  Quantum annealing aims at solving hard computational problems through
adiabatic state preparation. Here, I propose to use inhomogeneous longitudinal
magnetic fields to enhance the efficiency of the annealing. Such fields are
able to bias the annealing dynamics into the desired solution, and in many
cases, suitable field configurations can be found iteratively. Alternatively,
the longitudinal fields can also be applied as an antibias which filters out
unwanted contributions from the final state. This strategy is particularly well
suited for instances which are difficult to solve within the standard quantum
annealing approach. By numerically simulating the dynamics for small instances
of the exact cover problem, the performance of these different strategies is
investigated.
