Quantum technologies in diamond enabled by laser processing

Integrated photonic circuits promise to be foundational for applications in quantum information and sensing technologies, through their ability to confine and manipulate light. A key role in such technologies may be played by spin-active quantum emitters, which can be used to store quantum information or as sensitive probes of the local environment. A leading candidate is the negatively charged nitrogen vacancy (NV-) diamond color center, whose ground spin state can be optically read out, exhibiting long (similar to 1 ms) coherence times at room temperature. These properties have driven research toward the integration of photonic circuits in the bulk of diamond with the development of techniques allowing fabrication of optical waveguides. In particular, femtosecond laser writing has emerged as a powerful technique, capable of writing light guiding structures with 3D configurations as well as creating NV complexes. In this Perspective, the physical mechanisms behind laser fabrication in diamond will be reviewed. The properties of waveguides, single- and ensemble-NV centers, will be analyzed, together with the possibility to combine such structures in integrated photonic devices, which can find direct application in quantum information and sensing. (C) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

Integrated photonic circuits with the ability to confine and manipulate light show promise for applications in quantum information and sensing technologies. The negatively charged nitrogen vacancy (NV-) diamond color center is a leading candidate as a spin-active quantum emitter, with the capability of optically reading its ground spin state and long coherence times at room temperature. The use of femtosecond laser writing allows for the fabrication of optical waveguides and NV complexes. This Perspective reviews the physical mechanisms of laser fabrication in diamond, analyzes the properties of waveguides, single- and ensemble-NV centers, and discusses the potential for their integration into photonic devices for quantum information and sensing.