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Quantum 'spooky action at a distance' becoming practical?

phys.org

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Re: Quantum 'spooky action at a distance' becoming practical?

#31

Post by albutr »

comstock wrote: post #28
albutr wrote: post #23

Earlier quoted context omitted.

No, it's just one particular method of creating entangled pairs, e.g. there are integrated semiconductor devices that can be used to generate them using other physical effects (but AFAIK SPDC is what most people use in practical situations)

Interesting, do you have any search terms I could use to google for the semiconductor devices (I’ll try myself, but if you have a jumping off point that would be helpful).

Sure, one example that I'm familiar with is frequency entangled photons produced by parametric scattering of exciton-polaritons (it's scattering of quasiparticles in a quantum well which are strongly coupled to a photon field). Although, I actually can't recall if I've seen a convincing experimental demonstration of this.

I have seen a bunch of experimental results which demonstrated entanglement using integrated silicon waveguides, where there are two waveguides that overlap in an effective "beam splitter" section then separate again (this is analogous to how you can get entanglement from an Hong-Ou-Mandel setup, which is two (EDIT: identical photons) incident on a 50/50 beam splitter which produces so-called "path entangled" photons).

Here's a recent short review paper which goes over some additional semiconductor devices which can produce entangled photon pairs[1].

[1] https://arxiv.org/abs/1702.08823

Re: Quantum 'spooky action at a distance' becoming practical?

#33

Post by mathw »

thaumasiotes wrote: post #30
QAPereo wrote: post #26

Earlier quoted context omitted.

If you have secrets to keep, and your adversaries have that kind of access, better a DDOS than a leak. Edit: This kind of observation would already require physical access to the communications medium (e.g. a fiber optic cable). So if you could DoS a quantum encrypted channel by measuring it, you could equally well DoS a classical channel by just cutting the fiber. The comment just above mine, which does a better job…

Well, the whole point of encryption is that you can send your message through despite the fact that your adversary can see it. Replacing that with a system where your adversary can't see your message, and neither can your correspondent, is a downgrade, not an upgrade.

That depends entirely on your application.

Re: Quantum 'spooky action at a distance' becoming practical?

#34

Post by binarytransform »

zitterbewegung wrote: post #29
TipVFL wrote: post #7

Quantum entanglement is such a neat phenomenon, but secure communication feels like such a boring application. How much extra security would a quantumly protected communication channel provide over just using some really heavy encryption sent in a normal manner?

Current production quantum key distribution systems are actually succeptable to attack by gaming the systems that detect the particles and going beyond their limitations .

Source?

Re: Quantum 'spooky action at a distance' becoming practical?

#35

Post by filleokus »

binarytransform wrote: post #34
zitterbewegung wrote: post #29

Earlier quoted context omitted.

Current production quantum key distribution systems are actually succeptable to attack by gaming the systems that detect the particles and going beyond their limitations .

Source?

I'm not sure if GP is talking about this https://en.wikipedia.org/wiki/Quantum_key_distribution#Troja... or not, but that's definitely an issue.

Re: Quantum 'spooky action at a distance' becoming practical?

#36

Post by Asooka »

alex_anglin wrote: post #10
TipVFL wrote: post #7

Quantum entanglement is such a neat phenomenon, but secure communication feels like such a boring application. How much extra security would a quantumly protected communication channel provide over just using some really heavy encryption sent in a normal manner?

That observation of the communication would break the link, versus capture and (attempt to) decrypt?

A channel that disappears the moment you look at it seems like it would be very vulnerable to DoS.

Re: Quantum 'spooky action at a distance' becoming practical?

#37

Post by Faaak »

TipVFL wrote: post #16
alex_anglin wrote: post #10

Earlier quoted context omitted.

That observation of the communication would break the link, versus capture and (attempt to) decrypt?

That seems very exploitable, an enemy could theoretically intercept all your communications, just to prevent you from communicating.

You can also take a pair of scissors and cut the fiber

Re: Quantum 'spooky action at a distance' becoming practical?

#38

Post by reacweb »

Klathmon wrote: post #13
alex_anglin wrote: post #10

Earlier quoted context omitted.

That observation of the communication would break the link, versus capture and (attempt to) decrypt?

That to me seems like the coolest possibility. Encryption that breaks if someone other than the authorized parties observes it. Something which isn't possible with "traditional" encryption.

encryption breaks if someone "observes more" than is allowed by error correction. Physical world is rarely binary.

Re: Quantum 'spooky action at a distance' becoming practical?

#39

Post by thaumasiotes »

mathw wrote: post #33
thaumasiotes wrote: post #30

Earlier quoted context omitted.

Well, the whole point of encryption is that you can send your message through despite the fact that your adversary can see it. Replacing that with a system where your adversary can't see your message, and neither can your correspondent, is a downgrade, not an upgrade.

That depends entirely on your application.

Could you give some examples of applications of encryption where the purpose is not to send a message that adversaries may see but cannot understand?

Re: Quantum 'spooky action at a distance' becoming practical?

#40

Post by amelius »

alex_anglin wrote: post #10
TipVFL wrote: post #7

Quantum entanglement is such a neat phenomenon, but secure communication feels like such a boring application. How much extra security would a quantumly protected communication channel provide over just using some really heavy encryption sent in a normal manner?

That observation of the communication would break the link, versus capture and (attempt to) decrypt?

What is the practical application of this then, considering that you can choose an arbitrarily large key to make eavesdropping or tampering practically impossible?

I don't get what's so exciting about this.

Or does this only become practically useful once quantum computing breaks traditional encryption?

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