SPICE Workshop on Quantum Spinoptics, June 13th - 15th 2023
Tobias Donner
The time evolution of a quantum system can be strongly affected by dissipation. Although this mainly implies that the system relaxes to a steady state, in some cases it can lead to the appearance of new phases and trigger emergent dynamics. In our experiment, we study a Bose-Einstein Condensate dispersively coupled to a high finesse resonator. The cavity mode is populated via scattering off the atoms, such that the sum of the coupling field and the intracavity standing wave act as optical lattice potential. When the dissipative and the coherent timescales are comparable, we find a regime of persistent oscillations where the cavity field does not reach a steady state. In this regime the atoms experience an optical lattice that periodically deforms itself, without an external time dependent drive, leading to a pumping mechanism.
SPICE Workshop on Quantum Spinoptics, June 13th - 15th 2023
Antoine Browaeys
This talk will present our recent work on the realization of the Driven Dicke model using an elongated cloud of cold atoms in free space (arXiv:2207.10361). This model considers the collective spin of an ensemble of 2 level-atoms coupled to a single mode of the electromagnetic field and driven by a classical light. We observe experimentally the non-equilibrium phase transition predicted by the model, featuring a super-radiant phase at strong intensity of the driving laser and a phase characterized by a collective dipole at weak driving. We also measure the statistics of the emitted light and find that it has the properties predicted for a super-radiant laser.
SPICE Workshop on Quantum Spinoptics, June 13th - 15th 2023
Claudiu Genes
Cooperative effects in complex, coupled quantum systems, cannot be understood by sole consideration of the individual constituents, as they arise from the interplay among them. Light-matter platforms provide an optimal playground for the observation and exploitation of quantum cooperative effects [1]. For example, structured subwavelength arrays of quantum emitters trapped in optical lattices, are ideal showcases of such cooperative behavior, as their optical response can be efficiently enhanced by controlling the hopping of surface excitations via the quantum electromagnetic vacuum induced dipole-dipole interactions.
While subwavelength separations are not easily achieved in standard quantum optics setups, molecular dimers and molecular aggregates (i.e.~arrays of identical molecules, such as J- and H-Aggregates) can feature deeply subwavelength separations on the nanometer scale. The downside of such systems is the much more complex structure, which introduces coupling of electronic degrees of freedom with intra- and inter-molecular vibrations. We have introduced a quantum Langevin equations approach to electron-vibron interactions for single molecules subject to either classical or cavity quantum light fields. The extension of this method to more than one particle allowed us to benchmark the scaling of cooperative effects such as super- and subrradiance to molecular rings or chains and to quantify the effect of vibrations onto the operation of such systems as nanoscale coherent light sources [3].
[1] M. Reitz, C. Sommer, and C. Genes, Cooperative Quantum Phenomena in Light-Matter Platforms, PRX Quantum 3, 010201 (2022)
[2] M. Reitz, C. Sommer and C. Genes, Langevin approach to quantum optics with molecules, Phys. Rev. Lett. 122, 203602 (2019)
[3] R. Holzinger, S. Oh, M. Reitz, H. Ritsch and C. Genes, Cooperative subwavelength molecular quantum emitter arrays, Phys. Rev. Research 4, 033116 (2022)
