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35 posts tagged with physics *and* quantum.

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## Pilot-wave theory “seems to me so natural and simple..."

This idea that nature is inherently probabilistic — that particles have no hard properties, only likelihoods, until they are observed — is directly implied by the standard equations of quantum mechanics. But now a set of surprising experiments with fluids has revived old skepticism about that worldview. The bizarre results are fueling interest in an almost forgotten version of quantum mechanics, one that never gave up the idea of a single, concrete reality.

The experiments involve an oil droplet that bounces along the surface of a liquid. The droplet gently sloshes the liquid with every bounce. At the same time, ripples from past bounces affect its course. The droplet’s interaction with its own ripples, which form what’s known as a pilot wave, causes it to exhibit behaviors previously thought to be peculiar to elementary particles — including behaviors seen as evidence that these particles are spread through space like waves, without any specific location, until they are measured.

Particles at the quantum scale seem to do things that human-scale objects do not do. They can tunnel through barriers, spontaneously arise or annihilate, and occupy discrete energy levels. This new body of research reveals that oil droplets, when guided by pilot waves, also exhibit these quantum-like features.

## 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]

## That’s why it doesn’t matter if God plays dice with the Universe

Discovering Free Will (Part II, Part III) - a nice discussion of the Conway-Kochen "Free Will Theorem". [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]

## Mind is moving

Ron Garret, formerly of JPL and Google and "the most referenced computer science researcher in all of NASA", has an interesting take on quantum mechanics he dubs "zero-worlds", which he presents in an hour-long Google Tech Talk (meat starts around 42 minutes) as well as slightly older paper. He also got into a bit of further debate here. [more inside]

## 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]

## 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)

## Quantum realism mounts a charge. Prepare phenomenological defenses.

A mixed (superpositioned?) state of buzz among those working in quantum foundations over a new paper by Matt Pusey asserting that quantum states are real physical objects and not simply statistical probability distributions. Matt Leifer does a balanced contextualization and explication. A giddy article in nature news and David Wallace support and summarize. [more inside]

## Quantum Levitation

Sapphire + Superconductor + Gold + Saran Wrap + Liquid Nitrogen + Magnets = Quantum Levitation. [more inside]

## 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]

## The solution to quantum gravity is ready.

... and there is no dark matter/energy! Dr. Philip Mannheim has succeeded in developing a cosmological and quantum field theoretic consistent PT symmetric theory that contains no kind of dark matter and dark energy.
Space is flat in the absence of matter, and even the largest galactic rotation curves are predicted. Perhaps most interestingly, it also handles the cosmological constant and zero-point energy 'problems' simultaneously! (This is the final paper in a long list of publications, but it makes the case such that it's importance is immediately recognized. I leave it to the experts to recognize it's true beauty.) All hail the internets!

## Position-based quantum cryptography theoretically proved

*Our results open a fascinating new direction for position-based security in cryptography where security of protocols is solely based on the laws of physics and proofs of security do not require any pre-existing infrastructure.*

## The quantum mechanics of the waggle dance.

Mathematician Barbara Shipman speculates that a honey bee's sense of the quantum world could be as important to their perception of the world as sight, sound or smell: "the mathematics implies that bees are doing something with quarks."

## spacetime must organise itself in a way that maximises entropy

Gravity from Quantum Information

*At the heart of their idea is the tricky question of what happens to information when it enters a black hole. Physicists have puzzled over this for decades with little consensus. But one thing they agree on is Landauer's principle: that erasing a bit of quantum information always increases the entropy of the Universe by a certain small amount and requires a specific amount of energy.*(via mr)## Roger Penrose is looking more credible

Quantum processes involved in photosynthesis? "[A]lgae and bacteria may have been performing quantum calculations at life-friendly temperatures for billions of years. The evidence comes from a study of how energy travels across the light-harvesting molecules involved in photosynthesis. The work has culminated this week in the extraordinary announcement that these molecules in a marine alga may exploit quantum processes at room temperature to transfer energy without loss. Physicists had previously ruled out quantum processes, arguing that they could not persist for long enough at such temperatures to achieve anything useful." (via mr)

## [Tiger Woods] is busy, hasn't got a lot of time, but wants to catch up on what's happening in physics...

At least something good for someone has come out of the whole Tiger Woods brouhaha. Photos of Woods' wrecked SUV reveal a copy of Get a Grip on Physics on the floor of the Escalade's back seat. [more inside]

## Wolfgang Pauli was a Gargoyle?

## Quantum Art

## Somebody alert Jeff Goldblum

Scientists from the University of Michigan and the University of Maryland have managed to teleport information from one isolated atom to another over a distance of one meter, without it ever crossing space. Here's how they did it. [more inside]

## "You named your collaboration QAP? Really?"

The DiVincenzo Code [youtube trailer, geekery]. Faced with a strict demand from a funding agency to allocate research funds towards the dissemination of research ideas to the public, an experimental physics group at the University of Oxford produced a feature-length (55 min) action thriller about murder, ancient prophecy, tea breaks, and quantum computation. [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]

## R.I.P. John Wheeler, physicist

R.I.P. John Wheeler, theoretical physicist. Famous for the Wheeler-Feynman equations and the term "black hole," which he coined to describe a singular point mass, he has died at age 96. The NYT usually gives pretty good obituary but they outdid themselves this time. [more inside]

## 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]

## My name is Legion. You collapsed my probability distribution, prepare to die!

The Crossing is a new FPS game where single-player and multiplayer modes meld in one. At any point, any Non-Player-Character might not be an NPC at all, but another Player. It is likely that, as in a game of tag, players will just take turns to be "it" like Agents in the Matrix, but... wouldn't it be great if we could all be "it" at the same time? Quantum Gaming might just be the way to model such a swarm of gamers. [more inside]

## Particles and waves in your basement

Demonstrate one of the weirdest quantum effects in your home using a laser pointer, some tinfoil, a piece of wire, and a $7 polarizer. The device, called a quantum eraser, operates in a way very similar to the famously mind-blowing double slit experiment that was voted the most beautiful experiment in physics.

## Quantum Encryption

Quantum Encryption Scientists have created an unbreakable cypher through the use of quantum physics, where a photon is observed and used as the basis for an encryption key. "Uncertainty is the principle we exploit. It's impossible to find the key, because the photon can be measured once and only once. An eavesdropper can't measure it, and so can't get the key." Props to Heisenberg!

## Teleportation Breakthrough

Teleportation Breakthrough. Until now scientists have teleported similar objects such as light or single atoms over short distances from one spot to another in a split second.
But Professor Eugene Polzik and his team at the Niels Bohr Institute at Copenhagen University in Denmark have made a breakthrough by using both light and matter.
A more technical explanation.

## Quantum physics and You.

Enzyme reactions use quantum tunneling. British scientists have apparently solved the question of how enzymes speed up atomic reactions -- through a quantum tunneling effect at the reaction site. Just when you thought biology couldn't get any cooler. [via]

## maybe the Sarumpaet Rules will be worked out afterall

Before the Big Bang - way,

*way*out of my depth, but I thought this comment was intriguing: "The paper as published, along with a longer follow up paper, looks to my untrained eye a nearly complete quantum gravitation theory, which is an exciting prospect in itself. However, as with all physical theories, we will await for experimental support before popping the cork." Here's some more on loop quantum gravity, spin networks, the big bang and*ekpyrosis*.## Boundless energy or bad math?

Boundless energy or bad math? Randell Mills thinks he has the solution to our energy problems. In his company's patented process,

*"energy is released as the electrons of atomic hydrogen are induced to undergo transitions to lower energy levels producing plasma, light, and novel hydrogen compounds."*It also implies that quantum mechanics is wrong.## Student Challenges Basic Ideas of Time

A bold paper published in the August issue of Foundations of Physics Letters seems set to change the way we think about the nature of time and its relationship to motion and classical and quantum mechanics. The work also appears to provide solutions to Zeno's paradoxes. (Via Kurzweilai.net. More inside...)

## Schroedingers's lunchbox

Schroedinger's Lunchbox Quantom physics on an empty stomach is probably a mistake.

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