Earlier quoted context omitted.
How could he? there were no cell phones.
Yes, that was the point of the parent comment.
Thanks for reaffirming Poe's law. I was amused by how 'cell phone' was taken as a given, when talking about a CCD sensor.
Google Quantum AI
161–170 of 210 posts
Re: Google Quantum AI
#162Earlier quoted context omitted.
>They are extremely useful and do things that digital computers cannot do. But that is false. A classical computer can simulate a quantum computer. Performance is the difference, not inherent ability. >The cynicism in this thread is crazy The cynicism stems from people telling others that practical quantum computers will change the world for at least a decade. Even the URL invokes deep cynicism in me, as it randomly…
> The cynicism stems from people telling others that practical quantum computers will change the world for at least a decade. Practical quantum computers will change the world (break RSA 2048). The question is "when". The people who have a timeline of ~10 years instead of decades contribute to what we in our community call "Quantum hype" and it's very much frowned upon by most of the members in the community. > combi…
How would breaking RSA change the world?
Perhaps via some practical (non-crypto) application of factoring large numbers?
Re: Google Quantum AI
#163The fact this prize exists is admitting that no one has figured out a use for quantum computers. I have heard this mentioned several times in the last decade or so : "The only thing a quantum computer definitively does better than a classical computer is simulating a quantum computer." Whether this capability is useful is up in the air. Note that in practice, classical computers are going to be better at factoring nu…
Ther are plenty of well documented uses for quantum computers, the hardware is just too nascent to fully accommodate them. The most powerful quantum computers today still only have just over 1,000 qbits.
Assuming what the public knows about is the state of the art, of course, which I doubt is a good assumption to make. I'm sure major governments have been funneling billions for years into secret projects to be the first to be able to break the (non-post-quantum) communications of everyone else.
Re: Google Quantum AI
#164Earlier quoted context omitted.
Einstein did not have GPS in mind when he was developing his theories of relativity.
The theory of relativity does not in any way enable GPS. GPS is subject to (some) relativistic effects, but that is merely a source of bias, which could be corrected for with just an experience-based correction factor even if we did not understand relativity. If relativity did not exist as a physical concept, GPS would be easier, not harder or impossible. (I guess this misconception comes from xkcd in some form?) A p…
A more relevant example would be that Einstein did not predict how to make a laser when he discovered the theory of the stimulated emission of radiation (the "SER" in "LASER").
The photoelectric effect had been well known for decades, Einstein has just given a good explanation of its behavior that was already known from experiments. It would have been equally easy for the designers of the first video camera vacuum tubes, which were used in the early television, to design them based only on the known experimental laws, ignoring Einstein's explanation.
On the other hand, the formulae of the stimulated emission of radiation, complementing the previously known phenomena of absorption and spontaneous emission, were something new, published for the first time by Einstein in 1917. They are the most original part of Einstein's work, together with the general relativity, but their practical applications are immensely more important for now than the applications of general relativity, which are limited to extremely small corrections in the results of some measurements with very high resolutions.
The inventions of the masers and lasers after WWII would not have been possible without knowing Einstein's theory of radiation.
Re: Google Quantum AI
#165The fact this prize exists is admitting that no one has figured out a use for quantum computers. I have heard this mentioned several times in the last decade or so : "The only thing a quantum computer definitively does better than a classical computer is simulating a quantum computer." Whether this capability is useful is up in the air. Note that in practice, classical computers are going to be better at factoring nu…
> no one has figured out a use for quantum computers. It is my understanding that a use is very straightforward: quickly solving problems in the Big(O) Factorial Class (n!). I could be misunderstanding QC though.
Yes, you are. Quantum computers are only believed to be faster than classical computers for a handful of very specific problems. And even those are not 100% proven (we don't have a proof that a faster classical algorithm doesn't exist for any of them, except Grover's search, which is only a quadratic speedup, not an exponential one).
Re: Google Quantum AI
#166Earlier quoted context omitted.
Yes, that was the point of the parent comment.
Thanks for reaffirming Poe's law. I was amused by how 'cell phone' was taken as a given, when talking about a CCD sensor.
I believe that most, if not all, cell phone cameras have cheaper CMOS sensors, not CCD sensors (which have a lower image noise, but they need a more expensive manufacturing process, less compatible with modern digital logic and more similar to the manufacturing processes used for DRAM).
AFAIK the CCD technology continues to be used only in large-area expensive sensors inside some professional video cameras, in applications like astronomy, microscopy, medical imaging and so on.
Re: Google Quantum AI
#167Earlier quoted context omitted.
It is still open whether we can build quantum computers with sufficiently low noise to run Shor‘s algorithm.
> It is still open whether we can build quantum computers with sufficiently low noise to run Shor‘s algorithm. This statement should delimit between theory and experiment. Theoretically, the question of building a quantum computer with low enough noise to run Shor's has been solved. In fact it was solved by Shor himself in the 1990s: https://arxiv.org/abs/quant-ph/9605011 . Experimentally, we are just getting started…
That paper of Shor just shows how a quantum computer with a large number of bad qubits can be the equivalent of a quantum computer with a small number of good qubits.
The paper does not prove anything about the upper limit for the number of bad qubits that are physically realisable.
There are doubts that this upper limit, which is unknown yet, is high enough for most practical applications.
Re: Google Quantum AI
#168Earlier quoted context omitted.
Thanks for reaffirming Poe's law. I was amused by how 'cell phone' was taken as a given, when talking about a CCD sensor.
I believe that most, if not all, cell phone cameras have cheaper CMOS sensors, not CCD sensors (which have a lower image noise, but they need a more expensive manufacturing process, less compatible with modern digital logic and more similar to the manufacturing processes used for DRAM). AFAIK the CCD technology continues to be used only in large-area expensive sensors inside some professional video cameras, in applic…
Quite true even full-frame DSLRs typically use CMOS sensors for some time now.
CCD was the first thing that came to mind as 'charge' is right in the name.
Out of curiosity, looked up invention dates for CCD 1969 and CMOS 1963 and CMOS sensor 1993 (quite a gap). I was playing with DRAM light sensitivity in the lab in the late 80's. I'm guessing CMOS had too much noise to be useful for a long while or something.
Re: Google Quantum AI
#169Earlier quoted context omitted.
No that’s not how it works, quantum mechanics cannot be simulated efficiently on a classical computer, the state space grows exponentially with the number of degrees of freedom, every degree has relative phases to every other degree even when only looking at pure states, that’s why even the largest super computers cannot simulate more than 50 quantum degrees of freedom currently (see quantum supremacy).
I’m not claiming quantum mechanics can be efficiently simulated on a normal computer. I’m questioning whether arbitrary quantum mechanics systems can be effectively simulated by a quantum computer.
I have not seen any description of a general-purpose programmable quantum computer, which could simulate an arbitrary quantum system, like a digital computer.
All the examples given that I have seen were for making a hardwired simulator for a concrete quantum system, e.g. some chemical macromolecule of interest, to be used much in the same way as analog computers were used in the past for simulating systems governed by differential equations too complex to be simulated by the early digital computers in an acceptable time.
Re: Google Quantum AI
#170Earlier quoted context omitted.
We know how to simulate it, but we can't do it. Those equations though require too much computation if you solve them with any known classical algorithm.
This is completely wrong. My laptop can solve the equations in fractions of a second. I believe that with some optimizations it should be trivial to do the calculations on a 1960s mainframe.
That is not true.
You can solve such equations in fractions of a second only for very low precisions, much lower than the precision that can be reached in measurements.
For higher precision in quantum electrodynamics computations, you need to include an exponentially increasing number of terms in the equations, which come from higher order loops that are neglected when doing low precision computations.
When computing the energy levels of the spectrum of a hydrogen atom with the same precision as the experimental results (which exceed by a lot the precision of FP64 numbers, so you need to use an extended precision arithmetic library, not simple hardware instructions), you need either a very long time or a supercomputer.
I am not sure how much faster can that be done today, e.g. by using a GPU cluster, but some years ago it was not unusual for the comparisons between experiments and quantum electrodynamics to take some months (but I presume that the physicists doing the computations where not experts in optimizations, so perhaps it would have been possible to accelerate the computations by some factor).