Theory of 2 δ-kicked quantum rotors

We examine the quantum dynamics of cold atoms subjected to pairs of closely spaced kicks from standing waves of light and find behavior quite unlike the well-studied quantum kicked rotor QKR. We show that the quantum phase space has a periodic, cellular structure arising from a unitary matrix with oscillating bandwidth. The corresponding eigenstates are exponentially localized, but scale with a fractional power L~ħ_(-0.75), in contrast to the QKR for which L~ħ_(-1). The effect of intercell (and intracell) transport is investigated by studying the spectral fluctuations with both periodic as well as “open” boundary conditions