[Cryptography] Why full-fledged quantum computers might always be five years away

[Peter Gutmann]

Jon Callas <jon at callas.org> writes:

>What is a quantum computer? The question feels deceptively simple. It is a
>computer that uses quantum effects to run calculations

Which is what current physics experiments (misleadingly labelled as computers)
are not:

  computer, n: a programmable electronic device designed to accept data,
  perform prescribed mathematical and logical operations at high speed, and
  display the results of these operations

  experiment, n: A scientific procedure undertaken to make a discovery, test a
  hypothesis, or demonstrate a known fact

With a "quantum computer" you take a known fact, the product of two primes,
set up a physics experiment to demonstrate it and, if the experiment succeeds,
issue a press release about your new factorisation record.

These are not "computers" no matter how much you bend the definition.  They're
physics experiments, an exact match for the dictionary definition of an
experiment, "a scientific procedure undertaken to demonstrate a known fact".

Peter.