Quantization Of Energy Spectrum Research Articles

Intrinsic quantum dynamics of particles in brane gravity

The Newtonian dynamics of particles in brane gravity is investigated. Due to the coupling of the particles’ energy–momentum tensor to the tension of the brane, the particle is semi-confined and oscillates along the extra dimension. We demonstrate that the frequency of these oscillations is proportional to the kinetic energy of the particle in the brane. We show that the classical stability of particle trajectories on the brane gives us the Bohr–Sommerfeld quantization condition. The particle’s motion along the extra dimension allows us to formulate a geometrical version of the uncertainty principle. Furthermore, we exhibited that the particle’s motion along the extra dimension is identical to the time-independent Schrödinger equation. The dynamics of a free particle, particles in a box, a harmonic oscillator, a bouncing particle, and tunneling are re-examined. We show that the particle’s motion along the extra dimension yields a quantized energy spectrum for bound states.

Hybrid coupling optomechanical assisted nonreciprocal photon blockade

The properties of the open quantum system in quantum information is a science now extensively investigated more generally as a fundamental issue for a variety of applications. Usually, the states of the open quantum system might be disturbed by decoherence which will reduce the fidelity in the quantum information processing. So it is better to eliminate the influence of the environment. However, as part of the composite system, rational use of the environment system could be beneficial to quantum information processing. Here we theoretically studied the environment induced quantum nonlinearity and energy spectrum tuning method in the optomechanical system. And we found that the dissipation coupling of the hybrid dissipation and dispersion optomechanical system can induce the coupling between the environment and system in the cross-Kerr interaction form. When the symmetry is broken with a directional auxiliary field, the system exhibits the non-reciprocal behavior during the photon excitation and photon blockade for the clockwise and counterclockwise modes of the whispering gallery mode microcavity. Furthermore, we believe that the cross-Kerr coupling can be more widely used in quantum information processing and quantum simulation.

Generalized Uncertainty Principle in Cosmology with Supersymmetry Quantum Mechanics

In this paper, we exactly solve the Wheeler-DeWitt equation in the presence of a conformally coupled scalar field and in the context of the generalized uncertainty principle (GUP). The GUP-corrected Wheeler—De Witt equation in momentum space leads us to introduce factorization method. This method helps us to obtain the exact solution for the corresponding system. So, here we factorize the second-order equation in terms of first-order operators. These first-order operators help us to arrange partner potential and superpotential. Also, we achieve the general quantum stats and energy spectrum for GUP with conformally coupled scalar field system. Also, we show that the stability of a system with the energy spectrum with some conditions.

Electronic Structure and Itinerant Magnetism of Hydrogenated Graphene Nanofilms

The peculiarities of spin-polarized electronic structure of multilayer graphene nanofilm (4-GNL:H) within the framework of Kohn --- Sham approximation were studied in the present work. The calculated band structure and spin-resolved electronic energy spectrum of the 4-GNL:H system were correlated with experimental UPS and XANES spectra of thin hydrogenated a-C:H films. As the band structure calculations show there is a dimensional quantization of energy spectrum in the 4-GNL:H system, and the energy gap of 0.11 eV appears in the spectrum. The self-consistent calculations also predict the existence of itinerant magnetism in the system, conditioned by hydrogen chemisorption.

From classical periodic orbits in integrable $ \pi$-rational billiards to quantum energy spectrum

In the present paper, we establish a remarkable connection between the length of the periodic orbit of a classical particle enclosed in a class of 2-dimensional planar billiards and the energy of a quantum particle confined to move in an identical region with infinitely high potential wall on the boundary. We observe that the quantum energy spectrum of the particle is in exact one-to-one correspondence with the spectrum of the amplitude squares of the periodic orbits of a classical particle for the class of integrable billiards considered. We have established the results by geometric constructions and exploiting the method of reflective tiling and folding of classical trajectories. We have further extended the method to 3-dimensional billiards, for which exact analytical results are scarcely available --exploiting the geometric construction, we determine the exact energy spectra of two new tetrahedral domains which we believe are integrable. We test the veracity of our results by comparing them with numerical results.

A quantisation procedure in the presence of an initial Kasner singularity: primordial gravitational waves from triaxially anisotropic pre-inflation

In this paper, we discuss quantisation of cosmological tensor perturbations in the Kasner–de Sitter (KdS) space-time as a model of (pre-)inflation. Quantisation in such an anisotropic background has been argued to be problematic based on the fact that the initial Kasner singularity, where the spatial anisotropy blows up, causes divergences to the effective frequencies squared for the perturbations, which render the standard quantisation procedure relying on the existence of an adiabatic vacuum state inexecutable. Here, an essential aspect of the problem is that the ability in determining the quantum spectra of the fields is restricted. Without its knowledge, one cannot even choose physically favourable states like the Bunch–Davies vacuum in de Sitter. We here argue that this difficulty may be circumvented if only there is a period, even if temporal, after the singularity where certain adiabatic conditions for the fields are met and the standard procedure of second quantisation can be carried out within the framework of the WKB approximation. We demonstrate that our prescription for determining the quantum energy spectrum is useful in making physically meaningful predictions for the primordial gravitational waves (PGWs) in triaxially anisotropic KdS backgrounds. We confirm that, on short wave-length scales, the resulting spectrum and directional distribution of the PGWs are the same as de Sitter inflation, namely, scale invariant and isotropic.

Monodromy in non-integrable systems on certain compact classical phase spaces

On the example of bending vibrational polyads of the acetylene molecule (C2H2) in the approximation of the 1:1:1:1 resonant oscillator with axial symmetry, whose geometry is similar to the n-shell approximation of the perturbed hydrogen atom, we show how remaining invariant tori of the underlying classical non-integrable system form a nontrivial continuous family with monodromy. We read this monodromy off the quantum energy spectrum which was observed experimentally by spectroscopists, and we uncover its origins through the particular topology, geometry, and symmetry. We explain how monodromy characterizes the chaotic region surrounded by the tori. We detail the explicit correspondence between the bending polyads of C2H2 and the n-shells of the hydrogen atom, and uncover the dynamical SO(3) symmetry of the bending polyads and the corresponding spherically localized vibrational states.

A further study of the matte black-body

A deduction of the radiation intensity at see level is deduced by using a semiclassical approach by means of the quantum energy spectrum deduced from the driven damped harmonic oscillator, the ergodic theorem and the mean energy obtained by using the Abraham equation of motion for a charged particle. The method is based on using the quantum energy values of a modified Caldirola–Kanai Hamiltonian calculated by Um et al., (2002) with a particular driven force.

The Quantum Mechanics of a Rolling Molecular \u201cNanocar\u201d

We formulate a mathematical model of a rolling “molecular wheelbarrow”—a two-wheeled nanoscale molecular machine—informed by experiments on molecular machines recently synthesized in labs. The model is a nonholonomic system (briefly, a system with non-integrable velocity constraints), for which no general quantization procedure exists. Nonetheless, we successfully embed the system in a Hamiltonian one and then quantize the result using geometric quantization and other tools; we extract from the result the quantum mechanics of the molecular wheelbarrow, and derive explicit formulae for the quantized energy spectrum. We also study a few variants of our model, some of which ignore the model’s nonholonomic constraints. We show that these variants have different quantum energy spectra, indicating that in such systems one should not ignore the nonholonomic constraints, since they alter in a non-trivial way the energy spectrum of the molecule.

Two-Dimensional Triplet Magnetoexcitons and a Magnetofermionic Condensate in the GaAs/AlGaAs Heterostructures

A fundamentally new collective state, namely, the magnetofermionic condensate, is discovered during photoexcitation of a sufficiently dense gas of long-lived triplet cyclotron magnetoexcitons in a twodimensional Hall insulator with a high electron mobility, a filling factor of ν = 2, and temperatures of T < 1 K. The condensed phase coherently interacts with an external electromagnetic field, exhibits superradiant properties in the recombination of correlated condensate electrons with heavy holes in the valence band, and spreads nondissipatively in the layer of a two-dimensional electron gas to macroscopical large distances, transferring an integer spin. The observed effects are explained in terms of a coherent condensate in a nonequilibrium system of two-dimensional fermions with a fully quantized energy spectrum, in which a degenerate ensemble of long-lived triplet magnetoexcitons obeying the Bose statistics is present.

Двумерные триплетные магнитоэкситоны и магнетофермионный конденсат в GaAs/AlGaAs гетероструктурах

AbstractA fundamentally new collective state, namely, the magnetofermionic condensate, is discovered during photoexcitation of a sufficiently dense gas of long-lived triplet cyclotron magnetoexcitons in a twodimensional Hall insulator with a high electron mobility, a filling factor of ν = 2, and temperatures of T &lt; 1 K. The condensed phase coherently interacts with an external electromagnetic field, exhibits superradiant properties in the recombination of correlated condensate electrons with heavy holes in the valence band, and spreads nondissipatively in the layer of a two-dimensional electron gas to macroscopical large distances, transferring an integer spin. The observed effects are explained in terms of a coherent condensate in a nonequilibrium system of two-dimensional fermions with a fully quantized energy spectrum, in which a degenerate ensemble of long-lived triplet magnetoexcitons obeying the Bose statistics is present.

2D magnetofermionic condensate in GaAs/AlGaAs heterostructures

A principally new collective state—magnetofermionic condensate—was found upon excitation of long-lived triplet cyclotron magnetoexcitons in a Hall insulator with high electron mobility and filling factor ν = 2 at low temperatures T &amp;lt; 1 K. The condensed phase interacts coherently with external electromagnetic field, exhibits superradiant properties and spreads over macroscopic distances from the excitation spot along the surface of the 2D structure due to its low viscosity. The observed effects are explained in terms of a coherent condensate arising in the non-equilibrium system of 2D fermions with a fully quantized energy spectrum, in which a degenerate ensemble of long-lived triplet magnetoexcitons with Bose statistics is formed. The condensation occurs in the space of magnetic translation vectors. Under these conditions, new opportunities arise for future physical studies.

Symmetry Breaking Induced Geometric Surfaces with Topological Curves in Quantum and Classical Dynamics of the SU(2) Coupled Oscillators

AbstractIn the three‐dimensional (3D) transversely symmetric oscillator, there are plentiful degeneracies and gaps in the quantum energy spectrum as a function of the ratio of the transverse to longitudinal frequency. It is theoretically verified that while the SU(2) interaction destroys the original degeneracies, numerous new degeneracies and gaps emerge around the original degeneracies to form a similar fine energy spectrum. The classical trajectories at the emergent degeneracies are analyzed to be localized on the 3D parametric surfaces which are constituted by the topologically invariant curves in the transverse tomography. The quantum coherent states are exploited to develop the wave functions that correspond to the 3D geometric surfaces in classical dynamics. Furthermore, the wave structures of the stationary coherent states at small quantum numbers are explored and found to display peculiar patterns with symmetries related to classical trajectories.

Magnetofermionic condensate in two dimensions.

Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations.

Quantized Energy Spectrum and Modified Andreev Bound States of a Superconductor with Generalized Uncertainty Principle

The effect of a minimal uncertainty in position or momentum measurement on a superconductor system is investigated. The Bogoliubov-de Gennes equations for the quasiparticle states in a linear potential are solved exactly, where the position and momenta are assumed to obey the modified commutation relations. It is found that the quantized energy spectrum of the superconductor could be induced by generalized uncertainty principle (GUP) directly. We also discuss the GUP-corrected Andreev bound states and supercurrent in a SNS structure. The results imply that the GUP effect in superconductor systems could be testable under present experimental condition.

Spin–orbit-coupled BEC in a double-well potential: Quantum energy spectrum and flat band

Spin–orbit-coupled Bose–Einstein condensates (BECs) provide a powerful platform for studies on physical problems in various fields. Here we study the energy spectrum of a tunable spin–orbit-coupled BEC in a double-well potential with adjustable Raman laser intensity. We find in the single-particle spectrum there is a highly degenerate flat band in the ground state of the BEC, which remains stable against changes of the Raman strength. Many-body interactions between atoms remove this high degeneracy. Analytical results for particular cases are obtained by using the perturbation theory, which are in good agreement with the numerical results.

Automated drawing system of quantum energy levels

The purpose of this work is to derive an automated system that provides advantageous drawings of energy spectra for quantum systems (nuclei, atoms, molecules, etc.) required in various physical sciences. The automation involves the development of appropriate computational code and graphical imaging system based on raw data insertion, theoretical calculations and experimental or bibliographic data insertion. The system determines the appropriate scale to depict graphically with the best possible way in the available space. The presently developed code operates locally and the results are displayed on the screen and can be exported to a PostScript file. We note its main features to arrange and visualize in the available space the energy levels with their identity, taking care the existence in the final diagram the least auxiliary deviations. Future improvements can be the use of Java and the availability on the Internet. The work involves the automated plotting of energy levels in molecules, atoms, nuclei and other types of quantized energy spectra. The automation involves the development of an appropriate computational code and graphical imaging system.

Comparative quantum and semiclassical analysis of atom-field systems. I. Density of states and excited-state quantum phase transitions

We study the non-integrable Dicke model, and its integrable approximation, the Tavis-Cummings model, as functions of both the coupling constant and the excitation energy. Excited-state quantum phase transitions (ESQPT) are found analyzing the density of states in the semi-classical limit and comparing it with numerical results for the quantum case in large Hilbert spaces, taking advantage of efficient methods recently developed. Two different ESQPTs are identified in both models, which are signaled as singularities in the semi-classical density of states, one {\em static} ESQPT occurs for any coupling, whereas a dynamic ESQPT is observed only in the superradiant phase. The role of the unstable fixed points of the Hamiltonian semi-classical flux in the occurrence of the ESQPTs is discussed and determined. Numerical evidence is provided that shows that the semi-classical result describes very well the tendency of the quantum energy spectrum for any coupling in both models. Therefore the semi-classical density of states can be used to study the statistical properties of the fluctuation in the spectra, a study that is presented in a companion paper.

Spinless Particles in Exponentially Varying Electric and Magnetic Fields

We investigate the motion of the charged spin-0 particles subjected to the space-dependent electric and magnetic fields. By selecting the external fields oriented parallel and orthogonal to each other, exact solutions of the motion are obtained for the nonrelativistic and the relativistic cases. The quantized energy spectrum is determined by using the solutions obtained for the motion of the particles and dependence of the energy on the strengths of the electric and magnetic fields is discussed. We compared the energy spectrum of the nonrelativistic and the relativistic particles by using the numerical results obtained for the first few quantum levels.

Hofstadter’s butterfly and the fractal quantum Hall effect in moiré superlattices

Electrons moving through a spatially periodic lattice potential develop a quantized energy spectrum consisting of discrete Bloch bands. In two dimensions, electrons moving through a magnetic field also develop a quantized energy spectrum, consisting of highly degenerate Landau energy levels. When subject to both a magnetic field and a periodic electrostatic potential, two-dimensional systems of electrons exhibit a self-similar recursive energy spectrum. Known as Hofstadter's butterfly, this complex spectrum results from an interplay between the characteristic lengths associated with the two quantizing fields, and is one of the first quantum fractals discovered in physics. In the decades since its prediction, experimental attempts to study this effect have been limited by difficulties in reconciling the two length scales. Typical atomic lattices (with periodicities of less than one nanometre) require unfeasibly large magnetic fields to reach the commensurability condition, and in artificially engineered structures (with periodicities greater than about 100 nanometres) the corresponding fields are too small to overcome disorder completely. Here we demonstrate that moiré superlattices arising in bilayer graphene coupled to hexagonal boron nitride provide a periodic modulation with ideal length scales of the order of ten nanometres, enabling unprecedented experimental access to the fractal spectrum. We confirm that quantum Hall features associated with the fractal gaps are described by two integer topological quantum numbers, and report evidence of their recursive structure. Observation of a Hofstadter spectrum in bilayer graphene means that it is possible to investigate emergent behaviour within a fractal energy landscape in a system with tunable internal degrees of freedom.