# Talk:Quantum tunnelling

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## Archives

I added an archive box, so unless there is an issue I will be removing this section soon. Phancy Physicist (talk) 22:03, 24 August 2010 (UTC)

### Non-article Chat

Though related to the article, I don't think that the posts in this archive are about improving the article. Please correct me if I am wrong and please don't get mad if I moved your post. I'm just trying to make sure that things in the article that need attention get attention.

Phancy Physicist (talk) 09:33, 8 July 2010 (UTC)

The posts in this archive are matters that have been addressed in the past.

Phancy Physicist (talk) 09:33, 8 July 2010 (UTC)

### Out Dated Discussions

The posts in this archive are just old. If you think they still need fixed, repost them.

Phancy Physicist (talk) 09:33, 8 July 2010 (UTC)

## Translation

The article's page in Turkish wiki is: http://tr.wikipedia.org/wiki/T%C3%BCnel_etkisi Can you please link it? I don't know how to do it.

## Meandering and overly mathematical

First of all, this article betrays a poor grasp of the physical origin of tunneling phenomena. Tunneling occurs because particles exhibit wavelike properties, and are described by wave functions which satisfy the Schroedinger equation. By conservation of probability current, the wave function and its first derivatives must be continuous at a potential barrier. This results in an exponentially decaying wave function (and probability density) in the classically forbidden region. By the Heisenberg uncertainty principle, any attempt to localize the particle within the tunneling penetration length leads to a commensurate uncertainty in the momentum (and hence energy) of the particle such that its energy in the forbidden region is no longer known with sufficient precision.

Secondly, most of the math in this article is irrelevant to understanding the basic physics. Tunneling can be sufficiently understood by studying the finite potential barrier or finite potential well systems. This should require three or four equations at most. Also, like many quantum phenomena, tunneling has analogues in classical physics (evasnescent waves). Such a discussion of evasnescent waves would aid in the understanding of quantum tunneling. --Brian C 07:00, 8 February 2006 (UTC)

Everything you say in words is included in the mathematics. This is an encyclopedic article, so it needs a watered down explaination and possibly an in depth explaination. You are free to add an in depth explaination that is English and not mathematics. A square-well potential would be good to add. It would show tunneling behavior. However, the square-well potential is unphysical and has an incorrect classical limit. CHF 00:59, 4 March 2006 (UTC)

I want to point out that this article seems much inferior and much less adherent to the spirit of quantum mechanics than the article of the particle in the square well. Yet, the questions in this discussion section, while highly schizophrenic and disorganized, are very good natural deep questions. In other words I think the article needs better organization, and better language (sometimes they are inseparable) so that the questions may asked in the more natural language and not seem so incongruent. For example when someone asks the perfectly natural question: Is tunneling the fact that the particle is in the classically forbidden region of the wall. As it turns out tunneling is not one thing, but a number of related behaviors, of which being *in* the forbidden region is one of them. Another is crossing the forbidden region. Yet another is crossing the forbidden region with much more likelihood than you should classically. Also a non normalizable barrier-Hamiltonian eigenstate being non zero on both sides of the barrier (the most common association to the word tunneling) is not tunneling in the true sense of the word since tunneling roughly means: first you're on one side of the barrier, then at a later time your on the other side, and you never had enough energy to get across. —Preceding unsigned comment added by 131.94.20.246 (talk) 21:25, 16 January 2009 (UTC)

## Quantum field theory

Is there a reason that this quantum tunnelling page doesn't mention quantum field theory and virtual particles as being responsible for how the mechanism works? 130.88.117.230 (talk) 07:44, 4 June 2008 (UTC)

## Figure

In the figure on the left, a particle "tunnels" through a barrier. What is the form of the barrier in the example? To me, it looks like the particle is crossing the barrier, not tunneling through it. If the barrier is finite, the incoming wavepacket will have components above the barrier, and those are the ones that are transmitted. If the barrier is infinite, there should be no transmission (or tunneling). --24.34.222.177 (talk) 06:01, 29 December 2008 (UTC)

## Medium Types

If I may be so bold, what the hell are medium type 1 and medium type 2? Was anybody planning to define these terms at any point, or is it just assumed that everybody magically knows what that means? 98.204.74.229 (talk) 01:51, 13 March 2009 (UTC)

Medium type 1 is where the wave-equation has traveling-wave solutions; medium type 2 is where the wave-equation has solutions that are rising or falling exponentials. This language is meant to apply to all wave-equations, and normally arises physically because different media (e.g., glass and vacuum, for a light wave) have different properties A new section attempts to explain in more detail how this arises, in the context of quantum mechanics and the Schrödinger equation. Sentence has also been added to lead section (RGForbes (talk) 02:33, 20 March 2009 (UTC))
I agree this "Medium Types" wording is cumbersome, unclear and unnecessary. The concept of different mediums is needed but it doesn't have to be so "jargony". I will try to reword when I get time. Feel free to beat me to it.

Phancy Physicist (talk) 19:27, 8 July 2010 (UTC)

## Marking for cleanup

The writing in the section beginning with "Three notes..." could do with some reworking. Would appreciate 128.8.177.9 (talk) 16:56, 1 May 2009 (UTC)

## Spelling change. Please leave it.

Please don't change the spelling of "tunnelling" to "tunneling". both appear to be correct but the link to this article and the title are spelled "quantum tunnelling". I don't either way about spelling but the article should be self consistent. So I have changed it to match the title and link.

Phancy Physicist (talk) 17:58, 8 July 2010 (UTC)

## Orphaned text.

The following is some orphaned text from my rewrite of A semi-classical method for determining a formula for tunnelling probability

"

This classical limit would have failed in the unphysical, but much simpler to solve, situation of a square potential.

A related subject is above barrier reflection: in classical physics a particle will not reflect if its energy is above the potential barrier, but in the quantum case it is possible. In this case, the reflection coefficient is exponentially small in Planck constant. The semiclassical technique of calculation of the reflection coefficient is similar to the calculation of the tunnelling described above.

In a specific tunnelling problem, we might suspect that the transition amplitude is proportional to ${\displaystyle e^{-\int dx{\sqrt {{\frac {2m}{\hbar ^{2}}}\left(V(x)-E\right)}}}}$ and thus the tunnelling is exponentially dampened by large deviations from classically allowable motion.

"

I try to figure out what to do with it later.

Phancy Physicist (talk) 07:58, 15 July 2010 (UTC)

## Copy of WKB subsection.

I feel pretty stupid but I rewrote the section Applying the WKB method to tunnelling probability without even checking the WKB article first! This section is a bad or maybe old copy of the this WKB subsection. There are some changes that I will transfer to the WKB article but I think that this redundancy is silly since the WKB method has no direct connection with quantum tunnelling except that it provides a way of calculating transmission and reflection coefficients. I am going to remove it soon unless there are objections.

Phancy Physicist (talk) 08:37, 15 July 2010 (UTC)

## Spelling: tunnelling vs tunneling

This article is titled Quantum Tunnelling and uses the spelling tunnelling throughout, but that is not the correct spelling of the word. The correct spelling is tunneling (see references in Further Reading). Recommend changing the name of the page and all the spelling throughout. --Yoda of Borg (talk) 21:11, 12 August 2010 (UTC)

"Tunnelling" is proper English. This is the link to the Wikipedia Guidelines on American and British Spelling. As I said earlier on this talk page I don't really care which is used as long as the page and link are self-consistent, but there is no reason to change it now. Phancy Physicist (talk) 17:13, 15 August 2010 (UTC)
There is no doubt that "tunnelling" is just as acceptable in global English as "tunneling." In fact, "tunnelling" seems to be the preference on Wiktionary (although many spell checks prefer "tunneling"). It is also true that Wikipedia explicitly says that no spelling is preferred, except spelling should be consistent within an article . It can be seen that many American-authored articles use "tunneling." However, it is also found that neither the British, American, or physicists in general are consistent (most authors stick to one spelling, but groups are inconsistent). And, lastly, it should be pointed out that the Wikipedia article on Tunneling itself chooses a spelling, and, in turn uses that spelling to refer to this article, and it may be preferable to make the two consistent (or perhaps it is better to present both possibilities). For now, I think that there are greater issues to worry about with regard to this article, especially making sure that it captures the general, theoretical idea/concept well enough for a general audience.Brent Perreault (talk) 03:14, 18 August 2010 (UTC)
I second the above. There is more to worry about with this article than the spelling.:) Phancy Physicist (talk) 05:16, 22 August 2010 (UTC)
Personally, I'd like to see in the intro just a parenthetical note (also tunneling). The reason is that students using this page for assignment research, depending on what country they are in, could face a lower grade for misspelling if the teacher doesn't approve. Teachers have to be consistent in their classrooms, too.5Q5 (talk) 17:26, 2 October 2012 (UTC)
Here is an example of "(or tunneling)": http://www.sciencedaily.com/articles/q/quantum_tunnelling.htm. 5Q5 (talk) 15:28, 3 October 2012 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── I added to the intro "(also spelled quantum tunneling in American English)" based on these examples found in other articles, of which more can be found. 5Q5 (talk) 15:42, 5 October 2012 (UTC)

The main thing is consistency. I have amended all used of "tunneling" to match this article's title (except where used in cited reference titles). Also, I have re-added text in the lead to mention the alternative spelling. I don't understand why this was removed before. Bazonka (talk) 07:05, 27 July 2013 (UTC)

## "Mechanical Energy"

I took the liberty of changing the reference to "mechanical energy" to read "kinetic energy" in the intro, since that makes sense in the particular context. Please reverse this change if you do not agree. The term "mechanical energy" according to wikipedia is the sum of kinetic plus potential energy anyway, so potential energy was already included in "mechanical energy" (total) that was compared with the potential energy barrier. Does that make sense?CecilWard (talk) 19:44, 12 January 2011 (UTC)

## "Shining stars"?

In the intro, it says that quantum tunnelling is related to the phenomenon of "shining stars." Now, I'm not an expert on the subject, but I'm assuming that this refers to how light from stars reach Earth and how it is measured. I'm not sure how this could relate to the concept of quantum tunnelling, as the phrase is very ambiguous. If this isn't vandalism, some clarification would be beneficial, since the the reference is from a textbook and thus not readable by everyone. Eridani (talk) 18:47, 5 May 2011 (UTC)

Here is the quote from the book: "It's interesting to note that a quantum effect is key in making sunshine. Temperatures inside stars like the Sun are not high enough to allow colliding protons to overcome the Coulomb repulsion. In a certain percentage of collisions, however, the nuclei pass through the barrier anyway, an example of quantum tunneling". Dauto (talk) 21:42, 5 May 2011 (UTC)

Where is the Japanese Physist who invented Tunnel Diode? There were 3 winner of 1973 Nobel Prize, why you obmit the third one? This is a biased article. Please remove it. — Preceding unsigned comment added by 67.124.39.78 (talk) 11:54, 5 January 2012 (UTC)

## Major rewrite

I'm planning a major rewrite of this article. Most of the actual information in the article is correct, but poorly organized. I will start next week or two, I will try to take into account the most recent discussion, but please weigh in if you have strong opinions about how the article should look. — Preceding unsigned comment added by Infinitooples (talkcontribs) 22:51, 6 January 2012 (UTC)

I hope this is not considered unimportant or redundant given the above discussion, but if a total rewrite of the article is being done then SOME principled (non-coin-flippy) decision should be made about the preferable spelling of the key word "tunnelling/tunneling". There is no argument about the broad linguistic acceptability of both spellings. It appears, however, that the spelling of the word in the article's reference sources is (almost always?) the one-L variant. If indeed there is a dominant spelling in the professional literature, then clearly that's what should be used in this article as well! And if it turns out that a noteworthy number or category of professionals use the less-common spelling perhaps this fact could be mentioned parenthetically in the article's introduction. The less-common spelling can have a redirect page to the more-common one so no existing links are severed. Ontyx (talk) 05:31, 12 July 2012 (UTC)
A rewrite is definitely needed. Parts of the article are wordy, meandering, and unfocused. The point another poster makes about incomplete descriptions and explanations is also valid.
As for spelling... There's a rule in English that if vowels are separated by a single consonant, the first is long. "Tunneling" is therefore incorrect, unless you want to pronounce it "tu-nee-ling". There are other examples where the incorrect spelling is now accepted as correct (most notably "kidnaped"). WilliamSommerwerck (talk) 17:09, 22 May 2013 (UTC)

## teleportation as a tunneling effect

In James Blish's Spock Must Die!, the possibility of using quantum tunneling to transport objects (rather than disassembling/reassembling them) is briefly discussed. Such a discussion might make an interesting addition to this article. WilliamSommerwerck (talk) 17:09, 22 May 2013 (UTC)

## Question about history

From the article: "Friedrich Hund was the first to take notice of tunnelling in 1927 when he was calculating the ground state of the double-well potential.[4] Its first application was a mathematical explanation for alpha decay, which was done in 1928 by George Gamow and independently by Ronald Gurney and Edward Condon.[5][6][7][8] The two researchers ..." To whom does "The two researchers" refer?

## Incorrect Description of 1973 Nobel

Hey, I'm not a Wiki editor but just wanted to note that the article in its present form mischaracterizes the various independent experiments on tunneling in semiconductors and superconductors that were jointly awarded the Nobel Prize in physics in 1973. It currently reads "The work of Leo Esaki, Ivar Giaever and Brian David Josephson predicted the tunnelling of superconducting Cooper pairs, for which they received the Nobel Prize in Physics in 1973."

This is incorrect. Esaki experimentally verified tunneling in semiconductors in 1958 (his work had nothing to do with superconductivity). In 1960 Giaever used tunneling to measure the superconducting band gaps predicted by BCS theory. In 1962 Josephson alone predicted the tunneling of Cooper Pairs. — Preceding unsigned comment added by 130.132.173.233 (talk) 17:27, 17 January 2014 (UTC)

## Clearance

If all the energy in the universe creates a singularity where time holds still does it mean something is always left out in order to satisfy the consistency principle?

I had no idea talk was forbidden, are you with the government?

189.58.174.240 (talk) 05:34, 3 February 2014 (UTC)

ADDENDUM: http://www.businessinsider.com/atoms-reach-record-temperature-colder-than-absolute-zero-2013-1 apparently proves that Heisenberg can be cheated. Probably because "infinite" energy is not infinite, just a lot. Meaning, it doesn't take all the energy in the universe to cheat Heisenberg. Just a lot. Because traditional models in physics assume the real domain perhaps? Maybe.

189.58.174.240 (talk) 07:45, 3 February 2014 (UTC)

## Introduction to the concept needs a clarity boost

There are a couple of things that make this section hard to understand.

It says "In quantum mechanics, these particles can, with a very small probability, tunnel to the other side, thus crossing the barrier. Here, the "ball" could, in a sense, borrow energy from its surroundings to tunnel through the wall or "roll over the hill", paying it back by making the reflected electrons more energetic than they otherwise would have been."

"These particles" has already been introduced as "particles that do not have enough energy to classically surmount a barrier", which is fine. The "ball" represents that inability, which is also fine, but where did the electrons come from and why and how are they reflected? 78.144.72.141 (talk) 18:50, 6 September 2014 (UTC)

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