2026-10-05 - 2026-10-09
Hier geht es zur AnmeldungJulian Schmitt
Heidelberg University
Can light be trapped, brought to thermal equilibrium, and undergo condensation? Einstein introduced the photon box as a thought experiment to probe the foundations of quantum mechanics. Today, optical microcavities allow us to build photon boxes in the laboratory to explore the thermodynamics and many-body physics of light. By confining photons in microcavities, they acquire an effective mass and thermalise through interactions with matter, transforming light into a quantum many-body system at the interface of quantum optics, statistical mechanics, and condensed matter physics.
This lecture course provides an introduction to the physics of photon gases and the remarkable phenomena they enable. We begin by developing the foundations of photon thermalisation, Bose–Einstein condensation, coherence, and thermodynamics, highlighting parallels and differences to ultracold atomic gases. We then introduce the theoretical framework for driven-dissipative cavity systems, including master equations, effective open-system descriptions, rate equations, and non-Hermitian physics. Building on these concepts, we explore the statistical physics of photon condensates, covering statistical ensembles, fluctuations, photon-number statistics, correlations, and critical phenomena. Next, we discuss how microstructures realise trapping potentials from harmonic and box geometries to double wells and lattice systems, opening the door to studies of low-dimensional physics, nonlinear dynamics, and phase transitions. Finally, we show how photon gases provide a versatile simulation platform for topological lattice models, edge states, and non-Hermitian topological phases.
