  In this paper, we establish a noncommutative analogue of Calder\'on's
transference principle, which allows us to deduce noncommutative ergodic
maximal inequalities from the special case---operator-valued maximal
inequalities. As applications, we deduce dimension-free estimates of
noncommutative Wiener's maximal ergodic inequality and noncommutative
Stein-Calder\'on's maximal ergodic inequality over Euclidean spaces. We also
show the corresponding individual ergodic theorems. To show Wiener's pointwise
ergodic theorem, we construct a dense subset on which pointwise convergence
holds following a somewhat standard way. To show Jones' pointwise ergodic
theorem, we use again transference principle together with Littlewood-Paley
method, which is different from Jones' original variational method that is
still unavailable in the noncommutative setting.
