  Masking of quantum information spreads it over nonlocal correlations and
hides it from the subsystems. It is known that no operation can simultaneously
mask all pure states [Phys. Rev. Lett. 120, 230501 (2018)], so in what sense is
quantum information masking useful? Here, we extend the definition of quantum
information masking to general mixed states, and show that the resource of
maskable quantum states are far more abundant than the no-go theorem seemingly
suggests. Geometrically, the simultaneously maskable states lays on hyperdisks
in the state hypersphere, and strictly contain the broadcastable states. We
devise a photonic quantum information masking machine using time-correlated
photons to experimentally investigate the properties of qubit masking, and
demonstrate the transfer of quantum information into bipartite correlations and
its faithful retrieval. The versatile masking machine has decent extensibility,
and may be applicable to quantum secret sharing and fault-tolerant quantum
communication. Our results provide some insights on the comprehension and
potential application of quantum information masking.
