Squeezed Photons Enable Real-Time Monitoring of Valley Excitons in 2D Materials

The study of how materials respond to light at incredibly short timescales is fundamental to advances in fields like optoelectronics and photocatalysis, but conventional methods have limitations in both time and energy resolution. Now, Jiahao Joel Fan, Feihong Liu, and Dangyuan Lei, all from City University of Hong Kong, alongside Zhedong Zhang et al., demonstrate a new approach to transient absorption spectroscopy using correlated photons, known as squeezed light. This technique harnesses the unique properties of squeezed light to achieve significantly enhanced time and energy resolution, allowing researchers to observe the fleeting behaviour of excited states within materials with unprecedented clarity. The team’s work reveals a pathway to real-time monitoring of valley excitons in materials like monolayer transition metal dichalcogenides, and importantly, shows that optimal performance doesn’t require extremely strong squeezing, opening up practical possibilities for this powerful new method.

Squeezed Light and Entangled Photon Spectroscopy

This compilation details research into quantum-enhanced spectroscopy, particularly the use of squeezed light and entangled photons. The core principle is that these non-classical light sources can improve spectroscopic measurements beyond what’s possible with classical light, enhancing signal-to-noise ratios and enabling novel spectroscopic mechanisms. This allows for enhanced sensitivity, improved resolution, and new contrast mechanisms in various spectroscopic techniques, including two-photon absorption, resonance fluorescence, and coherent Raman spectroscopy. Research areas include molecular sensing, chemical dynamics, quantum control of molecular processes, and material characterization, supported by theoretical modeling and techniques like Hong-Ou-Mandel interferometry. Recent advances focus on ultrafast spectroscopy with entangled photons, quantum-enhanced time-domain spectroscopy, and two-dimensional fluorescence spectroscopy, with correlated photons used to estimate weak absorption signals. This compilation represents a comprehensive overview of the rapidly evolving field, highlighting the potential of non-classical light sources to revolutionize spectroscopic measurements and unlock new insights into the fundamental properties of matter.

Squeezed Light Reveals Ultrafast Nanoscale Dynamics

Researchers have developed a new spectroscopic technique using squeezed photons to observe the incredibly fast dynamics of materials at the nanoscale. This method, termed pump-probe-fluorescence spectroscopy, allows scientists to monitor the behavior of excitons in two-dimensional materials with unprecedented temporal and energy resolution. By harnessing the unique correlations within squeezed light, this technique overcomes the limitations of conventional methods, revealing details of exciton behavior previously hidden from view, including the conversion between “bright” and “dark” excitons and the formation of bi-excitons. The implications of this research extend beyond fundamental materials science, offering potential advancements in fields like photocatalysis and optoelectronics. By providing a means to precisely control and monitor the flow of energy within materials, this technique could pave the way for the design of more efficient solar cells, faster electronic devices, and novel quantum technologies. The ability to probe these dynamics with such precision promises a deeper understanding of how materials behave at the quantum level, opening up exciting new avenues for scientific discovery and technological innovation.

Squeezed Photons Unlock Ultrafast Material Dynamics

This research demonstrates a new approach to ultrafast spectroscopy using squeezed photons, a type of light with reduced noise and enhanced quantum correlations. The team developed a method capable of sensing real-time dynamics within materials, achieving a time-energy resolution beyond the limitations of conventional laser pump-probe techniques. This advancement was successfully applied to study valley excitons in monolayer semiconductors, allowing for detailed observation of the conversion between bright and dark excitons, a process previously hindered by temporal-spectral resolution constraints. The signal enhancement achieved with squeezed photons is several orders of magnitude greater than that from entangled photon pairs, providing a significant advantage for time-domain spectroscopy and offering a pathway to selectively access material correlation functions.

The authors found that an intermediate level of squeezing proves most effective for this type of spectroscopy. Future work may focus on extending this technique to investigate ultrafast dynamics in more complex materials, potentially opening new frontiers in fields like photocatalysis and optoelectronics. This proof-of-principle demonstration highlights the potential of quantum advantage to significantly improve spectroscopic measurements and deepen our understanding of material properties.