is-quantum-communication-faster-than-the-speed-of-light?

nsaspook

Joined Aug 27, 2009
9,730
The article is classic BS marketing hype for a maybe product that hints (with not Science, Physics or Math explanation) it can do the impossible. It's no wonder they bailed on building and selling the first quantum network in the U.S.
A link from the article: https://www.forbes.com/sites/chador...ter-than-light-communication/?sh=7094760a3a1e

https://www.forbes.com/sites/starts...-speed-of-light-nothing-does/?sh=18eb9e887c3c
But it also helps expose how physicists have managed to exploit a many-particle system in order to create the illusion of something traveling faster than light: a result which gets misreported every few years in the popular media.
No, no , no. FTL communications would break causality in a thousand horrible ways. Causality is more elemental than time or the speed of light.
https://arxiv.org/pdf/quant-ph/0310131.pdf
 
Last edited:

Thread Starter

Wendy

Joined Mar 24, 2008
22,841
That is according to current theory, maybe we will come up with new theories. This is a time will tell problem.
 

nsaspook

Joined Aug 27, 2009
9,730

Papabravo

Joined Feb 24, 2006
18,422
No, No, No. I'm sick of that cop out for bad science (the shallow claim in the article is not even bad science, it's not even wrong). Any new theory MUST be compatible with current theory about causality. At least in this universe, it's not happening.

http://curious.astro.cornell.edu/ab...-faster-than-light-communication-intermediate
I'm in substantial agreement here. There is nothing that I am aware of that would support the notion that such a thing was possible.
 

Thread Starter

Wendy

Joined Mar 24, 2008
22,841
Last I heard quantum entanglement was pretty much instantaneous, which suggests there are some footnotes to be added to our understanding of a new universe. I am not sure of this, but I believe experiments have borne this out. while there are a lot of experiments that verified quantum entanglement, none have set the speed limit for it yet. you can bet scientists are working on this problem right now. We have no clue what the linking mechanism of quantum entanglement is.
 
Last edited:

nsaspook

Joined Aug 27, 2009
9,730
Last I heard quantum entanglement was pretty much instantaneous, which suggests there are some footnotes to be added to our understanding of a new universe. I am not sure of this, but I believe experiments have borne this out. while there are a lot of experiments that verified quantum entanglement, none have set the speed limit for it yet. you can bet scientists are working on this problem right now. We have no clue what the linking mechanism of quantum entanglement is.
I can't make excused for the OP article. You heard wrong, there are no footnotes here. It's not instantaneous or allows for FTL communications.
https://www.quantamagazine.org/quantum-leaps-long-assumed-to-be-instantaneous-take-time-20190605/
The experiment shows that quantum jumps “are indeed not instantaneous if we look closely enough,” said Oliver, “but are coherent processes”: real physical events that unfold over time.

C in not a limit for light speed, C is the limit for causality. We don't need a loop-hole for speed, we need a loop-hole for causality.
 
Last edited:

Thread Starter

Wendy

Joined Mar 24, 2008
22,841
There might actually be a loophole. In the form of the multiverse.

You do know I am stirring, right?
 

nsaspook

Joined Aug 27, 2009
9,730
There might actually be a loophole. In the form of the multiverse.

You do know I am stirring, right?
I know the loopholes too.

From my second reply on this thread:
" At least in this universe, it's not happening."
Yes, it's Science-Fiction.
 
Last edited:

MrSalts

Joined Apr 2, 2020
1,762
A company I worked for leased printers from Ricoh. Their service technician always introduced himself as a Service Engineer. He would come in and efficiently service a printer then spend the next hour hitting on the admin who sat near the printer. His mode of operation was to tell the admin about all of his special scientific knowledge including access to secrets of science that nobody else seems to know - including time travel, biological impossibilities, and other weird things from sci-fi movies. Needless to say, it didn't work. I hoped he would somehow find a Trekkie or other sci-fi cosplayer to give home some companionship and he could stop wasting hours of admin time during every visit. And, unfortunately, the time of everyone else's time within earshot because the lines were just such a car-wreck that nobody could stop listening when he got into his groove.
 

Thread Starter

Wendy

Joined Mar 24, 2008
22,841
I have to wonder if he tried mansplaining something to her. I had it happen with me once, the guy was feeding back an exclamation I had just given him. He wasn't doing it because he was making clear he had the point. He actually thought he was he was teaching me something.

So if it does happen, does this mean we're in another universe?
 

MrSalts

Joined Apr 2, 2020
1,762
I have to wonder if he tried mansplaining something to her. I had it happen with me once, the guy was feeding back an exclamation I had just given him. He wasn't doing it because he was making clear he had the point. He actually thought he was he was teaching me something.

So if it does happen, does this mean we're in another universe?
I don't think the admins were too interested in saying anything to him. They just wanted him to leave so they could go wash their hands in an attempt to remove all of the weird from their space and move on with their day.
 

nsaspook

Joined Aug 27, 2009
9,730
I have to wonder if he tried mansplaining something to her. I had it happen with me once, the guy was feeding back an exclamation I had just given him. He wasn't doing it because he was making clear he had the point. He actually thought he was he was teaching me something.

So if it does happen, does this mean we're in another universe?
No.

The article you posted in a science and Physics topic was effectively discredited by the company that wrote it. Both are just as likely to be factual. ;)
 

DickCappels

Joined Aug 21, 2008
8,710
I think this relies on changing the spin of one particle and observing the spin on another particle. The problem seems to be that once you "look" at an entangled particle and measure its spin, it have that spin for then on. How would you know if somebody tried to flip the spin on the entangled particle, since you have stuck it in a permanent state?

Somebody check me...
 

nsaspook

Joined Aug 27, 2009
9,730
I think this relies on changing the spin of one particle and observing the spin on another particle. The problem seems to be that once you "look" at an entangled particle and measure its spin, it have that spin for then on. How would you know if somebody tried to flip the spin on the entangled particle, since you have stuck it in a permanent state?

Somebody check me...
Yes. The problem is knowing what the spin means (even if the spin changing exchange is FTL) in the information sense unless there was prior knowledge via a classical communications channel so we can have an 'agreement'.
https://www.aliroquantum.com/blog/quantum-entanglement-communication
Does quantum entanglement violate the speed of light?
No. While quantum entanglement can cause particles to collapse instantaneously over long distances, we can't use that to transport information faster than the speed of light. It turns out entanglement alone is not enough to send data. For example, quantum teleportation uses entanglement to transfer quantum states across long distances. However, teleportation requires sending a classical bit in addition to the entangled qubits. So, while the entanglement operates instantaneously, the information transfer is limited by the speed of the classical information, which travels at the speed of light.
 

BobTPH

Joined Jun 5, 2013
4,906
A way it was explained to me a while back was like this:

Imagine you have a pair of gloves (left and right). You package them up and send the packages to two friends, instructing them not to open them yet. Then you instruct friend 1 to open his package. At that point, friend1 knows which glove friend 2 has instantly. But friend2 does not know until friend 1 communicates his result.

Bob
 

dcbingaman

Joined Jun 30, 2021
566
No, No, No. I'm sick of that cop out for bad science (the shallow claim in the article is not even bad science, it's not even wrong). Any new theory MUST be compatible with current theory about causality. At least in this universe, it's not happening.

http://curious.astro.cornell.edu/ab...-faster-than-light-communication-intermediate
'Causality' seems to have been blown out the window when quantum physics came along and found the probability of finding a quantum 'wave/particle' at a specific location is completely statistical and based on the square of the wave function. The reason it appears at a specific location has nothing to do with causality. There is no cause for it to be there, it literally has nothing to do with causality and everything to to with probability which is why we now know there is no way to know the future because quantum mechanics limits our knowledge of any system. It is also meaningless to talk about what a particle/wave is doing when we are not looking at it. Even worse we cannot even say that it 'exist' until we look. Even worse, when we perform an experiment to 'look' at such things, we alter them via our own observations.
Consider a radioactive atom. When it decays is only controlled by probability and there is no cause whatsoever for it decaying at any given specific point.
 
Last edited:

nsaspook

Joined Aug 27, 2009
9,730
It's not 'Causality' that's blown out by QM, it's determinism. There is cause and effect (quantum theory violations of local causality don't allow superluminal signalling. ) in QM because we have probabilistic causation from relativistic causality (influences/information do not propagate faster than the speed of light) instead of predictability or Newtonian causality. You can call it Correlation instead of Causality if you want but you still can't escape the light-cone of c for FTL communications using quantum physics.

For a radioactive atom there were definite circumstances that allowed unstable atoms to be created which then allows them to decay. Just looking at decay misses the causality of the unstable state of the radioactive isotope. We know the cause of radioactive decay, it's random in the exact time NOT arbitrary, that's why we can use carbon-14 to date things.
 
Last edited:

dcbingaman

Joined Jun 30, 2021
566
It's not 'Causality' that's blown out by QM, it's determinism. There is cause and effect (quantum theory violations of local causality don't allow superluminal signalling. ) in QM because we have probabilistic causation from relativistic causality (influences/information do not propagate faster than the speed of light) instead of predictability or Newtonian causality. You can call it Correlation instead of Causality if you want but you still can't escape the light-cone of c for FTL communications using quantum physics.

For a radioactive atom there were definite circumstances that allowed unstable atoms to be created which then allows them to decay. Just looking at decay misses the causality of the unstable state of the radioactive isotope. We know the cause of radioactive decay, it's random in the exact time NOT arbitrary, that's why we can use carbon-14 to date things.
That still leaves open the exact time that any specific atom of carbon-14 will decay. The exact time is not 'caused' by anything that any experiment has been able to demonstrate nor can we calculate or predict it. I agree that the statistical likelihoods obviously allow us to date things, but that is not quantum mechanics, that is classical mechanics, quantum mechanics involves single particles/atoms or relatively small numbers of them, not large quantities of them, that is not the issue. We 'know' the chances that a given C-14 atom will decay in any given time period, we know if not because of quantum mechanics but because of classical physics when we measure a large sample of say C-14 and find that 50% of it decays within an 'average' time period. (Actually no experiment like that has been performed, see second paragraph). But why a specific atom decays when it decays remains unknown and experimental evidence shows no cause for it. Thus currently experimental evidence suggest that when things happen does not require a cause. Thus the cause and effect relationship is not guaranteed nor demonstrated by actual experiments.
Actually for C-14 (or many similar atomic decays for that matter) it gets worse. No experiment has ever waited around the 12000 or so years to verify that 50% will decay in that time period, but have simply 'extrapolated' it from small numbers of decay, say 1%. I am not saying this extrapolation is 'wrong'. I would consider it correct but that is not in any way proven by a real experiment. But experimental evidence and its limitations should be pointed out. We are extrapolating the '12 thousand year' half life of C-14. It has never been experimentally verified. A lot of assumptions take place during experimentation. We assume decay rates have remained the same over time. Yet there is no absolute proof of that. We assume the 'constants' like the gravitational constant have actually remained 'constant' we need to recognize that these assumptions are not based on experimentation. Such long period experimentations have never been performed, yet we act like we 'know' and assume a lot of things that are most likely incorrect.
 
Last edited:

nsaspook

Joined Aug 27, 2009
9,730
That still leaves open the exact time that any specific atom of carbon-14 will decay. The exact time is not 'caused' by anything that any experiment has been able to demonstrate nor can we calculate or predict it. I agree that the statistical likelihoods obviously allow us to date things, that is not the issue. We 'know' the chances that a given C-14 atom will decay in any given time period. But why it decays when it decays remains unknown and experimental evidence shows no cause for it.
True but the randomness of the decay event timing doesn't violate the physics meaning of causality irt FTL communications or modify a past timeline. There's no easy way to predict what number comes up when rolling dice, does that break physics causality? "Caused" isn't restricted to deterministic processes. A probabilistic component in the process doesn't mean that it is "uncaused".
 
Top