This article sounds important, but I don’t know enough to know if it is:
"Teleportation Across Calgary Marks ‘Major Step’ Toward Creation of ‘Quantum Internet’ "
Two questions:
Can you explain this article to me in short words and simple concepts?
How close are we to “Beam me up” ?
Thanks!
It’s not really teleportation as you’re thinking of it, it’s just a catchy term for this phenomenon.
“Although the name is inspired by the teleportation commonly used in fiction, there is no relationship outside the name, because quantum teleportation concerns only the transfer of information. Quantum teleportation is not a form of transportation, but of communication; it provides a way of transporting a qubit from one location to another, without having to move a physical particle along with it.”
And quantum “teleportation” is useful for some proposed data security schemes, since it’s more tamper-resistant than classical information: If you intercept a classical message, you can make a copy of it for yourself to analyze at your leisure while still sending the message along to its original recipient, but if you try the same thing with quantum information, then the intended recipient will know that someone’s been snooping.
The problem is that it’s devilishly tricky to get it to work, especially over long distances where most of the route isn’t in a precisely-controlled laboratory. So that’s what they’re working on in Calgary. Get it to work over long enough distances (like, those covered by the classical Internet), and it would be a lot more useful.
False advertising by physicists. Another example is “invisibility cloaks.” It’s done deliberately to make the work sound more exciting than it is.
Not exactly false advertising. Quantum teleportation is indeed just the transfer of information, but it’s quantum information. It’s not like ordinary information, because ordinary information is predetermined and can be copied. You can’t “copy” a qubit in the classical sense because observing it collapses the wave function. If you can move a qubit from point A to point B, there’s a real sense in which the original wave function has been been teleported without being affected by observation.
It’s rarely the physicists themselves that write the press releases, but rather the university or institution public relations division. Researchers can get notoriously cross about how their own universities play up their research.
From the sparse information in the article.
It seems that the experimenters had two particles separated by several kilometers. An action from a third location, supposedly influenced one of the particles. Which may have influenced the other particle without actually being connected to to the other one.
For instance. Human twins are in separate places. You punch one in the nose. Both get nose bleeds.
But…
Of course the article is not too detailed. The science is very complex. On many complex levels. I am still on the fence about quantum entanglement. And the term quantum is tossed about a bit loosely as well. Though this experiment is specifically about it.
But you still have to wait for the entangled particles to separate at light speed or less. Maybe we need to design a pair of quantum entangled, quantum entangled particle generators? Or generate a constant stream of entangled particles, like an entangled carrier wave.
The article is a little unclear but the basic idea of the experiment is that Alice wants to send a piece of quantum information (a qubit) to Bob a few kilometres away, but rather than sending it directly to Bob she sends it to a midway point between them where it is ‘teleported’ to Bob.
How this is done is that Bob specially prepares an entangled pair of photons and sends one to the midway point and keeps hold of one, meanwhile Alice sends the photon with the qubit that she wants to be teleported to the midway point. At the midway point the photons interact, are measured and discarded. The result of the measurement can then be sent to Bob by a classical communication channel (in the actual experiment fibre optics are used, but it could easily be a carrier pigeon, semaphore, etc.), which in effect gives Bob a very simple set of instructions to reconstruct the qubit that Alice sent to the midway point (with the photon that he kept).
Whilst the actual experimental set-up is pretty complicated, in the scheme of theoretical physics, the underlying theory is relatively simple.
There’s nothing to be on the fence about quantum entanglement I’m afraid. Whilst in the historical development of QM it was a little obscured for various reasons, it actually comes from the most basic principles behind QM and has been demonstrated experimentally many times (in fact this experiment is also a demonstration of entanglement).
A google search seems to return that no experiments have fully closed the 3 loopholes and succeeded . So I am still not totally convinced.
Still pretty far away. The linked article isn’t really about Star Trek style transporters, but then that might be a good thing because those are pretty nearly impossible, not because of the technology required, but because of the bandwidth.
I assume you’re talking about loopholes in Bell-type experiments here. Now, first of all, that’s a different concept: while violating a Bell inequality necessitates entanglement, not all entangled states violate a Bell inequality. In particular, entanglement can be detected independently of Bell inequality violation, such as via the use of so-called entanglement witnesses, which are basically measurements that you can carry out on a quantum system such that a specific outcome (by convention, a negative one) uniquely certifies the presence of entanglement. Such experiments have been carried out, and have demonstrated the presence of entanglement beyond reasonable doubt.
Now, for Bell test experiments, the two major remaining loopholes—the separation and detection loopholes—, which had up until last year only been closed in separate experiments, have now been simultaneously closed in experiments by three different experimental groups (see here, here, and here).
There exists still at least one logical possibility to evade the above conclusion, which is the ‘grand conspiracy’: if the choice of measurement of an experimenter isn’t free, but pre-determined in precisely such a way that the actual measurement statistics become biased towards certain outcomes, then a Bell inequality violation may occur. This is, in a sense, a metaphysical possibility that can never be ruled out conclusively—not least because it makes science, essentially, impossible: for any experiment, you can never tell whether you observed the actual distribution of outcomes, or were just constrained to observe some sub-sample biased towards certain outcomes. Consequently, your observations may not tell you anything about the actual distribution.
Furthermore, additional to its metaphysical baggage, such a conspiracy is also less explanatory than just assuming that QM works: for a given Bell inequality, QM predicts a specific value, while the grand conspiracy could in principle yield any value (compatible with the algebraic constraints) whatsoever. Thus, QM explains more while assuming (vastly) less.
To hear what one of the physicists says, goto Home | Quirks & Quarks with Bob McDonald | CBC Radio, scroll down to “Is Quantum Teleportation really here? Sorta, kinda…” and click on the listen button. But the quoted title tells you something.
Thank you for all of the comments. Still not sure I completely understand, but a bit better.