Quantum interference due to energy shifts and its effect on spontaneous emission (original) (raw)
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Quantum interference in optical fields and atomic radiation
Journal of Modern Optics, 2002
We discuss the connection between quantum interference effects in optical beams and radiation fields emitted from atomic systems. We illustrate this connection by a study of the first-and second-order correlation functions of optical fields and atomic dipole moments. We explore the role of correlations between the emitting systems and present examples of practical methods to implement two systems with non-orthogonal dipole moments. We also derive general conditions for quantum interference in a two-atom system and for a control of spontaneous emission. The relation between population trapping and dark states is also discussed. Moreover, we present quantum dressed-atom models of cancellation of spontaneous emission, amplification on dark transitions, fluorescence quenching and coherent population trapping.
Time evolution, Lamb shift, and emission spectra of spontaneous emission of two identical atoms
Physical Review A, 2010
A unitary transformation method is used to investigate the dynamic evolution of two multilevel atoms, in the basis of symmetric and antisymmetric states, with one atom being initially prepared in the first excited state and the other in the ground state. The unitary transformation guarantees that our calculations are based on the ground state of the atom-field system and the self-energy is subtracted at the beginning. The total Lamb shifts of the symmetric and antisymmetric states are divided into transformed shift and dynamic shift. The transformed shift is due to emitting and reabsorbing of virtual photons, by a single atom (nondynamic single atomic shift) and between the two atoms (quasi-static shift). The dynamic shift is due to the emitting and reabsorbing of real photons, by a single atom (dynamic single atomic shift) and between the two atoms (dynamic interatomic shift). The emitting and reabsorbing of virtual and real photons between the two atoms result in the interatomic shift, which does not exist for the one-atom case. The spectra at the long-time limit are calculated. If the distance between the two atoms is shorter than or comparable to the wavelength, the strong coupling between the two atoms splits the spectrum into two peaks, one from the symmetric state and the other from the antisymmetric state. The origin of the red or blue shifts for the symmetric and antisymmetric states mainly lies in the negative or positive interaction energy between the two atoms. In the investigation of the short time evolution, we find the modification of the effective density of states by the interaction between two atoms can modulate the quantum Zeno and quantum anti-Zeno effects in the decays of the symmetric and antisymmetric states.
Interference-induced splitting of resonances in spontaneous emission
Physical Review A, 2008
We study the resonance fluorescence from a coherently driven four-level atom in the Y-type configuration. The effects of quantum interference induced by spontaneous emission on the fluorescence properties of the atom are investigated. It is found that the quantum interference resulting from cascade emission decays of the atom leads to a splitting of resonances in the excited level populations calculated as a function of light detuning. For some parameters, interference assisted enhancement of inner sidebands and narrowing of central peaks may also occur in the fluorescence spectrum. We present a physical understanding of our numerical results using the dressed state description of the atom-light interaction.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2007
The effect of a modified reservoir on the nature of the quantum interference in the spontaneous emission of a driven double V-type four-level atom has been investigated. In the model used, the double V-type transitions of a driven atom interact respectively with a free vacuum reservoir and a modified reservoir, leading to the two possible types of quantum interference. The results show that the construction or the destruction of interference in the free vacuum reservoir depends on the type of the modified reservoir and the absence or the presence of interference in the modified reservoir. More interesting, it is shown that based on the presence or the absence of interference in the modified reservoir, interference in the free vacuum reservoir can be constructive or destructive if the modified reservoir is of the type of the free vacuum reservoir. On the other hand, the interference in the free vacuum reservoir is constructive, regardless of the presence or the absence of interference in the modified reservoir, if the modified reservoir is of the type of the photonic band gap. This case, therefore, can be used to control effectively the spontaneous emission and absorption spectra.
Quantum interference in the fluorescence of a molecular system
Physical Review A, 2000
It has been observed experimentally [H.R. Xia, C.Y. Ye, and S.Y. Zhu, Phys. Rev. Lett. 77, 1032 (1996)] that quantum interference between two molecular transitions can lead to a suppression or enhancement of spontaneous emission. This is manifested in the fluorescent intensity as a function of the detuning of the driving field from the two-photon resonance condition. Here we present a theory which explains the observed variation of the number of peaks with the mutual polarization of the molecular transition dipole moments. Using master equation techniques we calculate analytically as well as numerically the steady-state fluorescence, and find that the number of peaks depends on the excitation process. If the molecule is driven to the upper levels by a two-photon process, the fluorescent intensity consists of two peaks regardless of the mutual polarization of the transition dipole moments. If the excitation process is composed of both a two-step one-photon process and a one-step, two-photon process, then there are two peaks on transitions with parallel dipole moments and three peaks on transitions with antiparallel dipole moments. This latter case is in excellent agreement with the experiment.
Quantum interference effects in a Λ-type atom interacting with two short laser pulse trains
The European Physical Journal D, 2014
We study the quantum interference between the excitation pathways in a three-level Λ-type atom interacting with two short laser pulse trains under the conditions of electromagnetically induced transparency. The probability amplitude equations which describe the interaction of a three-level Λ-type atom with two laser pulse trains are numerically solved. We derive analytical expressions for the population of the upper excited state for resonant laser pulse trains with a rectangular temporal profile. By varying the parameters of the laser pulse trains such as area of a single pulse, detuning, repetition period, and number of individual pulses, we analyze the quantum interference between the excitation pathways in terms of the upper excited state population.
Interference of Spontaneously Emitted Photons
Fortschritte der Physik, 2002
We discuss an experimental setup where two laser-driven atoms spontaneously emit photons and every photon causes a "click" at a point on a screen. By deriving the probability density for an emission into a certain direction from basic quantum mechanical principles we predict a spatial interference pattern. Similarities and differences with the classical double-slit experiment are discussed.
Interference of spontaneous emission of light from two solid-state atomic ensembles
New Journal of Physics, 2007
We report an interference experiment of spontaneous emission of light from two distant solid-state ensembles of atoms that are coherently excited by a short laser pulse. The ensembles are Erbium ions doped into two LiNbO 3 crystals with channel waveguides, which are placed in the two arms of a Mach-Zehnder interferometer. The light that is spontaneously emitted after the excitation pulse shows first-order interference. By a strong collective enhancement of the emission, the atoms behave as ideal two-level quantum systems and no which-path information is left in the atomic ensembles after emission of a photon. This results in a high fringe visibility of 95%, which implies that the observed spontaneous emission is highly coherent.
Introduction to quantum optics
In this notes we explore several fundamental issues related to the interaction between an atom and an electromagnetic field. We show how the spontaneous decay naturally arise in the second quantization framework. At a later stage we include the effect of a classical monochromatic field showing how the population of the atom accomplish the so called Rabi oscillation. Finally we consider the spectra of resonance fluorescence and show the Mollow peaks in the spectra.
Observation of spontaneous quantum fluctuations in photon absorption by atoms
The European Physical Journal D, 2013
ABSTRACT Fluctuations in light absorption by atoms are observed by applying laser light on rubidium atoms and measuring the transmitted light intensity fluctuations. These fluctuations are spontaneous noise, which are generic to photon atom interactions. By making use of the sub-shot noise random signal detection technology, we have measured the spectra at sub-shot noise levels to reveal their rich nature, which had previously been unobserved. The effects of atoms transiting the laser beam, Rabi flopping in the optical transitions and Larmor precession of the magnetic moment are observed in the spectra. The properties of the fluctuations reflect not only the quantum behavior of atoms, but also that of light.