Ultra low-loss single-crystalline material platform for high-Q quantum devices

Quantum technologies is a rapidly grown research area, which have the potential to lead the revolution in supercomputing, sensing, global communications and security. The leading quantum computing concepts of design like superconductive qubits, optical quantum computing devices, solid-state and hybrid quantum systems are based on traditional semiconductor technology platform. However, new materials and nanoscale structures fabrication techniques are needed to explore the underlying physics and fulfill the subsequent specifications. Losses in thin films, surface, structure and interfaces quality are coming into the fore.
Here we present a new approach for high vacuum deposition of single-crystalline metallic films with extremely low losses, which we name the SCULL (Single-crystalline Continuous Ultra-smooth Low-loss Low-cost) process. Fabricated films show perfect crystallinity (FWHM for ω-scan is better than 0.3), best published optical, superconductive, electrical properties and sub-0.5nm roughness. We demonstrate perfect silver/gold plasmonic films and superconductive aluminum films. With SCULL films the longest SPP propagation length (200 µm at λ = 780 nm) and the brightest single-photon source (over 35 million photons per second) at room temperature is demonstrated.