Quantum Control - Science topic

Quantum Computer is nothing more than a big bubble and will not work at all. Please study the literature carefully before invesingt in a black hole!

Dear Saeed Haddadi, Let me tell you that, in general, mathematical criteria that identify (directly or indirectly) "mathematical entanglement" do not necessarily identify "physical entanglement." A specific example of this is found in the article: "A case of spurious quantum entanglement originated by a mathematical property with a non-physical parameter", by Bulnes and Bonk.

As pointed out above, the fundamental difference between Quantum and classical mechanics is the algebra of the obervable operators. Classical mechanics in the Hilbert space was introduced by Koopman and von Neumann.

In this way, the classical equation of motion is linear and very similar to Liouville's equation. The price to pay for having a linear equation of motions is that it becomes a partial differential equation, which is in most cases more difficult to solve. This represents an important challenge at the time to apply control. Nevtheless, it is possible as shown in one of my preprint publications.

Thank you Shuyu Zhou. I will have a look at it. I also found theoretical paper by Michael W. Jack and M. Yamashita where they analyze decay rate of the three-body losses from three-body correlation function at different lattice depth.

The link from Zhiyong Geng is a good place to start, and there are quite a few good reviews and textbooks that can be easily found.  Despite what Saeed Dashtban has commented on, quantum control is NOT only quantum computing - there is a fair bit more to it than that (although there is certainly an overlap with certain problems in quantum computing). Another good place to check out is the special issue from 2009 (edited by Herschel Rabbitz, one of the fathers of the field) in New Journal of Physics: Focus on Quantum Control http://iopscience.iop.org/1367-2630/11/10/105030. Should all be Open Access too

So in its simplest form, quantum control is the extension of classical control problems to the quantum space.  The quantum aspect can take any number of (not necessarily mutually exclusive) different flavours.  For example, the system being controlled could be a quantum system that is controlled by classical fields.  This was the case for some of the first quantum control problems of pumping rubidium atoms into Rydberg states, and is also the case for much of the liquid phase NMR work.  The system could be controlled via quantum feedback, for example in the creation of non-classical states of a cavity by measurement back action.

Some aspects that are usually common to quantum control include: typically intermediate states are non-classical states, and there is only incomplete information about the state of the system to avoid deleterious measurement back action.  The latter fact usually means that von Neumann measurements are prohibited, and some kind of weak measurement process may be required.  But even this rule is not hard and fast.

Hope this helps

I found some papers..... here is one reference for review article on Back action evading measurement....every thing is discussed in this review article.....whosoever are interested may go through this paper....

Another one is  V. B. Braginsky and Y. I. Vorontsov and K.S. thorne,science 209, 547(1980)

Thanks

Regards

Anil

As far as I know, simple correlation between two states isn't enough to form an entangled state.

One of the criteria of entanglement points out that if one can factorize the state vector (for example, |phi>=|phi_1>|phi_2>), then the state (|phi>) isn't entagled. In this case the subsystems |phi_1> and |phi_2> are physically "independent", for one can examine the properties of each factor (|phi_1>, |phi_2>) on its own, isolated, and it wouldn't affect the other factor. (I know the explanation isn't accurate, but it can help in some way to understand the whole thing).

Of course there may still be a correlation between them (for example, |phi_1> is set to downward spin, and |phi_2> is set to upward, so in general state |phi> both spins kind of come together with that structure and evolve accordingly to it), but it has nothing to do with quantum properties or interactions.

There was some argument one time (e.g. in this article: http://cds.cern.ch/record/142461/files/198009299.pdf) that on classical level you can see such correlations everywhere. You can send one sock to one of your friends, and another sock (from the same pair) to another. When one of them looks at the received sock, he would know exactly which colour has the sock sent to another friend. But obviously it is not due to some quantum entanglement.