The first step in demystifying quantum "teleportation" is to stop calling it "teleportation", which is a term that is made to be misleading.
The second thing to do is to stop reading any article that ever says anything remotely resembling, "the photon/atom/whatever was teleported..." since that is a flat-out falsehood that only a ignoramus or a liar would publish.
No photon, no atom, no thing has ever been "teleported" nor ever will be. Only the quantum state gets "teleported", and the quantum state most decidedly does not have the ontology of a "thing". That is why the quantum world is so weird.
Quantum "teleportation" ought to be called something like "entanglement transfer", which has the advantages of being a) fairly accurate and b) hard to use in the misleading and dishonest ways "teleportation" gets used.
> The first step in demystifying quantum "teleportation" is to stop calling it "teleportation", which is a term that is made to be misleading.
> No photon, no atom, no thing has ever been "teleported" nor ever will be. Only the quantum state gets "teleported", and the quantum state most decidedly does not have the ontology of a "thing".
I used to think the same thing as you, but if you accept quantum mechanics as complete and accurate, then the quantum state describes the totality of the system. There is nothing more than the state -- no other hidden variables.
So it comes down to the philosophical question: if you can make a perfect copy of something, except you have to delete the original version in the process (see the no-cloning theorem), is the new version the original "thing"? I would argue yes, it is. It's completely indistinguishable in every way.
(Now do I actually believe quantum mechanics is complete? I'm not sure I do. But if I assume that it is, then quantum teleportation is really teleportation.)
Asher Peres, one of the coinventors of teleportation, had an amusing story (with a serious subtext) about the question of what is teleported: "Later, when a newsman asked me whether it was possible to teleport not only the body but also the soul, I answered “only the soul.” Even that is a gross oversimplification."
In teleportation experiments to date only some degrees of freedom are teleported. So it doesn't usually make a whole lot of sense to say "the atom" was teleported. Rather, it'll just be the quantum state associated to nuclear spin states, or electronic degrees of freedom, or whatever.
Cool article. I wonder what the maximum number of degrees of freedom that has been teleported so far is. I also wonder if it gets exponentially harder to transmit larger and larger quantum states (the only reason I posit this is because it always seems like Nature prohibits us from doing all kinds of cool things in an exponentially hard way).
"when Bob receives Alice’s bits, he uses that information to apply one of four transformations to his photon. It is Bob’s action that changes his photon’s state into the state of Alice’s original photon. And that is the only time that Bob’s photon changes state."
I disagree with this particular bit. The state of Bob's photon changes exactly when Alice does her measurement [1]. Why? The state of a photon is given by 2 real numbers (infinite bits). Bob receives 2 bits of information from Alice so his 1/4 operation can't change the state of the photon to an arbitrary state.
The 'magic' does happen when Alice measures her state. After her measurement Bob's photon is in one of four possible states, which are the same up to 2 swaps. The 2 bits of information are needed to find out which swaps to perform. This swapping step nicely prevents faster-than-light travel.
[1] Caveat. In a relativistic universe, ordering of events depends on the frame of reference. All arguments carry through when this is taken into account.
Edit: I should explain how this saves relativity. No measurement (weak or strong) can distinguish which pre-swap-state Bob has. You can try to be clever and ask Alice to teleport millions of photon states to Bob. But that doesn't help either because each of the four states are equally likely in the whole ensemble. So you need 2 bits of information per teleported photon state to get the correct final state each time.
> The state of Bob's photon changes exactly when Alice does her measurement [1].
No, it doesn't. If it did, then this would lead to faster-than-light communication. The whole concept of "exactly when Alice does her measurement" isn't even well defined!
> Why? The state of a photon is given by 2 real numbers
Actually they are complex numbers. But this part of your point is valid nonetheless.
> The 'magic' does happen when Alice measures her state.
No, the "magic" happens when the entangled pair is first produced. Alice's measurement changes nothing on Bob's side.
Ron attributes to malice here that which can be more easily explained by indifference. I think Physicists have largely given up on trying to correct media's portrayals of QM as they either see it as not being important or because they see it as tilting at windmills.
The majority of experts I know feel like it's futile to try and correct the media's representation of their field. I think QM has it doubly hard as it has all the issues of other technical field, while suffering from both the problem of its ontology being foreign to the lay-person and certain key points of its ontology are still debated within the field.
I think you're on to something, but it goes even farther than that.
I'm sure a lot of scientists don't mind media-hyped and somewhat inaccurate coverage of science news because it's actually interesting to the layperson. The reality is that the general population is pretty blasé about even fluff science reporting - let alone accurate reporting.
So a little hype, even if inaccurate, probably goes a long way towards getting people interested in science. And that's a good thing for a) producing future scientists and b) securing funding.
In general I agree with you. But this case is different. This is not the popular press publishing this false information, it's NASA itself. I think they ought to hold themselves to a higher standard.
I guess I mentally put whatever part of NASA published this in the same category as university PR departments. You almost certainly know more about how NASA works than I do.
Your analogy is not wrong, but I think university PR departments ought to be held to a higher standard too. If a university PR department issued a press release that denied anthropogenic climate change or evolution there would be an uproar. Why should it suddenly be OK to play fast-and-loose with the truth just because the topic is physics rather than biology or climate science?
I had to think a bit before responding, but university PR departments regularly report questionable findings. The two you picked are obviously highly politicized topics, so it's obvious why that would cause an uproar.
I agree that they ought to be held to a higher standard, but I think that the motivation of scientists for not doing so is more out of apathy, and less out of a desire to seem more mysterious.
The second thing to do is to stop reading any article that ever says anything remotely resembling, "the photon/atom/whatever was teleported..." since that is a flat-out falsehood that only a ignoramus or a liar would publish.
No photon, no atom, no thing has ever been "teleported" nor ever will be. Only the quantum state gets "teleported", and the quantum state most decidedly does not have the ontology of a "thing". That is why the quantum world is so weird.
Quantum "teleportation" ought to be called something like "entanglement transfer", which has the advantages of being a) fairly accurate and b) hard to use in the misleading and dishonest ways "teleportation" gets used.