Quantum pancake reveals clues to better electronics

First published on Cosmos Magazine site, 25/9/18

An experiment with a cloud of ultracold atoms squashed into a quantum pancake has revealed never-before seen quantum effects that could lead to more efficient electronics, including high temperature superconductors.

A team at Swinburne University in Australia observed a quantum anomaly in lithium-6 gas cooled to a few billionths of a degree above absolute zero and squashed between two laser beams.

“We’re seeing quantum mechanics that’s visible on a macroscopic scale – a large collection of tens of thousands of atoms all behaving quantum mechanically,” says project leader Chris Vale, a researcher at Swinburne’s Centre of Excellence in Future Low-Energy Electronics Technologies.

The team’s work is published in the journal Physical Review Letters, concurrently with that of a team from Heidelberg in Germany which reported similar results.

The Australian team used laser beams focused into a flat plane to create a pancake of lithium-6 gas with a radius of 200 microns and the thickness of a single atom – around 500 nanometers. Then the researchers compressed the gas slightly with a magnetic field, to set it vibrating. Shining another laser from below, they measured the vibration frequency of the gas cloud by watching the shadow of the cloud on a camera.

The frequency of this radial vibration, known as a breathing mode, gave the telltale sign of a quantum anomaly: it vibrated 2.5% faster than the classical model predicted.

Symmetry in the classical model dictates that gas properties such as pressure and density should scale in a straightforward way as the size of the gas cloud oscillates. But the full quantum analysis predicts a higher frequency: the classical theory breaks down because of strong interactions between the gas particles.

To further test the model, the scientists jammed more atoms between the laser beams, and turned the pancake from a two-dimensional crepe into a fatter flapjack. Its three-dimensional nature conformed to the classical model.

Vale says the interactions between the gas particles in the quantum crepe was mid-way between two well-known states of matter: Bose-Einstein condensates, in which atoms in a gas interact strongly and exhibit uniform quantum behaviour, and low temperature superconductivity, in which electrons in a material form weakly-bound pairs known as Cooper pairs that can carry electricity through a material with no energy loss.

“There’s a continuous crossover between these two limits, what happens in the middle is not well understood,” he says

“There’s a lot of interesting physics there. For example, this is where we find the highest superfluid transition temperatures, in the intermediate zone where the binding energy of the fermion pairs is similar to the natural energy scale for the system, the Fermi energy.”

By studying a two-dimensional system, Vale hopes to spark developments of new materials for the electronics industry, for example topological insulators or high-temperature superconductors.

In the current highest-temperature superconductors, ceramics based on copper oxide, the superconducting current is carried in two-dimensional layers within the material – although exactly how the electrons pair up is not fully understood.

The power of the experiments at Swinburne is their simplicity, says Vale – the microscopic properties of the lithium atoms and their interactions are precisely known, which is not always possible in more complex materials such as solids.

“In a sense, our cold atoms are acting as a quantum simulator, where we can test models of many-body physics with precisely known inputs that can be difficult to pin down in other materials,” he says.

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WordPress Resources at SiteGround

WordPress is an award-winning web software, used by millions of webmasters worldwide for building their website or blog. SiteGround is proud to host this particular WordPress installation and provide users with multiple resources to facilitate the management of their WP websites:

Expert WordPress Hosting

SiteGround provides superior WordPress hosting focused on speed, security and customer service. We take care of WordPress sites security with unique server-level customizations, WP auto-updates, and daily backups. We make them faster by regularly upgrading our hardware, offering free CDN with Railgun and developing our SuperCacher that speeds sites up to 100 times! And last but not least, we provide real WordPress help 24/7! Learn more about SiteGround WordPress hosting

WordPress tutorial and knowledgebase articles

WordPress is considered an easy to work with software. Yet, if you are a beginner you might need some help, or you might be looking for tweaks that do not come naturally even to more advanced users. SiteGround WordPress tutorial includes installation and theme change instructions, management of WordPress plugins, manual upgrade and backup creation, and more. If you are looking for a more rare setup or modification, you may visit SiteGround Knowledgebase.

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Workin’ like a gherkin

PhilQuickly updated my Dr Phil Live page, and realised I have a busy few months across four cities!

COMING UP…

Wednesday May 9: Colliding Stars, Quantum Particles and Hawking’s Black Hole Legacy (Physics in the Pub) – Smiths Alternative, Canberra

Friday May 11: Colliding Black Holes, Quasiparticles and a low energy future (Physics in the Pub) – Beer Deluxe, Hawthorn, Melbourne

Monday May 14: MC, Collaborate, Innovate – CRCs Conference Drinks, UTS, Sydney.

Wednesday June 13: Chemistry in the Pub – Smiths Alternative, Canberra

Tuesday June 19: Sustainable Stand Up – Smiths Alternative, Canberra

Wednesday July 11: Health and Medical in the Pub – Smiths Alternative, Canberra

Wednesday August 15: Pub Cabaret, Dr Phil & Tom Gordon – Sydney

Thursday August 16: Physics in the Pub – Orient Hotel, Sydney

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Would you let me put drugs in your brain?

The amazing Dr Kiara Bruggeman gets all Dr Seuss with her rhyme about her PhD research to develop a bandaid for the brain. Previously she won FameLab people’s choice award with this piece.

 

Filmed at Health and Medical in the Pub at Smiths Alternative in Canberra. Supported by National Science Week ACT, ANU Medical School, Australian Society for Medical Research.

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Wave of the Century

Originally published in ANU Reporter:

The discovery of gravitational waves is the culmination of a search by a generation of ANU physicists, reports DR PHIL DOOLEY, BSc (Hons) ’90, PhD ’99.

An excited hush fell over the briefing room at Parliament House as Professor David McClelland stepped up to the microphone.

“I’m pretty sure you all know by now but I want to say it. We’ve done it,” he said as his voice quavered.

Spontaneous applause broke out, as McClelland allowed himself a smile. Camera flashes popped and TV cameras zoomed in.

“We detected a wave that was generated 1.3 billion years ago when two black holes crashed into each another… the most violent event ever witnessed.”

The announcement was sweet reward for McClelland, an ANU laser physicist who has spent his career working towards this moment.

Albert Einstein predicted the existence of gravitational waves but thought they were too small for humans to ever detect.

To prove Einstein wrong and right in a single stroke is rare treat for a scientist.

“This is a moment that will be remembered for a thousand years,” McClelland said.

Gravitational waves are vibrations of space and time themselves, one of the most outlandish predictions of Einstein’s 1916 General Theory of Relativity. Yet, they appeared exactly as predicted and join the long list of successes of Einstein’s theory over the last century.

The first success of Relativity came three years after Einstein’s publication, when a solar eclipse allowed astronomers to pick out the tiny deflection of distant starlight by the sun’s gravity.

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