Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[Peter Fairbrother]

On 29/06/2020 20:09, jim bell wrote:

"/Scientists in China managed to exchange a crypto key at a distance of 
over 1,000 kilometers/"



Secure quantum communication is very tricky, and afaik the Chinese 
didn't do that, they just did some entangled photon measuring.


First, the non-cloning theory doesn't say what most people think it does 
- it actually says that you can only clone a maximum of 5/6 of photons 
(technically 2/3 get cloned, plus half the remainder or 1/6 just happen 
to be the same orientation by chance).


Second, you need a classically authenticated channel as well as the 
cloning channel to securely exchange keys - it doesn't have to be 
secret, but it does need to be authenticated. If Mallory can attack that 
authentication he can prevent key exchange, and in some cases can obtain 
the key.



Although, in a way quantum mechanics can be described  as a
cosmic joke played on physicists.  Somewhat akin to Kurt Godel's work 
being a joke played on mathematicians and logicians.


More like Godel shoving a stick up their asses.

Godel's first incompleteness theorem is simple: First, if a system of 
logic is complicated enough to contain the statement "this statement is 
a lie" then the system contains contradictions [*]. Second, any system 
of mathematics which is complicated enough to include natural arithmetic 
is complicated enough to contain that statement.


That's not quite how Godel put it, but it's much the same result.

Of course everyone already knew that really, but pretended it was just a 
curiosity so they could look for a universal system for all mathematics; 
the shock was just Godel pointing it out in a way that could not be ignored.



I suspect that one day quantum mechanics may be seen exactly the same way.



[*] statements which cannot be assigned a true or false value. A bit 
like qubits...


Peter Fairbrother

Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[Bill Stewart]

On 6/29/2020 6:57 PM, Punk-Stasi 2.0 wrote:

On Sun, 28 Jun 2020 23:54:43 + (UTC)
jim bell  wrote:


Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography.
https://cointelegraph.com/news/experts-split-on-practical-implications-of-quantum-cryptography

bullshit as usual.
As far as I know so called 'quantum key distribution' needs an 
authenticated 'classical channel' to work, so it's completely pointless.


There seem to be two kinds of Quantum Crypto out there
- the kind that needs a piece of fiber
- the kind that lets you send your photons in free space between ground 
and satellite.


The former's a very niche application, and doesn't protect you about 
things like pseudonymity vs contact tracing (because you follow the 
piece of fiber and see who's at the other end, or follow the money and 
see who's renting the fiber :-).
It's more useful if your threat model is "Auditors" than "Spies"; 
otherwise you can send an extra diverse dude with a briefcase handcuffed 
to their arm for an initial authentication key exchange and then use 
another layer of Diffie-Hellman for authentication, maybe with an 
annoyingly long ECC key, while also printing the authentication public 
key in a classified ad in the NY Times or Pravda or Federal Register.


The latter's "interesting"; I'm skeptical about its usefulness, but 
haven't looked into it deeply, beyond a quick read of

https://arxiv.org/ftp/arxiv/papers/1909/1909.13061.pdf
There seem to be three approaches
- one end-to-end quantum-protected hop (ground to bird to ground)
- two (ground to bird-in-the-middle, bird-in-the-middle to ground)
- two (trusted-bird sends entangled pair, one to Alice, one to Bob)
Approach 1 doesn't appear to exist, approach 2 lets you use two 
prepare-and-measure channels (meh), approach three could be useful-ish



	Also, my current guess/understanding is that there isn't any 'entanglement' at all.The "trusted-bird sends entangled pair, one to Alice, one to Bob" method 
uses entanglement, but needs a bigger satellite than the 
bird-in-the-middle approach.  (According to the paper, it needs more 
than a 100kg satellite, as opposed to a single-end thing which can fit 
on an under-10kg cubesat.)

Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[таракан]

> On Monday, June 29, 2020, 09:50:46 AM PDT, Karl  wrote:
>>Jim put a lot of energy here into replying to a joke.
>
> I'm not aware that:
>
> "Scientists in China managed to exchange a crypto key at a distance of over 
> 1,000 kilometers"
>
>>"Wow!"
>
>>"How can they do that?"
>
> is a joke.
>
> Actually this 50% a joke 50% serious, since the initial article did not 
> mention anything about using Quantum Entanglement and so as such the 
> challenged looked as if we were in ... 1820...

now for the 50% seriousity, I wonder how they can really use quantum 
entanglement at such a distance ... I am sceptical there and it would be 
marvelous if they really achieved what they claim they achieved... quantum 
entanglement over more than 1,000 km of distance... you flip a bit, it gets 
'instantaneously' flipped on an other part of the world, located at 1,200 km 
distance, information without matter movement, at a speed (much) faster than 
light.

I got the explaination from Jim, still besides the obvious issues with the 
cables etc... such phenomenon as quantum entanglement relies on very complex 
experimentation and so I am not convinced at all that what they exchanged ( 
cryptohgraphic keys but in that context doesn't relaly matter ) was not used by 
"ordinary" communication, eg with matter displacement.

Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[jim bell]

, must carry 
physical properties or attributes not included in quantum theory, and the 
uncertainties in quantum theory's predictions are due to ignorance of these 
properties, later termed "hidden variables". Their scenario involves a pair of 
widely separated physical objects, prepared in such a way that the quantum 
state of the pair is entangled. "      [partial quote]


Quantum communication over fiber optics has been done to a record distance of 
50 kilometers.  
Entanglement sent over 50 km of optical fiber

| 
| 
| 
|  |  |

 |

 |
| 
|  | 
Entanglement sent over 50 km of optical fiber

For the first time, a team has sent a light particle entangled with matter over 
50 km of optical fiber. This pav...
 |

 |

 |



    
Ironically, I have actually made a major contribution to this field, although 
almost nobody realizes it yet.  The limit to the distance of quantum 
entanglement, 50 kilometers above, is based on the amount of optical loss 
present in the fiber.  Prior to my invention, and currently, the record for a 
low-loss single-mode optical fiber is by Sumitomo Electric, and is 0.1419 
db/kilometer.      
https://global-sei.com/company/press/2017/03/prs029.html#:~:text=Now%20Sumitomo%20Electric%20has%20advanced,lowest%20loss%20of%20optical%20fiber.
Fiber optics scientists and engineers achieved a fiber loss of about 0.200 
db/km in 1978, and about 0.160 by the mid-1980's.  They are apparently 
approaching a limit asymptotically, the limit defined by the presence of 
natural-quantities of spin-containing isotopes in silica.  
In about December 2008, while stuck in a Federal prison cell at USP Tucson, 
Arizona, I realized that the cause of the residual loss in these fibers is the 
Si-29 and O-17 isotope atoms, and for Corning-type fibers (containing germania, 
or GeO2, dopant), the Ge-73 isotope atoms.  Remove these spin-containing 
isotopes from optical fiber silica, and it should be possible to drop the loss 
by at least a factor of 100, or to about 0.001db/kilometer.
(Corning-type fibers use a core of 8% GeO2 and 92% SiO2, and pure silica in the 
cladding.   Sumitomo-type fibers use(s) a pure-silica core, and a 
fluorine-doped cladding.  Since there are fewer spin-containing isotopes in 
pure silica than in germania-doped silica, Sumitomo had/has a small loss 
advantage over Corning.)
If this fiber is used for comunication between New York and Ireland, the hop 
should be achievable by a single, continuous fiber.  It will not need to 
contain the 40-odd EDFA  https://en.wikipedia.org/wiki/Optical_amplifier  
amplifiers currently employed.  
Similarly, if such fiber is used for a quantum link, it should be possible to 
do the link at least at a distance of 5000 kilometers, 100x better than the 
recent (2019) record.
The Chinese have been doing entanglement experiments on a satellite named 
Micius.  https://en.wikipedia.org/wiki/Quantum_Experiments_at_Space_Scale
 "QUESS is a proof-of-concept mission designed to facilitate quantum optics 
experiments over long distances to allow the development of quantum encryption 
and quantum teleportation technology.[7] Quantum encryption uses the principle 
of entanglement to facilitate communication that is totally safe against 
eavesdropping, let alone decryption, by a third party. By producing pairs of 
entangled photons, QUESS will allow ground stations separated by many thousands 
of kilometres to establish secure quantum channels.[3] QUESS itself has limited 
communication capabilities: it needs line-of-sight, and can only operate when 
not in sunlight.[8] "
               Jim Bell



On Monday, June 29, 2020, 12:43:08 AM PDT, таракан 
 wrote:  
 
 I quote the main title of the article:

"Scientists in China managed to exchange a crypto key at a distance of over 
1,000 kilometers"

Wow!

How can they do that?
 On Monday, 29 June 2020 г., 2:54, jim bell  wrote:
 

Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography.
https://cointelegraph.com/news/experts-split-on-practical-implications-of-quantum-cryptography





There is proof inside many peoples' electronics.  Proof that a marketing group 
would contract development of a frightening virus.  A virus that responds to 
peoples' keystrokes and browsing habits, and changes what people see on their 
devices.  A virus that alters political behavior en masse, for profit.


  
  

Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[Karl]

Jim put a lot of energy here into replying to a joke.

Jim appears to be an electronics supergenius.

On Mon, Jun 29, 2020, 4:48 AM jim bell  wrote:

> Albert Einstein called it "spooky action at a distance".  He hated the
> concept of quantum mechanics, saying "God does not play dice with the
> Universe".  Unfortunately, Einstein was quite wrong.
>
> The idea is that pairs of photons can be generated and can go virtually
> any distance, and then a measurement made on one of these photons
> essentially instantaneously determines the equivalent value of the other
> photon.  There is apparently no limit to the distance over which this can
> be done.  A few years ago I read that the apparent velocity of this
> connection is at least 10,000 times c, or the speed of light in a vacuum.
> https://blogs.scientificamerican.com/news-blog/quantum-weirdnes-wins-again-entangl-2008-08-13/#:~:text=(In%202007%2C%20researchers%20transmitted%20entangled,two%20of%20the%20Canary%20Islands.)=But%20in%20reality%2C%20no%20experiment,times%20the%20speed%20of%20light.
>
> "The photons were indeed entangled, the group reports in *Nature*
> .
> But in reality, no experiment is perfect, so what they end up with is a
> lower limit on how fast the entanglement could be traveling: 10,000 times
> the speed of light."
>
> I'm not a good person to be explaining this to you:  My degree is in
> chemistry, not physics.
> But read up on Bell's inequalities.  (different Bell!)
> https://en.wikipedia.org/wiki/Bell%27s_theorem
>
>
> *"Bell's theorem* proves that quantum physics
>  is incompatible with local
> hidden variable theories
> . It was
> introduced by physicist John Stewart Bell
>  in a 1964 paper titled
> "On the Einstein Podolsky Rosen Paradox
> ", referring to a 1935 thought
> experiment  that Albert
> Einstein , Boris Podolsky
>  and Nathan Rosen
>  used to argue that quantum
> physics is an "incomplete" theory.[1]
> [2]
>  By
> 1935, it was already recognized that the predictions of quantum physics are
> probabilistic . Einstein,
> Podolsky and Rosen presented a scenario that, in their view, indicated that
> quantum particles, like electrons 
>  and photons , must carry physical
> properties or attributes not included in quantum theory, and the
> uncertainties in quantum theory's predictions are due to ignorance of these
> properties, later termed "hidden variables". Their scenario involves a pair
> of widely separated physical objects, prepared in such a way that the quantum
> state  of the pair is
> entangled . "
> [partial quote]
>
>
> Quantum communication over fiber optics has been done to a record distance
> of 50 kilometers.
>
>
> https://www.sciencedaily.com/releases/2019/08/190829150732.htm#:~:text=For%20the%20first%20time%2C%20a,for%20a%20future%20quantum%20internet.=FULL%20STORY-,For%20the%20first%20time%2C%20a%20team%20has%20sent%20a%20light,50%20km%20of%20optical%20fiber.
>
>
> Ironically, I have actually made a major contribution to this field,
> although almost nobody realizes it yet.  The limit to the distance of
> quantum entanglement, 50 kilometers above, is based on the amount of
> optical loss present in the fiber.  Prior to my invention, and currently,
> the record for a low-loss single-mode optical fiber is by Sumitomo
> Electric, and is 0.1419 db/kilometer.
> https://global-sei.com/company/press/2017/03/prs029.html#:~:text=Now%20Sumitomo%20Electric%20has%20advanced,lowest%20loss%20of%20optical%20fiber.
>
> Fiber optics scientists and engineers achieved a fiber loss of about 0.200
> db/km in 1978, and about 0.160 by the mid-1980's.  They are apparently
> approaching a limit asymptotically, the limit defined by the presence of
> natural-quantities of spin-containing isotopes in silica.
>
> In about December 2008, while stuck in a Federal prison cell at USP
> Tucson, Arizona, I realized that the cause of the residual loss in these
> fibers is the Si-29 and O-17 isotope atoms, and for Corning-type fibers
> (containing germania, or GeO2, dopant), the Ge-73 isotope atoms.  Remove
> these spin-containing isotopes from optical fiber silica, and it should be
> possible to drop the loss by at least a factor of 100, or to 

Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[jim bell]

te quantum optics 
experiments over long distances to allow the development of quantum encryption 
and quantum teleportation technology.[7] Quantum encryption uses the principle 
of entanglement to facilitate communication that is totally safe against 
eavesdropping, let alone decryption, by a third party. By producing pairs of 
entangled photons, QUESS will allow ground stations separated by many thousands 
of kilometres to establish secure quantum channels.[3] QUESS itself has limited 
communication capabilities: it needs line-of-sight, and can only operate when 
not in sunlight.[8] "
               Jim Bell



On Monday, June 29, 2020, 12:43:08 AM PDT, таракан 
 wrote:  
 
 I quote the main title of the article:

"Scientists in China managed to exchange a crypto key at a distance of over 
1,000 kilometers"

Wow!

How can they do that?
 On Monday, 29 June 2020 г., 2:54, jim bell  wrote:
 

Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography.
https://cointelegraph.com/news/experts-split-on-practical-implications-of-quantum-cryptography




  

Re: Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[таракан]

I quote the main title of the article:

"Scientists in China managed to exchange a crypto key at a distance of over 
1,000 kilometers"

Wow!

How can they do that?

On Monday, 29 June 2020 г., 2:54, jim bell  wrote:

> Cointelegraph: Experts Split on Practical Implications of Quantum 
> Cryptography.
> https://cointelegraph.com/news/experts-split-on-practical-implications-of-quantum-cryptography

Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography

[jim bell]

Cointelegraph: Experts Split on Practical Implications of Quantum Cryptography.
https://cointelegraph.com/news/experts-split-on-practical-implications-of-quantum-cryptography