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Sat Apr 5 09:36:55 UTC 2008

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From: the physics arXiv blog <howdy at arxivblog.com>
Date: Fri, 4 Apr 2008 16:38:52 -0500 (CDT)
To: eugen at leitl.org
Subject: the physics arXiv blog
Reply-To: the physics arXiv blog <howdy at arxivblog.com>

[1]the physics arXiv blog

   [2]Qutrit breakthrough brings quantum computers closer

   Posted: 04 Apr 2008 12:19 AM CDT

   [3]Toffoli gate 

   The folks playing with quantum computers have been claiming for years
   that their gadgets will one day make today's supercomputers look like
   quivering lumps of jelly. But so far, their computers have yet to
   match the calculating prowess of a 10-year old with ADHD.

   The most exciting work so far has been on universal quantum logic
   gates, the building blocks of any computer. A number of groups have
   built and demonstrated these and one team even took their gates for
   the computing equivalent of a run round the block by factorising the
   number 15.

   The trouble is that, to do anything useful with universal quantum
   gates, you need at least dozens and preferably hundreds of them, all
   joined together. And because of various errors and problems that creep
   in, that's more or less impossible with today's technology.

   Which is why a breakthrough by an Australian group led by Andrew White
   at the University of Queensland is so exciting. They have built and
   tested quantum logic gates that are vastly more powerful than those
   that have gone before by exploiting the higher dimensions available in
   in quantum mechanics. For example, a qubit can be encoded in a
   photon's polarisation. But a photon has other dimensions which can
   also be used to carry information, such as its arrival time, photon
   number or frequency. By exploiting these, a photon can easily be used
   as a much more powerful three level system called a qutrit.

   This is how the Ozzie team have exploited the idea: during a
   computation, their gates convert qubits into qutrits, process the
   quantum information in this more powerful form and then convert it
   back into qubits. All using plain old vanilla optics.

   That allows a dramatic reduction in the number of gates necessary to
   perform a specific task. Using only three of the higher dimension
   logic gates, the team has built and tested a Toffoli logic gate that
   could only have been constructed using 6 conventional logic gates. And
   they say that a computer made up of 50 conventional quantum logic
   gates could be built using only 9 of theirs.

   That's a significant reduction. What's more, they reckon that these
   kinds of numbers are possible with today's linear optics technology.

   That means these guys are right now bent over an optical bench with
   screwdrivers and lens cloths at the ready, attempting to build the
   world's most powerful quantum computer. We may see the results-a
   decent factorisation perhaps-within months.

   Could it be that Australia is about to become the center of the
   quantum computing world?

   Ref: [4]arxiv.org/abs/0804.0272: Quantum Computing using Shortcuts
   through Higher Dimensions

   [5][arXivblog?i=razenA] 
   [6][arXivblog?i=T4LPuLG] [7][arXivblog?i=IdEXGiG]
   [8][arXivblog?i=RWgcOOg] [9][arXivblog?i=OBotbZG]
   [10][arXivblog?i=YdcxnQg] [11][arXivblog?i=o2O5YjG]
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References

   1. http://arxivblog.com/
   2. http://feeds.feedburner.com/~r/arXivblog/~3/263767438/
   3. http://arxivblog.com/wp-content/uploads/2008/04/toffoli-gate.jpg
   4. http://arxiv.org/abs/0804.0272
   5. http://feeds.feedburner.com/~a/arXivblog?a=razenA
   6. http://feeds.feedburner.com/~f/arXivblog?a=T4LPuLG
   7. http://feeds.feedburner.com/~f/arXivblog?a=IdEXGiG
   8. http://feeds.feedburner.com/~f/arXivblog?a=RWgcOOg
   9. http://feeds.feedburner.com/~f/arXivblog?a=OBotbZG
  10. http://feeds.feedburner.com/~f/arXivblog?a=YdcxnQg
  11. http://feeds.feedburner.com/~f/arXivblog?a=o2O5YjG
  12. http://feeds.feedburner.com/~f/arXivblog?a=Hn1Dfog
  13. http://feeds.feedburner.com/~f/arXivblog?a=ZtC9ttG
  14. http://arxivblog.com/
  15. http://www.feedburner.com/fb/a/emailunsub?id=8632699&key=kesJ612ZsV
  16. http://feeds.feedburner.com/arXivblog
  17. http://feeds.feedburner.com/arXivblog

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Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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