Counter-counter-intuitive quantum coherence effects

The study of an ensemble of phase-coherent atoms has recently lead to interesting theoretical innovations and experimental demonstrations of counter-intuitive effects such as electromagnetically induced transparency (EIT), lasing without inversion (LWI), enhancement of index of refraction and ultra-large nonlinear susceptibility. In the present notes, we report a couple of new effects along these lines. In fact, it would be fair to call them surprises even in the repertoire of 'counter-intuitive effects', i.e. 'counter-counter-intuitive effects'. Specifically, we will show that the LWI concept, which is based on quantum coherence, has an interesting counterpart in the classical physics of free electron laser operation. In other current work, we find that it is possible to 'lock' atoms in an excited state via atomic coherence. It is, by now, not surprising that such a phase-coherent ensemble can show holes or dark lines in the emission spectrum. It is surprising that we can lock atoms in an excited (normally decaying) state via atomic coherence and interference. Such a phase-coherent collection of atoms, i.e. 'phaseonium', is indeed a novel new state of matter.