Scalable integration of quantum emitters into photonic integrated circuits

Abstract

Scaling up photonic quantum devices to reach complexities allowing to solve real-world problems requires a platform enabling scalable integration of solid-state quantum emitter with a high yield. Their nanometer-size together with their excellent quantum optical properties make them the ideal candidates for on-chip photonic quantum technologies. However, robust, scalable integration remains elusive. Here, we discuss the state-of-the-art methods to integrate quantum emitters into photonic integrated circuits, emphasizing the pros and cons of the integration methods applicable for specific quantum emitters. Based on our thorough comparison we give our perspective on the most promising approaches and how to overcome the remaining challenges.

Assessing the Alignment Accuracy of State-of-the-Art Deterministic Fabrication Methods for Single Quantum Dot Devices

“…The spatial displacement of the QD from the center of nanostructures has led to a large discrepancy between the theoretically expected and experimentally measured Purcell factors, especially for devices with a QD in close proximity to the surface of the structure. − Furthermore, recently, it has been found that in the case of circular Bragg grating (CBG) cavities, a displacement between QD and photonic structure of only 100 nm can lead to a strong polarization anisotropy, which limits their usage for the generation of flying qubits based on the polarization degree of freedom such as polarization-entangled photon pairs . In addition, to fabricate optimal devices for scaling up to larger quantum photonic systems such as large-scale integrated quantum photonic circuits, it is necessary to reliably integrate quantum emitters into nanobeam or photonic crystal cavities with an alignment accuracy better than 50 nm to maintain appropriately high photon coupling efficiency (CE) and light–matter interaction.…”

Fast Characterization of Optically Detected Magnetic Resonance Spectra via Data Clustering

“…Spin defects in solid-state host materials have become prime candidate hardware systems for advanced quantum technologies. − Prominent representatives include atom-like quantum emitters in diamond, , silicon carbide, hexagonal boron nitride (hBN), , zinc oxide, transition metal dichalcogenides, as well as rare-earth ions in solids, , and optically active donors in silicon. , These atom-like emitters are attractive for quantum applications as they often possess spin states that can be readily manipulated and read out, while also displaying long coherence time, room-temperature operation, the ability to create entangled states, and spin-dependent optical transitions that allow for spin-photon interfacing and long-distance transmission of quantum information. , Additionally, the solid-state host materials are technology-ready. Potential devices can be realized leveraging well-established nanofabrication techniques from the semiconductor industry and hold prospects for seamless integration with on-chip electronic, magnetic and photonic nanostructures. − Relevant applications span over a wide range of fields including quantum communication − and computation, − quantum simulation, , and quantum metrology and sensing. ,, …”

Purcell Enhancement of Silicon W Centers in Circular Bragg Grating Cavities

“…To overcome this limitation, research efforts have focused on fiber-coupling or hybrid integration of external single-photon sources (SPS), emitting at telecom wavelengths for low absorption in silicon waveguides, such as III–V semiconductor quantum dots (QD) , and erbium ions in YSO . In spite of tremendous progress in telecom photon generation in various platforms, − the scalability of these approaches is challenged by coupling losses at interfaces …”

“…8 In spite of tremendous progress in telecom photon generation in various plat-forms, 9−13 the scalability of these approaches is challenged by coupling losses at interfaces. 14 A promising alternative route exploits the integration of isolated atoms into the photonic chip, such as erbium ions 15 or isolated defects acting as artificial atoms. 16−18 By embedding one such emitter in a SOI cavity, one expects to tailor its spontaneous emission (SE) thanks to cavity quantum electrodynamics (CQED) effects and to control the single-photon generation process.…”