Toward Optimal Quantum Ranging: Hypothesis Testing for an Unknown Return Signal
Lior Cohen, Mark M. Wilde · Physical Review Applied · 2022
$Q\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}m$ $s\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}g$ aims to improve detector performance by utilizing quantum mechanics, but how much difference will that actually make? Here the authors show that the conventional limits given by quantum information theory are not achievable for a laser-ranging setup, since the receiver does not have complete information about the detected state $a$ $p\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i$. They present refined limits and a detection scheme to saturate these limits, which still demonstrate quantum improvement. This work strengthens the connection between quantum information theory and quantum sensing, and will promote the development of sensors that achieve the maximum improvement allowed by quantum mechanics.