  Josephson junctions in InAs nanowires proximitized with an Al shell can host
gate-tunable Andreev bound states. Depending on the bound state occupation, the
fermion parity of the junction can be even or odd. Coherent control of Andreev
bound states has recently been achieved within each parity sector, but it is
impeded by incoherent parity switches due to excess quasiparticles in the
superconducting environment. Here, we show that we can polarize the fermion
parity dynamically using microwave pulses by embedding the junction in a
superconducting LC resonator. We demonstrate polarization up to 94% $\pm$ 1%
(89% $\pm$ 1%) for the even (odd) parity as verified by single shot
parity-readout. Finally, we apply this scheme to probe the flux-dependent
transition spectrum of the even or odd parity sector selectively, without any
post-processing or heralding.

Mesoscale and Nanoscale Physics;Superconductivity;Quantum Physics