re. hot-boffin stuff
I was hoping for a picture of a hot boffin, for educational purposes.
One of the hurdles facing photon-based quantum systems using entangled photons is that it's hard to create them at the 1550 nm wavelengths used in telecommunications systems. Entanglements are the basis for all sorts of hot-boffin stuff: quantum information processing, repeaters, photon-based key exchange, and fully quantum …
" So just short range entanglement in real comms terms"
You do realise that 1550nm is the long-haul wavelength range used by telcos, don't you - so we're looking at distances in the order of 1000s of kms without having to decode or otherwise interfere with the photon. This sort of range is currently available off-the-shelf with existing DWDM systems, so no great break through required there.
Hence the push to get it working at 1550nm - there's no commercial advantage to using this technology within a data centre or even across campus, but trans-Pacific or trans-Atlantic is a different story altogether. I doubt that the cryogenic requirement would be too much of an issue either - it used to be a requirement for the low noise amplifiers in satellite antennas, but it didn't stop that technology being widely deployed.
If there's a significant economic advantage to this technology for long-haul carriers (and I suspect there is, capacity-wise) it will be developed into a stable and reliable commercial product surprisingly quickly.
Distances are more like <100km for single mode fibre spans before amp/regen is needed. But the commercials will revolve around where the applications for tangled photons lie. Plus figuring out any SLAs.. Some work's been done already around quantum cryptography already, and capacity would rely on bits per qbit. Then cost to double capacity vs using another fibre or wavelength. Or it may lead to advances in quantum teleportation, and then no need for fibres at all.