Quantum boomerang: Physicists observe strange effect for first time

Hundreds of thousands of lithium atoms cooled to near absolute zero exhibit a strange quantum effect a bit like a boomerang

By Karmela Padavic-Callaghan

Researchers have managed to demonstrate a strange phenomenon known as the quantum boomerang effect for the first time.

David Weld at University of California, Santa Barbara and his colleagues cooled hundreds of thousands of lithium atoms close to absolute zero inside a small vacuum-sealed box. They used lasers to arrange the lithium atoms in a line and keep them in a particular quantum state that they hoped would reveal the boomerang effect.

The researchers then used the laser to nudge the atoms. This resulted in them going from having zero average momentum to having a positive average momentum. If the same change happened to a ball it would roll away, but due to the quantum boomerang effect, the team found that the atoms’ average momentum soon returned to zero.

Theorists had originally proposed that this boomerang effect could happen with electrons moving inside a crystal filled with particles of dirt, but that has proved difficult to demonstrate and study. Weld and the team sidestepped that difficulty by instead focusing on very cold atoms which can be precisely manipulated with lasers.

Weld and colleagues presented the new experiment at the DAMOP conference in Orlando, Florida in May.

He says that the next goal is to determine if boomeranging happens when super cold atoms interact with each other very intensely. Behaviour of such very coordinated atoms is not well understood, so seeing them boomerang could uncover something new about quantum physics.