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41 posts tagged with quantummechanics.

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## What is Probability?

The Trouble with Quantum Mechanics - "The introduction of probability into the principles of physics was disturbing to past physicists, but the trouble with quantum mechanics is not that it involves probabilities. We can live with that. The trouble is that in quantum mechanics the way that wave functions change with time is governed by an equation, the Schrödinger equation,

*that does not involve probabilities*. It is just as deterministic as Newton's equations of motion and gravitation. That is, given the wave function at any moment, the Schrödinger equation will tell you precisely what the wave function will be at any future time. There is not even the possibility of chaos, the extreme sensitivity to initial conditions that is possible in Newtonian mechanics. So if we regard the whole process of measurement as being governed by the equations of quantum mechanics, and these equations are perfectly deterministic,*how do probabilities get into quantum mechanics?*" (via) [more inside]## Constrained Synthesis

Bitmap & tilemap generation from a single example with the help of ideas from quantum mechanics. [more inside]

## Theories of Everything, Mapped

Explore the deepest mysteries at the frontier of fundamental physics, and the most promising ideas put forth to solve them. A map of the frontier of fundamental physics built by interactive developer Emily Fuhrman.

## Reinventing Science

Science "explains things" in various ways. You can start with initial conditions, and apply laws of motion (classical kinematics). Or you can predict things via evolving probabilities (quantum mechanics). Or you can find emergent laws (thermodynamics). Or ... - There are many different

*modes of explanation*. Recently, David Deutsch invented a new one: Constructor Theory. [more inside]## The Big Bang Is Hard Science. It Is Also a Creation Story.

Even with its explanatory power, Big Bang theory takes its place in a long line of myths [more inside]

## The observer at the end of time: Of immortal watchers and imaginary data

In a Multiverse, What Are the Odds? "Testing the multiverse hypothesis requires measuring whether our universe is statistically typical among the infinite variety of universes. But infinity does a number on statistics." (previously) [more inside]

## I'm leaving my body to science, not medical but physics

Let's Talk About Science is a blog devoted to discussing the world of science and technology communication with clear, beginner-friendly language, written and compiled by nanoscientist/physicist Jessamyn Fairfield and science educator ErinDubitably. [more inside]

## Time : a flat circle :: Consciousness : a state of matter?

"While the problem of consciousness is far from being solved, it is finally being formulated mathematically as a set of problems that researchers can understand, explore and discuss.

Today, Max Tegmark, a theoretical physicist at the Massachusetts Institute of Technology in Cambridge, sets out the fundamental problems that this new way of thinking raises. He shows how these problems can be formulated in terms of quantum mechanics and information theory. And he explains how thinking about consciousness in this way leads to precise questions about the nature of reality that the scientific process of experiment might help to tease apart.

Tegmark’s approach is to think of consciousness as a state of matter, like a solid, a liquid or a gas. 'I conjecture that consciousness can be understood as yet another state of matter. Just as there are many types of liquids, there are many types of consciousness,' he says."

Today, Max Tegmark, a theoretical physicist at the Massachusetts Institute of Technology in Cambridge, sets out the fundamental problems that this new way of thinking raises. He shows how these problems can be formulated in terms of quantum mechanics and information theory. And he explains how thinking about consciousness in this way leads to precise questions about the nature of reality that the scientific process of experiment might help to tease apart.

Tegmark’s approach is to think of consciousness as a state of matter, like a solid, a liquid or a gas. 'I conjecture that consciousness can be understood as yet another state of matter. Just as there are many types of liquids, there are many types of consciousness,' he says."

## Einstein reportedly bitter about not getting spooky action at a distance

Researchers at the Kavli Institute of Nanoscience at the Delft University of Technology in the Netherlands have developed a technique for quantum data teleportation that uses deterministic methods to offer one hundred percent accuracy. Previous methods only worked reliably one in every 100 million attempts. [more inside]

## My God, it's full of... everything

Revelations in the field of quantum physics have resulted in the discovery of the Amplituhedron, a jewel-like higher dimensional object whose volume elegantly predicts fundamental physical processes that took the brilliant Dr. Richard Feynman hundreds of pages of abstruse mathematics to describe.
The theoretical manifold not only enables simple pen-and-paper calculation of physics that would normally require supercomputers to work out, but also challenges basic assumptions about the nature of reality -- forgoing the core concepts of locality and unitarity and suggesting that space and time are merely emergent properties of a timeless, infinitely-sided "master amplituhedron," whose geometry represents the sum total of all physical interactions.

**More:**The 152-page source paper on arXiv [PDF] - Lead author Nima Arkani-Hamed's hour-long lecture at SUSY 2013 - Scans of Arkani-Hamed's handwritten lecture notes - A far more detailed lecture series "Scattering Without Space Time": one, two, three - Arkani-Hamed previously on MeFi - A hot-off-the-presses Wikipedia page (watch this space)## conservation of information

A Black Hole Mystery Wrapped in a Firewall Paradox - "A paradox around matter leaking from black holes puts into question various scientific axioms: Either information can be lost; Einstein's principle of equivalence is wrong; or quantum field theory needs fixing." [more inside]

## Why Philosophers Should Care About Computational Complexity

"One might think that, once we know something is computable, how efficiently it can be computed is a practical question with little further philosophical importance. In this essay, I offer a detailed case that one would be wrong. In particular, I argue that computational complexity theory---the field that studies the resources (such as time, space, and randomness) needed to solve computational problems---leads to new perspectives on the nature of mathematical knowledge, the strong AI debate, computationalism, the problem of logical omniscience, Hume's problem of induction, Goodman's grue riddle, the foundations of quantum mechanics, economic rationality, closed timelike curves, and several other topics of philosophical interest. I end by discussing aspects of complexity theory itself that could benefit from philosophical analysis."

## direct realism

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]

## 2012 Nobel Prize in Physics

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

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.

**. 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:***may soon allow us to build computers with virtually limitless capabilities*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.

## noncommutative balls in boxes

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]

## The Strangest Man

*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.*[1939] [more inside]

## Experimental delayed-choice entanglement swapping.

*"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)

## More Evidence Found for Quantum Physics in Photosynthesis

Previous experiments have hinted at the connection... Physicists have found the strongest evidence yet of quantum effects fueling photosynthesis.
Multiple experiments in recent years have suggested as much, but it’s been hard to be sure. Quantum effects were clearly present in the light-harvesting antenna proteins of plant cells, but their precise role in processing incoming photons remained unclear.
In an experiment published Dec. 6 in Proceedings of the National Academy of Sciences, a connection between coherence — far-flung molecules interacting as one, separated by space but not time — and energy flow is established.
“There was a smoking gun before,” said study co-author Greg Engel of the University of Chicago. “Here we can watch the relationship between coherence and energy transfer. This is the first paper showing that coherence affects the probability of transport. It really does change the chemical dynamics.”

## Fabric of the Cosmos

Brian Greene's Fabric of the Cosmos is online in its entirety on NOVA's website, in four one-hour episodes. Time, Space, Quantum Mechanics, Multiverses.

## I still don't get it

Physicists have managed to observe light behaving both as a particle and wave in the same double-slit experimental condition, by means of a new method to weakly observe a particle's momentum. This article in Nature summarizes the results in non-mathematical terms. [more inside]

## Finite formula found for partition numbers

New math theories reveal the nature of numbers [1,2] - "We prove that partition numbers are 'fractal' for every prime. These numbers, in a way we make precise, are self-similar in a shocking way. Our 'zooming' procedure resolves several open conjectures, and it will change how mathematicians study partitions." (/.|via) [more inside]

## Does the Past Still Exist?

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]

## Quantum weirdness at the large scale

Scientists supersize quantum mechanics. "A team of scientists has succeeded in putting an object large enough to be visible to the naked eye into a mixed quantum state of moving and not moving."

## Grand Unification may be occurring near your vital organs.

## Genuine random numbers, generated by radioactive decay

*HotBits*is an Internet resource that brings

*genuine*random numbers, generated by a process fundamentally governed by the inherent uncertainty in the quantum mechanical laws of nature, directly to your computer in a variety of forms.

*HotBits*are generated by timing successive pairs of radioactive decays detected by a Geiger-Müller tube interfaced to a computer. (Warning: random sounds.)

## Time Travel gives you a headache...

The new Star Trek movie is both canon and a (partial) reboot. Screenwriter Roberto Orci explains using canon examples - and a discussion of the many-worlds interpretation of quantum mechanics. [more inside]

## How Much

Quantum of culture. Terminology from quantum theory shows up frequently in art, films, poetry and sculpture. Robert P. Crease gauges the impact of quantum mechanics on popular culture. [Via]

## Reality

The Reality Tests. "A team of physicists in Vienna has devised experiments that may answer one of the enduring riddles of science: Do we create the world just by looking at it?"

## Quantum Mechanics: Myths and Facts

*Quantum Mechanics: Myths and Facts*(pdf), a recently-updated paper on the Cornell arXiv peer-review site. By Hrvoje Nikolić of the Rudjer Bošković Institute in Croatia. [more inside]

## The Mechanical Universe on Demand

The Mechanical Universe...and Beyond is a critically-acclaimed series of 52 thirty-minute videotape programs covering the basic topics of an introductory university physics course. This well produced and highly informative 52 episode series, hosted by David Goodstein of Caltech, is available as Video on Demand (Note: simple registration required to view videos). [more inside]

## Does this mean we get to fly?

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.

## Physics simulators. Lots of physics simulators.

PhET - Physics Education Technology offers this astoundingly large library of online physics simulations. Play orbital billiards. Land on a cheesy moon. Experiment with sound. Or try more advanced quantum physics simulators. Still bored? Try the "cutting edge" catagory. Here's the complete index. (Warnings: Frames, Flash, Javascript, Java applets, graphics, sound, quantum timesuck.)

## String up the mobius chains.

Happy Anniversary, Quantum Mechanics! "On December 14, 1900, Max Planck presented experimental data at the German Physical Society and said that it could best be explained if energy existed in discrete packets, which he called "quanta." It was on that day that the field of Quantum Physics was effectively born. I call it QM Day and it's the unofficial start of the Agnostica Holiday!"

## QuIET is the New Loud

University of Arizona physicists have discovered how to turn single molecules into working transistors. The research could result in much smaller, more powerful computers and other devices with the ability to process many more channels of high-resolution audio and video than current products can manage. The abstract is available in PDF.

## Don't give me any of that intelligent life crap, just give me something I can blow up

For a star as big as our universe the calculated vacuum energy inside its shell matches the value of dark energy seen in the universe today. "It's like we are living inside a giant dark energy star" say two physicists and their collegues. Dark energy stars may do away with the concept of black holes.
(also seen recently on )

## Or did I just BLOW YOUR FUCKING MIND?!

We've talked about quantum computation a few times before, but how much do we really know? Metafilter, instruct thyself. Don't forget to learn some advanced probability and computational complexity (Scott Aaronson has more).
Whoa, that's a lot o' learning, so let's so check out the much easier, and much cooler "sleeping puppy" experiment. I can only dream that will help break quantum mechanics' association with animal abuse. Then, there's the Free Will Theorem that just came out (some discussion on it) and another paper with a new look at an old problem. The latter describes another way of solving ye olde, super importanto Einstein-Podolsky-Rosen paradox using the relational interpretation of quantum mechanics (lots of discussion running around). Whew. We don't need the crackpot ramblings of What the #$*! Do We Know? when we've got real physics to keep us up at night. So, who wants to become a physicist? (t'Hooft has some thoughts for those who want to go theoretical.)

## "Have you tried turning it off and on again?"

## Quantum Darwinism

Natural selection acts on the quantum world. "Objective reality may owe its existence to a 'darwinian' process that advertises certain quantum states."

## Yowza

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?

## Confuse-a-Cat, Ltd.

Schrödinger's famous theoretical kitty is one step closer to being/not being validated, revisiting some old conundrums and bright ideas.

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