Abstract
We propose a method for transferring atoms to a target quantum state for a multilevel quantum system with sequentially increasing, but otherwise unknown, energy splitting. This is achieved with a feedback algorithm that processes off-resonant optical measurements of state populations during adiabatic rapid passage in real time. As a demonstration, we reliably perform the state transfer vertical bar F = 2, m(F) = 2 > -> vertical bar 1, 1 > -> vertical bar 2, 1 > for a sample of ultracold Rb-87 in the presence of a random external magnetic field.