Re: China, entangled photons and the hackproof net
Posted: Mon Jun 19, 2017 3:08 pm
guy smiley wrote:
ANU’s
guy smiley wrote:
ANU’s
Might I stop it there? What about observation effect?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.
Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
MerciA5D5E5 wrote: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.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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.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.
Einstein had a gift for making great discoveries by getting things wrong.London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
Give Mad Scientist a shout.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
Didn't he lose a wager, or some such, or had he karked it before it was confirmed in the 60's?A5D5E5 wrote: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.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
Absolutely.guy smiley wrote:London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
PR to the rescue...again.Ted. wrote:Absolutely.guy smiley wrote:London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
"What he said".
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.Ted. wrote:Didn't he lose a wager, or some such, or had he karked it before it was confirmed in the 60's?A5D5E5 wrote: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.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
Could this phenomenon, just possibly, lead to teleportation?
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.A5D5E5 wrote:Einstein had a gift for making great discoveries by getting things wrong.London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
Sad thing is I thought that was pretty concise .guy smiley wrote:London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
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.London_Lurker wrote: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.A5D5E5 wrote:Einstein had a gift for making great discoveries by getting things wrong.London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
A5D5E5 wrote: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.London_Lurker wrote: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.A5D5E5 wrote:
Einstein had a gift for making great discoveries by getting things wrong.
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.
It was concise ... for anyone with a working knowledge of Hamiltonians, partial differential equations and vector spaces.London_Lurker wrote:Sad thing is I thought that was pretty concise .guy smiley wrote:London_Lurker wrote:Yes.Torquemada 1420 wrote:Help. What is the new bit here? This is Einstein's "spooky actions at distance" from the '30s?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.
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:
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.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.
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.
Its like when I write a paper and my PI/boss C&Ps 80% of what I've written into the supporting information.
Cheers! Anyway, I better log off and get back to the abstract stuff.guy smiley wrote: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.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.
guy smiley wrote:
Exactly what I was hoping for, a concise, easily understood summary I can quote in the office.