The atomic interferometry by Kasevich and Chu (Phys. Rev. Lett. 67, 181(1991)) has been the beginning of a range of very sensitive measurement techniques. We present a complete density matrix analysis of this technique. Although there has been several attempts to provide a theoretical analysis for this technique, the models used are incomplete. The density matrix method allows investigation of all the decoherence effects that are present in the real experimental system. This allows better understanding of how decoherences affect the resolution of the measurement of atom intereferometer, either as a gyroscope, magnetometer or a gravimeter.

Using a set of Zeeman sublevels of an alkali atom such as rubidium or sodium, we propose to construct a pair of coherentc population trap (CPT) states, which can be individually addressed and populated at will. The system can be arranged such that there exists a dressed state that is a linear combination of these two CPT states. We have earlier shown the capability of forming discrete quantum gates using this configuration [J.Phys. B, (2006), 39, 3919]. In the present communication, we will show how the same configuration can be used to prepare and operate continuously varying states. The state can be mapped to a 2D parametric space in such a way that any desired vector within it can be prepared, and a continuous, adiabatic evolution from one vector to another is also possible. A method to exploit a continuous interaction potential, which can be used in quantum computation, is also suggested. We discuss how a continuous variable quantum computation can be performed using such states.