back to article Boffin melds quantum processor with quantum RAM

A California physicist has created a quantum-computing chip based on the CPU/RAM combo known as the von Neumann architecture, opening the door, he argues, to commercial quantum-computing development. "I think it's very exciting as a researcher because we're really at the borderline between the two worlds of physics and …


This topic is closed for new posts.
  1. Destroy All Monsters Silver badge

    Why oh why

    Why are people afraid of saying what "superposition" is?

    It's just a vector of length 1, with complex-valued coefficients.

    It lies on the unit sphere of an N-dimensional vector space.

    Each dimension of that vector space represents the state of the system.

    If the vector lies perfectly aligned with one of the axis, the system is in a definite state. Otherwise it is in a superposition.

    For example, the qubit can be in states 0 or 1.

    This gives a 2-dimensional complex vector space, with the state vector on a "circle" (actually a 4-d real sphere)

    A system with 2 qubits can be in states 00 01 10 or 11.

    This gives a 4-dimensional complex vector space, with the state vector on a 4-D complex sphere.


    The quantum computer rotates that vector according to some linear differential equation.

    For "observation", in the simplest case, you take the coordinates of the vector along each of the principal axes for 00, 01, 10, 11 (this is a complex number). Take the length of the complex number, square it. This is the classical probability of "observing" the system to be in respective classical state 00, 01, 10, 11.

    Given that you want to solve a problem, you will set things up so that one of the axes is solution that you seek (evidently, it corresponds to a bitpattern). So you want your quantum computer to follow the linear differential equation that gives you the correct bitpattern with reasonable good probability upon "observation".

    And this is actually an extension of classical probability theory, it's just that nature apparently likes complex numbers: working with real-valued probabilities and state vectors moving on planes in an N-dimensional real state space is tired.

    Now, what kind of algorithms can be build with this extended probability calculus?

    Fast factorization. Simulation of quantum systems. Fast lookup in databases. Any other.. ?

    How to solve the "find the differential equation for my problem"? How to map the differential equation to the architecture described in the article? There is work to do!!

    1. TonyG

      Thank you.

      I think that you've eloquently explained why people are afraid of saying what superposition is.

    2. Anonymous Coward
      Anonymous Coward

      Maybe because

      when you start talking about vectors, complex-valued coefficients, N-dimensional vector space and whatever else you went on to talk about before I stopped reading, most people would tend to stop reading.

    3. Lunatik


      At last! Someone able to explain quantum theory in a measured, easy to understand manner! Anyone not comprehending it after reading this is surely a moron?

      More power to your superpositioned elbow.

    4. hplasm
      Thumb Up


      Supercool, friend!

    5. John Brown (no body) Silver badge

      Re: Why oh why

      Yeah, but how do you *know* if the bit is 0 or 1?

      If you look, does it change into a cat?

    6. Anonymous Coward
      Anonymous Coward

      To summarize your deliberately confusing post...

      Think of it as a sphere, with an arrow coming from the centre to the edge.

      but when you look at it from the side, as a circle, the arrow looks like it has a mixture of horizontal, and vertical components..

      but if the sphere's arrow is aligned with your sideways view, then the arrow is in a single definite state (say fully horizontal or fully vertical), and not a mix of the two.

      (just replace 'sphere' with some N dimensional word, and 'circle' with some N-1 dimensional word).

    7. MrT

      This explains why...

      ...eventually MrsT will eventually achieve her aim of owning all the shoes in the shop (the vector in 4D). And have the reasons why each is needed (the rotation, or "spin") ;-)

    8. Anonymous Coward
      Anonymous Coward

      Thanks for clearing that up

      Your cheque is superimposed in the post...

      Please wait while we collapse the wave function and find out exactly WTF is in your account...

      Transfer denied: you have a 60% probability of having insufficient funds...

      So if we had quantum accounting, then everyone could be rich and/or poor at the same time!

    9. Hungry Sean
      Thumb Up

      not sure what everyone else's beef is

      I thought this was fairly well put and informative-- clearest explanation of quantum jiggery-pokery I've seen so far. . .

      1. Goat Jam
        Paris Hilton

        My cats breath smells like cat food


  2. Anonymous Coward


    ...somebody figures how to use a differential quantum computing device like that to crack encryption, as envisioned in sci-fi, I don't want to be around...

    I hope yes, that quantum computing becomes a reality (and a useful one), but as for cracking encryption, I hope people will hit a snag of complexity / power / thermal requirements and just let go and give up.

    Or humanity has evolved to a point when we don't need secrets, or money.

    1. Tomato42

      Quantum and crypto

      While quantum computers help tremendously with brute-forcing encryption, they don't magically solve it. You still have to post-process the results given to you by a quantum computer on a regular computer.

      What this really means, is that the magnitude of possible solutions is halved. To crack a AES-128 encrypted file you don't have to perform 2^128 "operations", only 2^64 will do.

      2^64 is brute-forceable on todays computers, 2^128 won't ever be crackable on regular computers (using brute-force, it may be using flaws in algorithm). That's why your AES-256, RSA 16kbit and EC 521bit keys are safe.

      1. This post has been deleted by its author

    2. TonyG

      Just need to change encryption techniques

      There's a couple of techniques (for example McEliece) which (in theory) allow for cryptography even with quantum computers.

    3. amanfromMars 1 Silver badge

      C42 Quantum Control Systems

      "Or humanity has evolved to a point when we don't need secrets, or money." .... Anonymous Coward Posted Friday 2nd September 2011 20:58 GMT

      Evolved/Morphed into what exactly, AC ..... a Sublime Alien Program delivering Private Orgies of Organised ARG CHAOS to Brave New Pirate World Order Systems [The 0 Qubit component] ..... or Pirate Orgies of Organised ARG CHAOS to Brave New Private World Order Systems [The 1 Qubit Component ...... with all manner of entangling superpositions/random quantum pairings in the Dynamic Output of its NEUKlearer HyperRadioProActive IT ...... ITs Ternary Dividend.

      With Virtual Reality delivery assured and guaranteed with Organised Networking of Alternate Reality Games Clouds Hosting Advanced Operating Systems, are Future Programs for Humanity a Quantum Entanglement Exercise and AIReal SMART Enterprise with Unlimited Immaculate Potential for there are no bounds nor restraints, other than those which one would impose upon and require of oneself, on Imaginanation and Crazy Real World Plays and Global Prime Program Product Placements.

      Simply Complex Instructions Sets made easy to Follow with Leading Media Presenting Beta Trails/Show Trials of Novel ProgramMING Protocols with QuITe Alien Tautologies/AIMethodologies.

      Species may evolve in a progressive but relatively slow linear fashion. They may also at time "explode" and may make a seemingly spontaneous and instantaneous quantum leap into other areas of existence which would await their coming arrival with an empty canvas of a world in which they are fully expected to populate with fab creations.

      In Life in LOVE and in Live Operational Virtual Environments, there are no Rock Solid Answers, only Fluid Dynamic Solutions that are Intelligently Designed to Evaporate in Time for Progress to Deliver another Leading Question for the Past to Follow and Store to Virtual Memory Supply ....... Raw Core Source ...... which in this particular and peculiar case would be CodedDXSSXXXX

      And such explosive evolutions can be extremely revolutionary and most disruptive, although that is a choice which can be easily tailored to be unbelievably constructive and instructive, instead. Needs must will dictate that subjective path .... for all such major objective decisions have allied security considerations which are always flexible/liquid/Fluid Dynamic.

      And the tipping point for humanity to evolve and/or quantum leap with regard to "Or humanity has evolved to a point when we don't need secrets, or money." can be reached with just a nucleus few of enlightened souls to infect and effect all with what is discovered and available for delivery. Thus in the mass of humanity excused the burden of having to develop its own intelligence from primitive to prime in order to benefit from better programming and Beta ProgramMING ..... AI at ITs Work in REST for Play and ForePlay.

      1. Yesnomaybe


        quantum computing enable us to make sense of what amanfrommars 1 is trying to comunicate to us?

    4. Ru

      Quantum cracking not all it is cracked up to be

      Whilst Shor's algorithm and the like rather put paid to discrete logarithm and elliptic curve based public key encryption, there are all sorts of designs for new key distribution mechanisms that are not amenable to quantum cracking. With any luck they'll actually be ready by the time anyone actually implements a quantum computer.

      Grover's algorithm that allows a brute force search in O(sqrt(N)) time instead of O(N) is a significant speedup, but not to the same degree. A symmetric key cipher of suitable key length will still be impractical to brute force.

      djb has written a bit about this at, if you were feeling bored.

  3. Anonymous Coward

    still not convinced

    Are we sure this just isn't some fundamental funding bollox, dreamed up over Latte and Donuts. Is there a single Dell/HP/IBM piece of tin, powered by this vapourware, somewhere something tangible that can actually do something other than generate funding for another year. Until then, with supersymmetry cast to the four winds, isn't superposition along with the rest of quantum theory, just as vulnerable? I will rest my case and await real science in less bolloxial form to come forth and be proved.

    1. Ru

      So you don't actually know what quantum computing is?

      Hint: if you mention 'supersymmetry' then you clearly have no idea about particle physics either.

  4. hplasm

    I,for one, welcome

    our new overlord, Shalmaneser!

    1. Solly

      Tracking with close ups

      Christ what an imagination I've got...

  5. Nick Galloway
    Thumb Up

    Build one

    And then work out cold fusion. THen we could run the computer cheaply and get some mad frame rates from some seriously realistic games.

    The computers improve, the users do not. Quantum processing websurfing and solitaire!

    I still want these guys to build it to the point where we can all use them.

    Good luck

    1. Magnus_Pym

      Yes. But what happens...

      ...when the game become MORE realistic than reality. Does reality flip over into the game state.

      In quantum gaming Duke Nukem plays YOU.

  6. eBusiness

    1 billion states please

    It all sounds exciting, but after getting a few more facts from the press release I'm able to stay in my chair.

    "The quantum integrated circuit includes two quantum bits (qubits), a quantum communication bus, two bits of quantum memory, and a resetting register comprising a simple quantum computer."

    So this isn't really a computer, it has got a whooping 2 bits of memory, meaning that it can actually only hold 4 different states. The mathematicians working with quantum computers gladly assume that they can get an indefinite number of different states. The actual experiments seem to stick to single digit numbers. If quantum computing is to have a future someone needs to show that they can hold a large number of concurrent states in a quantum system.

    But +1 for building a steampunk prop and claiming that it is a computer. That image really deserves to be shown in a higher resolution:

  7. Anonymous Coward


    What eejit thought that one up? Was QPU (oh look, Quantum Processing Unit!) too *&)%&@ easy?

    1. Havin_it

      Oh aye?

      And what are you planning to call the quantum GPUs, FPUs, MMUs et al, smartarse?

      Anyway, QPU is already in usage. It's a university for dolls (obscure enough?)

  8. Michael 31

    Quantum Computing will not work (IMHO)

    As the article and the first poster eloquently expounded, a successful quantum computation depends on the exact degree of coupling between qubits. 30% or 31% makes a difference! So quantum computers are really analogue computers and this is the reason they will not work. They will be the most sensitive general purpose detectors of 'anything' ever built - and for that reason I think the work is interesting. But IMHO they will never complete any non-trivial calculation.

    This opinion has been correct for the last 20 years. I would be delighted to be obliged to change my opinion but I don't see anything happening to make me change it.

    And yes I know there quantum error checking circuits available - but they VASTLY enhance the complexity of the circuitry required.


    1. Anonymous Coward

      thought so

      Thank you Michael. IANAP (I am not a physicist) but the explanation did look awfully like an analogue computer to me too, but then, I could be wrong.

    2. Mr Young

      Quantum computing!!!

      It will work and not work at the same time

      1. Francis Boyle Silver badge

        As I understand it

        that the problem with quantum computers - you get the right answer(s) along with the all the wrong ones, hence the need for a secondary non-quantum computer to sort it all out.

        No joke.

    3. amanfromMars 1 Silver badge

      A simple mistake to make, Michael 31, and unbelievably costly too.

      "So quantum computers are really analogue computers and this is the reason they will not work." ... Michael 31 Posted Saturday 3rd September 2011 08:29 GMT

      Quantum computers are virtual entities and they have always worked .... since before even Time was In the Beginning.

      IT is the World of Cosmic Magic, Michael 31, and a Fab RapidE Trip for All Inner Circle Networks with their Virtual Covens of Hot Witches and Cool Wizards. Yin Yang Party Head Quarters. Seventh Heaven for Vixen and Foxes .... Masters and Mistresses of Stealth's Great LOVE Game .... in Live Operational Virtual Environments ...... Floated in CyberSpace.

      A Game Changer of a Virtually Traded, Semantic Operation ...... IntelAIgent Community Space Control Mission ...... aka NEUKlearer HyperRadioProActive World Order Program and/or Pogrom.

      Methinks there is more to worry about than just restless natives, should you be into those monitoring of communications games, for struggling to contain a mentor is a life-changing event which removes horizons.

      1. Mr Young
        Thumb Up

        And there was me thinking getting pissed was fun!

        I want some of what you're on

        1. Goat Jam

          Hello Mr Young

          You must be new here.

          Meet amanfrommars.

          amanfrommars hasn't been seen around these parts for a while. Some people theorise that he is some sort of AI bot experiment.

          But it could be, as you say, just the result of some really good drugs.

          1. amanfromMars 1 Silver badge

            Really Good in AI is always a Better Beta

            That's a novel mix, Goat Jam, which some might even conclude has one leading with experiments in the other for results which are heavenly.

  9. Jon Thompson 2

    Shurely Shome Mishtake?

    Von Neumann architecture? Surely Harvard....

  10. Alan Firminger

    Sounds like

    Sound like Shroedinger's cat, and I never believed that.

    1. Magnus_Pym

      I thought...

      ... that Schroedinger made up the cat thing to point how ridiculous the theory was.

  11. illiad


    CPU means Central Processing Unit... it is not based on how it does it... if it was it would be called 'Electron Processing Unit' - all the transistors inside control the flow(or not) of electrons..

  12. illiad

    Michael 31..

    well we will have wait and see, wont we??

    - and do remember that MANY things were once said to be impossible..

    they once said that driving a car at more than 10mph would be damaging to the human body..

    no man should fly, its against nature...

    this new dvd is totally uncrackable... (done in 10 minutes, *while* he was showing it off at some exhibition... :) :) )

    I am sure once the quPC is working, many geeks will break many quPasswords / qSecurity.....

  13. cordwainer 1

    Q or qu?

    I gathered from Mariantoni's statements quCPU was chosen over QPU to differentiate their "qubit CPU", with its unique quantum bus, from other researchers' quantum CPUs or quantum processing units. I could be wrong, and if so am braced for incoming jibes.

    However, it seems worth noting quCPU also lends itself to a larger number of informal or "lay" pronunciations than QPU, a matter of some importance where new technologies are concerned. One needs a quick, pronounceable term In order to talk with colleagues, yes, but more importantly a snappy coinage to catch the public imagination, for press releases and, with luck, for advertising. Any scientist worth his salt realizes choosing a good "wordable" acronym is an essential part of 20th Century research.

    Perhaps the inventors have toyed with qubitproc [properly pronounced kewbitpross, not kewbitprok], qubitcessor [kewbitsesser], or qubitcpunit [kewbitspoonit], subtlely emphasizing their qubit/qbus combo breakthrough.

    The public and press, on the other hand, lean toward whimsy, absurdity and - if even faintly possible - rudeness. It is there quCPU proves the better choice, offering dozens of amusing but fairly harmless variations including [phonetically] "kwackpu", "kew-sproo", "kew-spoo," "kwantalprok" or "kwokprok", as well ones suitable for both print and speech, such as the retrograde variants "centraqube" or "cproquit" [pronounced "sprocket"].

    In comparison, QPU would inevitably end up being pronounced "Q-poo" by the masses, no matter how diligently the inventors pushed for something less squatalogiqal.

    Personally, I'm rooting for biological solutions over quantum, particularly budding research into the IT possibilities of, plastinated....mouse brains.



  14. John Styles

    Whenever I hear of Grover's algorithm

    I cannot but help think of the muppet in Sesame Street and his little known work in complexity theory. Is the cookie in the monster or not? Until the trash-can is opened we cannot determine its state.

  15. Antoine Dubuc



    I represent the Quantum Computers illiterates of this world.

    Could someone explain how the popular notion that a quantum computer can figure out which result set is the right one?

    I mean, to mean this sounds like an oracle.

    You feed it a problem, it spits out a solution.

    I can understand it spits out all the results possible, but knowing which one is the right one?

    That's Spooky.

This topic is closed for new posts.

Other stories you might like