Continuous Single-Shot Detection of Quasiparticle Trapping

Superconducting quantum circuits are plagued by nonequilibrium populations of quasiparticle excitations. These quasiparticles can cause relaxation and spurious excitation of qubit states, producing errors in a quantum algorithm, and can cause correlated errors that are particularly difficult to address with error correction. To mitigate the effects of these quasiparticles, we need to understand their behavior better. Measurements of quasiparticle trapping in the internal Andreev states of a Josephson junction provide an excellent tool for continuous, non-saturating detection of quasiparticles. I will present our recent results using a superconducting resonator incorporating two aluminum nanobridge Josephson junctions to detect up to 3 quasiparticles trapping at once with high fidelity. I will present measurements of the quasiparticle trapping and untraping behavior, and discuss how we can use our detector device to develop quasiparticle mitigation techniques.

Speaker: Eli Levenson-Falk, University of Southern California

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