra are overlapped, the biexciton and exciton photons are degenerate in energy. This allows us to overcome the natural splitting between the intermediate exciton states. Moreover, the degree of entanglement depends on the geometrical parameters of the system. i.e., the radius of the metal nanoparticle and the distance between the quantum dot and the nanoparticle. The results reveal that such a hybrid system profoundly modifies the photon entanglement even in the absence of strong coupling between the emitter and the metal nanosphere.

quant-ph↗