Cryptocurrency mining using integrated photonics
Public blockchain systems are distributed databases that anyone can submit write transactions to and where you don&#x27;t need preauthorisation to join the system.  In order to avoid the network being taken over by sybil attacks, it&#x27;s necessary for participation to be based on locking up &#x2F; committing &#x2F; consuming something rare.  Anything that becomes cheap or easy is not suitable for basing participation on.<p>So far I know of systems using computational work (PoW), ownership of cryptocurrency (PoS), or storage space as that rare resource.  The idea of using photonics to create a low energy &#x27;proof of time&#x27; basis is interesting but there would still be difficult economic considerations.  If acquiring the photonics is too hard, then you&#x27;ve got a centralised system, if it&#x27;s too easy then the sybil resistance and environmental impact benefit goes away (because control of the system devolves into &#x27;who can acquire the most hardware&#x27; incentivising massive production).<p>Perhaps surprisingly, improving the cost efficiency of the work done by a traditional PoW blockchain doesn&#x27;t reduce its energy usage, because the usage is determined by a competitive market place driven by supply &amp; demand, not by a fixed amount of work needing to be done.  Increasing the cost efficiency of the calculations just results in the blockchain doing more calculations.<p>A huge chunk of the cost is in the electricity used, so power efficiency and cost efficiency are very very similar. 
 Ultimately I don&#x27;t think you can improve matters much by attacking power efficiency of the calculations.  You may be able to move the economic balance point between upfront&#x2F;ongoing costs by requiring more or more expensive hardware, but reducing ongoing electricity usage isn&#x27;t a clear win if it&#x27;s produced more waste and power usage during the creation and ultimate disposal of the hardware.