Engineering Quantum Sensors Exploiting Rabi Splitting in Plexcitonic Nanoparticle Assemblies

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Demonstrated quantum technologies based on single atomic emitters coupled to resonant cavities require cryogenic temperatures and exhibit fragile light-matter coupling. Plexcitonic resonators based on strong plasmon-exciton coupling exhibit a large Rabi splitting at room temperature in the solid-state indicative of strong coupling. Preliminary results indicate that the Rabi splitting in a plexcitonic system consisting of organic J-aggregates coupled to gold nanoislands is highly sensitive to ambient humidity. Although metals have Ohmic losses, the plasmonic local field enhancement compensates for these losses and enables strong coupling. Consequently, the sensing action observed by us is robust and reproducible. This motivated us to further improve and optimize the quantum plexcitonic sensor through extending the decoherence timescales by reducing energy dissipation. Another step in this direction involves forming plasmonic molecules (dimers and trimers) from Ag/Au nanocubes and nanoprisms through control of the inter-particle spacing during nanofabrication. Such plasmonic molecules are expected to exhibit a dramatic local field enhancement, which aids sensitivity and facilitates strong coupling. This project also aims to measure the subradiance/superradiance behavior of plexcitonic resonators through steady-state and time-resolved photoluminescence spectroscopy and imaging. This is a collaborative project involving the Shankar Group in Semiconductor Nanomaterials & Devices at the University of Alberta in Edmonton, Canada and the Shouvik Datta Group in Quantum Optoelectronic Devices at IISER-Pune, India. This project will leverage the Datta Group's expertise in measuring spatio-temporal coherence of emitted photons to achieve a deeper understanding of the plexcitonic quantum system. Plexcitons will provide a new avenue to create and manipulate entangled states close to room temperature, with the resulting Rabi splitting easily tunable by electrical, thermal, chemical or optical stimuli. This project aims to address the critical need for non-cryogenic photonic quantum technologies.