Engineering superconducting qubits to reduce quasiparticles and charge noise

Phonon downconversion to suppress correlated errors in superconducting qubits

“…The resulting values for Γ p for both chips are low: Γ p = 0.360 s −1 (0.023 s −1 ) for the non-Cu (Cu) chip. To the best of our knowledge, Γ p for the non-Cu chip is consistent with the lowest rates for QP poisoning reported in the literature [23,24], while for the Cu chip our measured poisoning rate is an order of magnitude lower.…”

Parity switching in a full-shell superconductor-semiconductor nanowire qubit

“…The resulting ω = (139 ± 2) µeV is in reasonable agreement with the bulk superconducting gap of Al ∼ 200 µeV. The density of non-equilibrium QPs x 0 QP ∼ 10 −8 is among the lower values reported for similar systems [9,15,19].…”

“…This was recently used to study QPP in NWs similar to those investigated here but with the superconducting shell only covering half the facets, where it was found that QPP occured on the timescale of 100 µs and could have a non-monotonic dependence on magnetic field [9]. The effect of geometry was also studied with the dispersive technique [19]. Typical reported QPP time scales have ranged from 100 µs up to 1 s [9, [14][15][16][17][18][19].…”

“…The effect of geometry was also studied with the dispersive technique [19]. Typical reported QPP time scales have ranged from 100 µs up to 1 s [9, [14][15][16][17][18][19]. Methods to mitigate unwanted quasiparticles in superconducting circuits have included qubit pumping [20] and trapping of quasiparticles by vortices [21,22] or regions of normal metal [23].…”

Quasiparticle Poisoning of Superconducting Qubits from Resonant Absorption of Pair-breaking Photons

“…This detailed understanding of the physical mechanism for quasiparticle poisoning will allow realization of new qubit designs that are robust against pair-breaking radiation; additionally, it could form the basis for a new class of quantum sensors based on the transduction of photons to quasiparticles followed by subsequent qubit-based detection. We note that a recent experimental study explains the scaling of quasiparticle poisoning rate with qubit size in terms of our model, without direct validation of the detailed spectral response of the qubit devices [23].…”