Quantum disruption: Chemical reactions rivaling black holes

Research from Rice University and the University of Illinois at Urbana-Champaign shows that molecules can scramble quantum messages as effectively as black holes, which has implications for chemical physics and Quantum computing.

If you were to drop a message in a bottle into a bottle black hole, all information in it, down to the quantum level, will become completely chaotic. Because this disruption occurs in black holes as quickly and completely as quantum mechanics allows, they are often considered nature’s ultimate information disruptors.

However, new research by Rice University theorist Peter Wolynes and collaborators at the University of Illinois at Urbana-Champaign shows that molecules can be as powerful as black holes in disrupting quantum information. Combining mathematical tools from black hole physics and chemical physics, they showed that quantum information scrambling occurs in chemical reactions, reaching almost the same quantum mechanical limits as in black holes.This work has been published online in Proceedings of the National Academy of Sciences.

Chemical reactions and quantum disturbances

“This research solves a long-standing problem in chemical physics, which has to do with how quickly quantum information gets scrambled in molecules,” Wallings said. “When people think about the reaction in which two molecules come together, they Atoms are thought to perform only one movement to form or break a bond.

“But from a quantum mechanical perspective, even a very small molecule is a very complex system. Like orbits in the solar system, molecules have a huge number of possible ways they can move – what we call quantum states. When chemical reactions When this happens, the quantum information about the quantum states of the reactants becomes scrambled, and we want to know how the scrambled information affects the rate of the reaction.

To better understand how quantum information is scrambled in chemical reactions, scientists borrowed a mathematical tool commonly used in black hole physics called an out-of-order correlator (OTOC).

“OTOCs were actually invented about 55 years ago in a very different context, when they were used to study how electrons in superconductors were affected by interference from impurities,” Wolynes said. “They are very special objects used in the theory of superconductivity. Next, they were used by physicists in the 1990s to study black holes and string theory.

OTOC measures how many adjustments to one part of a quantum system at one moment in time affects the motion of other parts, providing insight into how quickly and efficiently messages propagate throughout the molecule. They are quantum analogs of the Lyapunov exponent, a measure of unpredictability in classical chaotic systems.

“The rate at which OTOC increases over time tells you how quickly information is scrambled in a quantum system,” said Martin Gruebele, a chemist at the University of Illinois at Urbana-Champaign and co-author of the paper. “Chemists are very ambivalent about how many seemingly random states are being accessed, because perturbation is necessary to achieve the reaction goal, but it also disrupts your control of the reaction.

“Understanding under what circumstances a molecule disrupts a message and under what circumstances it does not may allow us to better control the response. Understanding OTOCs essentially gives us an understanding of when this information is truly gone and beyond our control Scope, and when we can still use it to control the results to limit.

In classical mechanics, particles must have enough energy to overcome the energy barrier for a reaction to occur. However, in quantum mechanics, it is possible for particles to “tunnel” through this barrier even if they do not have enough energy. OTOC’s calculations show that at low temperatures where tunneling dominates, low activation energy chemical reactions can scramble messages close to the quantum limit, as in the case of black holes.

Nancy Makri, also a chemist at the University of Illinois at Urbana-Champaign, uses a path integration method she developed to study what happens when simple chemical reaction models are embedded in larger systems. The system may be the vibration of the macromolecule itself or the solvent, and tend to suppress chaotic motion.

“In another study, we found that the environment tends to make things more regular and dampen the effects we’re talking about,” Macri said. “So we calculated OTOC for a tunnel system that interacted with the larger environment, and what we saw was that the disturbance was suppressed—the behavior changed dramatically.”

Practical applications and future research

One area of ​​practical application for this research is to constrain how tunneling systems can be used to build qubits for quantum computers. People need to minimize information disruption between interactive tunneling systems to improve the reliability of quantum computers. The research may also have relevance for light-driven reactions and advanced materials design.

“It’s possible to extend these ideas to processes where you don’t just have tunneling in one particular reaction, but you have multiple tunneling steps, because that’s what electronic conduction is involved in many of the new soft materials. content.

Reference: “Quantum Information Scrambling and Chemical Reactions” by Chenghao Zhang, Sohang Kundu, Nancy Makri, Martin Gruebele and Peter G. Wolynes, April 1, 2024 Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2321668121

Wallings is the Brad Welch Foundation Professor of Science, Professor of Chemistry, Biochemistry and Cell Biology, Physics and Astronomy, Materials Science, and Nanoengineering, and the Center for Theoretical Biophysics at Rice University. Co-director of the center, the center is funded by the National Science Foundation. Co-authors Gruebele is the James R. Eiszner Chair Professor of Chemistry; Makri is the Edward William and Jane Marr Gutgsell Professor and Professor of Chemistry and Physics; Chenghao Zhang is a graduate student in physics at the University of Illinois at Urbana-Champaign and is now a postdoctoral fellow at the Pacific Northwest National Laboratory; Sohang Kundu recently received his Ph.D.PhD in Chemistry from the University of Illinois, currently a postdoctoral fellow Columbia University.

This research was supported by the National Science Foundation (1548562, 2019745, 1955302) and the Brad Welch Chair at Rice University (C-0016).