Realization of high-speed adaptive quantum state estimation (Conference Presentation)
Saki Nohara, Ryo Okamoto, Koichi Yamagata +2 more
Accurate estimation of unknown quantum states using limited number of samples is very important but difficult task using fixed measurement basis states since the best local unbiased estimator (LUE) for estimating the parameter depends, in general, on the unknown parameter itself. In order to solve this problem, Nagaoka advocated an adaptive quantum state estimation (AQSE) procedure. Later, Fujiwara proved the strong consistency and asymptotic efficiency for AQSE. AQSE has been demonstrated by us for the linear polarizations of photons, and recently for a single polarization qubit. However, in order to apply AQSE to actual measurement including application to life science, we need to improve the speed of the system which is limited by the response time of the mechanical rotation stage used in the previous experiment [Phys. Rev. Lett. 109, 130404 (2012)]. To solve this problem, we realized high-speed AQSE experiment using liquid crystal retarder (LCR). We demonstrate the adaptive quantum state estimation using a LCR instead of a half wave plate on a mechanical rotator in previous research. We realized a substantial speed-up of estimation time, keeping the accuracy of estimation at the same level. In fact, it took 0.40 second per photon in the previous study, whereas 0.073 second per photon in the present. Specifically, the time to determine the polarization measurement basis was greatly decreased, from 0.34 second per photon in the previous study to 0.010 second per photon in the present.
Quantum Communications and Quantum Imaging•Nov 6, 2018•0 citations