Quantum computing

Originally posted by robbie carrobie
ok before i appear any more stupid i am going to read quantum mechanics for total noobs, starting here.

http://www.abarim-publications.com/QuantumMechanicsIntroduction.html

wish me luck.

It took me several seconds to find the first error. Try instead:

http://en.wikipedia.org/wiki/Introduction_to_quantum_mechanics

Originally posted by KazetNagorra
It took me several seconds to find the first error. Try instead:

http://en.wikipedia.org/wiki/Introduction_to_quantum_mechanics

what was erroneous?

Originally posted by robbie carrobie
what was erroneous?

Hold that thought (1):

Individual quantum particles are subjected to a completely different law than the law
to which large objects made from quantum particles are subjected.

Given that large objects are made of large numbers of particles following the laws
of quantum mechanics it cannot be [and isn't] the case that large objects follow
completely different laws than the particles that make them.

This is a highly flawed, and frankly just plain wrong way of viewing what is going on.

Everything is made up of tiny particles [or vibrating strings?] which follow a simple
set of physical laws. The behaviour of larger collections of these particles can be
approximated by other models/laws, but the larger objects are still actually only
following the laws that govern the particles that make them.

It's a very important distinction, and the way they put it is highly likely to lead to
misconceptions about what is going on. Which is not a good way to start.

This isn't the only thing they start off getting wrong, but I have neither the time
nor inclination to go through and list them all.

Originally posted by robbie carrobie
what was erroneous?

For instance, there are more than just two kinds of quark. I'm sure there are plenty more mistakes, but such an elementary error is enough to dismiss the entire article.

Originally posted by robbie carrobie
ok before i appear any more stupid i am going to read quantum mechanics for total noobs, starting here.

http://www.abarim-publications.com/QuantumMechanicsIntroduction.html

wish me luck.

Quantum mechanics is for total noobs.

😀

Originally posted by robbie carrobie
ok before i appear any more stupid i am going to read quantum mechanics for total noobs, starting here.

I recommend some Richard Feynman lectures starting here:
YouTube

However if you are willing to do the math, then there are university level courses available on the internet for free eg:
http://oyc.yale.edu/physics/phys-201#sessions

Originally posted by twhitehead
I recommend some Richard Feynman lectures starting here:
https://www.youtube.com/watch?v=xdZMXWmlp9g

However if you are willing to do the math, then there are university level courses available on the internet for free eg:
http://oyc.yale.edu/physics/phys-201#sessions

No sir i don't want to do the maths, I simply want to understand what the concepts are, it is enough for me

Originally posted by googlefudge

Hold that thought (1):

Individual quantum particles are subjected to a completely different law than the law
to which large objects made from quantum particles are subjected.

Given that large objects are made of large numbers of particles following the laws
of quantum mechanics it cannot be [and isn't] the case that large objects ...[text shortened]... ff getting wrong, but I have neither the time
nor inclination to go through and list them all.

This is a highly flawed, and frankly just plain wrong way of viewing what is going on.

so you are saying that they behave in exactly the same way?

Originally posted by robbie carrobie
This is a highly flawed, and frankly just plain wrong way of viewing what is going on.

so you are saying that they behave in exactly the same way?

No, googlefudge is right about quantum mechanics applying to all systems regardless of scale and all quantum physicists would rationally agree. But note that quantum effects are generally much less evident and hard to detect on a larger scale and that other equations other than quantum equations give a accurate enough disruption of that is going on on a larger scale at least most of the time. For example, if you wanted to calculate the amounts of mechanic forces on your bones, you would use Newtonian physics equations and not quantum physics equations since quantum effects on those forces (at least its direct effect. Its indirect effects may be a completely different matter ) would be extremely miniscule on that scale as to be completely negligible and probably totally undetectable. And yet, because the same quantum laws apply to ALL scales, those same quantum effects, minute and negligible as they often are on the larger scale, would nevertheless STILL exist on that scale; it is just that you wouldn't see them.

Of course, for any large scale system, if you arbitrary pick any tiny bit of it that is small enough, you should be able to detect strong quantum effects on that tiny bit of it even though you may not detect quantum effects on the large scale system as a whole. So that is yet another sense (but a subtly different one if you think about it carefully ) that quantum physics applies to all systems regardless of scale.

Originally posted by robbie carrobie
This is a highly flawed, and frankly just plain wrong way of viewing what is going on.

so you are saying that they behave in exactly the same way?

They don't behave in the same way, but are governed by the same equations.

Originally posted by KazetNagorra
They don't behave in the same way, but are governed by the same equations.

so the behavior of these particles are different, although under the same laws? like law abiding citizens and outlaws.

Originally posted by robbie carrobie
so the behavior of these particles are different, although under the same laws? like law abiding citizens and outlaws.

I don't see the problem here.
Elephants and mice are made of the same kind of matter (proteins, water, fat, etc) but they behave very differently. Yes, and...?

Originally posted by FabianFnas
I don't see the problem here.
Elephants and mice are made of the same kind of matter (proteins, water, fat, etc) but they behave very differently. Yes, and...?

There is no actual problem, googlefudge pointed out a mistake, in that a site that i cited had posted erroneous material stating that the laws for very small particles are different than the laws which govern large 'groups of particles'. My understanding is now that this is not the case, for the laws are the same, simply their respective behavior is different. Why it should be different though i cannot say.

Originally posted by robbie carrobie
There is no actual problem, googlefudge pointed out a mistake, in that a site that i cited had posted erroneous material stating that the laws for very small particles are different than the laws which govern large 'groups of particles'. My understanding is now that this is not the case, for the laws are the same, simply their respective behavior is different. Why it should be different though i cannot say.

read my previous post.

Originally posted by robbie carrobie
There is no actual problem, googlefudge pointed out a mistake, in that a site that i cited had posted erroneous material stating that the laws for very small particles are different than the laws which govern large 'groups of particles'. My understanding is now that this is not the case, for the laws are the same, simply their respective behavior is different. Why it should be different though i cannot say.

Essentially it is statistical. In quantum theory the modulus square of the wavefunction evaluated at some position gives the probability per unit volume of finding a particle in an arbitrarily small box centred on that position. Imagine the wave-function is a Gaussian function - a bell curve, then the width of the bell curve is the uncertainty in finding the particle. The uncertainty in the position of an electron and a cannon ball is given by the same rule. but the electron is small compared with the uncertainty and a cannon ball is huge by comparison with the uncertainty - around 43 orders of magnitude bigger. So quantum effects are not evident on macroscopic scales.

The page on "Compton Wavelength" on Wikipedia talks about this, see especially the bit about "Limitations on Measurement".