We demonstrate initialization by joint measurement of two transmon qubits in 3D circuit quantum electrodynamics. Homodyne detection of cavity transmission is enhanced by Josephson parametric amplification to discriminate the two-qubit ground state from single-qubit excitations non-destructively and with 98.1% fidelity. Measurement and postselection of a steady-state mixture with 4.7% residual excitation per qubit achieve 98.8% fidelity to the ground state, thus outperforming passive initialization.
@article{arxiv.1204.2479,
title = {Initialization by measurement of a two-qubit superconducting circuit},
author = {D. Ristè and J. G. van Leeuwen and H. -S. Ku and K. W. Lehnert and L. DiCarlo},
journal= {arXiv preprint arXiv:1204.2479},
year = {2012}
}
Comments
5 pages, 4 figures, and Supplementary Information (7 figures, 1 table)