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Comment by oh_my_goodness | Hacker News Reader

Yeah, they're off by a factor of 1000.

There are other serious technical errors in the piece too. For example they say "because photons move at the speed of light and electrons don't" ... which is irrelevant because electronic signals do move at the speed of light.

The most serious problem is missing context. It's been known for decades that you can build shockingly fast optical switches and even amplifiers. A hundred fs is fast but not unique. The problem is how to connect these devices in a complicated circuit without putting nanoseconds of waveguide in between. Unfortunately 1 ns is 1,000,000 fs.

So in telecom, where you're just going a long way in one direction, optical amplifiers with multi-THz bandwidth have dominated transport since the 1990s. But in computers, no.

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Electronic signals also do not move at the speed of light: https://en.wikipedia.org/wiki/Velocity_factor

Yes they do. It’s just that the speed of light differs slightly depending on the medium.

I think you're missing the bigger picture. While they're both EM but they're significantly different i.e. photon are much more desirable than electron.

For starter, for electron you have contention in the form of collision but there's no collision for photon. Imagine you have vehicles that can go pass through each other without any collision, they will be exponentially faster than the one's without this capability.

For transport, yes light is more desirable. For computing, no. The fact that electrons interact with each other is the basis of computational circuits. The article is about how to get photons to do the same.

Pardon me, but I don't think you get the big picture either. Chip industry is now seriously considering photonics based on-chip interconnect for better speed and efficiency [1][2]. However having this hybrid system of electronics and photonics required conversion overhead that's being lamented in the posted article. Ideally, having native photonics based computing and communication systems is going to be a game changer for better speed and efficiency since no conversion is necessary.

[1]Two Startups Are Bringing Fiber to the Processor:

https://spectrum.ieee.org/optical-interconnects

[2]Power and Latency Analysis of the Memory Tiering Pyramid: The CXL Effects:

https://news.ycombinator.com/item?id=34037321

In both cases it's EM waves that are traveling. In 'electronics,' mobile electrons normally guide the EM waves, which are typically 0-10GHz in frequency. In 'optics,' bound electrons normally guide the EM waves, which are typically hundreds of THz in frequency. In either case, you make a switch by somehow reversibly spoiling the waveguide that connects point A with point B.

Collisions between electrons don't directly affect either picture. You can multiplex lots and lots of completely independent 'electronic' EM waves on one conductor, they pass right through each other exactly as you described for optics, no problem.

The advantage of optics is that the low-loss bandwidth of optical waveguides is enormously wider than the low-loss bandwidth of waveguides made using copper or other conductors. And with optics we have enormous bandwidth available.

One disadvantage of optics is that we don't have a low-lag way to interconnect switches. We can connect switches, but so far the interconnect delays are much, much longer than the switching times. So a fast optical switch is useful, but so far only in systems that are solely "feed forward," like communication.

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