Quantum Initiation of Collective Radiation

Vadim N. Tsytovich

Victor Nikolaevich Popov, Vladimir Sergeevich Yarunin

Salman Mokhlespour, Jos E. M. Haverkort, Gregory Ya. Slepyan +2 more

We investigate the collective spontaneous emission in a system of two identical quantum dots (QDs) strongly coupled through the dipole-dipole ($d\ensuremath{-}d$) interaction. The QDs are modeled as two-level quantum objects, while the $d\ensuremath{-}d$ interaction is described as the exchange of a virtual photon through the photonic reservoir. The master equation approach is used in the analysis. The main attention is focused on antenna characteristics of the two-QD system---the radiation intensity dependence on the meridian and azimuthal angles of observation. We show that the radiation pattern of such a system is nonstationary and its temporal behavior depends on the initial quantum state. In particular, for entangled initial states the radiative pattern exhibits oscillations on the frequency which corresponds to the $d\ensuremath{-}d$ interaction energy. We also analyze spectral properties of the directional diagram. The comparison of radiation patterns is carried out for two QDs and two classical dipoles. The concept of quantum nanoantenna is proposed based on collective spontaneous emission in QD ensembles.

Dipankar Bhattacharyya, Jyotirmoy Guha

Helen S. Freedhoff

In this paper, we study the collective single-quantum excitations of a ring of N identical molecular units, of arbitrary radius R relative to the radiation wavelength λ. We first calculate the single-quantum eigenstates of the system for N=2,...,6 and N large, their energies and their lifetimes due to interaction with the radiation field. For large N, we study the collective emission by the ring as a function of direction, comparing the pattern with that created by a collectively excited linear chain of molecular units. Finally, we calculate the emission spectrum of the ring for arbitrary initial excitation, and the spectrum of the radiation absorbed by the ring from an external electromagnetic field.

R. N. Shakhmuratov, Farit G. Vagizov, J. Odeurs +1 more

Single $\ensuremath{\gamma}$ photon propagation in a dense absorptive medium with two widely spaced resonances is experimentally studied. After an initial fast decay, a revival of the photon amplitude in the form of a bump, exceeding the probability amplitude of the incident photon, is observed. The irradiation time of this bump delays approximately by the lifetime of the excited nuclei in the absorber. This effect is explained by the interference of the incoming radiation with the collectively scattered radiation, the phase of which is modulated with the frequency of the doublet splitting. Initially, the destructive interference changes to a constructive one, distinguishing the storage and retrieval stages of the photon propagation in a dense medium, i.e., the collective absorption and collective re-emission processes.