We have determined the energy difference between two quantum states in the helium atom with unprecedented accuracy, a ground-breaking discovery that contributes to our understanding of the universe and space-time and rivals the work of the world’s most expensive physics project, the Large Hadron Collider.

Our understanding of the universe and the forces that govern it relies on the Standard Model of particle physics. This Model helps us understand space-time and the fundamental forces that hold everything in the universe in place. It is the most accurate scientific theory known to humankind.

But scientists know the Standard Model does not fully explain everything, for example, it doesn’t explain gravity, dark matter, dark energy, or the fact that there is way more matter than antimatter in the universe.

So scientists are continually testing the Model by manipulating and controlling matter at the atomic level, looking for effects that cannot be explained directly – in this case the helium atom, which is the second most simple atom after hydrogen.

The latest experiment carried out by Dr Maarten Hoogerland from the University of Auckland and the Dodd-Walls Centre for Photonic and Quantum Technologies and Dr Wim Vassen from Vrije University in the Netherlands, was to test the helium atom’s transition between two states of energy. This is sometimes referred to as a quantum jump, or leap.

The significant change in energy in the atom is then precisely measured to estimate the diameter of the nucleus. This is done in an experiment that could fit on a tabletop with ultra-cold gas using an ultra-stable laser, accurate to a million times a million or, if you were using this level of measurement to measure the distance from Earth to the moon, it would be accurate to within a fraction of a millimetre.

“The fact the transition occurred is rare, and a milestone for quantum physics research. It advances our knowledge of the way atoms are put together and hence contributes to our understanding of space-time,” Dr Hoogerland says

“This new result is a great test for our understanding of the Model and also allows us to determine the size of the helium nucleus and of the helium atom. This has been the subject of intensive research for decades so for our experiment to have succeeded is an incredibly exciting result.”

The Large Hadron Collider is the largest machine ever built and a major international project involving hundreds of scientists looking for effects that cannot be explained by the Standard Model directly and for new particles at very high energy that do not fit the  Model.

The research is published here: https://rdcu.be/4sOu

A great summary appeared in the New Zealand Herald

Also we appeared on the radio this morning!

More news coverage on the business scoop

Again in Photonics Online!

We experimentally and numerically investigate thermalization processes of a trapped $87\mathrm{Rb}$ Bose gas, initially prepared in a nonequilibrium state through partial Bragg diffraction of a Bose-Einstein condensate (BEC). The system evolves in a Gaussian potential, where we observe the destruction of the BEC due to collisions and subsequent growth of a new condensed fraction in an oscillating reference frame. Furthermore, we occasionally observe the presence of defects, which we identify as gray solitons. We simulate the evolution of our system using the truncated Wigner method and compare the outcomes with our experimental results.

An extensive revamp of our setup has enabled the study of 2D physics using ultracold atoms. The details of the setup are published here:

Haase, T. A., White, D. H., Brown, D. J., Herrera, I., & Hoogerland, M. D. (2017). A versatile apparatus for two-dimensional atomtronic quantum simulation. The Review of scientific instruments, 88 (11)10.1063/1.5009584

We can let atoms expand in arbitrary potentials, such as a cavity shaped as a kiwi, a cat or a smiley face as shown here. Note that the entire size of the image is about the width of a human hair.

A kiwi from the atom lab to brighten your day. All kiwis are made from atoms – the only difference is that the one on the right was made today from rubidium atoms.

The image is made with 20000 atoms expanding from a Bose-Einstein Condensate of rubidium atoms in a plane (the plane is made by interfering two 1064 nm laser beams, having a lower frequency that the main resonance in rubidium).

• The kiwi is 150 micrometres in length.
• The atoms have a temperature of 10 nK.
• The height of the barrier made by the green laser is 2 microkelvin.

Nobel prize winner Bill Phillips was in Auckland. We had an excellent discussion at a poster session!

We have published an experimental study into the specific heat of a harmonically trapped Bose gas. Our experiment was sensitive enough to measure the correction to the specific heat caused by atom-atom interactions. Link to the article here: http://journals.aps.org/pra/abstract/10.1103/PhysRevA.92.063622 or to the preprint here: http://arxiv.org/abs/1409.5494

Our paper entitled

Phase noise in the delta kicked rotor: from quantum to classical

is now published in New Journal of Physics. This is an open access journal, so anyone can read it. It has a nice video that explains some of the basic concepts.