Heh. I worked on a type of photonic PoW in 2019 (but it wasn't silicon photonics).

- It's faster and lower power for the hash rate. It's worth it. But not as fast and low power as hoped.

- It's a great advantage for the early adopter who can mine that bit faster than everyone else for a short time. That was the motivation for the project.

- Contrary to the title of the article, making hashing faster for less energy doesn't "help with the high energy consumption of the crypto currency mining activities" once the technology becomes available to enough miners.

It's the same as the introduction of ASICs before it: only a temporary advantage to those few who have it first. Of course that's only a few miners, so it doesn't affect energy consumption of the whole blockchain much. As soon as a new technology becomes widespread enough to have a significant effect on the whole blockchain, blockchain proof-of-work returns to exactly the same amount of energy consumption as whatever technology came before it.

It's because of how the mining-price system works, proof-of-work energy consumption is independent of the technology widely used. In other words, you can't solve the proof-of-work energy consumption problem with a new proof-of-work hashing technology.

So whenever you see a headline or article promoting a new proof-of-work solution on the grounds that it will reduce energy consumption of the blockchain - that's false. Snake oil, even.

(On the other hand, other mining methods such as proof-of-stake do reduce blockchain energy consumption for real, in exchange for different problems, perhaps.)

But I think the Eindhoven people have understood this, and it's the journalism that misleads in this respect. From the article:

> From our perspective, the ideal proof of work algorithm would be an algorithm that spends no energy, but time (i.e. pure delay). This kind of proof of work is hardly possible in the real world. So instead, we would love to see some sort of a “computational delay” when only a small fraction of energy is spent on proof-of-work computation, while this computation itself introduces a time-delay. We believe that photonics can help us to achieve such a “computational delay”.

I'm surprised Verifiable Delay Functions (VDFs) are not mentioned. There is has been an emerging field of cryptography focused on delays enforced mathematically, called Verifiable Delay Functions, since about 2018. Rather like the technology race of proof-of-work, VDFs rely on the assumption that underlying technology (logic gates, arithmetic units (like in analogue photonics), etc) is somewhat evenly distributed; that nobody has access to a technology that can perform the calculations with much lower delay than everyone else.

VDFs still won't reduce energy consumption if they are used as another form of proof-of-work. For example if running many delay functions calculated in parallel gives a mining advantage, many will be built and together they will use the same amount of energy as proof-of-work. To provide a real energy consumption benefit, the blockchain consensus method needs to change as well. Think "proof-of-verifiable-delay". As far as I know, no such method has been worked out yet.