h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Quantum Computing - A1115146
Author: Baryonic Being - U234603

Please tell me your thoughts on this guide entry. They will be greatly appreciated.

I'm not going to pretend to understand all of the science behind it, but this is a great article! The way you've explained made sense, even to a non-science bod like myself.
By the way- parallell universes? And this has been built?
Next you'll be telling me to rotate the shield frequencies on my monitor....

Thank you very much for responding to my entry on Quantum Computing. I'm pleased you liked it. If you would like some background reading on quantum physics, maybe you should read this entry: A781823, and if you want to see the basic idea behind parallel universes then try: A700598.

Yes, strange as it may seem and feel, the principle behind the quantum computer is parallel universes. The universes exist along a perpendicular dimension (beyond the fourth dimension), and come into being whenever a quantum 'decision' is made, such as an electron/photon having many possible paths to take.

Only extremely simple quantum computers have been created as I say in the entry, so there are no high hopes for having super-fast PCs in the home in the next couple of decades, or even the next century.

If you wish to rotate the shield frequencies on your monitor, feel free to do so.

I don't see any mention of the limtations of quantum computing.

as we know there are some, how about mentioning them?

What do you mean by limitations? Could you give an example please?

Hi This is a great entry, very well written. One thing i would suggest is the two links you've given in this thread could be put into the text of your guide. Find a suitable word to turn into a link and there you go. If you need help with the GuideML for this just ask, I'll be more than happy to help.

Pongo

Thanks for the advice, Pongo. I have put the links as text in a suitable footnote, and they are now in the References part also. Do you have any ideas about the limitations of Quantum Computers, as xyroth suggests?

There appears to be a shocking lack of the word 'sexy' in this article. I only say this because Quantum Physics is about as sexy as physics gets (and believe or not, sometimes physics can be dull).

Great entry, really well written! The whole concept seems to give rise to endless possibilites...amazing especially that scientists are already on the way to proving it! The way the entry is set out makes it really accessible for those of us who aren't experts!

one quite obvious limitation is that we currently know very little about how to do quantum computation.

we have a couple of specific algorithms, but no real "science of quantum computation" as yet. they just don't cover enough of the subject yet.

A lot of computing is figuring out which method is the best way to do that specific computational task. we already know that some tasks are better done with sequential algorithms and some with parallel processing algorithms (with the current state of the art in algorithms), but we don't know yet when we should do things using quantum computations and when we shouldn't.

the whole subject is currently just too new for us to have got answers to those questions yet.

we also don't know how quantum computation relates to low energy computation yet.

Thank you. I'll probably have to research that thought some more before adding it. However, I must say that quantum physics has been in development for almost a century, so our knowledge is not trivial. I know that quantum computers are using different physics altogther, which obviously makes them complex to build and so on, but basic systems have been made, as I say in the entry, and this is the first step to going a long way.

"quantum physics has been in development for almost a century"... true, but quantum computation has not been going for much more than a decade, and that has been mostly theoretical.

considering recent evidence points to there being considerable holes in our understanding of quantum physics, that can hardly be said to well understood either.

it is understood well enough for most of the usual cases, however quantum computation by definition deals with the unusual cases.

things like entanglement and other esoteric specialities which by no means fall into the part of quantum physics that is fairly well understood.

it really is the case that we only know a small number of algorithms for highly specific tasks, and as yet, none of them connect to any others, so we don't even have the beginnings of a science of quantum computation.

but we do have enough data from the stuff we do have to point to it being very likely that eventually we will have.

Thanks for the advice, xyroth, but I do have a few things to set straight:

I disagree that quantum computing has been mostly theoretical and that there are 'considerable holes' in our understanding of quantum physics. As far as I see it, the only thing we don't know about quantum physics is its relation to classical physics, i.e. a quantum theory of gravity like String Theory. But quantum physics has been proved and tested, so the basis for quantum computing is actually in place.

You say that 'quantum computation by definition deals with the unusual cases'. I think that the quantum world is just as 'usual' as the macroscopic world - it's just that we don't notice its effects.

I also disagree that we don't have the 'beginnings of a science of quantum computation' because basic quantum computers, as I say, have already been built. The quantum entanglement theory has also been proved and tested, as I say in the entry, which means we must understand it to a considerable degree.

I do agree that quantum computing is a long way off yet (as I say in the entry too), and that we do have a limited number of algorithms. How much of this do you suggest I add to the entry?

Thanks again.

Fascinating..... your bit on searching databases only applies to serial searches, which even binary computers don't usually do... however I'm also of the opinion that practical applications of binary computing are not supportable until every result can be supported. IE 25% accuracy is worthless in most practical applications, though I can think of medical applications where it would be a vast improvement.

Definately thought provoking.

sorry, but I have to disagree.

while I don't claim that quantum mechanics is complete rubish, there are definately well defined areas of doubt and uncertainty.

as well as a problem with gravity, there are still problems with light speed and entanglement (and quantum tunneling seems to do some very odd things that the theory says it shouldn't).

because traditional interactions with quantum theory have worked to minimise the uncertainties with quantum level effects, that area is fairly well understood. it just has very little to do with the bit of the theory which is intimately involved with quantum computing.

we have only just begun to start finding ways of investigating these parts of the theory, like weak measurement, and we are getting some very strange results. as these results disagree with current theory, but fall into exactly the areas which are involved in quantum computation, there is every likelyhood that there will be major new problems before we start finding universal solutions.

at the moment the situation with algorithms is like pulling a few random pieces of a jigsaw out of the box. we might find a couple that link up, but as yet we just don't have enough pieces to get the general pattern of the entire jigsaw. unfortunately it is exactly the general pattern which will be required before we get a general theory of quantum computation, and can thus produce usefull quantum computers.

at the moment we have a couple of "toy" devices which lack generality. until we progress beyond that we won't have the science for a general purpose computer, and thus won't have a generally usefull device.

Right. You've convinced me. I'll add some more information as soon as I can. Thanks very much.

I have now added an extra paragraph about quantum algorithms and the limitations of quantum computing, and I have also provided some additional links.

Your Guide Entry has just been picked from Peer Review by one of our Scouts, and is now heading off into the Editorial Process, which ends with publication in the Edited Guide. We've therefore moved this Review Conversation out of Peer Review and to the entry itself.

If you'd like to know what happens now, check out the page on 'What Happens after your Entry has been Recommended?' at EditedGuide-Process. We hope this explains everything.

Thanks for contributing to the Edited Guide!

Well done!

Thank you. Thank you very much.

Although I was thinking about adding something more about the history of quantum computing... maybe not, I don't know.