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Spin-active color centers in silicon carbide for telecom-compatible quantum technologies

PhD ceremony:Mr T. (Tom) Bosma
When:February 19, 2021
Supervisor:prof. dr. ir. C.H. (Caspar) van der Wal
Co-supervisor:dr. R.W.A. (Remco) Havenith
Where:Academy building RUG
Faculty:Science and Engineering

The research described in this thesis aims at characterizing and identifying color-center defects with interesting properties in silicon carbide. These experiments were all optical, employing wavelength-tunable lasers to probe this solid-state material. Potential applications for these defects systems exist in e.g. long-distance quantum key distribution and in (bio) sensing. We discovered that ensembles of molybdenum impurity atoms in SiC have favorable electronic and magnetic properties for such qubit applications. Moreover, we measured the molybdenum electronic spin-relaxation times to exceed seconds at low temperatures.

We also investigated the occurrence of electromagnetically induced transparency (EIT) in divacancy defect ensembles. This quantum-physical phenomenon would allow for the coherent storage of single photons in a material. Solid-state materials typically suffer from  a spread in the values of certain material properties. This inhomogeneity  usually prevents us to establish EIT. However, we studied how to successfully circumvent this issue. Additional work is done to analyze SiC's prospects as platform for integrated optical applications that can be easily combined with existing semiconductor architectures. As such, we engineered a novel single-crystal SiC waveguide structure where n-type doped layers are used as cladding material, enabling the confinement of visible and infrared light inside the material.

See also: Defects promise quantum communication through standard optical fiber