Quantum Photonics

Research on photonics processes and photonics materials and systems, as well in general about light-matter interaction, naturally brings with it a strong expertise in various quantum aspects such as point defects and quantum dots, atoms, single photon emission and single-photon counting, as well as the quantum properties of different material systems.

Theoretical and Computational Analysis

Lisa Fredin’s lab builds computational models for experimental materials, including defects, surfaces, and disorder, using quantum mechanics and other electronic structure theories to develop a better understanding of structure-property relationships for complex materials. In addition to organic molecules and materials, this work encompasses also inorganic metal oxide materials and nanocrystals, building bridges between physical chemistry, material science, nanoscience, and computation.

Chinedu Ekuma’s group uses cutting-edge data-driven materials informatics and machine learning techniques that are revolutionizing the design and prediction of the next generation of quantum materials. A special focus is on uncovering emerging properties such as excitonic and topological physics, as well as the interplay of defects and many-body interactions in strongly correlated materials. Innovative approaches to the exploration of vast material spaces enable the rapid identification of materials with the most desirable properties for a range of applications, including quantum information processing and sensing. This research leverages a variety of tools, especially density functional theory, Green’s function-based approaches, material-specific parameterized effective Hamiltonians, and dynamical mean-field approximation-based techniques, including the typical medium dynamical cluster approximation, pioneered in-house. 

Prof. Bitan Roy is an expert in quantum field theory. His group’s activities go from using field theoretical and numerical techniques for the study of interparticle interactions in quantum solid state systems, to the exploration of the signatures of impurities on transport and thermodynamic properties of quantum materials. The quantum systems studied in his group include strongly coupled quantum phases, such as magnetism, superconductivity, non-Fermi liquids, and the non-trivial geometric structures developed by quantum-mechanical wavefunctions in condensed-matter systems that are related to the topological classification of quantum crystals.

Ultracold Atoms and Quantum Processors

Prof. Sommer’s lab has the ability to study Quantum many-body physics by using specially prepared ultracold atoms. One current activity is the investigation of transport and non-equilibrium interfaces in strongly interacting atomic Fermi gases. The experimental determination of transport properties of atomic Fermi gases with strong and well-characterized interactions provides important quantitative, experimental tests of many-body theories.

Investigation of Quantum Systems

The interaction between photons and the quantum states of matter is the fundamental process that enables a multitude of key phenomena, like photosynthesis, the color of many jewels, optical telecommunication, or quantum cryptography and is also a key effect that allows us to study the behavior and properties of quantum systems ranging from atoms to larger organic molecules, to quantum dots, or the states of atoms embedded in host materials, or in general point defects in crystals or atomic layers.

Prof. Biaggio in the Physics department is studying the excitonic states that are created by photon absorption in organic molecular crystals and organic semiconductors. In such materials photon absorption results in a tightly bound exciton with a total spin of 0 which, when the conditions are right, can decay into two neighboring excitons that have each a spin of 1 but are then entangled into having an overall spin of 0, and maintain this entanglement while they diffuse independently in the crystal. Such processes are useful because they can provide two excitons for the prize of one photon in future photovoltaic systems that use such organic semiconductors, but are also interesting from a fundamental quantum point of view, because the entanglement of the two excitons is detectable as quantum beats when those excitons meet again, and can be used to study the onset of decoherence of the quantum states. In addition the entangled exciton pair is interesting as a solid-state equivalent of the entangled photon pairs uses, e.g., for quantum-encrypted communication.

Also in the Physics Department, Prof. Stavola’s group uses infrared spectroscopy to determine the structure of defects and impurties in semiconductors and transparent conducting oxides. Also active in the investigation of point-defects and dopants in semiconductors and other material is Prof. Dierolf. Prof. Dierolf’s group is studying the behavior of dopants and point defects in various materials, in particular rare-earth atoms in wide-bandgap semiconductors that can lead to light-emitting diodes with tunable emission spectra. The main tool used for these activities is excitation-emission spectroscopy, a technique that delivers a map of the energy of the various possible quantum transition in a system.

Prof. Elizabeth Young’s lab in the Chemistry Department uses pump & probe transient absorption spectroscopy and time-resolved fluorescence dynamics to study  photophysics and photochemistry on the femto-to-microsecond time scales. In particular, Prof. Young and her group are interested in the mechanisms of energy flow and photo-induced charge transfer that are important in many energy storing chemical reactions, photovoltaic systems, and biology. Her group probes both molecular and materials systems. In semincondutor materials, Prof Young is working to contribute fundamental knowledge of photoactive materials and molecular-level mechanisms by providing a molecular-level understanding of how applied potential (in situ) and applied potential plus steady-state illumination (operando) conditions impact the photophysical mechanisms (i.e. charge carrier dynamics, charge separation, charge recombination, charge trapping and charge collection) within and between stacks materials.