Characterizing noise for capacitively-shunted flux qubits

Capacitively-shunted flux qubits (CSFQs), due to their high anharmonicity together with reduced persistent currents allow for relatively fast control pulses and long coherence times. This makes them a suitable candidate for both gate model quantum computing and quantum annealing. We report a joint theoretical-experimental study of 1/f noise in CSFQs using Macroscopic Resonance Tunneling (MRT). MRT has been used for flux qubits to characterize low-frequency flux noise using well stablished theoretical models. A detailed theoretical explanation of higher order MRT with correction of junction asymmetry is important for our understanding of noise in CSFQs. We carry out analyses of different theoretical models that account for relaxation and dephasing to explain experimental T₁ and T₂ results obtained from studies of CSFQs.