Matrix-operator difference-differential equations for dynamics of spectroscopic transitions in 1D multiqubit exchange coupled (para)magnetic and optical systems by strong dipole-photon and dipole-phonon coupling are derived within the framework of quantum electrodynamics and quantum phonon field theory. It has been established, that in the model considered the relaxation processes are of pure quantum character, which is determined by the formation of the coherent system of the resonance phonons and by the appearence along with absorption process of EM-field energy the coherent emission process, acompanying by phonon Rabi quantum oscillation, which can be time-shared. For the case of radiospectroscopy it corresponds to the possibility of the simultaneous observation along with (para)magntic spin resonance the acoustic spin resonance. Theoretical conclusions are confirmed experimentally in radiospectroscopy. It has been found in particular, that the lifetime of coherent state of collective subsystem of resonance phonons in disordered carbon samples - anthracites of medium-scale metamorphism - is very long and even by room temperature it is evaluated in $\sim 10$ ms. The phenomenon of the formation of the coherent system of the resonance phonons can be used in a number of practical applications, in particular by elaboration of logic quantum systems including quantum computers and quantum communication systems.
Matrix-operator difference-differential equations for dynamics of spectroscopic transitions in 1D multiqubit exchange coupled (para)magnetic and optical systems by strong dipole-photon and dipole-phonon coupling are derived within the framework of quantum electrodynamics and quantum phonon field theory. It has been established, that in the model considered the relaxation processes are of pure quantum character, which is determined by the formation of the coherent system of the resonance phonons and by the appearence along with absorption process of EM-field energy the coherent emission process, acompanying by phonon Rabi quantum oscillation, which can be time-shared. For the case of radiospectroscopy it corresponds to the possibility of the simultaneous observation along with (para)magntic spin resonance the acoustic spin resonance. Theoretical conclusions are confirmed experimentally in radiospectroscopy. It has been found in particular, that the lifetime of coherent state of collective subsystem of resonance phonons in disordered carbon samples - anthracites of medium-scale metamorphism - is very long and even by room temperature it is evaluated in ∼10 ms. The phenomenon of the formation of the coherent system of the resonance phonons can be used in a number of practical applications, in particular by elaboration of logic quantum systems including quantum computers and quantum communication systems.
Matrix-operator difference-differential equations for dynamics of spectroscopic transitions in 1D multiqubit exchange-coupled (para)magnetic and optical systems by strong dipole-photon and dipole-phonon coupling are derived within the framework of quantum field theory. It has been established that by strong dipole-photon and dipole-phonon coupling the formation of long-lived coherent system of the resonance phonons takes place, and relaxation processes acquire pure quantum character. It is determined by the appearance of coherent emission process of EM-field energy, for which the resonance phonon system is responsible. Emission process is accompanied by phonon Rabi quantum oscillation, which can be time-shared from photon quantum Rabi oscillations, accompanying coherent absorption process of EM-field energy. For the case of radio spectroscopy, it corresponds to the possibility of the simultaneous observation along with (para)magntic spin resonance, the acoustic spin resonance.
Strong coupling of light and matter is an essential element of cavity quantum electrodynamics (cavity-QED) and quantum optics, which may lead to novel mixed states of light and matter and to applications such as quantum computation. In the strong-coupling regime, where the coupling strength exceeds the dissipation, the light-matter interaction produces a characteristic vacuum Rabi splitting. Therefore, strong coupling can be utilized as an effective coherent interface between light and matter (in the form of electron charge, spin or superconducting Cooper pairs) to achieve components of quantum information technology including quantum memory, teleportation, and quantum repeaters. Semiconductor quantum dots, nuclear spins and paramagnetic spin systems are only some of the material systems under investigation for strong coupling in solid-state physics. Mixed states of light and matter coupled via electric dipole transitions often suffer from short coherence times (nanoseconds). Even though magnetic transitions appear to be intrinsically more quantum coherent than orbital transitions, their typical coupling strengths have been estimated to be much smaller. Hence, they have been neglected for the purposes of quantum information technology.\nHowever, we predict that strong coupling is feasible between photons and a ferromagnetic nanomagnet, due to exchange interactions that cause very large numbers of spins to coherently lock together with a significant increase in oscillator strength while still maintaining very long coherence times. In order to examine this new exciting possibility, the interaction of a ferromagnetic nanomagnet with a single photonic mode of a cavity is analyzed in a fully quantum-mechanical treatment. Exceptionally large quantum-coherent magnet-photon coupling with coupling terms in excess of several THz are predicted to be achievable in a spherical cavity of ∼ 1 mm radius with a nanomagnet of ∼ 100 nm radius and ferromagnet resonance frequency of ∼ 200 GHz. This should substantially exceed the coupling observed in solids between orbital transitions and light. Eigenstates of the nanomagnet-photon system correspond to entangled states of spin orientation and photon number over 105 values of each quantum number. Initial coherent state of definite spin and photon number evolve dynamically to produce large coherent oscillations in the microwave power with exceptionally long dephasing times of few seconds. In addition to dephasing, several decoherence mechanisms including elementary excitation of magnons and crystalline magnetic anisotropy are investigated and shown to not substantially affect coherence upto room temperature. For small nanomagnets the crystalline magnetic anisotropy of the magnet strongly localize the eigenstates in photon and spin number, quenching the potential for coherent states and for a sufficiently large nanomagnet the macrospin approximation breaks down and different domains of the nanomagnet may couple separately to the photonic mode. Thus the optimal nanomagnet size is predicted to be just below the threshold for failure of the macrospin approximation. Moreover, it is shown that initially unentangled coherent states of light (cavity field) and spin (nanomagnet spin orientation) can be phase-locked to evolve into a coherent entangled states of the system under the influence of strong coupling.
In this thesis we study the role of nonradiative degrees of freedom on quantum optical properties of mesoscopic quantum dots placed in the structured electromagnetic reservoir of a photonic crystal. We derive a quantum theory of the role of acoustic and optical phonons in modifying the optical absorption lineshape, polarization dynamics, and population dynamics of a two-level atom (quantum dot) in the ``colored" electromagnetic vacuum of a photonic band gap (PBG) material. This is based on a microscopic Hamiltonian describing both radiative and vibrational processes quantum mechanically. Phonon sidebands in an ordinary electromagnetic reservoir are recaptured in a simple model of optical phonons using a mean-field factorization of the atomic and lattice displacement operators. Our formalism is then used to treat the non-Markovian dynamics of the same system within the structured electromagnetic density of states of a photonic crystal. We elucidate the extent to which phonon-assisted decay limits the lifetime of a single photon-atom bound state and derive the modified spontaneous emission dynamics due to coupling to various phonon baths. We demonstrate that coherent interaction with undamped phonons can lead to enhanced lifetime of a photon-atom bound state in a PBG by (i) dephasing and reducing the transition electric dipole moment of the atom and (ii) reducing the quantum mechanical overlap of the state vectors of the excited and ground state (polaronic shift). This results in reduction of the steady-state atomic polarization but an increase in the fractionalized upper state population in the photon-atom bound state. We demonstrate, on the other hand, that the lifetime of the photon-atom bound state in a PBG is limited by the lifetime of phonons due to lattice anharmonicities (break-up of phonons into lower energy phonons) and purely nonradiative decay. We demonstrate how these additional damping effects limit the extent of the polaronic (Franck-Condon) shift of the atomic excited state. We also derive the modified polarization decay and dephasing rates in the presence of such damping. This leads to a microscopic, quantum theory of the optical absorption lineshapes. Our model and formalism provide a starting point for describing dephasing and relaxation in the presence of external coherent fields and multiple quantum dot interactions in electromagnetic reservoirs with radiative memory effects.
Aims/ objectives: The consideration of the three tasks, formulated below, is the aim of the given work. The first task of the paper presented is to analyse the existing viewpoints and to give the conclusion on the real photon status. To represent the clear and understandable explanation of the nature of the corpuscular-wave dualism and to give an insight into physics of the photon absorption process is the second task of the given review. The third task of the paper presented - to give the experimental proof for the Dirac theoretical conclusion, that the transitions of the quantum system from an equilibrium state to an excited state are not instantaneous and that a part of the time, related to a duration of the stay between the states can be determined. Study design: The theory of quantum Fermi liquid, the developed Dirac quantisation method, the theory of quantum Rabi oscillations and experimental results of the stationary electron spin resonance (ESR) spectroscopy were used. Place and Duration of Study: Heat-Mass Transfer Institute of National Academy of Sciences of RB, Belarusian State University and M.V.Lomonosov Moscow State University, between January 2014 and July 2014. Methodology: We have used the quantum 1D Fermi liquid model for the description of 1D correlated electronic systems, elaborated in the application to the quantised electromagnetic (EM) field, the Jaynes-Cummings model (JCM) of quantum Rabi oscillations, new Slepyan-Yerchak- Hoffmann-Bass model of propagating quantum Rabi oscillations and new fully quantum space-time quantisation method. Results: The status of the photon in the modern physics is analysed. In the physics of elementary particles the photon is considered to be the genuine elementary particle. The development of the viewpoint of the experts in the quantum electrodynamics theory is considered. It was established its change from the opinion, that the description of the photon to be the particle is impossible to the viewpoint on the photon to be the particle, that is, coinciding with the viewpoint, represented in the Standard Model of the physics of elementary particles. The quantized Maxwellian EM-field represents itself, according to the new conceptual model reviewed, the sets of 1D rays, the own structure of each ray is discrete - 1D-lattice of spin-1 bosons. Therefore, the structure of EM-field in boson model resembles the structure of the carbon frame of organic polymers like to trans-polyacetylene in the matter. Photons in the given concept are the corpuscles, propagating along EM-field boson-”atomic” chains. In other words, EM-field boson- ”atomic” chains represents themselves the medium for the photons’ propagation. In the structural aspect photons in usual conditions are chargeless spin 1/2 topological relativistic solitons of Su- Schrieffer-Heeger family. Spinless charged solitons of the same family can also be formed in socalled ”doped” EM-field structure. The origin of waves in the EM-field boson-”atomic” structure is determined by the mechanism, being to be quite analogous to the formation of Bloch waves in the solid state of condensed matter. The expression for the corresponding wave function representing itself the set of Bloch-like waves is given. Just, the given function allows to describe correctly the wave properties of the light, including the interference. Corpuscular properties of EM-field including those ones by its interaction with matter are described by independent scalar field function obtained from the solution of Schr¨odinger equation [nonstationary in general case] and usually called wave function. The term ”wave” seems to be incorrect in application to the given function and has to be corrected in all literature on quantum theory, including textbooks. The physics of quantum absorption process is analysed. It is argued, in accordance with Dirac guess, that the photon revival takes place by its absorption. It is concluded, that after the energy and impulse transfer to the absorbing system the photon state is a pinned state, in which it possesses the only by spin. The reviewed rather unusual spectroscopic electron spin resonance absorption characteristics of carbon nanotubes and superconducting ceramics, obtained with the participation of the authors and of the other research groups and being earlier unexplained, were correctly interpreted within the frames of the phenomenological model of the spectroscopic transition dynamics with finite time of the transfer of absorbing systems in an excited state. Moreover, it was established, that the time of the transfer of absorbing systems in an excited state governs the characteristics of the stationary ESR signal registered in the carbon nanotubes and superconducting ceramics. Conclusion: To describe correctly the EM-field properties including corpuscular-wave dualism [which is explained in a natural way] it is necessary to use the full variant of Schr¨ odinger’s theory, taking into consideration two scalar functions. The result, that the time of the transfer of absorbing systems into an excited state governs the characteristics of the stationary ESR signal is significant for the stationary spectroscopy at all, since the transfer of absorbing systems in an excited state is considered in the stationary spectroscopy at present to be instantaneous.
Investigation of the spin-cavity polaritons (SCP) is important since they play decisive role for the creating long-storage quantum memories and optical interfaces, polaritonic chemistry and for the elaborating of masers, especially those which operate at room temperature being of the great significance for a lot of different applications. In this report, we suggest almost completely classical model for the description of the polaritonic peaks conditioned both by free and forced Rabi oscillations of the SCP system. Our investigation is based on the linearized coupled differential equations we derived semi-classically for the magnetization component of the transition of the spin triplet states and the varying field in a cavity, when the empty cavity is exactly tuned to the transition. The normal frequencies of this system of equations were found and the corresponding graphs were constructed for the appropriate values of the parameters. It is shown that the increase of the spin-photon coupling can cause both pushing apart normal frequencies at a mutual decay rate (which is the known effect), and merging together normal decay rates at a mutual frequency (which is the predicted here effect). Polariton peaks observable by the cavity transmission function and by electron paramagnetic resonance (EPR) in the form of absorption and dispersion signals were also investigated and corresponding graphs were constructed. At that, instead of a transition of spin triplet states, a variety of other two-level systems (atoms, molecules, excitons and so on) can act as emitters. Since the value of the spin-photon coupling is of great interest for applied scientists, obtaining this value by comparing our results with experimental data is of great importance.
The quantum mechanical description of the transient resonance Raman scattering including both the excitation and observation processes is presented. To obtain the general formula for the actually observable transient emission spectrum, the following way of observation is proposed; the use of a spectroscope for wave transformation and a photon-counter behind it for particle transformation. On its basis, the transient emission spectrum and its average over the duration time of photon-counting are explicitly defined especially for systems small compared with the spacial extent of an incident pulse. It will be shown that the transient emission spectrum conforms to the minimal case of the Heisenberg uncertainty relation through the restriction for the emission time coming from the Fourier transform of the transfer function of the spectroscope. The theory is applied to a strongly coupled localized electron-phonon system. It will be shown that what aspects of the correlation between absorption and emission are disclosed depends strongly on both the ways of excitation and observation.