Classical behavior with small quantum numbers: The physics of Ramsey interferometry of Rydberg atoms

In Ramsey atomic interferometry, a superposition of atomic states is produc ed by a mechanism completely equivalent (for experimental purposes) to inte raction with a classical field. Since this property holds, in the case of R ydberg atoms, for temperatures close to absolute zero and field intensities of the order of a single photon, the question arises as to why the quantum nature of the field can be neglected. We model the passage of an atom thro ugh a Ramsey zone and show that, in order to explain the phenomenon, correl ation properties between three subsystems and strong cavity dissipation tur n out to be the essential physical ingredients leading to classical behavio r.