We present a scheme for tuning two quantum point contacts as a quantum-limited charge detector. Based on the scattering matrix approach, we analyze a general condition of quantum-limited detection with a single-channel quantum detector possessing time-reversal symmetry. From this analysis we find that quantum-limited detection can be easily realized with two quantum point contacts connected in series, which is not possible if only a single quantum point contact is used. We also discuss the sensitivity enhancement due to multiple reflections of the two point contacts.
@article{arxiv.1101.4784,
title = {Quantum-limited charge detection with two quantum point contacts},
author = {Kang-Ho Lee and Kicheon Kang},
journal= {arXiv preprint arXiv:1101.4784},
year = {2012}
}