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1
Rabani, Eran, Kunimasa Miyazaki, and David R. Reichman. "Quantum mode-coupling theory for binary mixtures." Journal of Chemical Physics 122, no. 3 (January 15, 2005): 034502. http://dx.doi.org/10.1063/1.1832593.
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Loring, Roger F., and Shaul Mukamel. "Self-consistent mode-coupling theory of quantum percolation." Physical Review B 33, no. 11 (June 1, 1986): 7708–14. http://dx.doi.org/10.1103/physrevb.33.7708.
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Schirmacher, W., E. Maurer, and M. Pöhlmann. "Quantum mode-coupling theory for vibrational excitations of glasses." physica status solidi (c) 1, no. 1 (January 2004): 17–20. http://dx.doi.org/10.1002/pssc.200303641.
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Rabani, Eran, and David R. Reichman. "QUANTUM MODE-COUPLING THEORY: Formulation and Applications to Normal and Supercooled Quantum Liquids." Annual Review of Physical Chemistry 56, no. 1 (May 5, 2005): 157–85. http://dx.doi.org/10.1146/annurev.physchem.56.092503.141138.
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BELYAEV, V. M. "SOFT MODE CONTRIBUTION TO PATH INTEGRALS." International Journal of Modern Physics A 08, no. 23 (September 20, 1993): 4019–30. http://dx.doi.org/10.1142/s0217751x93001648.
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A method for nonperturbative path integral calculation is proposed. Quantum mechanics as the simplest example of a quantum field theory is considered. All modes are decomposed into hard (with frequencies [Formula: see text]) and soft (with frequencies [Formula: see text]) ones, where ω0 is some parameter. Hard mode contribution is considered through weak coupling expansion. A low energy effective Lagrangian for soft modes is used. In the case of soft modes we apply a strong coupling expansion. To realize this expansion a special basis in functional space of trajectories is considered. A good convergency for the pro posed procedure in the case of potential V(x)=λx4 is demonstrated. The ground state energy of the unharmonic oscillator is calculated.
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Ciracì, Cristian, Radoslaw Jurga, Muhammad Khalid, and Fabio Della Sala. "Plasmonic quantum effects on single-emitter strong coupling." Nanophotonics 8, no. 10 (August 14, 2019): 1821–33. http://dx.doi.org/10.1515/nanoph-2019-0199.
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AbstractCoupling between electromagnetic cavity fields and fluorescent molecules or quantum emitters can be strongly enhanced by reducing the cavity mode volume. Plasmonic structures allow light confinement down to volumes that are only a few cubic nanometers. At such length scales, nonlocal and quantum tunneling effects are expected to influence the emitter interaction with the surface plasmon modes, which unavoidably requires going beyond classical models to accurately describe the electron response at the metal surface. In this context, the quantum hydrodynamic theory (QHT) has emerged as an efficient tool to probe nonlocal and quantum effects in metallic nanostructures. Here, we apply state-of-the-art QHT to investigate the quantum effects on strong coupling of a dipole emitter placed at nanometer distances from metallic particles. A comparison with conventional local response approximation (LRA) and Thomas-Fermi hydrodynamic theory results shows the importance of quantum effects on the plasmon-emitter coupling. The QHT predicts qualitative deviation from LRA in the weak coupling regime that leads to quantitative differences in the strong coupling regime. In nano-gap systems, the inclusion of quantum broadening leads to the existence of an optimal gap size for Rabi splitting that minimizes the requirements on the emitter oscillator strength.
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Yan, Xiao-Hong, Yi-Jie Niu, Hong-Xing Xu, and Hong Wei. "Strong coupling of single plasmonic nanoparticles and nanogaps with quantum emitters." Acta Physica Sinica 71, no. 6 (2022): 067301. http://dx.doi.org/10.7498/aps.71.20211900.
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In cavity quantum electrodynamics, when the interaction between quantum emitter and cavity mode is strong enough to overcome the mean decay rate of the system, it will enter into a strong coupling regime, thereby forming part-light part-matter polariton states. Strong coupling can serve as a promising platform for room temperature Bose-Einstein condensation, polariton lasing, single photon nonlinearity, quantum information, etc. Localized surface plasmons supported by single metal nanostructures possess extremely small mode volume, which is favorable for realizing strong coupling. Moreover, the nanoscale dimensions of plasmonic structures can facilitate the miniaturization of strong coupling systems. Here, the research progress of strong plasmon-exciton coupling between single metal nanoparticles/nanogaps and quantum emitters is reviewed. The theory background of strong coupling is first introduced, including quantum treatment, classical coupled oscillator model, as well as the analytical expressions for scattering and photoluminescence spectra. Then, strong coupling between different kinds of plasmonic nanostructures and quantum emitters is reviewed. Single metal nanoparticles, nanoparticle dimers, and nanoparticle-on-mirror structures constitute the most typical plasmonic nanostructures. The nanogaps in the latter two systems can highly concentrate electromagnetic field, providing optical nanocavities with smaller mode volume than single nanoparticles. Therefore, the larger coupling strength can be achieved in the nanogap systems, which is conducive to strong coupling at the single-exciton level. In addition, the active tuning of strong coupling based separately on thermal, electrical and optical means are reviewed. The energy and oscillator strength of the excitons in transition metal dichalcogenide (TMDC) monolayers are dependent on temperature. Therefore, the strong coupling can be tuned by heating or cooling the system. The excitons in TMDC monolayers can also be tuned by electrical gating, enabling electrical control of strong coupling. Optically tuning the quantum emitters provides another way to actively control the strong coupling. Overall, the research on active tuning of strong plasmon-exciton coupling is still very limited, and more investigations are needed. Finally, this review is concluded with a short summary and the prospect of this field.
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Wang, Zhihang, Lingyao Li, Xiaoqi Shi, Jiamin Xiao, Zhicheng Guo, and Wenxin Wang. "Bound states in the continuum induced by the strong coupling within the plasmonic lattices." Journal of Applied Physics 133, no. 15 (April 21, 2023): 153101. http://dx.doi.org/10.1063/5.0148144.
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Bound states in the continuum (BICs), manifesting themselves as the collapse of Fano resonance, are observed in many photonic and plasmonic systems. The BICs have been studied systematically through various methods such as the topological photonics analysis, temporal coupled mode theory, multipole decomposition method, and the cavity quantum electrodynamics (CQED) method. Since CQED can give a macroscopic and intrinsic description of light–matter interaction, it is expected to study BIC that participates in strong coupling. What is more, the relation between coupling strength, the Fano parameter, and the asymmetry property of BICs needs to be clarified. In this paper, we investigated the strong coupling between the cavity mode and Bloch-surface plasmon polariton (Bloch-SPP) mode induced by BICs within the plasmonic lattices of the metal-dielectric-metal (MDM) layer. The properties of strong coupling and BIC were revealed theoretically by the quantum model based on the CQED. The increase in the Fano parameters of BICs was proved to facilitate the coupling strength, which was indicated by the monotonically increasing relation between the Fano parameter and the coupling strength. This work may pave the way for flexible modulation and application of BIC in the fields of high-quality plasmonic nanocavity, low-threshold nano-lasers, and quantum information.
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Lytaev, A. A., and I. Yu Popov. "Computation of optical waveguide interaction for quantum gates implementation." Journal of Physics: Conference Series 2086, no. 1 (December 1, 2021): 012153. http://dx.doi.org/10.1088/1742-6596/2086/1/012153.
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Abstract The system of two coupled optical dual-mode waveguides is considered. The coupling of the system is studied to find a circuit for building a control switch for two qubit gates. The classical coupled mode theory is applied and the exact expressions for coupling coefficients are derived. The parameters of the system for performing the desired operations are numerically computed and analysed. The system describing the influence of intermodal interactions is solved numerically. The distortions are analysed.
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XU, GU, DINGZHOU LI, BINGSHEN WANG, and ZHAO-BIN SU. "SEMICLASSICAL THEORY OF EXCITONIC POLARITONS IN A PLANAR SEMICONDUCTOR MICROCAVITY." International Journal of Modern Physics B 14, no. 08 (March 30, 2000): 783–807. http://dx.doi.org/10.1142/s0217979200000662.
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We present a comprehensive theoretical description of quantum well exciton–polaritons imbedded in a planar semiconductor microcavity. The exact nonlacal dielectric response of the quantum well exciton is treated in detail. The 4-spinor structure of the hole subband in the quantum well is considered, including the pronounced band mixing effect. The scheme is self-contained and can be used to treat different semiclassical aspects of the microcavity properties. As an example, we analyze the "selection" rules for the exciton–cavity mode coupling for different excitons.
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Arteaga, Daniel. "Quantum Brownian Representation for the Quantum Field Modes." Advances in High Energy Physics 2009 (2009): 1–29. http://dx.doi.org/10.1155/2009/278759.
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When analyzing the particle-like excitations in quantum field theory it is natural to regard the field mode corresponding to the particle momentum as an open quantum system, together with the opposite momentum mode. Provided that the state of the field is stationary, homogeneous, and isotropic, this scalar two-mode system can be equivalently represented in terms of a pair of quantum Brownian oscillators under a Gaussian approximation. In other words, the two-mode system behaves as if it were interacting linearly with some effective environment. In this paper we build the details of the effective linear coupling and the effective environment, and argue that this quantum Brownian representation provides a simple, universal, and nonperturbative characterization of any single particle-like excitation. As immediate applications of the equivalence, we reanalyze the interpretation of the self-energy in terms of decay rates in a general background state and present the master equation for the field mode corresponding to the particle momentum.
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Pino, Javier del, Johannes Feist, and Francisco J. Garcia-Vidal. "Quantum theory of collective strong coupling of molecular vibrations with a microcavity mode." New Journal of Physics 17, no. 5 (May 22, 2015): 053040. http://dx.doi.org/10.1088/1367-2630/17/5/053040.
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CRANE, LOUIS. "STRING FIELD THEORY FROM QUANTUM GRAVITY." Reviews in Mathematical Physics 25, no. 10 (November 2013): 1343005. http://dx.doi.org/10.1142/s0129055x13430058.
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Recent work on neutrino oscillations suggests that the three generations of fermions in the standard model are related by representations of the finite group A(4), the group of symmetries of the tetrahedron. Motivated by this, we explore models which extend the EPRL model for quantum gravity by coupling it to a bosonic quantum field of representations of A(4). This coupling is possible because the representation category of A(4) is a module category over the representation categories used to construct the EPRL model. The vertex operators which interchange vacua in the resulting quantum field theory reproduce the bosons and fermions of the standard model, up to issues of symmetry breaking which we do not resolve. We are led to the hypothesis that physical particles in nature represent vacuum changing operators on a sea of invisible excitations which are only observable in the A(4) representation labels which govern the horizontal symmetry revealed in neutrino oscillations. The quantum field theory of the A(4) representations is just the dual model on the extended lattice of the Lie group E6, as explained by the quantum McKay correspondence of Frenkel, Jing and Wang. The coupled model can be thought of as string field theory, but propagating on a discretized quantum spacetime rather than a classical manifold.
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KRÁL, KAREL, and CHUNG-YI LIN. "PHONON EXCESS HEATING IN ELECTRONIC RELAXATION THEORY IN QUANTUM DOTS." International Journal of Modern Physics B 22, no. 20 (August 10, 2008): 3439–60. http://dx.doi.org/10.1142/s0217979208048577.
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When the usual operator of the Fröhlich's coupling between electrons and longitudinal optical phonons of semiconductor single quantum dot is used to calculate electronic energy relaxation, a permanent phonon generation in quantum dot is obtained, leading to an artificial effect of permanent heating up of the lattice. The mechanism of the phonon heating is identified here with the influence of the transverse part of the interaction operator. This part is responsible first of all for a tendency to build the polaronic well of an electron in a quantum dot. The effect of overheating is shown to be possibly eliminated to a considerable extent upon removing the transverse part of the interaction with the help of the Lang–Firsov canonical transformation and upon modifying accordingly the longitudinal part of the coupling. The resulting electronic relaxation and optical phonon generation is demonstrated numerically in a relatively simple approximation to electron and phonon self-energy, in which the model of quantum dot is reduced to an electron coupled to a single-LO-phonon mode. It is interesting to see that the removal of the phonon overheating based on the application of the Lang–Firsov canonical transformation has a rather small influence on electronic characteristics calculated with electronic transport equations. In this sense, the long-time limit properties of the electronic subsystem, like the electronic up-conversion and incomplete depopulation effect, calculated earlier, remain nearly untouched.
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Flick, Johannes, Nicholas Rivera, and Prineha Narang. "Strong light-matter coupling in quantum chemistry and quantum photonics." Nanophotonics 7, no. 9 (September 8, 2018): 1479–501. http://dx.doi.org/10.1515/nanoph-2018-0067.
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AbstractIn this article, we review strong light-matter coupling at the interface of materials science, quantum chemistry, and quantum photonics. The control of light and heat at thermodynamic limits enables exciting new opportunities for the rapidly converging fields of polaritonic chemistry and quantum optics at the atomic scale from a theoretical and computational perspective. Our review follows remarkable experimental demonstrations that now routinely achieve the strong coupling limit of light and matter. In polaritonic chemistry, many molecules couple collectively to a single-photon mode, whereas, in the field of nanoplasmonics, strong coupling can be achieved at the single-molecule limit. Theoretical approaches to address these experiments, however, are more recent and come from a spectrum of fields merging new developments in quantum chemistry and quantum electrodynamics alike. We review these latest developments and highlight the common features between these two different limits, maintaining a focus on the theoretical tools used to analyze these two classes of systems. Finally, we present a new perspective on the need for and steps toward merging, formally and computationally, two of the most prominent and Nobel Prize-winning theories in physics and chemistry: quantum electrodynamics and electronic structure (density functional) theory. We present a case for how a fully quantum description of light and matter that treats electrons, photons, and phonons on the same quantized footing will unravel new quantum effects in cavity-controlled chemical dynamics, optomechanics, nanophotonics, and the many other fields that use electrons, photons, and phonons.
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Rabani, Eran, and David R. Reichman. "A self-consistent mode-coupling theory for dynamical correlations in quantum liquids: Rigorous formulation." Journal of Chemical Physics 116, no. 14 (April 8, 2002): 6271–78. http://dx.doi.org/10.1063/1.1458545.
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Triana, Johan F., Mauricio Arias, Jun Nishida, Eric A. Muller, Roland Wilcken, Samuel C. Johnson, Aldo Delgado, Markus B. Raschke, and Felipe Herrera. "Semi-empirical quantum optics for mid-infrared molecular nanophotonics." Journal of Chemical Physics 156, no. 12 (March 28, 2022): 124110. http://dx.doi.org/10.1063/5.0075894.
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Nanoscale infrared (IR) resonators with sub-diffraction limited mode volumes and open geometries have emerged as new platforms for implementing cavity quantum electrodynamics at room temperature. The use of IR nanoantennas and tip nanoprobes to study strong light–matter coupling of molecular vibrations with the vacuum field can be exploited for IR quantum control with nanometer spatial and femtosecond temporal resolution. In order to advance the development of molecule-based quantum nanophotonics in the mid-IR, we propose a generally applicable semi-empirical methodology based on quantum optics to describe light–matter interaction in systems driven by mid-IR femtosecond laser pulses. The theory is shown to reproduce recent experiments on the acceleration of the vibrational relaxation rate in infrared nanostructures. It also provides physical insights on the implementation of coherent phase rotations of the near-field using broadband nanotips. We then apply the quantum framework to develop general tip-design rules for the experimental manipulation of vibrational strong coupling and Fano interference effects in open infrared resonators. We finally propose the possibility of transferring the natural anharmonicity of molecular vibrational levels to the resonator near-field in the weak coupling regime to implement intensity-dependent phase shifts of the coupled system response with strong pulses and develop a vibrational chirping model to understand the effect. The semi-empirical quantum theory is equivalent to first-principles techniques based on Maxwell’s equations, but its lower computational cost suggests its use as a rapid design tool for the development of strongly coupled infrared nanophotonic hardware for applications ranging from quantum control of materials to quantum information processing.
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KHRENNIKOV, ANDREI, MASANORI OHYA, and NOBORU WATANABE. "QUANTUM PROBABILITY FROM CLASSICAL SIGNAL THEORY." International Journal of Quantum Information 09, supp01 (January 2011): 281–92. http://dx.doi.org/10.1142/s0219749911007289.
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We present quantum mechanics (QM) as theory of special classical random signals. On one hand, this approach provides a possibility to go beyond conventional QM: to create a finer description of micro processes than given by the QM-formalism. In fact, we present a model with hidden variables of the wave-type. On the other hand, our approach establishes coupling between quantum and classical information theories. We recall that quantum information theory has already been used for description of the entropy of Gaussian input signals for noisy channels. The entropy of a classical random input was invented as the entropy of the quantum density operator corresponding to the covariance operator of the input process.1 In this paper, we proceed the other way around: we apply classical signal theory to create a measurement model which reproduces quantum probabilities.
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Martínez-Martínez, Luis A., and Joel Yuen-Zhou. "Comment on ‘Quantum theory of collective strong coupling of molecular vibrations with a microcavity mode’." New Journal of Physics 20, no. 1 (February 1, 2018): 018002. http://dx.doi.org/10.1088/1367-2630/aaa751.
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SOLONTSOV, A. "SPIN FLUCTUATIONS AND ANHARMONICITY IN ITINERANT ELECTRON MAGNETISM." International Journal of Modern Physics B 19, no. 24 (September 30, 2005): 3631–81. http://dx.doi.org/10.1142/s0217979205032462.
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The paper overviews recent investigations of thermodynamics and magnetic dynamics of itinerant electron magnets with strongly coupled (anharmonic) spin fluctuations (SF). A novel classification scheme for SF, dependent on their spatial dispersion and quantum effects is presented, including the generalized Fermi liquid (FL), soft-mode (SM), and localized moments (LM) regimes. It is shown that the conventional SCR theory of Moriya holds only in the weak coupling limit of the SM regime and cannot be applied to real magnets where spin anharmonicity induced by zero-point SF is expected to be strong. To account for the effects of strong spin anharmonicity, a variational SM theory of SF is presented. These effects essentially influence thermodynamics of itinerant magnets and affect the criterion for magnetic instabilities, equations of state, low temperature specific heat, non-FL and quantum critical behavior, etc. Nonlinear magnetic dynamics of itinerant magnets is analyzed based on the phenomenological spin-invariant dynamical equations both in the spin wave and relaxational regimes. Macroscopic magnetic dynamics and different mechanisms of magnon damping in the spin wave regime are shown to be essentially different from the results arising for the Heisenberg magnets. The relaxational regime may be strongly influenced by nonlinear effects of mode-mode couplings. The spectrum of overdamped longitudinal SF is shown to be radically changed due to their scattering by magnons, which may result in a quasielasic peak in the SF spectrum and inelastic SF near the magnon frequencies, depending on nonlinear coupling. The quasielastic SF are suppressed at low temperatures and develop at elevated temperatures, dominating near the Curie point. The results are applied to the magnetoresistive manganites.
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KRÓL, JERZY. "TOPOS THEORY AND SPACETIME STRUCTURE." International Journal of Geometric Methods in Modern Physics 04, no. 02 (March 2007): 297–303. http://dx.doi.org/10.1142/s0219887807002028.
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According to the recently proposed model of spacetime, various difficulties of quantum field theories and semiclassical quantum gravity on curved 4-Minkowski spacetimes gain new formulations, leading to new solutions. The quantum mechanical effects appear naturally when diffeomorphisms are lifted to 2-morphisms between topoi. The functional measures can be well defined. Diffeomorphisms invariance and background independence are approached from the perspective of topoi. In the spacetimes modified at short distances by the internal structure of some topoi, the higher dimensional regions appear and field/strings duality emerges. We show that the model has natural extensions over extremely strong gravity sources in spacetime and shed light on the strong string coupling definition of B-type D-branes.
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Sergi, Alessandro, Antonino Messina, Carmelo M. Vicario, and Gabriella Martino. "A Quantum–Classical Model of Brain Dynamics." Entropy 25, no. 4 (March 30, 2023): 592. http://dx.doi.org/10.3390/e25040592.
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The study of the human psyche has elucidated a bipartite structure of logic reflecting the quantum–classical nature of the world. Accordingly, we posited an approach toward studying the brain by means of the quantum–classical dynamics of a mixed Weyl symbol. The mixed Weyl symbol can be used to describe brain processes at the microscopic level and, when averaged over an appropriate ensemble, can provide a link to the results of measurements made at the meso and macro scale. Within this approach, quantum variables (such as, for example, nuclear and electron spins, dipole momenta of particles or molecules, tunneling degrees of freedom, and so on) can be represented by spinors, whereas the electromagnetic fields and phonon modes can be treated either classically or semi-classically in phase space by also considering quantum zero-point fluctuations. Quantum zero-point effects can be incorporated into numerical simulations by controlling the temperature of each field mode via coupling to a dedicated Nosé–Hoover chain thermostat. The temperature of each thermostat was chosen in order to reproduce quantum statistics in the canonical ensemble. In this first paper, we introduce a general quantum–classical Hamiltonian model that can be tailored to study physical processes at the interface between the quantum and the classical world in the brain. While the approach is discussed in detail, numerical calculations are not reported in the present paper, but they are planned for future work. Our theory of brain dynamics subsumes some compatible aspects of three well-known quantum approaches to brain dynamics, namely the electromagnetic field theory approach, the orchestrated objective reduction theory, and the dissipative quantum model of the brain. All three models are reviewed.
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Alqahtani, Moteb M., Mark S. Everitt, and Barry M. Garraway. "Cavity QED photons for quantum information processing." Journal of Physics B: Atomic, Molecular and Optical Physics 55, no. 18 (August 22, 2022): 184004. http://dx.doi.org/10.1088/1361-6455/ac864f.
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Abstract Based on a cavity QED framework, we theoretically describe a universal set of logic gates which are implemented by passing a multi-level atom initially in its ground state through a multi-mode cavity. The qubits are encoded on the cavity modes and the atom plays the role of an ancilla which will not be entangled with the final result of a gate operation. We apply the multiphoton resonance theory of Shore to develop effective two- and three-level Hamiltonians, so that the proper values for detunings, coupling coefficients, and interaction times for gate operations can be determined. This enables us to examine a faster iSWAP gate than our previous study and to examine numerically the effects of decoherence on both the iSWAP gate and our previously presented Fredkin gate which used the same multi-mode approach. We also present results that show how conditional measurements of the ancilla atom can improve gate fidelities in these cases.
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Fischer, Eric W., Janet Anders, and Peter Saalfrank. "Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry." Journal of Chemical Physics 156, no. 15 (April 21, 2022): 154305. http://dx.doi.org/10.1063/5.0076434.
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It has been experimentally demonstrated that reaction rates for molecules embedded in microfluidic optical cavities are altered when compared to rates observed under “ordinary” reaction conditions. However, precise mechanisms of how strong coupling of an optical cavity mode to molecular vibrations affects the reactivity and how resonance behavior emerges are still under dispute. In the present work, we approach these mechanistic issues from the perspective of a thermal model reaction, the inversion of ammonia along the umbrella mode, in the presence of a single–cavity mode of varying frequency and coupling strength. A topological analysis of the related cavity Born–Oppenheimer potential energy surface in combination with quantum mechanical and transition state theory rate calculations reveals two quantum effects, leading to decelerated reaction rates in qualitative agreement with experiments: the stiffening of quantized modes perpendicular to the reaction path at the transition state, which reduces the number of thermally accessible reaction channels, and the broadening of the barrier region, which attenuates tunneling. We find these two effects to be very robust in a fluctuating environment, causing statistical variations of potential parameters, such as the barrier height. Furthermore, by solving the time-dependent Schrödinger equation in the vibrational strong coupling regime, we identify a resonance behavior, in qualitative agreement with experimental and earlier theoretical work. The latter manifests as reduced reaction probability when the cavity frequency ω c is tuned resonant to a molecular reactant frequency. We find this effect to be based on the dynamical localization of the vibro-polaritonic wavepacket in the reactant well.
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HELD, K., M. ULMKE, and D. VOLLHARDT. "CORRELATED-ELECTRON THEORY OF METAMAGNETISM IN STRONGLY ANISOTROPIC ANTIFERROMAGNETS." Modern Physics Letters B 10, no. 06 (March 10, 1996): 203–10. http://dx.doi.org/10.1142/s0217984996000249.
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The electronic origin of metamagnetism in strongly anisotropic antiferromagnets is examined. To this end the infinite-dimensional Hubbard model with easy axis is investigated both analytically and numerically. At weak coupling a first order transition and at strong coupling a second order phase transition is found. To determine the transition behavior at intermediate coupling Quantum Monte Carlo techniques are used to calculate the field versus temperature phase diagram. The apparent similarities to the phase diagram of FeBr 2 and to mean field results for the Ising model with competing interactions are discussed.
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Reichman, David R., and Eran Rabani. "A self-consistent mode-coupling theory for dynamical correlations in quantum liquids: Application to liquidpara-hydrogen." Journal of Chemical Physics 116, no. 14 (April 8, 2002): 6279–85. http://dx.doi.org/10.1063/1.1458546.
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Dekker, H. "Effective Dipole-Radiation-Field Theory: III. Three-Dimensional Oscillator." International Journal of Modern Physics B 12, no. 09 (April 10, 1998): 965–87. http://dx.doi.org/10.1142/s0217979298000545.
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The novel analysis of the interaction between a harmonically bound, nonrelativistic "isotropic point" charge and the electromagnetic field as presented in paper I [Int. J. Mod. Phys.B8, 2307 (1994)] and II [Int. J. Mod. Phys.B10, 1211 (1996)], is finally extended to the case of a three-dimensional oscillator. The coupling between the electron and the field is treated through all orders beyond the standard dipole model. After a statistical linearization of the highly nonlinear dynamics, the problem is solved exactly in terms of the system's normal modes. The procedure intrinsically involves a generalized mass renormalization. The solution is free of runaway modes. The quantum mechanical ultraviolet divergence known from the standard dipole model is shown to be suppressed by the generalized coupling. Inter alia an effective equation of motion for the charge is derived. It is also shown that the zero-coupling and the infinite-system limits do not commute.
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CAMACHO, A. "ON A QUANTUM EQUIVALENCE PRINCIPLE." Modern Physics Letters A 14, no. 04 (February 10, 1999): 275–88. http://dx.doi.org/10.1142/s0217732399000328.
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The logical consistency of a description of quantum theory in the context of general relativity, which includes minimal coupling principle, is analyzed from the point of view of Feynman's formulation in terms of path integrals. We will argue from this standpoint and use an argument that claims the incompleteness of the general relativistic description of gravitation, which emerges as a consequence of the gravitationally induced phases of the so-called flavor-oscillation clocks, that the postulates of quantum theory are logically incompatible with the usual minimal coupling principle. It will be shown that this inconsistency could emerge from the fact that the required geometrical information to calculate the probability of finding a particle at any point of the respective manifold does not lie in a region with finite volume. Then we put forth a new quantum minimal coupling principle in terms of a restricted path integral, and along the ideas of this model not only the propagator of a free particle is calculated but also the conditions under which we recover Feynman's case for a free particle are deduced. The effect on diatomic interstellar molecules is also calculated. The already existing relation between restricted path integral formalism and decoherence model will enable us to connect the issue of a quantum minimal coupling principle with the collapse of the wave function. From this last remark we will claim that the geometrical structure of the involved manifold acts as, always present, a measuring device on a quantum particle. In other words, in this proposal we connect the issue of a quantum minimal coupling principle with a claim which states that gravity could be one of the physical entities which results in the collapse of the wave function.
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QUÉMERAIS, PASCAL, DAVID K. CAMPBELL, JEAN-LUC RAIMBAULT, and SERGE AUBRY. "QUANTUM TUNNELING EFFECTS IN THE SSH MODEL OF ELECTRON-PHONON INTERACTIONS." International Journal of Modern Physics B 07, no. 25 (November 15, 1993): 4289–303. http://dx.doi.org/10.1142/s021797929300367x.
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We examine the Su-Schrieffer-Heeger (SSH) model of electron-phonon (e-p) interactions as an example of a theory in which commensurate and incommensurate bond-order wave (BOW) ground states are generated (in the quasi-one-dimensional (quasi 1-D) case) by an intersite e-p coupling. We focus primarily on the two-fold commensurate situation, in view of its applicability to the important quasi 1-D conducting polymer trans-polyacetylene (trans — (CH) x). Using a coherent state formalism to model the quantum fluctuation corrections to the adiabatic ground state, we study the quantum tunneling of the SSH “solitons” (viewed as discommensurations created in the two-fold commensurate ground state) and show that, as a result of this tunneling, the energy of the discommensurations can become negative for e-p couplings below a certain critical coupling. We argue that this negative defect energy is an indication of the instability of the underlying adiabatic commensurate BOW state. The critical e-p coupling for this transition depends on the phonon frequency and, for general commensurability, on the commensurability ratio. Thus, in real trans — (CH) x chains where the e-p coupling and the bare phonon frequency are fixed, the transition we describe can occur as a function of doping (which can change the effective commensurability) and may explain the BOW-to-quasimetal transition in doped (CH) x. For quasi-1-D systems, we also estimate the critical e-p couplings for the three-fold commensurate and incommensurate cases. We conclude by mentioning possible extensions of our approach and results to the new family of “fullerenes”, C n(n≥60).
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SISSAKIAN, ALEXEY, IGOR SOLOVTSOV, and OLEG SHEVCHENKO. "VARIATIONAL PERTURBATION THEORY." International Journal of Modern Physics A 09, no. 12 (May 10, 1994): 1929–99. http://dx.doi.org/10.1142/s0217751x94000832.
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A nonperturbative method — variational perturbation theory (VPT) — is discussed. A quantity we are interested in is represented by a series, a finite number of terms of which not only describe the region of small coupling constant but reproduce well the strong coupling limit. The method is formulated only in terms of the Gaussian quadratures, and diagrams of the conventional perturbation theory are used. Its efficiency is demonstrated for the quantum-mechanical anharmonic oscillator. The properties of convergence are studied for series in VPT for the [Formula: see text] model. It is shown that it is possible to choose variational additions such that they lead to convergent series for any values of the coupling constant. Upper and lower estimates for the quantities under investigation are considered. The nonperturbative Gaussian effective potential is derived from a more general approach, VPT. Various versions of the variational procedure are explored and the preference for the anharmonic variational procedure in view of convergence of the obtained series is argued. We investigate the renormalization procedure in the φ4 model in VPT. The nonperturbative β function is derived in the framework of the proposed approach. The obtained result is in agreement with four-loop approximation and has the asymptotic behavior as g3/2 for a large coupling constant. We construct the VPT series for Yang-Mills theory and study its convergence properties. We introduce coupling to spinor fields and demonstrate that they do not influence the VPT series convergence properties.
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Alvarez, Benjamin Louis, and Jérémy Faupin. "Scattering theory for mathematical models of the weak interaction." Reviews in Mathematical Physics 32, no. 01 (August 8, 2019): 2050002. http://dx.doi.org/10.1142/s0129055x20500026.
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We consider mathematical models of the weak decay of the vector bosons [Formula: see text] into leptons. The free quantum field Hamiltonian is perturbed by an interaction term from the standard model of particle physics. After the introduction of high energy and spatial cut-offs, the total quantum Hamiltonian defines a self-adjoint operator on a tensor product of Fock spaces. We study the scattering theory for such models. First, the masses of the neutrinos are supposed to be positive: for all values of the coupling constant, we prove asymptotic completeness of the wave operators. In a second model, neutrinos are treated as massless particles and we consider a simpler interaction Hamiltonian: for small enough values of the coupling constant, we prove again asymptotic completeness, using singular Mourre’s theory, suitable propagation estimates and the conservation of the difference of some number operators.
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DEKKER, H. "EFFECTIVE DIPOLE-RADIATION-FIELD THEORY II: ALL ORDERS BEYOND STANDARD COUPLING." International Journal of Modern Physics B 10, no. 10 (April 30, 1996): 1211–25. http://dx.doi.org/10.1142/s0217979296000453.
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The novel treatment of the interaction between a charged particle and the electromagnetic field, as presented in paper I [H. Dekker, Int. J. Mod. Phys.B8, 1–19 (1994)], is generalized to all orders beyond the standard dipole model. The resulting nonlinear problem is then again statistically linearized and the ensuing dynamics is solved exactly for a harmonically bound nonrelativistic electron. The earlier noted ultraviolet divergence in the system’s quantum mechanics is found to be absent, unless the bare electron mass were exactly zero. Inter alia it is also found that the electron’s generic quantum distribution is Gaussian.
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Prada, Camilo M., and Luis J. Martínez. "Dynamics of Nano-Particles Inside an Optical Cavity in the Quantum Regime." Photonics 9, no. 9 (September 7, 2022): 641. http://dx.doi.org/10.3390/photonics9090641.
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We investigate the optomechanical effect on a single nano-particle inside an optical cavity, by deriving the optical forces acting on the nano-particle by the cavity from quantum theory. We obtain the steady state of the system and found that the force contains three terms associated with the gradient force, the back-action force resulting from the intra-cavity photon energy change, as well as the reactive force associated with the coupling between the external field and the cavity. Moreover, we solve the dynamical system for a dielectric particle in a small mode volume cavity, which is characterized by a quasi-periodic pattern. These results are important for understanding the control of various types of levitated nano-particles through optomechanical coupling.
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Tannukij, Lunchakorn, and Jae-Hyuk Oh. "Partially massless theory as a quantum gravity candidate." International Journal of Modern Physics A 36, no. 17 (June 2, 2021): 2150122. http://dx.doi.org/10.1142/s0217751x21501220.
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We study partially massless gravity theory (PM gravity theory) and suggest an alternative way to add higher order interaction vertices to the theory. Rather than introducing self-interaction vertices of the gravitational fields to the partially massless gravity action, we consider interactions with matter fields, since it is well known that addition of the self-interaction terms necessarily breaks the [Formula: see text] gauge symmetry that PM gravity theory enjoys. For the coupling with matter fields, we consider two different types of interaction vertices. The first one is given by an interaction Lagrangian density, [Formula: see text], where [Formula: see text] is the PM gravity field and [Formula: see text] is the stress-energy tensor of the matter fields. To retain the [Formula: see text] gauge symmetry, the matter fields also transform accordingly and it turns out that the transform must be nonlocal in this case. The second type of interaction is obtained by employing a gauge covariant derivative with the PM gravity field, where the PM gravity fields play a role of a gauge connection canceling the phase shift of the matter fields. We also study the actions and the equations of motion of the partially massless gravity fields. As expected, it shows 4 unitary degrees of freedom — 2 of them are traceless tensor modes and they are light-like fields and the other 2 are transverse vector modes and their dispersion relation changes as background space–time (de Sitter) evolutes. In the very early time, they are light-like but in the very late time, their velocities become a half of speed of light. The vector mode dispersion relation shows momentum-dependent behavior. In fact, the higher (lower) frequency modes show the faster (slower) velocity. We call this effect “conformal (or de Sitter) prism”. We suggest their quantization, compute Hamiltonians to present their exited quanta and construct their free propagators.
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KOJIMA, SHIN-ICHI, NORISUKE SAKAI, and YOSHIAKI TANII. "DILATON GRAVITY COUPLED TO A NONLINEAR SIGMA MODEL IN 2+ε DIMENSIONS." Modern Physics Letters A 10, no. 32 (October 20, 1995): 2391–400. http://dx.doi.org/10.1142/s0217732395002544.
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Quantum theory of dilaton gravity coupled to a nonlinear sigma model with a maximally symmetric target space is studied in 2+ε dimensions. The uv stable fixed point for the curvature of the nonlinear sigma model demands a new fixed point theory for the dilaton coupling function. The fixed point of the dilaton coupling is a saddle point similarly to the previous case of the flat target space.
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Lytaev, Aleksandr A., and Igor Yu Popov. "Simulation of switchers for CNOT-gates based on optical waveguide interaction with coupled mode theory." Zhurnal Srednevolzhskogo Matematicheskogo Obshchestva 23, no. 4 (December 30, 2021): 433–43. http://dx.doi.org/10.15507/2079-6900.23.202104.433-443.
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The paper is devoted to simulation of interactions in the system of two symmetrical slab optical waveguides, that guide exactly two guided modes with the aim to use the directional coupler as a switcher for CNOT gate in the waveguide model of quantum-like computations. The coupling mode theory is used to solve the system of Maxwell equations. The asymptotic analysis is applied to simplify the system of differential equations, so an approximate analytic solution can be found. The solution obtained is used for the quick directional coupler parameters adjusting algorithm, so the power exchange in the system occurs as that of correctly working CNOT-gate switcher. Moreover, the finite difference method is used to solve the stricter system of equations, that additionally takes into account the process of power exchange between different order guided modes, so the computational error of the device can be estimated. It was obtained, that the possible size of the device may not exceed 1 mm in the largest dimension, while the computational error does not exceed 3%.
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Mihaescu, Tatiana, and Aurelian Isar. "Dynamics of Entropy Production Rate in Two Coupled Bosonic Modes Interacting with a Thermal Reservoir." Entropy 24, no. 5 (May 14, 2022): 696. http://dx.doi.org/10.3390/e24050696.
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The Markovian time evolution of the entropy production rate is studied as a measure of irreversibility generated in a bipartite quantum system consisting of two coupled bosonic modes immersed in a common thermal environment. The dynamics of the system is described in the framework of the formalism of the theory of open quantum systems based on completely positive quantum dynamical semigroups, for initial two-mode squeezed thermal states, squeezed vacuum states, thermal states and coherent states. We show that the rate of the entropy production of the initial state and nonequilibrium stationary state, and the time evolution of the rate of entropy production, strongly depend on the parameters of the initial Gaussian state (squeezing parameter and average thermal photon numbers), frequencies of modes, parameters characterising the thermal environment (temperature and dissipation coefficient), and the strength of coupling between the two modes. We also provide a comparison of the behaviour of entropy production rate and Rényi-2 mutual information present in the considered system.
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Krishnaswami, Govind S., and T. R. Vishnu. "Quantum Rajeev–Ranken model as an anharmonic oscillator." Journal of Mathematical Physics 63, no. 3 (March 1, 2022): 032101. http://dx.doi.org/10.1063/5.0079269.
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The Rajeev–Ranken (RR) model is a Hamiltonian system describing screw-type nonlinear waves of wavenumber k in a scalar field theory pseudodual to the 1 + 1D SU(2) principal chiral model. Classically, the RR model is Liouville integrable. Here, we interpret the model as a novel 3D cylindrically symmetric quartic oscillator with an additional rotational energy. The quantum theory has two dimensionless parameters. Upon separating variables in the Schrödinger equation, we find that the radial equation has a four-term recurrence relation. It is of type [0, 1, 16] and lies beyond the ellipsoidal Lamé and Heun equations in Ince’s classification. At strong coupling λ, the energies of highly excited states are shown to depend on the scaling variable λk. The energy spectrum at weak coupling and its dependence on k in a double-scaling strong coupling limit are obtained. The semi-classical Wentzel-Kramers-Brillouin (WKB) quantization condition is expressed in terms of elliptic integrals. Numerical inversion enables us to establish a ( λk)2/3 dispersion relation for highly energetic quantized “screwons” at moderate and strong coupling. We also suggest a mapping between our radial equation and the one of Zinn-Justin and Jentschura that could facilitate a resurgent WKB expansion for energy levels. In another direction, we show that the equations of motion of the RR model can also be viewed as Euler equations for a step-3 nilpotent Lie algebra. We use our canonical quantization to uncover an infinite dimensional reducible unitary representation of this nilpotent algebra, which is then decomposed using its Casimir operators.
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SUN, LEI, JIPING YE, XIANXI DAI, and JIXIN DAI. "AN APPLICATION OF THIRD FORMALISM OF QUANTUM STATISTICS AND A DIAGONALIZATION THEOREM IN ASYMPTOTIC EXACT THEORY OF SUPERCONDUCTIVITY." International Journal of Modern Physics B 19, no. 01n03 (January 30, 2005): 13–15. http://dx.doi.org/10.1142/s0217979205027871.
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Starting from an electron-phonon interacting model, by means of the third formalism of quantum statistics, and with the aid of a diagonalization theorem, the Tc of superconductors from weak coupling to strong coupling cases are studied in a unified way. Our results are comparable with those of McMillan's theory, (which is valid up to the electron-phonon (e-ph) coupling parameter λ~1, a good agreement is shown for λ<1.3) and the Allen and Dynes's theory. Especially our results are very close to those of Hg spectrum with λ~2.0 and some strong coupling compounds. The theory is exact in the thermodynamic limit, without introducing variation method, the compensation of the dangerous diagrams in finite order in perturbation theory, abnormal green's function etc.
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DEKKER, H. "EFFECTIVE DIPOLE-RADIATION-FIELD THEORY I: ONE-DIMENSIONAL OSCILLATOR BEYOND STANDARD COUPLING." International Journal of Modern Physics B 08, no. 17 (July 30, 1994): 2307–25. http://dx.doi.org/10.1142/s0217979294000944.
Full textAbstract:
A novel generalization is given of the standard dipole interaction between a charged particle and the electromagnetic field in the radiation gauge. The resulting nonlinear interaction problem is statistically linearized. The ensuing dynamics is solved exactly for a harmonically bound nonrelativistic electron in a finite region of three-dimensional space. The solution involves a generalized renormalization procedure and is free of runaway modes. The theory is particularly suited for a self-consistent treatment of the system's quantum mechanics. As a consequence of the generalized coupling an earlier noted ultraviolet quantum mechanical divergence is absent.
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ZHOU, QING-CHUN, and SHI NING ZHU. "ATOMIC DIPOLE SQUEEZING IN THE DEGENERATE Λ QUANTUM BEAT THREE-LEVEL SYSTEM." International Journal of Modern Physics B 20, no. 20 (August 10, 2006): 2889–98. http://dx.doi.org/10.1142/s0217979206034911.
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By using the full quantum theory, we investigate the time evolution of the atomic dipole squeezing parameters of a Λ-type three-level atom interacting with a single-mode coherent optical field, and study the influence of the initial coherent-field intensity, the initial atomic coherence, the initial populations and energy splitting of the two lower atomic levels on the atomic dipole squeezing. The influence of a classical external driving field coupling to the atom on the atomic dipole squeezing is also explored at the end of the paper.
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Teruya, Andre S. W., Breno Raphaldini, Victor C. Mayta, Carlos F. M. Raupp, and Pedro L. da Silva Dias. "Wavenumber-Frequency Spectra of Normal Mode Function Decomposed Atmospheric Data: Departures from the Dry Linear Theory." Atmosphere 14, no. 4 (March 24, 2023): 622. http://dx.doi.org/10.3390/atmos14040622.
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The study of tropical tropospheric disturbances has led to important challenges from both observational and theoretical points of view. In particular, the observed wavenumber-frequency spectrum of tropical oscillations has helped bridge the gap between observations and the linear theory of equatorial waves. In this study, we obtained a similar wavenumber-frequency spectrum for each equatorial wave type by performing a normal mode function (NMF) decomposition of global Era–Interim reanalysis data. The NMF basis used here is provided by the eigensolutions of the primitive equations in spherical coordinates as linearized around a resting background state. In this methodology, the global multi-level horizontal velocity and geopotential height fields are projected onto the normal mode functions, characterized by a vertical mode, a zonal wavenumber, a meridional quantum index, and a mode type, namely, Rossby, Kelvin, mixed Rossby-gravity, and westward/eastward propagating inertio-gravity modes. The horizontal velocity and geopotential height fields associated with each mode type are then reconstructed in the physical space, as well as their corresponding filtered versions defined according to the vertical mode classes that exhibit barotropic and baroclinic structures within the troposphere. The results reveal expected structures, such as the dominant global-scale Rossby and Kelvin waves constituting the intraseasonal frequency associated with the Madden–Julian Oscillation. On the other hand, a number of unexpected features, such as eastward propagating westward inertio-gravity waves, are revealed by our observed 200 hPa zonal wind spectrum. Among all possible nonlinear processes, we focus on the analysis of the interaction between Kelvin and westward inertio-gravity waves, providing evidence for their coupling. Apart from the nonlinearity, we discuss the potential roles of a vertically/meridionally varying background state as well as the coupling with moist convection in explaining the departures of the observed spectra from the corresponding linear equatorial wave theory.
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Niu, Ming-Li, Yue-Ming Wang, and Zhi-Jian Li. "Estimation of light-matter coupling constant under dispersive interaction based on quantum Fisher information." Acta Physica Sinica 71, no. 9 (2022): 090601. http://dx.doi.org/10.7498/aps.71.20212029.
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Quantum parameter estimation is one of the most important applications in quantum metrology. The basic theory of quantum parameter estimation－quantum Cramer-Rao bound－shows that the precision limit of quantum parameter estimation is directly related to quantum Fisher information. Therefore quantum Fisher information is extremely important in the quantum parameter estimation. In this paper we use quantum parameter estimation theory to estimate the coupling constant of the Jaynes-Cummings model with large detuning. The initial probing state is the direct product state of qubit and radiation field in which Fock state, thermal state and coherent state are taken into account respectively. We calculate the quantum Fisher information of the hybrid system as well as qubit and radiation field for each probing state after the parameter evolution under the Hamiltonian of the Jaynes-Cummings model with large detuning. The results show that the quantum Fisher information increases monotonically with the average photon number increasing. The optimal detection state is that when the qubit system is in the equal weight superposition of the ground and the excited state, at this time the quantum Fisher information always reaches a maximum value, When the radiation field of probing state is Fock state or the thermal state, the information about the estimated parameter is included only in the qubit. The estimation accuracy of the coupling constant with thermal state or coherent state is higher than that with Fock state.
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Freindorf, Marek, Margaret McCutcheon, Nassim Beiranvand, and Elfi Kraka. "Dihydrogen Bonding—Seen through the Eyes of Vibrational Spectroscopy." Molecules 28, no. 1 (December 28, 2022): 263. http://dx.doi.org/10.3390/molecules28010263.
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In this work, we analyzed five groups of different dihydrogen bonding interactions and hydrogen clusters with an H3+ kernel utilizing the local vibrational mode theory, developed by our group, complemented with the Quantum Theory of Atoms–in–Molecules analysis to assess the strength and nature of the dihydrogen bonds in these systems. We could show that the intrinsic strength of the dihydrogen bonds investigated is primarily related to the protonic bond as opposed to the hydridic bond; thus, this should be the region of focus when designing dihydrogen bonded complexes with a particular strength. We could also show that the popular discussion of the blue/red shifts of dihydrogen bonding based on the normal mode frequencies is hampered from mode–mode coupling and that a blue/red shift discussion based on local mode frequencies is more meaningful. Based on the bond analysis of the H3+(H2)n systems, we conclude that the bond strength in these crystal–like structures makes them interesting for potential hydrogen storage applications.
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Singh, Tejinder P. "Gravitation, and quantum theory, as emergent phenomena." Journal of Physics: Conference Series 2533, no. 1 (June 1, 2023): 012013. http://dx.doi.org/10.1088/1742-6596/2533/1/012013.
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Abstract There must exist a reformulation of quantum field theory, even at low energies, which does not depend on classical time. The octonionic theory proposes such a reformulation, leading to a pre-quantum pre-spacetime theory. The ingredients for constructing such a theory, which is also a unification of the standard model with gravitation, are : (i) the pre-quantum theory of trace dynamics – a matrix-valued Lagrangian dynamics, (ii) the spectral action principle of non-commutative geometry, (iii) the number system known as the octonions, for constructing a non-commutative manifold and for defining elementary particles via Clifford algebras, (iv) a Lagrangian with E 8 × E 8 symmetry. The split bioctonions define a sixteen dimensional space (with left-right symmetry) whose geometry (evolving in Connes time) relates to the four known fundamental forces, while predicting two new forces, SU(3) grav and U(1) grav . This latter interaction is possibly the theoretical origin of MOND. Coupling constants of the standard model result from left-right symmetry breaking, and their values are theoretically determined by the characteristic equation of the exceptional Jordan algebra of the octonions. The quantum-to-classical transition, precipitated by the entanglement of a critical number of fermions, is responsible for the emergence of classical spacetime, and also for the familiar formulation of quantum theory on a spacetime background.
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CHENAGHLOU, A. "SECOND ORDER QUANTUM CORRECTIONS TO THE CLASSICAL REFLECTION FACTOR OF THE SINH–GORDON MODEL." International Journal of Modern Physics A 16, no. 28 (November 10, 2001): 4613–36. http://dx.doi.org/10.1142/s0217751x01005572.
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The sinh–Gordon model on a half-line with integrable boundary conditions is considered in low order perturbation theory developed in affine Toda field theory. The quantum corrections to the classical reflection factor of the model are studied up to the second order in the difference of the two boundary parameters and to one loop order in the bulk coupling. It is noticed that the general form of the second order quantum corrections are consistent with Ghoshal's formula.
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SI, QIMIAO, J. LLEWEILUN SMITH, and KEVIN INGERSENT. "QUANTUM CRITICAL BEHAVIOR IN KONDO SYSTEMS." International Journal of Modern Physics B 13, no. 18 (July 20, 1999): 2331–42. http://dx.doi.org/10.1142/s0217979299002435.
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This article briefly reviews three topics related to the quantum critical behavior of certain heavy-fermion systems. First, we summarize an extended dynamical mean-field theory for the Kondo lattice, which treats on an equal footing the quantum fluctuations associated with the Kondo and RKKY couplings. The resulting dynamical mean-field equations describe a Kondo impurity model with an additional coupling to vector bosons. Two types of quantum phase transition appear to be possible within this approach — the first a conventional spin-density-wave transition, the second driven by local physics. For the second type of transition to be realized, the effective impurity model must have a quantum critical point exhibiting an anomalous local spin susceptibility. In the second part of the paper, such a critical point is shown to occur in two variants of the Kondo impurity problem. Finally, we propose an operational test for the existence of quantum critical behavior driven by local physics. Neutron scattering results suggest that CeCu 6-x Au x passes this test.
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Horing, Norman J. Morgenstern. "Aspects of the theory of graphene." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, no. 1932 (December 13, 2010): 5525–56. http://dx.doi.org/10.1098/rsta.2010.0242.
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Following a brief review of the device-friendly features of graphene, recent work on its Green’s functions with and without a normal magnetic field are discussed, for an infinite graphene sheet and also for a quantum dot, with analyses of the Landau-quantized energy spectra of the sheet and dot. The random phase approximation dielectric response of graphene is reviewed and discussed in connection with the van der Waals interactions of a graphene sheet with atoms/molecules and with a second graphene sheet in a double layer. Energy-loss spectroscopy for a graphene sheet subject to both parallel and perpendicular particle probes of its dynamic, non-local response properties are also treated. Furthermore, we discuss recent work on the coupling of a graphene plasmon and a surface plasmon, yielding a collective plasma mode that is linear in wavenumber. Finally, we discuss the unusual aspects of graphene conduction and recent work on diffusive charge transport in graphene, in both the DC and AC regimes.
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LIZZI, FEDELE, NICK E. MAVROMATOS, and RICHARD J. SZABO. "MATRIX σ-MODELS FOR MULTI D-BRANE DYNAMICS." Modern Physics Letters A 13, no. 11 (April 10, 1998): 829–42. http://dx.doi.org/10.1142/s0217732398000905.
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We describe a dynamical worldsheet origin for the Lagrangian describing the low-energy dynamics of a system of parallel D-branes. We show how matrix-valued collective coordinate fields for the D-branes naturally arise as couplings of a worldsheet σ-model, and that the quantum dynamics require that these couplings be mutually noncommutative. We show that the low-energy effective action for the σ-model couplings describes the propagation of an open string in the background of the multiple D-brane configuration, in which all string interactions between the constituent branes are integrated out and the genus expansion is taken into account, with a matrix-valued coupling. The effective field theory is governed by the non-Abelian Born–Infeld target space action which leads to the standard one for D-brane field theory.
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Geddes, A. J., S. A. Morgan, and D. A. W. Hutchinson. "Novel dynamical resonances in finite-temperature Bose–Einstein condensates." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, no. 2063 (September 15, 2005): 3647–58. http://dx.doi.org/10.1098/rspa.2005.1543.
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We describe a variety of intriguing mode-coupling effects which can occur in a confined Bose–Einstein condensed system at finite temperature. These arise from strong interactions between a condensate fluctuation and resonances of the thermal cloud yielding strongly nonlinear behaviour. We show how these processes can be affected by altering the aspect ratio of the trap, thereby changing the relevant mode-matching conditions. We illustrate how direct driving of the thermal cloud can lead to significant shifts in the excitation spectrum for a number of modes and provide further experimental scenarios in which the dramatic behaviour observed for the m =0 mode at JILA can be repeated. Our theoretical description is based on a successful second-order finite-temperature quantum field theory which includes the full coupled dynamics of the condensate and thermal cloud and all relevant finite-size effects.