ab initio computational searches for TLS in amorphous dielectrics

Superconducting qubits are subject to noise affecting resonance frequencies and loss due to interactions with two level systems (TLS). TLS have been determined to reside in dielectrics used in device fabrication and are most strongly coupled to the qubit when in dielectric volumes bathed in strong electric fields from the superconducting resonator. TLS, in abstract, could correspond to atomic rearrangements of the dielectric material that possess electric dipole moment changes and are separated by small energy differences, in order to couple to a roughly 5 GHz excitation. In order to identify and characterize TLS in amorphous dielectric materials, we performed computational searches for transition states utilizing forces generated from both density functional theory and classical potentials. We then analyzed the TLS by calculating the dipole moment changes and comparing the atomic displacements, energy barriers, and energy differences.