By using the derived master equations, it is shown that the decay of electronic impurities in a nanocrystal can be described as a collective relaxation of particles. A set of entangled states of impurity atoms is found, which have immunity to this relaxation. These states can be used for decoherence-free quantum processing.
It is shown that the dynamics of electronic states of impurities in a nanocrystal embedded in a bulk matrix can be described with the help of the model of a single-mode microcavity with quasi-resonant atoms and losses at the mirrors. In the proposed model, the dynamics of impurities is similar to the collective decay of atoms in a common bath. In the case of a nanocrystal, matrix phonons represent this bath. Impurities interact with the localized phonon mode of the nanocrystal owing to the electron-phonon interaction. The localized phonon mode is coupled with bath phonons at the nanocrystal boundary. In the dispersive limit, the standard model of collective relaxation appears, within the framework of which, different types of many-particle entangled electronic states of impurities are described. In the case of exact resonance, similar entangled states also appear, which are discussed for two impurities in a nanocrystal.
We derive a master equation describing the collective decay of two-level atoms inside a single mode cavity in the dispersive limit. By considering atomic decay in the collective thermostat, we found a decoherence-free subspace of the multiparticle entangled states of the W-like class. We present a scheme for writing and storing these states in collective thermostat.
When a single donor atom is embedded in solid state nanodevice, a rich variety of phenomena in the proximity of T = 0 emerges due to the long phase coherence times Such phenomena are probed by means of charge sensing via tunneling currents. Some aspects connected to the transition from quantum to classical in quantum nanodevices are overviewed: the realization of transport through virtual states, and the definition of the temperature T of a microscopic/mesoscopic system as a key parameter required in the master equation when decoherence is considered. I also discuss the opportunity to study the transition from quantum to classical offered by single atom impurity devices on a time scale below the decoherence time, with a particular emphasis on the experimental test of the Leggett-Garg inequalities.
Relaxation of an excited state of an atom in the vicinity of a nanoparticle has been described taking into account the rotational degrees of freedom of the atom. The description has been compared with the widely used generalized (vector) two-level model of an atom and the classical oscillator model. Relaxation dynamics of real atoms (excluding the atoms with the angular momenta J m = 1 and J n = 0 of the upper and lower levels, respectively) has been found to differ significantly from the predictions of those models.