Danish quantum technology company Sparrow Quantum ApS has secured 31 million DKK ($4.5 million) in a seed funding round. The company, which was founded in Copenhagen in 2016 by Niels Bohr Institute professor Peter Lodahl, is focusing on light-matter interfaces for quantum technologies by bringing foundational quantum photonic components to market. Deterministic light-matter interfaces, according to the company, serve as foundational hardware, allowing fully secure quantum communication; a quantum internet; and a scalable, photon-based quantum computer. Sparrow Quantum will use the seed investment to accelerate the development of its products and services, as well as to expand its team. Sparrow Quantum’s first product is an on-chip single-photon source that can provide strings of more than 100 single photons without deteriorating quality and at a rate of more than 20 million single photons per second in fiber that the customer can directly deploy for multiphoton quantum simulations or quantum key distribution experiments. Sparrow Quantum ApS has secured $4 million in seed funding, which the company said represents the largest investment to date in a Danish quantum technology company. The company’s photonic quantum technology centers on two decades of work pioneered by the Niels Bohr Institute’s Peter Lodahl. Courtesy of Sparrow Quantum. According to Sparrow Quantum via its website, the company’s integrated 3- × 3-mm chip is made from indium arsenide/gallium arsenide quantum dot structures embedded in photonic crystal waveguides. The chip is sectioned into an array of structures engineered for emitting highly coherent single photons at specific wavelengths between 920 and 980 nm. For optimal performance, the chip must be mounted in a low-vibration cryostat with electrical and optical access. The quantum dot is excited by a pulsed laser that is focused onto the chip containing the quantum dot emitter via a confocal microscope objective. Single-photon emission is collected via the same objective, and the laser pump light is automatically filtered out thanks to the photonic crystal nanostructures. This process renders the single-photon stream ready to use, the company said. In addition to its product offerings, Sparrow Quantum plans to become a component provider in the quantum industry supply chain. The company plans to team with developers of quantum technology systems to incorporate its single-photon sources into large-scale commercial systems. At the Niels Bohr Institute, Lodahl previously demonstrated that light emission can be fully controlled using intricate photonic nanostructures. Lodahl currently heads the Center of Excellence for Hybrid Quantum Networks (Hy-Q), which is developing quantum hardware including single-photon sources, spin-photon interfaces, and photonic quantum gates.