  In addition to being a workhorse for modern quantum technologies,
entanglement plays a key role in fundamental tests of quantum mechanics. The
entanglement of photons in multiple levels, or dimensions, explores the limits
of how large an entangled state can be, while also greatly expanding its
applications in quantum information. Here we show how a high-dimensional
quantum state of two photons entangled in their orbital angular momentum can be
split into two entangled states with a smaller dimensionality structure. Our
work demonstrates that entanglement is a quantum property that can be
subdivided into spatially separated parts. In addition, our technique has vast
potential applications in quantum as well as classical communication systems.
