Fraunhofer IAF group developing ‘scalable, diamond-based quantum microprocessors’

Three-year project “Deutsche Brilliance” launched with Quantum Brilliance startup and Ulm University.

A new joint research and development project called “Deutsche Brilliance” (DE-Brill), launched last month, aims to enable scalable diamond quantum microprocessors with the ultimate objective of advancing the economic usability of quantum computing.

Germany’s German Federal Ministry of Education and Research (BMBF) is funding the cooperation between Fraunhofer Institute for Applied Solid State Physics (IAF), start-up Quantum Brilliance, and Ulm University for three years with €15.6 million through the “Enabling Start-up” measure. For the best possible exchange between the project partners, a team of Quantum Brilliance is located at Fraunhofer IAF.

DE-Brill aims to harness the special material properties of diamond and develop technologies for manufacturing and controlling diamond-based quantum microprocessors (“QPUs” ) by 2025. QPUs are intended to provide quantum advantages for applications such as edge computing—a basic technological prerequisite for the complex infrastructure of the Internet of Things.

Advantages and limitations

A central challenge in the development of quantum computers is the technological realization of quantum bits. Various approaches exist for the creation of qubits. They can, for example, be created based on nuclear spins in solids. In this regard, a relatively new approach is the use of diamond as a host material.

Diamond-based quantum computers promise significant advantages in practical applications: they can be built and operated more energy-efficiently, reliably and compactly than quantum processors based on superconducting qubits. There is no need for cooling them to cryogenic temperatures and evacuating them in complex systems.

In fact, diamond qubits operate at room temperature and ordinary pressure ratios due to the extremely stable diamond crystal lattice. Diamond qubits are created through the quantum entanglement of quasi-free electrons in nitrogen-vacancy centers of the diamond crystal lattice.

However, current methods for the fabrication of such NV centers do not allow an upscaling of diamond-based qubits to sufficiently large assemblies of multiple qubits in the form of arrays, which are needed for quantum computing. So far, there is a lack of methods that allow a defined placement of nitrogen atoms in the crystal lattice. This, however, is necessary for the coupling of multiple NV centers to create larger arrays.

Scalable diamond quantum computers

In the course of its subproposal within the joint project, Fraunhofer IAF is developing growth processes for diamond substrates of the highest purity and quality. In close collaboration with Quantum Brilliance, it is also designing precision manufacturing techniques for the production of scalable arrays of diamond qubits. Researchers at the Fraunhofer IAF aim to achieve the necessary local accuracy in the placement of nitrogen atoms of less than one nanometer using scanning probe microscopy.

“This approach for the targeted placement of NV centers is so far unique and a crucial step towards scaling NV arrays for quantum computing applications,” explains Dr. Ralf Ostendorf, project leader on the side of Fraunhofer IAF. For this reason, the joint project” will also contribute to the further development of the technology with regard to future research projects as well as industrial applications in the fields of sensor technology, imaging or communication.

In parallel with the Fraunhofer IAF subproject, a team led by Prof. Dr. Fedor Jelezko at the Institute for Quantum Optics at Ulm University is working on defining scalable readout and control techniques for diamond-based qubits, which will allow their precise operation.