DAMPING OF QUANTUM SUPERPOSITIONS

We study the first-order perturbation contribution of a generic Markovian master equation on a general superposed quantum state. From this we obtain a universal formula describing the decay of quantum superpositions for arbitrary quantum superpositions. For single-photon damping, superposed coherent states appear, naively, to give the smallest damping rate. However, a comparison of damping rates, based on the observability of superposition fringes, shows that superposed squeezed states can do significantly better than their coherent state rivals. The optimum squeezed superposition is shown to have a damping rate (for the zero-temperature Markovian master equation) linear in the phase-space distance between the pieces of the original unsqueezed superposition, as compared with the quadratic dependence for superpositions of coherent states. Finally, we show that superpositions of squeezed states can be generated directly from squeezed states without having to squeeze a superposition.