The Nature of Computation -
Intellects Vast and Warm and Sympathetic: "I hand you a network or graph, and ask whether there is a path through the network that crosses each edge exactly once, returning to its starting point. (That is, I ask whether there is a 'Eulerian' cycle.) Then I hand you another network, and ask whether there is a path which visits each node exactly once. (That is, I ask whether there is a 'Hamiltonian' cycle.) How hard is it to answer me?" (
via)
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posted by kliuless
on Dec 1, 2012 -
19 comments
The 2012 Nobel Prize in Physics has
been awarded to Serge Haroche (France) and David Wineland (US) for discovering ways to measure and manipulate quantum particles, a discovery which
many are suggesting may soon allow us to build computers with virtually limitless capabilities. The Nobel press release provides a layman friendly
PDF summary of the research and its potential applications, as well as a less layman friendly PDF with additional
scientific background information. The press release cites two older Scientific American articles for further reading, and the magazine has made these articles available to read free online for the next 30 days:
Monroe, C. R. and Wineland, D. J. (2008) Quantum Computing with Ions, Scientific American, August.Yam, P. (1997) Bringing Schrödinger’s Cat to Life, Scientific American, June.
posted by dgaicun
on Oct 15, 2012 -
51 comments
Morton and Vicary on the Categorified Heisenberg Algebra - "In quantum mechanics, position times momentum does not equal momentum times position! This sounds weird, but it's connected to a very simple fact. Suppose you have a box with some balls in it, and you have the magical ability to create and annihilate balls. Then there's one more way to create a ball and then annihilate one, than to annihilate one and then create one. Huh? Yes: if there are, say, 3 balls in the box to start with, there are 4 balls you can choose to annihilate after you've created one but only 3 before you create one..."
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posted by kliuless
on Jul 21, 2012 -
78 comments
"Using four photons, we can actively delay the choice of measurement on two of the photons into the time-like future of the registration of the other two photons. This effectively projects the two already registered photons onto one of two mutually exclusive quantum states in which the photons are either entangled (quantum correlations) or separable (classical correlations). This can also be viewed as ‘quantum steering into the past’." (
arXiv,
Nature Physics,
Ars Technica)
posted by jeffburdges
on Apr 25, 2012 -
80 comments
Physicists have 'solved' mystery of levitation Professor Ulf Leonhardt and Dr Thomas Philbin, from the University of St Andrews in Scotland, have worked out a way of reversing ... the
Casimir force, so that it repels instead of attracts. Their discovery could ultimately lead to frictionless micro-machines with moving parts that levitate. But they say that, in principle at least, the same effect could be used to levitate bigger objects too, even a person.
posted by MythMaker
on Aug 19, 2007 -
30 comments
