Not to sound corny or clichéd, but...
"In English, Einstein!"
IOW, what's in it for us regular folks? I mean, quantum networks sound so super-high-tech, but will they mean we can download faster or what?
Researchers claim to have demonstrated how it is possible to move quantum information from individual sets of multi-partite entangled atoms to four entangled beams of light (previously they had only managed with two). In simple terms, this a a big step forward in information science because it paves the way toward quantum …
If a quantum computer with a large number of quantum bits can be constructed, it means that all cryptography based on a very large number with just two large prime factors becomes useless. This, because a quantum computer can simultaneously try all potential prime factors in a single operation (boggle), and (like magic) reveal the true ones. The impact of this on the internet as we know and use it should be obvious.
Quantum factorization has been demonstrated, with four qubits, revealing that 15 = 5x3 or 14 = 2x7. There are huge practical difficulties for increashing the number of qubits. There *may* also be some unknown physical constraint. If so, it represents new physics beyond what is known today.
Therefore if such a computer cannot be constructed or fails to work as predicted, this may tell us something extemely interesting about physics. I'd bet that this is the case. The alternative - that quantum computers of arbitrary complexity can actually work - is just too wierd for me to countenance.
By the way, if anyone reading this is working on quantum computing and actually makes the 1024-bit breakthrough which I suspect is physically impossible, you must immediately spam all details to everywhere you can think of. Otherwise you have put a billion-quid price tag on your head. That's what it would be worth to a government to keep it secret, or even just to suppress it. You'd be dead hours after they found out, if the secret was not well and truly out of the bag by then.
Quantum networks help you do better cryptography.
The first 3 slides in this PowerPoint presentation explain the problem and the quantum solution: http://iopscience.iop.org/1367-2630/4/1/346/fulltext
In brief (and in English), current cryptography relies on mathematical functions in order to work. Unfortunately this is not foolproof.
Quantum entanglement describes a situation where subatomic particles (electrons, photons, &c.) are inextricably linked in such a way that performing a measurement on one immediately alters properties of the other (cf. wiki Quantum Entanglement and be prepared for a headache).
Anyway, once two particles are entangled they can be separated by some distance and when one particle's state is altered the other particle's state alters /simultaneously/ (i.e. it appears to be faster than light and yes I know this isn't supposed to be possible, but there you go, it's a funny old world innit?).
This has something to do with cryptography because if, instead of using PGP or whatever, you use one of a pair of entangled particles to encrypt the document and the other to decrypt it you have an unbreakable system. Nothing (not even a quantum computer) can unencrypt the document without one of the entangled pair of subatomic particles.
So there you go.
Heads all in one piece?
Considering most boffins think coding is easy and all you need to build complex systems is Fortran (god help anyone that has to maintain the spaghetti hack code they produce) what will the future of quantum computing look like? Probably a handful of super bright people that actually know QM and software development will have to build tools/frameworks that will allow us mere mortal developers to write code for the new hardware (pretty much as happened with the first digital computers with first assembler then higher and higher languages). I know this is probably long after most of us retire but I look forward to the Quantum Computing in Nutshell Oreilly book.
Quantum "computers" will in all likelihood not evolve past serving as hardware devices within our lifespans. Sensors or encryption gear...at worst you might need to code a device driver to understand the output a quantum device provides.
The reality is that they are just too inherently unpredictable to "program" in the traditional sense. At least with our limited understanding so far…
I was totally baffled.
I still get excited over the fact that my iPad 'pings' with a new Email BEFORE my always connected Desktop Outlook client gets it.
How can the Email fly through the 3G network and reach it before the PC which is 10 yards from the exchange server.
Quantum displacements? pah!
@Charles 9:
The trouble with quantum theory is that it can't really be explained in English. The language of choice for your jobbing theoretical physicist is mathematics, and even that can't really "explain" what's going on in the quantum world. In fact some of quantum theory's pioneers came to the conclusion that it can never be "understood" because it is not something that *can* be understood, even in principle. That might be hard to fathom, but it does appear to be the case that the reality we commonly experience emerges as a thin veneer over principles and operations that defy rational analysis at the microscopic level.
To make some sense of this, we imagine there are such things as tiny "particles" called electrons that do stuff and interact with each other (digitally) by exchanging particles of light called photons. To make matters more exciting, nothing is ever in a definite state and electrons can be said to be "spinning" in both directions at the same time. Imagine all the letters in this paragraph cycling randomly through the alphabet, independently of each other. If this were a quantum mechanical paragraph, it wouldn't just be the collection of letters you see in front of you now: it would be a paragraph that contains *all* possible combinations of characters. One of the tricks that a quantum computer could do is decrypt an encrypted document by turning it into a quantum paragraph and mix it with another quantum paragraph that simultaneously contains all possible keys that you might use to decrypt the original document. Only one key is any good, but if you can detect a successful outcome you will do so straight away because that quantum jiggery-pokery cycles through all possibilities in literally no time at all. That would mean the end of SSL, for example.
Of course, electrons aren't really spinning in both directions at the same time: they don't spin - it's just a convenient label that physicists apply to give it some kind of meaning. Likewise, an electron is said to hop from one orbit to another, which makes it spit out a photon, which in turn gets absorbed by another electron (perhaps a billion light years away) which causes that electron to hop up to another orbit. But Einstein demonstrated that time stops for anything moving at the speed of light. Therefore, from a photon's perspective, it never ever actually comes into existence because it is absorbed as soon as it is created (even if it has to travel the length of the universe before that happens).
It's a bit rich to imagine that words can adequately explain what's really going on, so I wouldn't worry about it too much.
Paris: she picked up all this stuff from Wikipedia
I found Alastair Rae's Quantum Mechanics: A Beginner's Guide to be a fantastic introduction. It has some basic maths in sideboxes (and there are a couple of errors in it as well, but they're not difficult to spot) but can be read without any real understanding of the maths, and explains QM in terms of practical applications. It's a very well written book and worth a read and defies the idea that QM is some sort of hocus pocus that no-one can describe without maths or jargon. Saying all that, because I have an interest in physics I'm now looking at books which DO go into mathematical detail, and enjoying it further.
Hawking's new book was a little disappointing as it doesn't have significantly more detail than ABHoT, although I did appreciate the extra it did have. I think if you want a very, very brief overview of QM it's useful, but Rae was easier to read, I think because it went into more detail he didn't have to cram things into a small section. It's a good book and worth buying if you have an interest in physics, but I found it a bit light, although maybe it kicked off my appetite a bit.
Now, yesterday, tomorrow, year before last, never, always - It's all quantum, innit.
"Archchancellor Mustrum Ridcully uses the term dismissively as a catch-all phrase summing up all he finds distasteful and annoying in this new-fangled magic they're "discovering" and "inventing" in the High Energy Magic Building at Unseen University. "Hooray," he mutters, sourly, "here comes another bloody quantum..." "
Lspace Wiki
Simply put, two entangled quantum elements are subject to instantaeneous change if either one has its state altered. This change is NOT subject to Einsteinein physics (well, not in the simplest sense). ie, the change is faster than the speed of light.
So, what will it do for you? Well, how about unlimited, instant broadband? how about ANY amount of information transmitted without time being a factor?
And don't even get me started on what it means to be dabbling with a multi-dimensional computing model.. I mean, tapping into alternative quantumn states in an infinite sea of alternate dimensions? Erm...you're no longer operating ONE computer; you're operating one in each of said dimensons. erm...how much computing power is that?!
If you'd like a simple in on quantum physics then I reccomend "Quantum Physics Cannot Hurt You" by Marcus Chown in which he actually discusses the implications of Quantum Entanglement and Quantum Computing in a relatively (pardon the pun) straightforward manner.
http://www.amazon.co.uk/Quantum-Theory-Cannot-Hurt-You/dp/057123545X
(PS, I are only an amateur boffin. please be kind.)
"If you'd like a simple in on quantum physics then I reccomend "Quantum Physics Cannot Hurt You" by Marcus Chown in which he actually discusses the implications of Quantum Entanglement and Quantum Computing in a relatively (pardon the pun) straightforward manner." ...... Bernard M. Orwell Posted Thursday 25th November 2010 14:24 GMT
That is as may be, Bernard, but be aware of Quantum Physicists who are Unstable and would Spin Processes out of Control and Into Heavy MetaDataBase Trouble with Deep Waters and Toxic Wasted Pools. Madness, which can easily descend into Badness, is not a Stranger to Immaculate Systems of Power but there is Zero Remote Quantum Control Leverage of Assets for Manipulation of the Crazily Befuddled and Depressingly Bewildered, the Weak Willed and Undereducated and Criminally Insane.
"...over a distance of 1mm. Useful."
Their experiment might've only been over a distance of 1mm, but the whole thing with entanglement is that distance/time isn't a factor, ultimately. It doesn't matter where the entangled particles actually are in the entire universe; change one and the matched particle changes to the exact mirror instantly.
Space/Time is old hat!
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