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The quantum internet has arrived (and it hasn’t)

nature.com

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Re: The quantum internet has arrived (and it hasn’t)

#11

Post by krastanov »

hartator wrote: post #9

> quantum particles [...] has been used for years to enhance data encryption. As an entropy source or more?

No, it is way more interesting than that. With entangled particles together with a public unencrypted classical communication channel you can create a protocol to exchange information securely. That protocol does not rely on any computational complexity assumptions, rather only on the assumption that the laws of quantum mechanics are correct. There are some caveats, but it is still an amazing construction.

https://en.wikipedia.org/wiki/Quantum_key_distribution

https://en.wikipedia.org/wiki/BB84

Re: The quantum internet has arrived (and it hasn’t)

#12

Post by IntronExon »

krastanov wrote: post #10
tomonl wrote: post #6

Earlier quoted context omitted.

The image is correct. The information is sent over a classical channel, not using entanglement.

While the image is correct, your statement would be a bit misleading to novices: You can not transfer the state of the qubit over a classical channel. You need both a classical channel and entanglement. Or in other words: a bit can be send over a classical communication channel (by copying it), but to transmit a qubit (which can not be copied due to its quantum nature), you either need to carry the physical qubit ove…

The essence of the issue for many, who seem to equate entanglement with FTL is that a classical channel is required. Without that, you’re just sending noise over your quantum channel.

Plus we get to keep cause and effect ordered, as a little bonus.

Re: The quantum internet has arrived (and it hasn’t)

#13

Post by dang »

crenellated wrote: post #2

Ugh. Images like this are why no one should ever pay attention to fluff magazine articles about quantum anything: https://media.nature.com/w800/magazine-assets/d41586-018-018... The person who created that picture had no clue what the diagram is supposed to represent. They obviously created the infographic based on a conversation with someone who probably also doesn’t completely understand what their talking about. W…

It sounds like you know enough about the topic to post a comment that doesn't break this HN guideline:

Please don't post shallow dismissals, especially of other people's work. A good critical comment is one that teaches us something.

In the future, could you please do that instead? Bilious dismissals degrade discussion; explaining a more correct view elevates it.

https://news.ycombinator.com/newsguidelines.html

Re: The quantum internet has arrived (and it hasn’t)

#15

Post by tristanj »

Do we really need a quantum internet though? Our current non-quantum encryption system honestly works very well. Symmetric encryption is statistically unbreakable at large enough key sizes. Using a brute-force attack on a 256-bit AES key, it would take billions of years to crack, even with a quantum computer. Given a large enough key size (1024-bits), it would take longer than the heat death of the universe to crack such a key.

For key exchange, quantum encryption is definitely better, but how much better is it than switching to a quantum resistant key exchange algorithm? And switching to quantum encryption would require a complete internet infrastructure overhaul, meaning fiber optics everywhere, all new routers (would packet routing still work?), new cell towers, and no more copper lines for internet.

Is this complete architectural overhaul worth it, just to decrease the chance of being hacked from 1/2^256, to 0? To me the benefits seem marginal.

It reminds me of flying cars: yes it's the future, yes they work, yes we can do it, but is it practical?

Re: The quantum internet has arrived (and it hasn’t)

#16

Post by krastanov »

tristanj wrote: post #15

Do we really need a quantum internet though? Our current non-quantum encryption system honestly works very well. Symmetric encryption is statistically unbreakable at large enough key sizes. Using a brute-force attack on a 256-bit AES key, it would take billions of years to crack, even with a quantum computer. Given a large enough key size (1024-bits), it would take longer than the heat death of the universe to crack…

I completely agree that while quantum key exchange is amazing, in practical terms it might not be necessary for great security.

However, creating a long range quantum network (as a supplement to the classical internet), would provide amazing new capabilities (plenty of which we probably have not thought of yet). I am particularly excited about using it to link up sensors (telescopes) so that we can surpass the diffraction limit of classical sensors.

Re: The quantum internet has arrived (and it hasn’t)

#17

Post by krastanov »

crenellated wrote: post #2

Ugh. Images like this are why no one should ever pay attention to fluff magazine articles about quantum anything: https://media.nature.com/w800/magazine-assets/d41586-018-018... The person who created that picture had no clue what the diagram is supposed to represent. They obviously created the infographic based on a conversation with someone who probably also doesn’t completely understand what their talking about. W…

I work in the field, on my way to a doctorate, and I do not see anything bothersome with the infographic. It is well made and factual.

Re: The quantum internet has arrived (and it hasn’t)

#18

Post by space_fountain »

krastanov wrote: post #16
tristanj wrote: post #15

Do we really need a quantum internet though? Our current non-quantum encryption system honestly works very well. Symmetric encryption is statistically unbreakable at large enough key sizes. Using a brute-force attack on a 256-bit AES key, it would take billions of years to crack, even with a quantum computer. Given a large enough key size (1024-bits), it would take longer than the heat death of the universe to crack…

I completely agree that while quantum key exchange is amazing, in practical terms it might not be necessary for great security. However, creating a long range quantum network (as a supplement to the classical internet), would provide amazing new capabilities (plenty of which we probably have not thought of yet). I am particularly excited about using it to link up sensors (telescopes) so that we can surpass the diffra…

Why are quantum links needed? I know you can do radio telescope linking up with just the normal internet.

Re: The quantum internet has arrived (and it hasn’t)

#19

Post by krastanov »

space_fountain wrote: post #18
krastanov wrote: post #16

Earlier quoted context omitted.

I completely agree that while quantum key exchange is amazing, in practical terms it might not be necessary for great security. However, creating a long range quantum network (as a supplement to the classical internet), would provide amazing new capabilities (plenty of which we probably have not thought of yet). I am particularly excited about using it to link up sensors (telescopes) so that we can surpass the diffra…

Why are quantum links needed? I know you can do radio telescope linking up with just the normal internet.

Even keeping things classical, linking radio telescopes in "very-long-baseline interferometry" requires a bit more than just the normal internet (it requires synchronized clocks). But as you suggested, all this is doable classically.

However, all you get with linking telescopes classically is a "virtual" telescope with a better resolution (the angular resolution is roughly proportional to 1/radius of telescope opening, and if your linked telescopes are on different continents you get "virtual" radius as big as that of Earth).

This scaling of the resolution of 1/radius is what gives you the "diffraction limit". However, if we have sensors that are entangled with each other, we can surpass that limit. Googling "quantum entanglement diffraction limit" would give in-depth information.

Re: The quantum internet has arrived (and it hasn’t)

#20

Post by walrus01 »

One of the huge problems of requiring lossless photon transmission through fiber: This will break all currently known approaches to DWDM. It is not economical for inter-city transport between ISPs to require its own dark strand pair, no WDM of any type, in most scenarios. There's a reason why people want to be able to do things like 100/200/400GbE coherent frequencies in a 80-channel DWDM bandplan.
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