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Team Constructs Silicon 2-qubit Gate, Enabling Construction of Quantum Computers (phys.org)

Posted by Soulskill on from the plug-and-play dept.

monkeyzoo writes: A team at the University of New South Wales (UNSW) in Sydney has made a crucial advance in quantum computing. Their advance, appearing in the journal Nature (abstract), demonstrated a two-qubit logic gate — the central building block of a quantum computer — and, significantly, did it in silicon. This makes the building of a quantum computer much more feasible, since it is based on the same manufacturing technology as today's computer industry. Until now, it had not been possible to make two quantum bits 'talk' to each other — and thereby create a logic gate — using silicon. But the UNSW team — working with Professor Kohei M. Itoh of Japan's Keio University — has done just that for the first time. The result means that all of the physical building blocks for a silicon-based quantum computer have now been successfully constructed, allowing engineers to finally begin the task of designing and building a functioning quantum computer.

56 of 92 comments (clear)

  1. Well there goes the cipherhood by Anonymous Coward · · Score: 2, Funny

    We done got fucked out of good publicly available encryption for decades at least. The beast won. Resistance is futile.

    1. Re:Well there goes the cipherhood by monkeyzoo · · Score: 2, Interesting

      Say goodbye to asymmetric encryption.
      Symmetric like AES can still survive quantum attacks with a doubling of key length. But all the current asymmetric algorithms are in peril once quantum computers exist.

    2. Re:Well there goes the cipherhood by Junta · · Score: 5, Interesting

      Of course the issue being that AES isn't useful in many contexts without key exchange, which is generally rooted in asymmetric algorithms. Pre-shared key circumstances exist, but are exceptionally rare and not particularly feasible in most internet contexts.

      Such a strategy using username/password as foundation of the strategy can work once a relationship is boot strapped, but no good way to bootstrap a new secure relationship.

      --
      XML is like violence. If it doesn't solve the problem, use more.
    3. Re:Well there goes the cipherhood by Bob+the+Super+Hamste · · Score: 5, Interesting

      Well AES, Twofish, serpent, etc. were all designed with quantum computers in mind hence the 256 bit key lengths. To brute force with even with quantum computers it takes more energy than can be reasonably harvested from our sun. What I wonder is if there are other weaknesses in symmetric key crypto that can be exploited with quantum computers that aren't a brute force attack. This is where the interesting results will happen.

      --
      Time to offend someone
    4. Re:Well there goes the cipherhood by eexaa · · Score: 1

      Oh c'mon

      https://github.com/exaexa/code...

    5. Re:Well there goes the cipherhood by slew · · Score: 2

      Say goodbye to asymmetric encryption.
      Symmetric like AES can still survive quantum attacks with a doubling of key length. But all the current asymmetric algorithms are in peril once quantum computers exist.

      Say hello to quantum encryption to replace some uses of asymmetric algorithms (which are often only used to exchange keys for symmetric algorithms).

      The real danger is to public-private key signature algorithms (such as those used to sign certificates). At some point these may need to change to use proof-of-work (e.g., bitcoin) style authentication or other cost prohibitive measures...

    6. Re:Well there goes the cipherhood by Junta · · Score: 2

      The challenge being that the dust is far from settled on the quantum-resistant asymmetric hashes, and none of them have been anywhere near as well researched as RSA or even elliptic curve.

      I can't reasonably today set up a website certificate using any quantum resistant algorithm. More research and consensus are required. It may be pessimistic to say no meaningful encryption for decades (it ignores symmetric encryption, this step actually isn't *practically* any closer to producing the theoretical quantum computer that could derive private keys from public keys, and even if it were closer, algorithms that are credibly being considered quantum resistant are out there, so it may be years, but not decades from now unless something is deeply wrong with *all* the candidates).

      --
      XML is like violence. If it doesn't solve the problem, use more.
    7. Re:Well there goes the cipherhood by r.freeman · · Score: 1

      SSI ECDG signing is immune to QC:
      https://en.wikipedia.org/wiki/...
      +
      https://en.wikipedia.org/wiki/...

      Also, NTru encryption is immune to QC.

    8. Re:Well there goes the cipherhood by TechyImmigrant · · Score: 1

      Say goodbye to asymmetric encryption.
      Symmetric like AES can still survive quantum attacks with a doubling of key length. But all the current asymmetric algorithms are in peril once quantum computers exist.

      The selling point of things like lattice crypto (e.g. NTRU) is that it is quantum attack secure.

      But don't worry. They aren't going to build a working quantum computer that can factor large numbers or solve the DLP over elliptic curves. They can't make things that cold.
       

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    9. Re:Well there goes the cipherhood by dcollins117 · · Score: 1

      Say hello to quantum encryption to replace some uses of asymmetric algorithms (which are often only used to exchange keys for symmetric algorithms).

      Quantum computers will only be available to those that can afford them so at first you'll see yet another huge capability imbalance between the haves and the have nots. If quantum computer does eventually become cheap enough for the average consumer, I'm not sanguine it will occur in my lifetime.

    10. Re:Well there goes the cipherhood by TechyImmigrant · · Score: 3, Interesting

      Say goodbye to asymmetric encryption.
      Symmetric like AES can still survive quantum attacks with a doubling of key length. But all the current asymmetric algorithms are in peril once quantum computers exist.

      Say hello to quantum encryption to replace some uses of asymmetric algorithms (which are often only used to exchange keys for symmetric algorithms).

      The real danger is to public-private key signature algorithms (such as those used to sign certificates). At some point these may need to change to use proof-of-work (e.g., bitcoin) style authentication or other cost prohibitive measures...

      No, there are quantum secure public key algorithms. They are around 2X less efficient on key size than ECC. So it's not a huge problem.

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    11. Re:Well there goes the cipherhood by TechyImmigrant · · Score: 1

      What's an asymmetric hash? Do you mean a signature?

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    12. Re:Well there goes the cipherhood by bob_super · · Score: 1

      In a nutshell, passwords are like house locks, not Fort Knox vaults.
      You deal with the consequences the same way: insurance (also known as offline backups).

    13. Re:Well there goes the cipherhood by MrNaz · · Score: 2

      How does an offline backup protect your research team from having their as-yet unpatented work-in-progress data stolen by a competitor who has cracked their teams' data links?

      --
      I hate printers.
    14. Re:Well there goes the cipherhood by bob_super · · Score: 1

      Since you can't buy locks that will handle patient blow-torching, I guess you have to tell the cops to stop looking for terrorists through the cute neighbor's bathroom window. Or stop having doors in your walls.

    15. Re:Well there goes the cipherhood by MobileTatsu-NJG · · Score: 1

      Quantum encryption? How does that work? "The message changed when I read it!"

      --

      "I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)

    16. Re:Well there goes the cipherhood by delt0r · · Score: 1

      Err just no. First of all there is a lot more to running the factoring method on a quantum computer than getting enough qubits (right now you need more than 1000). You need to keep it coherent for the many many operations that have to be run on it. Also building a QC is exponentially difficult. It is not like "just add a qubit" adding a single qubit to make 3 qubits is on the order of 2x harder than 2 qubits. Going from 100 to 101 qubits is again 2x harder than the 100 qubits. You get the idea.

      So even if they can make a few 100 qubits your still totally safe. Unlike classical computation there is no way to use a 100 qubit QC to solve a problem that needs a 101 qubit register. And right now with decoherence time we are getting, you also need many many many extra qubits for error correcting.

      Finally if there really is some uber breakthrough and +1000 bit QC become reality, there are public key schemes that are not compromised with QC. The keys are fairly big, but on the modern internet this is much less of a problem these days.

      --
      If information wants to be free, why does my internet connection cost so much?
  2. So Quantum Computing is real now? by lgw · · Score: 4, Interesting

    This step forward makes "quantum computing" real to me. Up till now, it's all been so experimental that it was divorced from engineering, and for me the target of much skepticism. Now that it's being done in silicon, however, it's on its way to being a product. Finally we might get past the hype and see what can actually be delivered!

    --
    Socialism: a lie told by totalitarians and believed by fools.
    1. Re:So Quantum Computing is real now? by KGIII · · Score: 2

      I want to know if it can solve the N Problem. *nods* Or, really, if it can be used to play Crisys.

      --
      "So long and thanks for all the fish."
    2. Re:So Quantum Computing is real now? by __aaclcg7560 · · Score: 1

      Finally we might get past the hype and see what can actually be delivered!

      Whether the cat is alive, dead or both?

    3. Re:So Quantum Computing is real now? by Anonymous Coward · · Score: 2, Interesting

      From the article, I understand that they have managed to entangle 2 particles together in a silicon chip. In a true quantum computer, you want to have much more than 2 particles entangled together. Adding many of those 2-particle-entangled chips isn't going to create a bigger quantum computer.

      The hard problem with quantum computers is decoherence. Maintaining 2 particles entangled is easy but maintaining 10 is very hard because the particles naturally tend to "collapse" as soon as they interact with anything in their environment.

      As much as this may be a very interesting progress towards building quantum computers, we have yet to solve the problem of maintaining 10, 20 or perhaps 100 qubits in an entangled state.

    4. Re:So Quantum Computing is real now? by TechyImmigrant · · Score: 1

      Measurement, collapse and entanglement are the same thing : https://www.youtube.com/watch?...

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    5. Re:So Quantum Computing is real now? by Bob+the+Super+Hamste · · Score: 1

      My bet is on a liquefied radioactive mass.

      --
      Time to offend someone
    6. Re:So Quantum Computing is real now? by Anonymous Coward · · Score: 1

      Yes. In a quantum computation, you want to set your qubits in an initial entangled state and let the computation "run". At the end of the computation, you will read the qubits, thus collapsing the state of your qubits (measure or collapse, same thing).

      Now what is very very important is that while the computation is running, the qubits need to stay entangled. If a photon (or anything else for that matter) passes through your qubit gate and collapses the entanglement, you will not read any useful results out of your computation.

      Now if you only have 2 qubits entangled, there's really nothing interesting that you can compute (you can factor numbers up to 3 perhaps). You will need more than 2 entangled qubits to do anything interesting.

  3. 2 bits? by TechyImmigrant · · Score: 1

    So we can try and factor 0,1,2 and 3?

    --
    I should use this sig to advertise my book ISBN-13 : 978-1501515132.
  4. Re:Can't wait to ask it... by ClickOnThis · · Score: 1

    That's a solved problem.

    --
    If it weren't for deadlines, nothing would be late.
  5. Translation ... by DrJimbo · · Score: 4, Interesting

    The real problem with quantum computers is noise and decoherence. To make a practical quantum computer you need three things:

    1) Qubits thare are very loosely coupled with the environment so they have a long decoherence time
    2) A way of coupling these qubits to each other without destroying (1).
    3) A way of reading from and writing to qubits without destroying (1) or (2).

    I *think* this paper claims to have solved (2) and (3). I believe (1) had previously been solved by the use of electron spin with atoms of Silicon-28 which this paper uses as well. Do a search for "qubit silicon 28". I think a saw a measured decoherence time of 200 microseconds. This would mean that a calcuation would need to be completed in well under this time in order to not get swamped out by noise from the environment.

    --
    We don't see the world as it is, we see it as we are.
    -- Anais Nin
    1. Re:Translation ... by Anonymous Coward · · Score: 4, Funny

      So if all these problems are solved why are they wasting their time publishing a paper instead of taking over the world?

    2. Re:Translation ... by HexaByte · · Score: 1

      So... does this mean I learned binary for nothing?

      --
      HexaByte - he's a square and a half!
    3. Re:Translation ... by DrJimbo · · Score: 1

      So... does this mean I learned binary for nothing?

      Sometimes it does mean that and sometimes it doesn't mean that.

      --
      We don't see the world as it is, we see it as we are.
      -- Anais Nin
    4. Re:Translation ... by DrJimbo · · Score: 1

      From the fine article:

      Dzurak noted that that the team had recently "patented a design for a full-scale quantum computer chip that would allow for millions of our qubits, all doing the types of calculations that we've just experimentally demonstrated."

      He said that a key next step for the project is to identify the right industry partners to work with to manufacture the full-scale quantum processor chip.

      ISTM that if you want to find the right industry partners and avoid a lot of "it can't be done" BS, there are worse ways than first publishing a paper in a prestigious journal.

      --
      We don't see the world as it is, we see it as we are.
      -- Anais Nin
    5. Re:Translation ... by ichthus · · Score: 1

      01001110 01101111

      --
      sig: sauer
    6. Re:Translation ... by esonik · · Score: 1

      The authors report coherence times of 120us and 61us for the two (slightly different) Qubits. Experimental evidence for Qubit Q2 is provided in the Supplementary Material and for Qubit Q1 in reference 4.

      Also, citing:
      " the error can be less than 1%, corresponding to a fidelity above 99% for the two-qubit CZ gate. The fast two-qubit operation frequency implies also that over 100,000 CZ gates can be performed within the single-qubit coherence time. [4]"

      and further

      "The tremendeous progress of quantum error correction codes over the last decade has resulted in schemes that allow fault-tolerant quantum computing with single and two-qubit errors as high as 1% [10]; values that already seem consistent with the fidelities of these silicon quantum dot qubits. These qubit fidelities could be further improved by lowering the sensitivity to electrical noise. This could be achieved by designing the two-qubit system such that it is completely decoupled from the reservoir during qubit control, possibly by additional pulsing on the barrier gates."

    7. Re:Translation ... by TeknoHog · · Score: 1

      So... does this mean I learned binary for nothing?

      Sometimes it does mean that and sometimes it doesn't mean that.

      Are you Shor?

      --
      Escher was the first MC and Giger invented the HR department.
    8. Re:Translation ... by DrJimbo · · Score: 1

      So... does this mean I learned binary for nothing?

      Sometimes it does mean that and sometimes it doesn't mean that.

      Are you Shor?

      There are several factors to consider, but just like Schroedinger's cation, I'm positive!

      --
      We don't see the world as it is, we see it as we are.
      -- Anais Nin
  6. Just imagine by rickb928 · · Score: 2, Funny

    How much closer they are to a Beowulf cluster of these...

    --
    deleting the extra space after periods so i can stay relevant, yeah.
    1. Re:Just imagine by myrdos2 · · Score: 1

      Wow. I just had a Pavlovian response to say something about Natalie Portman. I.. I think I need to go lie down now.

  7. Yes, but in parallel by Anonymous Coward · · Score: 2, Funny

    in case you need 0,1,2 or 3 factored really, reaaly fast.

    Science, huh?

  8. Re:How Big an Improvement Are We Talking Here? by dpidcoe · · Score: 1

    It's a different kind of improvement. It won't make your computer run crysis at 9000 fps, but you'd see it in things such as google maps being able to quickly calculate the most efficient path given that you want to travel from A to F and make stops B, C, D, and E along the way.

  9. Re:DOOMSDAY by n1ywb · · Score: 2

    eh they might not have it cracked yet but that doesn't matter because they'll just record it and crack it later

    --
    -73, de n1ywb
    www.n1ywb.com
  10. Re:Does this really lead to useful quantum compute by TechyImmigrant · · Score: 1

    It's a refrigeration problem.
    You need to get stuff very cold to dampen down the noise (other things entangling with your qbits).

    Making things cold takes energy. The lower the entropy in the qbits, the higher the energy that you blow in the refrigeration. Overall entropy will increase. So you might be able to equate the energy in the heat of serial computation of an O(2^n) problem to the energy spent cooling a circuit cold enough to solve an O(2^n) problem in parallel with magic quantum behaviors. Unfortunately in the parallel case you have to blow that energy all at the same time. If the serial case looks like it would need enough energy to boil all the oceans (about O(2^128)) then the parallel case might boil them all at once. You might want to get inland.

    --
    I should use this sig to advertise my book ISBN-13 : 978-1501515132.
  11. Re:How Big an Improvement Are We Talking Here? by tajribah · · Score: 1

    This does not seem to be likely, though. As far as I know, there is no polynomial-time quantum algorithm for solving the Traveling Salesman Problem, or any other NP-complete problem.

  12. Re:D-Wave by Tyrannosaur · · Score: 1

    My question is, if qubit gates have just been discovered, what the heck has D-Wave Systems been selling to Google and NASA in the past 2 years?

    Non-silicon based systems.

    and, significantly, did it in silicon

    This is really the only new thing that has happened. Which is significant, but it seems a significant portion of ./ users don't remember the story from june when we have seen over 1000 qbits demonstrated

  13. Re:How Big an Improvement Are We Talking Here? by As_I_Please · · Score: 1

    Not quite. There are very few algorithms that will see a substantial speedup on quantum computers, factoring numbers and simulating quantum systems being the big two. In fact, it wasn't until Shor's algorithm was discovered that physicists really took an interest in quantum computers since no one knew if there was anything a quantum computer could do better than a Turing machine. For general problems, you can only get a modest speedup over a brute force search on a classical computer. To find an entry in an unsorted database takes O(n) on a classical computer and O(sqrt(n)) on a quantum computer (Grover's algorithm). To get better results, the problem has to have some special property that is amenable to encoding in a quantum system (the quantum Fourier transform in the case of Shor's algorithm).

    For now, it seems that quantum computers won't help with NP-complete problems.

  14. Uh, D-Wave produces Quantum Computers already? by Kisai · · Score: 1

    Quantum Computers already exist...
    http://www.dwavesys.com/d-wave-two-system

    Perhaps TFA could be more specific on what aspect this changes.

    1. Re:Uh, D-Wave produces Quantum Computers already? by JoshuaZ · · Score: 1

      D-Wave's claimed quantum computers depend very much on what you call a quantum computer. D-Waves machines use a form of quantum annealing https://en.wikipedia.org/wiki/Quantum_annealing but they are not a universal quantum computer in the traditional sense, and even for quantum annealing they are very limited in what they can do and it isn't even clear that the problems that the D-Wave machine can do are any problems where we should expect any actual speedup from a quantum computer, and certainly the D-Wave machines have no capability for doing many of the problems we do want to use quantum computers for like factoring large integers.

  15. Re:How Big an Improvement Are We Talking Here? by As_I_Please · · Score: 1

    Here's a presentation on the topic by Scott Aaronson, a computer scientists at MIT: http://www.scottaaronson.com/t...

  16. Brute force? by fyngyrz · · Score: 1

    I may misunderstand this -- my quantum physics are hazy at best -- but I am under the impression that "brute force" isn't the leverage that quantum computing will apply to the problem.

    Can anyone who actually understands what a quantum computer could do give us (ok, me) a lesson on the nature of the threat to encryption?

    --
    I've fallen off your lawn, and I can't get up.
    1. Re:Brute force? by Bob+the+Super+Hamste · · Score: 1

      As others have mentioned both Grover's and Shor's algorithms which do better than regular brute force when applied to the correct type of cryptography. For symmetric key crypto it makes the problem substantially easier as in it effectively halves the key length. Even effectively halving the key length would require brute forcing the rest of the work, assuming the algorithm isn't broken in other ways. For asymmetric key crypto like RSA it is broken as prime factorization is trivial using quantum computers. The issue around elliptical curve public key crypto is that most believe it is compromised by the NSA with their choice of values so quantum computers aren't really needed there. For public key crypto there is still Lattice-based public key crypto which appears to be immune to quantum attack.

      --
      Time to offend someone
  17. Link to paper at arxiv.org by Anonymous Coward · · Score: 4, Informative

    Hi everyone,

    If you don't have a subscription to Nature, you download a copy of the preprint from arxiv.org at this link.

    http://arxiv.org/pdf/1411.5760.pdf

    Enjoy! This is great Science. Even without the really cool Quantum effects, this technology has potentially far higher logic densities than CMOS.

  18. Wake me when they get to 10,000 or so qubits by Myria · · Score: 1

    The original Xbox's 2048-bit RSA key and I have some unfinished business from more than a decade ago.

    --
    "Screw Sun, cross-platform will never work. Let's move on and steal the Java language." - Visual J++ Product Manager
  19. There's an upside to losing asymmetric crypto by Myria · · Score: 1

    No more locked bootloaders like Secure Boot or iBoot.

    --
    "Screw Sun, cross-platform will never work. Let's move on and steal the Java language." - Visual J++ Product Manager
  20. More info here: by dsmatthews9379 · · Score: 2

    http://www.engineering.unsw.ed... http://www.cqc2t.org/research And the patent docs https://register.epo.org/appli...

  21. A Beowulf cluster by Notorious+G · · Score: 1

    Imagine a Beowulf cluster of these! Sorry, been wanting to say that for years ...

  22. Billion dollar investment in perpetual motion. by Anonanonaon · · Score: 1

    Sorry, but every time I dig into this, it seems to reduce to a complicated version of trying to get something out of a balanced system which won't budge due to the Laws of Reality.

    If you could just get one of those fridge magnets to turn off for half the engine cycle, you could build a truly awesome car! But fridge magnets don't give free lunches.

    Similarly, if try to pull a measurement out of your q-bit, it stops being in super position and just becomes another dumb binary switch.

    Solving a problem is the same as trying to sneak an observation of particles acting as waves.

    If your quantum computer solves a problem, an encryption riddle, for instance, then that proves its q-bits were in superposition, which instantly means they weren't.

    I thought the double slit experiment adequately demonstrated this.

    I suspect that the only solutions to this reality gridlock can be found by the likes of Douglas Adams. Though, spending billions of dollars and hundreds of thousands of research hours on the problem is pretty close to the kind of narrative Douglas Adams enjoyed telling.

  23. Re: Does this really lead to useful quantum comput by TechyImmigrant · · Score: 1

    How many moons do you need to make an effective cluster?

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    I should use this sig to advertise my book ISBN-13 : 978-1501515132.