We are developing processes for surface processing of diamonds at atomic resolution. In this way, we improve the quality of diamond qubit systems for quantum computers.
Quantum computers based on nitrogen defect sites, known as NV centers, have very great potential. However, a major challenge is the as yet insufficient control over the diamond surface. Particularly etched or polished surfaces have defects that can sensitively interfere with the qubits. In close collaboration with the QCI industry partners, we want to develop novel etching, termination and coating processes for diamond surfaces at the DLR Innovation Center Ulm, which prevent unwanted defects and minimize the interfering influence of the diamond surface on the qubits.
NV center technology will allow quantum computers to operate at room temperature – making compact, mobile quantum computers feasible. However, decoupling the qubits from interfering influences of the diamond surface is still a challenge. In close collaboration with industry partners at the DLR Innovation Center Ulm, we are therefore developing delicate processing technologies that are suitable for machining diamond surfaces with atomic resolution. Our aim is to treat the surfaces in such a way that the properties of the qubits are improved. In this way, we want to contribute to bringing this quantum computer technology even closer to application maturity, so that even more powerful quantum computers can be built.
Unlike metals, for instance, diamond does not form a native oxide. However, through a wide variety of processes, the top layer of atoms can be selectively bonded (terminated) with foreign atoms. This single atomic layer has immense effects. NV centers near the surface are also influenced by this termination. With appropriate termination of the surface, the charge state of underlying NV centers can be adjusted so that they can be used as qubits. Classical surface machining processes, and conventional plasma etching processes, inherently lead to defects on the surface. These can severely disrupt the spin state of surface NV centers. Therefore, we will develop innovative, gentle plasma-assisted etching processes that can remove such disruptive defects and create none themselves. Thus, we will address the challenge of developing homogeneous, reproducible processes that reliably enable qubits with long coherence times.