Deep learning of quantum entanglement from incomplete measurements

The quantification of the entanglement present in a physical system is of paramount importance for fundamental research and many cutting-edge applications. Now, achieving this goal requires either a priori knowledge on the system or very demanding experimental procedures such as full state tomography or collective measurements. Here, we demonstrate that, by using neural networks, we can quantify the degree of entanglement without the need to know the full description of the quantum state. Our method allows for direct quantification of the quantum correlations using an incomplete set of local measurements. Despite using undersampled measurements, we achieve a quantification error of up to an order of magnitude lower than the state-of-the-art quantum tomography. Furthermore, we achieve this result using networks trained using exclusively simulated data. Last, we derive a method based on a convolutional network input that can accept data from various measurement scenarios and perform, to some extent, independently of the measurement device.

High Extraction Efficiency Source of Photon Pairs Based on a Quantum Dot Embedded in a Broadband Micropillar Cavity

The generation of photon pairs in quantum dots is in its nature deterministic. However, efficient extraction of photon pairs from the high index semiconductor material requires engineering of the photonic environment. We report on a micropillar device with 69.4(10)% efficiency that features broadband operation suitable for extraction of photon pairs. Opposing the approaches that rely solely on Purcell enhancement to realize the enhancement of the extraction efficiency, our solution exploits a suppression of the emission into the modes other than the cavity mode. Furthermore, the design of the device can be further optimized to allow for an extraction efficiency of 85%.

Purcell-Enhanced Single Photon Source Based on a Deterministically Placed WSe2 Monolayer Quantum Dot in a Circular Bragg Grating Cavity

We demonstrate a deterministic Purcell-enhanced single photon source realized by integrating an atomically thin WSe2 layer with a circular Bragg grating cavity. The cavity significantly enhances the photoluminescence from the atomically thin layer and supports single photon generation with g(2)(0) < 0.25. We observe a consistent increase of the spontaneous emission rate for WSe2 emitters located in the center of the Bragg grating cavity. These WSe2 emitters are self-aligned and deterministically coupled to such a broadband cavity, configuring a new generation of deterministic single photon sources, characterized by their simple and low-cost production and intrinsic scalability.

Hyperspectral study of the coupling between trions in WSe2 monolayers to a circular Bragg grating cavity

Circular Bragg gratings compose a very appealing photonic platform and nanophotonic interface for the controlled light-matter coupling of emitters in nanomaterials. Here, we discuss the integration of exfoliated monolayers of WSe2 with GaInP Bragg gratings. We apply hyperspectral imaging to our coupled system, and explore the spatio-spectral characteristics of our coupled monolayer-cavity system. Our work represents a valuable step towards the integration of atomically thin quantum emitters in semiconductor nanophotonic cavities.

Quartz tuning fork mass change sensing for FIB/SEM technology

In this paper we present a metrological method for determination of mass density of focused ion beam induced deposition (FIBID) materials using quartz tuning fork (QTF) mass change sensors. Dimension and density determination of FIBID deposited nanostructures is necessary to develop and reliable and repeatable microfabribrication technology of the highest versatility. The proposed metrological methodology allows to determine mass change with 5 pg resolution and accuracy below 5 % if density is considered. The described method is suitable for precise FIBID precursor parameters determination conducted during the deposition as actuation and signal read-out of the applied QTF can be performed electrically. High accuracy, resolution and stability are ensured due to excellent properties of quartz forming the sensor structure.

Strain-Tunable Single Photon Sources in WSe2 Monolayers

The appearance of single photon sources in atomically thin semiconductors holds great promises for the development of a flexible and ultracompact quantum technology in which elastic strain engineering can be used to tailor their emission properties. Here, we show a compact and hybrid two-dimensional semiconductor-piezoelectric device that allows for controlling the energy of single photons emitted by quantum emitters localized in wrinkled WSe₂ monolayers. We demonstrate that strain fields exerted by the piezoelectric device can be used to tune the energy of localized excitons in WSe₂ up to 18 meV in a reversible manner while leaving the single photon purity unaffected over a wide range. Interestingly, we find that the magnitude and, in particular, the sign of the energy shift as a function of stress is emitter dependent. With the help of finite element simulations we suggest a simple model that explains our experimental observations and, furthermore, discloses that the type of strain (tensile or compressive) experienced by the quantum emitters strongly depends on their localization across the wrinkles. Our findings are of strong relevance for the practical implementation of single photon devices based on two-dimensional materials as well as for understanding the effects of strain on their emission properties.

Surface Modification of Polycarbonate by an Atmospheric Pressure Argon Microwave Plasma Sheet

The specific properties of an atmospheric pressure plasma make it an attractive tool for the surface treatment of various materials. With this in mind, this paper presents the results of experimental investigations of a polycarbonate (PC) material surface modification using this new type of argon microwave (2.45 GHz) plasma source. The uniqueness of the new plasma source lies in the shape of the generated plasma-in contrast to other microwave plasma sources, which usually provide a plasma in the form of a flame or column, the new ones provides a plasma in the shape of a regular plasma sheet. The influence of the absorbed microwave power and the number of scans on the changes of the wettability and morphological and mechanical properties of the plasma-treated PC samples was investigated. The mechanical properties and changes in roughness of the samples were measured by the use of atomic force microscopy (AFM). The wettability of the plasma-modified samples was tested by measuring the water contact angle. In order to confirm the plasma effect, each of the above-mentioned measurements was performed before and after plasma treatment. All experimental tests were performed with an argon of flow rate up to 20 L/min and the absorbed microwave power ranged from 300 to 850 W. The results prove the capability of the new atmospheric pressure plasma type in modifying the morphological and mechanical properties of PC surfaces for industrial applications.