On-chip quantum photonics for complex quantum networking

光子是光的基本粒子，代表着新兴量子技术的基本资源，如量子通信和量子计算。为了对光子进行操作，有必要建立类似于电子电路的光电路。这些电路需要能够发射明确数量的光子的源、能够传播光子的波导、能够在电路中的不同光子之间相互作用的元件以及高灵敏度的探测器。在获得这种量子光子电路的不同策略中，半导体平台特别有吸引力，因为它的制造技术很发达，而且有可能在电路中集成高质量的光子源。半导体光源的自然选择是由所谓的量子点代表的，量子点是一种纳米结构，与经典光源不同，它可以按需发射单光子。尽管利用这种架构构建复杂网络的潜力很大，但进展仅限于只有一个量子点的电路。原因是，芯片中的不同量子点通常位于非最佳位置，并发出不同颜色和不同特性的光子。这阻碍了不同光子之间的有效相互作用，并严重限制了潜在的应用范围。本项目的目标是开发和使用一个创新的平台，能够在一个光子电路中同时运行多个量子点源。为了实现这一目标，我们将结合斯图加特大学和林茨大学现有的互补专业知识来制造光子芯片，在这种芯片中，不同量子点发出的光子的颜色和性质可以通过机械变形进行精确控制。反过来，后者将通过将光子电路放置在专利压电平台上来实现，该平台可以将施加的电压转换为可控的变形。与文献中提出的不同方法不同，我们将精确地将量子点放置在光子电路的输入端，并通过我们的新的压电式平台精确地控制独立源的发射特性。为了最大限度地增加成功的机会，我们将研究两种不同的半导体材料系统。这将使我们能够展示迄今为止实现的最高水平的光子相互作用，从而为复杂网络铺平道路。

Photons, the elementary particles of light, represent essential resources for emerging quantum technologies, such as quantum communication and quantum computation. In order to perform operations with photons, it is necessary to build up circuits for light, similar to electronic circuits. These circuits require sources capable of emitting a well-defined number of photons, waveguides - where photons can propagate, elements enabling interaction between different photons in the circuit, and highly-sensitive detectors. Among different strategies to obtain such “quantum photonic circuits”, semiconductor platforms are particularly attractive because of the well-developed fabrication technologies and the possibility to integrate high-quality photon sources in the circuit. The natural choice for the semiconductor source is represented by so-called quantum dots, which are nanoscopic structures that, different from classical sources, can emit single photons “on demand”. In spite of the potential of building up complex networks with this architecture, progress is limited to circuits with only one quantum dot. The reason is that different quantum dots in a chip are usually located at non-optimal positions and emit photons with different colors and with different characteristics. This hinders the efficient interaction between different photons and severely limits the range of potential applications.The goal of this project is to develop and use an innovative platform enabling the simultaneous operation of multiple quantum dot sources in a photonic circuit. To achieve this goal, we will combine complementary expertise available at the Universities of Stuttgart and Linz to build up photonic chips, where the color and properties of photons emitted by different quantum dots can be precisely controlled using mechanical deformation. In turn, the latter will be achieved by placing the photonic circuits on top of a patented piezoelectric platform, which convert applied voltages in controllable deformations. Different form approaches presented in the literature, we will precisely place quantum dots at the inputs of the photonic circuit and precisely control the emission properties of independent sources by our new piezoelectric platform. To maximize chances of success we will work on two different semiconductor material systems. This shall allow us to demonstrate the highest levels of photon interaction achieved to date, thus paving the way to complex networks.