Philipp Mutter

Noise affects the coherence of qubits and thereby places a bound on the performance of quantum computers. We theoretically study a generic resonator-coupled two-level system with fluctuating control parameters and find that characteristic features of the noise are imprinted in the transient transmission through the resonator. We present analytical expressions for the resonator response and propose a novel way of extracting the noise power spectral density in a frequency band only bounded by the range of the qubit-cavity detuning and with an exponentially decaying error due to finite measurement times. Finally, we discuss possible noise spectroscopy techniques for quadratically coupled systems and using the long-time transmission.