If you approach a chemical reaction to the quantum level, you will see that the particles behave like waves that can fluctuate and collide. Scientists have long sought to understand quantum coherence, the ability of particles to maintain phase relationships and exist in more than one state at the same time; It’s like synchronizing all the parts of the wave. It remains an open question whether quantum coherence can be maintained through a chemical reaction in which bonds are dynamically broken and formed.
Now a team of scientists from Harvard has demonstrated for the first time the existence of quantum coherence in a chemical reaction involving ultracold molecules. These discoveries highlight the potential to use chemical reactions for future applications in quantum information science.
“I am extremely proud of our work investigating a very fundamental feature of a chemical reaction where we don’t really know what the outcome will be,” said Professor Kang-Kuen Nee, the Theodore William Richards Professor of Chemistry. Department of Physics. “It was really cool to do an experiment to find out what Mother Nature was telling us.”
Observation of quantum dynamics
In a paper published in the journal Science, the researchers detail how they studied a specific chemical reaction of atomic exchange in an extremely cold environment involving alkaline molecules 40K87Rb, in which two molecules of potassium and rubidium (KRb) react to form potassium (K2). and rubidium. (Rb2) products. By manipulating magnetic fields, the team prepared the first nuclear spins in KRb molecules in an entangled state and then confirmed the result with special instruments. The Ni laboratory was able to monitor nuclear spin degrees of freedom in an ultracold environment and observe the complex quantum dynamics underlying the reaction process and outcome.
The work was carried out by several members of Nie’s laboratory, including Yi-Hsiang Liu, Linbang Zhu, Jeshurun Luke, JJ Arfor Houman, Mark K. Babin, and Ming-Guang Hu.
Using laser cooling and magnetic trapping, the team was able to cool its molecules to just a fraction of a degree above absolute zero. In this extremely cold environment of just 500 nanoKelvins, molecules slow down, allowing scientists to isolate, manipulate and detect individual quantum states with extraordinary precision. This control facilitates the observation of quantum effects such as superposition, entanglement and coherence, which play fundamental roles in the behavior of molecules and chemical reactions.
By applying sophisticated techniques, including coincidence detection, in which researchers can select exact pairs of reaction products from individual reaction events, the researchers were able to precisely map and identify reaction products. They had previously observed that the energy distribution between the rotational and translational motions of the product molecules was chaotic. [Nature 593, 379-384 (2021)]. It is therefore surprising to find quantum order in the form of coherence in the same fundamental reaction dynamics, this time in the degrees of freedom of nuclear spin.
The results showed that quantum coherence was maintained within the degrees of freedom of the nuclear spin throughout the entire reaction. Maintaining coherence meant that the product molecules K2 and Rb2 were in an entangled state, inheriting the entanglement from the reactants. Additionally, by deliberately causing the reactants to decohere, the researchers demonstrated that they gained control over the distribution of the reaction product.
In the future, Nee hopes to clearly demonstrate that product molecules are entangled, and he is optimistic that quantum coherence can be maintained in non-ultracold environments.
“We believe the result is general and not limited to cold temperatures and may occur in warmer and wetter conditions,” Nee said. “This means there is a mechanism for chemical reactions that we didn’t know about before.”
First co-author and graduate student Lingbang Zhu sees the experiment as an opportunity to expand people’s understanding of chemical reactions in general.
“We are investigating phenomena that may occur in nature,” Zhu said. “We can try to extend our concept to other chemical reactions. Although the electronic structure of KRb is different, the idea of interfering with reactions can be generalized to other chemical systems.”
Source: Port Altele
