Single-Step Phase-Engineered Pulse for Active Readout Cavity Reset in Superconducting Circuits

TL;DR

This paper introduces a simple, hardware-efficient single-step phase-engineered pulse scheme for actively resetting readout cavities in superconducting circuits, significantly improving reset speed and reducing backaction.

Contribution

The authors develop and experimentally validate a novel SSPE pulse that simplifies calibration and enhances cavity reset performance in circuit QED systems.

Findings

Accelerates cavity photon depletion by up to six times

Reduces qubit backaction compared to other pulse schemes

Simplifies calibration by invariant reset phase

Abstract

In a circuit QED architecture, we experimentally demonstrate a simple and hardware-efficient Single-Step Phase-Engineered (SSPE) pulse scheme for actively depopulating the readout cavity. The method appends a reset segment with tailored amplitude and phase to a normal square readout pulse. Within the linear-response regime, the optimal reset amplitude scales proportionally with the readout amplitude, while the optimal reset phase remains nearly invariant, significantly simplifying the calibration process. By characterizing the cavity photons dynamics, we show that the SSPE pulse accelerates photon depletion by up to a factor of six compared to passive free decay. We further quantify the qubit backaction induced by the readout pulse and find that the SSPE pulse yields the lowest excitation and relaxation rates compared to a Square and CLEAR pulses. Our results establish the SSPE scheme as a practical and scalable approach for achieving fast, smooth, low-backaction cavity reset in superconducting quantum circuits.