Will Quantum Computing Make It Out of the Lab?

alphadogg writes "Researchers have been working on quantum systems for more than a decade, in the hopes of developing super-tiny, super-powerful computers. And while there is still plenty of excitement surrounding quantum computing, significant roadblocks are causing some to question whether quantum computing will ever make it out of the lab. 'Artur Ekert, professor of Quantum Physics, Mathematical Institute at the University of Oxford, says physicists today can only control a handful of quantum bits, which is adequate for quantum communication and quantum cryptography, but nothing more. He notes that it will take a few more domesticated qubits to produce quantum repeaters and quantum memories, and even more to protect and correct quantum data. "Add still a few more qubits, and we should be able to run quantum simulations of some quantum phenomena and so forth. But when this process arrives to 'a practical quantum computer' is very much a question of defining what 'a practical quantum computer' really is. The best outcome of our research in this field would be to discover that we cannot build a quantum computer for some very fundamental reason, then maybe we would learn something new and something profound about the laws of nature," Ekert says.'"

Comments

That's just life

[rgbe]

Quantum Computing isn't going to work immediately, it's just life. It's going to make small progressions over time. Eventually there will be advancements that will make them practical for a given purpose. They will follow something like a "Moore's Law" of Quantum computing. Then some intelligent person will utter "I think there is a world market for maybe five Quantum computers"!!!

Details of the current state

[JoshuaZ]

The current state of the field is advancing. The real problem as discussed in TFA is scaling quantum computers in a useful way that can still do error correction. Shore's algorithm which allows you to quickly factor numbers using a quantum computer requires on the order of n qbits to factor an n bit number. So if one wants to factor say a 300 digit number used in some public key crypto system you would need to control around 300 qbits. The technology for that is clearly very far. There's been recent work using superconducting systems and using quantum dots for qbits both of which look more promising than previous systems. (The first experiments were done with NMR systems which are clearly not very scalable).

From a strictly theoretical compsci perspective, the set of things it seems that quantum computers can do seems to be growing larger. Recent work by Scott Aaronson and others suggest that BQP (the set of problems which can be easily solved by a quantum computer with a low probability of error) may not lie in the polynomial hierarchy at all. http://arxiv.org/abs/0910.4698. This is a much stronger claim then the claim that BQP doesn't lie in NP. This raises the hope that there may be some problems thought of as extremely difficult that lie in NP. However, trying to actually prove any strong results at this point is likely going to be really tough. At this point although many suspect that BPP (the classical analog of BQP) is equal to P, at this point we can't even prove that BPP lies in NP. In many ways theoretical comp sci is still very much in its infancy.

Re:High Frequency Trading

[0123456]

When high frequency trading finds a way to use this to make more money, you better believe they will make it work.

That'll be fun. You won't even know whether you own a stock until you open the box and look.

I suspect it will work

[TheSync]

1) We have built qbits
2) We have entangled qbits
3) We have implemented the CNOT which is the universal gate for quantum computing (similar to NAND/NOR universal gates in classical computing)

The question is scaling up number of qbits, increasing coherence times (and possibly using coding solutions to reduce decoherence problems).

We have a number of quantum algorithms waiting to be implemented, and even have quantum programming languages that you can run simulations on at home today. And there is even a LinkedIn Group on quantum information science.

But I must admit that it could end up like fusion. We have all the basic theoretical knowledge of how to do fusion, and we can do a bit of fusion in the lab, what we lack is the engineering knowledge to achieve enough fusion on a large enough scale to make it practical.

Re:I suspect it will work

[cjonslashdot]

First of all, I must disclose that I cannot speak authoritatively on this. While I know quantum mechanics and nuclear physics, I have never studied the problem of quantum computing. Therefore, take my opinion here on this topic with a grain of salt.

But I must confess that intuitively, it seems improbable. There is no "free lunch". Computing is a process of creating information. There is no shortcut for that. The primary challenge with quantum computing seems to be about maintaining adequate coherence, and I suspect that that maintaining coherence throughout a calculation will be equivalent in some manner to performing the calculation in a linear manner. But time will tell.

Re:I suspect it will work

[FrangoAssado]

(I'm not a physicist, but I have studied some quantum computing.)

Even though I suspect it's wise to listen to a physicist's intuition on these matters, I think your intuition might have been clouded by the hype surrounding quantum computers. The truth is that there's really no free lunch. Nobody (outside the media) claims that quantum computers instantly solve all kinds of problems.

Think of it this way: some things in quantum mechanics are very hard to simulate using classical computers (it's much harder than simulating classical mechanics). So, it seems reasonable that, if you have some way of using quantum mechanics to do the calculations, you can do better than classical computers. I believe that Feynman was one of the first people to suggest that. He was actually talking about using a quantum system to calculate the behavior of another quantum system, but a quantum computer is essentially a slight generalization: using a quantum system to calculate something else, not necessarily the behavior of another quantum system.

The problem becomes: what kind of calculations can be improved by using a quantum system? There are strong indications that not every kind of problem gains too much from quantum computers: for example, most complexity theorists believe that quantum computers cannot solve NP-hard problems. One of the only kind of problems we have found so far that gain a lot from it is factoring integers.

Let's not forget...

[Nethemas the Great]

the history of the PC. How many decades did it take for us to get where we are? The first PC was some 50 years in the making and by today's standards was downright laughable in its capabilities. The first computers weren't Von Neumann machines either. You had to have a team of dedicated operators reconfigure patch cables between between outputs and inputs for each an every calculation! To be so pessimistic so early in the life of quantum computing is insulting to the progress we've made so far which is considerably outstripping the pace of development of the modern computer.

Re:Let's not forget...

[JoshuaZ]

The key issue for quantum computing isn't that it will allow fixed increases in performance by some factor. The key is that it allows asymptotic increases. Thus for example, Shor's algorithm allows you to factor integers at a rate which is asymptotically better than classical factoring algorithms (although we can't actually prove that no better classical algorithm exists. This is a statement that is strictly stronger than claiming that P != NP). This is part of a general pattern. So, as computational power and the need for computational power increases, the advantage that quantum computers have will grow larger. It won't be a fixed factor.

In my view a computer a million times more performant is very useful however in the end even while this may seem impressive these sorts of advancements do not hold a candle to the origional promise of QC.

I'm not sure what you were expecting quantum computers to be able to do. There's a lot of media hype which is made worse by people who just don't understand stuff. For example, there's no known way to solve any NP complete problem in polynomial time on a quantum computer. Similarly, while quantum computers can break many public key crypto systems (such as those based on the difficulty of factoring large numbers or on the closely connected problem of the discrete log), they can't break every public key cryptosystem. Quantum computers aren't magic and the people working with them haven't said otherwise.

Re:Been out of the lab for over a decade now.

[Anonymous Coward]

source?

schizophrenia

Quantum Computing

[Toonol]

While I'm highly skeptical about building a useful general-purpose quantum computer, I think that there may be great value in incorporating that tech into traditional computers. In other words, a four-qubit computer may be nearly useless except for very specific problems; but if it was part of your desktop computer, it would give it a large boost in all sorts of power.

For instance, encryption is highly related to compression. I believe that a quantum computer would be highly efficient at compressing and decompressing data... which is a task CPUs (and GPUs) do a lot.

Re:Will Quantum Computing make it out of the lab?

[Pope]

Now you'll never know its momemtum...

Damn, now we'll be stuck at this stage of development forever!

Re:Would've been first post

[Runaway1956]

What's with those qubits, anyway? Wasn't Noah's ark so many qubits long, so many qubits wide, and some amount of qubits high? WTF? If the quantum computer people are going blblical on us, we may NEVER see a working computer! After all these years, no one is quite certain what the hell a qubit was in the Bible. How are they gonna know what a qubit is inside a computer?

Just look at the numbers!

[hweimer]

There has been an exponential increase in the number of qubits under control since the first serious experiments started almost two decades ago. If the current trend continues, we will have usable quantum computers between 2020 and 2023.

As a former QC researcher:

[drolli]

Yes. it will. the time frame for QC leaving the lab is something from 15 years to 50years. If it doesn't work in the next 50years it means we understand something about quantum mechanics significantly wrong (or we figured QC is useless for some reason).

There are several milestones:

1) implementing single qubits (done in many systems) and high fidelity readout (done on a few systems)

2) high fidelity operations on single qubits (done on some systems)

3) controllable coupling of qubits (done on some systems) witn good on-off ratio (done on a few systems) in a decent architecture (only very few experiments AFAIU) with a demonstration of simple QIP algorithms (done)

4) scalability in the production yield for solid state systems (NOT done, by far not) or in the resource usage for other systems (atom chips are promising)

5) Quantum media conversion between solid state and optics (done) with decent fidelity (far, far away) for using QIP in Quantum communication as local processors

6) Error correcting schemes to lower the threshold for 2) to a doable value for building a scalable computer (that is, a computer which gains computational power when ressources are added): theroretical (done) and experimental (far away)

7) Theoretical understanding of QIP Architecture (not done)

6, which implies 1-4 (and depending on the scheme also 5) have been solved is the criterion for building an arbitrary powerful QC for arbitrary money. The more you exceed the absolute thresholds imposed onto 2) and 4) the more power you will gain by adding resources (it could be 10 or 10000 physical qubits needed for 1 logical qubit). The question is: when will it be economical to build it? I cant answer this, but the first thing where it may pay off is for protein folding simulations. We are looking at replacing a 100MW input power classical computer by a some MW input power quantum computer (condensing helium). We may look at power cost savings of 10 to 100million of dollars per year runtime of the QC. Currently the schemes which are predicted to scale with current HW (on the rather optimistic end, i.e. the best experiments ever done) may require roughly a 100Million - 1billion Dollar investment into Hardware alone per QC (hand waving approximation), obviously unacceptable. However if the price goes down by a facto of 10 to 100 (which could happen in the next 20 years if better material or schemes are found), then it would be economical.