[Cryptography] Quantum computers will never overcome noise issues?

[Jay Sulzberger]

On Wed, 7 Feb 2018, Allen <allenpmd at gmail.com> wrote:

> Gil Kalai, a mathematician at Hebrew University, believes quantum
computers will never be able to overcome noise issues. See article at:
> 
> https://www.quantamagazine.org/gil-kalais-argument-against-quantum-computers-20180207/
> 
> Any thoughts on this?

Forty years ago most textbooks of quantum mechanics, very early
in the book, stated that one could never get around the "collapse
of the wave function" if the system under consideration was made
of more than a few atoms.  Indeed all the examples given tend
strongly to become approximately classical when you increase the
number of atoms (or more generally, small parts).  (Here of
course, only for some aspects of the system, for example usually
the atoms themselves tended to remain atoms, and atoms are just
about purely quantum objects, by the argument from ultraviolet
catastrophe.)  I have heard such arguments against the
possibility of building a quantum computer since the seventies.
An analogous argument against the possibility of building the
Brooklyn Bridge goes: "Look the only materials we have are Jello
and hemp package twine.  After thinking about whether we can
build the Brooklyn Bridge out of these materials, we have got
some calculations that show it would be practically impossible.".
And indeed, I think this argument is right.  But the textbooks
are textbooks of physics, not textbooks of engineering.  The
cases considered are important daily presenting cases.  They are
mostly simplifications of real gross physical cases, such as
rocks, tables, pulleys, etc..  But the Brooklyn Bridge is not
built of Jello and hemp twine.  It is built of steel and concrete
and granite.  Though granite occurs in nature, concrete does not,
nor does steel.  Concrete and steel are made by man, and we used
them, and not Jello and hemp, to build the Brooklyn Bridge.  And
some of those old textbooks of physics are indeed wonderful
introductions to quantum mechanics.  But they are not
introductions to the engineering of quantum computers, though
they might be prologomena to the textbooks on quantum computer
engineering.

oo--JS.