Slashdot Mirror
Quantum Computing: A view from the enemy camp
SIGFPE writes "There seems to be an unthinking acceptance by many people that quantum computers are now on their unstoppable way up and before too long we'll be cracking RSA and simulating protein folding on complex quantum computers. However there is another point of view that considers quantum computers to be as difficult to make as perpetual motion machines - and for much the same reason: entropy. As an antidote to all the successes that have been reported on /. here is a just published and highly readable preprint by a sceptical mathematical physicist."
While everything stated in this paper is all well and good and valid, he's missing the fundamental point of innovation.
You make no progress with pessimism.
CyberBlood
And because no organisms use lasers as a defensive weapon, they cannot exist?
evolution dictates that any lifeform that does not take full advantage of its enviroment will not survive to procreate
Evolution dictates nothing of the sort. All that happens is the fittest of any set of organisms is more likely to survive. There is no guarantee of optimality (otherwise I would currently be making a fortune with my perfect genetic algorithm-evolved stock market model).
An interesting article, but it seems to rely on several strange arguments. I wouldn't agree that the accuracies required in manufacture and operation are not achieveable. It would seem to me that a fabrication accuracy of 1 part in 10^5 is scarcely unachieveable, especially since we have everyday devices, for example LCD monitors in which less than 1 pixel in 1 million is dead, and those are consumer products.
I don't necessarily buy his argument about the inherent fault-intolerence of quantum computing either, since it relies on the idea that a simple computer with no fault tolerence built in is fault intolerant! Scarcely a surprise. He didn't make a convincing argument that building in fault tolerance is impossible, only that it isn't being done in the simple designs he notes. Maybe I've misunderstood, but it would seem that this is an avenue for more research, rather than less.
It seems to me that in the end the whole of his argument relies on the engineering argument that we don't at present have any way to measure large numbers of single spin states (or indeed any single spin state). This would seem again to be an argument for more research, rather than less, since engineering serendipity is not a predictable mathematical process.
I understand his frustration that quantum computing is taking a lot of research funding from other areas, but I'd be a little more cautious than he is about saying that it definitely _can't_ work.
As sung by the infamous Mc Hawking.
Entropy, how can I explain it? I'll take it frame by frame it,
to have you all jumping, shouting saying it.
Let's just say that it's a measure of disorder,
in a system that is closed, like with a border.
It's sorta, like a, well a measurement of randomness,
proposed in 1850 by a German, but wait I digress.
"What the fuck is entropy?", I here the people still exclaiming,
it seems I gotta start the explaining.
You ever drop an egg and on the floor you see it break?
You go and get a mop so you can clean up your mistake.
But did you ever stop to ponder why we know it's true,
if you drop a broken egg you will not get an egg that's new.
That's entropy or E-N-T-R-O to the P to the Y,
the reason why the sun will one day all burn out and die.
Order from disorder is a scientific rarity,
allow me to explain it with a little bit more clarity.
Did I say rarity? I meant impossibility,
at least in a closed system there will always be more entropy.
That's entropy and I hope that you're all down with it,
if you are here's your membership.
You down with entropy?
Yeah, you know me!
You down with entropy?
Yeah, you know me!
You down with entropy?
Yeah, you know me!
Who's down with entropy?
Every last homey!
Defining entropy as disorder's not complete,
'cause disorder as a definition doesn't cover heat.
So my first definition I would now like to withdraw,
and offer one that fits thermodynamics second law.
First we need to understand that entropy is energy,
energy that can't be used to state it more specifically.
In a closed system entropy always goes up,
that's the second law, now you know what's up.
You can't win, you can't break even, you can't leave the game,
'cause entropy will take it all 'though it seems a shame.
The second law, as we now know, is quite clear to state,
that entropy must increase and not dissipate.
Creationists always try to use the second law,
to disprove evolution, but their theory has a flaw.
The second law is quite precise about where it applies,
only in a closed system must the entropy count rise.
The earth's not a closed system' it's powered by the sun,
so fuck the damn creationists, Doomsday get my gun!
That, in a nutshell, is what entropy's about,
you're now down with a discount.
You down with entropy?
Yeah, you know me!
You down with entropy?
Yeah, you know me!
You down with entropy?
Yeah, you know me!
Who's down with entropy?
Every last homey!
How we know is more important than what we know.