Fig. 4: Qubit readout with the cryogenic pulse generator.
From: A cryogenic on-chip microwave pulse generator for large-scale superconducting quantum computing
a Circuit diagram for the readout of qubit state with the cryogenic pulse generator (blue). The qubit sample (orange) is implemented with a 3D circuit quantum electrodynamics architecture containing a transmon qubit that is dispersively coupled to a microwave resonator for state readout. The conventional readout signal is synthesized with room-temperature electronics as introduced in “Methods” section and Supplementary Fig. 6. A coplanar waveguide (green) is used to connect both the cryogenic pulse generator and the conventional readout signal to the qubit sample. b Qubit-state-dependent reflection spectra of the readout resonator measured with both the conventional method and the pre-calibrated microwave pulses from the cryogenic signal source. c Rabi oscillation of the transmon qubit measured with the conventional method (shadow) and the cryogenic pulse generator (scattered plots). d Histograms of the resonator response measured the conventional method (shadow) and the cryogenic pulse generator (scattered plots), with the qubit prepared in \(\left\vert g\right\rangle\) and \(\left\vert e\right\rangle\). The inset shows a typical distribution in the I-Q quadrature plane measured with the cryogenic pulse generator.
