If you are to believe the glossy marketing campaigns about ‘quantum computing’, then we are on the cusp of a computing revolution, yet back in the real world things look a lot less dire. At least if you’re worried about quantum computers (QCs) breaking every single conventional encryption algorithm in use today, because at this point they cannot even factor 21 yet without cheating.
In the article by [Craig Gidney] the basic problem is explained, which comes down to simple exponentials. Specifically the number of quantum gates required to perform factoring increases exponentially, allowing QCs to factor 15 in 2001 with a total of 21 two-qubit entangling gates. Extrapolating from the used circuit, factoring 21 would require 2,405 gates, or 115 times more.
underlying article: https://algassert.com/post/2500
If you can make a bubble out of crypto and sub-prime mortgages, quantum computing is a doddle, though I’d bet it comes after compute as a service using all those datacentres (some of which will even get built).
Problem is the AI burst is very likely to take out the US economy (and do bad things to the rest of the world), the home of these scams. But I’m sure some shareholder value was ‘created’.