Coherent superpositions and entanglement are hallmarks of quantum mechanics, but they are fragile and can easily be perturbed by their environment. Selected isolated physical systems can maintain coherence and generate entanglement using well-controlled interactions. Chemical reactions, where bonds break and form, are highly dynamic quantum processes. A fundamental question is whether coherence can be preserved in chemical reactions and then harnessed to generate entangled products. Here we investigate this question by studying the 2KRb $\rightarrow$ K $_2$ + Rb $_2$ reaction at 500 nK, focusing on the the nuclear spin degrees of freedom. We prepare the initial nuclear spins in KRb in an entangled state and characterize the preserved coherence in nuclear spin wavefunction after the reaction. The data are consistent with full coherence at the end of the reaction. This suggests that entanglement can be prepared within the reactants, followed by a chemical reaction that produces separate, entangled molecules. We additionally demonstrate control of the reaction product state distribution by deliberately decohering the reactants.Coherent superpositions and entanglement are hallmarks of quantum mechanics, but they are fragile and can easily be perturbed by their environment. Selected isolated physical systems can maintain coherence and generate entanglement using well-controlled interactions. Chemical reactions, where bonds break and form, are highly dynamic quantum processes. A fundamental question is whether coherence can be preserved in chemical reactions and then harnessed to generate entangled products. Here we investigate this question by studying the 2KRb $\rightarrow$ K$_2$ + Rb$_2$ reaction at 500 nK, focusing on the the nuclear spin degrees of freedom. We prepare the initial nuclear spins in KRb in an entangled state and characterize the preserved coherence in nuclear spin wavefunction after the reaction. The data are consistent with full coherence at the end of the reaction. This suggests that entanglement can be prepared within the reactants, followed by a chemical reaction that produces separate, entangled molecules. We additionally demonstrate control of the reaction product state distribution by deliberately decohering the reactants.

arXiv:2310.07620Oct 11, 20231 citation

Nontransient phase-coherent effects in multilevel systems

James P. Stone, Myron F. Goodman

We examine the effect of including phase-coherent coupling between a driving laser field and a gas of multilevel molecules ( $N=20,40$ ) on a nontransient time scale. Although multiphoton enhancement of upper energy-level populations is known to be negligible for systems containing a small number of levels ( $N=3,4$ ), such coherent enhancements increase strongly as a function of the number of consecutive radiatively coupled levels, and may play a significant role in recently observed laser-induced chemical reactions.We examine the effect of including phase-coherent coupling between a driving laser field and a gas of multilevel molecules ($N=20,40$) on a nontransient time scale. Although multiphoton enhancement of upper energy-level populations is known to be negligible for systems containing a small number of levels ($N=3,4$), such coherent enhancements increase strongly as a function of the number of consecutive radiatively coupled levels, and may play a significant role in recently observed laser-induced chemical reactions.

Physical Review AJul 1, 197617 citations

Production of Coherent Radiation by Atoms and Molecules

Charles Hard Townes

Springer eBooksJan 1, 19814 citations

\rightarrow

_2

+ Rb

_2

reaction at 500 nK, focusing on the the nuclear spin degrees of freedom. We prepare the initial nuclear spins in KRb in an entangled state and characterize the preserved coherence in nuclear spin wavefunction after the reaction. The data are consistent with full coherence at the end of the reaction. This suggests that entanglement can be prepared within the reactants, followed by a chemical reaction that produces separate, entangled molecules. We additionally demonstrate control of the reaction product state distribution by deliberately decohering the reactants.

We examine the effect of including phase-coherent coupling between a driving laser field and a gas of multilevel molecules (

N=20,40

) on a nontransient time scale. Although multiphoton enhancement of upper energy-level populations is known to be negligible for systems containing a small number of levels (

N=3,4

), such coherent enhancements increase strongly as a function of the number of consecutive radiatively coupled levels, and may play a significant role in recently observed laser-induced chemical reactions.