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Hardware Science

Toward On-Chip Quantum Computing 48

Darum writes "Researchers are working to create devices built on the rules of quantum mechanics. These would allow quantum computers which can do certain problems such as prime number factorization for decryption and simulation of complex systems (such as protein folding) in a tiny fraction of the time required on classical computers. Two papers appearing in this week's Nature raise the possibility of developing such quantum devices by manipulating light signals by semiconductor quantum dots. One of the approaches bases on photonic crystals, which seem pretty ideal for on-chip integration of a full set of computation components. One of the study's authors put up a good background story of this work on CVitae. The author discusses the potential simplicity and microchip scalability of these two quantum-dot 'light switch' systems. This could be good news for quantum information processing and ultra-secure long-distance communication applications. It could also allow all-optical signal processing, which has long been a holy grail for optical communications and could allow extremely fast and low-power optical interconnects."
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Toward On-Chip Quantum Computing

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  • by Jimminey Cricket ( 224848 ) on Saturday December 15, 2007 @12:29PM (#21709020)
    A free version of the other article (using microdisks instead of photonic crystals) is available on the arXiv: []
    Reading the two papers careful, it turns out the photonic crystal paper is only at the "onset" of strong coupling (the decay rate is still about 2x faster than the coherent light-matter coupling rate) while the microdisk paper is actually strongly coupled (the coherent coupling rate is faster than any decay or dephasing).
  • by exp(pi*sqrt(163)) ( 613870 ) on Saturday December 15, 2007 @01:53PM (#21709642) Journal
    I would never hold it against someone that they know nothing about quantum computers or nothing about games. But you have chosen to hold forth on these subjects in response to someone's questions without taking any note of the fact that you haven't the faintest clue what you are talking about.

    > A variable will still be a variable

    This is completely incorrect. The concept of a variable radically changes in a quantum computer because you are allowed superposed states.

    > I'm not aware of quantum mechanics introducing any new operators

    What in heaven's name are you imagining? Of course quantum mechanics introduces new operators. It completely turns classical mechanics on its head and introduces concepts that make no sense in a classical framework. Here's an example [] of a specifically quantum operator.

    TSP is NP-hard, and quantum computers don't, as far as we know, make NP-hard problems solvable in polynomial time. Grover's algorithm [], however, does allow you to search a database of N items in time sqrt(N) so it could provide many speedups to familiar algorithms.

    > Chess, aside from being Zero Sum

    Are you *trying* to look like an ignoramus? Zero-sumness has absolutely nothing to do with chess. Zero-sumness is about the payoff you get from game of incomplete information. It has nothing to do with the strategy you should use in a game of complete information like chess. I guess you just want to sound smart by throwing around technical terms you don't grasp.

    > seriously doubt there is one unbeatable strategy, since a player cannot control the first piece the other player moves.

    Woah! Where are you getting this stuff from? Are you just making stuff up as you write it? It's incredible. Whether or not a game has a winning strategy has nothing to do with whether you can control the other player's first move.

    As I say, there's nothing wrong with not knowing stuff. But spouting garbage in response to someone's genuinely inquiring questions is nothing short of obnoxious and just serves to lower the signal to noise ratio on Slashdot.

"The eleventh commandment was `Thou Shalt Compute' or `Thou Shalt Not Compute' -- I forget which." -- Epigrams in Programming, ACM SIGPLAN Sept. 1982