QC-4-BW – Diamond-based spintronic quantum register for a scalable quantum processor

Project visual: Knots on blue diamond
© Siarhei – stock.adobe.com | Fraunhofer IAF

Within the Competence Center Quantum Computing Baden-Württemberg a miniaturized and scalable quantum processor will be developed. It will be evaluated and compared to the superconducting quantum processors of the IBM quantum computer »Quantum System One«, which has a quantum volume of 30. The targeted quantum processor is based on optically coupled quantum registers, where each quantum register is formed by 10 nuclear spin-based qubits and one electron spin.

The goal in the first phase of the project is to develop a diamond-based spintronic quantum register for a scalable quantum processor to evaluate quantum chemical processes. For this purpose, a 10-qubit quantum register is being developed, which is the only register realized so far that also has an integrated quantum memory.

The key element of the quantum register is an optically addressable color center in diamond. This color center has an electron spin which is used as an input and output qubit and which is strongly coupled to about 10 nuclear spins of surrounding 13C atoms. Since the strength of the coupling between the electron spin and the 10 nuclear spins far exceeds their decoherence rate, two-qubit gates can be realized between electron spin and nuclear spin or between nuclear spins (indirectly coupled via electron spins). Furthermore, the individual nuclear spins are used as one-qubit gates. In addition to the 10 strongly coupled nuclear spins, the quantum register contains another 20-40 nuclear spins, which are more weakly coupled to the electron spin of the color center due to their greater distance and are used to build a quantum memory.

The performance of the quantum register, the qubit topology and the one- and two-qubit quantum gates will be compared with the corresponding components of the IBM Quantum System One.


QC-4-BW – Development and benchmarking of a diamond-based spintronic quantum register for a scalable quantum processor



2021 – 2024


Ministry of Economic Affairs, Labour and Tourism Baden-Württemberg


Fraunhofer IAF


  • Development of a novel new generation of spin-based quantum registers with an integrated memory for quantum mechanical states
  • Comparison of the performance of spin-based and superconducting qubit technologies for use in application-relevant quantum computers

Funded by the Ministry of Economic Affairs, Labour and Tourism Baden-Württemberg

Further information


Quantum Computing at Fraunhofer IAF

All information about research in quantum computing at Fraunhofer IAF can be found here.


Competence Center Quantum Computing

The Competence Center Quantum Computing in Baden-Württemberg connects stakeholders in the state.