Mie Resonant Dielectric Metastructure Based Optical Circuits Integrated with Quantum Dot Single Photon Source for on-Chip Scalable Quantum Information Processing

Abstract

Realization of on-chip scalable optical quantum information processing (QIP) systems requires optical circuits built around arrays of single photon sources (SPSs) to manipulate the emitted photons and enable interference between photons from distinct SPSs resulting in entanglement. Towards such a goal we have reported a new class of on-chip single quantum dot arrays - grown on lithographically fabricated mesas designed to exploit the attendant surface stress gradient driven adatom migration during MBE growth thus termed mesa-top single quantum dots (MTSQDs) [1]. These MTSQDs, we have demonstrated, are ~99% pure SPSs [2] that are readily integrable with on-chip light manipulating units (LMUs) that provide the needed multiple functions of enhancing the emission rate of the SPS and the directionality of the photon emission in the horizontal direction, on-chip propagation, splitting and recombining to enable on-chip interference towards entanglement. So far attempts towards creating such LMUs (mostly resonant cavity and waveguide) have been based on photonic crystal membrane structures and exploit departure from Bragg scattering to provide localized photon modes for individual cavity or waveguides thus facing the challenge of strict mode-matching between these components. In contrast, in this talk we present an approach to realizing all the required light manipulating functions based on metastructures made of subwavelength size dielectric building blocks (DBBs) where a common collective Mie resonance of the interacting DBBs is exploited to provide all the needed light manipulating functions simultaneously [3, 4, 5]. These Mie resonances are fundamentally different from Bragg scattering as they are typically broad in spectrum, with a typical Q~100- that alleviates the strict requirements of spectral and spatial matching between the network components and with the SPS emission mode. Moreover, Mie resonances are less sensitive to effect of fabrication disorders that introduce aperiodicity in the array. Furthermore, the spectral broad nature of the Mie resonances allows controlled interference between the electric and magnetic modes resulting in directionality of photon emission and propagation without strong field localization—an effect that is unique to this class of LMUs. Importantly, providing all the needed light manipulating functions using the same collective Mie mode circumvents issue of mode mismatch between the components of the optical circuit including the SPS, and thus allows design and realization of large-scale circuits. Aimed at the above noted objective of on-chip nanophotonic systems, in this talk we will present finite element method (FEM)-based design and simulation of the response of an MTSQD-DBB integrated optical circuit that exploits the dominant collective magnetic and electric dipole mode to provide the MTSQD emission rate enhancement (Purcell effect) ~5 as well as emission directionality (the nanoantenna effect), lossless on-chip propagation, beam-splitting, and beam-combining [4, 5]. We show that such structures enable on-chip interference of photons resulting in path entanglement between the two MTSQD SPSs at large distances. Finally, we will present FEM simulations of direct coupling of two SPSs via an intermediate lossless collective Mie mode over on-chip distances much longer than the wavelength. We show that such coupling can result in a super-radiant state involving on-chip SPSs at a distance resulting in a ~2 fold enhanced decay rate [5]. This emergent super-radiant state in such SPS-SPS coupled system is maximally entangled, and thus may act as a potential resource for on chip QIP. [1] J. Zhang et.al, J.Appl.Phys.120,243103(2016) [2] J.Zhang et. al, App. Phys. Lett. 114, 071102(2019) [3] S. Chattaraj, J. Opt. Soc. Am. B. 33, 12(2016) [4] S. Chattaraj et.al, arXiv1811.06652v1(2018) [5] S. Chattaraj et.al, IEEE J. Quant. Electron. 2019, Accepted for Publication This work is funded by ARO W911NF-15-1-0025