Condensate formation in a dark state

4 May 2023

Photo: AG Hemmerich

The scientists used an experimental platform consisting of an ultracold quantum gas in an optical high-finesse cavity, pumped by a periodically shaken standing light wave

In a research work recently published on the cover of Physical Review Letters, scientists from the department of physics at Universität Hamburg showed that the dark state concept, originally developed in quantum optics, provides a general approach to efficiently prepare complex many-body states in an open quantum system.

The concept of dark states was originally developed in quantum optics. It involves superpositions of matter states with relative phases, so that the quantum mechanical amplitudes coupling the different sectors to an irradiated light field interfere destructively.

While uncontrolled dissipation often has a destructive impact on a quantum system, with appropriate control it can also be utilized to engineer nontrivial states, often in conjunction with driving a system out of equilibrium. A prominent experimental platform for this purpose is that of ultracold quantum gases coupled to high-finesse optical cavities, such that the photon loss of the cavity provides a well-controlled dissipative channel.

The condensate in the dark state remains unaffected

The researchers now demonstrated a robust condensate formation in a dark state. They used an experimental platform consisting of an ultracold quantum gas in an optical high-finesse cavity, pumped by a periodically shaken standing light wave. In a specific parameter regime, they observed a stationary excited dark state condensate, for which scattering of pump photons into the cavity mode is suppressed.

The scientists, who conduct both theoretical and experimental research in the Cluster of Excellence "CUI: Advanced Imaging of Matter", found that the atomic condensate in the dark state remains essentially unaffected, when the pump light is switched off, while, if the system is prepared in a bright state, it undergoes a dynamic phase transition back into the normal condensate phase.

Citation

Jim Skulte, Phatthamon Kongkhambut, Sahana Rao, Ludwig Mathey, Hans Keßler, Andreas Hemmerich, and Jayson G. Cosme

"Condensate Formation in a Dark State of a Driven Atom-Cavity System"

Phys. Rev. Lett. 130, 163603 (2023)

DOI: 10.1103/PhysRevLett.130.163603