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Gaaah, please stop advertising optical computers as the technology that will overcome Moore's law. It makes no effing sense. Wavelength of the light emitted by

Gaaah, please stop advertising optical computers as the technology that will overcome Moore's law. It makes no effing sense. Wavelength of the light emitted by these devices: ~4000nm Latest generation commodity CPU transistor structure size: 7nm Add to that that photons really don't like being trapped; you essentially need a delay line and optical amplifier to hold them indefinitely (that's essentially the core technology my whole PhD thesis centers around), it makes them a really impractical thing to store bits with. Things with a rest mass can be stored easily, though. Things like, say, electrons!

dr_dshiv 6y ago
I like to think that comments like this make me smarter with 10x efficiency. In this case, the pattern is: 1. Identify and refute common conception 2. Compare easily understood numbers 3. Assert basis of knowledge 4. Introduce a clear, tangible model for alternative thinking 5. Appropriate use of emotional resonance to capture and maintain attention
- karkisuni 6y ago
  Five Easy Steps to Becoming a 10x Commenter!
  - kevin_thibedeau 6y ago
    There's no profit in taking five steps.
    - deleted 6y ago
      [deleted]
dannypgh 6y ago
It's definitely not a continuation of Moore's law as it has nothing to do with transistor density, but it may mean that the performance people expect from computers - which is why people are usually talking about Moore's law - may continue increasing. I don't see how the wavelength is comparable to transistor size because as you switch to the optical realm, the benefit of information propagation at speeds near c (or c, if you're pulling a vacuum) means physical size doesn't matter as much. At 4Ghz you can move information 7.5cm in one cycle, and that's a pretty large distance compared to any integrated circuit I've ever seen. Why is storage necessary? If you can move bits to optical gates and get a result back it seems to me like you can work around the fact that, in an electrical system, capacitance and heat (due to density achieved in the quest for minimizing capacitance) start to limit the computation you can do.
- lopsidedBrain 6y ago
  > Why is storage necessary? Have you ever tried wiring any non-trivial logic without flip-flops? Say, a simple signal routing layer. Even the most basic bits of logic becomes much less efficient to downright impossible without storage.
  - twomoretime 6y ago
    You can use hybrid systems where, say, memory is conventional RAM but computation (maybe full cpu or submodule like apu) is done with photons. You can probably perform large numbers of concurrent operations by taking advantage of the wavelike properties of photons.
    - ip26 6y ago
      You can wave pipeline electrons too. It just very rapidly becomes an impossible design problem as the complexity of your design increases (and as the variation grows in significance with node shrinks)
- gibybo 6y ago
  I thought electric charge in conductors already moved very close to C? https://en.wikipedia.org/wiki/Speed_of_electricity https://en.wikipedia.org/wiki/Speed_of_electricity
  - mcnamaratw 6y ago
    Exactly. If we're pedantic about it, a charge signal moves at the speed of light. But the signals are what computers use.
  - whatshisface 6y ago
    Only if you consider 70% or so to be close. There's some room for improvement over copper wires. Now, if there are any physicists here who want to jump in, I have a question about that. I heard waveguides are dispersive, would sending pulses of light through tiny channels slow it down as well?
ehonda 6y ago
In the article, they do say that the use will be in transmitting data from a processor to different components farther away from it, like RAM or sensors on a car.
miscPerson 6y ago
This is a tangent, but could you point me towards delay line + amplifier literature? Would be much appreciated.
- jacquesm 6y ago
  That's how the very first computers worked: https://www.computerhistory.org/storageengine/edsac-computer-employs-delay-line-storage/ https://www.computerhistory.org/storageengine/edsac-computer... Not optical, but piezo electrical, usually with a crystal or air as the medium instead of mercury. Optical is much the same principle, a feedback loop incorporating the delay line, so the same bits get re-injected over and over again and can only be read out at specific points in time.
  - hinkley 6y ago
    I thought the mercury delay lines were the craziest thing I’d heard about in computer evolution until I learned about using a cathode ray tube as memory.
    - jacquesm 6y ago
      In a way that is a delay line too, the phosphor decay time allows you to read out the bits a bit later than you put them in. The big advantage is that it is theoretically random access.
  - miscPerson 6y ago
    Yep, and I was looking for something applied. Like most things, the concept is much simpler than making one work — and I was hoping I could find some papers on the applied side of photon delay lines. (Since OP commented it was related to his/her PhD.)
Zenst 6y ago
How do electronics compare to photonics thermal radiation wise? Though as always with electrical based electronics - superconductors are room temperature are always heralded to be the big jump in many things. As always, soon, much like photonics or let alone the ability to easily design and implement asynchronous circuits, let alone CPU's. Though I do wonder what other industries have the equivalent to moore's law driving them in both advancements and marketing? I'm kinda drawing a blank of anything that has any progress metric defined. Though hopefully somebody else knows of something comparable in another form of production/business.
andrewflnr 6y ago
The article specifically proposes using light for transmission between components (not storage), with the efficiency benefit of multiplexing (albeit not mentioned by name). As I read it they're talking nanoscale fiber optics, not optical transistors and memory. This sounds pretty reasonable to me, and your comment seems to not address it at all.
jl2718 6y ago
High-bandwidth plasmon resonator waveguides. This would allow multiple datapaths on a single 'wire'. Fermions are great for logic and storage, but not for comms. Currently we use ~90% of chip power moving around data. We need to use bosons for this. We need to make them in silicon, and reduce the waveguide dimension. That's where this is going.
kelsolaar 6y ago
I will be pedantic but there is no light at 4000nm. Light is by definition the radiation that is considered from the point of view of its ability to excite the human visual system (HVS). The HVS sensitivity, as given in ASTM E308-15 practise, is in range [360, 780]nm.
- datenwolf 6y ago
  Well, the semantics of what constitutes light and what not are a bit murky. CO2 lasers are still considered LIGHT amplification by stimulated emission of radiation. CO2 lasers operate at ~10000nm. In the optics community we usually consider everything we can manipulate with refractive optics as "light" – and yes, I am fully aware that this goes down well into what's considered microwave radio. My personal cutoff for where optics begins is, where I no longer can use an antenna that is part of a resonant _circuit_ to emit / receive the radiation, and have to resort to quantum mechanical state transitions.

dr_dshiv 6y ago

I like to think that comments like this make me smarter with 10x efficiency. In this case, the pattern is: 1. Identify and refute common conception 2. Compare easily understood numbers 3. Assert basis of knowledge 4. Introduce a clear, tangible model for alternative thinking 5. Appropriate use of emotional resonance to capture and maintain attention

karkisuni 6y ago
Five Easy Steps to Becoming a 10x Commenter!
- kevin_thibedeau 6y ago
  There's no profit in taking five steps.
  - deleted 6y ago
    [deleted]

dannypgh 6y ago

It's definitely not a continuation of Moore's law as it has nothing to do with transistor density, but it may mean that the performance people expect from computers - which is why people are usually talking about Moore's law - may continue increasing. I don't see how the wavelength is comparable to transistor size because as you switch to the optical realm, the benefit of information propagation at speeds near c (or c, if you're pulling a vacuum) means physical size doesn't matter as much. At 4Ghz you can move information 7.5cm in one cycle, and that's a pretty large distance compared to any integrated circuit I've ever seen. Why is storage necessary? If you can move bits to optical gates and get a result back it seems to me like you can work around the fact that, in an electrical system, capacitance and heat (due to density achieved in the quest for minimizing capacitance) start to limit the computation you can do.

lopsidedBrain 6y ago
> Why is storage necessary? Have you ever tried wiring any non-trivial logic without flip-flops? Say, a simple signal routing layer. Even the most basic bits of logic becomes much less efficient to downright impossible without storage.
- twomoretime 6y ago
  You can use hybrid systems where, say, memory is conventional RAM but computation (maybe full cpu or submodule like apu) is done with photons. You can probably perform large numbers of concurrent operations by taking advantage of the wavelike properties of photons.
  - ip26 6y ago
    You can wave pipeline electrons too. It just very rapidly becomes an impossible design problem as the complexity of your design increases (and as the variation grows in significance with node shrinks)
gibybo 6y ago
I thought electric charge in conductors already moved very close to C? https://en.wikipedia.org/wiki/Speed_of_electricity https://en.wikipedia.org/wiki/Speed_of_electricity
- mcnamaratw 6y ago
  Exactly. If we're pedantic about it, a charge signal moves at the speed of light. But the signals are what computers use.
- whatshisface 6y ago
  Only if you consider 70% or so to be close. There's some room for improvement over copper wires. Now, if there are any physicists here who want to jump in, I have a question about that. I heard waveguides are dispersive, would sending pulses of light through tiny channels slow it down as well?

ehonda 6y ago

In the article, they do say that the use will be in transmitting data from a processor to different components farther away from it, like RAM or sensors on a car.

miscPerson 6y ago

This is a tangent, but could you point me towards delay line + amplifier literature? Would be much appreciated.

jacquesm 6y ago
That's how the very first computers worked: https://www.computerhistory.org/storageengine/edsac-computer-employs-delay-line-storage/ https://www.computerhistory.org/storageengine/edsac-computer... Not optical, but piezo electrical, usually with a crystal or air as the medium instead of mercury. Optical is much the same principle, a feedback loop incorporating the delay line, so the same bits get re-injected over and over again and can only be read out at specific points in time.
- hinkley 6y ago
  I thought the mercury delay lines were the craziest thing I’d heard about in computer evolution until I learned about using a cathode ray tube as memory.
  - jacquesm 6y ago
    In a way that is a delay line too, the phosphor decay time allows you to read out the bits a bit later than you put them in. The big advantage is that it is theoretically random access.
- miscPerson 6y ago
  Yep, and I was looking for something applied. Like most things, the concept is much simpler than making one work — and I was hoping I could find some papers on the applied side of photon delay lines. (Since OP commented it was related to his/her PhD.)

Zenst 6y ago

How do electronics compare to photonics thermal radiation wise? Though as always with electrical based electronics - superconductors are room temperature are always heralded to be the big jump in many things. As always, soon, much like photonics or let alone the ability to easily design and implement asynchronous circuits, let alone CPU's. Though I do wonder what other industries have the equivalent to moore's law driving them in both advancements and marketing? I'm kinda drawing a blank of anything that has any progress metric defined. Though hopefully somebody else knows of something comparable in another form of production/business.

andrewflnr 6y ago

The article specifically proposes using light for transmission between components (not storage), with the efficiency benefit of multiplexing (albeit not mentioned by name). As I read it they're talking nanoscale fiber optics, not optical transistors and memory. This sounds pretty reasonable to me, and your comment seems to not address it at all.

jl2718 6y ago

High-bandwidth plasmon resonator waveguides. This would allow multiple datapaths on a single 'wire'. Fermions are great for logic and storage, but not for comms. Currently we use ~90% of chip power moving around data. We need to use bosons for this. We need to make them in silicon, and reduce the waveguide dimension. That's where this is going.

kelsolaar 6y ago

I will be pedantic but there is no light at 4000nm. Light is by definition the radiation that is considered from the point of view of its ability to excite the human visual system (HVS). The HVS sensitivity, as given in ASTM E308-15 practise, is in range [360, 780]nm.

datenwolf 6y ago
Well, the semantics of what constitutes light and what not are a bit murky. CO2 lasers are still considered LIGHT amplification by stimulated emission of radiation. CO2 lasers operate at ~10000nm. In the optics community we usually consider everything we can manipulate with refractive optics as "light" – and yes, I am fully aware that this goes down well into what's considered microwave radio. My personal cutoff for where optics begins is, where I no longer can use an antenna that is part of a resonant _circuit_ to emit / receive the radiation, and have to resort to quantum mechanical state transitions.