Pristine graphene quantum dots and graphene oxide quantum dots are synthesized by chemical exfoliation from the graphite nanoparticles with high uniformity in terms of shape (circle), size (less than 4 nm), and thickness (monolayer). The origin of the blue and green photoluminescence of GQDs and GOQDs is attributed to intrinsic and extrinsic energy states, respectively.

The goal of integrated quantum photonics is to combine components for the generation, manipulation, and detection of non-classical light in a phase stable and efficient platform. Solid-state quantum emitters have recently reached outstanding performance as single photon sources. In parallel, photonic integrated circuits have been advanced to the point that thousands of components can be controlled on a chip with high efficiency and phase stability. Consequently, researchers are now beginning to combine these leading quantum emitters and photonic integrated circuit platforms to realize the best properties of each technology. In this article, we review recent advances in integrated quantum photonics based on such hybrid systems. Although hybrid integration solves many limitations of individual platforms, it also introduces new challenges that arise from interfacing different materials. We review various issues in solid-state quantum emitters and photonic integrated circuits, the hybrid integration techniques that bridge these two systems, and methods for chip-based manipulation of photons and emitters. Finally, we discuss the remaining challenges and future prospects of on-chip quantum photonics with integrated quantum emitters. PHOTONIC INTEGRATED CIRCUIETS FOR QUANTUM PHOTONICSPICs provide a compact, phase stable, and high-bandwidth platform to transmit, manipulate, and detect light on-chip. By leveraging advances in semiconductor manufacturing for classical communication, PICs have been demonstrated with over a thousand active components in a few square mm [50]. Now, with many foundries offering multi-26. I. Aharonovich, D. Englund, and M. Toth, "Solid-state single-photon emitters," Nat. Photonics 10, 631 (2016) , "Neardeterministic activation of room-temperature quantum emitters in hexagonal boron nitride," Optica 5, 1128-1134 (2018)

Scalable quantum photonic systems require efficient single photon sources coupled to integrated photonic devices. Solid-state quantum emitters can generate single photons with high efficiency, while silicon photonic circuits can manipulate them in an integrated device structure. Combining these two material platforms could, therefore, significantly increase the complexity of integrated quantum photonic devices. Here, we demonstrate hybrid integration of solid-state quantum emitters to a silicon photonic device. We develop a pickand-place technique that can position epitaxially grown InAs/InP quantum dots emitting at telecom wavelengths on a silicon photonic chip deterministically with nanoscale precision.We employ an adiabatic tapering approach to transfer the emission from the quantum dots to the waveguide with high efficiency. We also incorporate an on-chip silicon-photonic beamsplitter to perform a Hanbury-Brown and Twiss measurement. Our approach could enable integration of pre-characterized III-V quantum photonic devices into large-scale photonic structures to enable complex devices composed of many emitters and photons.Photonic quantum information processors use multiple interacting photons to implement quantum computors, 1,2 simulators, 3,4 and networks. [5][6][7][8] These applications require efficient single photon sources coupled to photonic circuits that implement qubit interactions to create highly connected multi-qubit systems. [8][9][10][11] Scalable photonic quantum information processors require methods to integrate single photon sources with compact photonic devices that can combine many optical components. Such integration could enable complex quantum information processors in a compact solid-state material. [12][13][14] Silicon has many advantages as a material for integrated quantum photonic devices. It has a large refractive index that enables many photonic components to fit into a small device size. [15][16][17] Electrical contacts incorporated into the photonic structure can rapidly modulate and reconfigure

Long-distance quantum communication relies on the ability to efficiently generate and prepare single photons at telecom wavelengths. In many applications these photons must also be indistinguishable such that they exhibit interference on a beamsplitter, which implements effective photon-photon interactions. However, deterministic generation of indistinguishable single photons with high brightness remains a challenging problem. We demonstrate two-photon interference at telecom wavelengths using an InAs/InP quantum dot in a nanophotonic cavity. The cavity enhances the quantum dot emission, resulting in a nearly Gaussian transverse mode profile with high out-coupling efficiency exceeding 36% after multi-photon correction. We also observe Purcell enhanced spontaneous emission rate up to 4. Using this source, we generate linearly polarized, high purity single photons at 1.3 μm wavelength and demonstrate the indistinguishable nature of the emission using a two-photon interference measurement, which exhibits indistinguishable visibilities of 18% without post-selection and 67% with post-selection. Our results provide a promising approach to generate bright, deterministic single photons at telecom wavelength for applications in quantum networking and quantum communication.* Email: edowaks@umd.edu 2 Single photon sources are important building blocks for optical quantum information processing [1][2][3][4]. They are essential to generate photonic quantum bits (qubits) that can travel long distances over optical fibers and interconnect distant quantum network nodes [5][6][7]. Efficient on-demand single photon sources also enable quantum computation schemes based on either linear [3, 4] or nonlinear [8] optical elements.Many applications in quantum communication require deterministic single-photon sources that emit at telecom wavelengths. Parametric down-conversion sources can operate in this wavelength range [9, 10] but provide only heralded single-photon states and cannot be easily extended to ondemand operation. In contrast, single quantum emitters provide the potential for creating ondemand single-photon sources [11, 12]. Quantum dots in III-V semiconductors are particularly promising quantum emitters that generate single photons with high indistinguishability at nearinfrared wavelengths [13][14][15][16][17][18], and are also compatible with electrical injection [19,20] and integration with nanophotonic structures [21][22][23][24]. A number of works have extended the emission of III-V quantum dots to telecom wavelengths by optimizing materials and growth parameters [25][26][27][28][29][30][31]. However, an on-demand source of indistinguishable single photons remains an outstanding challenge at telecom wavelength.In this work, we demonstrate two-photon interference from a bright single photon source at telecom wavelengths. We use a single InAs/InP quantum dot in a photonic crystal cavity to attain bright and highly polarized single-photon emission at telecom wavelengths. Rather than using the fundamental mode of the ca...