Title: The quantum first detection problem
Author: Daniel Adam
Stochastic processes, such as diffusion, are essential in many parts of science, especially in physics and biology. Diffusion of ultracold single atoms can be used to model different physical systems, for example the diffusion of atoms in a tilted optical lattice can be used to describe the behavior of
Josephson junctions, by adjusting the relevant parameters like the damping and potential including the depth of the minima and the tilt.
In our system we observe the diffusion of single atoms in a (tilted) periodic potential coupled to a light bath. Using an optical lattice as conveyor belt allows to apply an adjustable force to the atoms, i.e. tilt the optical lattice more or less. There are two states for diffusional atoms in a tilted optical
lattice. The locked state, when the atoms are trapped in a minimum of the potential and the running state, when the atoms are running only damped by the drag force down the potential. Above a critical point of force the potential minima vanish and only the running state occurs. Increasing the
force can lead to some giant increase of the diffusion coefficient, even for tilted potentials below the critical point.