71–80 of 219 posts
I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…
Earlier quoted context omitted.
> Teleportation is not possible. Quantum teleportation is the transmission of the exact state of a photon from one place to another. Still, even this happens at less than the speed of light. Otherwise it would violate causality. Maybe I'm remembering my QED special topics class incorrectly, but I thought the state teleportation is believed to be instant. The problem is to extract the state information, the transforma…
So many advancements in physics have been the result of a smart person abandoning some "law".
I understand the temptation to think that every "law" is just waiting to be broken, but I can easily read the same data and come to the opposite conclusion about the strength of our current "laws".
I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…
http://blog.rongarret.info/2014/12/quantum-teleportation-dem...
(Also submitted to HN: https://news.ycombinator.com/item?id=12549728)
10 picoseconds is "one millionth of one millionth of a second"? Damn it, I must have been misunderstanding engineering units all my life.
"or one millionth of one millionth of a second"
Not satisfied with asking me to subscribe to their newsletter before I've even read one article, this site _also_ popped up a request that I allow them to send me desktop notifications. Do people actually fill these things out? Why does ScienceBulletin think I might even want these things?
I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…
It's not "fairly certain", it's absolutely certain. http://blog.rongarret.info/2014/12/quantum-teleportation-dem... (Also submitted to HN: https://news.ycombinator.com/item?id=12549728 )
The premise upon which the idea that it is impossible is based is an axiom:
https://en.wikipedia.org/wiki/Wightman_axioms#W3_.28local_co...
Not a conclusion from data or other, simpler premises. It is an axiom that has nice consequences and is generative of much that describes our observations, but it remains an untestable assumption.
I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…
It's not "fairly certain", it's absolutely certain. http://blog.rongarret.info/2014/12/quantum-teleportation-dem... (Also submitted to HN: https://news.ycombinator.com/item?id=12549728 )
Is there a rule for describing the entanglement of the resulting constituent particles with the pre-existing particle?
If it's possible to actually break entanglement(so that measurement of a qubit resets to 50%-50% random), it seems like you could transmit information faster than light by preparing a 100%-0% distribution with quantum gates and destroying the particles. Then the first particle would change the distribution of its measurements. And so you could prepare 1000 qubits and measure them every hour, waiting to observe a change.
I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/…
Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.
A measurement is an interaction of the quantum system under test/consideration with another system / component that is classical (non-quantum, e.g. big).
Why? Because otherwise we would have to specify the exact details of every measurement device. Model number wouldn't be enough. What is the full quantum state of photon detector with its enormous number of atoms? Unusable.
Entanglement isn't some spooky thing. In fact it's required for us to be able to measure anything. The measuring device's quantum state must become entangled with the quantum system it's measuring. We can't really consider each one separately, but we try anyway, and with great success if we do it right.
I like James Binney's take on this: QM is adult physics. It's an admission that when you measure something, you disturb it. When you measure something really small, you disturb it alot, and can't idealise that away as you can for classical macroscopic systems.
He explains it better than I can: https://www.youtube.com/watch?v=NKPI_wurNlo&t=37m20s
EDIT> I should add that for a measuring device, we want it to be correlated to the system under test. I.e. I could make a thermometer that always read 5C (uncorrelated to environment), but it would be a bad thermometer. Quantum entanglement is how this correlation is set up. But it means that now the future evolution of the quantum system depends on the (unknown to us) exact state of the measuring device.