Quantum Computers

nesf

I've heard stuff on some fo the theory proposed, with 2 particle systems and such, but is there any experemental progress being made?

Trojan

Quantum physics is an amazingly interesting area, it's even possible to understand it from a lay perspective.

I thoroughly recommend reading Crichtons (sf) "Timeline" <A HREF="http://www.amazon.com/exec/obidos/ASIN/0345417623/qid=997881640/sr=8-1/ref=aps_sr_b_1_1/104-4840970-3183101&quot; TARGET=_blank>http://www.amazon.com/exec/obidos/ASIN/0345417623/
qid=997881640/sr=8-1/ref=aps_sr_b_1_1/104-4840970-3183101</A>

- it hasn't got great reviews on the site, but those guys are muppets, it's a good book.

Definition of quantum computation:

<font face="Verdana, Arial" size="2">
A fundamentally new mode of information processing that can be performed only by harnessing physical phenomena unique to quantum mechanics (especially quantum interference).
</font>

QC makes easy:

Cryptography: perfectly secure communication. (see http://www.qubit.org/intros/cryptana.html for more on this)
Searching, especially algorithmic searching (Grover's algorithm).
Factorising large numbers very rapidly (Shor's algorithm).
Simulating quantum-mechanical systems efficiently.

Have a look at
http://www.qubit.org/intros/comp/comp.html and all the files on there in fact.

Lets get some discussion going on this (before Der Fuhrer deletes it for being Off-Topic ).

Anyone know much about the (successful) teleportation effort they got working back was it last year or 99? I know it was only a sub-atomic particle, but it's teleportation ffs!

Al.

[ Edited to stop long lines scrolling screen over, but I broke the amazon url, take out the space ]



[This message has been edited by Trojan (edited 15-08-2001).]

KevDaEdbanger

I read a while ago that they were thinking of using complacated molecules (Such as Caffien) as the basis for Quantum computing for example I think Caffiene has 8 diffrent qunantum varibles each one of which could be used as a Q-bit more complacared molecules such as Proteans could be used to form more powerfull coprossessers. For More info got find New scientist Magizen's website.

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8¬)

Trojan

<font face="Verdana, Arial" size="2">Originally posted by KevDaEdbanger:
For More info got find New scientist Magizen's website.
</font>

Yeah, they used to have a cool article at http://www.newscientist.com/features/features_22393.html but they moved it on me the bastids.

Al.

Ivan

Yeah I heard about it, I read an article on it. It was a proton they teleported across a room. Which sounds like ****e but in fact is pretty awesome when you think about it.

Now all we have to do is learn how to split highly advanced, organic and inorganic substances into tiny protons, get enough equipment to teleport each and every one of them (or else wait a very long time as the one machine teleports millions of protons, then figure out how to put the stuff back together, Sort out the whole missing electrions, neutrons (not to mention neurons, quarks and other stuff) mix them all back together to get what we originally had.
AND finally, figure out how we're gonna get enough enery, and brain-power to do all of this.

So guys, not long now :]

Nah seriously, it was pretty awesome, I was majorly impressed, but it took some crap loads of energy, and it was only across a room, and only 1 proton. So kind of a cheap victory, but a victory non-the-less.

I'd recommend ye sell all ye're shares in Bus Eireann :P

I'm gonna rummage around and see if I can find the article. I'll post again if I can find it.

Hobbes

From what I gather the problem isn't getting the computer to work but actually getting the answer.

Once you look at the answer it will change.

Or something like that.

nesf

As far as I know Hobbes, you can get around that. I had a lecture on how if we trap two particles in a potential well, in a lever system, that is only one can have a high energy value as if the particle were on opposite ends of a see-saw, you can circumvent the Uncertainty principle.

The proof is all maths, and since I'm posting from memory, I can't replicate it.

I would disagree on understanding quantum physics from a lay perspective, you'll spend 4 years at college studying the stuff and still be confused Also quantum theory is very math heavy and not at all intuition based, it's a hard thing to explain to someone with out being too definite. In quantum physics everything that should happen might happen, and everything that shouldn't might just happen anyway

Thats not fully true of course, but it's close enough.

Bob the Unlucky Octopus

<font face="Verdana, Arial" size="2">Originally posted by Trojan:
Lets get some discussion going on this (before Der Fuhrer deletes it for being Off-Topic ).
</font>

Mein Leben!! They're onto me...ach

KevDaEdbanger

<font face="Verdana, Arial" size="2">Originally posted by nesf:
I would disagree on understanding quantum physics from a lay perspective, you'll spend 4 years at college studying the stuff and still be confused Also quantum theory is very math heavy and not at all intuition based, </font>

Its this kind of lazy thinking I hate. Physics is not about maths. Maths is mearly a tool for those who have trubble geting their Imaganation in gear. I love Physics. I hate Maths. I'm Good at Physics. I keep failing my maths tests 8¬(

Any time some one saws something is too difficult to explain to you what they mean is they haven't bothered to figure it out for themselves yet.


And quantum computing dose not involve Teloporting Protons (Ie the positivly charged particals in the nuclus of atoms) Thats Quantam Tunniling using the uncertainty principle to make particals apear to voilate the laws of therom dynamics but moving from low to high Energy states without an energy input. Quantum computing uses fuzzy logic gates to inturprit the final rest state of a molecule that has a number of quantum varibles as a Didgital signial.

_____________________________________________
My own quote:
"Nothing was created in the Big Bang,
Allong with Everything Else."
_____________________________________________

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8¬)

Trojan

<font face="Verdana, Arial" size="2">Originally posted by bonkey:

On an aside - Trojan - Quantuum Crypto does not require a quantuum computer.

jc</font>

Who said it did?

I said it made it easy. Cos that's what the qubit guys say. Cos they know what they're talking about.

But go on, prove your intellectual prowess, tell us why.

Al.

[edit] Took out secondary quoting [/edit]

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Sedulously eschew obfuscatory hyperverbosity and prolixity.

You really should you know.



[This message has been edited by Trojan (edited 17-08-2001).]

bonkey

<font face="Verdana, Arial" size="2">Originally posted by Trojan:
But go on, prove your intellectual prowess, tell us why.
</font>

Quantuum crypto can be achieved by sending someone a set of polarised quanta, which they then read using an arbitrary set of polarised receivers. Simplify, and assume there are "+" and "x" masks. an you send any one of 4 bits (| - \ /).

Some bits they will interpret correctly as they pass through the filter, some will get blocked, and some will be read incorrectly as they will validly pass through the filter despite being the wrong polarity. This last bit of weirdness is related to quantuum effects and is perfectly valid, and also unpredictable.

The recipient then sends you back a list of the bits they read, and you simply tell them which were correct. Obviously, in a real world situation, this is done by electronic hand-shaking.

Because anyone interpreting the signal and trying to read it along the way would "mess" with the quanta, you will know if the signal was interrupted or intercepted as the initial messages encrypted will be undecipherable.

On the other hand, simply knowing which bits of the original signal were used is useless to an interceptor, because they still dont know the polarity of the quanta in question because they couldnt intercept and read it.

In otherwords, you use quantuum mechanics to generate a non-interceptable one-time pad.

If you read Simon Singh's The Code Book, he gives a slightly more coherent explanation of how it works in theory...and apparently some people already have working models.

At present, all models require line of sight for the quanta transmission, which is a bit useless.

jc

bonkey

<font face="Verdana, Arial" size="2">Originally posted by Trojan:
I said it made it easy. Cos that's what the qubit guys say. Cos they know what they're talking about.
</font>

I've just read your link, and they say no such thing.

qubit say that quantum computers would make cryptanalysis of conventional ciphers easy, as they can easily factor large numbers. The factorisation of large numbers is an unfeasibly difficult task today, as there is no known effective shortcut. QC would eliminate this.

They do not, anywhere that I can see, mention how a quantum computer could be used
for cryptography.

jc

Trojan

<font face="Verdana, Arial" size="2">Originally posted by KevDaEdbanger:
Its this kind of lazy thinking I hate.
</font>

Agreed.

Have any of you guys read Feynman?

oh god, I hope SS-Bob doesnt read this one...

Al.

bonkey

<font face="Verdana, Arial" size="2">Originally posted by KevDaEdbanger:
Its this kind of lazy thinking I hate. Physics is not about maths. Maths is mearly a tool for those who have trubble geting their Imaganation in gear. I love Physics. I hate Maths. I'm Good at Physics. I keep failing my maths tests 8¬(
</font>

There is a world of a difference between understanding concepts in physics, and being able to use them.

To understand and communicate an idea does not require mathematics. To use physics does.

Put simply, you can understand the concepts of quantum mechanics without ever seeing a single equation. I very much doubt that you'd ever be able to do a single piece of work on the subject without mathematics, just by "getting your imagination into gear".

On an aside - Trojan - Quantuum Crypto does not require a quantuum computer.

jc

Trojan

<font face="Verdana, Arial" size="2">Originally posted by bonkey:

They do not, anywhere that I can see, mention how a quantum computer could be used
for cryptography.
jc</font>

<font face="Verdana, Arial" size="2">
What will quantum computers be good at?

These are the most important applications currently known:

Cryptography: perfectly secure communication.
</font>

I think that's pretty plain!

Apologies, I didn't want to get into a bítching match, but tbh any kind of crypto without a computer sounds like too much hard work to me. I don't understand the issues, and won't until I've a couple of quiet hours to spend reading this stuff

Al.

---

Sedulously eschew obfuscatory hyperverbosity and prolixity.

You really should you know.

Bob the Unlucky Octopus

<font face="Verdana, Arial" size="2">Originally posted by Trojan:

oh god, I hope SS-Bob doesnt read this one...

</font>

Wasn't it UnterSturmfuhrer Amon Goeth who said "Sheep will always need a shephard?" :P

Anyhow, I've got Feynman's lectures on tape- LMU did a fantastic joint release with EMI, I also got the transcripts of some of his famous lectures. A true genius of quantum mechanics, yet the idea of a quantum computer was one he thought a tad ludicrous. Any physics majors out there?

Bob the Unlucky Octopus

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My name is Dr. Gathermole Lipharvest the Third...the other two died of embarassment.

nesf

<font face="Verdana, Arial" size="2">Originally posted by KevDaEdbanger:
Its this kind of lazy thinking I hate. Physics is not about maths. Maths is mearly a tool for those who have trubble geting their Imaganation in gear. I love Physics. I hate Maths. I'm Good at Physics. I keep failing my maths tests 8¬(

</font>

I would disagree, alot of the concepts of quantum mechanics are mathematically based. To understand them would require you to look at the maths. You could repeat the english explanation, but as to predict what would happen, you'd need to use maths. Look at an extremely simple quantum system like a harmonic oscilator in a square potential well. Try understanding it without looking at any maths or diagrams, then try to apply that understanding. It's near impossible, because what happens with probability spreads is completely non-intuitive.

Theres alot in physics that doesn't
translate well into English.

Its not lazy thinking, just my own opinion as a physics student at college. Most of the stuff that I've seen I couldn't understand totally until I saw the maths. I'm not good at maths exams either, but thats because maths as a subject and maths as a language for physics are very different.


Plus physics is not seeking to get your imagination in gear, it's trying to explain the way the world functions at a very basic level. No theory can be put forward without a strong mathematical backing. So to say that maths is not physics is non-sensical imo. You're thinking more along the lines of natural and metaphysical fields of philosophy, which are equally fascinating subjects but not the same as physics.

Gargoyle

I'm a graduate student at University of Virginia. We, in cooperation with several other American universities, are in the early development of a basic quantum circuit. We are currently trying to use a focused ion beam machine to do the lithography (no photoresists) but having a bit of a problem with the resolution right now. It may eventually be necessary to use deep UV laser lithography techniques to accomplish the necessary resolution for the quantum effects of the circuit to work reliably. However, with IBM as a big funding source, I believe it will be available within 10 years.

EDIT: Those who assume that cryptography will be unbreakable assume that the crackers won't be using quantum computers as well. Ccryptographers will be forced to develop an entirely different model once the massively parallel quantum computers become readily available.


[This message has been edited by Gargoyle (edited 25-08-2001).]