A vanishing quantum gas of light
Our understanding of quantum systems in the textbook usually comes from modeling these systems isolated from the environment. An emerging focus, however, is to understand how many quantum systems with many bodies behave when dealing with their environment and how they then become dissipative or non-Hermetic systems. Öztürk et al. a quantum condensate of light formed by capturing photons in an optical cavity, a system that is naturally dissipative. By changing the capture conditions, they have shown that the system provides a powerful platform to explore the complex dynamics and phase transitions that occur in dissipative quantum systems.
Science, this issue p. 88
Abstract
Quantum gases of light, such as photon or polariton condensates in optical microcavities, are collective quantum systems that allow the scattering of, for example, cavity loss. This property makes them an instrument for studying dissipative phases, an emerging topic in quantum multi-body physics. We experimentally demonstrate a non-Hermetic phase transition from a photon Bose-Einstein condensate to a dissipative phase characterized by a two-coupled decay of the coherence of the second order of the condensate. The phase transition occurs due to the emergence of an exceptional point in the quantum gas. Although Bose-Einstein condensation is usually associated with load by a smooth crossing, the observed phase transition separates the two-coupled phase from both load and an intermediate, oscillating condensate regime. Our approach can be used to study a wide range of dissipative quantum phases in topological or lattice systems.