The gigantic field of “quantum computing” with many thousands of active researchers, hundreds of thousands of publications, numerous conferences and workshops, daily announcements of new breakthroughs, and many, many billions of dollars spent, has been triggered by Shor’s invention of his famous algorithm for factoring extremely large numbers (thus eventually opening the door for quantum computers to break security codes), and by the developments of methods for quantum error correction, which is generally considered as being absolutely indispensable.
The worldwide quantum computing euphoria and the general excitement are going on already for a quarter of a century! Before engaging further for another 25 years, it might be wise to have a look at the achievements reached to date during this period.
The observable outcome can be summed up as follows:
• Factoring the number 15 by Shor’s algorithm is still not possible.
• Error correction has still never been achieved, even on a very small scale.
• No quantum device exists, capable of doing elementary arithmetic, like 3 × 5, or
3 + 5.
Thus, after a quarter of a century, there are absolutely NO meaningful results in
• The only working quantum machines to date are those introduced by the D-wave Systems company in 1999, and currently intensely studied and developed by Amazon, Google, IBM, and other tech giants, as well as by the D-wave company itself. These machines can perform quantum annealing but so far are not capable of error correction and thus are NOT quantum computers in the original sense of this term. They too are not capable of factoring 15, nor calculating 3 + 5. However, they are interesting from the scientific point of view and allow to obtain some valuable results [30–33].
• With no clear reasons to believe that this situation is going to change during the next 25 years, the perspectives of quantum computing appear to be extremely doubtful.