Investigating microwave loss of SiGe using superconducting transmon qubits

Silicon-germanium (SiGe) is a material that possesses a multitude of applications ranging from transistors to electro-optical modulators and quantum dots. The diverse properties of SiGe also make it attractive to implementations involving superconducting quantum computing. Here, we demonstrate the fabrication of transmon quantum bits on SiGe layers and investigate the microwave loss properties of SiGe at cryogenic temperatures and single photon microwave powers. We find relaxation times of up to 100 μs, corresponding to a quality factor Q above 4 M for large pad transmons. The high Q values obtained indicate that the SiGe/Si heterostructure is compatible with state-of-the-art performance of superconducting quantum circuits.