Single-step phase-engineered pulse for active readout cavity reset with a known qubit state
Phys. Rev. Applied 26, 054020 – Published 6 November, 2026
DOI: https://doi.org/10.1103/9cmh-2yhz
Abstract
In a circuit quantum electrodynamic architecture, we experimentally demonstrate a hardware-efficient and qubit-state-dependent single-step phase-engineered (SSPE) pulse scheme for actively depopulating a readout cavity. The protocol appends a reset segment with tailored amplitude and phase to a square readout pulse. Within the linear-response regime, the optimal reset amplitude scales proportionally with the readout amplitude, while the optimal reset phase remains invariant, significantly simplifying the experimental calibration procedure. For a known qubit state, time-resolved measurements demonstrate that the SSPE pulse achieves faster cavity depletion than the CLEAR protocol. Crucially, this approach enables arbitrarily fast, overshoot-free depletion of the cavity photon population, with the ultimate reset rate constrained by the available drive amplitude and the finite analog bandwidth of the measurement chain. A comprehensive evaluation of the quantum nondemolition character reveals no measurable increase in non-QND measurement errors (non-QNDness) relative to the free-decay and CLEAR protocols. The remaining non-QNDness is predominantly attributable to state switching induced by qubit relaxation during the readout process. These results establish the SSPE scheme as a practical and scalable approach for achieving rapid and smooth cavity reset in superconducting quantum circuits in the case of a known qubit state.
