Non-perturbative interactions between light and matter have long been a subject of interest for researchers. These interactions involve the quantum properties of light and the phenomena that arise from them. However, the understanding of these phenomena has been limited, with each foundational theory explaining different aspects of the interactions. To address this issue, researchers from Technion–Israel Institute of Technology have proposed a new theory that describes the physics underlying non-perturbative interactions driven by quantum light. This theory has the potential to guide future experiments and promote the development of quantum technology.
The research at Technion began with the curiosity to understand high harmonic generation (HHG) and its quantum features. Previously, HHG experiments were explained classically, but the researchers aimed to determine when quantum physics starts to play a role in this phenomenon. The discrepancy between the theories used to explain HHG and spontaneous emission was also a concern for the researchers. They sought to establish a unified framework that could account for all photonics phenomena, including HHG, based on quantum optics.
While classical laser fields were traditionally used to drive HHG experiments, the researchers became aware of the possibility of using intense quantum light known as bright squeezed vacuum. This discovery motivated their new investigation. In their study, the researchers developed a comprehensive framework that describes strong-field physics processes driven by quantum light. Using this framework, they predicted how HHG would change when driven by quantum light, contrary to expectations.
One significant finding of their research is that important features, such as intensity and spectrum, change when a different quantum photon statistics driving light source is used. The researchers predicted experimentally feasible scenarios that can only be explained by considering the photon statistics. These upcoming experiments will undoubtedly have a profound impact on the rising field of strong-field quantum optics.
The work conducted by the Technion team is currently theoretical. However, their paper marks the first theory of non-perturbative processes driven by quantum light. They demonstrated that the quantum state of light influences measurable quantities, such as the emitted spectrum. Their theory works by splitting the driving light into the generalized Glauber distribution or the Husimi distribution. The conventional simulations of the HHG field, known as the time-dependent Schrodinger equation (TDSE), are then used to simulate the parts of the distribution separately before combining them to derive the overall result. This integration of standard tools into a quantum-optical calculation scheme makes their work powerful and applicable to any quantum state of light and any system of emitters.
The newly derived theory has the potential to inform studies in various areas of physics. Beyond HHG, it can be applied to a wide range of non-perturbative processes that can be driven by non-classical light sources. Experimental validation of this theory is highly anticipated. For example, the theory can be directly applied to the generation of attosecond pulses via HHG, which has implications for quantum sensing and imaging technologies. Another potential application is in the Compton effect, which is used to generate X-ray pulses. In fact, the researchers have already published a follow-up paper on this application in Science Advances, and they are working on performing the experiment discussed in the paper.
The researchers also have an ambitious goal of extending the developed theory beyond HHG. They aim to investigate quantum effects in various materials driven by intense light, bridging the gap between quantum optics and condensed matter physics. This generalization would open new avenues for exploration and innovation in the field.
The research conducted at Technion sheds light on the unexplored role of quantum light in non-perturbative interactions. By proposing a new theory and demonstrating its potential implications, the researchers have laid the foundation for future experiments and the development of quantum technology. The integration of quantum photon statistics into the calculations provides valuable insights into phenomena such as high harmonic generation and offers new possibilities for further research in strong-field physics. As this research unfolds, it has the potential to revolutionize our understanding of light-matter interactions and pave the way for technological advancements in quantum optics and condensed matter physics.
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