Date of Award

Spring 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Physics

First Advisor

Devoret, Michel

Abstract

The development of fault-tolerant quantum computers relies critically on fast and accurate readout of qubit states. In state-of-the-art superconducting quantum processors, the readout operations exhibit higher error rates and longer execution times compared to single- and two-qubit gates, bottlenecking their performance. How can we realize faster readout with lower error rates in superconducting circuits? In this dissertation, we answer this question through addressing two pressing limitations in the dispersive readout scheme: readout-induced state transitions and Purcell decay of the qubit. We introduce the "readout channel benchmarking" technique for the faithful benchmarking of readout performance accounting for the readout-induced state transitions. We further identify the mechanisms behind such unwanted transitions as multi-quanta resonances activated by the drive, and parse them into different categories based on their predictability. To address Purcell decay, we implement a "dimon" architecture that provides intrinsic Purcell-protection, achieving fast, high-fidelity dispersive readout. Through optimization of readout frequency guided by Floquet simulation, we demonstrate successful mitigation of readout-induced leakage errors in the dimon circuit.These advances provide both practical solutions for immediate implementation and fundamental insights for future improvements of the readout in superconducting quantum processors.

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