We derive an explicit expressions for geometric description of state manifold obtained from evolution governed by a three parameter family of Hamiltonians covering most cases related to real interacting twoqubit systems. We discuss types of evolution in terms of the defining parameters and obtain relevant explicit description of the pure state spaces and their Remannian geometry with the Fubini-Study metric .

A simple, room-temperature, cavity-and vacuum-free interface for an efficient photon-matter interaction is implemented. In the experiment a heralded single photon generated by the process of spontaneous parametric down-conversion is absorbed by a single atom-like system, specifically a nitrogen-vacancy color center in diamond. Here phonon-assisted absorption solves the mismatch problem of a narrow absorption bandwidth in a typical atomic medium and broadband spectrum of quantum light. The source is tunable in the spectral range 452 − 575 nm, which overlaps well with the absorption spectrum of nitrogen-vacancy centers. This can also be considered as a useful technique paving the way for development of novel quantum information processing and sensing applications.arXiv:1909.05843v1 [quant-ph]

A simple, room-temperature, cavity- and vacuum-free interface for a photon-matter interaction is implemented. In the experiment, a heralded single photon generated by the process of spontaneous parametric down-conversion is absorbed by an ensemble of nitrogen-vacancy color centers. The broad absorption spectrum associated with the phonon sideband solves the mismatch problem of a narrow absorption bandwidth in a typical atomic medium and broadband spectrum of quantum light. The heralded single photon source is tunable in the spectral range 452 − 575 nm, which overlaps well with the absorption spectrum of nitrogen-vacancy centers.