Photonic high-dimensional entanglement in the spatial degree of freedom has recently emerged as a practical way to enhance the capacity of quantum information systems, as well as increase their robustness to noise. However, while qubit entanglement has been distributed over large distances through free-space and fibre, the transport of high-dimensional entangled states of light through highly complex media has never been demonstrated.
After many months of hard work, we achieved the transport of high-dimensional spatial-mode entanglement through a commercial multi-mode fibre for the first time. In our experiment, one photon from a bipartite spatially entangled state was sent through a two-metre piece of multi-mode fibre from Thorlabs. Interestingly, while entanglement was completely lost, the resulting “scrambled” correlations captured the behaviour of the multi-mode fibre in the form of its transmission matrix. This information allowed us to recover the entanglement by only manipulating the entangled partner photon that did not enter the fibre!
For more details, please read our preprint: N. H. Valencia, S. Goel, W. McCutcheon, H. Defienne, and M. Malik, “Unscrambling Entanglement through a Complex Medium”, arXiv:1910.04490 (2019), Link: https://arxiv.org/abs/1910.04490