  Introducing quantum confinement has uncovered a rich set of interesting
quantum phenomena and allows one to directly probe the physics of confined
(quasi-)particles. In most experiments, however, electrostatic potential is the
only available method to generate the quantum confinement in a continuous
system. Here, we demonstrated experimentally that inhomogeneous pseudomagnetic
fields in strained graphene can introduce exotic quantum confinement of
massless Dirac fermions. The pseudomagnetic fields have opposite directions in
the two distinct valleys of graphene. By tuning real magnetic field, the total
effective magnetic fields in the two valleys are imbalanced. Then, we realized
valley-contrasting spatial confinement, which lifts the valley degeneracy and
results in field-tunable valley-polarized confined states in graphene. Our
results provide a new avenue to manipulate the valley degree of freedom.
