Experise: Quantum optics, condensed matter physics, quantum control
Research directions: Floquet theory, Polaritons, Spectroscopy, Quantum sensing
Languages: German (native), English (native-like), Chinese (fluent)
Scientific Genealogy: Tobias Brandes (1994); Bernhard Kramer (1967); Otfried Madelung (1950);
Werner Heisenberg (1923); Arnold Sommerfeld (1891); Carl Lindemann (1873); Christian Felix Klein (1868); Julius Pluecker (1823);
Christian Ludwig Gerling (1812); Carl Friedrich Gauss (1799).
2024-now:Researcher, Shenzhen International Quantum Academy (SIQA)
2021-2024:Associate Researcher, Shenzhen Institute of Quantum Science and Engineering (SUSTech)
2017-2021: Postdoc, Beijing Computational Science Research Center. Supervisor: Jianshu Cao (MIT)
2017: PhD, TU Berlin, Supervisor: Tobias Brandes
2013: Master of Science, TU Berlin, Supervisor: Tobias Brandes
2012: Bachelor of Science, TU Berlin, Supervisor: Tobias Brandes
Motivation and achievements
My research investigates principles of light-matter interaction
in the quantum optical and semiclassical regimes. In this context, I develope protocols for
quantum control and quantum sensing. Besides others, my research has contributed to the
understanding of the exciton-polariton dynamics and the quantum control of Floquet systems.
Honors and Awards
2025:National Natural Science Foundation of China, International (Regional) Cooperation and Exchange Project, Research Fund for International Excellent Young Scientists
2020:National Natural Science Foundation of China, International (Regional) Cooperation and Exchange Project, Research Fund for International Young Scientists
2018:International Postdoctoral Fellowship Program 2018 (Talent-Introduction Program)
2018:First-Class Grant from the 64th Batch of General Funding by the China Postdoctoral Science Foundation
2014:Physics Studies Award: Physik-Studienpreis der Physikalischen Gesellschaft zu Berlin
Research highlights
Photon-resolved Floquet theory approach to spectroscopic quantum sensing
Georg Engelhardt, Konstantin Dorfman, and Zhedong Zhang
Spectroscopic quantum sensing uses the quantized nature of matter to develop metrological methods beyond classical means. For instance, electric-field sensing using Rydberg atoms
and optical magnetometry are currently already highly-sensitivity techniques deployed in the tedious search for the elusive dark matter. Yet, the lack of suitable theoretical
methods to predict photonic measurement statistics beyond the mean value inhibits the improvement of such spectroscopic quantum sensing devices.
A new theoretical framework combining the celebrated Floquet theory and full-counting statistics, which is dubbed Photon-resolved Floquet theory, now offers assistance
in the quest for better spectroscopic sensing protocols. Relying only on semiclassical simulations of the light-matter interaction, it constitutes a flexible tool to optimize
existing experimental setups and the development of new measurement protocols. Besides others, it explains a diverging measurement noise in the weak dissipation regime as a
generic consequence of the quantized nature of quantum matter. Intriguingly, the Photon-resolved Floquet theory predicts that electric field sensing with Rydberg atoms might
be improved by several orders of magnitude by measuring the laser phase instead of its intensity. Similarly, the framework can unlock the full potential of other spectroscopic
quantum sensing protocols.
Photon-resolved Floquet theory: Full-Counting statistics of the driving field in Floquet systems
Georg Engelhardt, JunYan Luo, Victor M. Bastidas, Gloria Platero
Floquet theory and other semiclassical approaches are very successful in describing quantum matter which is subject
to external driving fields. While accurately predicting the state of the driven quantum system, Floquet theory per se is
not concerned with the state of the photonic driving field. Full-counting statistics (FCS) has become a well-established
method in electron transport through semiconductor nanostructures to predict the statistics of electrons having tunneled
between distinct electron reservoirs. Similarly to the FCS in electronic systems, the photon-resolved Floquet theory (PRFT)
introduces counting fields into the semiclassical equation of motion of the driven quantum system, which tracks the photon
exchange with distinct coherent photonic driving fields [1,2]. This approach enables a numerical efficent and accurate way
to calculate the joint light-matter dynamics.
Besides others, the PRFT predicts an intriguing light-matter entanglement effect, in which the state of the light field is
steered by the Floquet states, generalizations of eigenstates in time-independent system to the peridically-driven case [1].
This entangled light-matter state theoretically enables a highly efficent quantum communication protocol, which uses coherent light fields
instead of few-photon protocol. The light-matter entanglement can survive even in the presence of dissipation, as investigates in the PRFT
framework extension for open quantum systems [3].
Polariton Localization and Dispersion Properties of Disordered Quantum Emitters in Multimode Microcavities
Georg Engelhardt and Jianshu Cao
Experiments have demonstrated that the strong light-matter coupling in polaritonic microcavities
significantly enhances transport. Motivated by these experiments, we have solved the disordered
multimode Tavis-Cummings model in the thermodynamic limit and used this solution to analyze its
dispersion and localization properties. The solution implies that wave-vector-resolved spectroscopic
quantities can be described by single-mode models, but spatially resolved quantities require the
multimode solution. Nondiagonal elements of the Green’s function decay exponentially with distance,
which defines the coherence length. The coherent length is strongly correlated with the photon weight and
exhibits inverse scaling with respect to the Rabi frequency and an unusual dependence on disorder. For
energies away from the average molecular energy and above the confinement energy, the
coherence length rapidly diverges such that it exceeds the photon resonance wavelength λ. The rapid
divergence allows us to differentiate the localized and delocalized regimes and identify the transition from
diffusive to ballistic transport.
