  Dynamical error suppression techniques are commonly used to improve coherence
in quantum systems. They reduce dephasing errors by applying control pulses
designed to reverse erroneous coherent evolution driven by environmental noise.
However, such methods cannot correct for irreversible processes such as energy
relaxation. In this work, we investigate a complementary, stochastic approach
to reducing errors: instead of deterministically reversing the unwanted qubit
evolution, we use control pulses to shape the noise environment dynamically. In
the context of superconducting qubits, we implement a pumping sequence to
reduce the number of unpaired electrons (quasiparticles) in close proximity to
the device. We report a 70% reduction in the quasiparticle density, resulting
in a threefold enhancement in qubit relaxation times, and a comparable
reduction in coherence variability.
