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Fredkin Gate Breakthrough Brings Quantum Computing Within Closer Reach ( 52

An anonymous reader quotes a report from PCWorld: Quantum computers are based on atomic-scale quantum bits, or qubits, that can represent both 0 and 1 simultaneously. Realizing that potential, however, depends on the ability to build working quantum circuits. The quantum version of the classic Fredkin gate exchanges two qubits depending on the value of the third. It could be a key component of quantum circuitry, but because of the complexity involved, no one has ever managed to build one in the real world -- until now. Whereas the Fredkin gate typically requires a circuit of five logic operations, researchers from Griffith University and the University of Queensland used the quantum entanglement of particles of light to implement the controlled-SWAP operation directly. Essentially, the scientists demonstrated how to build large quantum circuits directly, without having to use numerous small logic gates. That, in turn, puts real quantum computers within closer reach.
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Fredkin Gate Breakthrough Brings Quantum Computing Within Closer Reach

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  • by Tablizer ( 95088 ) on Monday March 28, 2016 @08:42PM (#51796617) Journal

    I give up, quantum stuff makes sorcery sound logical in comparison.

    Too bad Einstein's not still around; maybe he could find a more down-to-earth or simpler explanation. He seemed to be the only prominent one questioning that something seems really out of whack, as if we are missing a yuuuuuge piece of the puzzle.

    He solved the ether weirditity by plugging in relativity. Similarly, maybe the probability and multi/ghostiverses games will fade away when the equivalent of relativity is applied to quantum stuff.

    Maybe particles are like sperm in that when one photon is apparently emitted, there's really many particles emitted, and the first one to hit (react) shuts off the other particles so that they are invisible, almost like neutrinos, so that we don't detect them.

    Thus, the interference pattern really *is* a wave; it only looks like a lone particle upon detection because the others cloak. Well, I'm rambling, but you get the idea: there's a BIG IDEA out there to be discovered...

    • by Anonymous Coward

      The way I think about it now is that quantum computation is essentially multi-level logic, where we can actually do useful computations while staying in the multi-level domain.
      The exact physics of the situation are irrelevant (unless you are a physicist trying to increase the number of qubits).

    • by Anonymous Coward

      The problem is that QM is straight forward if you have high school calculus plus some math, mostly notation, that would fit within a small appendix. Things like the particle wave duality aren't that mysterious or a problem at all if you can work out actual QM instead of trying to contemplate a bad analogy. A large amount of the mysticism and confusion is not there in what is a sophomore level class. Most of the problems people think make QM confusing comes from trying to make math-free analogies connecting

      • by Tablizer ( 95088 )

        But that's possibly like saying, "epicycles are straight forward to model if you remember your math". (Circular regression?) While possibly true, epicycles were the "wrong model" to begin with for orbital mechanics.

        One can model just about any fake or spooky thing that follows patterns with math/algorithms, but that doesn't mean the model reflects the underlying mechanism well.

        • by Anonymous Coward

          No, it's actually the opposite. Epicycles are a complex mathematical model for a phenomenon that has a straightforward math-free analogy. The simple math-free explanation is "planets go around the sun, including Earth", or for "planets go around the Earth" for the epicycles explanation. The actual math of a two-body gravitational system in vacuum where one body is much heavier than the other is not that difficult, but it's more complicated than "planets go around the sun".

          But people often say things like

          • by Anonymous Coward

            That said, most high schools do not teach solving partial differential equations in their Calculus class. Schrodinger's equation is pretty critical. But you don't need to be an expert on PDEs to be able to pick up enough to verify and understand statements made be others; you'd just have trouble independently getting those insights.

            As is, many intro physics classes get by only covering some derivations, and spending more time on results (and often the QM ones just use hand waving arguments to get a rough form of the PDE solution that the students can confirm instead of spending a lot of time on PDEs more complicated than a particle in a well).

            You probably don't even need calculus at all to get the formal gist of many things. Simply learning the concepts behind bra-ket notation, and glossing over the use of calculus to calculate actua

            • by dbIII ( 701233 )

              You probably don't even need calculus at all to get the formal gist of many things

              Only by learning via rote and parroting a list of rules. You need calculus to even work out what is going on with displacement, velocity and acceleration. Extremely easy calculus that makes more sense than looking at things any other way, but it's still calculus.

              To start with it's a lot easier than the physics it's used to explain. What is so hard to understand about the area under a curve of a graph?

      • by Viol8 ( 599362 )

        "The problem is that QM is straight forward if you have high school calculus plus some math,"

        You've obviously never heard Feynmans quote: "If you think you understand QM then you don't"

        In fact no one understands the why, just the what. Giving the probabilities of what might happen in a QM system is one thing, asking WHY it happens in the first place or what a surposition really is, are still questions we're not even close to answering.

      • Actually the heart of it seems to be very simple from a logical perspective. Our most complete and proven models are arithmetic and algebra, so many people use it to prove models but fail to realize arithmetic itself may well be the model. Arithmetic boils down to:

        Where A is a number ranging from negative infinity to positive infinity which much include 1 and 0 regardless of base. Op represents an infinite number of potential logical operations and yet the results have a potential range that is identical to
  • Quantum computing will always be 20 years away. Getting anything practical work done on quantum computers is not likely going to happen in our lifetimes (unless you redefine 'practical work', of course).

  • Quantum computing can be described as a method, a technique, which allows for the computer for a given task to take a peak into the future and to read the answer from the future back to the present.

    In my opinion, any real breakthrough or substantial achievements could and should be classified, because this matter is clearly a subject of the national security.

    There is a lot to learn from the history. Did you know how Soviet military managed to spy and steal US nuclear secrets during WW2? Soviet military inte

    • by JoshuaZ ( 1134087 ) on Monday March 28, 2016 @09:19PM (#51796803) Homepage

      Quantum computing can be described as a method, a technique, which allows for the computer for a given task to take a peak into the future and to read the answer from the future back to the present.

      This is completely wrong. There are in fact computational models that have been worked out about what a computer that could peak into the future would be like and they are insanely more powerful than quantum computers. See []. Quantum computing has nothing remotely like what you've said. I suggest for an actual primer on the topic reading Scott Aaronson's excellent book "Quantum Computing Since Democritus" which doesn't require anything beyond a little basic linear algebra. And in the meantime, if you don't know much about a topic, maybe don't make extreme policy suggestions?

      • by alvinrod ( 889928 ) on Monday March 28, 2016 @10:17PM (#51797127)
        Alternatively, this video [] does a reasonable job at outlining how a quantum computer works. It doesn't go into too much detail, but it's probably enough to give the average person an idea of the differences between quantum and classical computers.
      • If you can't use the word "peek" properly you shouldn't be commenting on computer related issues at all.
        • I think there is a reason why I gave you a red dot.

          I did not even notice that he mistyped peek with peak.

          But thank you that your intellect is so smart that you see typing errors but so dim that you don't grasp the meaning of what he said.

          I for my part usually don't see typing errors ... and I'm happy that my browser underlines wrong spelled words red or redly or read ... hm, seems the underlining failed ... what did I want to say?

          • by Guignol ( 159087 )
            I know what you mean, but
            This wasn't just any "your everyday typo"
            I mean, peek and poke... you know ?
            I would also have a hard time being convinced by anyone unfamiliar with how to write peek to have much of a deep insight about computers... and quantum computing at that
            I think you were replying to a sort of joking/not so joking reply
            But I could be wrong and this could just be our regular grammar nazi :) you probably red-doted him for some reason before after all...
            • Well, my personal typing error I was working on the last 2 years is 'where' and 'were'.
              And yes, my brain knows the difference since I started to learn english which was 40 years ago.
              My fingers don't, my eyes don't. So now some fucking thing, no idea where it actually came from and how to apply it to other typing errors always makes me stop typing after a 'were' or 'where'.
              Usually I type 'where', where a 'were' is appropriated. And remove the 'h'.

              That is why it makes me upset if people try to proclaim other

          • It isn't a typing error. The words "peek" and "poke" are fundamental to computing. If you repeatedly use "peak" instead of "peek" then you don't have any sort of basic knowledge of computing. In addition, his description is nonsensical.
            • The words "peek" and "poke" are fundamental to basic programming from three decades ago. What modern languages use those terms?

            • ofc it is an typing error, how dumb are you?
              Even native english speakers make typing errors of that kind.
              I make hundreds of them every day in my own native language, because my fingers seem just to hear what my brain is thinking loud.
              No idea what the psychological reason behind errors like that is.

              I'm hundred percent sure if you ask the author of the post that makes you so upset:
              a) define the meaning of peak
              b) define the meaning of peek
              He perfectly defines it.

              Bottom line you are one of the idiots if he woul

    • by Anonymous Coward

      Sadly no.

      Quantum Physics is not science, more religion. Experiments to prove quantum entanglement prove it does not happen (e.g. the latest Delft experiment), and so Delft filtered the experiments for times of 'successful entanglement'. In other words filtering for the effect you're trying to prove then using those experiments as proof of the effect.

      A photon of light never did change it's nature depending on the detector it hit. That change of nature never did propagate backwards in time and then forwards a

      • by Anonymous Coward

        I'll admit I don't know anything about this Delft experiment, other than confirming that's a real thing that says the exact opposite of what you're saying. Your criticism sounds like something that could be true, but I'm doubtful on the basis that everything else you said is a non-sequitur. I particularly like this one:

        they don't always get the correct result, (i.e. not in all states simultaneously, no quantum effect).


        • by Anonymous Coward

          DWave is an optimizer. It runs an annealing algorithm. An optimizer tries to solve a user function to find the best solution. e.g. what value of (x1,x2,x3,x4,x5...) would return the minimum of my function F(x1,x2,x3,x4,x5...).

          In DWave the function is a magnetic circuit, defined by connections. You define the connections, the magnetic field collapses, and settles on a minimum result for F. You then measure x1,x2,x3.... to see what inputs gave that result.

          A classic Feyman theoretical quantum computer has phot

        • by Anonymous Coward

          The AC you replied to is a re-occurring Slashdot crackpot or troll(s). They copy-paste the same thing over and over again, sometimes changing a lot or a little, while completely disregarding posts that point how how fundamentally wrong their armchair theories are. It is great that someone wants to think about things and ask questions, but when they show zero interest in answers, or experiments that directly contradict their theories (including basic ones that conflict with his starlings idea of photons, s

      • Pretty much everything you've said is wrong. Yes, the Delft experiment used filtering. No, the filtering doesn't do what you think it does. But more to the point, there have been many experiments prior to the Delft experiment that didn't use that sort of filtering and still got results consistent with entanglement. See e.g. [] for an example.
    • At the same time there is a consensus that Superluminal communication (faster-than-light) is considered impossible.

      It has been proven (within our understanding of physics) that being able to send messages faster than light allows you, between certain weird reference frames, to send a message back in time, breaking causality. But I'm not sure how fundamental causality is to our physics models, or if our models actually allow for exceptions.

      Sort of similar to the crap about time paradoxes and killing your own father. There is no paradox, and killing your father won't make you slowly fade out like in the movies. Caus

      • My take on time travel is that it is impossible. Here is my reasoning: the universe is constantly evolving, be it's wave function or thermodynamically. To move backwards in time, you have to reverse the state of the universe to that of your choosing. To do that, you have to do work. Think about the amount of energy necessary to move all particles of the universe 1 second to the past. Besides, you don't know the state of the universe, not because you don't have enough information, but on principle it is impo

  • by PopeRatzo ( 965947 ) on Monday March 28, 2016 @10:29PM (#51797223) Journal

    Well, it is and it's not.

  • Schrödinger's Quark

In every non-trivial program there is at least one bug.