  Owing to a reduced solar background and low propagation losses in the
atmosphere, the 2- to 2.5-$\mu$m waveband is a promising candidate for daylight
quantum communication. This spectral region also offers low losses and low
dispersion in hollow-core fibers and in silicon waveguides. We demonstrate for
the first time near-maximally entangled photon pairs at 2.1 $\mu$m that could
support device independent quantum key distribution (DIQKD) assuming
sufficiently high channel efficiencies. The state corresponds to a positive
secure-key rate (0.254 bits/pair, with a quantum bit error rate of 3.8%) based
on measurements in a laboratory setting with minimal channel loss and
transmission distance. This is promising for the future implementation of DIQKD
at 2.1 $\mu$m.
