They want to store the state of received photons on „quantum harddrives“, transport them to the same place, read the states out and let them interfere locally.

This is the mentioned paper from december 2020 about hour-long optical storage (by Chaun-Feng Li et al.):

https://arxiv.org/abs/2012.14605

(Earlier article from 2015 about this storage technique: https://newatlas.com/quantum-encryption-storage-drive/35553/ )

The state (phase) of the received photon will depend on the position of the receiver. Even if you have a perfect quantum hard drive, you still need to maintain the position of your receivers to within a wavelength. That will be hard to do if they are separated by a long distance.

There are already some crazy light sources with line width of less than a single Hz (not a typo) https://www.news.ucsb.edu/2019/019332/quiet-light

Still other work to be done, and worrying about what happens in the fibre optics, but it is becoming possible, especially if the coherence does not need to be long lived.

The perseverance of scientific obsession must not be underestimated.

It is also amazing how the right amount of curiosity, ingenuity and spirit can create opportunity for insight.

The optimism of scientific publications likewise