Decoherence of a quantum two-level system by spectral diffusion

Abstract

We study the dephasing of an individual high-frequency tunneling two-level system (TLS) due to its interaction with an ensemble of low-frequency thermal TLSs which are described by the standard tunneling model (STM). We show that the dephasing by the bath of TLSs explains both the dependence of the Ramsey dephasing rate on an externally applied strain as well as its order of magnitude, as observed in a recent experiment [J. Lisenfeld et al.]. However, the theory based on the STM predicts the Hahn-echo protocol to be much more efficient, yielding too low echo dephasing rates, as compared to the experiment. Also the strain dependence of the echo dephasing rate predicted by the STM does not agree with the measured quadratic dependence, which would fit to a high-frequency white noise environment. We suggest that few fast TLSs which are coupled much more strongly to the strain fields than the usual TLSs of the STM give rise to such a white noise. This explains the magnitude and strong fluctuations of the echo dephasing rate observed in the experiment.

13 pages, 4 figures

References in corpus (8)

• Low-frequency noise as a source of dephasing of a qubit
• Decoherence in qubits due to low-frequency noise
• Generalized Tunneling Model for TLS in amorphous materials and its predictions for their dephasing and the noise in superconducting microresonators
• Measuring the temperature dependence of individual two-level systems by direct coherent control
• Decoherence spectroscopy with individual two-level tunneling defects
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Cited by in corpus (12)

• Towards understanding two-level-systems in amorphous solids -- Insights from quantum circuits
• Probing individual tunneling fluctuators with coherently controlled tunneling systems
• Effective qubit dephasing induced by spectator-qubit relaxation
• Transport Signatures of a Majorana Qubit and Read-out-induced Dephasing
• Nonuniversality and strongly interacting two-level systems in glasses at low temperatures
• Strain-spectroscopy of strongly interacting defects in superconducting qubits
• Experimentally revealing anomalously large dipoles in a quantum-circuit dielectric
• Rabi noise spectroscopy of individual two-level tunneling defects
• The effect of interactions and disorder on the relaxation of two-level systems in amorphous solids
• Anomalous low-energy properties in amorphous solids and the interplay of electric and elastic interactions of tunneling two-level systems
• Qubit dephasing by spectrally diffusing quantum two-level systems
• Thermal cycling -- evidence for a generalized tunneling model and a tool to distinguish noise sources in quantum circuits