Exploiting collective dynamics of quantum emitters ensembles

ExceedQ is an interdisciplinary project that makes use of quantum optics tools applied to design, enhance and exploit light-matter interactions in quantum systems ranging in size from the micro- scale (atoms, molecules) to the macro-scale [solid-state based mechanical resonators (MRs)]. The main vision of the project is to provide novel ideas for basic science and applications that exploit collective dynamics in order to outperform applications designed for single element systems. The light-matter interactions under consideration are loosely grouped according to their basic physical mechanism: i) near-resonant optical driving of systems with sharp transitions, i.e. quantum emitters (QEs) and ii) optomechanical (OM) interactions based on the radiation pressure effect exerted by photons onto solid-state based MRs. The proposal is structured around 4 aims where the main benefit arises from the exploration of collective coherent as well as incoherent dynamics in ensembles of QEs. This topic is predominant within the first 3 aims and present as well in the last aim where current OM photon-phonon interaction mechanisms are challenged by the consideration of an alternative indirect QE-mediated light-motion coupling mechanism. Within the first 3 aims, ensembles of QEs are explored towards goals such as quantum metrology, transport and many-body physics. The coupling of emitters can occur either dispersively as well as via common dissipative reservoirs. Strategies are developed that lead to innovations of the standard Ramsey interferometry and Rabi spectroscopy techniques for frequency estimation based on collective decaying and dephasing processes (aim 1). Collective dispersive interactions are used to design symmetry and energy-resolving excitation schemes for the generation of many-particle quantum correlated states (aim 1). The dispersive particle-particles interaction constitute the starting point of investigations of quantum transport in emitter chains where the collective behaviour is introduced via a mediating cavity field. The upshot is that both exciton and charge transport are predicted to increase in quantum vacuum embedded materials (aim 2) hinting towards novel quantum chemistry applications. Atom-atom interactions of tailorable strength provide a testbed for investigations proposed in aim 3 where the nature of many particle interactions in dense ultracold Rydberg gases is explored via time-domain interferometry with attosecond precision. Finally, aim 4 builds on the progress made by the applicant in the direction of multi-element OM and hybrid OM by proposing a change of paradigm from direct photon-phonon to QE-mediated interactions that exploit both collective interactions as well as collective dissipative processes. The success of ExceedQ will lead to significant contributions in a variety of research fields such as: i) quantum metrology (improvements in the precision of atomic clocks), ii) quantum memories (by preparing states showing strong multi-particle quantum correlations), iii) quantum transport (by the exploration of the strong light-matter coupling regime to show enhanced exciton and charge transport properties), iv) strongly-coupled systems (developing theories for the ultra-fast time domain experimental investigations of Rydberg gases) and finally v) quantum optomechanics (by providing alternative paths to traditional Om via the hybrid OM approach).

A detailed and deep understanding of the coupled dynamics of light and material objects is the physical basis of a great deal of modern technical devices almost all areas. With growing miniaturization of these devices quantum descriptions become a growing focus of the future developments. In this project we study the properties and dynamics f minimalistic model systems composed of quantum dipole emitters and light modes illuminated by laser fields in great detail. Here we use analytical descriptions as well numerical methods to gain a microscopic, detailed understanding of the ongoing physics. At the heart of our investigations is the collectivs absorption, reemission and scattering of singles photons in nanoscopic arrays of two-level quantum emitters. Our results allow a better understanding of the precision obtained in optical atomic clocks, optical data transmission and storage or the possibilities to build light sources as lasers with nanosopic dimensions. The numerical methods and software developed within the project is now publicly available in open source form and also wide used in the current quantum flagship initiative of the EU.