Superposition states spontaneous emissions

Figure 9.11 Suppression of the 2P-1S spontaneous emission in the hydrogen atom, for which the natural linewidth is 1.66 X 10 cm". The solid lines display the decay of the optimized superposition of the Autler-Townes split levels with no interruptions. The dot-dashed lines are the decay curves of the same superposition states in the presence of interruptions. The dashed lines display the average decay of the two Autler-Townes split components. The optimization time t (marked by a triangle) is 0.2/T(= 0.65 ns), and the total time range displayed is up to 3/r(= 10 ns). A is the Autler-Townes splitting induced by the CW laser and T denotes the natural linewidth. Reprinted figure by permission from Ref. [38]. Copyright 2003 by the American Physical Society.

The procedure that we propose to enhance the concentration of a particulap enantiomer when starting with a racemic mixture, that is, to purify the mixture) is as follows [259], The mixture of statistical (racemic) mixture of L and irradiated with a specific sequence of three coherent laser pulses, as described below. These pulses excite a coherent superposition of symmetric and antisymmetric vibrational states of G. After each pulse the excited system is allowed to relax bg t to the ground electronic state by spontaneous emission or by any other nonradiativ process. By allowing the system to go through many irradiation and relaxatio cycles, we show below that the concentration of the selected enantiomer L or can be enhanced, depending on tire laser characteristics. We call this scenario lat distillation of chiral enantiomers. 

If a quantum state starting from Rb63p3/2), then we take C4 = 1 and C3 = 0. The process described by the arrival state C4 = 0 and C3 = 1 can be seen in a two-fold manner (1) The > -photon is sent away into the cavity by spontaneous emission (2) The linear superposition becomes periodic in time where the state is an entangled state the energy hco is no longer available. 

The effect of quantum interference on spontaneous emission in atomic and molecular systems is the generation of superposition states that can be manipulated, to reduce the interaction with the environment, by adjusting the polarizations of the transition dipole moments, or the amplitudes and phases of the external driving fields. With a suitable choice of parameters, the superposition states can decay with controlled and significantly reduced rates. This modification can lead to subnatural linewidths in the fluorescence and absorption spectra [5,10]. Furthermore, as will be shown in this review, the superposition states can even be decoupled from the environment and the population can be trapped in these states without decaying to the lower levels. These states, known as dark or trapped states, were predicted in many configurations of multilevel systems [11], as well as in multiatom systems [12],... 

Thus, the condition V 2 = /1 1I2 for suppression of spontaneous emission from the antisymmetric state is valid for identical as well as nonidentical atoms, whereas the coherent interaction between the superpositions appears only for nonidentical atoms with different transition frequencies and/or spontaneous damping rates. 

Quantum-beat lasers are a particular form of correlated spontaneous emission lasers (CEL s) [43-49]. Quantum-beat is formed by creating coherence between near degenerate atomic states, either excited states or ground states. In particular, a beam of three-level atoms in Vee configuration emit photons into two modes. The atomic upper levels are initially prepared in a coherent superposition or are coupled by a coherent field [13-17]. The fluetuations of the relative phase and the relative amplitude drop to the vacuum levels. In addition to this, as a different form, correlated spontaneous emission can be formed by creating eoherenee between a pair of states between which lasing transitions occm. One such example is a two-photon CEL [13-17] with a beam of three-level atoms in cascade configuration. The top and bottom states are initially prepared in a coherent superposition state. It was predicted that the phase noise is reduced by 50% below the vacuum noise level. 

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