  Classical information encoded in composite quantum states can be completely
hidden from the reduced subsystems and may be found only in the correlations.
Can the same be true for quantum information? If quantum information is hidden
from subsystems and spread over quantum correlation, we call it as masking of
quantum information. We show that while this may still be true for some
restricted sets of non-orthogonal quantum states, it is not possible for
arbitrary quantum states. This result suggests that quantum qubit commitment --
a stronger version of the quantum bit commitment is not possible in general.
Our findings may have potential applications in secret sharing and future
quantum communication protocols.
