Deterministic coupling of site-controlled quantum emitters in monolayer semiconductors to plasmonic nanocavities (1804.06541v1)

Abstract: Solid-state single-quantum emitters are a crucial resource for on-chip photonic quantum technologies and require efficient cavity-emitter coupling to realize quantum networks beyond the single-node level. Previous approaches to enhance light-matter interactions rely on forming nanocavities around randomly located quantum dots or color centers but lack spatial control of the quantum emitter itself that is required for scaling. Here we demonstrate a deterministic approach to achieve Purcell-enhancement at lithographically defined locations using the sharp corner of a metal nanocube for both electric field enhancement and to deform a two-dimensional material. For a 3 by 4 array of strain-induced exciton quantum emitters formed into monolayer WSe2 we show spontaneous emission rate enhancement with Purcell-factors (FP) up to FP=1050 (average FP=272), single-photon purification, and cavity-enhanced quantum yields increasing from initially 1 % to 15 %. The utility of our nanoplasmonic platform is applicable to other 2D material, including boron nitride, opening new inroads in quantum photonics.

• The paper presents a novel method for coupling site-controlled quantum emitters using strain-induced localization in monolayer semiconductors.
• The approach achieves high Purcell enhancement with factors up to 1050 and boosts quantum yield from 1% to 15% for improved photon emission.
• This deterministic assembly technique paves the way for scalable on-chip quantum networks and integrated photonic circuits.

Deterministic Coupling of Site-Controlled Quantum Emitters in Monolayer Semiconductors to Plasmonic Nanocavities

The paper presented in this paper offers a thorough investigation into the deterministic coupling of strain-induced quantum emitters, specifically within the field of monolayer semiconductors like tungsten diselenide (WSe₂), to plasmonic nanocavities. It addresses fundamental challenges in the field of solid-state quantum photonics, primarily focusing on the spatial control and coupling efficiency necessary for scalable quantum networking. The methodology involves a precise approach to establish site-controlled exciton quantum emitters directly at designated hotspots, defined lithographically, within nanoplasmonic gap-mode cavities.

The central thrust of this research demonstrates significant advancements in achieving high Purcell-enhancement factors for spontaneous emission rates of site-controlled quantum emitters. The approach ensures precise emitter placement and coupling through lithographically defined metal nanocubes, which are capable of deforming two-dimensional materials to produce localized strain-induced quantum emitters. This technique distinctly allows for highly efficient cavity-emitter coupling, ensuring that the quantum emitters are coherently and consistently aligned with the desired cavity modes.

Key numerical achievements include a noteworthy Purcell factor up to 1050, with an average factor reported at 272 across their samples. This substantial enhancement results in significant improvements in single-photon purity as well as quantum yields, which increased from an initial 1% to 15% upon coupling. Such values highlight the effectiveness of the methodology in amplifying light-matter interactions, achieving high photon emission rates, and refining quantum signal purity.

The implications of this paper are far-reaching in the context of photonic quantum technologies. The success of the deterministic assembly technique developed here opens up pathways to more complex, integrated on-chip quantum networks, which require not only precise emitter placement but reliable emitter-mode coupling for photon routing and enhanced quantum yield. Furthermore, the versatility of the approach, applicable beyond WSe₂ to other two-dimensional materials such as boron nitride, can potentially streamline the development of versatile room-temperature quantum emitters.

From a theoretical standpoint, the findings underscore the critical leverage provided by strain-induced quantum emitters and their potential to be harnessed in conjunction with plasmonic structures to overcome previous spatial and coupling limitations. This research is likely to stimulate further inquiry into optimizing the gap-mode resonators and exploring additional material systems that could benefit from similar enhancements.

Speculating on future developments, continued research might focus on improving extraction efficiency and reducing nonradiative recombination in these systems. This could involve exploring finer control over the precise geometric configurations of nanocavities and the strain profiles imposed on the quantum emitters. Additionally, as quantum optical circuits evolve, integration strategies that can incorporate electrical excitation methods, such as electroluminescence in WSe₂, could be pursued to achieve multi-node photonic quantum circuits.

In conclusion, this paper lays a robust foundation for the ongoing evolution of quantum emitter-cavity systems, setting a precedent for future innovations in the field of quantum photonics. The methodologies and results detailed here provide a compelling roadmap for harnessing the full potential of monolayer semiconductors in quantum information science.