Interference Purcell Filter for Fast, Modular, and Hardware-Efficient Quantum Measurement

Abstract

This thesis proposes a method to suppress Purcell decay for fast, modular, and hardware-efficient quantum measurement that we call an “interference” Purcell filter. Superconducting qubits experience many decay channels, one of which is Purcell decay, or leakage of the qubit state into the readout line. The proposed work suppresses Purcell decay by coupling the readout resonator at two points on the readout line to create a destructive interference effect, enabling a small and space-efficient footprint. The Purcell suppression is compatible with large resonator decay rates, making it a suitable design as quantum error correction schemes move toward faster readout. Unlike many existing methods to suppress Purcell decay, the proposed design does not require an “open” or weakly-coupled port, the removal of which would improve modularity and expedite the design of many-qubit systems.