Quantum Computing Using Traditional Transistors

Awesome! by erick99 · 2004-07-22 10:51 · Score: 3, Interesting

Once they get the cost down for actually reading the the state of an electron this will be awesome. Imagine only needing 100 transistors to:

"With 100 transistors, each containing one of these electrons, you could have the implicit information storage that corresponds to all of the hard disks made in the world this year, multiplied by the number of years the universe has been around," Yablonovitch said. "And why stop with 100 transistors?"

That is pretty amazing.

Cheers!

Erick

--
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Re:Awesome! by Sgs-Cruz · 2004-07-22 10:57 · Score: 2, Interesting

It has to do with all the possible quantum states of the system. I.e. if each transistor has two states, there's 2^100 quantum states of the system when the system contains 100 transistors.
Actually making use of those squillions of quantum states is something else entirely. It's not like you can just store that much information in 100 transistors, it's that it contains all possible combinations of those 2^100 quantum states while it's running.

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Karma: pi (Mostly due to circular reasoning in posts).
Re:Awesome! by argent · 2004-07-22 11:13 · Score: 2, Insightful

Don't be too impressed... it doesn't mean as much as it sounds.

It's kind of like saying a room full of monkeys implicitly encode all the works of Shakespeare.

Secure communications? by agm · 2004-07-22 10:51 · Score: 5, Insightful

Quantum computing, which holds the promise of nearly unlimited processing power, secure communications and the ability to decode encrypted conversations by terrorists and others, is a significant step closer to becoming a reality today with new research published by a team of UCLA scientists in the journal Nature.

So which is it, secure communications or communications that can be spied on? It can't be both.

Re:Secure communications? by RidiculousPie · 2004-07-22 11:07 · Score: 3, Informative

Most encryption algorithms rely on it being easier to multiply numbers than to factorise them. Quantum computers can easily factorise a large number into a product of primes.

This is how quantum computers can break encryption

I'm not sure what they mean by the encryption that is secure though; Quantum encrytion as such is completely separate from Quantum computers, it is just a clever method using detection of the polarisation of light.

The sending computer begins by sending photons in one of four configuations, two each for the x shape and + shape

The detectors can only tell the difference between the two states if they are detecting using the correct shape.

The reciever then transmits a list saying which detector shape it used for each bit, and the sender sends back information saying when it was a correct guess, thus establishing a cipher key

Now, if someone is intercepting the signal, they will not guess the same way as the reciever, thus they wont have the cipher key at the end (I can't remember if they are detectable becuase they screw with the polarisation or not).

Thus unbreakable crytography.

[Disclaimer: IANAPhysicist, and I know that because I read The Code Book by Simon Singh. He describes it properly and accurately (both secure cryptography and breaking today's algorithms with quantum computers)]

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ah, mod points ... now where is my crack?
Re:Secure communications? by lenhap · 2004-07-22 11:09 · Score: 4, Informative

It is secure and it allows encrypted communications to be spied on. What they don't tell you is that the encrypted comunications are encrypted using standard encryption methods around today. Things that can be cracked by exhaustive search.

Using a quantum computer it can search every possible key simultaneously, cracking the encryption almost instantly. An example to understand this, you are in a building searching for your briefcase. Normal computers would go through every room one by one until they find it. A quantum computer would find the briefcase by existing in every room at the same time, finally settling (existance wise) in the room with the briefcase.

They also mention quantum cryptography being uncrackable, this is true. If someone eaves drops on communication that is encrypted, it inherently destroys the data. The users will recognize intrusion and the eavesdropper cannot decrypt the message because the data has been destroyed.

So yes, quantum computers can decrypt normal encryption that can be broken by exhaustive search and they can be used to provide quantum cryptograph which is a theoretically unbreakable form of communication.
Re:Secure communications? by cephyn · 2004-07-22 11:39 · Score: 5, Interesting

Here's what i never understood, maybe you or someone can help me out...

if eavesdropping on the encrypted transmission destroys it, couldnt the eavesdropper do so on purpose everytime, effectively jamming all transmission? Little point in having a secure way to communicate if no message can ever get through.

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Moo.
Re:Secure communications? by Bingo+Foo · 2004-07-22 12:19 · Score: 2, Informative

Yes, quantum communication is not magically DOS proof.

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taken! (by Davidleeroth) Thanks Bingo Foo!
Re:Secure communications? by Bingo+Foo · 2004-07-22 12:23 · Score: 2, Informative

The quantum channel is only used for creating one-time pads (OTP). The channel is eavesdrop-sensitive so you know which bits are compromised and you don't use them in the OTP. Then when you have generated a large enough shared OTP, you use it to encrypt the message and simply send that over regular channels, and since no one else has your securely generated OTP, that message is unbreakable.

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taken! (by Davidleeroth) Thanks Bingo Foo!
Re:Secure communications? by Christopher+Thomas · 2004-07-22 15:26 · Score: 2, Insightful

Using a quantum computer it can search every possible key simultaneously, cracking the encryption almost instantly.

My understanding was that this is not true. At best you get the square root of the number of steps that would be required for a non-quantum brute force search. This means that key sizes are effectively halved, but that isn't an insurmountable problem.

A bigger problem is that some algorithms are intrinsically vulnerable to quantum computing (or to rephrase, take far, far fewer steps to reverse on a quantum computer than a classical one). Factoring is one such case, which is why quantum computing spells the death of RSA. Most other algorithms are relatively safe, if I understand correctly (or at least, have no known quantum computing cracking method beyond brute force; this may change, unless they're _proven_ to have no other cracking method).

In summary, quantum computing is powerful, but not a magic wand that makes all classical encryption schemes invalid.
Re:Secure communications? by bigberk · 2004-07-22 17:21 · Score: 3, Interesting

if eavesdropping on the encrypted transmission destroys it, couldnt the eavesdropper do so on purpose everytime, effectively jamming all transmission?
Definitely. The main problem with practical quantum crypto communications is this issue of information loss due to noise or tampering. If you could send photons over a lossless link (impossibility) then you guarantee entirely protected communications, or easy detection of tampering/eavesdropping.

But since real transmission lines (even the best optic fibers) will always lose photons, you have to start adding on complicated processing to deal with the losses. Were the photons lost due to natural causes, or is someone eavesdropping? And if data is duplicated to account for losses, the system can possibly be tricked by an attacker into revealing information. This is a delicate subject and a great cause of complication in the field!

The communications can also be jammed of course but the focus of the technology is delivering a secure link.
Re:Secure communications? by randombit · 2004-07-23 03:08 · Score: 3, Informative

My understanding was that this is not true. At best you get the square root of the number of steps that would be required for a non-quantum brute force search. This means that key sizes are effectively halved, but that isn't an insurmountable problem.

Bingo. Which is why the AES competition required support for 256 bit keys, when even 128 bits is out of reach by any conceivable technology.

Factoring is one such case, which is why quantum computing spells the death of RSA.

Not true, necessarily. Shor's algorithm is algorithmically faster than the generalized number field sieve, but there is a constant in there. We don't know how big that constant is, and we won't until we have a quantum computer big enough to run Shor's algorithm (30 qubits or so, IIRC). It's entirely possible that Shor's algorithm is only faster then the GNFS once you hit keysizes of 10,000 bits, in which case it doesn't matter. OTOH, if Shor's algorithm is faster than the GNFS on 256 bit keys, we are, indeed, in some trouble. Of course running Shor's algorithm on a 1024 bit RSA key would take quite a large quantum computer, too.

And, as you mention, there is no algorithm for compute discrete logarithms much faster than usual on quantum computers. I haven't heard about such an algorithm, anyway. Doesn't mean it doesn't exist, of course.

Summary: algorithmic complexity is not the sole determinant of algorithm running time.

In summary, quantum computing is powerful, but not a magic wand that makes all classical encryption schemes invalid.

Thank you. Every time a quantum crypto or quantum computing store pops up here, the hype level seems to increase by several orders of magnitude. It's really annoying.

Now that's a huge hard drive... by zeux · 2004-07-22 10:52 · Score: 3, Insightful

From the article:
"With 100 transistors, each containing one of these electrons, you could have the implicit information storage that corresponds to all of the hard disks made in the world this year, multiplied by the number of years the universe has been around," Yablonovitch said. "And why stop with 100 transistors?"

Of course, because with 101 transistors you could store as many Library of Congress as there are electrons in the visible universe on a disk the size of 2 square hogs for a duration of up to 3.4256 parsecs.

Unfortunately, it will take up to as many (1/98742) of year as it took in seconds for Apollo 11 to reach the moon from the launch pad to design such a hard-drive.

Why is it scientists always use weird units? I have absolutely no clue of what "the implicit information storage that corresponds to all of the hard disks made in the world this year, multiplied by the number of years the universe has been around" actually represents in bytes.

--
Iraq: war to save the U

That's weird by Anonymous Coward · 2004-07-22 10:53 · Score: 4, Funny

The article said something totally different brfore I clicked it.

Hrmm... by Arcanix · 2004-07-22 10:53 · Score: 5, Funny

I thought about reading the article but will it change if I look at it?

wow! by quelrods · 2004-07-22 10:53 · Score: 3, Informative

This would be something to help drive down the cost. Quantum computing on the desktop would finally be a evolutionary step in computing. (Up'ing clockspeed constantly and decreasing chip size is not evolutionary.) Though, quantum computing on the desktop probably means time to stop using passwords due to sheer power to brute force them.

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:(){ :|:&};:

Re:wow! by geekoid · 2004-07-22 10:55 · Score: 3, Insightful

"(Up'ing clockspeed constantly and decreasing chip size is not evolutionary.) "

actually, it is evolutionary, just not revolutionary.

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The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

Kind of misleading... by 7Ghent · 2004-07-22 10:55 · Score: 5, Informative

They're actually using pulsed microwave bursts to manipulate the electron's spin, not the transistor itself, really.

Re:Kind of misleading... by QuantumG · 2004-07-22 17:17 · Score: 2, Insightful

Well seeing as you can lay down a junction on a silicon die that can produce that microwave burst just as easily as you can lay down a transistor the basic principle that you can do quantum computing with silicon is still being demonstrated.

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How we know is more important than what we know.

Tin Foil Hat Time... by CommanderData · 2004-07-22 10:58 · Score: 4, Insightful

From the article:
Quantum computing, which holds the promise of nearly unlimited processing power, secure communications and the ability to decode encrypted conversations by terrorists and others (emphasis mine)

Take special note of the word others, which should be read as everyone. The government will be falling all over themselves to support this research and inherit a technology that makes encryption virtually useless.

I'm all for advancing technology, and no doubt quantum computing will be a great leap forward. It's just a shame that our privacy will be sacrificed in the process.

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Urge to post... fading... fading... RISING!... fading... fading... gone.

How long before I can turn my transistor radio by Anonymous Coward · 2004-07-22 10:58 · Score: 2, Funny

...to a quantum radio? I want to pull in stations from alternate universes since there is no good local music.

Secure Communications ... by mdvlspwn99 · 2004-07-22 11:01 · Score: 4, Insightful

is great. Until the technology becomes ubiquitous enough that even terrorists have access to it. Then what? It's secure...even from us.

--
If reality was like Slashdot, most people would be (-1) Redundant.

Quantum terms by Decaff · 2004-07-22 11:05 · Score: 3, Interesting

I wish physicists would be more cautious in their use of language.

In the article it states: "The UCLA team succeeded in flipping a single electron spin upside down."

Considering that the term 'spin' is just a metaphor for a quantum-mechanical property that has no equivalent in our everyday experience, it makes no sense to talk about 'flipping' it, or the spin being 'upside down'.

Neat achievement though....

Re:Quantum terms by Ruie · 2004-07-22 14:45 · Score: 2, Interesting

Actually this was pretty precise.
You see electron spin space is a two dimensional complex space. It is tied to usual 3 dimensional real space via representation of SU(2) - so it is hard to say which direction corresponds to which.
However, if one fixes a basis in usual space one can use it to fix a particular representation of SU(2).
Furthermore, one of the basis vectors will have a particularly simple Pauli matrix corresponding to it - the direction of this vector is usually called "quantization axis".
Often this vector corresponds to "z" axis. The "up" spin is then defined as (1,0) and the "down" spin is (0,1). So flipping the spin upside down is just switching components.
Another justification for talking about "up" and "down" is that spin vectors are usually written as columns so there is an upper entry and the lower entry.
Re:Quantum terms by Decaff · 2004-07-22 20:26 · Score: 2, Informative

Must confess I am being pedantic here, so I may be annoying, but....

Usual 3 dimensional spin is characterized by speed (revolutions per second) and the axis the object is spinning about.

Yes, but with quantum mechanical particles, nothing is spinning. There is not one part of an electron that is rotating about another. (see my warning about 'pedantic' above!)

Flipping spin means reversing the axis - i.e. changing the direction of rotation.

But with quantum mechanical particles, there is no real 'direction' - its a relative property, and direction is meaningless when there are only limited states.

Its a metaphor, an analogy, and that is all. We have absolutely no idea what is 'really' happening at the 'electron' level. All we have is some math that gives answers. I strongly believe that using terms like 'spin' gives a false impression of understanding. Eventually terms like 'spin' and 'orbit' are so frequently used they crowd out alternative metaphors.
Re:Quantum terms by Ruie · 2004-07-22 20:53 · Score: 2, Interesting

I guess we have different points of view them..
Just for fun let me continue.. :)
What do you mean by nothing is spinning ? What does it mean to be spinning ?
I can tell when a ball spins because I can see it. But does Earth spin ? I can't see the rotation but I can infer it with tools.
Do small pieces of matter (like dust) spin ? Maybe.
Now it turns out when you look at very small pieces of matter (like particles) then the laws of nature we are accustomed to change. This is simply because we do not teach quantum mechanics in kindergarten.
One that is aware of quantum mechanics see its manifestations on macro scale - they are just commonly perceived as separate phenomena (like electricity).
Now classical rotation corresponds precisely to quantum spin.
When you consider two quantum particles (with spins J1 and J2) as a single system the result is a tensor product of spins - so you get a direct sum of representations between |J1-J2| and |J1+J2|.
When you have a lot of particles comprising a ball you can still describe it on a quantum mechanical level - it would be a direct sum of representations of SU(2) with numbers between 0 or 1/2 and N/2 (where N is the number of particles).
The "usual" behaviour you are accustomed to happens because the particles have weakly interacting spins and are unordered.
The quantum part can manifest in macroscopic situations, albeit in (so far) very restricted circumstance - for example quantum Hall effect.
My point is that you can start at very small with quantum notion of spin and then as you increase the number of particles in your system you will gradually reach the situation where classical notions of spin are a *very* good approximation.
Re:Quantum terms by Ruie · 2004-07-22 21:15 · Score: 2, Interesting

The "usual" behaviour you are accustomed to happens because the particles have weakly interacting spins and are unordered.
Sorry, this is not right. Usual behaviour is due more to particles changing positions than to remnants of quantum behaviour.
So your point would hold if we restrict ourselves to considering only spinning that is due to bodies rotating one around another.
My point would hold if we allow idealization of solid body - i.e. an object with an intrinsic spin.
For example, you could consider a ball as multitude of molecules changing positions around each other.
Or we can consider it as idealized object (sphere) with an axis of rotation - I usually think of it this way. (So throwing a ball is composed of two parts - imparting linear movement and spinning the ball around with fingers. Note that usage of "spinning" as independent of movement.)
Quantum spin is the right generalization of intrinsic spin at the quantum level.
Re:Quantum terms by trixillion · 2004-07-23 05:00 · Score: 2, Informative

Saying that something is spinning in the classical sense imputes an angular momentum on the object. But the quantum of angular momentum has different units than the quantum of spin. Hence, quantum spin is fundamentally different from classical spin. And this is one of the rationales that has been argued for decades for why quantum spin should be given another name.

I had a Quantum hard drive before by gphinch · 2004-07-22 11:09 · Score: 5, Funny

"With 100 transistors, each containing one of these electrons, you could have the implicit information storage that corresponds to all of the hard disks made in the world this year, multiplied by the number of years the universe has been around," Yablonovitch said. "And why stop with 100 transistors?"

I hope this drive lasts longer than the Quantumm Fireball I had.

--
in bed.

Ready for Doom 4! by Evil+Butters · 2004-07-22 11:26 · Score: 2, Interesting

Cool... With one of these new quantum computers, I should be able to meet the minimum requirements for Doom 4! Now if only I could get my quantum video card to work...

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Homer no function beer well without.

Terrorists? by mikeg22 · 2004-07-22 12:11 · Score: 2, Insightful

Oh, you mean the ones that use human couriers to relay messages? The ones that live in caves with no access to computers?

No, this technology is not going to be used on terrorists. It is going to be used on a combination of normal people suspected of criminal activity (ie anyone who bothers to encrypt their communications) and actual hightech criminals.

This technology will be effectively useless at stopping the terrorists we are worried about.

Re:Terrorism. by emeitner · 2004-07-22 12:13 · Score: 3, Insightful

Fear sells.

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Guru Meditation #6d416769.21610a21

Don't hold your breath... by Dr.+Mu · 2004-07-22 12:15 · Score: 2, Interesting

I Google-whacked 'quantum-computing Clear-Channel' and already got 63 hits.

Re:Why does anyone believe this works... by Requiem+Aristos · 2004-07-22 12:38 · Score: 2, Insightful

*SMACK*

This would be an accurate description, only it's not.

If you perform the double-slit experiment with twenty humans, a canon, and segments of brick walls, you don't wind up with an interference pattern. With electrons, you do. Also, factoring with quantum computers has been successfully performed, so we know it works.

If it makes you feel better, it isn't just a matter of treating statistics as physical reality. It's more a matter of realizing that at certain small sizes, 'matter' isn't exactly matter. It's closer to energy, and has a wave behavior similar to energy. It just happens that measurable physical properties can only be said to exist when the wave function has 'collapsed'.

(I expect some QM geek will want to correct my explanation, but it's certainly more accurate than your attempt. Happy trolling!)

Implicit Disinformation by reversible+physicist · 2004-07-22 13:12 · Score: 3, Interesting

Quantum communication is already practical, and provides a secure way to communicate to replace factoring-based encryption, which quantum computation may one day make insecure. The hype in this article, though, is way over the top. 100 electron spins can only encode 100 classical bits. Not one bit extra. Yablonovitch is using a very sloppy way of talking about how hard it is to simulate 100 spins, and making it sound like he's talking about a way to store a lot of classical bits! His "implicit information storage" is nonsense. It's also worth mentioning that quantum computation is unlikely to speed up any computation you care about, unless you like to simulate quantum systems. Fast factoring is the "killer app" that got people excited about this field, but "terrorists" (and the rest of us) can just stop using factoring-based encryption.

Name that profession by bigsteve@dstc · 2004-07-22 14:02 · Score: 2, Funny

Do these researchers call themselves "quantum spin doctors" or just plain "quantum mechanics"?

I can see it now.... by teutonic_leech · 2004-07-22 14:11 · Score: 3, Funny

Welcome to Windows Quantum 2006! We crash several ways at the same time!

Intro to Quantum Computing by GogglesPisano · 2004-07-22 14:13 · Score: 3, Informative

The following link may be helpful for those of us who are a little fuzzy on quantum computing: http://www.cs.caltech.edu/~westside/quantum-intro. html

OT: wrt to your sig by mysticgoat · 2004-07-22 18:15 · Score: 2, Funny

Karma: pi (Mostly due to circular reasoning in posts).

Sir:

Your sig is irrational.

Just thought you'd like to know that.

Re:Hmm... by carnivore302 · 2004-07-22 20:00 · Score: 2, Informative

First off: I am not an expert, just someone who watches this closely and has read a lot of books on the subject. (Hint: The fabric of reality and Quest for the Quantum computer are very good, not to difficult to read)

In a sense, nothing has been achieved here that hasn't been achieved with other methods. These guys are strugling with just one quantum spin, which doesn't even make one qubit (you have to do more) where others like some researchers from IBM have already combined 4 qubits. Making just one qubit isn't all that difficult these days, but combining them in a way that they are still usable is increasingly difficult when the number of qubits increases. It's called the problem of decoherence.

...But: what is good about this is that it is being done with conventional approaches: an ordinary transistor. Now they can use everything that is known to transistors to proceed and make it better. (what is not so good is that they still need to do it at _very_ low temperatures.)

--
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Re:Article is misleading by Rich0 · 2004-07-22 23:48 · Score: 2, Interesting

One problem - quantum crypto only works for direct hardware links. It does not allow for retransmission of photons. So, it is limited in range and generally to line of site (or whatever you can reach without reboosted fiber optics).

There is no technology which would allow two distant parties (say 1000 miles apart) to use QC to secure their communication against any evesdropping. There is nothing to suggest that this technology will ever be developed.

Now, with retransmission you could link two arbitrarily distant points. However, you could easiliy intercept the transmission without notice at the repeater. In fact, in most practical implementations, the repeaters are owned by a network provider, who of course would be complying with court orders, etc.

So, QC will prevent cable tapping and stuff like that in the middle of nowhere. However, it will not prevent people with access to the satellites/network closets/etc from intercepting communications.

For all practical purposes, that is no different from not having QC at all. How many communications are intercepted via cable-tapping these days? If you want to intercept something you either get a warrant for an ISP to install Carnivore, or you bribe somebody at the ISP (if you're not legit).

So, QC will not lead to terrorist having secure lines of communication...

"Quantum voting" by tooloftheoligarchy · 2004-07-23 01:08 · Score: 2, Funny

(From the article): Perhaps future elections will be held using secure quantum voting.

Gives new meaning to the term "spin doctor".

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Quantum Computing Using Traditional Transistors

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