Creation and detection of molecular schrödinger cat states: Iodine in cryogenic krypton observed via four-wave-mixing optics

This contribution addresses the experimental observation and theoretical interpretation of environment-induced decoherence of molecular Schrödinger cat states, as observed for dihalogen molecules embedded in a cryogenic rare gas environment. We specifically address a three-pulse experiment performed on an I-krypton system, involving the coherent creation, by two distinct optical pulses, of a vibrational Schrödinger cat state and its observation through a third pulse which induces a Raman scattering signal that reports on the time-evolving coherence. Full quantum-mechanical simulations of the combined molecule-plus-environment system under the influence of the external fields are reported, making use of advanced wave packet propagation techniques. As a key quantity, a time-evolving subsystem coherence matrix is characterized, and its evolution as a function of the state preparation is discussed. In line with the experiment, it is found that long-lived coherences can be observed, even though the system-bath coupling is comparatively strong. The system–environment interactions fall into a non-Markovian regime and are determined by a few specific environmental modes that strongly interact with the chromophore. A perspective is given on general implications of these observations for molecular systems embedded in a matrix or solvent environment.