Quantum Nanoplasmonic Networks at Ambient Temperature

Quantum technologies are widely expected to bring a revolution in communications and information technologies in the coming decade allowing, for example, un-paralleled levels of secure communications. For quantum communication, photonic quantum effects have played a central role, but most photonic solutions and systems based on light-matter interaction also require cryogenic environments. Strong coupling of light and matter at the single emitter level is a fundamental quantum resource offering deterministic energy exchange between single photons and a two-level system, and the possibility to achieve single-photon nonlinearities via the anharmonicity of the Jaynes-Cummings ladder. Until recently, however, the conditions for achieving strong light-matter coupling were most commonly met at cryogenic temperatures such that de-coherence processes are suppressed. As a major step forward, we have recently demonstrated room-temperature strong coupling of single molecules [1] and single quantum dots [2] to ultra-confined light fields in plasmonic resonators at ambient conditions. The fact that strong-coupling conditions may be reached at room temperature is of immense interest because it represents a clear route to a practical implementation and use of quantum behaviour in nanophotonic systems and its application in bio-sensing [3].<br/><br/>The talk will discuss how nanoplasmonics can be an enabler of ultrafast quantum nanophotonic networks via strong coupling and ultrafast quantum dynamics [4]. We will highlight the physics associated with recently demonstrated room-temperature strong coupling of single molecules in a plasmonic nano-cavity [1] and near-field generated strong coupling of single quantum dots [2] and single quantum emitter Dicke enhancement [5] paving the road towards single-photon quantum nonlinearities. The presentation will also explain near-field enhanced single-photon emission in near-zero index materials [6] and ultrafast multi-partite quantum entanglement [7]. This provides the foundation for unprecedented control over photon number, single photon dynamics, and dynamic multi-photon coherence. These properties are all imperative for the development of next-generation, nanoscale building blocks in ambient-temperature quantum communication 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] N. Kongsuwan, X. Xiong, P. Bai, J.-B. You, C. E. Png, L. Wu, and O. Hess, <i>Quantum Plasmonic Immunoassay Sensing</i>, Nano Lett. <b>19</b>, 5853 (2019).<br/>[4] 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/>[5] T. Tufarelli, D. Friedrich, H. Groß, J. Hamm, O. Hess, and B. Hecht, <i>Single Quantum Emitter Dicke Enhancement</i>, Phys. Rev. Research <b>3</b>, 033103 (2021).<br/>[6] 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/>[7] 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).