Decoherence of qubits in spinless and spinful semiconductors

Spin defects in semiconductors provide a versatile material platform for quantum information processing, quantum sensing, and quantum computing with unprecedented high temperature capabilities. Magnetic field fluctuations due to various parasitic spin defects in the host material as well as interaction with lattice phonons cause decoherence and spin relaxation of spin qubits that limit current applications. It therefore of fundamental importance to study material related disturbances and develop mitigation strategies. In recent years, significant advances have been achieved on the theriacal characterization of decoherence [1-3] and spin relaxation [4,5] of spin qubits in semiconductors. The developed first principles methods led to new understanding of decoherence in various materials [6-8]. In my talk, I will present our latest computational results on various spin defects in silicon carbide (SiC) and hexagonal boron nitride (hBN). More specifically, I will discuss the spin state lifetime of divacancy and silicon vacancy qubits in a bath of electron and nuclear spins in SiC. [9,10] Furthermore, I will demonstrate that isotope purification may lead to unexpected enhancement of electron spin relaxation rates and magnetic field fluctuations due to the residual electron spin bath that may limit the lifetime and coherence time of spin qubits in materials. [11] By taking into account all the relevant effects, I will shed light on the interplay of the electron and nuclear spin bath and discuss the complex nuclear spin abundance dependence of the coherence time in isotope engineered host materials. In addition, I will present our latest results on the coherence of boron vacancy center in hBN.[8,12]