  Dynamical decoupling operations have been shown to reduce errors in quantum
information processing. Leakage from an encoded subspace to the rest of the
system space is a particularly serious problem for which leakage elimination
operators (LEO) were introduced. These are a particular type of decoupling
which are designed to eliminate such leakage errors. Here, we provide an
analysis of non-ideal pulses, rather than the well-understood ideal pulses or
bang-bang controls. We show that under realistic conditions for experiments
these controls will provide protection from errors. Furthermore, we find that
the effect of LEOs depends exclusively on the integral of the pulse sequence in
the time domain with proper ratio of pulse duration time and its period. When
these two key parameters are chosen within certain bounds, leakage errors of
the open system (exemplified by a three-level system for the nitrogen-vacancy
centers under external magnetic field) would be dramatically decreased. The
results are illustrated by the fidelity dynamics of LEO sequences, ranging from
regular rectangular pulses, random pulses and even disordered (noisy) pulses.
