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Titus Sandu - One of the best experts on this subject based on the ideXlab platform.

  • Dynamics of a Quantum Oscillator strongly and off-resonantly coupled with a two-level system
    Physics Letters A, 2009
    Co-Authors: Titus Sandu
    Abstract:

    Beyond the rotating-wave approximation, the dynamics of a Quantum Oscillator interacting strongly and off-resonantly with a two-level system exhibit beatings, whose period equals the revival time of the two-level system. On a longer time scale, the Quantum Oscillator shows collapses, revivals and fractional revivals, which are encountered in Oscillator observables like the mean number of Oscillator quanta and in the two-level inversion population. Also the scattered Oscillator field shows doublets with symmetrically displaced peaks.

  • Dynamics of a two-level system coupled with a Quantum Oscillator: The very strong coupling limit
    Physical Review B, 2006
    Co-Authors: Titus Sandu
    Abstract:

    The time-dependent behavior of a two-level system interacting with a Quantum Oscillator system is analyzed in the case of a coupling larger than both the energy separation between the two levels and the energy of Quantum Oscillator ($\Omega < \omega < \lambda $, where $\Omega $ is the frequency of the transition between the two levels, $\omega $ is the frequency of the Oscillator, and $\lambda $ is the coupling between the two-level system and the Oscillator). Our calculations show that the amplitude of the expectation value of the Oscillator coordinate decreases as the two-level system undergoes the transition from one level to the other, while the transfer probability between the levels is staircase-like. This behavior is explained by the interplay between the adiabatic and the non-adiabatic regimes encountered during the dynamics with the system acting as a Quantum counterpart of the Landau-Zener model. The transition between the two levels occurs as long as the expectation value of the Oscillator coordinate is driven close to zero. On the contrary, if the initial conditions are set such that the expectation values of the Oscillator coordinate are far from zero, the system will remain locked on one level.

D. P. L. Castrigiano - One of the best experts on this subject based on the ideXlab platform.

  • Effective density of states for a Quantum Oscillator coupled to a photon field
    Communications in Mathematical Physics, 2010
    Co-Authors: Volker Betz, D. P. L. Castrigiano
    Abstract:

    We give an explicit formula for the effective partition function of a harmonically bound particle minimally coupled to a photon field in the dipole approximation. The effective partition function is shown to be the Laplace transform of a positive Borel measure, the effective measure of states. The absolutely continuous part of the latter allows for an analytic continuation, the singularities of which give rise to resonances. We give the precise location of these singularities, and show that they are well approximated by of first order poles with residues equal the multiplicities of the corresponding eigenspaces of the uncoupled Quantum Oscillator. Thus we obtain a complete analytic description of the natural line spectrum of the charged Oscillator.

  • Natural spectrum of a charged Quantum Oscillator
    Il Nuovo Cimento B Series 11, 1993
    Co-Authors: D. P. L. Castrigiano, N. Kokiantonis, H. Stierstorfer
    Abstract:

    The spectrum of a harmonically bounded electron is investigated, which couples to its own radiation field. For the coupling, an appropriately simplified version of the minimal electromagnetic coupling is used. This system is treated exactly by path integration. By integrating out the field variables, a reduced system is obtained, which depends only on the electron variables. It is regarded as a model for thenatural charged Quantum Oscillator. The interaction of the Oscillator with the field is condensed in a non-local potential for the electron, and the present investigations concern the modifications of the Oscillator spectrum due to this additional potential. An analytic formula for the whole spectrum is obtained as the inverse Laplace transform of the partition function. The properties of the spectrum are studied in detail and are related to the radiative behaviour of the system. In particular, it is shown that the shapes of the broadenend spectral lines differ slightly from Lorentz profiles proving that the spontaneous decays of the states are not purely exponential. The widths and shifts of the lines are computed. It is mentioned that the model is rather universal so that the results apply, in principle, to other dissipative systems.

Garnett W Bryant - One of the best experts on this subject based on the ideXlab platform.

  • strongly coupled Quantum dot metal nanoparticle systems exciton induced transparency discontinuous response and suppression as driven Quantum Oscillator effects
    Physical Review B, 2010
    Co-Authors: Ryan D Artuso, Garnett W Bryant
    Abstract:

    We probe the transition to bistability that exists in a hybrid metal nanoparticle and semiconductor Quantum dot (SQD) system when they are strongly coupled. In particular, we see a discontinuous jump in the response of the system (in both the diagonal and off-diagonal density-matrix elements) and a SQD response that is highly suppressed above resonance in this transition region. This discontinuous response and suppression arise because the SQD acts as a driven (Quantum) Oscillator. The phase change at resonance drastically alters the hybrid response when crossing the resonance. The study of this transition region, the discontinuity, and the suppression phenomena provides different insights into understanding this system, predicts a more complicated behavior than previously thought and corrects earlier work where the transition region was absent.

R.f. O'connell - One of the best experts on this subject based on the ideXlab platform.

  • Entropy of a Quantum Oscillator coupled to a Heat Bath and implications for Quantum Thermodynamics
    Physica E: Low-dimensional Systems and Nanostructures, 2005
    Co-Authors: G W Ford, R.f. O'connell
    Abstract:

    The free energy of a Quantum Oscillator in an arbitrary heat bath at temperature T is given by a ”remarkable formula” which involves only a single integral. This leads to a corresponding simple result for the entropy. The low temperature limit is examined in detail and explicit results are obtained both for the case of an Ohmic heat bath and a radiation heat bath. More general heat bath models are also examined. In all cases it is found that the entropy vanishes at zero temperature, in conformity with the third law of thermodynamics (Nernst’s theorem).

  • Frequency Shifts and Master Equations for a Quantum Oscillator Coupled to a Reservoir
    Annals of Physics, 1998
    Co-Authors: G W Ford, R.f. O'connell
    Abstract:

    Abstract For a Quantum Oscillator coupled to a reservoir, master equations obtained under the assumptions of weak coupling and use of a rotating-wave Hamiltonian (RWA) are known to give incorrect frequency shifts. Here, we show that a calculation which does not invoke the RWA gives results for the frequency shifts, which agree with exact results for Lamb-type (temperature T =0) shifts. However, for non-zero T , we point out that, in general, corresponding energy and free energy shifts for the system require exact treatments since off-resonant contributions (which are automatically excluded in weak coupling calculations) are important in the case of super-Ohmic reservoirs.

A. Mirzac - One of the best experts on this subject based on the ideXlab platform.

  • Steady-State Behaviors of a Quantum Oscillator Coupled with a Three-Level Emitter
    4th International Conference on Nanotechnologies and Biomedical Engineering, 2020
    Co-Authors: A. Mirzac, M. A. Macovei
    Abstract:

    A laser-pumped three-level Λ-type system the upper state of which is being coupled with a Quantum Oscillator characterized by a single quantized leaking mode has been investigated. Two distinct situations leading to lasing effects of the Quantum Oscillator’s degrees of freedom have been identified and the mechanisms behind them have been described. Particularly, the interplay between single- or two-quanta processes accompanied by Quantum interference effects among the induced emitter’s dressed-states responsible for flexible lasing effects has been proved, respectively.

  • Dynamics of a Quantum Oscillator coupled with a three-level Λ-type emitter
    Journal of the Optical Society of America B, 2019
    Co-Authors: A. Mirzac, Mihai A. Macovei
    Abstract:

    We investigate the Quantum dynamics of a Quantum Oscillator coupled with the most upper state of a three-level Λ-type system. The two transitions of the three-level emitter, possessing orthogonal dipole moments, are coherently pumped with a single or two electromagnetic field sources, respectively. We have found ranges for flexible lasing or cooling phenomena referring to the Quantum Oscillator’s degrees of freedom. This is due to asymmetrical decay rates and Quantum interference effects leading to population transfer among the relevant dressed states of the emitter’s subsystem with which the Quantum Oscillator is coupled. As an appropriate system can be considered a nanomechanical resonator coupled with the most excited state of the three-level emitter fixed on it. Alternatively, if the upper state of the Λ-type system possesses a permanent dipole then it can couple with a cavity electromagnetic field mode which can be in the terahertz domain, for instance. In the latter case, we demonstrate an effective electromagnetic field source of terahertz photons.