quantum dots

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#1 Thu, 04/03/2008 - 14:59

quantum dots

what are quantum dots?
what is the physics behind their existance ?
what theory explains all the properties of quantum dots?
finally i would like to ask what are the funamentals of quantum dots?

Tue, 04/08/2008 - 23:51

re: quantum dots

Hello Shanmukh,

1. Quantum dots are in fact very small physical cavities in which a finite number of particles, for example electrons, are trapped. These dots are commonly engineered by the current silicon technology.

2&3. The physics behind quantum dot is very simple --- quantum mechanics QM which is the most fundamental (and well accepted) theory currently known to mankind. QM governs the dynamics of everything in the microscopic world. Quantum dot is a physical (approximately) realization of the textbook example of the so-called particle-in-a-box which illustrates the quantization of energy when a particle is placed inside a (sufficiently small) box.

To have a complete description of the quantum dot dynamics, practically, one has to deal with the dissipative effects due to the environment as well, which may also be quantum mechanical in nature.

4. As mentioned about, there is nothing fundamental about quantum dots, but it offers very good physical realization of the quantum mechanical effects and mostly like can help us build better devices for both classical or quantum computing.

If you found some technical terms or concepts above not clear enough, and you have no knowledge about quantum mechanics before, it is very natural (partly may due to my poor presentation). To have a quick and dirty understand the QM, try this:

http://www.quantiki.org/wiki/index.php/Introduction_to_Quantum_Theory

and/or wikipedia.

Of course, you are welcome to come back and ask more specific questions!

Thu, 04/10/2008 - 15:17 (Reply to #2)

quantum dots

sir,
i could not actually visualize "how a quantum dots is".how is it possible that a large number of electrons or sometimes atoms enclosed in a 1-dimension?
how does size affect the color of QD's? i'm getting various answers for this particular question which is actually confusing me a lot. what is the actual answer?
if you could send me some material relating these, i would be very happy
my email id is "shanmukh.abhishek@gmail.com".or send a link which gives the above information

Thu, 04/10/2008 - 21:46 (Reply to #3)

Hello, After some searching

Hello,

After some searching on the web, I agree that it is quite difficult to find literature of quantum dots for non-experts. Some what simple webpage I found is this:

http://www.google.com/translate?u=http%3A%2F%2Fnano.nchc.org.tw%2Fdictio...

which is translated from a chinese webpage: http://nano.nchc.org.tw/dictionary/quantum_dots.html

If you want a lecture, I found this:

https://www.nanohub.org/resources/189/

Come back to your comments:

1. Yes, it is difficult to visualize quantum dots, I hope you have more idea after the reading above. In fact, it is more appropriate to say quantum dots are zero-dimension objects. (1d would be called quantum wire)

2. The size affect indirectly the color of a quantum dot. To explain, when you say "color", I suppose you mean the electromagnetic radiation (photons) coming out from a quantum dot.

Due to the quantum confinement (the fact that electrons are trapped in a small region):

2.a The energy of the quantum dots is quantized, in the sense that if we are to measure the energy of a quantum dot, then we get discrete values, called energy levels. (It is wrong to say that the QDs can have discrete energy. This is somewhat too technical, I know)

2.b The smaller the size, the wider the energy level spacing, and hence the higher frequency (towards blue color) light would be emitted

The fact that you get different answers from different people is natural. Because different people have different understanding of quantum dots for different purposes. There is no actual answer if the scenarios is not clearly defined. For example, there are different ways to make quantum dots.

For me, as a theorist, I pay more attention to the basic idea of the quantum dots (physical reason etc.), instead of the fabrication part of it.

I hope my comments and the references above could help you a bit.

Fri, 04/11/2008 - 15:07 (Reply to #4)

thanks a lot sir for giving me the link

thanks a lot sir for giving me such a valuable link for the lecture
i am very much interested to join summer research fellowship in this particular area i.e in nanotechnology. Sir, can you please help me in this matter. i am presently doing my btech 1st year , will be 2nd year in a month.

Mon, 04/14/2008 - 20:51 (Reply to #5)

It is certainly a good idea

It is certainly a good idea to start doing some research on this, given your enthusiasm. However, I personally can't help much on this for you. Two pieces of advice may be helpful for you though:

1. If you want to find the groups who are doing research on quantum dots, look for the publications in e.g. science or nature. (You may then ask them if they want summer students)

2. If you are serious about a career in the field of nano-technology, firm understanding of quantum mechanics is crucial.

Tue, 04/15/2008 - 15:21 (Reply to #6)

summer research

thankyou sir for giving your valuable advice. if you come across any such oppurtunities please do not forget to inform me. i don't have any idea about it right now.
thank you ,and i hope you would do it for me.

Tue, 04/29/2008 - 17:06

entanglement

what is entanglement?
how can a single particle exist in different states at same time?
and how can we control the state of one particle by controlling the state of other?
how is parallel processing possible in quantum computers?