Quantum Tech: Examples & Details

[roy5995]

What are examples of quantum technology? and what are the detail of them?

 

[chroot]

Every semiconductor-based electronic device ever built. Your computer, for example.

- Warren

 

[roy5995]

Does anyone know of a website of an enyclopedia were i can find some info on this topic?

 

[vanesch]

"quantum technology"

Although one often hears these answers (lasers, semiconductors, etc...) in fact I think they are a bit overselling the quantum aspect.
In fact, most of these technologies are based upon what's called "semiclassical" models, and quantum mechanics is only responsible for a few parameters in these applications. For example, in semiconductors, once you have the effective masses and mobilities of electrons and holes, you calculate transistors with them as if these were classical fluids.
In laser applications, you only need to know the 3 (in fact 2) coefficients of stimulated emission, absorption and spontaneous emission in order to describe the medium, and then you use classical optics to consider the laser.
Of course, it is a quantum world, and you can also say that structural stability of building materials are quantum applications because ultimately that's what's determines their properties under stress, but once you have the elastic parameters of steel, you do a classical calculation, and I don't see much difference with lasers or semiconductors in most of the applications.
Apart from scientific applications, it is hard to come up with true quantum applications (that is: you NEED the quantum formalism to build the application, and no empirical parameters would allow you to circumvent this).
Say: superconductivity, a typical quantum phenomenon. Well, it was empirically achieved before the advent of quantum theory !
True quantum applications are probably: the Josephson junction, B-E condensates, neutron diffraction, and indeed more sophisticated applications of semiconductors such as semiconductor lasers. And then a big part of computational chemistry and pharmacology where molecular models are built.

cheers,
Patrick.

 

[slyboy]

Quantum Technology usually refers to the physical devices being used to try and perform quantum communication, quantum cryptography and quantum computing. A few of these were mentioned in the last posting.

A good source on this kind of stuff is http://www.qubit.org

Note that quantum cryptography can now be bought "off the shelf" from a company in Geneva called GAP Optique.

The book "Quantum Technology" by Gerald Milburn is a reasonably good attempt to explain this stuff to a general audience. (It has some problems though. For example, it goes through great pains to introduce what complex numbers are, but it assumes you know what the "twin paradox in special relativity" is. I would say that the best book on this subject for a general audience has probably not been written yet.)

 

[Kurdt]

Probably the ultimate piece of quantum technology I believe would be a quantum computer. Hopefully they are not that far off the horizon, and if you think ordinary IT has developed considerably in the past ten years consider how IT could change with the power of a quantum computer.

 

[roy5995]

can someone please explain what quantum really means?

I've read different things on it but I'm not sure that i really understand.

 

[spdf13]

I'm working on a single atom quantum teleprotation experiment right now. It involves being able to "teleport" the exact quantum state of an isolated atom to another via an entangled photon source.

When you ask what quantum means, the best and most simple explanation I can give is its the physics of probability. When you deal with small particles you find that they can be in a combination of states as opposed to being something completely identifiable like a macroscopic particle. For example, think about the state of a coin. It can either be in the heads up position, or the heads down position, but nothing more. A quantum particle, however, could be in the heads up position, the heads down position, and a combinaition of the heads up and heads down position.

If you make a measurement on the particle that is in a combinaitioin of the heads up and heads down state, you will only get one answer, either heads up or heads down and from that time on the particle will stay in this state until the particle is disturbed. This is known as the collapse of the particles wave function.

Of course this is a very simplified (and not the greatest) definition of quantum mechanics. There is a lot more to it, but ideas of quantum mechanics began with these ideas (instead of heads and tails, it was sending particles through a double slit experiment and trying to figure out if the particle went through slit 1 or slit 2). I hope I haven't confuse you more.

 

[roy5995]

i still don't understand.

does quantum technology exist today, or are they still reseaching it.
is a computer an example of quantum technology. If so, in what way?

Is teleportation an example of quantum communication?

i can't seem to find any info on quantum technology when i search the web, most sites seem to be company sites not information sites, and encylopedias don't have very much much info on this topic. Does any know of a good site for quantum technology (that is general, and doesn't get very specific when calculations and other things that i don't understand) and should i be searching something different?

 

[Jimmy]

Originally posted by roy5995
can someone please explain what quantum really means?

I've read different things on it but I'm not sure that i really understand.

quantum: The smallest discrete amount of any quantity (plural: quanta).

quantum mechanics: The laws of physics that apply on very small scales. The essential feature is that energy, momentum, and angular momentum as well as charges come in discrete amounts called quanta.

If you're interested, I would suggest reading about Max Planck and his solution to what was called The Ultraviolet Catastrophe

Planck wasn't comfortable with the idea that energy is absorbed and emitted in discrete units called quanta and thought his ideas would be proved false by later theories. Instead, it was used later to describe the photoelectric effect, for which Einstein won a Nobel Prize, and later evolved into the science of Quantum Mechanics.

 

[Jimmy]

Originally posted by roy5995
i still don't understand.

does quantum technology exist today, or are they still reseaching it.
is a computer an example of quantum technology. If so, in what way?

I'm not sure about the details of quantum computing so I won't try to discuss something I really don't have knowledge on.

As far as existing quantum devices, I think the Tunnel Diode is a good example.

http://www.nobel.se/physics/laureates/1973/presentation-speech.html

http://www.tpub.com/neets/book7/26a.htm

Because a tunnel diode has a very fast response time to inputs, it is almost exclusively used in microwave technology. It offers low-noise amplification at those frequencies.

Probably not the exciting answer you were maybe looking for but it is an example of a device which was designed based on quantum principles.

 

[Kurdt]

If you search for a scanning tunnelling electron microscope, that should return some useful results. It is an application of Quantum theory in the most complete sense I believe and one of the only examples that uses no other theory coupled with it in the world today. Thats as far as I know anyway somebody may be able to put me straight.

 

[roy5995]

Thanks, i think that i understand a little more now.


But what could be some consequences of quantum technology

 

[Jimmy]

Here's a link to a paper entitled An Introduction to Quantum Computing for Non-Physicists by Eleanor Rieffel and Wolfgang Polak.

I ran across this paper early last year and thought you might be interested in checking it out. Took awhile for me to find it again. I lost my own copy when my hard drive crashed...

Here is the abstract:

Richard Feynman's observation that quantum mechanical effects could not be simulated efficiently on a computer led to speculation that computation in general could be done more efficiently if it used quantum effects. This speculation appeared justified when Peter Shor described a polynomial time quantum algorithm for factoring integers.
In quantum systems, the computational space increases exponentially with the size of the system which enables exponential parallelism. This parallelism could lead to exponentially faster quantum algorithms than possible classically. The catch is that accessing the results, which requires measurement, proves tricky and requires new non-traditional programming techniques.
The aim of this paper is to guide computer scientists and other non-physicists through the conceptual and notational barriers that separate quantum computing from conventional computing. We introduce basic principles of quantum mechanics to explain where the power of quantum computers comes from and why it is difficult to harness. We describe quantum cryptography, teleportation, and dense coding. Various approaches to harnessing the power of quantum parallelism are explained, including Shor's algorithm, Grover's algorithm, and Hogg's algorithms. We conclude with a discussion of quantum error correction.

Interesting excerpt:

Classically, the time it takes to do certain computations can be decreased by using parallel processors. To achieve an exponential decrease in time requires an exponential increase in the number of processors, and hence an exponential increase in the amount of physical space needed. However, in quantum systems the amount of parallelism increases exponentially with the size of the system. Thus, an exponential increase in parallelism requires only a linear increase in the amount of physical space needed. This effect is called quantum parallelism [Deutsch and Jozsa 1992].

There is a catch, and a big catch at that. While a quantum system can perform massive parallel computation, access to the results of the computation is restricted. Accessing the results is equivalent to making a measurement, which disturbs the quantum state. This
problem makes the situation, on the face of it, seem even worse than the classical situation; we can only read the result of one parallel thread, and because measurement is probabilistic, we cannot even choose which one we get.

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