Wikipedia:Featured article review/Quantum computer/archive1

The following is an archived discussion of a featured article review. Please do not modify it. Further comments should be made on the article's talk page or at Wikipedia talk:Featured article review). No further edits should be made to this page.

The article was removed 08:25, 13 May 2007.

---

Quantum computer

Review commentary

Messages left at Physics, Computing, Computer science and Technology. SandyGeorgia (Talk) 17:22, 8 April 2007 (UTC)

Quantum computer is a "brilliant prose" promotion (no original author) that had a scanty review in May 2006.

• There is a massive link farm labeled (incorrectly—WP:GTL) as "Further reading".
• Citations are not formatted and the article needs a review for citations.
• There are red links in See also; also, See also should be minimized per WP:GTL, incorporating articles into the text and deleting from See also those that are already included in the text.
• Strange bolding throughout and incorrect use of dashes, indicating the need for a copyedit.
• External jumps (example: D-Wave Systems Inc. (dwavesys.com) ... )
• Poor prose when incorporating other articles, example: See Bloch sphere.
• Mathematical formulas wrap off screen.
• Incorrect italicization and/or use of See also or Seealso template: For discussion of foundational aspects of quantum computing, see the article on quantum circuits.
• WP:MSH issues; title repeated often in TOC.
• Weasly, example: It is widely believed that if large-scale quantum computers can be built, ...

SandyGeorgia (Talk) 17:22, 8 April 2007 (UTC)

Factual problems

Complex numbers

Portions of the following are incorrect

In fact, the register is described by a wavefunction:

$|\psi \rangle =a\,|000\rangle +b\,|001\rangle +c\,|010\rangle +d\,|011\rangle +e\,|100\rangle +f\,|101\rangle +g\,|110\rangle +h\,|111\rangle$

Yes, that's OK.

If a>b>c>d>e>f>g>h, then a+h=b+g=c+f=d+e.

Huh? these are complex numbers, these can't be simply ordered. This is just wrong.

For example:

(2.166/4.4)|000>+(1.966/4.4)|001>+(1.766/4.4)|010>+(1.566/4.4)|011>+(1.434/4.4)|100>+(1.234/4.4)|101>+(1.034/4.4)|110>+(0.834/4.4)|111>

(2.166/4.4)²+(1.966/4.4)²+(1.766/4.4)²+(1.566/4.4)²+(1.434/4.4)²+(1.234/4.4)²+(1.034/4.4)²+(0.834/4.4)² = 1

WTF. Just delete this.

where the coefficients a, b, c,... are complex numbers...

this is correct. I'll make edits to cut out the questionable stuff shortly. linas 23:13, 10 April 2007 (UTC)

Number of states

I turned the following remark into a footnote, as it is trite and irrelevant:

Note that the coefficients are not all independent, since the probabilities must sum to 1. The representation is also (for most practical cases) non-unique, since there is no way to physically distinguish between a particular quantum register and a similar one where all of the amplitudes have been multiplied by the same phase such as −1, i, or in general any number on the complex unit circle. One can show the dimension of the set of states of an n qubit register is 2ⁿ⁺¹ − 2. See Bloch sphere.

linas 23:18, 10 April 2007 (UTC)

---

Other than the two problems above, which I've corrected, the article appears to be scientifically correct, from the point of view of quantum mechanics. linas 23:55, 10 April 2007 (UTC)

• I've corrected the formatting on section headings as they were distorting the entire TOC at WP:FAR. Please take care with excessive TOC headings at FAR. Thanks, SandyGeorgia (Talk) 14:16, 11 April 2007 (UTC)

Bits vs. Qubits

This section gives a short description of qubits, but in my view does not sufficiently contrast them to bits, as the section title would indicate. One may note e.g. that 2^n is also the number of bit sequences that n bits can represent. The indicated number of states for qubits should be directrly compared against bits to make this section more clear and true to its purpose. Added by 84.74.194.32 (talk · contribs) 22:47, 16 April 2007

FARC commentary

Suggested FA criteria concerns citation sufficiency and formatting (1c), links, jumps, and other formatting issues (2), and prose (1a). Marskell 10:31, 25 April 2007 (UTC)

• Remove per 1c. "Further reading" is also an external link farm in disguise. LuciferMorgan 11:30, 29 April 2007 (UTC)

Comment I've been cutting the link farm down to size and adding appropriate footnotes, but it's probably not satisfactory yet. Anville 15:36, 7 May 2007 (UTC)

• Remove, issues raised on FAR almost entirely unaddressed. SandyGeorgia (Talk) 12:49, 9 May 2007 (UTC)

• Remove per the above. Trebor 14:38, 12 May 2007 (UTC)

The above discussion is preserved as an archive. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article review. No further edits should be made to this page.