Characterizing noise sources of spin qubit devices with the anisotropy in relaxation and dephasing times

Spin qubits in semiconductor quantum dots devices are one of the promising platforms for building a quantum computer.  Understanding the noise that degrades their performance is a central issue.  Thus we wish to have experiments that can distinguish and characterize charge noise, evanescent-wave Johnson noise, and noise from nuclear spins and phonons.  To do this, we can use qubits that act as natural noise sensors and one would like to make them as sensitive as possible to the tensor structure of electric and magnetic noise.  We propose that rotating the external magnetic field can give much information about the noise tensor, which in turn sheds light on the noise mechanisms.  We compute the anisotropy in the relaxation time and the dephasing time of the qubit for these mechanisms and shows how to use this information to better understand the nature and position of the noise sources in present-day spin-qubit devices.