
Quantum computer built inside a diamond - wglb
http://www.sciencedaily.com/releases/2012/04/120404161943.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+%28ScienceDaily%3A+Latest+Science+News%29
======
readme
Can someone more inclined elaborate a bit on this please?

"As opposed to traditional computer bits, which can encode distinctly either a
one or a zero, qubits can encode a one and a zero at the same time. This
property, called superposition, along with the ability of quantum states to
"tunnel" through energy barriers, will some day allow quantum computers to
perform optimization calculations much faster than traditional computers."

I get it, a qubit can store multiple states, but if someone could give a
little more on how it does that, and why that means quantum computers will be
faster someday, that'd be excellent.

~~~
Radzell
I wrote a paper in highschool so take this with a grain of salt basically the
idea is have truly parallel programming instead of having concurrent ones the
ability of the qubit to solve for multiple states means they can solve for
multiple problems at the same time while conventional computing seems parallel
whats really happening is that calculation are switching states so fast they
feel parallel. If I am wrong someone correct me.

~~~
buu700
Yeah, that's completely off (it would be a more apt description of the
distinction between multiple cores and hyperthreading).

The important characteristic of quantum computation is not that it's faster or
more parallel than classical computation, but that it's a _generalisation_ of
classical computation. The same way that classical mechanics describes a
subset of quantum mechanics rather than disjoint phenomena, all current
classical CPUs are technically "quantum" CPUs (the best kind of quantum
CPUs!).

So, what does this mean?

Well, for all the software we have today, and for almost everything we know
how to code today, absolutely nothing; in fact, most of what we can do on
classical computers will be slower simply because it will be _quite_ some time
before a quantum computer is anywhere near as well-engineered as, say, a Core
i7 – especially when you take into account that the properties of quantum
mechanics make this engineering not only different but also significantly more
difficult.

What we do get from the computational paradigm shift, however, is a broader
set of operations which allow for a broader set of algorithms.

Take Grover's algorithm (the one mentioned in the article):
[http://en.wikipedia.org/wiki/Grovers_algorithm#Algorithm_ste...](http://en.wikipedia.org/wiki/Grovers_algorithm#Algorithm_steps)

If you understand the notation, what you'll see is a series of linear
operations (quantum gates) being applied to vectors (qubits (classical bits
are scalars)) in a quantum circuit. These can all be used to describe any
operation which would be performed on, say, an x86 core (albeit more
verbosely), but can also take advantage of quantum mechanical properties to
manipulate non-classical information (which gets complicated to discuss).

For the canonical example of how this can significantly change computation as
we know it, see Shor's algorithm, which speeds up prime number factorisation
from sub-exponential time to polynomial time, and thus could potentially break
RSA encryption if we had a practical quantum computer):
<http://en.wikipedia.org/wiki/Shors_algorithm>

Aside from that, I'm sure people much smarter than I am could go on in
technical depth about how, despite not _really_ being an advancement of
mythical proportions in and of itself, this new class of algorithms would be
able to revolutionise areas like search, machine learning,
physical/biological/chemical simulation, and so on.

------
Symmetry
I should point out that diamonds can also make very good semiconductors when
properly doped, with very large carrier mobility compared to silicon. We just
don't know how to make the necessarily complex patters on them.

~~~
jpdoctor
> _I should point out that diamonds can also make very good semiconductors
> when properly doped, with very large carrier mobility compared to silicon.
> We just don't know how to make the necessarily complex patters on them._

Don't know what you mean by "properly doped": The biggest problem with diamond
is that it is a bitch to make n-type. In fact, the conduction band is above
the vacuum level!

It is why people try to use diamond as a thermionic emitter: electrons in the
conduction band naturally try to leave the material.

~~~
stephengillie
Doping is the intentional adding of impurities.

Maybe phosphorous could be added among the carbon molecules in the diamond,
similar to how silicon is doped with phosphorous to make a better
semiconductor.

Maybe nitrogen or oxygen would be a better choice, for the similarity in
molecule size - they wouldn't disrupt the diamond's carbon lattice structure
as much.

<http://en.wikipedia.org/wiki/N-type_semiconductor>

~~~
jpdoctor
You realize that pretty much every group V dopant has been already measured?
The problem is that n-type dopants are deep in energy, far away from the
conduction band. So the electron from the donor stays with the dopant atom
rather than activating and putting its electron in the conduction band.

> _Maybe nitrogen or oxygen would be a better choice, for the similarity in
> molecule size_ [Typo: Dopants are atoms not molecules.]

Many Group V atoms have been tried. See eg
<http://phycomp.technion.ac.il/~david/thesis/node17.html>

