A superconductor free of quasiparticles for seconds

Material matters in superconducting qubits

“…It is interesting that recent measurements conducted on superconducting islands, which exhibited an exponential decrease in Cooper pair breaking events over a time scale of hundreds of days at operating temperatures, suggests that sources that are effectively constant on such timescales, such as environmental radioactivity or cosmic rays, may not be the dominant mechanism [319]. Such observations hint at the possibility that thermalization issues emanating from many potential places in the qubit environment, from dielectric materials on the chiplet and packaging [302] to ancillary electronic equipment within the dilution refrigerators, still need to be addressed.…”

Electrostatic control of quasiparticle poisoning in a hybrid semiconductor-superconductor island

“…Employing reflectometry, we count tunneling events on an island through that tunnel barrier in real time. Deep in the Coulomb valley the island shows no signal of quasiparticle tunneling on time scales ranging from sub-microsecond time scales to hours [35]. At charge degeneracy points, the tunneling rate varies by orders of magnitude with electrostatic gating of the island (Fig.…”

A Sub-GHz Impedance-Engineered Parametric Amplifier for the Readout of Sensors and Quantum Dots

“…The JPA chip (not shown) omits the λ/4 transmission line, and its sample holder has a simplified PCB (not shown) that lacks a reservation for L aux and C aux . Notably, a copy of the JPA characterized in this work has enabled the real-time counting of quasiparticles on a mesoscopic superconducting island [9]. There the JPA operated as a phase-sensitive preamplifier of a rf singleelectron transistor, but here we exclusively focus on standalone measurements in the phase-insensitive mode.…”

“…Despite the success of JPAs in cQED, a similarly widespread adoption has not yet occurred in lower radio frequency (rf) experiments. In the sub-GHz domain there are a few notable exceptions, though [6]- [9]. The low-frequency hindrances are partly due to technical challenges with the JPAs.…”