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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.arch
Subject: Re: Is Intel exceptionally unsuccessful as an architecture designer?
Date: Thu, 19 Sep 2024 20:12:51 +0200
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On 19/09/2024 18:23, MitchAlsup1 wrote:
> On Thu, 19 Sep 2024 14:15:09 +0000, David Brown wrote:
> 
>> On 19/09/2024 12:59, Terje Mathisen wrote:
>>
>> According to someone on the internet (that ever-reliable source of
>> information), an n-bit integer takes 2n + 2 fully entangled qubits and
>> 448.n³.log(n) gates.  For 1024-bit RSA, that's 2050 logical qubits and
>> about 5×10e12 gates.    For the common default size of 2048-bit RSA,
>> it's 4098 logical qubits and 4.2×10e13 gates.
>>
>> Then you need the quantum error correction in addition.  I am not at all
>> convinced that I understand the details here or if I am applying them
>> correctly, but I think that for larger systems you need perhaps 1000
>> physical qubits per logical qubit.
> 
> I am convinced that quantum computers will eventually be good at
> some things that regular computers are not and cannot be.
> 

OK.

They are already good at a few tasks, but they are not particularly 
useful ones.

> I am not convinced that any current application is one of those.
> 

Agreed, at least as far as we have seen so far with quantum computing.

> And for the things that quantum computers may be great at
> {Deciphering without keys} they may do more harm than good.

I also don't think breaking encryption would be a useful thing.  There 
may be other good uses of integer factorisation, however.

Still, I don't believe quantum computers will ever actually be any good 
for this, unless someone comes up with a far better algorithm.  I think 
it will always be easier and cheaper to break encryptions using social 
engineering, tricks, malware, bribery, blackmail, or - if all else fails 
- rubber hose cryptoanalysis.