We present a novel readout scheme for phase qubits which eliminates the read-out SQUID so that the entire qubit and measurement circuitry only requires a single Josephson junction. Our scheme capacitively couples the phase qubit directly to a transmission line and detects its state after the measurement pulse by determining a frequency shift observable in the forward scattering parameter of the readout microwaves. This readout is extendable to multiple phase qubits coupled to a common readout line and can in principle be used for other flux biased qubits having two quasi-stable readout configurations.
@article{arxiv.1001.1453,
title = {Readout for Phase Qubits without Josephson Junctions},
author = {Matthias Steffen and Shwetank Kumar and David DiVincenzo and George Keefe and Mark Ketchen and Mary Beth Rothwell and Jim Rozen},
journal= {arXiv preprint arXiv:1001.1453},
year = {2015}
}