The new strategy reveals the ‘full chemical complexity’ of quantum decoherence

Rochester researchers report a strategy to understand how quantum coherence is lost for solvent molecules with full chemical complexity. The findings open the door to rational modulation of quantum coherence through chemical design and functionalization. Credit: Anny Ostau De Lafont

In quantum mechanics, particles can exist in multiple states at the same time, defying the logic of everyday experiences. This property, known as quantum superposition, is the basis of emerging quantum technologies that promise to revolutionize computing, communication, and sensing. But quantum superpositions face a significant challenge: quantum decoherence. During this process, the delicate superposition of quantum states breaks down when interacting with its surroundings.

To unlock the power of chemistry to create complex molecular architectures for practical quantum applications, scientists need to understand and control quantum decoherence so that they can design molecules with specific quantum coherence properties . Doing so requires figuring out how to rationally change the chemical structure of the molecule to modulate or reduce quantum decoherence.

To that end, scientists need to know the “spectral density,” the quantity that summarizes how fast the environment moves and how strongly it interacts with the quantum system.

Until now, quantifying this spectral density in a way that accurately reflects the intricacies of molecules remains difficult both theoretically and experimentally. But a group of scientists has developed a method to obtain the spectral density of solvent molecules using a simple resonance Raman experiment in a method that captures the full complexity of the chemical environment.

Led by Ignacio Franco, an associate professor of chemistry and physics at the University of Rochester, the team published their findings in Proceedings of the National Academy of Sciences.

Using the obtained spectral density, it is possible not only to understand how fast the decay occurs but to determine which part of the chemical environment is more responsible for it. As a result, scientists can now map decoherence pathways to connect molecular structure to quantum decoherence.

“Chemistry builds from the idea that molecular structure determines the chemical and physical properties of matter. This principle guides the modern design of molecules for medicine, agriculture, and energy applications. Using this strategy, we can finally begin to develop chemical design principles for emerging quantum technologies,” said Ignacio Gustin, a chemistry graduate student at Rochester and the study’s first author.

The breakthrough came when the team realized that resonance Raman experiments provided all the information needed to study decoherence with full chemical complexity. Such experiments are often used to investigate photophysics and photochemistry, but their utility for quantum decoherence has not yet been appreciated.

Key insights emerged from discussions with David McCamant, an associate professor in Rochester’s chemistry department and an expert in Raman spectroscopy, and with Chang Woo Kim, now on the faculty of Chonnam National University in Korea and is an expert in quantum decoherence, while he is a postdoctoral researcher in Rochester.

The team used their method to show, for the first time, how the electronic superpositions of thymine, one of the building blocks of DNA, are broken in 30 femtoseconds (one femtosecond is one millionth of one billionth of one seconds) after UV absorption. light.

They found that some molecular vibrations dominate the initial steps of the decoherence process, while the solvent dominates the later stages. Additionally, they discovered that chemical modifications to thymine can significantly alter the decoherence rate, with hydrogen-bond interactions near the thymine ring leading to faster decoherence.

Ultimately, the team’s research paves the way toward understanding the chemical principles that govern quantum decoherence. “We are excited to use this strategy to finally understand quantum decoherence in molecules with full chemical complexity and use it to develop molecules with strong cohesive properties,” said said Franco.

More information:
Ignacio Gustin et al, Mapping electronic decoherence pathways in molecules, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2309987120

Provided by the University of Rochester

Citation: New strategy reveals ‘full chemical complexity’ of quantum decoherence (2023, December 19) retrieved 21 December 2023 from full-chemical-complexity.html

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