Quantum statistical theory of coherent emission from a system of multi-level atoms

Francesco Giorgino, P. Zahálka, Lennart Jehle +4 more

Resonance fluorescence of natural or artificial atoms constitutes a prime method for generating non-classical light. While most efforts have focused on producing single photons, multi-photon emission is unavoidably present in the resonant driving of an atom. Here, we study the extent to which these processes occur: we quantify the multi-photon emission statistics in a resonantly driven two-level artificial atom—a semiconductor quantum dot in a micropillar cavity—when pumped by short optical pulses. By measuring auto-correlation functions up to the fourth order, we observe up to four photons emitted after a single pumping pulse and investigate the emission dynamics with finely resolved temporal measurements. Furthermore, we propose a method based on acquisition time gating to enhance the purity of a single-photon source while maintaining high efficiencies. Our results deepen the understanding of the photon emission processes in coherently driven atomic systems and suggest a simple but effective technique to reduce the multi-photon components of a single-photon source.

V. V. Dodonov, Vladimir I. Man’ko, Olga V. Man’ko

G. S. Agarwal

Jin Xiong, Zhi‐Ming Zhang

The idea of a mazer is put forward with particular reference to the question of the driving-induced atomic coherence, which is established by a coherent driving field. The interaction of a quantum cavity field and an ultracold V-type three-level atom in which two levels are coupled by a coherent driving field, is derived. Its general quantum theory is established and the atomic emission probability and photon statistics are calculated and analysed. It is found that the mazer based on this driving-induced atomic coherence shows new features. There is a non-vanishing probability for the atom emitting a photon in the cavity even when the resonance condition is not fulfilled (here the resonance condition means that the cavity length is an integer multiple of half the atomic de Broglie wavelength). Under the resonance condition, the atomic emission probability has two sets of resonance peaks. For a very strong coherent driving field, the emission of the atom can be forbidden. As to the photon statistics, when the driving field is not very strong, the driving-induced atomic coherence reduces the photon number fluctuations of the cavity field. The photon statistics exhibits strong sub-Poissonian behaviour. In the region considered here, it can even be sub-Poissonian for any cavity length. However, when the driving field is too strong, the sub-Poissonian property may disappear.

Vladilen S Letokhov

Lin-sheng He, Xun‐Li Feng

The time-dependent two-photon emission spectra of a two-level atom interacting with a single-mode radiation field in an ideal cavity have been studied. The expressions of the system operators as a function of time have been derived based on the two-photon Jaynes-Cummings model and Heisenberg equation. As a result, the theoretical curves of the time-dependent two-photon emission spectra have been given. The features of two-photon emission spectra depend not only on the photon statistical distribution of the initial field, such as the thermal field, the squeezed vacuum field, and the coherent field, but also on the passband width of the filter detector \ensuremath{\Gamma}. The two-photon emission spectra exhibit multi- peaked structures when \ensuremath{\Gamma}(two-photon coupling constant).