Fragile quantum entanglement may survive chaos of chemical reactions

Odd quantum phenomena can survive the havoc of a chemical reaction, researchers have found. This could eventually prove useful for emerging quantum technologies or reveal surprising quantumness in nature.

“Typically, people describe chemical reactions as a very chaotic thing: you put a whole bunch of atoms in there, they do a little ‘dance’ and then when products are formed, they just fly out,” says Lingbang Zhu at Harvard University. He and his colleagues set out to see what this does to the quantum properties of molecules.

Quantum objects can act as both particles and waves. The researchers focused on a property called coherence, which reflects molecules’ wave-like character. Quantum entanglement, which makes objects inextricably linked even across massive distances, is closely related to coherence. So, the experiment offers insight into entanglement’s fate during a chemical reaction.

Molecules’ quantum properties are most prominent at extremely low temperatures, so the researchers studied potassium and rubidium atoms at mere billionths of a degree above absolute zero. To achieve this chill, they placed the atoms in an airless chamber and applied a precise combination of laser beams, magnetic fields and pulses of microwaves to cool them and combine them into molecules.

These molecules spontaneously underwent chemical reactions, but Zhu and his colleagues carefully controlled their initial quantum states, including their coherence and entanglement. After the reaction, they assessed the quantum properties of the resulting products. These molecules managed to keep their coherence, or wave-like property – so much so that they overlapped and interfered with each other like two conventional waves with mismatched peaks and valleys.

Yong Chen at Purdue University in Indiana says experiments like this open the door for a new stage of quantum research where scientists are not just passively uncovering quantum properties but finding ways to control them instead. However, he says, future experiments could still diagnose molecules’ entanglement more directly.

The team is now investigating how to leverage molecules’ quantum properties to control what kind or how many products the reactions make, and to glean hints of whether chemical reactions that happen in nature could contain more quantumness than previously thought, says Zhu.