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RECENT FORUM POSTS

Thomas Ray: "Here's something, Eckard, from the Barrett paper Jonathan linked, that..." in Black Holes Do Not Exist,...

Thomas Ray: ""Something that is said to be larger than any quantity cannot be a quantity..." in Black Holes Do Not Exist,...

Peter Jackson: "Akinbo, Nice to find agreement, and well spotted re-pure plasma and the..." in Faster than Light

Peter Jackson: "Steve, Electron densities were up to ~10^2/cm^-3 (that is per cubic..." in The Quantum Pet Store:...

Akinbo Ojo: "Okay your definition 'reality' and 'non-linear' sounds fine, with some..." in Faster than Light

Steve Agnew: "Your rabbits are really amazing...you just keep pulling. Actually I never..." in The Quantum Pet Store:...


RECENT ARTICLES
click titles to read articles

Life's Quantum Crystal Ball
Does the ability to predict the future—perhaps with quantum help—define the fundamental difference between living and inanimate matter?

The Quantum Truth Seeker
Watching particles fly through an interferometer might help to unveil higher-order weirdness behind quantum theory.

Quantifying Occam
Is the simplest answer always the best? Connecting Medieval monks to computational complexity, using the branch of mathematics known as category theory.

Heart of Darkness
An intrepid physicist attempts to climb into the core of black hole.

Why Quantum?
Entropy could explain why nature chose to play by quantum rules.


FQXi BLOGS
October 22, 2014

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Dust Settling on the BICEP2 results
By ZEEYA MERALI • Sep. 22, 2014 @ 15:35 GMT

Just opening up a forum thread for discussing the intermediate Planck results (arXiv:1409.5738v1) which show that the BICEP2 signal -- lauded as direct of evidence of primordial gravitational waves earlier this year -- could be down to dust, which has long been a concern.

The image shows Planck's Northern (on the left) and Southern (right) sky projections. Dark blue indicates parts of the sky that are clearer of dust. BICEP2 looked at the region marked by the black box in the Southern projection.

For background, listen to our podcast editions from May, with interviews with Andrei Linde and especially Joao Magueijo (who raised these particular concerns and others), and June, with Alan Guth.

Reports from Quanta, the BBC and Nature.
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The Quantum Pet Store: New Podcast Edition is Up!
By ZEEYA MERALI • Sep. 1, 2014 @ 02:00 GMT

L. Filter, Nature Communications
The latest edition of the podcast is up -- and you may notice there's a bit of a quantum animal theme. Listen to it here.

First up, we talk to Andrew Jordan of Rochester University about recent experiments that allow you to track and steer Schrodinger's metaphorical cat (or in this case a superconducting "transmon") between life and death, while it is locked in a box. The technique could be used to create a new kind of quantum control.

Other animals featuring in the main podcast are quantum pigeons. FQXi member Jeff Tollaksen chats about his theoretical analysis that suggests that there is a new type of quantum correlation that's even spookier than those we've come to know and love. We're used to talking about quantum entanglement, which continues to link two or more particles that have been specially prepared together, no matter how far apart they are separated. But Tollaksen and his colleagues have calculated that quantum particles can become united without having to ever have been in contact. And he illustrates this by talking about vanishing pigeons!

Both of these items described by Jordan and Tollaksen are based on pioneering theoretical work on "weak measurements" in the 1960s by FQXi member Yakir Aharonov and colleagues. These allow experimenters to measure some properties of quantum systems, without destroying them. You can read more about that program in the article, "The Destiny of the Universe" by Julie Rehmeyer.

That research program has also lead to the idea that it is possible to create what Tollaksen dubs a "Quantum Cheshire Cat." Just as the cat in Alice in Wonderland managed to slowly vanish leaving behind a grin without a cat, physicists have recently carried out experiments in which a neutron has been separated from its properties. Tollaksen spoke to me about these tests too, and you can hear that as a podcast extra on the website, but note that it is not in the main podcast. (The image above, by Leon Filter, appears in the team's paper in Nature Communications. Thank you to Gina Parry for suggesting a forum post based on this piece of research.)

We have also included some non-animal items too. For cosmology fans, and those hankering for a resolution of the black hole information paradox, check out the interview with FQXi's Carlo Rovelli. His latest analysis with Hal Haggard, based on the theory of Loop Quantum Gravity, predicts that when black holes die, they explode into white holes, spewing all the matter that they swallowed back out again. If he and his colleague are correct, then astronomers may be able to pick up signs of such exploding black holes -- which would also be the first observational support for this model, or indeed any candidate theory of quantum gravity.

But it's not all smooth sailing. Keen podcast listeners may remember an interview from the June 2013 podcast with Jorge Pullin, who carried out a similar analysis also using loop quantum gravity, but got a different answer. Pullin argued that at the center of black holes you will find wormholes that fast track you to other parts of the universe. Listen to the podcast to find out what Rovelli has to say about the conflicting results.

And, if you enjoyed reading Sophie Hebden's profile of Noson Yanofsky and his work using category theory to study whether Occam's Razor is really mathematically valid, then you can also listen to her interview with him.

Anyway, please tune in and listen to all the latest weird and wonderful experiments and models. As Alice would say, things are getting curiouser and curiouser.
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Your Invitation to FQXi's Online Essay Contest Award Ceremony & a Call for Questions!
By ZEEYA MERALI • Aug. 20, 2014 @ 21:05 GMT

The judges have made their decisions…and we can now (almost) reveal the winners of this year's essay contest, which asked: "How Should Humanity Steer the Future?" We had 155 entries this year and we're awarding 16 prizes. Thank you to everyone who entered, read the entries, commented, and voted for their favourites.

This year, we're doing something a bit different with the announcement of the big winners. We're inviting you to tune in to a live webcast of the award ceremony, where you can join FQXi directors Max Tegmark and Anthony Aguirre as they reveal the top 3 prize winners. Our first prize winner will walk away with $10,000, and our two second prize winners will each take home $5,000.

The event: The FQXi Essay Contest Award Ceremony 2014

The time: Thursday 21st August, 1pm EDT

The place: Here



This is also your chance to quiz the winners, so please post your burning questions below. To aid you in framing your questions, I have permission to reveal the panellists…but I cannot yet tell you which of them has won first prize, and which two are runners-up. You'll find out -- as will they -- tomorrow at the ceremony!

So congratulations to our panellists, who between them have won the top 3 prizes. They are listed here in alphabetical order:

Daniel Dewey, who wrote about "Crucial Phenomena"…

Sabine Hossenfelder, who told us "How to Save the World"…

Jens Niemeyer, who outlined "How to avoid steering blindly: The case for a robust repository of human knowledge".

Please post your questions and comments below (or tweet them to @FQXi).

We've also been busy announcing the names of our six 3rd place winners ($2,000), five 4th place winners ($1,000) and two special prize winners ($1,000) on twitter and Facebook. You can check out the list of the winners who have been revealed so far here. Congratulations to each of them for providing some thought-provoking reading matter.
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Quantum theory escapes locality by accepting uncertainty
By OSCAR DAHLSTEN • Aug. 17, 2014 @ 15:28 GMT

Figure 1
When a ballerina does a pirouette she must escape the friction of the ground in order to get the freedom to move. (Figure 1: Photo by Michael Garner, courtesy of English National Ballet.) She does this by restricting her contact with the ground to a point. In a recent paper I and my collaborators Andrew Garner and FQXi's Vlatko Vedral show that quantum theory in a very similar way escapes a fundamental constraint on movement by accepting uncertainty.

Quantum systems are associated with states which encode the statistics of future possible measurements. The collection of such states may be represented as a geometric shape. In the smallest possible quantum systems, single qubits (quantum bits), this shape is a sphere, called the Bloch sphere.

For example, think about a property of a qubit, such as its position: the qubit could be associated with two possible positions, A and B, say, or it can be in a fuzzy superposition where it exists in both of these mutually incompatible states simultaneously, before being observed. If it's in a superposition then although experimenters cannot know with certainty what position they will find it in when they make a measurement, they will have some sense of the probability of getting a certain outcome. The Bloch sphere helps to visualise this odd feature and the probabilistic nature of quantum mechanics. In the example, a vector pointing to the north pole of the sphere could represent position A, while the south pole represents position B. (In a classical system, this would represent the only two options available for a binary digit, or bit, to access). However, a qubit can also be represented by a vector pointing elsewhere on the surface of the sphere, corresponding to the fuzzy in-between states.

Figure 2
The maximal state space conceivable would actually be the cube outside of the sphere, as shown in figure 2. The quantum state space is the sphere, but if there were no uncertainty principle all states in the outer cube could be allowed. In this case certain measurements could all have predictable outcomes at the same time, in violation of the quantum uncertainty principle.

One may ask why quantum theory is restricted to the sphere, and accordingly to having the uncertainty principle.

We came across an intriguing answer when thinking about how the cube state space would handle an interferometer. In an interferometer the particle or photon is firstly placed in a superposition of being in two places and then operations are done on each site. Now when you have two different sites fundamental locality restrictions come into play. In particular, we point out that if a system has 0 probability of being found on site B, then an operation on site B must leave the state of the system invariant. Otherwise we could do action at a distance. Contrary to some popular science depictions, quantum theory does not allow action at a distance. The universe would be almost inconceivably odd and complicated if action at a distance were possible. We would not be able to make a statement about an individual system without taking into account what happens everywhere else in the world.

On the Bloch diagram, state transformations move points around, e.g. by rotating the shape. So, if one accepts that this locality restriction holds, it turns out that operations on site B must leave all points (states) on the lower plane of the cube invariant. It is like the points are stuck by total friction between the shape and the lower plane. As a result the cube has a big disadvantage over the sphere because if the entire square face touching the ground is restricted, then the whole cube gets stuck and no states can change.

But now imagine metamorphosing the cube into a sphere, or indeed something else with only one point on the lower plane, like how the ballerina goes up on one toe. Then the shape, with all the quantum states in it, can move. The quantum sphere has the advantage over the cube that it can rotate even if there is full friction with the lower (and/or upper) plane, just as the ballerina accepts the uncertainty of only having a point in contact with the ground in return for the ability to pirouette.

One may say that uncertainty, rather than being just limiting, liberates quantum states to change.

--

Oscar Dahlsten is affiliated with Oxford University

The paper appears in Nature Communications.
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F(ilm)QX
By WILLIAM OREM • Aug. 1, 2014 @ 20:34 GMT



Looking for a low-level break from your usual high-level philosophizing about science? Check out Luc Besson's latest: a sci-fi shoot-em-up titled *Lucy* that will keep you crunching popcorn without straining too many neurons.

Okay, it's not really the thinky movie it thinks it is, but it's fun, and the premise is terrific (spoiler alert, obviously).

Our story begins with Lucy, the Australopithecus, sipping water from a primordial stream: hey, look how far make-up has come since *Space Odyssey*! (Plot ideas, not so much; this movie's most interesting parts are *Space Odyssey* on training wheels). Flash forward three million years to Scarlet Johansson as another Lucy, this one a modern-day dimwit who becomes entangled in an evil Japanese scheme to sell a new designer drug. The drug -- it's not clear how the bad guys missed this before they decided to mass-market it -- inadvertently causes people who take it to start utilizing more and more of their untapped cognitive potential. You may remember a similar premise from the 2011 movie *Limitless,* in which . . . well, exactly that.

This time, the bad guys stash a bag of the stuff in poor Scarlet Johansson's abdomen, turning her into a detection-free drug mule. Even worse, halfway to her destination a sadist starts beating her up, kicking her so hard in the gut that the bag full of crystals begins to leak . . .

That's the most intimidating moment of the movie right there, actually. Lucy's enforced participation in these gruesome proceedings; the savagery of the thugs, coupled by the icy sociopathy of the kingpin; it's scary stuff. At exactly this point, however, our suspended disbelief plummets as we dive into what has become the bane of Hollywood thrillers: the whiz-bang CGI sequence. Racing through Lucy's capillaries *Incredible Spider-Man* style, we see what would have been obvious anyway: the leaked drug is infiltrating her brain, causing amazing physiological changes. (The first of these, oddly, is an anti-gravity seizure.)

How we got from "she's becoming more intelligent" to "she's floating on the ceiling" is anyone's guess -- or, rather, it's up to Morgan Freeman, in his usual wise mentor role, to inform us via a series of wildly unscientific lectures. Among the groaners:

The notion that humans only use 10 percent of our brains. Why do so many people think this is true? There isn't a 90 percent block of gray matter that's just sitting in our skulls, not functioning. This movie claims to be about human evolution -- and interrupts itself frequently to montage about the effects of evolving intelligence in the cosmos -- but isn't all that clear on how brains actually evolve. To quote a Scientific American article on this misperception: "Though an alluring idea, the '10 percent myth' is so wrong it is almost laughable . . ."



If you had access to 20% of your brain, science-Morgan tells us, "you could control your own body." (A bit of a head-scratcher: don't humans control their bodies right now? And why does Lucy start having eyeballs from other species?) At 30% you can control other people's bodies as well; next comes telekinesis, morphing, and on up to time travel. How science-Morgan concluded any of these things is left out of the script, probably wisely; just play along.

Religion also gets smooshed in here too, though in a rather perfunctory way: "You never really die," Lucy informs a mere mortal at one point. "I only hope we are worthy of your sacrifice," science-Morgan sighs, as she heads toward her humanity-saving apotheosis. There isn't much of Lucy-as-Savior, though: mostly she kicks ass and shoots guns.

The real fun, however, isn't any of that -- it's in the premise of a dumb, abused woman who quickly becomes not only smart, but smarter than her abusers, then smarter than the police chasing her, the scientists studying her, and everyone else on earth. In a way, we owe all such stories to Arthur Conan Doyle, whose hyper-perceptive detective set the standard (If you doubt the enduring influence of Sherlock Holmes, I would point you toward the Robert Downey Jr. movies, the PBS re-runs of the magnificent Jeremy Brett, the runaway British success *Sherlock*, the American TV shows *Elementary* or *The Mentalist* or even *House* . . . among still others.)

Now it's Lucy, who can out-think the rest of us with ease as she evolves up the Kurzweil ladder of rapidly accelerating intelligence. If only the movie stayed with that idea, which is something that is actually on the way -- technologically enhanced super-intelligence, when we boot-strap ourselves into another evolutionary phase altogether -- instead of the magical stuff. As Mr. Spock, an earlier Sherlock Holmes knock-off, would have said, that's fascinating.

credit: public library toronto

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