Ultracold Molecules Advance Quantum Computing

Radical cooling could hold great potential for quantum computing and simulations.

To that end, Purdue University researchers have created an ultracold molecule using lasers to remove the kinetic energy and cool the atoms to 0 K (-273 °C / -459 °F) — the lowest temperature possible in the universe. At extremely low temperatures, the atoms come to a near standstill, creating new kinds of chemical interactions that are mainly quantum mechanical.

The investigators merged two heteronuclear atoms in a technique known as photoassociation, inducing a chemical bond to form a lithium-rubidium molecule. Although other researchers have used this technique to create cold molecules from other alkali metals, this is the first bialkali molecule to be made cold.

The Purdue team performed the process inside a magneto-optical trap, which uses a vacuum chamber, magnetic coils and a series of lasers to cool and trap the atoms.

The lithium-rubidium molecules also can be produced in large quantities, making them ideal for applications such as quantum computing. Because of their significant dipole moment, which enables interaction between molecules, they could be used as quantum bits.

The researchers believe that this could lead to entanglement, which puts the quantum states in between one and zero to increase the capacity to process information.

“In quantum computing, the larger the dipole moment, the stronger the interaction would be between molecules, and you need that interaction,” said researcher Daniel S. Elliott, a professor of electrical and computer engineering and physics at Purdue. “They need to interact with each other in order to affect each other — the key to entanglement.”

The ultracold molecules could be produced in their “ground, polar state,” said researcher Sourav Dutta. This would provide the lowest possible rotational, vibrational and electronic energy, making the molecules more stable and easier to control.

The research is published in Europhysics Letters and in Physical Review A.

For more information, visit: www.purdue.edu.