Page 1 of 1

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:08 pm
by Big Nipper
guy smiley wrote:





ANU’s

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:11 pm
by JM2K6
I read about using quantum entanglement for "unbreakable" security some time last year - really fascinating stuff but I struggle to fully understand the concepts behind it.

I miss 6roucho :(

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:12 pm
by Dumbledore
Be interesting to see if it works out. Some smart dudes out there.

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:19 pm
by JM2K6
:thumbup:

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:35 pm
by A5D5E5
I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:37 pm
by Spinbad
Very bloody impressive.

Or as they say here ho bloody impressive.

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:55 pm
by Torquemada 1420
guy smiley wrote:This is beyond my level of quantumming but... shit.

China's supposed tech advances present a fairly solid threat to The World As We Know It and this is out there. The put a laser on a satellite that orbits at 480km, generate a couple of entangled particles and beam them to ground stations 1200km apart, breaking the previous record for successful entanglement distance by a factor of 10.

Insane, right?

https://en.wikipedia.org/wiki/Quantum_entanglement
Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others, even when the particles are separated by a large distance—instead, a quantum state must be described for the system as a whole.
Might I stop it there? What about observation effect?

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 3:57 pm
by Torquemada 1420
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 4:01 pm
by A5D5E5
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
The new bit is "just" engineering I think. It is certainly spooky action at a distance - but great as he was, Einstein was (seemingly) wrong about it.

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 4:04 pm
by Torquemada 1420
A5D5E5 wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
The new bit is "just" engineering I think. It is certainly spooky action at a distance - but great as he was, Einstein was (seemingly) wrong about it.
Merci

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 5:16 pm
by London_Lurker
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.

Re: China, entangled photons and the hackproof net

Posted: Mon Jun 19, 2017 6:03 pm
by A5D5E5
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.
Einstein had a gift for making great discoveries by getting things wrong.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 1:01 am
by Ted.
JM2K6 wrote:I read about using quantum entanglement for "unbreakable" security some time last year - really fascinating stuff but I struggle to fully understand the concepts behind it.

I miss 6roucho :(
Give Mad Scientist a shout.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 1:06 am
by Ted.
A5D5E5 wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
The new bit is "just" engineering I think. It is certainly spooky action at a distance - but great as he was, Einstein was (seemingly) wrong about it.
Didn't he lose a wager, or some such, or had he karked it before it was confirmed in the 60's?

Could this phenomenon, just possibly, lead to teleportation?

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 1:12 am
by Ted.
guy smiley wrote:
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.

Exactly what I was hoping for, a concise, easily understood summary I can quote in the office.
Absolutely.

"What he said". :nod:

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 3:44 am
by Bokkom
Ted. wrote:
guy smiley wrote:
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.

Exactly what I was hoping for, a concise, easily understood summary I can quote in the office.
Absolutely.

"What he said". :nod:
:thumbup: PR to the rescue...again.

Mind you, by the time I've reached the office, there will be some slight modifications, I fear. :?

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 11:26 am
by A5D5E5
Ted. wrote:
A5D5E5 wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
The new bit is "just" engineering I think. It is certainly spooky action at a distance - but great as he was, Einstein was (seemingly) wrong about it.
Didn't he lose a wager, or some such, or had he karked it before it was confirmed in the 60's?

Could this phenomenon, just possibly, lead to teleportation?
If you mean "Standing on a circle with Spock and the unnamed bloke who is obviously going to die, going all wavy and then reappearing on an obviously fake alien planet" type of teleportation then no. Entanglement is a purely quantum mechanical effect.

If you mean "Transferring some quantum mechanical information about a particle and using that to replicate the quantum state of that particle some distance away" type of teleportation then it has already been in the "can do" box for about 25 years. It is pretty disappointing though compared to Star Trek - still limited to the speed of light and you essentially need to visit the chosen destination first to set up the "pathway".

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:12 pm
by Uthikoloshe
The Numberphile guys will have a work around.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:37 pm
by London_Lurker
A5D5E5 wrote:
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.
Einstein had a gift for making great discoveries by getting things wrong.
Einstein's field equations. Stick in a Lambda, ditch the lambda... now it seems we've got the lambda back (dark energy term...). I'm a mathematician so tend not to be very hot on the physical interpretations but the maths behind QM, QFT and general relativity is fascinating.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:39 pm
by London_Lurker
guy smiley wrote:
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.

Exactly what I was hoping for, a concise, easily understood summary I can quote in the office.
Sad thing is I thought that was pretty concise :(( .

Its like when I write a paper and my PI/boss C&Ps 80% of what I've written into the supporting information.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:44 pm
by A5D5E5
London_Lurker wrote:
A5D5E5 wrote:
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.
Einstein had a gift for making great discoveries by getting things wrong.
Einstein's field equations. Stick in a Lambda, ditch the lambda... now it seems we've got the lambda back (dark energy term...). I'm a mathematician so tend not to be very hot on the physical interpretations but the maths behind QM, QFT and general relativity is fascinating.
That is exactly what I had in mind - if the cosmological constant turns out to be dark energy then it would be a remarkable discovery via an unorthodox route.

The maths is utterly wonderful - it is what got me interested in these subjects long before the sheer wonder of what they say about the world grabbed me.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:47 pm
by London_Lurker
A5D5E5 wrote:
London_Lurker wrote:
A5D5E5 wrote:
Einstein had a gift for making great discoveries by getting things wrong.
Einstein's field equations. Stick in a Lambda, ditch the lambda... now it seems we've got the lambda back (dark energy term...). I'm a mathematician so tend not to be very hot on the physical interpretations but the maths behind QM, QFT and general relativity is fascinating.
That is exactly what I had in mind - if the cosmological constant turns out to be dark energy then it would be a remarkable discovery via an unorthodox route.

The maths is utterly wonderful - it is what got me interested in these subjects long before the sheer wonder of what they say about the world grabbed me.
:thumbup: :nod:

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:48 pm
by A5D5E5
London_Lurker wrote:
guy smiley wrote:
London_Lurker wrote:
Torquemada 1420 wrote:
A5D5E5 wrote:I'm not 6roucho (nor even close), but I'll have a go at explaining this.

Quantum entanglement creates a pair of particles that "know" exactly what the other is doing - even when they are separated (in this case by a very long distance). This knowledge exchange happens instantaneously (seemingly - certainly much, much more quickly than the speed of light) [but as information can't be transmitted by this mechanism, it doesn't break the rules around relativity and the speed of light which strictly apply to information transmission].

I think what this new announcement is about is using entangled particles as a way to detect if somebody without the appropriate "key" is trying to access the encrypted message. There is a process called decoherence where particles "lose" their quantum mechanical properties (opening the box and looking at the cat for example). This seems to be the way that the encrypted information is destroyed if an unauthorised person tries to read it.

The big deal is the sheer distance over which the particles are separated - an engineering masterpiece by the looks of it.

As to how that is all done - you will need to ask somebody with a nobel prize in physics.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?
Yes.

The basic postulates of schrodinger flavoured non-relativistic quantum mechanics that connect the mathematical theory to observable reality include:

(i) all the information you can get about a quantum system is described mathematically in its wave function (this gives a complex number for every possible state the quantum system could be in if observed),
(ii) that every observation of a quantum system corresponds to a mathematical object called an operator (this is something that maps wave-functions to other wave-functions), and
(iii) the chance you actually observe something is proportional the amplitude of complex number that possibility was given by wave function.
(iv) once you observed something the wave function is "collapsed" and now assigns 100% probability to the observation (technically any possible distinct observable value is an eigenvalue of the observation operator and the wave function collapses to become the associated unique eigenfunction within the Hilbert space you've constructed to understand the quantum system mathematically).

Einstein (and Podolsky and Rosen in Physical Review vol. 47 1935) noticed in the standard maths of QM that it was possible to have two connected quantum systems (called I and II) that get their joint wave-function, you let them separate so they are not interacting (basically no distance term exists in the equations), observe some stuff about the first system (which collapses the wave function), and for the collapsed wave function to specify that the other system is now in the eigenfunction state for some definite measurements (lets say for quantities P and Q). Basically, QM allowed observing system I to make the observation of system II definite:
EPR in 1935 wrote: This makes the reality of P and Q depend on the process of measurement carried out in the first system, which does not disturb the second system in any way. No reasonable definition of reality could be expected to permit this.
Except that not only does reality permit this... you can actually demonstrate this mad brain bending shit! This effect is what we now call quantum entanglement.

My understanding is that the chinese quantum security mechanism doesn't make uncrackable security but rather it makes it impossible to read (i.e. observe and collapse its quantum state) without that observation being detected.

Exactly what I was hoping for, a concise, easily understood summary I can quote in the office.
Sad thing is I thought that was pretty concise :(( .

Its like when I write a paper and my PI/boss C&Ps 80% of what I've written into the supporting information.
It was concise ... for anyone with a working knowledge of Hamiltonians, partial differential equations and vector spaces.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:53 pm
by London_Lurker
guy smiley wrote:
London_Lurker wrote:
Sad thing is I thought that was pretty concise :(( .

Its like when I write a paper and my PI/boss C&Ps 80% of what I've written into the supporting information.
Actually I followed it ok, roughly speaking. I'm a layman with this stuff. Wish I'd followed it from school to uni to be honest, it's fascinating and I was always good with abstract stuff and maths. Your summary was good. I was being a smartass.
Cheers! Anyway, I better log off and get back to the abstract stuff.

Re: China, entangled photons and the hackproof net

Posted: Tue Jun 20, 2017 12:59 pm
by Torquemada 1420
guy smiley wrote:
Exactly what I was hoping for, a concise, easily understood summary I can quote in the office.
:lol:

Bohm's work on this stuff was fascinating.