> the measurement on the first particle injects quantum energy into the system
That set off my bogometer. What is "quantum energy"?
The devil is always in the details, but I have yet to see a popular account of anything having to do with entanglement that didn't completely ignore the fundamental fact that entanglement and measurement are the same physical phenomenon. Once you realize that most of the mysteries simply evaporate.
So Mermin was on the right track, but he didn’t get it quite right: not only is the
moon is not really there when nobody looks, but it isn't really there even when
you do look! "Physical reality" is not "real", but information-theoretical reality is.
We are not physical entities, but informational ones. We are made of, to quote
Mermin, "correlations without correlata." We are not made of atoms, we are made
of (quantum) bits. At the risk of stretching a metaphor beyond its breaking point,
what we usually call reality is really a very high quality simulation running on a
quantum computer.
This is a very counterintuitive view of the world, but the mathematics of Quantum
Mechanics tell us unambiguously that it is correct, just as the mathematics of
relativity tell us that there is no absolute time and space. Entanglement, far from
being an obscure curiosity of QM, is in fact at its very heart. Entanglement is the
reason that measurement is possible, and thus the reason that the Universe is
comprehensible.
There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature. Niels Bohr
Reality is not "running on a quantum computer" it is just that QM is the best description we have of what we can observe of the external world.
I'd be wary of it, I haven't read the whole thing but it seems suspicious, least of which is that he comes off as if he fully understands QM.
I only know so much about QM, but I do know that no one fully understands it, and that in attempting to sound deep, the author of this paper misattributed a classic Zen koan to Douglas Hofstadter.
That paper has been reviewed at one time or another by at least a dozen card-carrying physicists, including Jeff Kimble and John Preskill at Caltech (who are the ones who actually helped me figure all this stuff out). Reactions range from, "Oh my God, what a revelation!" to "Duh. Everybody already knows that." But I have yet to encounter anyone who knows what they're doing who thinks it's wrong.
"There's a widespread belief that quantum mechanics is supposed to be confusing. This is not a good frame of mind for either a teacher or a student. Complicated math can be difficult but it is never, ever allowed to be confusing."
I got it from GEB. Hofstadter doesn't attribute it, so I just assumed it was original with him. (And frankly I'd be surprised if you found any references to Zen Master Zeno prior to GEB.)
Measurement and entanglement isn't quite the same physical phenomenon. Measurement necessarily involves a certain kind of entanglement, but not every entanglement is a measurement (or, if it is, then you've chosen a particularly confusing definition of measurement tantamount to any interaction between systems with substantial uncorrelated degrees of freedom.)
That's right, not all entanglements are measurements. But all measurements are entanglements. They are the "same" in the same sense that, e.g. heat and motion are the "same", or light and radio waves are the "same". Measurement can be understood in terms of entanglement. They are not distinct physical phenomena.
I couldn't help but laugh at this unfortunate wording "He gives the example of a string of entangled ions oscillating back and forth in an electric field trap, a bit like Newton's balls."
The article seems to suggest it's impossible to communicate faster than light speed using entanglement b/c they need to know a bit of information at the sender's side which can't be sent using the entanglement phenomenon itself.
That's something I'd like to understand better..
Is it really impossible to distinguish between an 'On' state and an 'Off' state at the receiver's end without this piece of information? Is it our ability to measure the observation that hinders this or is this a law of physics that will 'never' be broken?
To answer with an example, a lot of these experiments entangle the "spin" property of two particles. In a two-state system such as spin up and spin down, it is tempting to call, say, "up" 1 and "down" 0, but you won't get too much use out of that. What you'll often read is that when you take two entangled particles and take them to opposite ends of the room (or the universe), and you measure your particle as having spin up, you know at once that the other particle must have spin down. That is a function of conservation of angular momentum, and has a very intuitive classical analog.
Before you make a measurement, though, the particle you measured is in a combination of both states. It's not that you don't know which it is; it really is neither (to the best of modern interpretations). If it has equal probability spin up or down, you are equally likely to measure either one. Once you measure it once, though, and get either up or down, if you immediately measure again, you'll get the same result. That's the hastily abused "collapsing the wave function." If you consider the wave function of the particle with regard to its spin states to be representative of a probability distribution of measuring either state, once you measure it, the state you measured has probability one and the rest have probability 0. The new wave function is just a delta, and has been collapsed.
Now to get on with answering your question-- you've not only collapsed this particle's wave function; you've collapsed the other one's too.Instantly. So, you know what the other guy taking measurements on his will measure. What you have no control over is the information content itself. You can't spin your particle so the other one spins in the opposite way. It just doesn't work that way. Information propagation in relativity comes with a caveat-- causal information travels no faster than the speed of light. Non causal information can travel as fast as it likes. It's not spooky action at a distance because it's not really action. Nothing's different in the tangible world as a result of it, which is why you can't use it to send bits. If you're really interested, I recommend Griffiths' Intro to Quantum Mechanics. It was used in all of my related courses, and the author has a way with the inexplicable.
My impression was that relativity was preserved because the two particles are effectively 0m apart, functioning as the same particle.
Kind of like a VPN for elementary particles; the remote client and its presence on the local network are the same thing, if I'm not stretching my computer-physics analogies too far.
"Certain phenomena in quantum mechanics, such as quantum entanglement, appear to transmit information faster than light. According to the No-communication theorem these phenomena do not allow true communication; they only let two observers in different locations see the same event simultaneously, without any way of controlling what either sees."
let two observers in different locations see the same event simultaneously [...]
So ... what if observer B does nothing while observer A (a long, long ways distant) measures something. Can B then "see" the corresponding wave function collapse, thereby knowing that A took a measurement?
What I'm working towards here is not caring about the measurement outcome, but rather knowing that a measurement took place, and using that as "information". If you have enough entangled quanta don't you then have a primitive serial line?
It should be obvious here that I'm not very familiar with QM. Just wondering.
I thought that the whole point was that you invariably change the state of a quantum particle just by observing it. The particles are so small that just waiting for a photon to reflect off of it so you can observe it changes its state.
Working for a test and measurement company I would be curious to see the non generalized version of this report. One with tests and measurements, possibly some data and techniques.
So, the summary doesn't make this clear, and if you were to use the colloquial definition of teleportation the title of the article would simply be wrong.
Quantum teleportation is nothing like teleportation in shows and movies. The big difference is that you have to already have something on the other side. In other words, you can't teleport a rat to mars because there is no rat on mars. Yet. :-p
Further, that rat would have to be entangled with another rat on mars, not something trivially accomplished. At least that's my understanding of it.
Here's an article on QM teleportation that's easier to grok (although not about teleporting energy specifically):
That set off my bogometer. What is "quantum energy"?
The devil is always in the details, but I have yet to see a popular account of anything having to do with entanglement that didn't completely ignore the fundamental fact that entanglement and measurement are the same physical phenomenon. Once you realize that most of the mysteries simply evaporate.
http://www.flownet.com/ron/qm.pdf