  Quantum steering is a recently-defined form of quantum correlation which lies
at the heart of quantum mechanics. In difference from other types of quantum
correlations, quantum steering is inherently asymmetric, which implies that it
could manifest in one direction but not in the opposite direction. This rather
peculiar phenomenon, known as one-way steering, have been demonstrated in
several experiments, but subtlety remains. In fact all experiments were shown
to be ambiguous until a very recent conclusive one, which however made a
crucial use of a high dimensional embedding to get around assumptions. This
leaves the question open whether the one-way steering phenomenon can be
reliably demonstrated in the genuine two-qubit system. Here, we report such an
experimental demonstration of one-way steering for a family of two-qubit
states. Our experimental setup and results thus resolve the subtlety caused by
fidelity assumption in previous experiments without the need of higher
dimensional embedding. Moreover, our work provides a universal method to
characterize one-way steering phenomenon for generic two-qubit states.
