7 ms·

The need for quantum computers remains small

89 points by hunglee2 4y ago

lxe 4y ago
A great writeup about Shor's algorithm linked in the article: https://scottaaronson.blog/?p=208 https://scottaaronson.blog/?p=208
soganess 4y ago
Barring the sky falling, our best bet for NP hard problems is approximate solutions that have provable lower bounds on approximation ratio. From that purview, a general heuristic for approximating combinatorial optimization problems would be a godsent. Even if algorithms like the QAOA do not improve(or tightly match) approximation ratios beyond that of a carefully crafted classical algorithm... A turn key algorithm on a coherent high-qubit-count quantum computer would change the industrial use landscape forever. The number of developer hours saved would be uncountable. We're just aiming way too dang high.
- elcritch 4y ago
  I mean that sounds a lot like what DWave and Google are pursuing with the adiabatic QCs.
- pyinstallwoes 4y ago
  Kind of like how instead of modeling the entire economy and figuring out how to influence the behavior, you just identify a key parameter such as inflation or interest rates and modify that to affect every possible outcome.
rektide 4y ago
The need is high... for bad people doing bad things to everyone else (trying to de-secure the world)? There's some hypothetical travelling salesperson style questions we might ask. But we don't seem incapable of doing this work today. 98% the needs seem like: can we break the world's crypto. How is this anything beyond a chaotic evil mis-use? How will this do anything but de-secure & instigate risk across the planet? At least when 99.5% of the engineers were working on ads, they were just wasting their time doing amoral shit. This seems actively immoral. I really struggle to understand what this all is good for. There probably are some valid & good uses. But it's all hyper-abstract, with little grounding. The attempt to hipster-ize the facilities, to make the physical systems themselves look cool, to present an impressive front: it all works counter to the very essence that made computing cool for so much of my growing-up period: computing in my era was personal. It empowered people. I don't see how this will help actual people at all. It seems mostly like a big hard problem for which the winner reaps some eventual explotative spoils. At likely cost to general world order & peace. Hiss boo.
- amelius 4y ago
  Computational chemistry (e.g. protein folding) is one useful application.
  - femto 4y ago
    Which leads onto computational medicine. The advent of SPICE [1] meant that with the right models electrical engineers could simulate complex electrical systems, do sensitivity analysis and make integrated circuits that had a high probability of working. Imagine a (quantum) simulator that can rapidly simulate all or part of the human body. The effects of medicines could be rapidly simulated, or the simulation could guide the design of treatments. Eventually, if the simulation becomes as accurate as SPICE can be today, it would be possible to go directly from the design of a treatment to its administration, secure in the knowledge that it is unlikely to cause problems. [1] https://en.wikipedia.org/wiki/SPICE https://en.wikipedia.org/wiki/SPICE
    - exmadscientist 4y ago
      Why do you believe a quantum computer can actually solve that problem? The whole point of the article is that quantum computers are not and can never be general-purpose computers. And something with as many inputs as "simulate the human body" seems like the exact opposite of what you can encode in qubits, evolve as a state vector, and usefully read out.
      - cycomanic 4y ago
        The point is that for these sort of simulations you don't want a general purpose computer. Ideally you have a "equivalent" of the quantum mechanical Hamiltonian that you can manipulate/design and read effects out from. Now to simulate the human body probably requires a prohibitively large number of qubits, however for many very useful things you don't need that.
        exmadscientist 4y ago
marcosdumay 4y ago
Only people that deal with stuff created by chemical reactions have a need for quantum computers... None else.
mtlmtlmtlmtl 4y ago
I wonder if quantum computing is just a mirage that results from looking too much at the time complexity of quantum algorithms versus the cost in qubits, which are still wildly expensive. Maybe qubits will just never scale to the number of qubits needed to meaningfully outperform classical computers.
- dataflow 4y ago
  Yeah lots of people think decoherence will prevent QC from becoming practically useful. Some researchers seem to think differently, but I never found an explanation for why I should be as optimistic as they are.
  - ramraj07 4y ago
    Which side is Scott Aaranson on? Just curious.
    - dataflow 4y ago
      The only link I have handy is this comment from him in 2019 [1]. I feel like I've seen more in the past, but I can't find them now. [1] https://scottaaronson.blog/?p=4372from=timeline#comment-1822765 https://scottaaronson.blog/?p=4372from=timeline#comment-1822...
    - mtlmtlmtlmtl 4y ago
      Doesn't he work on QC from the theory side? I assume he has at least some faith if he's spending his time on it. He's on Sean Carroll's podcast talking about this stuff but I can't remember what stance he took on it. I know Stephen Wolfram isn't too excited. But I believe his issue was more that algorithms end with "and then a measurement happens", which might be quite tricky and possibly even cancel out any potential gains. Not sure about the details of that, but it makes superficial sense given the nature of measurement in QM.
      - bowsamic 4y ago
        Why would quantum measurement be a problem in any way? Obviously measurement doesn’t destroy quantum effects, else we would not be able to see QM in the first place. Obviously you have to factor in what the measurement does to your quantum computer, but that’s obviously just part of your design in the first place
glitchc 4y ago
Reminds me of this: https://ieeexplore.ieee.org/document/4051190 https://ieeexplore.ieee.org/document/4051190 Back then a digital computer couldn’t hold a candle to an analog one and processed only a few bits at a time. It was slow and imprecise. Look at where we are now. A general quantum computer is a fundamentally different kind of computer. Those who cannot imagine what can be done with one lack the imagination to understand foundationally new technology and are unable to invent their own.
- tjr225 4y ago
  It seems that nobody on the planet is able to invent their own quantum computer.
  - chasil 4y ago
    Actually, a 65-qubit quantum computer has been created. "IBM's current largest quantum computer, revealed this month, contains 65 qubits." https://www.science.org/content/article/ibm-promises-1000-qubit-quantum-computer-milestone-2023 https://www.science.org/content/article/ibm-promises-1000-qu...
    - brokensegue 4y ago
      I'm not an expert but I think because of the error correction mechanisms the effective number of quibits is smaller than that
      - _8091149529 4y ago
        No quantum computing platform today has meaningful error correction. What you can get, in some cases, is limited error detection based on the outcome of the question computation, if it's built into your specific algorithm.
    - sgt101 4y ago
      There is a big difference between a practical QC and the QC we have now. 65bits isn't practical for any known real problem but ask also how long it takes to boot it, how many cycles it can execute per run and how many runs it can do per day (or week). These thing are not like your laptop, they are more like particle accelerators.
cc101 4y ago
I remember when the Commodore 64 came out. "64K RAM?", I thought, "What could anyone do with so much RAM?" Power to do something new always generates new things to do with it.
- jchw 4y ago
  You're only following the winners, but computer science has also had a lot of flops, too. Time will tell if quantum computers is one of those, but it sure isn't looking great so far.
  - reacweb 4y ago
    At that time QL Sinclair was a loser. A good computer that never got programs. It was the computer of Lius Torwalds and the reason he had to write himself programs. Without QL Sinclair, we may never had Linux. At my work, I was present when the research on ASAS (https://skybrary.aero/articles/airborne-separation-assurance-systems-asas https://skybrary.aero/articles/airborne-separation-assurance...) led to the idea of PMS (https://www.eurocontrol.int/sites/default/files/2021-05/eurocontrol-point-merge-guide-v1-4.pdf https://www.eurocontrol.int/sites/default/files/2021-05/euro...). Never underestimate serendipity
    - jchw 4y ago
      While that's a neat story, I'm not sure if it has a lot to do with the practical applicability of quantum computing. I didn't mean to single out Commodore or their CBM64, I really mean to say that there are plenty of examples of entire technologies that were hyped and then flopped, not just market competitors in a given technology that is already mostly proven.
    - einpoklum 4y ago
      > we may never [have] had Linux. Oh, come on. Linux was a clone of MINIX with a GPL license. If Linus had not written it, somebody else would have; and at worst (if that is worse), we would have all been running FreeBSD now.
bpodgursky 4y ago
I think there is a world market for about five quantum computers.
O__________O 4y ago
Are quantum computers being used in economically significant ways that only are possible with quantum computers yet? If so, what is the best example? Last time I checked few years ago, my understanding was the answer was still no; specifically, believe I asked Scott Aaronson as a follow up question to a talk he gave: https://www.scottaaronson.com/ https://www.scottaaronson.com/
- cycomanic 4y ago
  The short answer is no, I think Ising machines are much closer or even there for specific problems. They are somewhat similar to quantum computers, but entirely classical (Dwave was shown to be equivalent to an Ising machine IIRC).
- bowsamic 4y ago
  No
blueprint 4y ago
No, per Susskind, we need entangled quantum computers of sufficient size to do wormhole experiments!
LeegleechN 4y ago
He's not wrong about the narrow algorithmic use cases (so far), but he's completely missing the utility for simulation of quantum phenomena (chemistry, microbiology, materials science). That use case alone completely justifies investing into them even if you don't care about advancing science.
- bowsamic 4y ago
  Yeah the problem is in the name and the marketing. People think it is meant to replace normal computers, but that is totally wrong. The simulation use cases as well as probing fundamental physics are far more immediate and exciting
  - baby 4y ago
    And there’s all the crypto FUD that quantum computers will scale enough to break crypto algorithms
    - hnfong 4y ago
      It hasn't happened yet or won't happen any time soon, but if there's a chance RSA is going to be broken I'd rather be aware of the possibility 10 years earlier than 10 days after...
- credit_guy 4y ago
  Out of curiosity, how many qubits would you need to simulate the molecule of water?
  - tokamak 4y ago
    Can QC simulate that?
    - ki_ 4y ago
      QC cant do anything, it has no use cases. And that won't change. Except if you want to generate random numbers. that it can do.
tho2u43234 4y ago
That's probably because "real" quantum computing today can't even factor 4-bit numbers. The coherent-bits are really not scaling fast enough (and this is to be expected given their entanglement IMO) for anyone to really care other than snazzy startups scamming investors of their money.
- johnebgd 4y ago
  Yeah, quantum computing is still basically experimental…
  - pyinstallwoes 4y ago
    Experimental, non-physical, completely theoretical. Yep.
yshvrdhn 4y ago
I would argue its similar to how we thought of computers when they first came out ?
feliyur 4y ago
From my limited understanding, a quantum computer performs computations over probability distributions, rather than over numerical values. Performing precise computations over probability distributions is a serious problem in many domains - physical simulations are just one. Another example is that could allow much more efficient and precise data fusion, and as a result - a leap in AI abilities, across domains where AI is used.
- yccs27 4y ago
  Unfortunately, even though a quantum computer "manipulates wavefunctions", you can still only measure the outcome once. The magic has to happen somewhere in between state preparation and measurement. It's more like a computer with an inbuilt RNG - but if you can reach the same result via multiple execution paths, the probabilities don't just add, but they can interfere like in-phase/out-of-phase oscillatins.
hit8run 4y ago
So did the need for computers before the revolution started. It’s just a matter of time
- vanviegen 4y ago
  > It’s just a matter of time Why? Not every new tech solves a problem people actually have..
- morelisp 4y ago
  "Computers" are named after the teams of humans previously tasked with doing what they now do, a relatively common job in the first half of the 20th century and even irregularly earlier. The need was clear.
seydor 4y ago
Quantum computers are a part of quantum mechanics that s more of a curiosity than something to be engineered at scale. There's so much more to explore in quantum mechanics outside computation that is not receiving commensurate funding. I guess it's because "computing" is what BigTech (who has the money to fund it) understands
- throwawayffffas 4y ago
  I was under the impression that it was because quantum computers would make the simulation of quantum mechanics significantly faster as well.
lizardactivist 4y ago
Is there any demonstration of practical, usable QC yet? I'm thinking of some kind of common computational work, with a clearly defined input and verified output, shown to be carried out at least an order of magnitude faster than our conventional computers.
- tokamak 4y ago
  Obviously not
nabla9 4y ago
Normal computers would have suffered the same fate if they were only good for scientific calculations. Computer revolution was funded by demand in business, gaming and automation. It's the cash flow that funds long term R&D. Not potential benefit. There is no such demand for quantum computers. Everyday problems have too small complexity for them to be useful even if algorithm exists. I suspect that computational biochemistry will have funders from drug firms and companies doing materials science to keep funding the research for quantum computing, but the total sum will not be billions per year like it was in computer revolution.
- varjag 4y ago
  Classical computers appeared and for the first decade existed purely because of scientific demand. Gaming and business were secondary effects.
  - nabla9 4y ago
    Scientific demand is enough to start something, not sustain huge annual investments. Global supercomputer market is roughly $6-7 billion. Nvidia, AMD together spend more into R&D than the whole market has sales. Scientific use is minuscule compared to business and entertainment needs. Quantum computers research gets millions or maybe few tens of millions funding. That's not enough.
budlebee 4y ago
It feels like I'm reading an article on Netscape browser that says, "AI is still useless."
derpherpsson 4y ago
If you are able of imagining the future, and capable of logical coherent thoughts, the statement "the need for quantum computers remains small" is just... damn narrow-minded and perhaps just plain stupid. If you can shave off a factor n in O(n^3) then O-B-V-I-O-U-S-L-Y it will change the world. If you don't see the obviousness in this, then why are you working with computers? Before you hate on me, did you even google "quantum computer"? Did you read the introduction section of the Wikipedia article?
- trention 4y ago
  The proportion of comp sci tasks that have practical importance for which a quantum computer can shave off a factor of ~000s seems to be sufficiently small to doubt it will "change the world".
- morelisp 4y ago
  I've read the introduction (and, uh, a lot more). What specific algorithms do you have in mind where quantum supremacy seems a) likely (or even possible) and b) enough of an improvement to be world-changing?
xwdv 4y ago
Don’t we need quantum computers to crack cryptography in reasonable time? Could be useful for surveillance or espionage purposes.
alpineidyll3 4y ago
If error correction can be made to work they would revolutionize human life by allowing the microscopic world to be predictable. The recent result about error correction in surface codes from the Google group is encouraging, but still several OOMs away from anything meaningful.
wintorez 4y ago
"I think there is a world market for maybe five computers." -- Thomas Watson, president of IBM, 1943
- rbanffy 4y ago
  I came here to say precisely that. We don’t know yet what they could be useful for because we don’t have a single one that’s as capable as conventional computers were in 1943.
- rbanffy 4y ago
  “Apple is already dead.” Nathan Myhrvold, former Microsoft CTO, 1997
- rbanffy 4y ago
  “There is no reason anyone would want a computer in their home.” Ken Olsen, founder of Digital Equipment Corporation, 1977
abeppu 4y ago
He sort of glosses by the need to upgrade from current cryptographic algorithms. But I wonder if in 20-30 years, we'll look back on the bad timing of having designed blockchains before post-quantum cryptography was on solid footing. Even if there are few problems where quantum computers have a clear advantage, it seems at least unfortunate that a lot of people spent a lot of time and resources building up "value" explicitly protected by those problems ... and decentralizing them in a way that makes upgrades challenging. We like to imagine that quantum computers will be creating value for society by doing simulations about cutting-edge scientific problems. What if it just lets rich companies impersonate long-dead bitcoin whales?
- tromp 4y ago
  I consider the odds of having quantum computers able to break discrete log within 3 decades to be rather minute. The challenges involved seem way larger than for something like making nuclear fusion commercially viable. I also have a very hard time believing that 1) physical reality supports computing with a superposition of 2^{256} states each with an accurate amplitude of magnitude 2^{-128}, and 2) that we can engineer systems preserving such accuracies.
  - abeppu 4y ago
    Care to shed more light on your intuitions? I get that the engineering challenges are hard (or we'd have figured it out by now). And everyone seems pretty bad at predicting how long it will take for us to build something fundamentally new. But from the physical impossibility side, what would have to be true/what would we learn if we discovered that physical reality _doesn't_ support quantum computation with a large number of qubits and sufficient accuracy? I did do a course which included some quantum computation material and the professor highlighted that it wasn't actually demonstrated whether nature would be so "extravagant" ... but I haven't heard anyone describe what the universe would need to be like to both support the quantum phenomena that we've already studied and demonstrated, but to disallow some larger/more complex arrangements of what seem to be the same principles.

89 points by hunglee2 4y ago

lxe 4y ago

A great writeup about Shor's algorithm linked in the article: https://scottaaronson.blog/?p=208 https://scottaaronson.blog/?p=208

soganess 4y ago

Barring the sky falling, our best bet for NP hard problems is approximate solutions that have provable lower bounds on approximation ratio. From that purview, a general heuristic for approximating combinatorial optimization problems would be a godsent. Even if algorithms like the QAOA do not improve(or tightly match) approximation ratios beyond that of a carefully crafted classical algorithm... A turn key algorithm on a coherent high-qubit-count quantum computer would change the industrial use landscape forever. The number of developer hours saved would be uncountable. We're just aiming way too dang high.

elcritch 4y ago
I mean that sounds a lot like what DWave and Google are pursuing with the adiabatic QCs.
pyinstallwoes 4y ago
Kind of like how instead of modeling the entire economy and figuring out how to influence the behavior, you just identify a key parameter such as inflation or interest rates and modify that to affect every possible outcome.

rektide 4y ago

The need is high... for bad people doing bad things to everyone else (trying to de-secure the world)? There's some hypothetical travelling salesperson style questions we might ask. But we don't seem incapable of doing this work today. 98% the needs seem like: can we break the world's crypto. How is this anything beyond a chaotic evil mis-use? How will this do anything but de-secure & instigate risk across the planet? At least when 99.5% of the engineers were working on ads, they were just wasting their time doing amoral shit. This seems actively immoral. I really struggle to understand what this all is good for. There probably are some valid & good uses. But it's all hyper-abstract, with little grounding. The attempt to hipster-ize the facilities, to make the physical systems themselves look cool, to present an impressive front: it all works counter to the very essence that made computing cool for so much of my growing-up period: computing in my era was personal. It empowered people. I don't see how this will help actual people at all. It seems mostly like a big hard problem for which the winner reaps some eventual explotative spoils. At likely cost to general world order & peace. Hiss boo.

amelius 4y ago
Computational chemistry (e.g. protein folding) is one useful application.
- femto 4y ago
  Which leads onto computational medicine. The advent of SPICE [1] meant that with the right models electrical engineers could simulate complex electrical systems, do sensitivity analysis and make integrated circuits that had a high probability of working. Imagine a (quantum) simulator that can rapidly simulate all or part of the human body. The effects of medicines could be rapidly simulated, or the simulation could guide the design of treatments. Eventually, if the simulation becomes as accurate as SPICE can be today, it would be possible to go directly from the design of a treatment to its administration, secure in the knowledge that it is unlikely to cause problems. [1] https://en.wikipedia.org/wiki/SPICE https://en.wikipedia.org/wiki/SPICE
  - exmadscientist 4y ago
    Why do you believe a quantum computer can actually solve that problem? The whole point of the article is that quantum computers are not and can never be general-purpose computers. And something with as many inputs as "simulate the human body" seems like the exact opposite of what you can encode in qubits, evolve as a state vector, and usefully read out.
    - cycomanic 4y ago
      The point is that for these sort of simulations you don't want a general purpose computer. Ideally you have a "equivalent" of the quantum mechanical Hamiltonian that you can manipulate/design and read effects out from. Now to simulate the human body probably requires a prohibitively large number of qubits, however for many very useful things you don't need that.
      - exmadscientist 4y ago

marcosdumay 4y ago

Only people that deal with stuff created by chemical reactions have a need for quantum computers... None else.

mtlmtlmtlmtl 4y ago

I wonder if quantum computing is just a mirage that results from looking too much at the time complexity of quantum algorithms versus the cost in qubits, which are still wildly expensive. Maybe qubits will just never scale to the number of qubits needed to meaningfully outperform classical computers.

dataflow 4y ago
Yeah lots of people think decoherence will prevent QC from becoming practically useful. Some researchers seem to think differently, but I never found an explanation for why I should be as optimistic as they are.
- ramraj07 4y ago
  Which side is Scott Aaranson on? Just curious.
  - dataflow 4y ago
    The only link I have handy is this comment from him in 2019 [1]. I feel like I've seen more in the past, but I can't find them now. [1] https://scottaaronson.blog/?p=4372from=timeline#comment-1822765 https://scottaaronson.blog/?p=4372from=timeline#comment-1822...
  - mtlmtlmtlmtl 4y ago
    Doesn't he work on QC from the theory side? I assume he has at least some faith if he's spending his time on it. He's on Sean Carroll's podcast talking about this stuff but I can't remember what stance he took on it. I know Stephen Wolfram isn't too excited. But I believe his issue was more that algorithms end with "and then a measurement happens", which might be quite tricky and possibly even cancel out any potential gains. Not sure about the details of that, but it makes superficial sense given the nature of measurement in QM.
    - bowsamic 4y ago
      Why would quantum measurement be a problem in any way? Obviously measurement doesn’t destroy quantum effects, else we would not be able to see QM in the first place. Obviously you have to factor in what the measurement does to your quantum computer, but that’s obviously just part of your design in the first place

glitchc 4y ago

Reminds me of this: https://ieeexplore.ieee.org/document/4051190 https://ieeexplore.ieee.org/document/4051190 Back then a digital computer couldn’t hold a candle to an analog one and processed only a few bits at a time. It was slow and imprecise. Look at where we are now. A general quantum computer is a fundamentally different kind of computer. Those who cannot imagine what can be done with one lack the imagination to understand foundationally new technology and are unable to invent their own.

tjr225 4y ago
It seems that nobody on the planet is able to invent their own quantum computer.
- chasil 4y ago
  Actually, a 65-qubit quantum computer has been created. "IBM's current largest quantum computer, revealed this month, contains 65 qubits." https://www.science.org/content/article/ibm-promises-1000-qubit-quantum-computer-milestone-2023 https://www.science.org/content/article/ibm-promises-1000-qu...
  - brokensegue 4y ago
    I'm not an expert but I think because of the error correction mechanisms the effective number of quibits is smaller than that
    - _8091149529 4y ago
      No quantum computing platform today has meaningful error correction. What you can get, in some cases, is limited error detection based on the outcome of the question computation, if it's built into your specific algorithm.
  - sgt101 4y ago
    There is a big difference between a practical QC and the QC we have now. 65bits isn't practical for any known real problem but ask also how long it takes to boot it, how many cycles it can execute per run and how many runs it can do per day (or week). These thing are not like your laptop, they are more like particle accelerators.

cc101 4y ago

I remember when the Commodore 64 came out. "64K RAM?", I thought, "What could anyone do with so much RAM?" Power to do something new always generates new things to do with it.

jchw 4y ago
You're only following the winners, but computer science has also had a lot of flops, too. Time will tell if quantum computers is one of those, but it sure isn't looking great so far.
- reacweb 4y ago
  At that time QL Sinclair was a loser. A good computer that never got programs. It was the computer of Lius Torwalds and the reason he had to write himself programs. Without QL Sinclair, we may never had Linux. At my work, I was present when the research on ASAS (https://skybrary.aero/articles/airborne-separation-assurance-systems-asas https://skybrary.aero/articles/airborne-separation-assurance...) led to the idea of PMS (https://www.eurocontrol.int/sites/default/files/2021-05/eurocontrol-point-merge-guide-v1-4.pdf https://www.eurocontrol.int/sites/default/files/2021-05/euro...). Never underestimate serendipity
  - jchw 4y ago
    While that's a neat story, I'm not sure if it has a lot to do with the practical applicability of quantum computing. I didn't mean to single out Commodore or their CBM64, I really mean to say that there are plenty of examples of entire technologies that were hyped and then flopped, not just market competitors in a given technology that is already mostly proven.
  - einpoklum 4y ago
    > we may never [have] had Linux. Oh, come on. Linux was a clone of MINIX with a GPL license. If Linus had not written it, somebody else would have; and at worst (if that is worse), we would have all been running FreeBSD now.

bpodgursky 4y ago

I think there is a world market for about five quantum computers.

O__________O 4y ago

Are quantum computers being used in economically significant ways that only are possible with quantum computers yet? If so, what is the best example? Last time I checked few years ago, my understanding was the answer was still no; specifically, believe I asked Scott Aaronson as a follow up question to a talk he gave: https://www.scottaaronson.com/ https://www.scottaaronson.com/

cycomanic 4y ago
The short answer is no, I think Ising machines are much closer or even there for specific problems. They are somewhat similar to quantum computers, but entirely classical (Dwave was shown to be equivalent to an Ising machine IIRC).
bowsamic 4y ago
No

blueprint 4y ago

No, per Susskind, we need entangled quantum computers of sufficient size to do wormhole experiments!

LeegleechN 4y ago

He's not wrong about the narrow algorithmic use cases (so far), but he's completely missing the utility for simulation of quantum phenomena (chemistry, microbiology, materials science). That use case alone completely justifies investing into them even if you don't care about advancing science.

bowsamic 4y ago
Yeah the problem is in the name and the marketing. People think it is meant to replace normal computers, but that is totally wrong. The simulation use cases as well as probing fundamental physics are far more immediate and exciting
- baby 4y ago
  And there’s all the crypto FUD that quantum computers will scale enough to break crypto algorithms
  - hnfong 4y ago
    It hasn't happened yet or won't happen any time soon, but if there's a chance RSA is going to be broken I'd rather be aware of the possibility 10 years earlier than 10 days after...
credit_guy 4y ago
Out of curiosity, how many qubits would you need to simulate the molecule of water?
- tokamak 4y ago
  Can QC simulate that?
  - ki_ 4y ago
    QC cant do anything, it has no use cases. And that won't change. Except if you want to generate random numbers. that it can do.

tho2u43234 4y ago

That's probably because "real" quantum computing today can't even factor 4-bit numbers. The coherent-bits are really not scaling fast enough (and this is to be expected given their entanglement IMO) for anyone to really care other than snazzy startups scamming investors of their money.

johnebgd 4y ago
Yeah, quantum computing is still basically experimental…
- pyinstallwoes 4y ago
  Experimental, non-physical, completely theoretical. Yep.

yshvrdhn 4y ago

I would argue its similar to how we thought of computers when they first came out ?

feliyur 4y ago

From my limited understanding, a quantum computer performs computations over probability distributions, rather than over numerical values. Performing precise computations over probability distributions is a serious problem in many domains - physical simulations are just one. Another example is that could allow much more efficient and precise data fusion, and as a result - a leap in AI abilities, across domains where AI is used.

yccs27 4y ago
Unfortunately, even though a quantum computer "manipulates wavefunctions", you can still only measure the outcome once. The magic has to happen somewhere in between state preparation and measurement. It's more like a computer with an inbuilt RNG - but if you can reach the same result via multiple execution paths, the probabilities don't just add, but they can interfere like in-phase/out-of-phase oscillatins.

hit8run 4y ago

So did the need for computers before the revolution started. It’s just a matter of time

vanviegen 4y ago
> It’s just a matter of time Why? Not every new tech solves a problem people actually have..
morelisp 4y ago
"Computers" are named after the teams of humans previously tasked with doing what they now do, a relatively common job in the first half of the 20th century and even irregularly earlier. The need was clear.

seydor 4y ago

Quantum computers are a part of quantum mechanics that s more of a curiosity than something to be engineered at scale. There's so much more to explore in quantum mechanics outside computation that is not receiving commensurate funding. I guess it's because "computing" is what BigTech (who has the money to fund it) understands

throwawayffffas 4y ago
I was under the impression that it was because quantum computers would make the simulation of quantum mechanics significantly faster as well.

lizardactivist 4y ago

Is there any demonstration of practical, usable QC yet? I'm thinking of some kind of common computational work, with a clearly defined input and verified output, shown to be carried out at least an order of magnitude faster than our conventional computers.

tokamak 4y ago
Obviously not

nabla9 4y ago

Normal computers would have suffered the same fate if they were only good for scientific calculations. Computer revolution was funded by demand in business, gaming and automation. It's the cash flow that funds long term R&D. Not potential benefit. There is no such demand for quantum computers. Everyday problems have too small complexity for them to be useful even if algorithm exists. I suspect that computational biochemistry will have funders from drug firms and companies doing materials science to keep funding the research for quantum computing, but the total sum will not be billions per year like it was in computer revolution.

varjag 4y ago
Classical computers appeared and for the first decade existed purely because of scientific demand. Gaming and business were secondary effects.
- nabla9 4y ago
  Scientific demand is enough to start something, not sustain huge annual investments. Global supercomputer market is roughly $6-7 billion. Nvidia, AMD together spend more into R&D than the whole market has sales. Scientific use is minuscule compared to business and entertainment needs. Quantum computers research gets millions or maybe few tens of millions funding. That's not enough.

budlebee 4y ago

It feels like I'm reading an article on Netscape browser that says, "AI is still useless."

derpherpsson 4y ago

If you are able of imagining the future, and capable of logical coherent thoughts, the statement "the need for quantum computers remains small" is just... damn narrow-minded and perhaps just plain stupid. If you can shave off a factor n in O(n^3) then O-B-V-I-O-U-S-L-Y it will change the world. If you don't see the obviousness in this, then why are you working with computers? Before you hate on me, did you even google "quantum computer"? Did you read the introduction section of the Wikipedia article?

trention 4y ago
The proportion of comp sci tasks that have practical importance for which a quantum computer can shave off a factor of ~000s seems to be sufficiently small to doubt it will "change the world".
morelisp 4y ago
I've read the introduction (and, uh, a lot more). What specific algorithms do you have in mind where quantum supremacy seems a) likely (or even possible) and b) enough of an improvement to be world-changing?

xwdv 4y ago

Don’t we need quantum computers to crack cryptography in reasonable time? Could be useful for surveillance or espionage purposes.

alpineidyll3 4y ago

If error correction can be made to work they would revolutionize human life by allowing the microscopic world to be predictable. The recent result about error correction in surface codes from the Google group is encouraging, but still several OOMs away from anything meaningful.

wintorez 4y ago

"I think there is a world market for maybe five computers." -- Thomas Watson, president of IBM, 1943

rbanffy 4y ago
I came here to say precisely that. We don’t know yet what they could be useful for because we don’t have a single one that’s as capable as conventional computers were in 1943.
rbanffy 4y ago
“Apple is already dead.” Nathan Myhrvold, former Microsoft CTO, 1997
rbanffy 4y ago
“There is no reason anyone would want a computer in their home.” Ken Olsen, founder of Digital Equipment Corporation, 1977

abeppu 4y ago

He sort of glosses by the need to upgrade from current cryptographic algorithms. But I wonder if in 20-30 years, we'll look back on the bad timing of having designed blockchains before post-quantum cryptography was on solid footing. Even if there are few problems where quantum computers have a clear advantage, it seems at least unfortunate that a lot of people spent a lot of time and resources building up "value" explicitly protected by those problems ... and decentralizing them in a way that makes upgrades challenging. We like to imagine that quantum computers will be creating value for society by doing simulations about cutting-edge scientific problems. What if it just lets rich companies impersonate long-dead bitcoin whales?

tromp 4y ago
I consider the odds of having quantum computers able to break discrete log within 3 decades to be rather minute. The challenges involved seem way larger than for something like making nuclear fusion commercially viable. I also have a very hard time believing that 1) physical reality supports computing with a superposition of 2^{256} states each with an accurate amplitude of magnitude 2^{-128}, and 2) that we can engineer systems preserving such accuracies.
- abeppu 4y ago
  Care to shed more light on your intuitions? I get that the engineering challenges are hard (or we'd have figured it out by now). And everyone seems pretty bad at predicting how long it will take for us to build something fundamentally new. But from the physical impossibility side, what would have to be true/what would we learn if we discovered that physical reality _doesn't_ support quantum computation with a large number of qubits and sufficient accuracy? I did do a course which included some quantum computation material and the professor highlighted that it wasn't actually demonstrated whether nature would be so "extravagant" ... but I haven't heard anyone describe what the universe would need to be like to both support the quantum phenomena that we've already studied and demonstrated, but to disallow some larger/more complex arrangements of what seem to be the same principles.