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.

Biography

I received my bachelor's from Harvard in 2008 and my PhD from Berkeley in 2013 working in Prof. Irfan Siddiqi's Quantum Nanoelectronics Lab. My research there centered on using nanobridge Josephson junctions for ultra-sensitive magnetometry and amplification. I then did a postdoc in Prof. Aharon Kapitulnik's group at Stanford, where I worked on sub-mm gravity measurements, axion detection, and transport in unconventional superconductors and bad metals. After this brief excursion to other fields, I returned to superconducting devices when I joined the faculty at USC in 2017. In 2021 I won the Cottrell Scholar award, and I am the editor-in-chief of QuBytes.org, the Quantum Information Reader's Digest.