1 minute parity lifetime of a NbTiN Cooper-pair transistor

Abstract: 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.