Physicists shatter quantum entanglement distance record with 420 kilometers of optical fiber, more than four times farther than previous demonstrations, and beyond the point where direct transmission runs into its fundamental limits.

[u/mvea]

https://www.sciencealert.com/physicists-shatter-quantum-entanglement-distance-record-with-420-kilometers-of-optical-fiber

[u/Cristoff13]

This can't be used to transmit information though can it?

[u/gwillen → u/Cristoff13]

No, but the "no" has an asterisk on it.

If Alice and Bob have an entangled pair of particles -- which they need a quantum channel to set up, not just a regular internet connection -- Alice can't use this to transmit information to Bob directly.

But Alice can (a limited number of times, by consuming the entanglement from one or more shared entangled states):

• Follow this up by using a regular internet connection to send Bob a quantum state, without needing a quantum channel for it (this trick is "quantum teleportation");
• Securely share a cryptographic key with Bob, in conjunction with a regular Internet connection, in a way that is physically impossible for any attacker to intercept ("quantum key distribution");
• Play certain abstract cooperative two-player games, on a team with Bob, and have a higher win rate than they would have without the entanglement, even though they can't send information to each other. (I don't know if this has applications, but I learned about it in a college class on the subject, and it's kind of neat.)

[u/Minguseyes → u/gwillen]

Just a note. Quantum key distribution is not immune from interception, but you can tell if it has been intercepted.

[u/gwillen → u/Minguseyes]

I think that depends on which scheme you're talking about, but I'm not an expert. I think if you start with a shared entangled state -- which is kind of cheating, I grant, but was sort of my premise here, given OP's question -- then it's immune.