  We exploit quantum discord (and geometric discord) to detect quantum
correlations present in a well-known communication model called quantum random
access codes (QRACs), which has a variety of applications in areas ranging form
quantum communication complexity, network coding, information causality, to
security proof of QKD protocol. In spite of the fact that there is no
entanglement between the two parts involved in this model, analytical
derivation shows that the quantum discord is nonzero and highlights that
quantum discord might be regarded as a figure of merit to characterize the
quantum feature of QRACs, since this model has no classical counterparts. To
gain further insight, we also investigate the dynamical behavior of quantum
discord under state rotations. As a comparison, the connection between quantum
discord and dimension witness is graphically discussed. Interestingly, our
results illustrate that these two quantities are monotonically related to each
other, which implies that the dimension witness and nonclassical correlations
may be intrinsically linked.
