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Another Step In Quantum Computing: A Functional Interconnect 43

Posted by timothy from the race-to-the-bottom-continues dept.
New submitter Gennerik writes: According to a recent article in the MIT Technology Review, a team of international physicists have been able to create a quantum computing interconnect. The interconnect, which is used to connect separate silicon photonic chips, has the important feature of preserving entanglement. This marks a vital step in creating quantum computers that don't have to work in isolation. According to the article, the trick that The trick that [University of Bristol Researcher Mark Thomson] and pals have perfected is to convert the path-entanglement into a different kind of entanglement, in this case involving polarization. They do this by allowing the path-entangled photons to interfere with newly created photons in a way that causes them to become polarized. This also entangles the newly created photons, which pass into the optical fiber and travel to the second silicon photonic chip.
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Another Step In Quantum Computing: A Functional Interconnect More

Another Step In Quantum Computing: A Functional Interconnect

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  • The summary (Score:5, Funny)

    by Maritz ( 1829006 ) on Thursday August 20, 2015 @01:39PM (#50355761)
    Summary would have read better if the submitter had read over it. ;)

  • Comment removed (Score:5, Funny)

    by account_deleted ( 4530225 ) on Thursday August 20, 2015 @01:53PM (#50355951)
    Comment removed based on user account deletion

    • PS, if quantum photon tangler re-danglers are activated, let me know which light on the server indicates this and how i can check to make sure the tangler is launching fresh photons.

      Well, we have designed it so that the photons will automatically light up. I am particularly proud of that design.
      Unfortunately, we have not exposed them outside the box so you will not be able to see them from the outside.
      However, we are working on software that will represent their state in a meaningful fashion.

  • Big news also in boson sampling (Score:4, Interesting)

    by JoshuaZ ( 1134087 ) on Thursday August 20, 2015 @02:01PM (#50356055) Homepage
    In related news on quantum computing 6-photon boson sampling has also been performed (incidentally also by researchers at Bristol with some overap between the two groups). See http://www.scottaaronson.com/blog/?p=2435 [scottaaronson.com] for details and discussion. Boson sampling is an important idea which involves estimating the probability distribution of non-intersecting photons. Crucially, boson sampling may be substantially easier to construct since they don't require nearly as much in the way of complicated machinery and error correction as full-power quantum computers, but there are also strong reasons to believe that boson sampling cannot be done efficiently on a conventional computer. That paper is http://arxiv.org/abs/1505.01182 [arxiv.org] (which also has some other very cool results - they've made essentially reconfigurable chips for this rather than having to make new ones for any specific photon sampling procedure). The original paper which proposed boson sampling is http://www.scottaaronson.com/papers/optics.pdf [scottaaronson.com].

  • now that we have entanglement working, can we skip the quantum computing and go straight to the ansible?

    • Unfortunately, it doesn't work that way. There's no known way to get faster than light communication using entanglement and if we're correct in our understanding of physics then it is entirely impossible. One can take two particles that are entangled but if one changes the state of one of them, it doesn't alter the other's state, it simply breaks the entanglement.

      • One can take two particles that are entangled but if one changes the state of one of them, it doesn't alter the other's state, it simply breaks the entanglement.

        this doesn't make sense. I thought the definition of entanglement was that two particles were linked and a change to one caused a change in the other, regardless of the distance between the particles, and this change happened at FTL.

        • Re:ansible (Score:4, Informative)

          by JoshuaZ ( 1134087 ) on Thursday August 20, 2015 @04:09PM (#50357073) Homepage
          No. That's not how entanglement works. A better way of thinking about entanglement is imagining two fair coins that can be any distance apart and the first time you flip them, you are guaranteed that they'll either both be heads or both be tails. This isn't a perfect description, but this is close enough. If one wants to be mathematically rigorous then we'd say that two particles are entangled if we cannot describe their combined state simply as the tensor product of the state of each one https://en.wikipedia.org/wiki/Quantum_entanglement#Quantum_mechanical_framework [wikipedia.org]. If you want to read a good introduction to a lot of these issues, I recommend Scott Aaronson's "Quantum Computing Since Democritus" which is essentially aimed as an introduction to quantum computing for non-experts with a some math background (essentially assumes is ok with basic linear algebra and basic calculus). Scott is an absolutely fantastic writer.

          • we're saying the same thing. what I'm hearing is that each of us have a coin, and when we flip them they land on the same value. but the trick is, you say it only happens the first time you flip them, but I bet it happens every time you flip them, no? but then how will we know to flip them at the same time if we are a good distance apart (light years)?

            • No. You get one such flip. It won't actually matter if you flip them at the same time or not. As long as you keep your coin carefully in a little box (where keeping it carefully in a little box is essentially a metaphor for keeping it in a little box that doesn't let any stray photons in), you can do your flip whenever you want. But let's say we had a billions coins so we could each get a billion flips. We still can't use that to send information faster than the speed of light because we have no way to cont

              • well what do you want me to say? at least I'm trying to solve a problem and make something new and exciting. you're just throwing up your hands and saying something won't work. Is that was science is all about? shutting down prominent avenues of research? what if somebody had shut Einstein down, or Copernicus, or Darwin? where would we be now?

                • Is that was science is all about? shutting down prominent avenues of research?

                  Science is about observing nature and forming theories and laws that agree with those observations. Prominent avenues of research can explore speculative areas and can even challenge previous results. However, the stronger those previous results are, the harder it is to challenge them. I'd be absolutely thrilled if someone came up with a way to achieve faster-than-light signalling. But I'm not expecting it to happen anytime soon, because our current understanding of physics says that it's impossible.

                  what if somebody had shut Einstein down, or Copernicus, or Darwin? where would we be now?

                  Einstei

                • No. I'm attempting to explain that people have thought about this a lot, and we understand why it won't work. I also gave you references on what to read that will explain it in detail. I strongly recommend Scott's book I mentioned earlier. If you do think that your idea has any chance of working, the best thing to do is to try and actually go read a bit on the subject and see if you can make it work. But in general, it is worth keeping in mind that the vast majority of ideas *don't work* and understanding w

                • Here, I'll help you out.

                  He's right; it's never going to happen in a 4 dimensional space-time manifold. Or perhaps more accurately; attempting to use mass (photon, electron, what have you) bound within the confines of said manifold to somehow trick its own existence... you see how one gets out into the weeds there?

                  You have to think bigger. If these dimensions don't allow something, then you'll have to go around them; under, over, bypass somehow.

                  How to get outside this manifold we seem to be bound to? Well, i

            • I don't think it matters that we both flip them at the same time, they have already been flipped but the result is in both states at once. It is more like looking at the result of the flip. Once I look at the result then your coin result is also set and when you look you will see the same result even if it is an hour or day later. To do another case we would need new coins where the result is unknown and they are entangled.

          • No. That's not how entanglement works. A better way of thinking about entanglement is imagining two fair coins that can be any distance apart and the first time you flip them, you are guaranteed that they'll either both be heads or both be tails. This isn't a perfect description, but this is close enough

            Perhaps even better (per the analogy to particle-spins) is to imagine that one coin is guaranteed to be in the opposite state of the other, i.e., if one is heads, the other is tails.

            Another important point is that you cannot control the outcome of the observation: you can't make your coin produce a head or tail, you can only flip it and see what happens. If your coin shows say, a head, then you know immediately that the other is a tail, no matter how far away it is -- but you can't control the outcome, so y

            • No. That's not how entanglement works. A better way of thinking about entanglement is imagining two fair coins that can be any distance apart and the first time you flip them, you are guaranteed that they'll either both be heads or both be tails. This isn't a perfect description, but this is close enough

              Perhaps even better (per the analogy to particle-spins) is to imagine that one coin is guaranteed to be in the opposite state of the other, i.e., if one is heads, the other is tails.

              Another important point is that you cannot control the outcome of the observation: you can't make your coin produce a head or tail, you can only flip it and see what happens. If your coin shows say, a head, then you know immediately that the other is a tail, no matter how far away it is -- but you can't control the outcome, so you can't use the observation to send a faster-than-light signal.

              It's like mashing two TINY potatoes together and setting the remains aside. They are now entangled. When you observe one, you can infer the state of the other if neither had interacted with any potatoes in the meantime because if your potato is missing a hunk, it's probably stuck to the other one. We observe these tiny potatoes by throwing other little vegetables at them and observing the results, thus disentangling them in the process, because now you have broccoli guts all over.

              It's "spooky" because yo

  • If I can share entangled states via an interconnect I can send a member of a pair to another location before I cause the state of it's twin to be resolved. This allows me to build a pair of quantum buffers, which gives you zero lag links and caches etc.

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