4 ms·

> So how many gates are we talking to factor some "cryptographically useful" number? That is a hard question to answer for two reasons. First, there is no bri

by lisper 1y ago

> So how many gates are we talking to factor some "cryptographically useful" number? That is a hard question to answer for two reasons. First, there is no bright line that delineates "cryptographically useful". And second, the exact design of a QC that could do such a calculation is not yet known. It's kind of like trying to estimate how many traditional gates would be needed to build a "semantically useful" neural network back in 1985. But the answer is almost certainly in the millions. [UPDATE] There is a third reason this is hard to predict: for quantum error correction, there is a tradeoff between the error rate in the raw qbit and the number of gates needed to build a reliable error-corrected virtual qbit. The lower the error rate in the raw qbit, the fewer gates are needed. And there is no way to know at this point what kind of raw error rates can be achieved. > Is there some pathway that makes quantum computers useful this century? This century has 75 years left in it, and that is an eternity in tech-time. 75 years ago the state of the art in classical computers was (I'll be generous here) the Univac [1]. Figuring out how much less powerful it was than a modern computer makes an interesting exercise, especially if you do it in terms of ops/watt. I haven't done the math, but it's many, many, many orders of magnitude. If the same progress can be achieved in quantum computing, then pre-quantum encryption is definitely toast by 2100. And it pretty much took only one breakthrough, the transistor, to achieve the improvement in classical computing that we enjoy today. We still don't have the equivalent of that for QC, but who knows when or if it will happen. Everything seems impossible until someone figures it out for the first time. --- [1] https://en.wikipedia.org/wiki/UNIVAC_I#Technical_description https://en.wikipedia.org/wiki/UNIVAC_I#Technical_description

deleted 1y ago
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fhdkweig 1y ago
>> Is there some pathway that makes quantum computers useful this century? > This century has 75 years left in it, and that is an eternity in tech-time. As a comparison, we went from first heavier than air flight to man walking on the moon in only 66 years.
- thechao 1y ago
  My great grandmother, who was born in 1891, asserted ca. 1990 that her favorite invention was large print novels. More importantly: the social right to read trashy novels. But, yeah, computers, planes, starships, nuclear power, etc etc.
- eastbound 1y ago
  > to man walking on the moon in only 66 years And that was before Epoch (1969, unix time started in 1970). We went from calculator to AI in 55 years, which is, actually, extremely long. It took exactly the time to miniaturize CPUs enough that you would hold as many gates in a GPU as neurones in a human’s brain. The moment we could give enough transistors to a single program, AI appeared. It’s like it’s just an emergent behavior.
  - jacquesm 1y ago
    > We went from calculator to AI in 55 years, which is, actually, extremely long. I think it is insanely fast. Think about it: that planet has been here for billions of years. Modern humanity has been here for 200,000 years, give or take. It took 199700 years and change to get to a working steam engine. 266 years later men were walking on the moon and another 55 years and we had a good facsimile of what an AI looks like in practice. That's insane progress. The next 75 years are going to be very interesting, assuming we don't fuck it all up, the chances of which are right now probably 50/50 or so.
    - lttlrck 1y ago
      If this is what AI is going to look like in practice it's a big letdown. Science fiction has been predicting what an AI would be like for over a hundred years, there was even one in a movie in 1927. We're so far from what we dream that, to me, it feels like a mere leaf blowing in the wind compared to the Wright Flyer.
      - jacquesm 1y ago
        It's not what it can do today (which is already pretty impressive) it is what it can do in another century, which too is a relatively short time. The Wright Flyer was a complete aircraft but small, awkward and not very practical. But it had all of the parts and that was the bit that mattered. LLMs are not a 'complete AI' at all, they are just a very slick imitation of one through a completely different pathway. Useful, but not AI (at least, not to me). Meanwhile, a very large fraction of the users of OpenAI, Claude etc all think that AI has arrived and from that perspective it is mostly the tech crowd that is disappointed. For the rest of the people the thing is nothing short of magic compared to what they were able to do with a computer not so long ago. And for people like translators it is a massive threat to their jobs, assuming they still have one. It is both revolutionary and a letdown, depending on your viewpoint and expectations.
ted_dunning 1y ago
Good reminder on the time scale. On the other hand, the Univac could do more useful work than current quantum computers.
TheOtherHobbes 1y ago
It's not an eternity because QC is a low-headroom tech which is already pushing its limits. What made computing-at-scale possible wasn't the transistor, it was the precursor technologies that made transistor manufacturing possible - precise control of semiconductor doping, and precision optical lithography. Without those the transistor would have remained a lab curiosity. QC has no hint of any equivalent breakthrough tech waiting to kick start a revolution. There are plenty of maybe-perhaps technologies like Diamond Defects and Photonics, but packing density and connectivity are always going to be huge problems, in addition to noise and error rate issues. Basically you need high densities to do anything truly useful, but error rates have to go down as packing densities go up - which is stretching optimism a little. Silicon is a very forgiving technology in comparison. As long as your logic levels have a decent headroom over the noise floor, and you allow for switching transients (...the hard part) your circuit will be deterministic and you can keep packing more and more circuitry into smaller and smaller spaces. (Subject to lithography precision.) Of course it's not that simple, but it is basically just extremely complex and sophisticated plumbing of electron flows. Current takes on QC are the opposite. There's a lot more noise than signal, and adding more complexity makes the problem worse in non-linear ways.
- lisper 1y ago
  I'm sympathetic to this argument, but nearly every technological breakthrough in history has been accompanied by plausible-sounding arguments as to why it should have been impossible. I myself left my career as an AI researcher about 20 years ago because I was convinced the field was moribund and there would be no major breakthroughs in my lifetime. That was about as well-informed a prediction as you could hope to find at the time and it was obviously very wrong. It is in the nature of breakthroughs that they are rare and unpredictable. Nothing you say is wrong. I would bet against QC is 5 years (and even then I would not stake my life savings) but not 75.
  - lqstuart 1y ago
    In fairness, the biggest breakthrough in AI has been calling more and more things “AI.” Before LLMs it was content based collaborative filtering.

by lisper 1y ago

deleted 1y ago

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fhdkweig 1y ago

>> Is there some pathway that makes quantum computers useful this century? > This century has 75 years left in it, and that is an eternity in tech-time. As a comparison, we went from first heavier than air flight to man walking on the moon in only 66 years.

thechao 1y ago
My great grandmother, who was born in 1891, asserted ca. 1990 that her favorite invention was large print novels. More importantly: the social right to read trashy novels. But, yeah, computers, planes, starships, nuclear power, etc etc.
eastbound 1y ago
> to man walking on the moon in only 66 years And that was before Epoch (1969, unix time started in 1970). We went from calculator to AI in 55 years, which is, actually, extremely long. It took exactly the time to miniaturize CPUs enough that you would hold as many gates in a GPU as neurones in a human’s brain. The moment we could give enough transistors to a single program, AI appeared. It’s like it’s just an emergent behavior.
- jacquesm 1y ago
  > We went from calculator to AI in 55 years, which is, actually, extremely long. I think it is insanely fast. Think about it: that planet has been here for billions of years. Modern humanity has been here for 200,000 years, give or take. It took 199700 years and change to get to a working steam engine. 266 years later men were walking on the moon and another 55 years and we had a good facsimile of what an AI looks like in practice. That's insane progress. The next 75 years are going to be very interesting, assuming we don't fuck it all up, the chances of which are right now probably 50/50 or so.
  - lttlrck 1y ago
    If this is what AI is going to look like in practice it's a big letdown. Science fiction has been predicting what an AI would be like for over a hundred years, there was even one in a movie in 1927. We're so far from what we dream that, to me, it feels like a mere leaf blowing in the wind compared to the Wright Flyer.
    - jacquesm 1y ago
      It's not what it can do today (which is already pretty impressive) it is what it can do in another century, which too is a relatively short time. The Wright Flyer was a complete aircraft but small, awkward and not very practical. But it had all of the parts and that was the bit that mattered. LLMs are not a 'complete AI' at all, they are just a very slick imitation of one through a completely different pathway. Useful, but not AI (at least, not to me). Meanwhile, a very large fraction of the users of OpenAI, Claude etc all think that AI has arrived and from that perspective it is mostly the tech crowd that is disappointed. For the rest of the people the thing is nothing short of magic compared to what they were able to do with a computer not so long ago. And for people like translators it is a massive threat to their jobs, assuming they still have one. It is both revolutionary and a letdown, depending on your viewpoint and expectations.

ted_dunning 1y ago

Good reminder on the time scale. On the other hand, the Univac could do more useful work than current quantum computers.

TheOtherHobbes 1y ago

It's not an eternity because QC is a low-headroom tech which is already pushing its limits. What made computing-at-scale possible wasn't the transistor, it was the precursor technologies that made transistor manufacturing possible - precise control of semiconductor doping, and precision optical lithography. Without those the transistor would have remained a lab curiosity. QC has no hint of any equivalent breakthrough tech waiting to kick start a revolution. There are plenty of maybe-perhaps technologies like Diamond Defects and Photonics, but packing density and connectivity are always going to be huge problems, in addition to noise and error rate issues. Basically you need high densities to do anything truly useful, but error rates have to go down as packing densities go up - which is stretching optimism a little. Silicon is a very forgiving technology in comparison. As long as your logic levels have a decent headroom over the noise floor, and you allow for switching transients (...the hard part) your circuit will be deterministic and you can keep packing more and more circuitry into smaller and smaller spaces. (Subject to lithography precision.) Of course it's not that simple, but it is basically just extremely complex and sophisticated plumbing of electron flows. Current takes on QC are the opposite. There's a lot more noise than signal, and adding more complexity makes the problem worse in non-linear ways.

lisper 1y ago
I'm sympathetic to this argument, but nearly every technological breakthrough in history has been accompanied by plausible-sounding arguments as to why it should have been impossible. I myself left my career as an AI researcher about 20 years ago because I was convinced the field was moribund and there would be no major breakthroughs in my lifetime. That was about as well-informed a prediction as you could hope to find at the time and it was obviously very wrong. It is in the nature of breakthroughs that they are rare and unpredictable. Nothing you say is wrong. I would bet against QC is 5 years (and even then I would not stake my life savings) but not 75.
- lqstuart 1y ago
  In fairness, the biggest breakthrough in AI has been calling more and more things “AI.” Before LLMs it was content based collaborative filtering.