Progress in superconducting qubit experiments with greater numbers of qubits or advanced techniques such as feedback requires faster and more accurate state measurement. We have designed a multiplexed measurement system with a bandpass filter that allows fast measurement without increasing environmental damping of the qubits. We use this to demonstrate simultaneous measurement of four qubits on a single superconducting integrated circuit, the fastest of which can be measured to 99.8% accuracy in 140ns. This accuracy and speed is suitable for advanced multi-qubit experiments including surface code error correction.
@article{arxiv.1401.0257,
title = {Fast Scalable State Measurement with Superconducting Qubits},
author = {Daniel Sank and Evan Jeffrey and J. Y. Mutus and T. C. White and J. Kelly and R. Barends and Y. Chen and Z. Chen and B. Chiaro and A. Dunsworth and A. Megrant and P. J. J. O'Malley and C. Neill and P. Roushan and A. Vainsencher and J. Wenner and A. N. Cleland and J. M. Martinis},
journal= {arXiv preprint arXiv:1401.0257},
year = {2014}
}