Implementing dispersive readout of superconducting qubits with simultaneous resonator reset

A key challenge in quantum computing is speeding up measurement and initialization. Here, we experimentally demonstrate a dispersive measurement method for superconducting qubits that simultaneously returns the readout resonator to its initial state. The approach is based on analytical pulses [1] and requires knowledge of the qubit and resonator parameters, but needs no direct optimization of the pulse shape. Moreover, the method generalizes to an arbitrary number of modes. In the case of qubit readout, we are able to drive the resonator to 10² and back to 10^-2 photons in less than 4/κ, achieving a T₁-limited assignment fidelity of 98.5%. We also present results for qutrit readout. 

[1] F. Motzoi, L. Buchmann, C. Dickel: Simple, smooth and fast pulses for dispersive measurements in cavities and quantum networks, arXiv:1809.04116v1 [quant-ph]