Archive for November, 2007

Quantum dreamin and optical illusions

Saturday, November 10th, 2007

double-image

Quantum consciousness, a phrase that sends most eggheads running for the hills, is currently on a roll. A coupla months back, Efstratios “Moussaka” Manousakis of Florida State University in Tallahassee published a paper suggesting that a certain kinda optical illusion could be explained in quantum terms.

The optical illusion in question is the double image flip like the one above which switches from one scene to another in the viewer’s mind. Neuroscientists have always wondered why ya can’t see both images at the same time.

The new thinkin is that the image exists in a kinda quantum superposition of both states. When this state collapses, it gives the observer the sense that he or she is lookin at one scene or the other (but not both). That sounds interesting but the impressive thing about Moussaka’s work is that it succesfully predicts the rate at which this flipping occurs in humans.

Now quantum physicist Henry “Goose” Stapp from the Lawerence Berkeley National Lab in Berkeley has entered the fray. His contribution is to tackle some of the criticism that has been levelled at Moussaka’s idea, in particular, the charge that in our warm, wet brains, decoherence destroys any quantum effects before they even get going.

Not so says Stapp. He argues that there exists a kinda twilight zone in which quantum phenomena can follow classical trajectories without being influenced by decoherence. So the collapse that triggers the conscious observation of one image or the other is essentially a classical phenomena that is steered by a few key quantum rules. It is therefore immune to decoherence.

Interesting idea but you can almost hear neuroscientists sucking their teeth as they read it. Stapp’s gonna need some more evidence and lots of it before an idea like this can become mainstream.

Ref: arxiv.org/abs/0710.5569: The Quantum-Classical and Mind-Brain Linkages: The Quantum Zeno Effect in Binocular Rivalry

The first brain image taken with an ultra low field MRI

Friday, November 9th, 2007

Ultra low field MRI

Ya’ll know that MRI machines are great hulking lumps o’ metal filled with pulsing tubes of liquid helium and evil superconducting magnets that’ll rip yer fillings out if ya as much as smile at ’em.

All that bulk is necessary to create the fantastic magnetic fields of several Tesla needed make the protons in yer body to line up in a way that makes it possible to image them.

Now all that is set to change thanks to Vadim “Eye teeth” Zotef and buddies at the Los Alamos National Labroatory in New Mexico. They gone and built themselves a machine that can image the brain using fields of only a few microTesla. Yep, thats microTesla. That has the potential to make MRI machines much smaller, perhaps even suitcase size

The trick is to use ultrasensitive devices known as SQUIDs (superconducing quntum interference devices) to do the imaging at much lower magfnetic field strengths. SQUIDs are so sensitive that they can pick up the magnetic fields generated by yer brain even as ya are a-thinkin and a-dreamin.

So Eye Teeth Zotef has combined the two things into one new toy: an ultra low field MRI machine plus a magnetoencephalograph.

This picture shows several layers from the first 3D image of a human skull and brain made in this way.

Champagne all round. (Or is it MGD they drink over at Los Alamos? Ah forget.)

Ref: arxiv.org/abs/0711.0222: Microtesla MRI of the Human Brain with Simultaneous MEG

Future computers to run on quantum monoxide

Thursday, November 8th, 2007

Quantum monoxide

Them quantum eggheads have long been a-huntin and a-scramblin to find the perfect building blocks for their quantum computers. They looked at photons, electrons, ions, neutral atoms and quantum dots. In fact there ain’t much they haven’t looked at.

Now Elena “Coolhand” Kuznetsova and chums at the Harvard-Smithsonian Center for Astrophysics in Cambridge says the answer has been staring everbody in face all along: carbon monoxide. Yep, a single molecule of hosepipe gas is the perfect place to put a qubit.

Here’s why quantum monoxide is so good. The dream qubit needs to be well protected from sources of decoherence. Qubits stored in electrons and ions, for example, decohere almost instantly. Sneeze and they’re gone. But a qubit stored in the electronic states of a quantum monoxide molecule is pretty robust, says Coolhand Kuznetsova.

Qubits also need to be able to interact with each other so that the information they contain can be processed. This is where photons fall down, getting two photons to talk to each other is almost impossible (although one or two bods have had some impressive success with nonlinear optical methods).

That ain’t a problem for quantum monoxide molecules since they can be made to interact via various coupling mechanisms.

The only problem now is to build a computer based on quantum monoxide. That’s where Coolhand and her pals fall badly behind cos their work is strictly theoretical and everyone else is outta their starting blocks and well into their stride.

Any experimentalists out there fancy takin’ this on?

Ref: arxiv.org/abs/0710.4356: Schemes for Robust Quantum Computation with Polar Molecules: Analysis of Experimental Feasibility

Studying the tunnel of death

Wednesday, November 7th, 2007

Lefortovo

The Lefortovo Tunnel runs underground for 3 kilometres on the outskirts of Moscow. The deep tunnel has three lanes which are equipped with traffic sensors every 60 metres. These have provided a rich vein of traffic data for Boris Livshits and pals at Moscow Technical University who have been a-mining and a-crunchin it.

B Livshits says the data shows there are four distinct phases of traffic flow: free flow, light synchronised traffic, heavy synchronised traffic and jam. They’ve even found that that traffic undergoes a phase change when the lane occupancy rises above 32 per cent. When that happens, the average speed of the traffic drops suddenly by at least 15 km/h.

But they missed a trick here. Traffic planners want to be able to prevent jams by spotting the telltale signs that they are about to form and then slowing everything down or reducing lane occupancy in way that prevents the jam forming.

But B Livshits and friends ain’t got anything to say about what causes jams to form. Perhaps they ain’t got the right kinda data. Maybe studying the video below, taken in the tunnel, might help ’em better understand the cause of jams.


Ref: arxiv.org/abs/0710.3273: Complex Fundamental Diagram of Traffic Flow in the Deep Lefortovo Tunnel (Moscow)

A load of Pollocks

Tuesday, November 6th, 2007

Pollock

In 1999, Richard “Drippy” Taylor at the Univesity of New South Wales in Australia announced that he was able to tell a painting by the American abstract expresisonist Jackson Pollock by analysing the fractal patterns made by the paint on the canvas. He claimed that the fractal signature Pollock made as he dripped paint onto the canvas was unique and the technique could be used to a tell the real thing from a forgery.

The technique was little more than a novelty until 2003 when a cache of more than 25 unattributed paintings believed to be by Pollock were found in the US. All of a sudden the fractal analysis technique meant the difference between a worthless piece o’ cancas and a million dollar masterpiece.

Or so Taylor thought. Now Lawrence “Beam me up Scotty” Krauss and colleagues from Case Western Reserve University in Cleveland say they taken another look at the fractal technique and have pronounced it a load of old pollocks.

The team say they have shown that “amateur artists seeking to emulate Pollock’s technique can successfully create paintings which possess the fractal signature said to be unique to Pollock”. They also say that “even authentic Pollock paintings fail to possess his fractal signature”.

So there ya have it. The ball’s now firmly in Drippy Taylor’s court.

Ref: arxiv.org/abs/0710.4917: Drip Paintings and Fractal Analysis

A wishlist of experiments to do in space

Monday, November 5th, 2007

What should we do in space? NASA has bet the farm on the International Space Station, a giant orbiting Lego set where astronauts can play Mommies and Daddies, practice sharing and become zero-g toilet trained. Almost everyone else wants to do something useful.

So a bunch of chief eggheads from the world of physics have drawn up a wishlist of space missions to look for new physics and test the old stuff to breaking point. Here’s a few of the gems:

SpaceTime: a mission to fly atomic clocks in a highly elliptical orbit around the Sun to see if the fine structure (or other fundamental) constant varies. Could also test the Equivalence principle

Inverse Square Law Experiment in Space (ISLES) does what it say on the tin by bouncing laser beams off the Moon and Mars to test whether gravity really follows an inverse square law at large distances

The Laser Astrometric Test of Relativity (LATOR) would use laser interferometry to measure the non-Euclidean geometry of giant light triangle around the Sun. The mission would test whether the infamous evidence in favour of dark matter could be explained instead by a modified theory of gravity

LISA (the Laser Interferometer Space Antenna) measures gravity waves using a constellation of laser interferometers

The Extreme Universe Space Observatory (EUSO) watches how a segment of the Earth’s atmopshere lights up when struck by ultra-high energy cosmic rays and neutrinos. Might also spot dark matter particles

Cold atom sensors in space could test the inverse square law at the scale of a few micrometers.

And so on…

If these sound like a physicist’s wet dream, yer probably right. But don’t write it off, there are some big cheeses behind this list, including Francis “Probe” Everitt (although the last spacecraft he built took 40 years to get into space ). They got the clout to get at least one of these things off the ground.

Ref: arxiv.org/abs/0711.0150: Space-based Research in Fundamental Physics and Quantum Technologies

Cakes ‘n’ cream

Sunday, November 4th, 2007

The tastiest leftovers from the physics arXiv this week:

A New Source of Random Numbers for Cryptographers

Q: Can One Detect Passage of a Small Black Hole through the Earth? A: Yep

Detecting Communities in Social Networks

Entanglement on Demand through Time Re-ordering

Crime ‘n’ punishment

Saturday, November 3rd, 2007

Social physics is a cool new science in which the eggheads use mathematical models to simulate the behaviour of large numbers of people. What these guys are finding is that very simple assumptions can reproduce hugely complex behaviours and they is using it to study everything from trading on the money markets to the spread of racism.

Now Mirta “Squirter” Gordon at the University of Grenoble in France  is using the technique to study crime levels. Here’s the thinkin’: crime costs societies in many ways. But crime fighting is expensive too,  cos a-huntin’ and a-chasin’ crims costs money.

So perhaps there’s a balance to be had: society could accept the cost of a small amount of crime and thereby save on law enforcement.

That would be an error, conclude Squirter Gordon and her colleagues. Their model assumes that  people have an inclination to abide by the law that depends on the likelihood of being caught after committing a crime.  So people are more likely to commit crime when they are less likely to be caught.  Seems reasonable.

What happens when ya run the simulation is that the  crime rate increases as law enforcement is cut and the chances of getting caught drop. So far so good-that’s kinda what ya expect.

But Squirter Gordon has found something else: a critical point at which a very small cut in law enforcement causes a massive increase in crime. In other words a phase change.

That’s has big implications. The community can save money by cutting law enforcement but once the critical point has been reached and crime soars, the cost of reducing crime levels again is huge.

The moral? Cutting law enforcement is a false economy.

Ref: arxiv.org/abs/0710.3751: Crime and Punishment: the Economic Burden of Impunity

Triggering a molecular supernova

Friday, November 2nd, 2007

Place a fluorescing molecule next to a gold nanosphere and it lights up like a supernova.

That’s what Vahid “Thou” Sandoghdar and his cronies at the Swiss Federal Institute of Technology in Zurich are telling ya’ll today. This simple trick turns a molecular matchflame into a full blown roman candle.

Here’s what’s goin on. The light emitted from the molecule causes waves of electrons called plasmons to surf over the surface of the sphere. If the frequency is just right, yer get a resonant effect that boosts the emission. Thou Sand reckons he can boost the fluorescence by a factor of ten thousand.

Strap your gold nanosphere to the end of a probe, scan it across a surface and as the sphere passes by, individual molecules will flare up like herpes on a party campus (ah mention no names, Arizona State, cough) . Molecules have a habit of a-movin and a-migratin when you ain’t looking so having a way to spot them again is surely gonna be handy for anybody building molecular machines and computers.

Ref:  arxiv.org/abs/0710.4092: Modification of Single Molecule Fluorescence close to a Nanostructure: Radiation Pattern, Spontaneous Emission and Quenching

How cleanliness can kill

Thursday, November 1st, 2007

The hygiene hypothesis is that our immune system requires the presence of pathogens to grow and function properly. The thinkin is that dirt ‘n’ muck provides a kinda training ground on which the immune system “learns” it’s trade when we’re all youngsters.

So mothers who keep a-scrubbin and a-cleanin them germs away are actually doin’ more harm than good. Their littluns’ immune systems ain’t never gonna learn how to fight off invaders.

Alotta medical bods think the hygiene hypothesis makes sense. They say it’s cleanliness that causes asthma and other allergies, not dirt. And the evidence is growing to back ’em up. But exactly how this balance between pathogens and our immune system works ain’t known.

Now Didier “See” Sornette at the Swiss Federal Institute of Technology in Zurich and a few buddies have built a mathematical model of the immune system based on this idea. Their assumption is that a balance exists between the immune system and the many pathogens that it comes across each day. (FYI our bodies are built outta 10^13 cells but house something like 10^14 bacteria.)

See Saw and his pals study two ways that this balance can change. The first is an external attack of pathogens such as a cholera epidemic or an infection following major surgery. Obviously that don’t do nobody no good.

But another type of change occurs when the immune system itself becomes weakened, perhaps by stress, lack of sleep or heavy boozin’. Then pathogens can spread even if the body ain’t exposed to an abnormal load.

See Saw’s work consists of exploring the topology of this mathematical model and findin’ areas of stability. The model predicts, for example, that a critically ill person can be made healthy by strengthening their immune system. Nothin’ strange about that. But it also predicts that ya can kill a critically ill person by reducing the load on their immune system. That’s when cleanliness kills.

So dirt might be even better than we thought. Not only does it train the immune system, but it can keep ya alive too. And if that’s the case, sterile hospitals could be as bad as dirty ones.

That’s gonna get people goin’ like a mongoose in a jockstrap. Ya’ll sit back and wait for the wailin’ and gnashin’ of teeth.

Ref: arxiv.org/abs/0710.3859 :Endogenous versus Exogenous Origins of Diseases