  The uncertainty relation lies at the heart of quantum theory and behaves as a
non-classical constraint on the indeterminacies of incompatible observables in
a system. In the literature, many experiments have been devoted to the test of
the uncertainty relations which mainly focus on the pure states. Here we
present an experimental investigation on the optimal majorization uncertainty
for mixed states by means of the coherent light. The polarization states with
adjustable mixedness are prepared by the combination of two coherent beams, and
we test the majorization uncertainty relation for three incompatible
observables using the prepared mixed states. The experimental results show that
the direct sum majorization uncertainty relations are tight and optimal for
general mixed systems.
