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Comment by perlgeek | Hacker News Reader

If I understood the logic correctly, if you think in terms of transistors, they had a laser on the gate and used that to control an electric charge.

> To reach these extreme speeds, the team made junctions consisting of a graphene wire connecting two gold electrodes. When the graphene was zapped with synchronized pairs of laser pulses, electrons in the material were excited, sending them zipping off towards one of the electrodes, generating an electrical current.

This is not what you typically call a "logic gate", where the control and the output have the same type of energy (either both electric or both photonic), this is more like a fast light sensor?

There are plenty of good applications for fast light sensors, why this article tries to spin it into a logic gate (which it is not) is incomprehensible to me.

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From wikipedia:

> A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device

As long as it implements a boolean function, which this clearly does, it sure sounds like a logic gate. What difference does it make whether the control and output have the same form of energy when the real thing that matters is the information it captures?

Scalability, for one. A modern PC CPU has ~10^10 transistors forming ~10^9 logic gates that work because you can chain them easily.

Interesting to think how many 10^6 faster gates would be needed to do the work of 10^9 at the same speed. Say take the 8086 and make it a million times faster. At about 30K transistors and 5MHz. A photonic 8086 apparently would run blindingly fast around anything available now.

Serial speed is always a gain up, no questions asked I guess.

Obviously all of that is over simplified, and not considering other components to any system that would be built (but hey, it's not like any of this is happening tomorrow anyway).

The issue is not the 30k optical transistor, it's the 60k extremely precise laser pulse generators you need to drive them

> What difference does it make whether the control and output have the same form of energy when the real thing that matters is the information it captures?

Just thinking out loud, but it might break common assumptions about being able to (easily) compose a individual gates into a more complicated logic function.

> What difference does it make whether the control and output have the same form of energy when the real thing that matters is the information it captures?

A logic gate itself doesn't do much useful computation, you have to chain them together.

But how do you chain them, if they use a laser beam as input and an electrical charge as output? You have to use the electrical charge to drive a laser... which is much slower and more energy intensive than a classical logic gate in a modern integrated circuit.

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