High-Quality Copper Oxide Crystals Synthesized for Quantum Photonics

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Researchers from KTH Royal Institute of Technology report that they have developed a scalable production method for cuprous oxide (Cu2O) micrometer-size crystals. Also involved in the study were the Institute of Solid State Physics; Graz University of Technology, Austria; and Laboratoire d’Optique Appliquée Ecole Polytechnique, Palaiseau, France.

“The unique properties of Cu2O can lead to new schemes for quantum information processing with light in the solid state, which are difficult to realize with other materials,” said Stephan Steinhauer, a researcher in KTH’s Quantum Nano Photonics group. “This work paves the way for the widespread use of Cu2O in optoelectronics and for the development of novel device technologies.”

To synthesize the crystals, a copper thin film is heated to high temperatures in vacuum conditions. In their study, which was published in Communications Materials, the researchers at KTH took this method and identified the growth parameters to achieve Cu2O microcrystals with optical material quality.

The process is compatible with standard silicon fabrication techniques and allows the possibility for photonic circuit integration.

“The majority of quantum optics experiments with this material have been performed with geological samples found in mines, for instance, the Tsumeb mine in Namibia,” Steinhauer said. “Our synthesis method is associated with very low-cost fabrication, suitable for mass production, and does not require gases or chemicals that are toxic or harmful for the environment.”

Steinhauer said the work lays the foundation for realizing quantum technologies based on solid-state Rydberg excitations, which are excited quantum states with high principal quantum number.

According to Steinhauer, these excitations can be interfaced with photonic integrated circuits, aiming at on-chip generation and manipulation of light at the single-photon level.

“Exciting challenges lie ahead to translate quantum information processing and quantum sensing schemes previously developed for Rydberg atoms into the solid-state environment of a semiconductor crystal at the micrometer or nanometer scale.”

Published: April 2020
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of physics that emerged in the early 20th century to explain phenomena observed on very small scales, where classical physics fails to provide accurate explanations. In the context of quantum theory, several key concepts are associated with the term quantum: Quantum mechanics: This is the branch of...
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and manipulation of light using nanoscale structures and materials, often at dimensions comparable to or smaller than the wavelength of the light being manipulated. Aspects and applications of nanophotonics include: Nanoscale optical components: Nanophotonics involves the design and fabrication of...
quantum optics
The area of optics in which quantum theory is used to describe light in discrete units or "quanta" of energy known as photons. First observed by Albert Einstein's photoelectric effect, this particle description of light is the foundation for describing the transfer of energy (i.e. absorption and emission) in light matter interaction.
Research & TechnologyInstitute for Solid State Physicsquantumnanophotonicsmicrocrystalsquantum opticscopper oxideEuropecrystalssilicon photonicsphotonic integrated circuitsTech Pulse

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