Quantum Nanoplasmonic Coherent Perfect Absorption

Nanoplasmonics offers the unique ability to confine light to extremely sub-wavelength volumes and strongly enhance local optical fields via resonant surface plasmon modes, thereby constituting exceptional architectures for enhanced light-matter interaction and the exploration of extreme nano-optics for quantum dynamics. In particular, room-temperature strong coupling using single molecules and colloidal quantum dots in nanoplasmonic environments has been realized using ultrathin (∼1 nm) nanoplasmonic cavities [1] and scanning probe tips [2]. While ultrafast plasmonic near-field evolution can be exploited to achieve high-speed quantum operations [3], including dynamic bi [4]- and tripartite [5] entanglement in quantum dots, it is in the light of fast-decaying cavity plasmon modes vital to explore pathways for improving the temporal robustness of strongly coupled plasmon-emitter states under ambient conditions, with the aim of realizing truly room-temperature-viable quantum nanophotonic devices.<br/><br/>Here, a novel strategy for selective preparation and, conceivably, ‘immortalization’ of selected plasmon-exciton polariton states by means of quantum nanoplasmonic coherent perfect absorption (qnCPA) is discussed. It is shown that under plasmonic nanowire-waveguide driving, the qnCPA regime can selectively lock a nanocavity-emitter system in either the upper or lower plasmon-emitter polariton. Furthermore, in this regime, the intrinsic losses of the nanocavity-emitter device can be precisely compensated for by means of the coherent and non-perturbing waveguide feeding at a suitable rate, effectively paving the way towards strongly coupled light-matter states that are robust against decoherence at room temperature. This contrasts sharply with the conventional belief that preserving an individual quantum state requires cryogenic cooling and strict isolation of the system from environmental influence. In fact, here, dynamic dissipation under ambient conditions is fully embraced, strategically harnessing its interplay with plasmon interference in a specific dressed state to establish the qnCPA regime itself. As a novel paradigm for quantum state preparation and preservation in plasmonic cavity quantum electrodynamics, qnCPA offers exciting prospects for room-temperature-viable quantum nanophotonic technologies.<br/><br/><b>ACKNOWLEDGEMENTS</b><br/>Supported by the Science Foundation Ireland (SFI) via grants 18/RP/6236 and 22/QERA/3821.<br/><br/><b>REFERENCES</b><br/>[1] R. Chikkaraddy, B. de Nijs, F. Benz, S. J. Barrow, O. A. Scherman, E. Rosta, A. Demetriadou, P. Fox, O. Hess, and J. J. Baumberg, <i>Single-Molecule Strong Coupling at Room Temperature in Plasmonic Nanocavities</i>, Nature <b>535</b>, 127 (2016).<br/>[2] H. Groß, J. M. Hamm, T. Tufarelli, O. Hess, and B. Hecht, <i>Near-Field Strong Coupling of Single Quantum Dots</i>, Science Advances <b>4</b>, eaar4906 (2018).<br/>[3] X. Xiong, N. Kongsuwan, Y. Lai, C. E. Png, L. Wu, and O. Hess, <i>Room-Temperature Plexcitonic Strong Coupling: Ultrafast Dynamics for Quantum Applications</i>, Appl. Phys. Lett. <b>118</b>, 130501 (2021).<br/>[4] F. Bello, N. Kongsuwan, J. F. Donegan, and O. Hess, <i>Controlled Cavity-Free, Single-Photon Emission and Bipartite Entanglement of Near-Field-Excited Quantum Emitters</i>, Nano Lett. <b>20</b>, 5830 (2020).<br/>[5] F. D. Bello, N. Kongsuwan, and O. Hess, <i>Near-Field Generation and Control of Ultrafast, Multipartite Entanglement for Quantum Nanoplasmonic Networks</i>, Nano Lett. <b>22</b>, 2801 (2022).