The project seeks to demonstrate the operation of a quantum network node [1,2] based around NPL’s ion microtrap chip device [3-5], the most recent variants of which have been developed in collaboration with Kelvin Nanotechnology Ltd. Research will be split to address each technical ingredient required to address this challenge, develop appropriate solutions and quantify their performance independently. Following that, their combined operation will be demonstrated to ensure compatibility with no significant consequences. Ion-photon entanglement will be demonstrated in this system, thus concluding with a blueprint for a reproducible network node for a future multi-node network [6].  

The project will develop network node hardware incorporating the following features. 1) Ion microtrap chip; a latest generation device containing 11 experimental zones to separate out the functions of loading, state preparation, local qubit processing and ion-photon entanglement. 2)  Optically heated oven; containing two atomic species to enable optimum choice of qubit transitions for local operations and for photonic transitions. 3) Optical cavity; miniature assembly located around the packaged ion trap chip, while maintaining sufficient optical access to other zones. 4) Optical system to guide light in and out of the cavity in vacuum, and to stabilise the optical cavity with light that is non-resonant with the atomic system.  

Each aspect will be addressed separately; with a view to more widespread application, technical solutions suited to scalable manufacturing and assembly will be used. Demonstration of ion trapping will be performed using existing infrastructure in NPL’s testbed apparatus. Hardware and measurement techniques for single-photon detection and correlation will be enabled in collaboration with NPL’s photonics research team; a local network of fibres permits access to equipment such as high-efficiency superconducting single-photon detectors. This will enable efficient detection of ion-photon entangled states. 

Principal and immediate outputs of the project will be: 1) Showcase the use of a UK-made scalable ion microtrap in a quantum network node, demonstrating suitability for purpose. 2) A template for a reproducible ion trap network node. 3) A pathway to incorporate local qubit processing in a segmented ion trap array with a network node. Results will also point the route towards a multi-node network of UK ion traps. Furthermore, the research will highlight the activities of our industry collaborators, thus promoting the UK supply chain for scalable quantum computing.