Novel collective states of molecules and macroscopic superpositions
While quantum correlations in dipole-coupled arrays of molecules can enhance light-matter interactions, resulting in superradiance, little is known about how their spectroscopic properties change when the dipole-coupling is strong enough to cause electronic polarization. In the first part of this talk I shall analyze a linear array of dipole-coupled molecules that shows a spectroscopic signature of a quantum phase transition between regimes of weak and strong coupling, corresponding to paraelectric and ferro/antiferroelectric polarized phases. The linear absorption is found to show increasing superradiant enhancement as the phase transition is approached and is singular at the transition, after which it displays a quadratic ‘hyperradiant’ size scaling of one-photon absorption and emission in the strong coupling regime. Possibilities for emulating this unusual strong coupling phase and its anomalous superradiance will be discussed. In the second part of the talk I shall summarize recent results systematizing the size of macroscopic superposition states that have led to generalization of the energy-time uncertainty relation to arbitrary quantum states, with implications for the minimal speed of quantum transformations.