Physics Colloquium with Eli Levenson-Falk on Superconducting Circuits
Superconducting circuits have been used to make scalable quantum bit (qubit) devices, with high coherence and easy addressability. Decades of development have improved these devices to the point that they can be combined into noisy intermediate-scale quantum (NISQ) processors, which have already been used to demonstrate quantum advantage over classical processors. Superconducting qubits rely on lossless transport of supercurrent in order to achieve high coherence. However, quasiparticle excitations of the superconducting state can give rise to lossy transport, causing qubit state transitions and fast decoherence. Furthermore, "bursts" of these quasiparticles from high-energy radiation (such as muon impacts) can cause correlated errors in many qubits across a chip, breaking most quantum error correction architectures. In this talk I will give an introduction to quasiparticles and where they come from. I will show recent results from my group demonstrating real-time detection of quasiparticles trapping in the Andreev states of a nanobridge Josephson junction, and explain how these measurements can be used to probe quasiparticle behavior. And I will discuss possible techniques for mitigating quasiparticle-mediated decoherence in superconducting qubits.
This colloquium will be in person. If you prefer to join via Zoom, please register at the link below.