Stability of superconducting resonators: motional narrowing and the role of Landau-Zener driving of two-level defects

Abstract

Frequency instability of superconducting resonators and qubits leads to dephasing and time-varying energy-loss and hinders quantum-processor tune-up. Its main source is dielectric noise originating in surface oxides. Thorough noise studies are needed in order to develop a comprehensive understanding and mitigation strategy of these fluctuations. Here we use a frequency-locked loop to track the resonant-frequency jitter of three different resonator types---one niobium-nitride superinductor, one aluminium coplanar waveguide, and one aluminium cavity---and we observe strikingly similar random-telegraph-signal fluctuations. At low microwave drive power, the resonators exhibit multiple, unstable frequency positions, which for increasing power coalesce into one frequency due to motional narrowing caused by sympathetic driving of individual two-level-system defects by the resonator. In all three devices we probe a dominant fluctuator, finding that its amplitude saturates with increasing drive power, but its characteristic switching rate follows the power-law dependence of quasiclassical Landau-Zener transitions.

References in corpus (15)

• Microwave photonics with superconducting quantum circuits
• Decoherence benchmarking of superconducting qubits
• Materials loss measurements using superconducting microwave resonators
• Reducing intrinsic loss in superconducting resonators by surface treatment and deep etching of silicon substrates
• Observation of directly interacting coherent two-level systems in a solid
• Microscopic origin of low frequency flux noise in Josephson circuits
• Coherent Quasiclassical Dynamics of a Persistent Current Qubit
• Characterization and reduction of microfabrication-induced decoherence in superconducting quantum circuits
• Generalized Tunneling Model for TLS in amorphous materials and its predictions for their dephasing and the noise in superconducting microresonators
• Two-level systems in superconducting quantum devices due to trapped quasiparticles
• Coherence of an optically illuminated single nuclear spin qubit
• Large-amplitude driving of a superconducting artificial atom: Interferometry, cooling, and amplitude spectroscopy
• High Quality 3-Dimensional Aluminum Microwave Cavities
• Relaxation of Josephson qubits due to strong coupling to two-level systems
• Low-Loss Superconducting Nanowire Circuits Using a Neon Focused Ion Beam