A dissipative quantum gas of light

Our textbook understanding of quantum systems tends to come from modeling these systems isolated from the environment. However, an emerging focus is understanding how many-body quantum systems behave when interacting with their surroundings and how they subsequently become dissipative, or non-Hermitian, systems. Öztürk et al. formed a quantum condensate of light by trapping photons in an optical cavity, a system that is naturally dissipative. By altering the trapping conditions, they demonstrated that the system provides a powerful platform with which to explore the complex dynamics and phase transitions occurring in dissipative quantum systems.
Science, this issue p. 88


Quantum gases of light, such as photon or polariton condensates in optical microcavities, are collective quantum systems enabling a tailoring of dissipation from, for example, cavity loss. This characteristic makes them a tool to study dissipative phases, an emerging subject in quantum many-body physics. We experimentally demonstrate a non-Hermitian phase transition of a photon Bose-Einstein condensate to a dissipative phase characterized by a biexponential decay of the condensate’s second-order coherence. The phase transition occurs because of the emergence of an exceptional point in the quantum gas. Although Bose-Einstein condensation is usually connected to lasing by a smooth crossover, the observed phase transition separates the biexponential phase from both lasing and an intermediate, oscillatory condensate regime. Our approach can be used to study a wide class of dissipative quantum phases in topological or lattice systems.

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Materials and Methods
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References (3041)


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References and Notes

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Published In

Volume 372 | Issue 6537
2 April 2021

Submission history

Received: 26 September 2020
Accepted: 23 February 2021
Published in print: 2 April 2021


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We thank S. Diehl, M. Scully, and H. Stoof for discussions. Funding: We acknowledge support by the DFG, under SFB/TR 185 (277625399) and the Cluster of Excellence ML4Q (EXC 2004/1–390534769); the EU, under the Quantum Flagship project PhoQuS; and the DLR, with funds provided by the BMWi (50WM1859). J.S. thanks the University of Cambridge for support during the early stages of this work, and M.W. thanks the CAIQuE for providing a guest stay at UC Berkeley. Author contributions: F.E.Ö., T.L., J.S., and F.V. analyzed the data. J.S., J.Kl., and M.W. conceived of and designed the experiments. F.E.Ö., T.L., and J.Kr. contributed materials and/or analysis tools. F.E.Ö. and G.H. performed the experiments. F.E.Ö., T.L., J.S., F.V., J.Kr., and M.W. wrote the paper. Competing interests: The authors declare that they have no competing interests. Data and materials availability: Data shown in the figures are available in the Zenodo database (29).



Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
Tim Lappe
Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany.
Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
Jan Klaers
Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
Present address: Complex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, Drienerlolaan 5, 7522 NB Enschede, Netherlands.
Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany.
Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.

Funding Information

Cluster of Excellence ML4Q: EXC 2004/1
Cluster of Excellence ML4Q: 390534769


Corresponding author. Email: [email protected] (J.S.); [email protected] (M.W.)

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  1. Phasen eines Bose‐Einstein‐Kondensats aus Licht, Physik in unserer Zeit, 52, 4, (162-163), (2021).

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