First Quantum Byte Created

gila_monster writes "Juice Enews Daily is reporting that the Institute of Quantum Optics and Quantum Information at the University of Innsbruck in Austria has created an entanglement of eight quantum particles, yielding a quantum byte or 'qubyte,' or eight qubits. The formal paper was published in the December 1 issue of Nature. A qubyte with eight ions provides a computing matrix of 65536 mostly independent elements. No word in the article about whether they were able to actually use the qubyte for computing."

Comments

no word in the article

[Anonymous Coward]

No word in the article about whether they were able to actually use the qubyte for computing

I think we can be sure that if somebody had unlocked the secret of quantum computing there's a chance they'd say so at some point.

Re:no word in the article

[David Hume]

I think we can be sure that if somebody had unlocked the secret of quantum computing there's a chance they'd say so at some point.

Unless that someone worked for the National Security Agency.

Re:no word in the article

[Mjec]

I think we can be sure that if somebody had unlocked the secret of quantum computing there's a chance they'd say so at some point.

Ummm... not quite. There's lots of quantum computing currently being done - 4 qbit computers exist in several places (or can be brought into existance on demand, anyway). Quantum computation requires entanglement and manipulation of entangled bits. Well, the former is the hard part - that's what's been managed here. A major step forward - I recall 6 qbits was the record about a 18 months ago. Entangled bits are quite delicate - so that's the next challange. Now that they can entangle this many bits, they just need to manipulate them. That'll come with time.

Quantum bytes still decryptable?

[LiquidCoooled]

Wasn't there some news recently that the so called quantum bits could be read without disturbing their state.
Which would either break quantum theory, or would mean they are just fabricated bits of information and not quantum bits at all.

The article was here

Re:Quantum bytes still decryptable?

[Silverlancer]

Read the post here. It (and a few responses to it) describe why this doesn't violate quantum theory.

Re:Quantum bytes still decryptable?

[LiquidCoooled]

Doesn't Quantum theory say you cannot read the state without disturbing the state?
The act of finding the state of a quantum bit collapses the quantum wave and obtains a result, ie you can find out what the value is now, but that may disturb what the value was going to be leading to possibly incorrect answers.

Qubits as described by modern phsyical science do not sound like true theoretical quantum bits and just sound more like tiny transistors.

obligatory bill cosby quote

[baldass_newbie]

"God, what's a qubit?"

Que?

[Rhinobird]

A qubyte with eight ions provides a computing matrix of 65536 mostly independent elements.

Wouldn't a qubyte just provide an indeteminate number of somewhere between 0 and 255 zombie cats?

Seriously, how do they get a 16 bit number out of an 8 bit qubyte?

Re:Que?

[L0phtpDK]

Umm... No.

One qubit has four states. So its actualy an 8-qubit integer.

(go through the powers of x^4: 4,16,64,256,1024,4096,16384,65536)

Re:Que?

[marol]

Don't you mean 4^x?

Re:Que?

[Ruberik]

A qubit has an uncountably infinite number of states: choose any two complex numbers A and B such that |A|^2 + |B|^2 = 1, and they define an allowed qubit. On the other hand, when you measure a qubit's state, you can get one of two results: 0 (with probability |A|^2) or 1 (with probability |B|^2).

I can't find the original article, so I don't know where this 2^16 business is coming from, but I assure you that a qubit does not have four states -- the only useful numbers for counting a qubit's number of states are infinity (quantum states) and two (possible measurement results).

If someone can link the paper this comes from, I'd be interested in reading it: I'm doing a MSc in quantum computing right now, so I might be able to decipher the source of this 2^16 stuff.

Re:Que?

[maxwell demon]

If I am understanding this wrong, please correct me :).

You understand this wrong.

A qubit indeed can have one of a continuum of states. For example, if you think of the photon polarisazion, each linear polarization direction corresponds to a distingt state, and then there are the circular and elliptic polarized states as well. Indeed, you can map the states of a qubit onto a sphere (embedded in ordinary 3D space), which is called Bloch sphere. Every point of that sphere corresponds to a (pure) state of the qubit. (Note that the Bloch sphere is not the Hilbert space, but for single qubits, it's IMHO much easier to understand things in the Bloch sphere picture)

Now if you measure, you basically choose a direction on that spere, and you get just one of two results. e.g. if you think of the sphere as Earth's surface, and let's assume you have chosen the direction of the Earth's rotation axis for measurement, then if the state of the qubit (before measurement) is actually the North Pole, you get with certainty one result (which, for obvious reasons, I'll call "North"), and if the state is the South Pole, you get with certainty another result (which I'll now call "South"). However, even if the state is something else, your measurement will never give anything but "North" or "South". The probability to get "North" grows the closer the state is to the North Pole, and equivalently for the South Pole. If the state is at the equator, the probability of getting North or South is the same, i.e. the result of your measurement is completely unpredictable.

Now the funny thing is that after you measured North or South, for an ideal quantum measurement, the state actually is the corresponding Pole, no matter what it was before.

If you map the states described by the article with the Bloch sphere, and say you map the states 0 and 1 to the North and South pole, then the states you named `0 and `1 would be two antipodal states on the equator, say on the zero meridian and on the 180 degree meridian (unlike in the hilbert space, the directions now are not in 45 degrees, but actually orthogonal). That is, if the state is `0 or `1, then any measurement in the north-south direction will give completely unpredictable results. Of course if you choose the direction of the `0 and `1 states (I'll call that the equatorial direction from now on), then those states will create a predictable result, while the North and South pole states will get completely unpredictable results.

Now the nice thing for encryption is that if you don't know if the state was prepared in the North-South direction or the equatorial direction, there's no way for you to know if what you got for a measurement is a prepared state, or just random garbage. Moreover, since measuring in the wrong direction changes the original state (and therefore destroys the information which was originally in there), you'll be able to notice if someone tries to eavesdrop your connection.

Re:Que?

[milimetric]

I've read the posts here and I can point you to one source that I know is accurate, easy to understand and in my opinion beautiful:

N. David Mermin

This man is a genius. He can also explain his genius which makes him quite unique. I took a class of his and actually understood some stuff. His basic goal is to explain quantum computation to CS students. More on topic, here's the skinny on qubits:

Chapter 1 of his intro class

I really wouldn't do justice to the ease with which he explains things to attempt to summarize, but hey, what's slashdot for:

Basically skip ahead to part C if you want to jump right into it. It helps if you think of Classical bits as vectors in a two dimensional space. (0,1) and (1,0) would represent 0 and 1 as we normally think about them. So then think about Quantum bits (qubits) as (a,b) which is just a superposition of the two classical bits with amplitudes a and b which are complex scalars. The only condition is that the qubit is a unit vector in two dimensional complex vector space, or in short |a|^2 + |b|^2 = 1. Now more to the point of this thread, if you go to section 1..62 you can see that n qubits make up a computational basis (or classical basis). So, the answer is, there's not really anything like simple 0,1 states for qubits. The truth is more complicated but once you start looking at how to take advantage of qubits, a lot more beautiful in my oppinion.

Getting there...

[meringuoid]

... Eight qubits? ISTR that Shor's original quantum error correction code requires nine, and there are simpler codes requiring fewer. We're getting here into a scale where some very interesting features of quantum computation can be demonstrated.

Why eight?

[pubjames]

Why did they choose eight 'bits' for their quantum 'byte'? For historical reasons, or is there a logical reason to choose eight? Why not seven, or 42?

I'm not being entirely frivolous - I understand quantum computing is radically different from today's architectures and so don't understand why they are choosing a byte size based on what seems to me to be historical factors.

Re:Why eight?

[glwtta]

Why did they choose eight 'bits' for their quantum 'byte'?

They probably felt that 7 wasn't enough and 9 was too many.

A few more..

[Renraku]

We need a few more before quantum porn.

Think about it..any kind of porn in one file..

Re:A few more..

[aug24]

Mmmm, quantum porn. Super-position, entanglement and some guy with a pussy.

J.

Re:A few more..

[syle]

But is the pussy alive or dead? Beastality or necrophilia are two completely different areas of porn and discriminating viewers need to know!

Think of the cats!

[Anonymous Coward]

Let us all take a minute to reflect on all the cats who died in support of this research.

Or maybe they didn't.

Star Trek School of Programming

[UncleAlias]

"That's not a bug, that's a quantum singularity!"

And God Said to Moses...

[craznar]

... build a Linux Box 40 Qubits in size....

Why, Oh, Why?

[tcdk]

Do we really need this? I can't imagine how anybody will have usage for more that four qubits anyway. When will the madness stop?

Re:Whats a Qbit?

[centie]

A qubit is a superposition of two states, a 1 and a 0 if you like. So it containes some 0 and some 1, or written as a|0> + b|1>, where a and b describe "how much" (more accuratly the probability) of 0 and 1 in the state. a and b are in general complex numbers. One qubit has then 2d hilbert space, 2 quibits 4d and 3 quibts 8d etc. So 8 qubits has a 256 dimensional space for its complex amplitudes (a and b etc) to inhabit.

Here's a no-b.s. article on quantum computers

[putko]

I found this at Caltech, a piece on quantum computers. I've never really taken quantum computation seriously -- it just seemed too far-fetched. If they've really got 8-bits, maybe quantum computing will matter in my lifetime.

From reading the piece, it sounds like we will have some major problems with our current cryptographic systems if quantum computers become available.

Re:Quantum Calculations

[centie]

You've kind of answered your own question..

The massive parrallel computation with a single element means you can solve *certain* problems in, for example, 2n instead of 2^n steps. But yes, then you get a bit matrix of answers, and reading them all out takes the same amount of steps as classical computing. But, your only usually intristed in some of the answers, so you can then use another algorithm (eg Deutsch-Jozsa) to read those out, again faster than classically.

So you get a substantial decrease (ofton exponential) in the time taken to solve *cetain* problems. Some of these problems would simply be impossible to solve in any reasonable timescales (eg milennia) using classical algorithms.

Re:Mostly independent?

[spot35]

We are qubit 7 of 8 or computing matrix 65536. We will will add your cryptographic and entangled distinctivenes to our own. We are the qubyte. Resistance is uncertain.

yay!

[3-State Bit]

I was born in 1983, but now I can re-experience even advances in computing that happened in the seventies and before! Cabinet-sized hard-drives that hold a couple of megabytes? Quantum computing is at A FEW QUBITS! I doubt many people here lived through the ENIAC (and realized what it meant at the time), but that's exactly what my grandchildren will be hearing from me. Granson, back in my day we had EIGHT QUBITS! Not qubytes, QUBITS, sonny boy, eight of 'em. Like this: one, two, three, four, five, six, seven, eight. Total. And that was state of the art. It was a research demonstration! And we liked it!

"There is a world market for 4, maybe 5 quantum computers."

"512 kiloqubytes outta' be enough for anybody!"

Etc, etc, etc. WHOOOHOO!!! I was there at ground zero, baby!!! In ought six!!!!

What do you mean ought-six, grandpa? "I mean 2006, granson".

"Whoa! When were you born?"

"I was born in the LAST MILENNIUM, GRANSON"

"Did they have cars?"

"Just road ones."

"What about Google?"

"yeah, but it wasn't like today. Man I wish I'd have held on to that stock tho'..."