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Optical Computer Prototype

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Re: Optical Computer Prototype

#11

Post by Veratyr »

mentos wrote: post #4

If photons and electrons travel at the same speed am I right in thinking that the benefits of optical computing would be limited to parallel processing?

Might be worth reading up to understand how much the speed Electrons can move at matters: https://en.wikipedia.org/wiki/Speed_of_electricity

TL;DR: "The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic wave, not the movement of electrons. Electromagnetic wave propagation is fast and depends on the dielectric constant of the material. In a vacuum the wave travels at the speed of light and almost that fast in air."

Re: Optical Computer Prototype

#12

Post by ajuc »

dogma1138 wrote: post #7
mentos wrote: post #4

If photons and electrons travel at the same speed am I right in thinking that the benefits of optical computing would be limited to parallel processing?

Electrons have mass they can't move at the speed of light. Photons also have other nice properties such as wavelength which open a whole suit of possibilities e.g. like having a logic gate which can operate in different mods based on the wavelength and polarization of the light. While this is technically possible with electronics as well by setting a different voltage limit it's much more effective with photonic comp…

Information we move around using electrons moves much faster than any single electron - because electrostatic field changes move at speed of light obviously, so the electrons at the end of wire start moving as soon as the electrostatic field change gets to it.

You don't have to wait with processing for the electron from the beggining of the wire to get to the end?

So, the difference between photons and electrons speed as measured by the time it takes electronic and optical signal to move through the same distance - is insignificant.

Re: Optical Computer Prototype

#13

Post by dogma1138 »

mentos wrote: post #10
dogma1138 wrote: post #7

Earlier quoted context omitted.

Electrons have mass they can't move at the speed of light. Photons also have other nice properties such as wavelength which open a whole suit of possibilities e.g. like having a logic gate which can operate in different mods based on the wavelength and polarization of the light. While this is technically possible with electronics as well by setting a different voltage limit it's much more effective with photonic comp…

What fraction of the speed of light are electrons moving at in the most advanced silicon chip we have? Trying to understand how much speed is left on the table for us to pick up in serial processing?

It's not that easy to define because were talking about semi-conductors after all;)

They don't move at a constant speed like say in a conductor (which isn't the case either because electric field causes resistance e.g. eddy currents, but lets say a super-conductor)

You have quite a few concepts with semiconductors primarily saturation velocity (which in most cases is the peak velocity, but not necessarily attained in actual operation) which is also affected by the drift velocity due to any electric fields in your components.

https://en.wikipedia.org/wiki/Saturation_velocity

Light speed in vacuum is 29979245800 cm/s Saturation velocity in Si based SC is 10000000 cm/s

So there's quite a bit of difference there ;)

Re: Optical Computer Prototype

#14

Post by dogma1138 »

Veratyr wrote: post #11
mentos wrote: post #4

If photons and electrons travel at the same speed am I right in thinking that the benefits of optical computing would be limited to parallel processing?

Might be worth reading up to understand how much the speed Electrons can move at matters: https://en.wikipedia.org/wiki/Speed_of_electricity TL;DR: "The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic wave, not the movement of electrons. Electromagnetic wave propagation is fast and depends on the dielectric constant of the material. In a vacuum the wave travels at the…

While that's true for simple conductive cables that's not the case for semi-conductors. https://en.wikipedia.org/wiki/Saturation_velocity

Especially since there are some semi-conductors which actually require you to move electrons, like e.g. flash memory ;)

Re: Optical Computer Prototype

#15

Post by dogma1138 »

ajuc wrote: post #12
dogma1138 wrote: post #7

Earlier quoted context omitted.

Electrons have mass they can't move at the speed of light. Photons also have other nice properties such as wavelength which open a whole suit of possibilities e.g. like having a logic gate which can operate in different mods based on the wavelength and polarization of the light. While this is technically possible with electronics as well by setting a different voltage limit it's much more effective with photonic comp…

Information we move around using electrons moves much faster than any single electron - because electrostatic field changes move at speed of light obviously, so the electrons at the end of wire start moving as soon as the electrostatic field change gets to it. You don't have to wait with processing for the electron from the beggining of the wire to get to the end? So, the difference between photons and electrons spee…

I didn't say that we need to move electrons (although we do for some things like Flash Memory), but you are confusing simple wave propagation in conductors with electron mobility in semiconductors which is quite a bit more complicated.

You also need to remember that when we talking about waves then the wavelength ties directly to your data throughput, and with electrons the wavelength in conductors at say a frequency of 1GHZ is still around 3 kilometers, visible light has much much shorter wavelengths which allows you to pass more data per given amount of time.

Re: Optical Computer Prototype

#16

Post by imaginenore »

mechagodzilla wrote: post #9

This appears to basically be an analog optical computer - it inputs some 2D data using an LCD, puts it through a bunch of optical transforms, and then captures the output with a camera. This probably does have some kind of obscure use cases where it makes sense, but it's very hard to compete with modern silicon for raw compute using some kind of hybrid method - moving data in and out of the optical part is just painf…

Today's computers are very slow. Try modeling something complex, let's say 1 billion water molecules interacting. Then realize that 1 billion molecules is orders of orders of magnitude far from modeling a cup of water.

Re: Optical Computer Prototype

#18

Post by dang »

sounds wrote: post #2

I think the submission here on HN has overdone it on the title. It doesn't compute "flops" like a traditional computer. The relevant text from the article: "The prototype achieves a processing speed equivalent to 320 Gflops and it is incredibly energy efficient as it uses low-powered, cost effective components." I am as interested as anybody in switching out for photons instead of electrons/holes. But please use the…

Ok, we took "32O Gflop" out of the title. If anyone suggests a better title we can change it again.

Re: Optical Computer Prototype

#19

Post by jjoonathan »

imaginenore wrote: post #16
mechagodzilla wrote: post #9

This appears to basically be an analog optical computer - it inputs some 2D data using an LCD, puts it through a bunch of optical transforms, and then captures the output with a camera. This probably does have some kind of obscure use cases where it makes sense, but it's very hard to compete with modern silicon for raw compute using some kind of hybrid method - moving data in and out of the optical part is just painf…

Today's computers are very slow. Try modeling something complex, let's say 1 billion water molecules interacting. Then realize that 1 billion molecules is orders of orders of magnitude far from modeling a cup of water.

> 1 billion molecules is orders of orders of magnitude far

Understatement. There are 50 trillion atoms in a cell, 50 trillion cells in a human body (give or take an order of magnitude or two for definitions and caveats). Furthermore, big swaths of chemistry/biochemistry are inherently quantum mechanical (classical mech + E&M doesn't explain why molecules snap into little geometric shapes, let alone how those shapes interact) which has god-awful asymptotic complexity on account of the "present state" of the system (wavefunction) being a probability for each possible configuration of the system rather than a description of a single configuration.

A purpose-built silicon supercomputer will struggle to simulate a single small protein using classical-mechanics approximations for a millisecond (and there are millions of those per cell and trillions of cells per body). There's a lot of room for improvement.

Re: Optical Computer Prototype

#20

Post by mentos »

dogma1138 wrote: post #13
mentos wrote: post #10

Earlier quoted context omitted.

What fraction of the speed of light are electrons moving at in the most advanced silicon chip we have? Trying to understand how much speed is left on the table for us to pick up in serial processing?

It's not that easy to define because were talking about semi-conductors after all;) They don't move at a constant speed like say in a conductor (which isn't the case either because electric field causes resistance e.g. eddy currents, but lets say a super-conductor) You have quite a few concepts with semiconductors primarily saturation velocity (which in most cases is the peak velocity, but not necessarily attained in…

So does this imply an opportunity to improve computing speed by 2997?
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