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
) [more inside]
posted by kliuless
on Dec 1, 2012 -
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 -
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..." [more inside]
posted by kliuless
on Jul 21, 2012 -
The trend of mathematics and physics towards unification provides the physicist with a powerful new method of research into the foundations of his subject, a method which has not yet been applied successfully, but which I feel confident will prove its value in the future. The method is to begin by choosing that branch of mathematics which one thinks will form the basis of the new theory. One should be influenced very much in this choice by considerations of mathematical beauty.
 [more inside]
posted by smcg
on Apr 28, 2012 -
"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’."
, Nature Physics
, Ars Technica
posted by jeffburdges
on Apr 25, 2012 -
Is our present defined by decisions we make in the future?
And maybe we don't know who killed JFK because the universe hasn't decided yet. A Huffington Post science blogger discusses the nature of history from a quantum perspective. To quote Stephen Hawking, "The histories of the universe depend on what is being measured, contrary to the usual idea that the universe has an objective observer-independent history." [more inside]
posted by GnomeChompsky
on Aug 20, 2010 -
The physicist Shariah Afshar has used a beautifully simple experiment
, which no-one seems to have thought of before, to disprove Bohr's principle of complementarity
, something which has been pretty much unchallenged for 80 years. He may also have gone some way towards showing that there is no such thing as a photon, and that Einstein's Nobel prize should be revoked. So, big stuff. What do you physicists think?
posted by Pretty_Generic
on Jul 29, 2004 -