Ultracold Atoms as Coherent Systems

One of the most important properties of ultracold atoms is their high degree of quantum coherence. The de Broglie wavelength is associated to the whole atomic sample, as already discussed especially in Chap. 3 . Experimental evidences for this feature have been shown both in the direct observation of interference fringes from two condensates and in the manipulation of the phase of the condensate to imprint velocity fields, as demonstrated in the production of solitons and vortices. In this chapter, we focus on quantum coherence of ultracold atoms and its impact in a variety of applications to both measurements of fundamental physics and engineering, most notably in analog and digital computing.