Correlating decoherence in transmon qubits: Low frequency noise by single fluctuators

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We report on long-term measurements of a highly coherent, non-tunable superconducting transmon qubit, revealing low-frequency burst noise in coherence times and qubit transition frequency.

• We achieve this through a simultaneous measurement of the qubit's relaxation and dephasing rate as well as its resonance frequency.
• The analysis of correlations between these parameters yields information about the microscopic origin of the intrinsic decoherence mechanisms in Josephson qubits.
• Our results are consistent with a small number of microscopic two-level systems located at the edges of the superconducting film, which is further confirmed by a spectral noise analysis.