A theory of unperturbed strong-field physics driven by quantum light

Non-perturbative interactions (that is, interactions that are too strong to be described by what is called perturbation theory) between light and matter have been the subject of many research studies. However, the role that the quantum properties of light play 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 non-turbulent interactions driven by quantum light. 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 Prof. Edo Kamener, Prof. Oren Cohen and Prof. Michael Kreuger. Students Alexei Gorlach and Matan Even Zur, first authors of the paper, led the study with support and ideas from Michael Burke and Nick Rivera.

“This has been a major scientific journey for us,” Prof 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 find out when quantum physics starts to play a role there.

“Frankly, we were disturbed that many fundamental phenomena in physics were explained by a completely different theory and thus could not be linked. For example, the HHG drew on a theory that contradicted the one normally applied to account for spontaneous emission – and explained each on a different basis. ”

HHG are highly nonlinear physical processes that entail a strong interaction between light and matter. Specifically, it occurs when intense pulses of light applied to the material cause what are called the high harmonics of an intense pulsed light pulse to be emitted.

For several years, Professor Kaminer and his research team have tried to devise a single framework based on quantum theory that would collectively take into account all optical phenomena, including the HHG. they 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 has opened up the now emerging field of quantitative HHG,” explained Prof. Kaminer and Gorlach. However, all of the HHG experiments were driven by classical laser fields. It even seemed that there could never be any quantum light intense enough to create the HHG. However, Works of Professor Maria Chekhova showed that it is possible to create sufficiently intense quantum light in a form known as a bright compressed vacuum. This motivated our new investigation.”

As part of their new study, Prof. Kaminer, Gorlach and their colleagues created a complete framework describing strong-field physics processes driven by quantum light. To theoretically validate their framework, they applied it to HHG, and predicted how this process would change if it were 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,” said Professor Kaminer and Gorlach. “Our paper also predicts experimentally possible scenarios that can only be explained by any other means by looking at photon statistics. These upcoming experiments will be of even greater influence and significance to this emerging field of strong-field quantum optics.”

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

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

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

The new theory derived by Prof. Kaminer, Gorlach and their colleagues could soon inform studies in different 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 applied directly to the generation of attosecond pulses via HHG, a process that can support the work of quantum sensing and quantum imaging techniques.

In this regard, the team published a recent theoretical paper in Nature photonics which propose to control attosecond pulse coils using the quantum nature of light, eg 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 Science advances“, which ended up coming to light earlier because of delays in the peer-review process,” Kaminer and Gorlach add 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 far beyond HHG, and to investigate quantum effects in various materials driven by intense light, which links our new developments in quantum optics to the frontiers of condensed matter physics.”