Coherent states with elliptical polarization

Loucas C. Papaloucas

Guangqiang He, Zeng Gui-Hua

A quantum identification system based on the transformation of polarization of a mesoscopic coherent state is proposed. Physically, an initial polarization state which carries the identity information is transformed into an arbitrary elliptical polarization state. To verify the identity of a communicator, a reverse procedure is performed by the receiver. For simply describing the transformation procedure, the analytical methods of Poincaré sphere and quaternion are adopted. Since quantum noise provides such a measurement uncertainty for the eavesdropping that the identity information cannot be retrieved from the elliptical polarization state, the proposed scheme is secure.

Alastair Brodlie

Valery Milner, Yehiam Prior

We present the first experimental proof for the existence of elliptical dark states, the multilevel analog of the well known three-level dark states. An ensemble of multilevel atoms, when prepared by elliptically polarized light, becomes transparent to probe light of the same polarization. The effect stems from laser-induced coherences between many ground-state magnetic sublevels which reflect the polarization of the light that had created the dark state. The novelty and essential character of the dark states are elucidated by the experimental demonstration of their creation by incoherent light. It is anticipated that elliptical dark states will play an important role in the laser cooling and manipulation of molecules.

V. P. Karasev, Vladimir Leonardovich Derbov, O. M. Priyutov

Vladimir S. Smirnov, Anatolii M Tumaikin, Valeriy I. Yudin