  We compute one-loop corrections to the energy of a IIA giant magnon solution
in the $AdS_4 \times CP^3$ background by using the standard quantum field
theory (QFT) techniques. The string action is expanded around the solution to
the quadratic order in the fluctuation fields. The resulting action has 2D
coordinate dependent-coefficients, a feature that complicates the analysis. The
solution contains a worldsheet velocity parameter $v$, and is expanded in terms
of the parameter. A perturbative analysis is carried out by treating the
$v$-dependent parts as vertices. The energy is computed by first putting the
system in a box of length $L$ and Fourier-transforming the fields into the
discrete momentum modes. We compare our result with the results obtained by the
algebraic curve method.
