Reflection‐Zero Waveforms for Selective Loading in Shared‐Line Superconducting Qubit Circuits

ABSTRACT Shared microwave lines reduce cryogenic wiring in superconducting processors, but a pulse sent through one line drives the dressed circuit instead of an isolated qubit. This network response can reflect energy and load spectator modes. In this work, we design microwave waveforms from reflection zeros of the dressed one‐port response. A zero sets both the microwave carrier and the finite envelope rise rate , so the incident field cancels the field re‐emitted into the input port during loading. A three‐qubit input‐output model and transient Advanced Design System simulations of weakly nonlinear Josephson circuits test this loading rule in the weak‐drive regime. Compared with equal‐energy Gaussian pulses at the same carriers, reflection‐zero waveforms raise target selectivity from 0.386–0.484 to 0.842–0.934 and crosstalk‐suppression ratios from 1.185–1.353 to 6.668–18.340. A ten‐qubit calculation further tests the construction in a larger crowded shared‐line network. In a lossy circuit, the true reflection‐zero drive preserves target loading while raising the crosstalk‐suppression ratio from 3.84 to 8.45 relative to a conjugate‐pole drive. The construction supplies the network‐matching stage of frequency‐multiplexed superconducting control and provides an initial envelope for subsequent gate calibration.