‘Quantum egg carton’ to test field theories

In the quantum realm, no particle is an island.

At microscopic scales, the likes of photons and electrons are constantly interacting with quantum fields, the omnipresent swarms of real and virtual particles that underlie the physical world we see. This means that a description of a single particle alone is always incomplete.

Furthermore, unlike at familiar macroscopic scales, particles in a quantum field don’t just interact with neighbours but also with their more distant fellows. One important feature of quantum field theories is the “correlation function”, which describes the relationships between particles that are separated from each other in space.

In the past, physicists have relied on calculations and computer simulations to understand these correlation functions because they have been difficult to approach experimentally.

Now scientists from the Vienna University of Technology have created a device that may help to test them in the lab: a “quantum simulator” that uses magnetically trapped, ultra-cold atoms. They report their findings in Nature.

Associate Professor Gavin Brennan, a physicist from Macquarie University who was not involved in the study, thinks this is an exciting result. “They are showing how to probe some essential quantum characters that couldn’t be easily predicted from much simpler models.”

The team created a lab-based quantum system made up of thousands of ultra-cold atoms confined on an atom chip.

The setup is a simple one: the atoms are trapped in two rows which, Brennan says, “could be thought of as atoms trapped in two rows of an egg carton”. The atoms are free to hop between the hollows of the ‘quantum egg carton’.

Even though the movement of the atoms seems simple, the underlying physics of all the potential ways the atoms could move is incredibly complex. Observing these movements will allow the researchers to take empirical measurements of the correlation function.

By monitoring the movements of the atoms, the scientists think that they will be able to verify a range of quantum theories in unprecedented detail.

They hope that these results will provide new insights into the strange behaviour of the young universe, right after the big bang, and explain the properties of new exotic materials, such as topological insulators, used for high-efficiency electronics and sensors.