Non-perturbative strong field physics theory driven by quantum light

Non-perturbative interactions (i.e. interactions that are too strong to be described by so-called perturbation theory) between light and matter have been the subject of many research studies. However, the role played by the quantum properties of light in these interactions and the phenomena arising from them has so far remained largely unexplored.

Researchers at the Technion-Israel Institute of Technology recently presented a new theory that describes the physics underlying quantum light-driven non-perturbative interactions. Their theory, presented in Nature physicsIt could guide future experiments investigating strong field physics phenomena, as well as the development of new quantum technology.

This latest paper was the result of a close collaboration between three different research groups at the Technion, led by principal investigators Professor Ido Kaminer, Professor Oren Cohen and Professor Michael Krüger. Students Alexei Gorlach and Matan Even-Tzur, first authors of the paper, led the study with support and ideas from Michael Burke and Nick Rivera.

“This was a major scientific expedition for us,” Professor Kaminer and Gorlach told Phys.org. “We started thinking about high harmonic generation (HHG) and its quantum properties already in 2019. At that time, light in all HHG experiments was explained classically and we wanted to know when quantum physics would start to play a role there.

“Frankly, it bothered us that so many fundamental phenomena in physics were explained by a completely different theory and therefore could not be linked. For example, HHG was based on a theory that contradicted the theory usually applied to calculate spontaneous emission – and explained each on a different basis.” ”

HHG are highly nonlinear physical processes that entail strong interaction between light and matter. Specifically, it occurs when intense light pulses applied to the material emit so-called high harmonics of the intense driving light pulse.

For several years, Professor Kaminer and his research team have been trying to devise a single framework based on quantum theory that would collectively account for all optical phenomena, including HHG. they The first paper on this topicpublished in Nature Communications In 2020, I presented a proposed version of this unified framework, for analyzing HHG in the language of quantum optics.

“This study contributed to opening up the now emerging field of quantitative HHG,” Professor Kaminer and Gorlach explained. “However, all HHG experiments were driven by classical laser fields. It even seemed that there could not be any quantum light intense enough to create a HHG. However, Works of Professor Maria Chekhova He showed that it is possible to create sufficiently intense quantum light in a form known as a bright compact vacuum. “This motivated our new investigation.”

As part of their new study, Professor Kaminer, Gorlach and their colleagues created a complete framework that describes strong-field physics processes driven by quantum light. To validate their framework theoretically, they applied it to the HHG, and predicted how this process would change if driven by quantum light.

“We have shown that, contrary to expectations, many important features such as intensity and spectrum all change as a result of using a driving light source with different quantum photon statistics,” Professor Kaminer and Gorlach said. “The paper we have written also predicts experimentally possible scenarios that cannot be explained by any other means than by considering photon statistics. These upcoming experiments will be of even greater impact and importance to this emerging field of strong-field quantum optics.”

So far, the work done by this team of researchers has been considered purely theoretical. Their research provides the first theory of non-perturbative processes driven by quantum light, while also demonstrating theoretically that the quantum state of light affects measurable quantities, such as the emitted spectrum.

“The way our theory works is by dividing the driving light into one of two representations called the generalized Glauber distribution or Haussimi distribution, and then using the traditional simulation of the HHG field, the time-dependent Schrödinger equation (TDSE), to simulate separate parts of the distribution,” Professor Kaminer and Gorlach said. , before combining the simulations together to derive the overall result.”

“It is this connection between the community’s standard tools in an optical quantum computation scheme that made our work so powerful and useful – it can be applied to an arbitrary quantum state of light and an arbitrary system of emitters.”

The new theory derived by Professor Kaminer, Gorlach and their colleagues could soon benefit studies in various areas of physics. In fact, their paper envisions taking the idea beyond HHG, to a wide range of non-perturbative processes, all of which could be driven by non-classical light sources.

This theoretical prediction can soon be tested and validated in experimental settings. For example, the team’s theory can be directly applied to the generation of attosecond pulses via HHG, a process that can support the work of quantum sensing and quantum imaging technologies.

In this regard, the team published a recent theoretical paper in Nature photonics that propose controlling attosecond pulse coils using the quantum nature of light, for example showing promising conditions using a combination of classical light and compressed quantum light.

In addition, their theory can be applied to other phenomena based on strong field physics, such as the Compton effect, a process used to generate X-ray pulses.

“We recently published a follow-up paper on this application in Advancement of science“Which ended up coming up earlier due to delays in the peer review process,” Kaminer and Gorlach added about the Compton effect. “We are now working on implementing the experiment discussed theoretically in our paper.

“Another ambitious goal is to generalize the developed theory beyond HHG, and investigate quantum effects in various materials driven by condensed light, which links our new developments in quantum optics to the frontiers of condensed matter physics.”