We address the ultimate charge detection scheme with a quantum point contact. It is shown that a superposed input state is necessary to exploit the full sensitivity of a quantum point contact detector. The coherence of the input state provides an improvement in charge sensitivity, and this improvement is a result of the fundamental property of the scattering matrix. Further, a quantum-limited (maximally efficient) detection is possible by controlling the interference between the two output waves. Our scheme provides the ultimate sensitivity and efficiency of charge detection with a generic quantum point contact.
@article{arxiv.1208.0818,
title = {Ultimate charge sensitivity and efficiency of a quantum point contact with a superposed input state},
author = {Kang-Ho Lee and Kicheon Kang},
journal= {arXiv preprint arXiv:1208.0818},
year = {2015}
}