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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.'"

129 comments

  1. Lets ask by Anonymous Coward · · Score: 1

    *Shakes the magic 8-electron*

    Reply hazy, try again

    1. Re:Lets ask by Anonymous Coward · · Score: 1

      *Shakes the magic 8-electron*

      Outcome uncertain, try again

    2. Re:Lets ask by Anonymous Coward · · Score: 0

      *Shakes the magic 8-electron*

      Yes and no.

  2. Would've been first post by Ironchew · · Score: 1, Funny

    With just a few more qubits, I could have entangled first post.

    1. Re:Would've been first post by Runaway1956 · · Score: 2

      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?

      --
      "Windows is like the faint smell of piss in a subway: it's there, and there's nothing you can do about it." - Charlie Br
    2. Re:Would've been first post by Anonymous Coward · · Score: 0

      Cubits Noah used Cubits.

  3. Been out of the lab for over a decade now. by Anonymous Coward · · Score: 0

    The NSA used their black budget to build a quantum computer 20 years ago. They went full scale a decade ago.

    1. Re:Been out of the lab for over a decade now. by Anonymous Coward · · Score: 0

      source?

    2. Re:Been out of the lab for over a decade now. by Anonymous Coward · · Score: 2, Insightful

      source?

      schizophrenia

    3. Re:Been out of the lab for over a decade now. by Xaedalus · · Score: 1

      And the world STILL sucks. We do not live under an uber-American world totality where we all sing the National Anthem at breakfast and those of the wrong skin color, temperament, or with irritable bowel syndrome have been quietly taken out back and shot.

      Fat lot of good that super-secret quantum supercomputer in the hands of a secretive US government agency did

      --
      Here's to hot beer, cold women, and Glaswegian kisses for all.
    4. Re:Been out of the lab for over a decade now. by Synerg1y · · Score: 1

      Paranoia

    5. Re:Been out of the lab for over a decade now. by TheRaven64 · · Score: 1

      Well, the problem with the NSA's super-secret quantum computer is that they can't tell other agencies the result of decrypting any message unless they can think of some plausible way of decrypting it without needing a quantum computer. If they did, the world would know that they had a quantum computer and that RSA and related algorithms were totally compromised, and they'd switch to using something else.

      Well, maybe not, but the same situation did occur in the second world war - Churchill didn't allow civilians to be warned of German bombing raids, because doing so would have let the Germans know that Enigma was broken.

      --
      I am TheRaven on Soylent News
  4. Eventually by masternerdguy · · Score: 1

    Once some lab figures out how to do it it will seem so easy in hindsight.

    --
    To offset political mods, replace Flamebait with Insightful.
    1. Re:Eventually by Mashiki · · Score: 1

      I agree. Though I expect that quantum computers will end up being cost prohibitive to the average consumer. What will end being in consumer electronics is some variant of optical processing.

      --
      Om, nomnomnom...
    2. Re:Eventually by TheRaven64 · · Score: 1

      Not just expensive - not that interesting. Quantum computers can't just take algorithms written for classical computers and run them insanely fast, they can run a certain category of algorithm insanely fast. A typical user would be better off with a slightly faster classical computer than an insanely fast quantum computer. For certain applications, a quantum coprocessor might be interesting though,

      --
      I am TheRaven on Soylent News
  5. High Frequency Trading by smileygladhands · · Score: 0

    When high frequency trading finds a way to use this to make more money, you better believe they will make it work. Quantum communication across continents? puhlease.

    1. Re:High Frequency Trading by 0123456 · · Score: 3, Funny

      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.

    2. Re:High Frequency Trading by TheLink · · Score: 1

      Maybe they could arrange with their pals in the stock exchange to entangle things so that no matter what happens, they win :).

      --
    3. Re:High Frequency Trading by Anonymous Coward · · Score: 0

      Didn't they do that already? And provided a proof by demonstration?

    4. Re:High Frequency Trading by Runaway1956 · · Score: 1

      Yep, I remember that, like yesterday. The catch-phrase was something like "To big to fail".

      --
      "Windows is like the faint smell of piss in a subway: it's there, and there's nothing you can do about it." - Charlie Br
    5. Re:High Frequency Trading by Anonymous Coward · · Score: 0

      they did this long long ago, my friend ...

  6. That's just life by rgbe · · Score: 2

    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"!!!

    1. Re:That's just life by cmarkn · · Score: 1

      640 qubits ought to be enough for anybody.

      --
      People should not fear their government. Governments should fear their people.
  7. Details of the current state by JoshuaZ · · Score: 4, Informative

    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.

    1. Re:Details of the current state by drolli · · Score: 1

      Thats 300 logical qubits. It may require many more physical qubits.

  8. Will Quantum Computing Make It Out of the Lab? by idontgno · · Score: 1, Redundant

    Maybe; maybe not.

    --
    Welcome to the Panopticon. Used to be a prison, now it's your home.
    1. Re:Will Quantum Computing Make It Out of the Lab? by ThorGod · · Score: 1

      And, possibly, maybe and maybe not.

      --
      PS: I don't reply to ACs.
    2. Re:Will Quantum Computing Make It Out of the Lab? by Anonymous Coward · · Score: 0

      Yes and no.

    3. Re:Will Quantum Computing make it out of the lab? by Sooner+Boomer · · Score: 1

      The answer is both Yes and No.

      I know the answer...
      ...I looked.

      --
      Chaos maximizes locally around me.
    4. Re:Will Quantum Computing make it out of the lab? by V!NCENT · · Score: 1

      Now you'll never know its momemtum...

      --
      Here be signatures
    5. Re:Will Quantum Computing make it out of the lab? by Pope · · Score: 2

      Now you'll never know its momemtum...

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

      --
      It doesn't mean much now, it's built for the future.
    6. Re:Will Quantum Computing Make It Out of the Lab? by seven+of+five · · Score: 1

      Not as long as you're looking.

    7. Re:Will Quantum Computing Make It Out of the Lab? by im_thatoneguy · · Score: 1

      |Ï(x)|^2

    8. Re:Will Quantum Computing Make It Out of the Lab? by mcswell · · Score: 1

      If it does, my cats want to buy one, so they can determine whether I've woken up in the morning to feed them. The door to my bedroom is shut at night, so for them, until I open the door I am in a state of indeterminate wakefulness.

      (Ok, I'm in a superposition of awake and asleep at other times, too...)

  9. I suspect it will work by TheSync · · Score: 5, Informative

    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.

    1. Re:I suspect it will work by cjonslashdot · · Score: 3, Insightful

      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.

    2. Re:I suspect it will work by NeutronCowboy · · Score: 1

      To some extent, I suspect that quantum computing might well end up with the same problem that quantum mechanics is facing now: it works awesomely great on a very, very small scale, but cannot be used to explain the large scale force of gravity. Similarly, quantum computing might very well work with a few dozen to hundred qbits, but will fall apart at a larger scale where the number of error correcting mechanisms required to overcome decoherence will be too much.

      --
      Those who can, do. Those who can't, sue.
    3. Re:I suspect it will work by Anonymous Coward · · Score: 0

      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)

      Yes, but as per TFS, and as you note yourself, the issue is whether these building blocks can be scaled up to such a size as to do something useful. Quantum mechanics itself gets astronomically more complex in going from a state space of 2 qubits to 100 or 1000 qubits -- i.e., two qubits and single quantum gates is the trivial part.

      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.

      Which means basically nothing given that the issue is not whether we can invent such algorithms, but whether we can actually build the machine to run them on...

      And there is even a LinkedIn Group on quantum information science.

      So we've established that (a lot of) quantum information researchers exist then. That fact is utterly irrelevant to whether a practical quantum computer can be built, you do realize that right?

    4. Re:I suspect it will work by Urkki · · Score: 1

      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.

      It could also be, that we don't lack just the engineering knowledge, we lack the universe with suitable physical laws... But hopefully not.

    5. Re:I suspect it will work by ThorGod · · Score: 1

      I remember Feynman wrote some about quantum computing. He always seemed positive on the idea, and I'm inclined to believe him. (That also ends my claimed background on all things quantum computing. From hereon I'm speculating, so there's no sense in flaming a dreamer - for those who might.)

      A quantum computer, though, isn't a fusion reactor. The end goals for both systems are different. In a sense, the requirement that a fusion reactor eventually sustain itself (as it were) is something a quantum computer needn't achieve. My suspicion is that 'simplification' makes quantum computing much more likely than self sustaining fusion.

      From my perspective, what's more interesting is how quantum computing would impact the world. Information already flows free and fast. I don't think more computational power is going to solve economic nor political woes. If all the questions that can be answered competently are already being answered competently, how are things going to change with some added computational power?* It would probably result in more ingenious gadgets (which in themselves may be blessings).

      *For instance: I don't expect a quantum computer to make modeling the weather and/or human behavior as predictable as a Newtonian physics experiment.

      --
      PS: I don't reply to ACs.
    6. Re:I suspect it will work by ThorGod · · Score: 1

      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.

      As designed by the Sirius Cybernetics Corporation...all of the fatal flaws are perfectly masked by the superficial flaws?

      --
      PS: I don't reply to ACs.
    7. Re:I suspect it will work by Anonymous Coward · · Score: 0

      To add to this, and I'm no authority either, I thought it was well agreed that there was a bound limit between information (energy), physical space, and computational processing? For example, that whole concept of a Black Hole being a large computer. We're talking about orders of magnitudes of processing 'order', opposite chaos, and purposeful control. I think, or hope, we find some find interesting rules about nature, information and processing when we start getting down to the known physical constraints.

    8. Re:I suspect it will work by quax · · Score: 1

      Quantum computing is adiabatic computing. I.e. fully reversible without entropy increase. Hence a complex quantum computation is theoretically not an my more energy intensive then a simple one. Entropy only increases at the end when the final measurement is performed.

      What makes the process tricky is keeping quantum coherence over the length of the algorithm.
       

    9. Re:I suspect it will work by Anonymous Coward · · Score: 0

      Computing is a process of creating information.

      No. It's just rearranging it.

      Quantum computing algorithms work because you can ask a different set of questions than you can with a classical computer. For example, Shor's factoring algorithm works because in the quantum world you can ask "what is the period of this periodic function?" without having to compute any values of the function. Quantum computing is really trying to work out what questions you can ask... so, perhaps, Douglas Adam's was right after all!

    10. Re:I suspect it will work by cjonslashdot · · Score: 1

      Perhaps! LOL

      But once again, I don't want to assert this with any certainty. Just food for thought. Perhaps I am wrong.

    11. Re:I suspect it will work by StripedCow · · Score: 1

      But I must admit that it could end up like fusion.

      At least for fusion, we know that it should be possible both in theory and practice (just look at the Sun for proof).

      --
      If Pandora's box is destined to be opened, *I* want to be the one to open it.
    12. Re:I suspect it will work by FrangoAssado · · Score: 2

      (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.

    13. Re:I suspect it will work by PaulBu · · Score: 1

      I remember Feynman wrote some about quantum computing. -- Yeah, see, e.g., here: http://www.phy.mtu.edu/~sgowtham/PH4390/Week_02/IJTP_v21_p467_y1982.pdf

      Some people say that he coined the term "Quantum computer", others say that he popularized it, and it was originally due to David Deutsch. And of course it was influenced by Fredkin and Toffoli, and others asking about energy requirements for computation. And THAT goes back to von Neumann!

      Now, von Neumann gave us not only classical computer view, currently bearing his name, but also showed the mathematical equivalence of Heisenberg's matrix and Schrödinger's wave formulations of quantum mechanics. I think that I've read it somewhere recently (do not remember where, up to /. crowd to crowdsource it :) ) that the really interesting question is not why quantum computers are taking so long to arrive, but why they were not conceived much, much earlier!

      If all the questions that can be answered competently are already being answered competently, how are things going to change with some added computational power? Well, see P vs. NP (BQP in this case, YMMV) -- there are questions that we were trained not to be asking, knowing that we can not get the answer back before the heat death of the Universe! ;) See Feynman link above, the real impact would be not in cracking RSA, but in simulating (and, thus, being able to engineer) quantum systems. Think better materials/batteries/"gadgets", but also think proteins, cells, your body, maybe your mind...

      Paul B.

    14. Re:I suspect it will work by blahplusplus · · Score: 1

      The real issue is whether it's costs can be brought down and whether it can scale. Quantum computing may stay too expensive for anyone outside of governments and corporations doing serious scientific research. The idea that just because you have quantum bits on one scale, that this scale will continue up as systems get larger is the flaw. You may get scalability but might hit a cost wall. BTW we still don't have flying cars. I use flying cars as an example of drawing a conclusion about the cost of technology and it's feasibility.

    15. Re:I suspect it will work by Anonymous Coward · · Score: 0

      The theory of fault-tolerant quantum computing has been very well developed, is well understood, and has been experimentally tested. Maintaining coherence throughout a calculation is definitely not equivalent to performing the calculation in a linear manner. As Ekert says, the only way quantum computers could break down in this way is if quantum mechanics is wrong. While that would stop quantum computers in their tracks, it would also probably be the biggest scientific discovery of the 21 century, far, far more important than, e.g., discovering the Higgs boson.

    16. Re:I suspect it will work by Permutation+Citizen · · Score: 1

      Yes, and the quantum theory being wrong so you can't possibly make a quantum computer is unlikely. I don't say current physic theories are complete and faultless (they aren't) but any better theory would have to explain experiments already done, including most of quantum non-intuitive stuff used in quantum computing.

      People often understand (because they are told so) that quantum physics applies only at small scale, and not at bigger one. Actually quantum physics works at all scales, and theory of decoherence explains why it seems to get back to classic behavior at bigger scale and higher temperature. There is an article in Scientific American a few month ago about how quantum effect are also seen at larger scale is many cases.

      Any hope that quantum theory is replaced by something more intuitively understandable seems extremely very unlikely to me. As observed outcome of experiment is weird, theory to explain them must be weird also. Actually, the more we understand physic, the more weird it gets, not the other way around.

  10. YES... by Anonymous Coward · · Score: 0

    and NO

  11. Will Quantum Computing make it out of the lab? by DickBreath · · Score: 1

    The answer is both Yes and No.

    It is a superposition of skates.

    -----
    Google: partner with everyone, sue no one.
    Apple: partner with no one, sue everyone.

    --

    I'll see your senator, and I'll raise you two judges.
  12. Let's not forget... by Nethemas+the+Great · · Score: 5, Informative

    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.

    --
    Two of my imaginary friends reproduced once ... with negative results.
    1. Re:Let's not forget... by Anonymous Coward · · Score: 0

      Not to mention an almost arrogant assumption that there will be no breakthroughs. This is like predicting the demise of computers prior to the invention of the transistor or semi-conductor. Some wild accident could happen which unlocks the potential for quantum computers and could propel technology into completely unknown territory. This guy wants to quit before trying.

    2. Re:Let's not forget... by WaffleMonster · · Score: 1

      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.

      My pessimism is driven by a firm belief there is no free lunch in the universe. There is no perpetual motion. There is no well of infinite computation.

      If you think your going to be able to answer questions requiring classic processors having the mass of the sun with a QC having many thousands of entangled qbits in a single coherent system I *believe* this is fantasy.

      If your bar is much much lower.. say cost effective QC on desktops which add 1k, 1m or a billion times performance for some classes of problems over what we have now then yes I agree with you this future may well be possible.

      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.

    3. Re:Let's not forget... by Anonymous Coward · · Score: 0

      We don't have real Von Neumann machines now, due to memory limitations. But we do have working models and software systems that can simulate a Von Neumann machine for most purposes....

      Can't find my password, sorry.

    4. Re:Let's not forget... by hedwards · · Score: 1

      That was more or less my thought, I mean quantum computing is probably a lot further along than when Babbage came up with his difference engine idea. And it wasn't until a century or so after his death that computers finally made their way out of the lab and started winding up in living rooms on a regular basis.

    5. Re:Let's not forget... by hedwards · · Score: 1

      Just because it's hyped doesn't mean that it's not real. Granted it's highly unlikely that we'll get unlimited computational power, but that's hardly reason to believe that quantum computing won't ever happen. Keep in mind that if you asked somebody working in a computer lab back in the 60s or even 80s, what we have now would likely be met with a lot of skepticism as well.

    6. Re:Let's not forget... by JoshuaZ · · Score: 2
      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.

    7. Re:Let's not forget... by Yoik · · Score: 1

      Actually there was an issue of Communications of the ACM on the 25th anniversary of ENIAC (about 1971) that predicted mid 90's microprocessors quite accurately. An IBM 7094 in a wristwatch is the phrase I recall, the brand might be wrong.

      Nobody knew what would happen with components, but the outlines of Moore's law were visible even then.

    8. Re:Let's not forget... by Osgeld · · Score: 1

      PC's are not mainframes, 50 years? some guys in the 70's wanted a computer, half decade later it was already an industry ... I think your skewing this a little too hard

    9. Re:Let's not forget... by Anonymous Coward · · Score: 0

      Your stance is motivated by nothing other than a myopic view of scientific advance. Most of what we have today would look like a ridiculous 'free lunch' to people living 100 or 150 years ago, particularly in computing. But you are taking it for granted because you don't really internalize that you're already living with countless free lunches.

    10. Re:Let's not forget... by WaffleMonster · · Score: 1

      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.

      I'm expecting computational power to scale to the exponent of the number of entangled qbits. Further I expect the number of qbits in the system to run well into the thousands.

      Without the above you will never see a single code of any consequence broken on a QC.

      2^1000 is a number with more than 300 digits and most certainly qualifies as magic to me.

      There is simply not enough matter on earth available to build a powerful enough computer based on any other known principal.

      In my mind arbitrary scaling of n^qbits is in the same category as denying the conservation of energy. I don't believe in something for nothing. I reject the idea it is possible to extract ungodly amounts of computation from the universe simply because it smacks of something for nothing. I hope someone proves me wrong. I'm confident I will die without this ever having been accomplished.

    11. Re:Let's not forget... by WaffleMonster · · Score: 1

      Your stance is motivated by nothing other than a myopic view of scientific advance. Most of what we have today would look like a ridiculous 'free lunch' to people living 100 or 150 years ago, particularly in computing. But you are taking it for granted because you don't really internalize that you're already living with countless free lunches.

      "Nothing other than a myopic view" is a little harsh considering there are only 10^80 atoms in the universe. A 1000 qbit system would perform vastly more classic operations in one single coherent transaction than there are atoms in the entire observable universe.

      There is incremental advancement and then there is absolute lunacy.

      I could use your reasoning in response to someone doubting the viability of perpetual motion machines or to poopoo shannon and nyquisy.

      Nobody knows everything - at any time anything could happen and long held ideas can evaporate in an instant but we often have to make value judgements to get work done. Flailing about without any constraints is often a waste of time and resources.

    12. Re:Let's not forget... by Chris+Burke · · Score: 1

      2^1000 is a number with more than 300 digits and most certainly qualifies as magic to me.

      And? You don't need 2^1000 qubits (or bits) to deal with 1000-binary-digit numbers. You need 1000. Your computer right now can easily handle such numbers.

      There is simply not enough matter on earth available to build a powerful enough computer based on any other known principal.

      Powerful enough to do what? Factor 1000 bit numbers? Well that's a problem with classical computers. Not an inherent principle of the universe, because the universe doesn't operate on classical principles.

      In my mind arbitrary scaling of n^qbits is in the same category as denying the conservation of energy. I don't believe in something for nothing. I reject the idea it is possible to extract ungodly amounts of computation from the universe simply because it smacks of something for nothing.

      "Arbitrary" as in unending, no, but there's little reason to think they couldn't be scaled exponentially for as long as we've done the same with transistors. Unless, as TFA says, we discover some fundamental principle that prevents it. And no, Conservation of Energy is not that principle.

      You seem to think that what matters for determining the feasibility of a quantum computer is the amount of classical computation, and thus size of classical computer, that would be required to perform an equivalent computation. It isn't. That's irrelevant. Quantum computers operate under a different computational model than classic computers. That's why in algorithm classes, when talking about algorithmic complexity, they always include the caveat "on a deterministic computer". QCs are non-deterministic.

      That doesn't make them magic. There are still things a non-deterministic computer can't do any more efficiently than a deterministic one. However there are things that it can do more efficiently. And what constitutes "ungodly" amounts of computation is based on the kind of computation you're doing. There's nothing ungodly about the computation performed in a 1000 qubit machine factoring a 1000 bit integer.

      --

      The enemies of Democracy are
    13. Re:Let's not forget... by JoshuaZ · · Score: 1

      You don't get information from anything in a quantum computation. The total information is the same. The only substantial difference is that you can process some things faster. This isn't similar to the issue of conservation of energy- in that context there's a mathematical law that you can't break. Here there's just a lot of computation that you can do faster. We already know that this can happen at a small scale, the primary issue is scaling it up which seems to be an engineering problem. We don't know of any fundamental laws of physics that say we can't get away with this. Also, the computation involved is probably not ungodly. For example, it is suspected that you can't use quantum computers to solve NP complete problems in polynomial time. So, the computational result is more in the category of very impressive but definitely mortal. Note also that there's been a definite pattern in the last few years of more and more things turning out to be surprisingly easy to compute. The most prominent example would be the AKS algorithm which showed that one could test for primaity in polynomial time on a classical computer.

  13. Obligatory: Will Quantum Computers +2, True by Anonymous Coward · · Score: 0

    run Quake?

    Morons. The answer is NO.

  14. Of course it will. Or not. by bryan1945 · · Score: 1

    Depends on the flavor of cat.

    It is not so much of "will it" as opposed to "when will it." And to what degree of success & usefulness. I'll give the timeline roughly around the same time as fusion.

    --
    Vote monkeys into Congress. They are cheaper and more trustworthy.
  15. At least out of the lab and into the military by Anonymous Coward · · Score: 0

    Given the fact that Quantum Computers will break any, and all, public key encryption schemes, the military simply won't give it up. It's far too valuable.

  16. Re:quantum repeaters??? by V!NCENT · · Score: 1

    We're talking internet right here. The problem faced with long-distance quantum stuff is that the bigger the lenght of the channel, the higher the probability of error.

    So how do you implement this? You make a shitload of entangled particle pairs in such a way that it works like an error-correction-protocol (computers, hmkey? They proces, duh) and then send the result by means of more entagled particle pairs to the next repeater, or until the package has reached its destination.

    You could have Googled that, you know...

    --
    Here be signatures
  17. The Schrödinger's cat ate my conference slide by Anonymous Coward · · Score: 0

    But now that we're all gathered here in Nice, I move that we adjourn to the beach.

  18. Two Qubits... by griffjon · · Score: 1

    Two qubits should be enough for anyone.

    Oh c'mon, somebody had to say it. Might as well save some budding tech CEO from being cursed with that quote for all time.

    --
    Returned Peace Corps IT Volunteer
  19. Realistic answer via a question. by Anonymous Coward · · Score: 0

    How many people have industrial coolers in their homes that can freeze things to 0 kelvin temperatures?
    How many of those people even know what a Kelvin is, other than a horrible name for a kid, or some weird pop group?
    How many people are willing to put up with their qubits dying all the time? Your RAM chips got fried? Pah, that's nothing.

    Until we get these things running in unstable environments, probably not any time soon.

    Yeah, we might be able to sell to rich people and let them take care / destroy it. But considering their current state, not entirely useful for anything really besides research.

  20. CD, DVD, Blu-Ray by kyrio · · Score: 1

    Didn't all of these things take 30+ years to develop?

  21. Too late, it already did... by Anonymous Coward · · Score: 1

    Lockheed-Martin already bought one. It's made by D-Wave Systems and is called the D-Wave One. It is known as the first commercial quantum super computer. It has 128 qbits and has been out for about a year already.

    1. Re:Too late, it already did... by Anonymous Coward · · Score: 0

      While not a general purpose quantum computer it does perform useful "quantum simulations of quantum phenomena" for certain types of problems.

  22. I'm surprised no one has mentioned D-Wave Systems by Anonymous Coward · · Score: 0

    D-Wave Systems

    They are not strictly a quantum computer even though they market it as such, but they are one of a handful of companies in the world who seem to challenge this article's assertion that it won't be commercially viable.

  23. what 'a practical quantum computer' really is by wiredog · · Score: 1

    It has to be able to run Doom. And Barney Doom.

    And, obviously, Linux. OpenBSD would be the Big Win.

  24. Quantum Computing by Toonol · · Score: 2

    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.

    1. Re:Quantum Computing by FrangoAssado · · Score: 1

      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.

      Not really; a four-qubit quantum computer can be simulated very fast in today's computers. It would be completely useless for any practical purpose (unless quantum computer fabrication technology improvements become ridiculously better than improvements on classical computer fabrication technology for an extended period of time).

      To simulate the evolution of an n-qubit quantum computer all you have to do is (essentially) multiply a vector of size 2^n by a series of 2^n-by-2^n matrices whose entries are complex numbers; each matrix multiplication represents one step of the algorithm you're running. There are, of course, many optimizations that can be done depending on the type of algorithm you're running. (Here is a nice list of quantum simulators.)

      Because the size of the vectors and matrices grows exponentially (2^n) with the number of qubits, simulating a quantum computer with a classical computer becomes impractical even for a moderate size. For very a very small number of qubits, though, it's completely reasonable.

      That said, the rest of what you said seems right. Even though it would be possible to run classical algorithms in a quantum computer (i.e., quantum computers are Turing-complete), it would probably be an enormous waste of resources to use quantum computers that way. Unless, of course, quantum computer fabrication technology improvements become ridiculously better, etc.

    2. Re:Quantum Computing by Anonymous Coward · · Score: 0

      To simulate the evolution of an n-qubit quantum computer all you have to do is (essentially) multiply a vector of size 2^n by a series of 2^n-by-2^n matrices whose entries are complex numbers

      Is that all?

    3. Re:Quantum Computing by FrangoAssado · · Score: 1

      Yes, except for the final step, which is trivial (and also fast) to simulate but a little harder to explain: you have to "make a measurement", which can be simulated simply as choosing randomly one of the 2^n components of the vector, according to probabilities that depend on the values of each component. The relative probability of each component can be calculated as the square of the absolute value the component (remember, these are complex numbers).

      So, quantum algorithms have to be designed so that in the end of the calculation (i.e., before the measurement), the vector has all components -- except one (the right answer) -- very close to zero. This means that when you make the measurement, you have a very high probability of getting the right answer. This requirement is what makes it so hard to "program" a quantum computer: you have to find a way to make all wrong answers come up with extremely low probabilities. You can then increase you confidence in the result even more by running the algorithm many times to avoid being fooled by unlucky outcomes. For example, if the probability of getting the wrong result in one run is 1% (=0.01), then if you run the program 5 times the probability of getting the wrong result becomes 0.01^5=0.0000000001.

      This, of course, is all conceptual; actual simulations do all kinds of optimizations depending on the kind of algorithm being run (i.e., if you know some properties of the matrices, you usually don't have to do the full multiplications, etc.).

  25. can it run crisis 2 at full speed with at least 60 by Joe_Dragon · · Score: 1

    can it run crisis 2 at full speed with at least 60fps at full detail?

  26. Re:can it run crisis 2 at full speed with at least by Anonymous Coward · · Score: 0

    Yes, but you both win and lose.

  27. Netscraft Confirms It by iggymanz · · Score: 1

    Quantum computing was dying, or it wasn't. Then Netcraft confirmed it and collapsed the state to dead.

  28. Will require a shift in thinking by wcrowe · · Score: 1

    I imagine quantum computers will be possible, but only after a fundamental change in how we think about and design things. Sort of like how future technology was imagined in the 30's and 40's. It took the invention of the transistor and other solid state devices to get people to re-think how things could be designed.

    --
    Proverbs 21:19
  29. In a word. by kurt555gs · · Score: 1

    No.

    --
    * Carthago Delenda Est *
  30. Re:quantum repeaters??? by V!NCENT · · Score: 1

    that's not a quantum system... that's what the internet is now.

    No shit, Sherlock. But it's not quantum based. How else do you want to make a fully working quantum computer, if you can't have a quantum based network 'card'?

    PS: Google starting English sentences with capitals...

    --
    Here be signatures
  31. Best outcome? by Anonymous Coward · · Score: 0

    The best possible outcome would be that we successfully build a cheap-but-reliable quantum computer, AND learn something fundamentally new about physics (something that makes interstellar space travel practical and affordable, perhaps).

    Oh, if this research could provide a way to cure all human disease and give us eternal youth, that would be even better.

  32. lifeless time by Anonymous Coward · · Score: 0

    quantum computing is just a way to explain (away) that back-door (code) into
    your secured system:
    "How the f#ck did you get in?"
    "By using a "quantum computer"" ....

  33. Partly yes. Partly no. by Anonymous Coward · · Score: 0

    ;-)

  34. Yes by Anonymous Coward · · Score: 0

    Next!

  35. Correction by Anonymous Coward · · Score: 0

    *cubit

    1. Re:Correction by Anonymous Coward · · Score: 0

      Whoosh.

  36. Quantum Summary by mooingyak · · Score: 1

    The quantum summary quantumly mentions many quantum uses of the word quantum.

    And for some filler, maybe they'll make a quantum grill to quantum barbecue quantum burgers and quantum hot dogs.

    --
    William of Ockham had no beard. The most likely explanation is that it was chewed off by squirrels every morning.
  37. Re:quantum repeaters??? by somersault · · Score: 1

    Uh. Don't feed the trolls. This guy is one of the more obvious ones.

    --
    which is totally what she said
  38. Re:can it run crisis 2 at full speed with at least by Anonymous Coward · · Score: 0

    Except it will display all possible frames, every frame.

  39. In Soviet Russia by Roachie · · Score: 1

    We struggle to keep quantum computer IN lab!

    --
    This sig is not paradoxical or ironic.
  40. Oh! Oh! I know.... by Genda · · Score: 1

    You can't build a quantum computer here because we're a simulation already running in another quantum computer and there isn't enough resolution in the simulation's space time manifold to support the necessary function of another quantum computer. Duh!

    1. Re:Oh! Oh! I know.... by jameskojiro · · Score: 1

      Just like how I cannot run a copy of windows on my windows computer....

      Oh wait...

      VirtualBox

      Maybe we can run quantum computers but they will run very crappily and have the potential to crash the universe.....

      --
      Tsukasa: All I really want, is to be left alone...
  41. Chalk!!! by guitardood · · Score: 1

    All theoretical physicists should be hung by the chalk covered thumbs. Shouldn't we maybe......oh I don't know......INVENT SOMETHING!!!!!!!! What happened to all the scientists that actually experimented with real world problems and solutions that are within our grasp rather than take a hit of acid and calculate PI to a million digits. Especially seeing as how most of the field is based on the great moron's (einstein) postulate that NOTHING can travel faster than light. IT WAS A THEORY!!!!! STOP INVENTING FACTS BASED ON INVENTED FACTS AND INVENT A FREAKING TOASTER THAT DOESN'T BURN MY MUFFINS!!!! AND BTW, STOP TEACHING YOUR BULLSHIT THEORIES AS IF THEY WERE PROVEN FACTS. IT STIFLES FREE THINKING AND INNOVATION. Sorry for that but these chalkboard surfing morons have spent the last 50-75 years speculating on the speculation of the speculation of the speculation of.... I understand that you have to start somewhere but there comes a time when you have to start proving or disproving your theories and move on to the next, you can watch your Star Trek reruns tomorrow. The planet is running out of juice, literally, and we need real scientists to solve very real problems. A bunch of bouncing balls on a canvas is not a parallel universe IT"S A BUNCH OF BALLS ON A CANVAS YOU MORONS! I know this was about Quantum computing, but somebody mentioned physicists and they just piss me off

    --
    -- L8R, guitardood
    1. Re:Chalk!!! by Anonymous Coward · · Score: 0

      switch to decaf, cheers, yet I agree, and digress ...

    2. Re:Chalk!!! by jameskojiro · · Score: 1

      The Oak Ridge Boys (not the band) invented a power source of the future for the whole world inthe late 60's / early 70's but the DOE had a vested interest in making bombs instead and since this new tech would eat bomb parts as fuel they were dismissed and ignored because they were so "heavily vested in current tech" which was ironically invented by the same guy who came up with the new tech.....

      Such is the ways of foolish government agencies and the companies that lobby them.

      --
      Tsukasa: All I really want, is to be left alone...
  42. Re:The Official Slashdot GNU/Linux Distro by guitardood · · Score: 1

    I thought this was about quantum computing not quantum thinking.

    --
    -- L8R, guitardood
  43. neutrinos by StripedCow · · Score: 1

    I, for one, am putting my bets on neutrino computing.

    Using neutrinos faster than the speed of light, it will be possible to send messages back in time, thereby enabling any kind of brute force algorithm. Just do a brute force search, and instantly receive a message from the future containing the answer to your problem.

    --
    If Pandora's box is destined to be opened, *I* want to be the one to open it.
    1. Re:neutrinos by jameskojiro · · Score: 1

      This will break even passwords that only allow one try as you send a msg back in time that AAAAAAAAA didn't work , try somethign else. You will always get the correct answer back.

      --
      Tsukasa: All I really want, is to be left alone...
  44. Change Focus by Anonymous Coward · · Score: 0

    It seems a stretch to build a general purpose quantum computer, at least for a number of years. If would make more sense to me to change focus and attempt to build purpose built circuits to solve a single algorithms. This seems like it simplifies the problem and would in the long run contribute to both the science of general quantum computing and the adoption and thus reinvestment in quantum design. ~Ben

  45. Not like classical physics by Anonymous Coward · · Score: 0

    Making quantum computers work is not just a matter scaling like it was with traditional computers. We know that all quantum effects such as entanglement disappear when we move from the microscopic to the macroscopic. We don't know exactly how it works but just hide it behind words like "collapse of the wavefunction".

    If we are unlucky, there might be some yet undiscovered principle which effectively forbids any quantum effects large systems. I hope not though.

  46. Misconception in summary by Anonymous Coward · · Score: 0

    It is not and never has been a goal of quantum computing to create smaller computers. I am not aware of anyone even working on that idea, and I can't think of any application for such a device. Lets not forget that the first useful computers took up a city block and were not a consumer product.

  47. QPU, quantum processing unit by Anonymous Coward · · Score: 0

    Why wait for quantum computing to be able to replace the CPU? We have GPU's for graphics, DSPU's for signal processing, PPU's for physics processing, etc. Even if quantum computing stays restricted to a limited set of problems, then it might be a useful adjunct to the current deterministic digital computers. Analog computers remained in use for certain problems decades after the digital computer became available.

  48. Announcement will be delayed by many years. by Yoik · · Score: 1

    Because of the impact of Q.C. on crypto systems, I think it unlikely that the announcement will rapidly follow a real practical breakthrough development. Unless there is a very strong willed stinker on the development team, who can resist the bribes and threats, the policy is going to be to keep it under wraps as long as possible. The news will throw the financial community into a panic as no electronic encryption or signature systems will be considered reliable. There is too much money at risk for a product announcement to come out within years of the development.

    Not to mention that the spies of the world would all love to be the only ones with the technology. Let the bad guys on the other side think that their kilo-bit keys are secure so they keep using them. Enigma was the biggest secret of WW2, and mad a real difference to winning the war. Had the Germans known their codes were insecure we might be karate chopping birds for salutes today.

    With the threats and bribes available, it is a secret that can be kept a long time.

    BTW, if there is a reason it isn't feasible, that would be almost as big a secret. Just slightly different motives.

  49. This article is an advertisement for D-Wave by Anonymous Coward · · Score: 0

    D-Wave doesn't have qubits, they have artificial spins. Their system is not a universal quantum computer (UQC) in the sense that it cannot implement an arbitrary unitary transformation to any given initial state. It does use quantum mechanics to solve some problems faster than a classical computer would, but it's not the real thing yet. So it is profitable for them to spread doubts on the feasibility of quantum computation, they could end up selling more than just a single machine...

    And indeed, until the error threshold for arbitrarily long quantum computation is achieved in real qubits, nobody really knows whether a UQC can really be built or not. However the error rates for solid state implementations are getting smaller every month now and we may actually see a small working UQC in the very near future... and that could be bad news for D-Wave.

  50. ENIAC was useful. by Anonymous Coward · · Score: 0

    It served a practical purpose, despite arguably never making it out of the lab. In fact, a lot of "practical" things never do make it out of the lab. Just because people aren't likely to use, e.g., PCR outside of molecular biology labs doesn't mean it isn't useful, usable, and important.

  51. Just look at the numbers! by hweimer · · Score: 2

    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.

    --
    OS Reviews: Free and Open Source Software
  52. As a former QC researcher: by drolli · · Score: 3, Informative

    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.

  53. An interesting question! by madhi19 · · Score: 1

    "Will Quantum Computing Make It Out of the Lab?" Is an interesting but isn't asking it result in changing the outcome?

  54. Questions to the experts by Anonymous Coward · · Score: 0

    It is said that a qubit is a superposition of 2 states (E.g. spin or polarisation). Reading the value
    of a qubit returns either 1 or 0 with a given probability.
    - How do you *practically* (physically) encode a given superposition ?
    - How do you practically read a superposition knowing that a read operation changes
        definitively the state of the qubit.
        In order to determine the probability of reading 1 or 0, one has to perform a succession
        of read operations. How it is done if the state of the qubit is fixed after the first operation ?

    1. Re:Questions to the experts by FrangoAssado · · Score: 1

      I'll try to answer this, even though it's a little late, and I don't know if you'll ever read this. Be warned that I'm not a physicist -- but I've studied quite a bit of quantum computing, and I asked the same kinds of questions you're asking.

      The thing is, a superposition of 2 states (or actually any finite number of states) is not really that interesting or weird, unless you're also talking about entanglement. Unfortunately, quantum computers really need entanglement to work. [Note that when you're talking about position, momentum, energy or time (and many other things), the number of states is infinite, so things become even weirder.]

      The way to measure an electron spin (I'll stick to this example) is to apply around the electron a strong magnetic field in the "up" direction (whatever you decide that to be) and wait a little. The amount of time you have to wait depends on the strength of the field you applied -- the stronger the field, the less time you have to wait. If the spin of the electron is already "up", nothing will happen. If the spin of the electron is "down", the electron will emit a photon and its spin will change to "up". This means that if you detect a photon after you applied the magnetic field, you "measured" the spin to be "down", and if there was no photon, you "measured" it to be "up". After the measurement, the original spin is ruined: it's always up, because the magnetic field forces it to become that way.

      A superposition of "50%up and 50%down" with no entanglement with anything else can be encoded as an electron with spin pointing to the "left" (or any direction perpendicular to the up/down axis, really). To read it, you would apply the same strong magnetic field pointing up and wait for the photon. You get the same thing as the non-superposition states: a photon means you measured "down", no photon means "up". You can only know the probability (in this case "up" and "down" are both 50%) if you repeat the whole thing from the start (i.e., make the spin point left, and then apply the field and wait for the photon) many times. You can change the amounts in the superposition by varying the angle between the spin and the "up" direction. That is: if the spin is almost, but not quite, in the "up" direction, you would get, say, "95%up and 5%down", and so on.

      The problem is: if someone hands you an electron and doesn't tell you which direction its spin is pointing, there's really nothing better you can do to find the direction of the spin than what I described: the best you can get is an "up"/"down" answer relative to a direction of your choosing. Now, the important thing is: when you're talking about an electron that is not entangled, the spin is always pointing in a determinate direction, even though you might not know what it is. That means that there's always a measurement you could make (if you knew which direction to measure) that would give a deterministic answer. That is, if you apply the magnetic field in the direction the electron spin is already pointing, you will always read "up", i.e., no photon.

      Things start to become weird when you allow the spins of two (or more) electrons to interact (and become entangled). If you put two electrons close to each other and far from anything else (and free from any magnetic field), after a while their spins will become "maximally entangled", which is a weird state in which the nice property I described above (having a determinate spin direction) is no longer true. That is, there's no direction that you could make a measurement that would give a deterministic answer. For any direction, you'd have 50% of probability of reading up and 50% of down. That remains true even if you separate the electrons, until you (or something else) measures the spin and forces it to be determinate again. You have to note that to measure a spin, any magnetic field is sufficient (although a very weak field would take a relatively long time to measure it), so it's very hard to maintain this entangled state. What i

  55. how will they... by crutchy · · Score: 1

    ...steampunk a quantum pyewta?

  56. RE: quantum thinking by Geotopia · · Score: 1

    Does anyone remember the Quantum hard drive company? What was in them hard drives?

  57. It scales badly by azgard · · Score: 1

    I don't believe it will. Quantum bits just don't scale as well as normal bits, because they must be entangled. That's the problem.

    If I have a working n (normal) bits, it's quite easy to make 2*n bits (just produce the same thing twice and add some circuitry). But with quantum bits, if you have n qubits working, even n+1 qubits is an engineering challenge and 2*n qubits is a major research effort.

    And because it scales so badly, it won't become practical. So, your quantum computer broke the crypto on 300 bits? No problem - we just double the number on conventional computer (which is easy) and you're screwed.