  Hyperentanglement is a promising resource in quantum information processing
with its high capacity character, defined as the entanglement in multiple
degrees of freedom (DOFs) of a quantum system, such as polarization,
spatial-mode, orbit-angular-momentum, time-bin and frequency DOFs of photons.
Recently, hyperentanglement attracts much attention as all the multiple DOFs
can be used to carry information in quantum information processing fully. In
this review, we present an overview of the progress achieved so far in the
field of hyperentanglement in photon systems and some of its important
applications in quantum information processing, including hyperentanglement
generation, complete hyperentangled-Bell-state analysis, hyperentanglement
concentration, and hyperentanglement purification for high-capacity
long-distance quantum communication. Also, a scheme for hyper-controlled-not
gate is introduced for hyperparallel photonic quantum computation, which can
perform two controlled-not gate operations on both the polarization and
spatial-mode DOFs and depress the resources consumed and the photonic
dissipation.
