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

We report on long-term measurements of a high-coherent, non-tunable transmon qubit, revealing low frequency burst noise in coherence and transition frequency. We present a simultaneous measurement of the qubit's relaxation and dephasing rates as well as resonance frequency fluctuations, and analyze their correlations. These yield information about the microscopic origin of the intrinsic decoherence mechanisms in Josephson qubits and their fluctuation dynamics. From a spectral noise analysis we obtain further evidence for our presented model of a small number of dominant fluctuators.