  We study Wilson loop operators in three-dimensional, N=6 superconformal
Chern-Simons theory dual to IIA superstring theory on AdS4 x CP3. Novelty of
Wilson loop operators in this theory is that, for a given contour, there are
two linear combinations of Wilson loop transforming oppositely under
time-reversal transformation. We show that one combination is holographically
dual to IIA fundamental string, while orthogonal combination is set to zero. We
gather supporting evidences from detailed comparative study of generalized
time-reversal transformations in both D2-brane worldvolume and ABJM theories.
We then classify supersymmetric Wilson loops and find at most
1/6-supersymmetry. We next study Wilson loop expectation value in planar
perturbation theory. For circular Wilson loop, we find features remarkably
parallel to circular Wilson loop in N=4 super Yang-Mills theory in four
dimensions. First, all odd loop diagrams vanish identically and even loops
contribute nontrivial contributions. Second, quantum corrected gauge and scalar
propagators take the same form as those of N=4 super Yang-Mills theory.
Combining these results, we propose that expectation value of circular Wilson
loop is given by Wilson loop expectation value in pure Chern-Simons theory
times zero-dimensional Gaussian matrix model whose variance is specified by an
interpolating function of `t Hooft coupling. We suggest the function
interpolates smoothly between weak and strong coupling regime, offering new
test ground of the AdS/CFT correspondence.
