Suc-Kyoung Hong

The quantum under-, critical- and over-damped driven harmonic oscillators

The cases of under-, critical- and over-damping are treated for the quantum driven harmonic oscillator. Following a survey of the classical version, the quantum invariant operator for each case is constructed and their eigenvalues are evaluated. Using these eigenvalues and the Schrodinger equations, the wavefunctions are obtained for each case. From formal path integral theory, their propagators are evaluated and are checked with those obtained by the closed property formed by the complete set of wavefunctions.

Excitons and polaritons in quasi-molecular eigenbasis of the excitation hopping system interacting with a photon field

We report studies of excitons and polaritons in the quasi-molecular eigenbasis of a nano-aggregate, in the model of excitation transfer with, or without, photon-exciton coupling. We evaluate the effective interaction between quasi-molecular subsystems in quasi-molecular eigenbasis representation, with its eigenenergies and eigenstates. From the analysis of the effective interaction Hamiltonian in the quasi-molecular eigenbasis representation, we see that the effective interaction between subsystems in quasi-molecular eigenbasis representation gives fertile points of view to understand the given system, and the dynamics of excitons and polaritons becomes simpler to understand, or to deal with, depending on the division of the whole system into specified subsystems.

Excitonic quantum interference in a quantum dot chain with rings

We demonstrate excitonic quantum interference in a closely spaced quantum dot chain with nanorings. In the resonant dipole-dipole interaction model with direct diagonalization method, we have found a peculiar feature that the excitation of specified quantum dots in the chain is completely inhibited, depending on the orientational configuration of the transition dipole moments and specified initial preparation of the excitation. In practice, these excited states facilitating quantum interference can provide a conceptual basis for quantum interference devices of excitonic hopping.

Cooperative Spontaneous Emission from Nanocrystals to a Surface Plasmon Polariton in a Metallic Nanowire

We analyze the cooperative spontaneous emission of optically excited nanocrystals into surface plasmon polaritons propagating on the surface of a cylindrical metallic nanowire. The spontaneous emission probability of the nanocrystals is obtained by perturbative expansions with and without dipole-dipole interaction among nanocrystals in order to see the cooperative effects. The spontaneous emission probability depends on the radial and axial distributions, as well as on the dipolar orientation of nanocrystals. It is shown that the spontaneous emission probability is strongly influenced by dipole-dipole interaction, axial distribution, and dipolar orientation of nanocrystals for closely spaced nanocrystals.

Analysis of Mach-Zehnder interferometer with two degenerated optical parametric amplifiers

Abstract We have analyzed a Mach-Zehnder interferometer with one or two degenerated parametric amplifiers, one for each arm. The photocurrent, its variance, and the phase fluctuation are obtained. The photon statistics of the entangled state exiting the interferometer is described by means of the Mandel Q parameter.

Phase correlation of ensemble of quantum emitters and timed Dicke state

We study the phase-correlated state which is introduced by the instantaneous excitation of an ensemble of identical two-level quantum emitters and its relation with the Dicke states. Under weak coupling regime, the time evolution of the phase-correlated system of the emitters is also derived to see the characteristics of the collective spontaneous emission of the emitters. It is found that the effective coupling of the ensemble in the phase-correlated state with the emitted field is directly determined by the collective phase of the system. Hence, the collective phase is considered for several specified distributions in brief.

Cooperative spontaneous emission of nano-emitters with inter-emitter coupling in a leaky microcavity

We study the spontaneous emission from a few two-level nano-emitters placed in a leaky microcavity with Lorentzian spectral density near a critically damped regime. Collective features of the spontaneous emission are investigated by numerical analysis of the excitation dynamics when initially one nano-emitter is totally excited but we do not know which one. The results show that there are three decay rates in the excitation dynamics, two for simple exponential decays and one for damped oscillatory decay. The excitation dynamics is found to critically depend on the regime of the system. It is shown that the spontaneous emission is enhanced or suppressed depending on whether the system is in the underdamped or overdamped regime, respectively. On the other hand, the cooperative spontaneous emission is suppressed in the underdamped while it is enhanced in the overdamped regime. Furthermore, the effect of the direct inter-emitter coupling on the breaking of the cooperativeness of the spontaneous emission is shown as well.

Phase properties of superposed squeezed states

The phase properties of the superposed squeezed states are studied. The superposed squeezed states are obtained by inserting two squeezers in a Mach-Zehnder interferometer one for each arm. The visibility of the states as a measure of the coherence of the generated photons in the nonlinear interferometer is analyzed. And the mean-square phase fluctuations are also considered to analyze the phase properties of the superposed squeezed states. The quantities are obtained as a function of gain and the input phase, when the amplified input is a coherent state, a number state, a thermal state, a displaced number state, or a coherent thermal state.

COHERENCE AND COMPLEMENTARITY IN A MACH-ZEHNDER INTERFEROMETER WITH TWO DOPAS

The characteristics of the quantum optical complementarity principle and the coherence of the photons generated in a Mach-Zehnder interferometer with two degenerate optical parametric amplifiers are analysed. The photon statistics and the phase fluctuation of the combined states are analysed in a homodyning Mach-Zehnder interferometer with two degenerate optical parametric amplifiers. By analysing the photon statistics, the mean-square phase fluctuation and the fringe visibility, the complementarity is considered as a function of the gain and input phase, when the amplified input is a coherent state containing one photon, on average. It is also considered when the input is a number state with one photon.