Why every quantum computer will need a powerful classical computer
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Yeah - I am glad they are getting a handle on how to functionally make this work - but man - that really is a big chunk of classical processing to bite off every second!
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I'm forever grateful to Ars (and the commenters) for their ability to convey these complicated topics to me an a way that's just understandable enough to make me forget I still have no idea how quantum computing works or is supposed to work despite probably reading or grazing at least 50 (good!) articles on the topic.
"The future of computing is checking for errors at a rate of 100TB per second!"
* brain aneurysm *
Always interesting to read, though!
"The future of computing is checking for errors at a rate of 100TB per second!"
* brain aneurysm *
Always interesting to read, though!
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WinternetHexplorer
Smack-Fu Master, in training
So what is an "interesting" versus "sophisticated" calculation? For the current state of the technology, does interesting lie in the range of long division, or more along the lines of factoring for large prime numbers for some cryptographical applications? What about sophisticated calcs?
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So, next question - do you have to keep a copy of all that data so you can replay it all to figure out if something went wrong?
And if yes, what sort of storage systems are they talking about? Exabyte size? Or larger? (considering that a petabyte sized storage device will be full in 10 secs at 100 TB per sec, it does not seem big enough). And what sort of connectivity?
And if yes, what sort of storage systems are they talking about? Exabyte size? Or larger? (considering that a petabyte sized storage device will be full in 10 secs at 100 TB per sec, it does not seem big enough). And what sort of connectivity?
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So, "interesting" in this case starts at roughly 100 error-corrected qubits, and involves a complete quantum simulation of a modest sized molecule. "Sophisticated" includes the sort of algorithms that inspired quantum computing in the first place, like factoring two large primes.
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Yeah; from my understanding, what's needed is not a "powerful classical computer" per se, but a specific type of powerful classic processing. Storage will need to scale to match the qbit comparisons required, with a fraction of that again to handle the comparison operations. There will then need to be a qbit mapper that can set a flag for any qbit that fails an equivalency test. We won't need the classic register/accumulator/processor structure that a modern classic computer has though; it's mostly about high volume throughput calculations backed by a basic state machine.
Replays are theoretically possible, but your qbits will be in the wrong state, so any replay is going to be HUGE since it first needs to reset the entire system. Seems to me the more likely route would be some level of redundancy where the statistical significance of the result degrades by a known and calculated amount, but the calculation continues. The algorithm could also have extra loops in it that come into play if the error margins get too large for a significant result.
"From my understanding" is a significant caveat though; I'm no quantum computing engineer.
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And the next question becomes: how much and what kind of benefits are we getting from the quantum computer vs. what we would get if we just used that classical computing power for...classical computing?
If it requires as much or more error correcting capability to allow quantum solutions as it would to use classically deterministic solutions to the same problems, we're not gaining much. Or maybe we're only gaining at very large scales or very specific problems or something of that sort?
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Now I get it.
Quantum Computing and Fusion Power Generation are both around the corner,
and only a decade or so away.
They both take massive infrastructure that offsets production severely.
And it sounds like we might need one for the other.
Quantum Computing and Fusion Power Generation are both around the corner,
and only a decade or so away.
They both take massive infrastructure that offsets production severely.
And it sounds like we might need one for the other.
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Downvoters, be nice! This was just a comment intended for a different thread, and who among us…
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Nothing like building a machine that outputs a shitload of bad data that you have to sift through for the possibility of it being right 1% of the time. Literally don't sneeze in the room, or 50ft away from it.
Reminds me of the video of some datacenter techs that would yell at a JBOD and show all of the metrics jump around due to the vibration.
Edit: Here it is.
View: https://www.youtube.com/watch?v=tDacjrSCeq4
Reminds me of the video of some datacenter techs that would yell at a JBOD and show all of the metrics jump around due to the vibration.
Edit: Here it is.
View: https://www.youtube.com/watch?v=tDacjrSCeq4
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The classical compute described in the article isn't generalized compute like you're probably thinking - the headline is mildly misleading in what it's implying. It's powerful in the sense that it'll (theoretically) scale to huge amounts of data handled per second, for sure. If you had to do that on an x86 or ARM computer, you'd probably be right on the money about the cost/benefits. But because they've designed dedicated hardware, they've traded the flexibility and relative inefficiency of those architectures for being really efficient at doing one thing.
I don't know enough about quantum computing to know how qubit scaling aligns to the problems solved, but my basic understanding is that you'd only need a few hundred/thousand qubits to get into really interesting territory that classical supercomputers struggle with. Assuming this chip scales somewhat linearly (starting at 8mW per logical qubit per the article), then you're still in the single/double-digit watt range by the time you get there. Total energy consumption will certainly be higher for various reasons, but even an order of magnitude or two higher is miniscule compared to the supercomputer it's theoretically replacing.
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This is literally true. I didn't understand Euler's identity until I saw the 3blue1brown video with the animation that shows a circle "unrolling" onto the complex plane.
Suddenly it made perfect sense. Euler's identity isn't some "strange, beautiful, inconceivable" quirk of mathematics that I had been lead to believe. After seeing the visualization I thought, "oh! Well of COURSE it's like that! It couldn't possibly be any other way!"
3D graphics are essentially a necessity for properly teaching high level math. I say "essentially" because while not required per se, I'm pretty sure 3blue1brown's videos alone could improve college level math grades across the world by a very significant amount. It helps that he wrote his own software for the animations he makes, that's really what sets his stuff apart. Which is open source, of course. Of courses courses should be using the open source course s- eh I'm trying too hard for this pun I'll stop have a nice evening everyone
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There should be a "sidevote" button for these kinds of pun posts. The internet equivalent of a collective groan.
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That 100tb throughout sounds impressive but I'm wondering how it stacks up with traditional silicon - such as the l3 cache throughput on a modern processor? Is this throughput really that big a jump or is it more the application here that's noteworthy? (I googled around a bit for an answer for l3 cache bandwidth but didn't see an obvious answer, so hoping someone here can put this in context).
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This chip isn't replacing a supercomputer, it is just a small component in the system. The big power draw with creating/maintaining physical qbits is still going to be there.
I think the innovation here is adding capability without increasing the (already massive) power draw significantly.
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I wonder at times if we're looking at quantum computing all wrong and that perhaps we should consider that errors are simply going to be a part of such computations, and build around that expectation.
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100TB. Big B. Impressed yet?
Dual channel DDR5 at 6000 on a Zen4 CPU hits ~96GB/s?
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I found that detail surprising. My understanding of quantum error correction led me to believe that far fewer qubits would be needed.
To guarantee that a classical bit (cbit) is transmitted correctly, send it three times. Any single bit error can be detected and corrected using this encoding. Qubits are more complex (pun intended.) States like |0> + |1> and |0> - |1> differ only in phase, which has no equivalent concept in cbits.
Quantum error correction would seem to be impossible, since you can't copy qubits (the no cloning theorem) and measuring them destroys their entanglement. The One Weird Trick that makes it work is to entangle some other qubits with the encoded qubits, and then measure these ancillary qubits. You won't gain any useful information from this measurement about the actual state of the encoded qubits - again, the no cloning theorem prohibits that - but you can learn if an error occurred and how to correct it!
Yes, that's as bizarre as it sounds. Welcome to quantum computer science. That's what these guys are doing in their FPGAs: detecting the error state of the encoded qubit and calculating the appropriate error correction to apply to the encoding.
In his original paper on quantum error correction, Schor (yes, the same Schor from the prime factoring algorithm) found a nine-qubit encoding that corrects all types of qubit errors. It has since been proven that five is the minimum needed, although it requires quantum gates that are difficult to realize in hardware. A seven qubit-encoding that uses only simple gates looks like the sweet spot. Hence my confusion about dozens of qubits needed for each logical qubit.
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Thank you so much for all this! Even though I read the article, I was unclear on how reliable error detection actually was with this method. I had presumed that full error protection was flat out impossible without using other quantum bits which themselves would be prone to errors. It's clear you know your stuff.
All I can presume, taking what you've said in combination with the article, is that it's a matter of the difference between a theoretical minimum and practical realities that complicate construction and make that 7 qubit minimum infeasible.
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This appears to be a not-uncommon typo where further instances in the same source texts (often academic/scientific) show "ion trap". Apparently more non-technical people are involved in working up papers than I would have expected.
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Thanks - that is good context but "on wafer" throughput to L3 cache should be much, much faster that bus throughput to ddr5 ram right? L3 cache transfer speed is typically measured in cpu clock tics not seconds (which is why it was hard for me to find out its per sec bandwidth), but suggests to me that it's very fast when compared to ram (it's literal point is to hold data so the cpu doesn't have to ask for data over the slower ram bus)..
I'm just curious if this company has developed new solutions or if this is similar to what's been done on silicon before and they are applying it to a new problem in a clever way?
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I remember back when quantum computing was first seeming viable people were saying it was going to be able to real time crack the encryption used to secure internet traffic and would cause huge problems...so I guess it's great to see that hasn't happened at least
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Yeah, I was attempting to reference the chip and the total energy cost it would add to the overall system - chiplet tax, extra data buses, etc. I tried to look into estimates of energy consumption per real qubit to compare, but couldn't really find anything I was comfortable with using for hard numbers. It did bring up a different concern - since this chip needs some multiples of real qubits to simulate a logical qubit, that would certainly inflate the energy needs of an entire system. But that leads to an entire rabbit trail of relative efficiencies and scaling impacts that I just don't feel qualified to comment on.
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Or that oversized crook they use to pull bad performances off the stage?
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