Several Quantum Calculations Combined At NIST

Al writes "Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a crucial step toward building a practical quantum computer: multiple computing operations on quantum bits. The NIST team performed five quantum logic operations and 10 transport operations (meaning they moved the qubit from one part of the system to another) in series, while reliably maintaining the states of their ions — a tricky task because the ions can easily be knocked out of their prepared state. The researchers used beryllium ions stored within so-called ion traps and added magnesium ions to keep the beryllium ones cool and prevent them from losing their quantum state." In related news, another reader links to an Australian study indicating that quantum computers "can continue to work perfectly even if half their components, or qubits, are missing."

Comments

I have failed to convince Slashdot that I am human

[Anonymous Coward]

Maybe the qubit computer can do better.

This may be slightly off-topic, but

[Anonymous Coward]

Seriously WTF is Quantum Computing? I've looked at the wiki articles and googled things, and I'm still lost. I did read that unless you have an education in this area you just won't get it, but help me out here.

Re:This may be slightly off-topic, but

[mrsteveman1]

They are computers that leap from datacenter to datacenter, solving previously unsolvable problems, and hoping each time that the next leap will be the leap home.

Re:This may be slightly off-topic, but

[jpmorgan]

To truly understand a quantum computer you need a fairly strong understanding of linear algebra, although knowing quantum mechanics isn't actually necessary. I'll repost an explanation I wrote for another site:

Not 100% accurate, but here's a rough way to understand a quantum computer: If you've ever heard of the concept that whenever there's some chance, the universe 'splits' and both events occur, that's what's going on. When the quantum computer makes a qubit 1 and 0 at the same time, it basically uses a truly random event to determine which value the bit will be. The universe 'splits' and down one path there is a 1, and down the other there is a 0. Except the quantum computer 'splits' the universe in such a way that the two universes can interact with each other. It is even possible to have the quantum computer compute something on every input at once and then search through all the different universes to find an answer; this is known as Gover's algorithm.

The critical part is coherence: making sure that the only difference between the different universes is inside the quantum computer itself. So long as coherence is maintained, the universes can merge back together and all you're left with is the right answer (99.99999% of the time). If coherence isn't maintained then the universes can't remerge, and you don't get a correct answer. Decoherence is actually extremely hard to deal with, and the biggest engineering challenge in designing a quantum computer.

Re:This may be slightly off-topic, but

[xerent_sweden]

So basically it's quantum physics applied on computer science. Computers of today are based on semiconductors and diodes, which allows us to build electric circuits with memory. In this case, it's voltage applied or voltage off - one or zero. Quantum computing is a whole new world of computing; because it's based on the principles of quantum physics. This means that a quantum computer does not resemble the computers of today at all. In a quantum computer, information is stored in "qubits", which is 0, 1 or "undetermined / both". This is a direct application of the wave/particle duality of matter (wiki: De Broglie-wavelength). Working out how a quantum computer - which behaves totally differently from anything we have today - and constructing such a device is really hard. Theoretically, such devices would be more efficient than our computers - and that's an understatement. This story means that we've taken yet another small step towards practical quantum computers, but also that it'll be reposted at least 100 times before working quantum computers are reality. (Off the top of my head, please correct me if I wrote something in error. Thanks! :)

Re:This may be slightly off-topic, but

[MichaelSmith]

The critical part is coherence: making sure that the only difference between the different universes is inside the quantum computer itself. So long as coherence is maintained, the universes can merge back together and all you're left with is the right answer (99.99999% of the time).

How does the observer in the universe with the right answer know their answer is right?

Re:This may be slightly off-topic, but

[xerent_sweden]

How do you know you're asking the right question?

Re:This may be slightly off-topic, but

[jpmorgan]

Typically with these searches you know the answer you want, and you're interested in which input gives you that answer (the inverse problem). An important caveat about Grover's algorithm is that, while it's significantly faster than classical unordered search, it's still non-polynomial.

Re:This may be slightly off-topic, but

[FooAtWFU]

You might check it with a classical-computing algorithm. For NP problems, verification of the answer is often substantially faster than computing the answer itself.

Re:This may be slightly off-topic, but

[RiotingPacifist]

Can they also eliminate lots of latency by doing the computation BEFORE reading the file?

Re:This may be slightly off-topic, but

[Pseudonym]

Usually the answer is one that's difficult to compute but easy to check, such as any problem in NP. Checking that you have a factor of a number is much easier than producing a factor, and checking that a proof is correct is much easier than producing a correct proof.

The other option is to simply run it more than once. If you have an algorithm which is wrong 1% of the time (and that 1% is uncorrelated to the "input"), then if you run it ten times, the chance that all of them are wrong is extremely small.

Having said that, the "many universes" model is, according to most quantum mechanics, not an accurate picture. It's better to think of quantum algorithms as being probabilistic algorithms that works with quantum probability theory rather than classical probability theory.

Re:This may be slightly off-topic, but

[Anonymous Coward]

To understand how it works you'll need a degree in theoretical physics. To understand why you'd want to use it, you'll need at least a course in linear algebra or several in computer science.

This isn't a concept you can explain to a layperson with a page of text. This is going to be an increasingly common problem as technology advances.

Basically, though, interesting properties of quantum particles allow you to preform multiple computations simultaneously on a single circuit.

Re:This may be slightly off-topic, but

[Anonymous Coward]

Because the pan-dimensional mice told me it's the right question, okay?

Re:This may be slightly off-topic, but

[blincoln]

f you've ever heard of the concept that whenever there's some chance, the universe 'splits' and both events occur, that's what's going on. When the quantum computer makes a qubit 1 and 0 at the same time, it basically uses a truly random event to determine which value the bit will be. The universe 'splits' and down one path there is a 1, and down the other there is a 0. Except the quantum computer 'splits' the universe in such a way that the two universes can interact with each other. It is even possible to have the quantum computer compute something on every input at once and then search through all the different universes to find an answer; this is known as Gover's algorithm.

As big a fan as I am of the Many Worlds theory, and as much as I think it's the one that makes the most sense in terms of explaining quantum phenomena, my understanding is that it's far from accepted as fact, with the Copenhagen interpretation being in the lead.

So to keep things on an even keel, is there a similarly straightforward explanation that can be given which doesn't depend on Many Worlds?

Re:This may be slightly off-topic, but

[iris-n]

You just couldn't resist using Everett's interpretation, could you?

I don't think it is a good idea using it to explain something to laymen. They usually end up thinking that quantum mechanics is some kind of inaccessible black magic.

Just to be clear here, it is possible (and it is what's done most of the times) to describe quantum mechanics without ever talking about splitting universes.

Let's see: the qubit can hold some combination of 0 and 1 (NOT 0 and 1). By the same reason (superposition), the quantum computer can perform multiples paths of computation at the same time, which can be used to accelerate the computation of some algorithms.

Quantum computers are quite sensible to noise; it causes decoherence, which can be understood as a loss of quantumness. In other words, a qubit that suffered too much decoherence can't hold a superposition of 0 and 1 anymore.

See? It wasn't that difficult.

Re:This may be slightly off-topic, but

[sanman2]

Ever seen that Superman comicbook issue where he changes back and forth between Superman and Clark Kent so fast that he appears as 2 people in front of the media, and fools them into thinking that Clark and Superman are 2 different guys?

Well, at the tiny smallscale - aka, the quantum level - small particles are being buffeted between different states so quickly, that to us it can look like they're in 2 states at once (like being in 2 different places at the same time - like that Superman comic)

If you're Superman able to use his superspeed to fool people into thinking you're in 2 places at the same time, then you could lead 2 different lives, or even have a conversation with yourself on camera.

If you're a qubit able to be in 2 different states at once, then you could be used to perform twice as many state operations as a regular bit. And if there are 2 qubits, then they can do 4 times as many operations, 3 qubits can do 8 times as many, etc, etc.

So the advantages pile up rather quickly.

Re:This may be slightly off-topic, but

[dwarfenhoschi]

I dont need any degree to know IÂd use it...its a freakin quantum computer, of course i would want to use it. Which Geek doesnt ?

Re:This may be slightly off-topic, but

[ajs]

Quantum computing is a whole new world of computing; because it's based on the principles of quantum physics. This means that a quantum computer does not resemble the computers of today at all. In a quantum computer, information is stored in "qubits", which is 0, 1 or "undetermined / both".

Yeah, I'm still not buying it. Quantum computing has yet to do anything that lives up to even its basic promise. If it's possible to harness these states, we should have been able to demonstrate, at the very least, the capacity for computation on the scale of, say, the average pocket calculator. And yet, we've still gotten nowhere. Why? Well, there are many possible reasons, but I tend to favor the simplest: quantum mechanics is a field that is built on some very nice math and as many intersections with reality as we've been able to test, but fundamentally we don't really understand what's going on at the level of the atom, much less at the level of its constituent parts. As we gain that understanding, our math is likely to be revised and refined several times.

Put simply: we're like Aristarchus of Samos measuring the relative sizes and distances of the sun and moon. He was more accurate than any before him, and his understanding drove countless others' discoveries, but if he'd tried to put a man on the moon using that math, he would have failed.

We're doing roughly that: trying to put a man on the moon at quantum scale, and while the discoveries of Plank and Dirac and all of their successors to the current day have enlightened us as to the nature of the quantum world, we're still not so much farther along than Aristarchus. I expect there to be at least one more wave of truly physics-shattering discoveries on par with the uncertainty principle before we even start to be able to perform real computation at the quantum scale. Even then, it's entirely possible that those discoveries will invalidate the entire idea of using superposition for computation.

Then again, I could be completely wrong, and quantum computing could be workable tomorrow. Just don't go betting the farm on it.

Re:This may be slightly off-topic, but

[SeekerDarksteel]

Wow, a decent summary of quantum computing on the internet. It's so weird not having to pull out the baseball bat and perform some facial readjustment in a qc thread. Just a little added information. When we refer to qubits as being "both" 0 and 1 at the same time, it's not necessarily a 50/50 split. It is in the form (a+bi)|0> + (c + di)|1>, where |0> refers to the 0 state and |1> to the 1 state. |a+bi| = sqrt(a*a + b*b) is the probability that, if measured in the 0/1 basis, it will result in 0, and |c + di| the probability it will result in 1.

The presence of i (the imaginary number, in case that wasn't clear), is important. Also, you can measure a qubit in any basis, not just 0/1, which is actually vital to the way some quantum algorithms work. (Notably quantum key exchange, which relies on the fact that a potential eavesdropper doesn't know what basis he should be measuring the qubit in.) A good way to imagine a single qubit is a bloch sphere. Imagine a sphere, where straight up is 0, and straight down is 1. Anything on the equator is a 50/50 superposition of 0 and 1.
Also, to say that quantum computers are more "efficient" than classical computers isn't quite precise enough for my tastes. It's not that they're capable of doing the same things as a classical computer can, just faster. It's that they're able to do things classical computers simply cannot do due to the way superposition works. And those things allow it to solve a number of problems more efficiently.

Re:This may be slightly off-topic, but

[Anonymous Coward]

I for one think that stochastic electrodynamics and the zero-point field are going to win out. Many-worlds crackpots. It's not symmetrical or beautiful at all for there to be a universe exactly, exactly the same as this one, except there was a uranium atom on Pluto that decayed a minute earlier. Or one exactly, exactly the same, except that there was a single hydrogen atom in Sirius whose electron jumped two levels instead of just the one we observe here.

Re:This may be slightly off-topic, but

[Anonymous Coward]

Let's truly see how far the rabbit's hole really goes....

Re:This may be slightly off-topic, but

[Artifakt]

It's not really better (or worse). One of the basic postulates of Quantum Mechanics is that several interpretations seem to fit equally well, and there's no mathematical reason to pick one of them and decide it's superior to the others.
      Psychologically, it's definitely less mind blowing for most people to treat a lot of quantum processes as something happening to probabilities rather than objectified things. It's probably much less mind numbing for the average person, to claim, for example, that the universe at our level seems deterministic only because the underlying state is so purely probabilistic, than it is to insist the whole universe splits every time a state vector collapses, but both are really remarkable claims, a lot of formally trained philosophers would find either equally disturbing, and the math itself doesn't show a preference.
        I confess I don't like the term 'collapse' much when referring to state vectors. It has a certain negative sound to it. It seems to imply the quantum realm is somehow superior to the classical one. Like the quantum level is heavenly and things fall into our mundane world like Lucifer leaving the divine presence. I personally prefer the word "reification" (Latinate for 'thing becoming'), meaning the quantum level isn't just probabilistic, it consists of probabilities, whereas in the classical universe, we find real things instead. But that's a linguistic preference, the math doesn't specify which interpretation is 'better'.

Re:This may be slightly off-topic, but

[AnyoneEB]

There have been very small quantum computers demonstrated. IBM made a 7-qubit one and ran Shor's algorithm (for polynomial-time factoring) on it in 2001. As far as I can tell, that is the highest number of qubits anyone has demonstrated in a quantum computer.

Re:This may be slightly off-topic, but

[Anonymous Coward]

Excuse me, I have to retrieve my brain which just splattered across the walls.

Re:This may be slightly off-topic, but

[Anonymous Coward]

Till it's final leap where is settles on the Enterprise for a while. :-)

Re:This may be slightly off-topic, but

[Anonymous Coward]

??? WTF was this response. I know both LA and QC and this is not accurate. At best it is a finite interpretation of non-quantum applications of QC (else why not 100%?)

The Q was what is QC. Briefly QC is (both real and conceptual) replacing bits by qubits.

In the conceptual setting this mean replacing the set {0,1} with the line segment [0,1]. or another way to think of it is adding middle (conditional) grounds between yes and no (or true and false, black and white, hungry and full, drunk and sober, ...)

In real terms it (currently) means adding a lot of undecidability to the algorithm/program/process. Most other posts here seem to refer to this or applications currently associated with this.

Re:This may be slightly off-topic, but

[Anonymous Coward]

42?

Re:This may be slightly off-topic, but

[smallfries]

Ziggy computes a 98.3% chance that is the correct definition for Quantum Computing.

Re:This may be slightly off-topic, but

[Hucko]

Before or after the sacrifice of a naked virgin in the full moon with a quicksilver spoon?

Re:This may be slightly off-topic, but

[Anonymous Coward]

I'm too young to die!

Re:This may be slightly off-topic, but

[giuseppemag]

This sounds awfully like the way Prolog works...

Re:This may be slightly off-topic, but

[tetha]

You have to be aware that any result a regular computer computes is also correct only within a certain probability. Once the quantum computers success probability is higher than the probability of flipping a bit inside a regular CPU, you are done. You are not only as good as it probably gets, you are as good as regular computers.

If you don't trust the Quantum computer then, you have to stop using any computer.

Re:This may be slightly off-topic, but

[maxwell demon]

I consider that a very bad explanation of quantum computers (and yes, I work in the field of quantum information, so I know quite well about it). Nothing against many-worlds, but using it to explain a quantum computer is IMHO misplaced. The working of quantum computers is "interpretation-invariant" and adding many-worlds here only muddles the waters.

Even the usual statement that a qubit is "at the same time 0 and 1", while in some sense true, isn't really helpful. Indeed, a single qubit can be modeled by direction in three-dimensional space (for most implementations it's an abstract space, but if you use the spin of spin-1/2-particles to represent the qubit, then those directions are literally the directions of real space). Operations on a single qubit (other than measurement, which is special) are just rotations in that space. Where the power of quantum computing comes from is entanglement: If you have several quantum systems, the states they can assume are more than just "the first qubit is in state X, the second qubit is in state Y". There are "entangled" states where the single qubits are in no single state, but the whole system is still in a well defined space.

The whole point is that for classical systems (even classical analog systems), the state for the whole system is the direct sum of the states of the separate systems, while for quantum system, it's the direct product. That is, if a classical system has an n-dimensional state space, then k copies of it have an n*k-dimensional state space. That is, the size of the state space grows linearly (of course the number of states grows exponentially because every dimension gives a new factor). OTOH, for quantum systems, k copies of a system with an n-dimensional state space have an n^k-dimensional state space. That is, the dimension of the state space grows exponentially rather than linearly. Therefore it's not surprising that for some problems, you get an exponential speedup: By adding a linear amount of physical resources (qubits) you add an exponential amount of computational resources (states space dimensions).

Now those extra dimensions can only be used in very limited ways, therefore not every problem gets an exponential speedup. At that point it should be stressed that those are state space dimensions, not real space dimensions; e.g. two classical particles in three-dimensional space have together 12 state space dimensions (for each particle 3 dimensions for position and 3 dimensions for momentum; note that the classical physics state space is usually called phase space).

Re:This may be slightly off-topic, but

[maxwell demon]

Quantum computers are good for problems where the reverse problem is easy. Take factorization: It is hard to factorize a large number, but if someone gives you two numbers and claims those are the factors, it's easy to check if they multiply to your number.

Re:This may be slightly off-topic, but

[maxwell demon]

42?

I just tried to run Shor's algorithm on that number. The factors turned out to be 6 and 9.

Re:This may be slightly off-topic, but

[maxwell demon]

I confess I don't like the term 'collapse' much when referring to state vectors. It has a certain negative sound to it. It seems to imply the quantum realm is somehow superior to the classical one. Like the quantum level is heavenly and things fall into our mundane world like Lucifer leaving the divine presence.

Well, in some sense it is so. It's just not Lucifer who destroys the quantum heaven, but decoherence.

Re:This may be slightly off-topic, but

[Vu1turEMaN]

When the answer is 42.

Re:This may be slightly off-topic, but

[Vu1turEMaN]

Which is like.....99.99999% of Slashdot?

The other .00001% had arranged marriages.

Re:This may be slightly off-topic, but

[cfortin]

Ya know, alot of these 'summaries' are not really helpful, so I'll take a shot :).

QC for the most part can be thought of in the same fashion as convenetion computer
science, qbits == bits, 'transistors', memory ... etc.

The really cool part, and the part that makes it very interesting to many, is a certain property
of the qbits. Normal bits are independent, each being calculated and contributing to further
calculations on its own. In a QC, then qbits are 'entangled', which can result in one qbit
being effected by the calculations being performed on another. Knowing this, you can
design algorithms to perform certain types of math much much faster than a normal
computer could. Notice that the speed up isn't in clock rate, or individual calculation rate,
but rather in 'bang for the buck' in each calculation. This can change the calculation time for
a big factorization, for example, from 'next millennia' to 'next week', and more inportantly,
if you add a bit to the number you are factoring, the calculation time for a QC would raise
to '1 week+1 minute', whereas a convention computer's calculation time would go from
'1 millennia' to 'life of the universe'.

For an example of such a QC algorithm, see

http://en.wikipedia.org/wiki/Shor's_algorithm

Re:This may be slightly off-topic, but

[RiotingPacifist]

The analogy isn't great, and all responses to do with it being easy to verify the answer are wrong. if the QC just gives you a wrong answer as often as a guess would, which is implied in the responses, then there is no point using a QC!

Imagine a game where you have to guess the correct input to get an output (one of these games is called factorisation), QC is a way of cheating at these games, instead of actually trying all the inputs the QC tries them all the ones that give the wrong answer cancel! The interpretations, i don't know how something that fundamentally can't be verified can be called a theory, are to do with explaining when the cancelling/cheating happens but don't really matter much to the science of quantum mechanics, at some point you interpret the answer and use that data and the cheating is already done (e.g you already have the correct answer)

Re:This may be slightly off-topic, but

[Anonymous Coward]

>If coherence isn't maintained then the universes can't remerge, and you don't get a correct answer.

So the rip in the universe remains? But what if it leaks out of the computer? Are we sure it is safe? O.O

Re:This may be slightly off-topic, but

[Anonymous Coward]

My computer was placed into the imaging chamber and then vanished. I always just assumed it was stolen.

Now what about the Evil Computer or the Return of the Evil Computer? The Devil is a Quantum Physicist?

Re:This may be slightly off-topic, but

[RiotingPacifist]

the quantum realm is somehow superior to the classical one

The quantum realm is superior to the classical one, all classical stuff is just a subset of quantum stuff. A ball bouncing off a wall not only obeys the laws of classical physics it also follows those of quantum mechanics.

whereas in the classical universe, we find real things instead

There is only one universe, there are different 'realms/domains' but fundamentally everything obeys the laws of quantum mechanics and the classical universe is just you see on the surface, the "real things" are quantum objects. It happens that for stuff we experience in everyday life stuff follows a more strict set of rules.

One of the basic postulates of Quantum Mechanics is that several interpretations seem to fit equally well,

Its not a postulate, (there are 4 postulates, they are un-testable (from within QM theory) assumptions NOT results) it's simply a result of people wanting an answer to something that is impossible to know.

the math itself doesn't show a preference.

The maths doesn't deal with objects it only ever deals with probabilities, all the interpretations are philosophical ramblings that try and explain what the probabilities mean.

I that the universe at our level seems deterministic only because the underlying state is so purely probabilistic

I think the world is pretty probabilistic and it would be pretty hard to explain the actions of most living beings in a deterministic way!

I personally prefer the word "reification" (Latinate for 'thing becoming')

That assumes that stuff turns into classical objects (which they do not) and it undermines any holgraphic (e.g we only see one outcome) interpretations

Re:This may be slightly off-topic, but

[RiotingPacifist]

but fundamentally we don't really understand what's going on at the level of the atom, much less at the level of its constituent parts.

The problem with most atoms is they deal with a lot of objects (e.g n-body problems), we do however grok hydrogen and have a thorough understanding of the rules of the game. While we probably will get a huge discovery on how the insides of an atom work (and perhaps an other on how the insides of however whatever we find in that works), we know how electrons and photons interact with eachother well enough to construct QC that use these as building blocks.

The Bernoulli principle was know about since 1738 but it took till 1903 to get planes to fly using the principle

Re:This may be slightly off-topic, but

[Anonymous Coward]

Also, to say that quantum computers are more "efficient" than classical computers isn't quite precise enough for my tastes. It's not that they're capable of doing the same things as a classical computer can, just faster. It's that they're able to do things classical computers simply cannot do due to the way superposition works.

No, they cannot. A classical computer is (except for limited memory) as powerful as a Turing machine. And quantum computers don't add anything to that besides greatly improved performance.

Re:This may be slightly off-topic, but

[pjt33]

And if it turns out that P != NP then verification of the answer will always be substantially faster than computing the answer itself.

Re:This may be slightly off-topic, but

[Anonymous Coward]

Yeah, I'm still not buying it. Quantum computing has yet to do anything that lives up to even its basic promise. If it's possible to harness these states, I should have be able to demonstrate, at the very least, the capacity for computation on the scale of, say, the average pocket calculator. And yet, I've still gotten nowhere. Why? Well, there are many possible reasons, but I tend to favor the simplest: quantum mechanics is a field that is built on some very nice math and as many intersections with reality as I've been able to test, but fundamentally I don't really understand what's going on at the level of the atom, much less at the level of its constituent parts. As I gain that understanding, my math is likely to be revised and refined several times.

Put simply: I'm like Aristarchus of Samos measuring the relative sizes and distances of the sun and moon. He was more accurate than any before him, and his understanding drove countless others' discoveries, but if he'd tried to put a man on the moon using that math, he would have failed.

fixd

Re:This may be slightly off-topic, but

[Hucko]

/.ers go out in the *full* moonlight? Don't you just shrivel up 500,000 times slower?

Re:This may be slightly off-topic, but

[Vu1turEMaN]

Not if you have taco sauce on your head....

Re:This may be slightly off-topic, but

[Pseudonym]

I'm not sure that I agree. The multi-universe interpretation suffers from a very serious, IMO fatal, problem in lay-explanatory power, which is that it's difficult to picture several split universes "interfering" to cancel each other out.

Re:This may be slightly off-topic, but

[buchner.johannes]

Example: decomposition of a number into its prime factors.

Re:This may be slightly off-topic, but

[buchner.johannes]

If we can learn something from the history of computing (transistors, silicone chips, disk space), we know that we are good at aggressive exponential growth. I think they had 1 qubit calculation experiments running 2-3 years ago, and 4 qubit or so last year. Now you can calculate when they will crack AES.

What wasn't mentioned yet is that due to the superposition of states (instead of 0/1), you can define requirements to the state, ideally so that it must be definite. Then you measure it and retrieve the (one) solution. It like calculating with all possible inputs at once. However, it is still just another Turing machine.

Re:This may be slightly off-topic, but

[bh_doc]

Nearly, but not quite. With Superman switching places really fast, Superman is really ever only in one place at a time. Qubits are not - they really can be in two different states at the same time.

The bit about state operations isn't really true. You can't do twice as many operations, but with quantum mechanics you can do some new, really funky operations that you can't do with classical bits. Like entanglement.

It's possible to figure out ways to use these multiple states and funky operations to solve problems faster than you can classically, but it's really hard to understand them on any intuitive level.

Re:This may be slightly off-topic, but

[bh_doc]

You could couch the argument as not regarding whole universes, but rather regarding only the quantum system (computer) involved. It's basically the same argument: the system splits into many states, they must be kept in coherence, and then they recombine at the end when you perform the measurement and get your answer.

Copenhagen just has that extra measurement step which disconnects the observer and the system (which IMHO is a bit arbitrary), but otherwise it's very similar. And you can simply generalise the system in the above argument to include the entire universe and we're right back where we started.

works with half their components missing

[beckett]

imagine half a beowulf cluster of these things!

Re:works with half their components missing

[Kratisto]

I wonder if it can run half a Linux kernel.

Re:works with half their components missing

[dmartine40]

Hmph! It'd just be a bunch of Schrodinger's cats taped together!

Re:works with half their components missing

[Captain Electrode]

So ... if it took 42 cats, it'll still work if 21 are ... huh?

Re:works with half their components missing

[gronofer]

If it works with half the components missing, why not omit the other half too? It worked in Permutation City.

Begs the Question

[ObsessiveMathsFreak]

In related news, another reader links to an Australian study indicating that quantum computers "can continue to work perfectly even if half their components, or qubits, are missing."

Uhhhh....Hmmmmm....

Re:Begs the Question

[MichaelSmith]

In related news, another reader links to an Australian study indicating that quantum computers "can continue to work perfectly even if half their components, or qubits, are missing."

Uhhhh....Hmmmmm....

I wonder if it keeps working when all of its components are missing?

Re:Begs the Question

[John Hasler]

Only half the time.

Re:Begs the Question

[Anonymous Coward]

In related news, another reader links to an Australian study indicating that quantum computers "can continue to work perfectly even if half their components, or qubits, are missing."

Uhhhh....Hmmmmm....

I wonder if it keeps working when all of its components are missing?

Only half of the time.

Re:Begs the Question

[jpmorgan]

That's a horribly misleading summary. Quantum computation is plagued with error... the same thing occurs in classical scenarios but we have error correction schemes to deal with that (for example, error correcting codes). Analagously there's quantum error correction which lets you recover your quantum information after corruption, however previously it was fairly limited in capability. The new research is a way to improve quantum error correction, so that the original information is recoverable after much more substantial corruption than was possible before.

Re:Begs the Question

[Eternauta3k]

Even better:

• Remove half of the components
• You still have a working computer
• Repeat

</misinterpreting the summary for fun and profit>

Re:Begs the Question

[Anonymous Coward]

well, not quite true. QC is plagued by decoherence under certain circumstances.
There are developments such as decoherence free subspaces which could avoid a
loss of coherence.
and this is not with regards to the parent... but im appalled at how slasdot deals with non
IT related questions (perhaps, /. is equally off the mark on IT related topics but since im not from
IT maybe i don't realize it? )

Entangled Backups

[Clever7Devil]

Nothing's going to screw with my offsite storage on the other side of the galaxy.

Re:Entangled Backups

[PieSquared]

No, no, no. That's an off-site *mirror*, not a backup. Just... hyperdimensional RAID 1.

Re:Entangled Backups

[Clever7Devil]

"Hyperdimensional RAID 1" Sounds like a Dalek Universal Domination plan. "EXTerminate!"

Take cover!

[SEWilco]

Release the cat jokes!

Now then...

[FunPika]

Can their quantum computers run Vista?

Re:Now then...

[Anonymous Coward]

That would be great - a UAC prompt that you could push both 'Allow' and 'Deny' on!

The scientists may have a bit more work ahead, though, as they don't yet have a qubit state for FILE_NOT_FOUND.

Re:Now then...

[InfiniteLoopCounter]

The scientists may have a bit more work ahead, though, as they don't yet have a qubit state for FILE_NOT_FOUND.

That's only because it is a redundant state. When you search for file X you now get - "At least 50% of file X found in folder Y with at least 90% of its contents intact." Although, immediately after the search, the office assistant still taunts at you when you are not looking.

Re:Now then...

[Captain Electrode]

In quantum computing, clippy pwns you!

Inadequate and stupid

[sonicmerlin]

is how I feel whenever a discussion of quantum computers come up.

Re:Inadequate and stupid

[Ritz_Just_Ritz]

Probably a step up from how you'd feel if a discussion of women and relationships came up. ;)

Re:Inadequate and stupid

[promythyus]

that's what she said?

Oblig. Bad Car Analogy

[PPH]

...quantum computers "can continue to work perfectly even if half their components, or qubits, are missing."

Based on the number of spare parts I end up with after every time I tinker with it, so can my car.

oh hai

[Anonymous Coward]

oh hai, im livin all nine lives simultaneously!

Quick Quantum Computing Explanation

[Anonymous Coward]

In the quantum universe, you can take a fundamental property like "position" and put a particle into a superposition state. A particle can be at position a with some probability and position b with some probability. Amazing, huh?

Now, the second component is that you can use quantum entanglement to create superposition states of multiple particles. Einstein had this great idea where measuring the state of one particle tells you what the state of another entangled particle is. This is fundamentally what allows for the improvement over classical algorithms. You can know the states of two things with one measurement.

One more example of quantum powers: When you put a particle in a superposition state, you can store a lot of information this way (sort of). You can give it a probability to be in place a of: 0.1234567891 and probability to be at place b of 1 - 0.123456789. However, you have to make repeated measurements to access this information.

Anyway, it's a fascinating subject. Caltech has a good page online somewhere. I hope that people everywhere can get an appreciation of this brilliant new field!

Don't worry

[Anonymous Coward]

Most of us feel the same. Because of that, large percentage of people who even click these stories are from that minority that understands something about it.

Then there are people like you and me who click to see if comments offered us some insight to the subject.

But most likely the largest group here is people who know just enough of the subject to think that they understand it though they really don't.

Re:Don't worry

[ButtercupSaiyan]

How true. My ignorance is honest; their ignorance is derived from knowing just enough to get themselves into trouble. The older I get, the more I realize that what I was "taught" in higher education was based on shaky or uncertain principles and I had to accept that what I actually know may not be entirely true or accurate at any time, ever.

Good Lord

[rastoboy29]

Thanks is so *fucking* amazing.  It's becoming clearer every day that quantum computing is in the state silicon computing was back in the 50's.

Things are going to get very weird!

Re:Good Lord

[raktul]

Good analogy, I will wait 36 years then before trying to figure it out since it was not till 86 that I was born.

Re:Good Lord

[Anonymous Coward]

assmaster

Cat joke no. 1

[jonaskoelker]

I can has measurement?

Applicaton

[mhajicek]

According to my understanding of it, a quantum processor will be best for large matrix operations. What hardware do we have that does that now? Video cards! So the race is on; who will release the first truly quantum GPU, ATI or Nvidia? And will there be an exploitable glitch that moves the hostess' undergarments one foot to the left?