Novel Experiment Distinguishes Between Quantum Decoherence

Although Bose-Einstein condensates are usually very large, consisting of hundreds of thousands of atoms, they still follow quantum mechanics laws, which makes them so important in the study of the properties of quantum mechanics.

"Over the years, work on Bose-Einstein condensates, known as BECs, have led to more and more interesting phenomena. This is because they behave according to quantum mechanics, and are fairly large objects. The goal is to use them to explore opportunities in the quantum regime." says Artur Widera from Harvard University, and part of a team that published recently a paper called "Quantum Spin Dynamics of Mode-Squeezed Luttinger Liquids in Two-Component Atomic Gases".

"In experiments, we see that quantum properties somehow decay. We call this decoherence. They do so for two main reasons. The first is technical. It usually means that we have done something wrong. The second reason is due to the interactions between atoms that go on at the level and make our signals look like decoherence. At the same time these interactions can lead to probably the most intriguing phenomena in quantum physics, namely quantum correlations," explained Widera.

Because the two reasons cannot be distinguished with the current tools, Widera and his colleagues thought at a mean to make a difference by encouraging more interactions inside a BEC squeezed into a one-dimensional trap.

"In solid state physics, we find that there are interesting phenomena in the lower dimensions that are not possible in three dimensions. Experimentally, we used, not a single system, but an array of one-dimensional systems," said Widera.

He continues by saying that the team was able for the first time to distinguish between the decoherence states produced by interactions and the technical issues. "Additionally, we even saw the quantum fluctuations play a big role, and that they dominate the behavior. This is a fundamental property of one-dimensional quantum systems, which in our experiment could be understood thanks to our colleagues from Harvard. Now, we've been able to see and understand what effects are going on."

Nevertheless, controlling such interactions at this moment is out of the question. The experiment tried to do so and failed due to poor understanding of the processes taking place. "Right now this work deals with fundamental quantum physics. Think how it will be when we know how to control these issues," says Widera.