Wednesday, 18 February 2009

Quantum Dots and Spintronics for Quantum Computing and Communication

It is proposed that an entirely new form of information processing, namely quantum computing, could be possible[1] if the states of electron spins in a given solid can be synthesised (or created), manipulated and measured at the single-quantum level. A spin-quantum dot architecture for a quantum computer, thereby indicating a variety of first generation nanostructures, is reviewed. A spin filter and spin detection mechanism [3] at the single-spin level which can be used for read-in and read-out in conventional as well as in quantum computer gates is discussed. Addressing the feasibilty of quantum communication with entangled electrons [4,5], Einstein-Podolsky-Rosen pairs are discussed.

A way of using Quantum Dots (QD) would be to look at it as a producer of electric charge and use the same electric charge as a qubit. Semiconductor QD's can serve as 3-Dimensional boxes with electrostatic potentials which confine charge quanta. Unfortunately, uncontrolled distant charged motion leads to dephasing. Also scattering reactions such as those triggered by phonon interactions cause coherence times to be relatively short for charge states.

Obtaining of Entangled Photons from Quantum Dots in a cavity for usage in Quantum Computation & Communications is steadily growing in popularity. Some progress has been done in this area [ e.g. Bensaon et. al, 2000; Stace et. al,2003; benycouf et. al., 2004; Kumar et. al., 2004]. It is also expected that there will be other such sources soon. A very demanding but also very promising area, while implementing Quantum Communication, is generating fluorescence photons by manipulating trapped atoms or ions. This is closely connected to Quantum Computation with trapped ion systems and cavity QED systems. A reference source for these techniques is, for example, "Focus On Single Photons On Demand " by Grangier et. al. 2004.

Teleportation of single qubits have already been achieved by multiple groups in laboratories using entangled photons ( for e.g., see ref. Galindo et. al below).

[1] D. Loss, D.P. DiVincenzo, Phys. Rev. A 57 (1998) 120; cond-mat/9701055.
[2] G. Burkard, H.A. Engel, D. Loss, cond-mat/0004182 (Review).
[3] P. Recher, E. V. Sukhorukov, D. Loss, cond-mat/0003089.
[4] D. Loss, E. Sukhorukov, Phys. Rev. Lett. 84, 1035 (2000).
[5] G. Burkard, D. Loss, E. Sukhorukov, to appear in Phys. Rev. B RC, cond-mat/9906071.

[6] A. Galindo and M.A. Martin-Delgado: Infomration and Computation: Classical and Quantum Aspects, 74:347-423, 2002

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Breakfast At Serengeti

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The Ngorongoro Family

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Tabloid Time: The Aliens Are a'Landing ?!.. ;-)

At the risk of being ridiculed and being labelled a freak, I shall like to draw everyone's attention to the following recent events....If you watch the videos then turn on the sound for the commentary...

Fireball across Ausin, Texas (16th Feb 2009). According to BBC, apparently, its NOT debris from a recent satellite collision...:

Same in Idaho in recent times. NO meteor remains found yet:

Exactly same in Sweden:

This was recorded on 25th Feb 2007 in Dakota, US:

This year has seen three of the spookiest UFO videos surface, with people in India, Mexico and even in space, NASA, spotting things they couldn't explain:

CHECK out this one on 24th Januray, 2009 in Argentina close to Buenos Aires:
You tube:
Press Coverage

AND Lastly, and more importantly, from Buzz Aldrin on Apollo 11 :

Heh?! Don't know how authentic these news are... don't even know if these are UFO's or meteors or ball lightning or something else. But, if meteors, then where are the meteorites ? However, I see no reason why life cannot exist in other planets and why they could not be sneaking around here :-) . I for one, have long suspected some of my relations to be space aliens or at least X-people from X-files :-)

I am waiting for a job on an Alien spaceship myself. :-)

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Serengeti Shall Never Die

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Wildebeeste Calf starts running only 5 min. after being born. CLICK on the pitcture to view Slideshow