metropolbadger

A faculty not allowing LaTeX seems like a weird choice, what were their reasons? Did they need direct access to a document for editing or something? Would honestly be a huge red flag for me if someone would tell me in which editor I cannot write a doc.

All good! That was me 5 years ago :)

- Yes and no. The photons emitted and sent through the fiber are entangled with their electron counterparts. So we send simultaneously a photon state (entangled with electron) from Delft, and a photon state (entangled with electron) from Den Haag. Those states interfere in the midpoint (Rijswijk), and upon measurement of one photon (photon now is absorbed/measured/gone) we know that the _electrons_ of the nodes in Delft and Den Haag are entangled.

- The above also answers this question: yes!

- No. They can be used to transfer a quantum state from one place to the other, for example, which _consumes_ the entanglement (one-time use only, per pair of entangled particles). However, still classical feedback signals need to propagate for that to happen, so we still need _a_ link, preferably optical (for speed and distance). Wiki has actually a great page on teleportation: https://en.wikipedia.org/wiki/Quantum_teleportation

I'll answer to a different question on repeaters later in another comment, so check back :) Indeed, multi-node quantum network was an awesome experiment. This takes it to the next level of being able to distribute entanglement over large distances and between quantum nodes that are self-sufficient (no sharing of hardware resources between nodes).

All those incremental changes is what made my research work indeed. As we described in the paper, the margin we had on amount of signal (dependent also on the conversion efficiency!) was small, so every % of loss anywhere in this chain of photon from emission to detection mattered.

Hi all! I'm one of the co-authors. Honestly it's a dream to end up on HN with my research. As mentioned in the video we made, it has been a long road (6-7 years) to achieve this absolute moonshot of a project. I think we'll look back on this demonstration as the first experiment that truly made a distributed and real-world deployed quantum network. Not only did we use a (quantum) hardware platform capable of quantum processing, we also generated the entanglement in a way that it can be used in further quantum computations. In order for all this to work on a distributed network, we had to fully design and build the architecture to support that, both hard- and software. And we did it successfully!

Besides hard-working PhD students, another key ingredient that our research institute QuTech facilitated, was the collaboration with expert hardware and software engineers, allowing us to quickly transform new ideas into (deployable) products. A great show of what's possible when academia mixes with professional engineering. But of course there was enough hacking and tinkering going on that it warrants to be on HN ;)

You can reply here if you have any questions, I'll be checking throughout the day. Thanks!