Periodic Reporting for period 1 - Q-light-matter (Nonequilibrium Quantum Matter Coupled To Quantum Light)
Reporting period: 2020-12-01 to 2022-11-30
The project ”Nonequilibrium Quantum Matter Coupled To Quantum Light” studies how coupling material to light could be used to probe and to control its properties. Interaction between light and matter is a fundamental physical phenomenon that could be observed when atoms are coupled to photons in optical cavities. Experimental progress in coupling atoms, molecules, quantum dots and Josephson junctions to cavity photons opens the possibility of using light to control and design properties of the material. On the applicational side, it has been previously demonstrated experimentally that it is possible to enhance conductivity in organic semiconductors, to modify the superconducting transition temperatures, and even to induce topological phases of matter by coupling materials to electromagnetic field. Topology is an important field of research in modern condensed matter physics due to its application for quantum technologies. Topological superconductors and insulators are examples of the materials that could be used for such applications. Topological superconductivity is associated with formation of zero-energy modes at the edges of the system, which are called Majorana bound states. Such bound states could be used as qubits for topological quantum computing due to their stability against perturbations. The prospect of using Majorana bound states as topological qubits is currently hampered by the difficulty in observing them in transport experiments. Proposing a novel approach based on spectroscopy with photons in microwave cavities is highly needed at the moment. Electrical devices based on Josephson junctions have many practical applications such as qubits, metamaterials, Josephson bifurcation amplifiers or detectors of mesoscopic systems, such as rf-SQUIDS or topological materials. The current flowing in the spectrometer is proportional to the photon absorption rate that contains the information about the mesoscopic system. Building a theory for the Josephson spectroscopy opens a way to probe new physics in various mesoscopic systems. When the light-matter coupling is strong, cavity photons can modify material properties. Using light to control topological properties of quantum matter is an important open question in this perspective.
The overall objectives addressed in the projects have been to study the following physical phenomena: (1) Strong coupling of electrons and photons in mesoscopic systems; (2) Collective phases of electrons and photons out of equilibrium; (3) Generation of topological states by photons.
The overall objectives addressed in the projects have been to study the following physical phenomena: (1) Strong coupling of electrons and photons in mesoscopic systems; (2) Collective phases of electrons and photons out of equilibrium; (3) Generation of topological states by photons.
The project in the field of theoretical condensed matter physics addressed the questions on using coupling to cavity photons as a way to detect and to modify properties of various mesoscopic systems. The main results of the project consist in building a theory of excitation spectra of mesoscopic system coupled to Josephson junction spectrometer and in proposing a new scheme for detecting Majorana bound states in topological superconductors. Moreover, the project derived the general formalism for describing the coupling between interacting electronic systems and cavity photons valid in the ultarstrong coupling regime achieved in the state-of the-art experiments performed in the field. This framework was used to resolve the issue of quantum phase transitions being absent in the strongly correlated electronic system coupled to a single mode cavity. This project also demonstrated that coupling to cavity photons is a novel way to modify the topological criterion in the prototype model of topological insulator.
The project resulted in three peer-reviewed publications in top-tier domain journals (Physical Review B and Communications Physics) and one additional arXiv preprint (the manuscript is now undergoing a review process at Physical Review B). The results were also presented at two conferences (as a poster presentation in 2021 and as an invited talk in 2022) and seven invited seminar talks at various Universities in Europe.
To promote the novel research field of light-control of quantum materials, the workshop on “Cavity Control of Quantum Matter” was organised at Collège de France, Paris, France (from 17/10/2022 to 18/10/2022). The two-day workshop included sixteen scientific talks by the top scientists from France, Italy, Spain, Germany, Switzerland, and Poland, and was open to the general public. Around fifty people attended the workshop, including students and postdocs working in the research institutes in Paris area as well as members of the general public.
During the action, the Researcher took part in various training activities, such as Summer Schools in Physics and French language classes. The Summer Schools offered training on numerical simulations, quantum technologies and hybrid light-matter systems, directly related to the project.
The project resulted in three peer-reviewed publications in top-tier domain journals (Physical Review B and Communications Physics) and one additional arXiv preprint (the manuscript is now undergoing a review process at Physical Review B). The results were also presented at two conferences (as a poster presentation in 2021 and as an invited talk in 2022) and seven invited seminar talks at various Universities in Europe.
To promote the novel research field of light-control of quantum materials, the workshop on “Cavity Control of Quantum Matter” was organised at Collège de France, Paris, France (from 17/10/2022 to 18/10/2022). The two-day workshop included sixteen scientific talks by the top scientists from France, Italy, Spain, Germany, Switzerland, and Poland, and was open to the general public. Around fifty people attended the workshop, including students and postdocs working in the research institutes in Paris area as well as members of the general public.
During the action, the Researcher took part in various training activities, such as Summer Schools in Physics and French language classes. The Summer Schools offered training on numerical simulations, quantum technologies and hybrid light-matter systems, directly related to the project.
This MSCA broadened the frontiers of using quantum light to probe and control properties of materials. The project results are important for understanding the fundamental phenomenon of light-matter interaction in strongly correlated electronic systems coupled to photons and has a potential application in the quantum platforms based on topological materials. The main results of the project include developing theory of the Josephson junction spectroscopy for mesoscopic systems, proposing new detection protocols for Majorana bound states in topological superconductors based on microwave spectroscopy, derivation of the form of light-matter interaction in many-body systems, and demonstrating the light-control of the topological properties in electronic model, none of which was previously available in the state of the art. In particular, theoretical study of the spectroscopy of an rf-SQUID coupled to a Josephson spectrometer allowed to explain the linear to non-linear transition in the photon absorption rate observed in the experiment, thus opening a way towards future application of this technique to probe quantum materials. Majorana bound states emerging in topological superconductors are at the center of research fields focused on topological phases of matter and quantum technologies. However, practical realizations are currently hampered by the difficulty in distinguishing Majorana bound states from other trivial bound states in conductance measurements. Within the action, it was proposed to use microwave spectroscopy to probe signatures of the Majorana bound states. This proposal goes beyond the standard experimental approach for Majorana detection. Recent experimental advances in reaching the ultrastrong coupling regime between the material and photons required building the theoretical description of hybrid electron-photon systems. Deriving the model for light-matter coupling, performed as part of this action, answered the fundamental question of quantum phase transition in electronic system coupled to photons and demonstrated that the trivial phase of the prototype model for topological insulator could be turned into the topological one with light.
The research conducted during the action has increased our understanding of light-matter interaction in the strong coupling limit in many-body systems, quantum phase transitions generated by light, novel detection methods for mesoscopic systems, and topological properties of matter. The results of the project have an impact on the field of light-control of material properties and on further development of quantum technologies in general.
The research conducted during the action has increased our understanding of light-matter interaction in the strong coupling limit in many-body systems, quantum phase transitions generated by light, novel detection methods for mesoscopic systems, and topological properties of matter. The results of the project have an impact on the field of light-control of material properties and on further development of quantum technologies in general.