Shaped pulses for transient compensation in quantum-limited electron spin resonance spectroscopy

[Display omitted] •Bump-shaped pulses suppress transients in quantum-limited ESR spectroscopy at 10 mK.•Bump-shaped pulses enable driving spins with a bandwidth larger than the cavity.•Bump-shaped pulses increase the Signal-to-Noise Ratio.•Bump-shaped pulses enable CPMG sequences with short inter-pulse delay. In high sensitivity inductive electron spin resonance spectroscopy, superconducting microwave resonators with large quality factors are employed. While they enhance the sensitivity, they also distort considerably the shape of the applied rectangular microwave control pulses, which limits the degree of control over the spin ensemble. Here, we employ shaped microwave pulses compensating the signal distortion to drive the spins faster than the resonator bandwidth. This translates into a shorter echo, with enhanced signal-to-noise ratio. The shaped pulses are also useful to minimize the dead-time of our spectrometer, which allows to reduce the wait time between successive drive pulses.