Re: Quantum computing practically impossible

[Masataka Ohta <[e-mail]>]

Viktor Dukhovni wrote:

> No.  That's not the case.  The scepticism around in principle
> scalability of QCs is in fact centered on whether environmental noise
> can be corrected in principle or not.  Much has been written about this
> by Gil Kalai, who has a long-running debata with Scott Aaronson on this
> issue.  Neither side has conceded.

The point of Gil should be that:

	https://www.quantamagazine.org/gil-kalais-argument-against-quantum-computers-20180207/
	All physical systems are noisy, he argues, and qubits kept
	in highly sensitive “superpositions” will inevitably be
	corrupted by any interaction with the outside world.

should, obviously, be valid.

However, he overlooked a fact that "interaction with the outside
world" is very strong in quantum computers running quantum
algorithms where qubits directly involved in some QEC circuits are
actively entangled with many other qubits outside of the QEC
circuits but, still, in the quantum computers.

> Time will tell who's right.

Now is the time.

 > The devil is in very difficult details of
 > the noise models that the experts don't agree on.

Not. It's just straight forward.

In my draft, I strictly follow the noise model by Shor that
noises result in local interaction between qubits and their
local environment.

However, though Shor overlooked a fact that local environment
states and resulting error/noise operators are different term
by term if quantum state is entangled represented by superposition
of many unentangled terms, the local environment states and resulting
error/noise operators are different term by term.

In other words, Shor thought entangled states were just as fragile/noisy
as unentangled states, against a well known fact that really entangled
states are a lot more fragile/noisy than unentangled states.

						Masataka Ohta