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FQXI ARTICLE

December 20, 2014

A Whole New Quantum Ball Game

Searching for the boundary between the quantum and classical worlds, with microscopic polystyrene balls.

FQXi Awardees: Hendrik Ulbricht

February 25, 2011

HENDRIK ULBRICHT

University of Southampton

When quantum mechanics arrived on the scene in the early part of the twentieth century it wrought havoc with our common sense view of the world. Think that light is a wave and electrons are tiny billiard-ball-shaped particles? Think again, because experiments showed that light can sometimes behave like a stream of bullets, known as photons, while small particles, such as electrons, can display wave-like properties. The question is, can we find the line beyond which objects are too big to show this dual-quantum behavior?

With an FQXi grant of around $140,000 in hand, Ulbricht, at the University of Southampton, UK, is searching for this quantum limit—if it exists—by recreating one of those classic experiments using microscopic balls of polystyrene of increasing size. His polystyrene test has all the elements of Thomas Young’s nineteenth-century

Pushing Boundaries

Over the years, interference patterns have been created by firing single electrons, atoms, and even large molecules at the slits. Those experiments confirm that these particles have a wave-like nature, somehow interfering with themselves before landing on the collection plate. Ulbricht hopes to push the quantum-classical boundary a big step further by demonstrating interference using polystyrene balls that are a thousand times heavier than the largest molecules tested so far.

Ulbricht traces his interest in physics to school, where a teacher lent him Stephen Hawking’s

Instead Ulbricht opted for an experimental PhD, which eventually led him to a molecular interference lab at the University of Vienna, Austria, with Markus Arndt and FQXi-member Anton Zeilinger.

INTERFERING WITH PHYSICS

Will Ulbricht’s optical grating experiment reveal a quantum limit?

Ulbricht’s main challenge in carrying out his tests is to create a coherent beam of polystyrene balls. The balls come in a solution, which Ulbricht squirts into the focus of an optical trap, where a laser pins down the balls and holds them in an electric potential between mirrors. There the balls are cooled to stop them jiggling, and then released, so that they drop under gravity through an

The final step is to examine the distribution of the polystyrene balls on a glass plate beneath the grating, using a microscope. "Nobody has done it with polystyrene before but it looks very promising," says Ulbricht.

Quantum Breakdown

Steven Carlip, a quantum gravity theorist at UC Davis, notes that the technology has only recently become good enough to test these big masses. "A lot of us hope that something interesting will happen when you get to high enough masses," says Carlip. "Maybe quantum mechanics will break down."

Is it new physics? Or

is the reason we don’t

see large quantum objects

just a technological issue?

is the reason we don’t

see large quantum objects

just a technological issue?

- Hendrik Ulbricht

To fill the gap there are lots of non-standard theories that attempt to explain the transition. The most popular is

"There is no question that decoherence exists," says Ulbricht. "But the question is whether that is really the reason why we don’t observe macroscopic quantum objects. Is it new physics or is it a technological issue, of being able to stop the particle interacting with the environment?"

Spaceballs

Rival theories of wavefunction collapse predict a quantum breakdown at different masses between a million and ten billion times that of a hydrogen atom and both Ulbricht and Arndt hope to discriminate between them. But there’s a problem: At the upper end of that mass scale, gravity could affect the experiment by accelerating the particles towards the grating, making their wavelength too small for interferometry.

To get round this, the tests may have to be carried out in microgravity. "Ulbricht’s experiment is preparing the way for such space-based experiments," says Ardnt.

If Ulbricht’s polystyrene balls do make it into space years from now, it will be good news for quantum mechanics, because it means that the theory will have held up in all his Earth-based tests.

Carlip’s money is on quantum mechanics’ continuing success. "I would bet that Ulbricht will continue to see interference as long as his experiment is accurate enough," he says.

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PAUL REED wrote on June 3, 2012

Steve

No!

All that exists at any point in time is a finite number of adjacent spatial possibilities which the entity could occupy next (directions if you want, but not dimensions). There is no 'time' within any given reality, because that is concerned with the rate at which this movement (or any other form of change) occurred. And if there is change that means there is another reality (or physically existent state is better) which has superseded the original. The two do not exist...

Steve

No!

All that exists at any point in time is a finite number of adjacent spatial possibilities which the entity could occupy next (directions if you want, but not dimensions). There is no 'time' within any given reality, because that is concerned with the rate at which this movement (or any other form of change) occurred. And if there is change that means there is another reality (or physically existent state is better) which has superseded the original. The two do not exist...

STEVE DUFOURNY wrote on June 2, 2012

incredible, 11 posts, I see 3 posts .You are really bad persons simply.

A comportment of stealers simply.

incredible, 11 posts, I see 3 posts .You are really bad persons simply.

A comportment of stealers simply.

JOE BLOGS wrote on July 29, 2011

Lets chat.

https://www.sendthisfile.com/Dsi1UcAS1T4nqej4a0zxk1TB

My clock converts a circular earth orbit into an eliptical one.

And the result is six minutes difference from sidereal time per year.

Approx we take this figure to 10,000 digits of pi accuracy as the formula uses Pi.

A cicular orbit can be in as many as 11 dimensions but these are unstable when an orbit is converted to an elipse it becomes stable in three dimensions plus one of time.

Thus...

Lets chat.

https://www.sendthisfile.com/Dsi1UcAS1T4nqej4a0zxk1TB

My clock converts a circular earth orbit into an eliptical one.

And the result is six minutes difference from sidereal time per year.

Approx we take this figure to 10,000 digits of pi accuracy as the formula uses Pi.

A cicular orbit can be in as many as 11 dimensions but these are unstable when an orbit is converted to an elipse it becomes stable in three dimensions plus one of time.

Thus...

read all article comments