New way to “see” quantum sound with quantum light

Researchers at the University of East Anglia have introduced an innovative approach, utilizing quantum light to observe quantum sound. In a recent publication on October 2 in Physical Review Letters, they unveil the intricate quantum interplay between vibrations and photons (particles of light) within molecules.

This breakthrough holds the potential to enhance our comprehension of how light and matter interact at the molecular level. Moreover, it could lay the foundation for exploring fundamental questions regarding the role of quantum phenomena in various applications, from emerging quantum technologies to biological systems.

Dr. Magnus Borgh, a physicist at UEA, highlighted the longstanding debate in chemical physics concerning the nature of energy transfer within molecules by light particles. Are these processes fundamentally quantum-mechanical or classical in nature? Molecules, being complex and constantly vibrating, pose challenges in understanding how these vibrations influence quantum processes within them.

Traditionally, scientists have relied on polarization-based techniques, a classical phenomenon, to investigate these processes. However, Dr. Borgh suggests that leveraging techniques from quantum optics, a field dedicated to studying the quantum nature of light and its interactions at the atomic scale, can offer a direct path to exploring genuine quantum effects in molecular systems.

To reveal quantum behavior, researchers examined correlations in the emitted light from molecules placed in a laser field. These correlations indicate the likelihood of two photons being emitted closely together and can be quantified using standard methods.

Ben Humphries, a Ph.D. student in theoretical chemistry at UEA, emphasized that their research demonstrates how the exchange of phonons (quantum sound particles) between a molecule and its environment generates distinct signals in photon correlations.

Although photons are routinely generated and measured in laboratories worldwide, individual phonons, the corresponding sound quanta, cannot be measured in a similar manner. This new discovery provides a valuable toolkit for exploring the realm of quantum sound within molecules.

Lead researcher Dr. Garth Jones from UEA’s School of Chemistry expressed hope that their work might inspire the development of innovative experimental techniques for directly detecting individual phonons—an exciting prospect on the horizon.

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