  Highly entangled quantum networks cluster states lie at the heart of recent
approaches to quantum computing \cite{Nielsen2006,Lloyd2012}. Yet, the current
approach for constructing optical quantum networks does so one node at a time
\cite{Furusawa2008,Furusawa2009,Peng2012}, which lacks scalability. Here we
demonstrate the \emph{single-step} fabrication of a multimode quantum network
from the parametric downconversion of femtosecond frequency combs. Ultrafast
pulse shaping \cite{weiner2000} is employed to characterize the comb's spectral
entanglement \cite{vanLoock2003}. Each of the 511 possible bipartitions among
ten spectral regions is shown to be entangled; furthermore, an eigenmode
decomposition reveals that eight independent quantum channels
\cite{Braunstein2005} (qumodes) are subsumed within the comb. This multicolor
entanglement imports the classical concept of wavelength-division multiplexing
(WDM) to the quantum domain by playing upon frequency entanglement as a means
to elevate quantum channel capacity. The quantum frequency comb is easily
addressable, robust with respect to decoherence, and scalable, which renders it
a unique tool for quantum information.
