Search

A high-quality single-photon source (SPS) is one of the most critical components in photonic quantum information technologies (e.g. QKD, cryptography, linear quantum computing, etc.) where qubits are encoded within individual photons. Moreover, the scalability of these technologies relies heavily on their integration into existing photonic systems, so controlling their quantum properties is crucial. Besides their advantages, current material platforms present limitations due to their complex fabrication procedures and inherent attributes. In the search for reliable SPSs, Transition Metal Dichalcogenides (TMDCs) have emerged as a promising platform. Despite the recency of the field, they have exhibited satisfactory integration potential into photonic cavities, purity close to the state-of-the-art, and the ability to be used in quantum information protocols. The poster presents on-chip quantum emitters from monolayer WSe2 with controlled polarization and high purity, via strain and defect engineering. We explain the drawbacks of current nanopillar designs for strain application, which we use to justify the new proposed geometries. Moreover, we analyze the entire fabrication process from the structure fabrication, the flake exfoliation and transfer, to the defect introduction through electron beam irradiation. Finally, we characterize the samples with different imaging techniques and present the properties of the produced quantum emitters.

Among the other applications is the field of quantum technologies, some layered materials, such as TMDCs and hBN, have been demonstrated to be capable of emitting single photons from localized quantum states. The strong light-matter interaction makes them rather efficient in terms of photon–qubit coupling, and their atomic-scale thickness facilitates a high photonextraction efficiency. Moreover, their stability and easy implementation in photonic and plasmonic integrated devices make them an ideal platform for optics-based, solid-state implementations of QTs. WSe2 is the most studied among the TMDCs as a host for quantum emitters (QE). In particular, the first demonstration and subsequent investigations were conducted on single layered materials. Here we fabricated QEs out of a bilayer two-dimensional WSe2 via deterministic strain and defect engineering. The fabricated TMD QEs exhibit extremely narrow emission lines around 800 nm with a linewidth of around 0.14 nm. Furthermore, they exhibit very good purity of 0.05 and 0.02 under continuous wave (CW) and pulsed excitation, respectively. The narrow emission spectrum of the emitter reveals phonon side bands and zero phonon lines, which allow us to extract relevant information regarding the phonon density of TMD-based quantum emitters. The knowledge about phonon density of states helps designing advanced optical excitation schemes that can be employed to improve efficiency and indistinguishability of the emitters by either involving or decoupling the phonons. Additionally, we also demonstrate the quasi-resonant optical excitation of these emitters, showing that the linewidth almost halves down to 0.08 nm (limited by the resolution of the spectrometer) even though the decay time of the state drastically decreases. We also studied time-resolved emission resonance to study how much charge noise introduces unwanted fluctuation of the resonance which leads to poor indistinguishability.

Photonic quantum information technologies, such as linear optical quantum computing and quantum communications, can be implemented using efficient single-photon sources, detectors, and ordinary linear optical elements to manipulate qubits, which are encoded onto single photons. Scalable quantum computing and communications with millions of qubits require many efficient sources providing indistinguishable and pure single-photon states to obtain entanglement and maximize security without additional protocol complexity. However, this has been proven to be very challenging due to the limitations of both the material platforms and the fabrication complexity. Transition-metal dichalcogenide (TMDC) flakes are among the most recently discovered platforms for quantum information. Still, they have already shown promising results in terms of single-photon emission purity of strained monolayers, deterministic integration of the single-photon emitters in nanophotonic devices, and competitive performance with other single-photon emitters for quantum key distribution. In this poster, we present our advancement toward generating, manipulating, and collecting single-photon states in photonic chips with TMDC devices on silica-on-silicon substrates. First, we justify and support the chosen designs with the results obtained with finite-difference numerical modeling. We then illustrate our nanofabrication process for the development of WSe2 and MoTe2 single-photon emitters, WS2 linear optical components (e.g., waveguides, beam splitters, and interferometers), and photonic crystal nanobeam cavities toward the efficient manipulation of pure and indistinguishable single photons. Finally, we report our preliminary results from the optical characterization experiments carried out so far.