  The parity modulation of the ground state of a superconducting island is a
direct consequence of the presence of the Cooper pair condensate preferring an
even number of charge carriers. The addition energy of an odd, unpaired
quasiparticle equals to the superconducting gap, $\Delta$, suppressing single
electron hopping in the low temperature limit. Controlling the quasiparticle
occupation is of fundamental importance for superconducting qubits as single
electron tunneling results in decoherence. In particular, topological quantum
computation relies on the parity control and readout of Majorana bound states.
Here we present parity modulation for the first time of a niobium titanite
nitride (NbTiN) Cooper-pair transistor coupled to aluminium (Al) leads. We show
that this circuit is compatible with the magnetic field requirement in the
range of 100 mT of inducing topological superconductivity in spin-orbit coupled
nanowires. Our observed parity lifetime exceeding 1 minute is several orders of
magnitude higher than the required gate time of flux-controlled braiding of
Majorana states. Our findings readily demonstrate that a NbTiN island can be
parity-controlled and therefore provides a good platform for superconducting
coherent circuits operating in a magnetic field.
